CN107370187A - A kind of photovoltaic microgrid system and photovoltaic microgrid system control method - Google Patents
A kind of photovoltaic microgrid system and photovoltaic microgrid system control method Download PDFInfo
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Abstract
The present invention provides a kind of photovoltaic microgrid system and photovoltaic microgrid system control method.Wherein, photovoltaic microgrid system includes：Multiple stage type photovoltaic generation subsystems in parallel；Any stage type photovoltaic generation subsystem includes：Multiple power optimization devices, multiple power optimization device control units, concentrate inverter and concentrate inverter control unit.Wherein, photovoltaic microgrid system control method includes：For any photovoltaic generation subsystem, the active power and reactive power for concentrating inverter output are obtained；Obtain the available maximum active power for concentrating inverter and can use maximum reactive power；Obtain reference voltage；Generate the control signal of the concentration inverter.A kind of photovoltaic microgrid system and photovoltaic microgrid system control method provided by the invention, realize coordination control of multiple photovoltaic generation subsystems under without communication condition, the autonomous of proof load power, reasonable distribution and the stabilization of photovoltaic microgrid system voltage and frequency.
Description
Technical Field
The invention relates to the technical field of photovoltaic power generation, in particular to a photovoltaic micro-grid system and a control method of the photovoltaic micro-grid system.
Background
The photovoltaic power generation has the advantages of less environmental pollution, flexible installation place, high energy utilization rate and the like, and is one of the important development trends of the current distributed power generation. The photovoltaic microgrid is used as an effective carrier for integrating distributed photovoltaic power supplies, photovoltaic power generation systems in different areas can be coordinated, random uncertainty and regional dependence of partial photovoltaic power generation are overcome to a certain extent, and the overall stable power supply capacity and power supply electric energy quality of the system are improved. When the photovoltaic microgrid operates in an off-grid mode, the photovoltaic power generation system has certain random fluctuation, and the voltage and the frequency of the photovoltaic microgrid system are difficult to keep stable.
The photovoltaic power generation system of the photovoltaic microgrid mainly comprises a single-stage photovoltaic power generation system and a double-stage photovoltaic power generation system. A two-stage photovoltaic power generation system mainly comprises a photovoltaic panel assembly, a DC/DC converter and a centralized inverter. Through the coordination control of the centralized inverters of all the two-stage photovoltaic power generation systems, when the photovoltaic microgrid system operates in an off-grid mode, the voltage and the frequency of the photovoltaic microgrid system can be stabilized. The existing coordination control on the centralized inverter is based on communication among two-stage photovoltaic power generation systems, system voltage or frequency is adjusted by coordinating power balance among the two-stage photovoltaic power generation systems, high communication bandwidth is needed, and the existing coordination control on the centralized inverter does not have plug-and-play characteristics and high reliability.
Disclosure of Invention
The invention provides a photovoltaic micro-grid system and a photovoltaic micro-grid system control method, aiming at overcoming the defect that a plurality of photovoltaic power generation subsystems of the existing photovoltaic micro-grid system need higher communication bandwidth for coordinated control.
According to one aspect of the invention, there is provided a photovoltaic microgrid system comprising: a plurality of two-stage photovoltaic power generation subsystems connected in parallel; any of the two-stage photovoltaic power generation subsystems, comprising: the system comprises a plurality of power optimizers, a plurality of power optimizer control units, a centralized inverter and a centralized inverter control unit; the plurality of power optimizers are connected in series; the output end of the plurality of power optimizers connected in series is connected with the input end of the centralized inverter; each power optimizer corresponds to one power optimizer control unit; the power optimizer control unit is used for switching into two different working modes according to the output voltage of the power optimizer and performing hysteresis control on the power optimizer; the centralized inverter control unit is used for controlling the output power of the centralized inverter according to the available maximum active power of the centralized inverter, so that the difference between the available maximum active power and the output power of the centralized inverter of each two-stage photovoltaic power generation subsystem is equal.
Preferably, the centralized inverter control unit includes: the device comprises a power calculation module, a power outer ring control module, an available maximum power dynamic estimation module, a voltage and current control module and a PWM (pulse width modulation) module; the power calculation module is used for acquiring the active power P output by the centralized inverter according to the output voltage and the output current of the centralized inverter0And reactive power Q0(ii) a The available maximum power dynamic estimation module is used for acquiring the available maximum active power of the centralized inverter according to the input current and the input voltage of the centralized inverterAnd maximum available reactive powerThe power outer ring control module is used for transmitting power according to the centralized inverterActive power P output0Reactive power Q0Available maximum active powerAnd maximum available reactive powerObtaining a reference voltage Vrsinωrt; the voltage current control module is used for controlling the current according to the reference voltage Vrsinωrt, generating a voltage reference signal in the centralized inverter; and the PWM modulation module is used for modulating the voltage reference signal in the centralized inverter and generating a control signal of the centralized inverter.
Preferably, the active power P output by the centralized inverter and obtained by the power calculation module0And reactive power Q0Are respectively as
Wherein, VoacTo concentrate the output voltage of the inverter, IoacFor concentrating the output current of the inverter, Vo'acIs a VoacThe voltage lagging by 90 degrees, τ, is the low pass filter constant.
Preferably, the maximum active power available for the centralized inverter obtained by the maximum power dynamic estimation moduleAnd maximum available reactive powerRespectively as follows:
when the input voltage V of the concentrated inverter is higher than the reference voltage VbusBelow Vbus,minWhen, the available maximum active power of the concentrated inverterAnd maximum available reactive powerAre respectively as
Wherein,in order to concentrate the maximum available active power of the inverter,to concentrate the maximum available reactive power, P, of the inverterrealtimeFor concentrating the real-time power of the inverter, SmaxFor concentrating the maximum value of the apparent capacity of the inverter, Vbus,minFor concentrating the minimum output voltage allowed by the inverter, ibusFor concentrating the input current of the inverter, VbusIs the input voltage of the concentrated inverter;
when the input voltage V of the concentrated inverter is higher than the reference voltage VbusHigher than Vbus,maxThe maximum active power available from the central inverterAnd maximum available reactive powerAre respectively as
Wherein,to concentrate the maximum active power available to the inverter at the kth beat,for the (k +1) th beat the maximum active power available for the inverter is concentrated,centralizing the available maximum reactive power of the inverter for the (k +1) th beat, SmaxFor concentrating the maximum value of the apparent capacity of the inverter, Vbus,maxTo concentrate the maximum output voltage allowed by the inverter.
Preferably, ω in the reference voltage acquired by the power outer loop control modulerAnd VrAre respectively as
Wherein, ω isr、VrReference values of angular frequency and amplitude, omega, respectively, for the output voltage of the central inverter*、V*The angular frequency and the amplitude of the output voltage of the centralized inverter in a rated state are respectively shown, m and n are respectively the droop coefficients of active-angular frequency droop (P-omega) and reactive-voltage droop (Q-V) of the centralized inverter,respectively the maximum active power available and the maximum reactive power available, V, of the central inverterbus、Respectively being the input of a central inverterVoltage and its nominal reference value, k is the regulation factor.
Preferably, the reference value is rated according to the input voltage of the concentrated inverterDetermining a minimum output voltage allowed by the centralized inverter and a maximum output voltage allowed by the centralized inverter.
Preferably, the power optimizer control unit switches to two different operation modes according to the output voltage of the power optimizer, and further includes:
when the output voltage V of the power optimizerdcBelow Vdc,minWhen the power optimizer control unit is switched to a maximum power tracking working mode; wherein, Vdc,minThe minimum output voltage allowed for the power optimizer;
when the output voltage V of the power optimizerdcHigher than Vdc,maxWhen the power optimizer control unit is switched to a direct-through working mode; wherein, Vdc,maxThe maximum output voltage allowed by the power optimizer.
Preferably, the reference value is based on the output voltage of the power optimizerDetermining the minimum output voltage V allowed by the power optimizerdc,minAnd the maximum output voltage V allowed by the power optimizerdc,max；
Output voltage reference value of the power optimizerIs composed of
Wherein,and n is the total number of the power optimizers in the two-stage off-grid photovoltaic power generation subsystem.
According to another aspect of the invention, a photovoltaic microgrid system control method is provided and comprises the following steps: for any one of the photovoltaic power generation sub-systems,
s1, according to the output voltage V of the centralized inverteroacAnd an output current IoacObtaining the active power P output by the centralized inverteroAnd reactive power Qo；
S2, according to the input current i of the centralized inverterbusAnd an input voltage VbusObtaining the maximum active power available for the centralized inverterAnd maximum available reactive power
S3, according to the active power P of the centralized inverteroReactive power QoAvailable maximum active powerAnd maximum available reactive powerObtaining a reference voltage Vrsinωrt；
S4, according to the reference voltage VrsinωrAnd t, generating a control signal of the centralized inverter.
Preferably, the step S4 further includes:
s41, according to the ginsengReference voltage Vrsinωrt, generating a voltage reference signal in the centralized inverter;
and S42, modulating the voltage reference signal in the centralized inverter and generating a control signal of the centralized inverter.
According to the photovoltaic micro-grid system and the photovoltaic micro-grid system control method, coordinated control of a plurality of photovoltaic power generation subsystems under a communication-free condition is achieved, and autonomous and reasonable distribution of load power and stability of voltage and frequency of the photovoltaic micro-grid system are guaranteed.
Drawings
Fig. 1 is a schematic structural diagram of a photovoltaic microgrid system according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of a centralized inverter control unit in a photovoltaic microgrid system according to an embodiment of the present invention;
FIG. 3 is a schematic diagram illustrating a control principle of a power optimizer control unit in the photovoltaic microgrid system according to an embodiment of the present invention;
fig. 4 is a flowchart of a control method of a photovoltaic microgrid system according to an embodiment of the present invention.
Detailed Description
The following detailed description of embodiments of the present invention is provided in connection with the accompanying drawings and examples. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.
Fig. 1 is a schematic structural diagram of a photovoltaic microgrid system according to an embodiment of the present invention. As shown in fig. 1, a photovoltaic microgrid system comprises: a plurality of two-stage photovoltaic power generation subsystems connected in parallel; any two-stage photovoltaic power generation subsystem, comprising: the system comprises a plurality of power optimizers, a plurality of power optimizer control units, a centralized inverter and a centralized inverter control unit; a plurality of power optimizers are connected in series; the output end of the plurality of power optimizers connected in series is connected with the input end of the centralized inverter; each power optimizer corresponds to one power optimizer control unit; the power optimizer control unit is used for switching into two different working modes according to the output voltage of the power optimizer and performing hysteresis control on the power optimizer; and the centralized inverter control unit is used for controlling the output power of the centralized inverter according to the available maximum active power of the centralized inverter so as to enable the difference between the available maximum active power and the output power of the centralized inverter of each two-stage photovoltaic power generation subsystem to be equal.
The photovoltaic microgrid system comprises a plurality of two-stage photovoltaic power generation subsystems. Wherein the plurality is at least two. Referring to fig. 1, a photovoltaic microgrid system includes M two-stage photovoltaic power generation subsystems. Wherein M is more than or equal to 2. M two-stage photovoltaic power generation subsystems are connected in parallel and are all connected to a common bus. And the common bus is also connected with an area equivalent load.
The structure of each two-stage photovoltaic power generation subsystem is described below by taking the 1 st two-stage photovoltaic power generation subsystem as an example. The structures of other two-stage photovoltaic power generation subsystems, namely the structures of the 2 nd to M th two-stage photovoltaic power generation subsystems, are the same as the structure of the 1 st two-stage photovoltaic power generation subsystem, and are not repeated here.
The 1 st two-stage photovoltaic power generation subsystem includes: the system comprises a plurality of power optimizers, a plurality of power optimizer control units, a centralized inverter and a centralized inverter control unit.
The front stage of the 1 st two-stage photovoltaic power generation subsystem is a plurality of power optimizers. The number of the power optimizers in the 1 st two-stage photovoltaic power generation subsystem is n, wherein n is larger than or equal to 2. The n power optimizers are Boost type direct current/direct current (Boost type DC/DC) power optimizers.
The input end of each power optimizer is connected with the output end of the photovoltaic panel assembly through the input end of the power optimizer in a capacitance mode. Each power optimizer controls the photovoltaic panel assembly to which it is connected.
The output of each power optimizer also includes an output capacitance.
The output ends of the n power optimizers are connected in series, and the boosting capacity of the front stage can be improved.
Each power optimizer corresponds to a power optimizer control unit. Each power optimizer control unit controls the power optimizer connected to it. And the power optimizer control unit is switched into two different working modes according to the output voltage of the power optimizer, generates a control signal of the power optimizer, controls the duty ratio of a semiconductor switch of the power optimizer and realizes hysteresis control of the power optimizer.
The front stage of the 1 st two-stage photovoltaic power generation subsystem is a concentrated inverter. The input end of the centralized inverter is connected with the output end of the n power optimizers after being connected in series through the direct current bus capacitor, and the decoupling function of a certain degree is achieved through the direct current bus capacitor.
The output side of the concentrated inverter is connected with a public bus of the photovoltaic microgrid through a line impedance 1.
The concentrating inverter is a DC/AC inverter. In order to achieve better capability of direct current/alternating current (DC/AC) power conversion, the centralized inverter may employ a typical single-phase full-bridge voltage type inverter, but is not limited thereto.
And the centralized inverter control unit is used for controlling the output power of the centralized inverter according to the available maximum active power of the centralized inverter. And controlling the output power of the concentrated inverter by each concentrated inverter control unit according to the available maximum active power of the concentrated inverter, so that the difference between the available maximum active power and the output power of the concentrated inverter of each two-stage photovoltaic power generation subsystem is equal.
According to the embodiment of the invention, each centralized inverter control unit controls the output power of the centralized inverter according to the available maximum active power of the centralized inverter, so that the coordinated control of a plurality of photovoltaic power generation subsystems under the condition of no communication is realized, the autonomous and reasonable distribution of load power and the stability of the voltage and frequency of the photovoltaic micro-grid system are ensured, and the plug-and-play performance and the higher reliability are realized. Furthermore, the photovoltaic microgrid system provided by the embodiment of the invention is particularly suitable for a high-permeability photovoltaic microgrid, under the condition that the total photovoltaic power generation capacity of the system is greater than the load demand, a large number of energy storage devices are not needed to stabilize the output power of the system, and the energy storage system and the auxiliary energy are not needed to be supported, so that the investment of auxiliary type schedulable energy in the photovoltaic microgrid is greatly reduced, the construction cost of the system is saved, and the waste of the energy storage devices is avoided. Furthermore, the two-stage photovoltaic power generation subsystem based on the series structure of the power optimizer realizes the boosting function of the whole voltage and higher system conversion efficiency, and has the advantages of simple structure, flexible control, high conversion efficiency, stability, reliability and the like.
Fig. 2 is a schematic structural diagram of a centralized inverter control unit in the photovoltaic microgrid system according to an embodiment of the present invention. Based on the above-described embodiment, as shown in fig. 2, the concentrated inverter control unit includes: the device comprises a power calculation module, a power outer ring control module, an available maximum power dynamic estimation module, a voltage current control module and a PWM (pulse width modulation) module.
A power calculation module for obtaining the active power P output by the centralized inverter according to the output voltage and output current of the centralized inverter0And reactive power Q0。
The available maximum power dynamic estimation module is used for acquiring the available maximum active power of the centralized inverter according to the input current and the input voltage of the centralized inverterAnd maximum available reactive power
Power outer loop control moduleFor deriving active power P from the output of the central inverter0Reactive power Q0Available maximum active powerAnd maximum available reactive powerObtaining a reference voltage Vrsinωrt。
A voltage current control module for controlling the current according to a reference voltage VrsinωrAnd t, generating a voltage reference signal in the centralized inverter.
And the PWM module is used for modulating the voltage reference signal in the centralized inverter and generating a control signal of the centralized inverter.
Specifically, the power calculation module calculates the output voltage V according to the centralized inverteroacAnd an output current IoacObtaining the active power P output by the centralized inverter0And reactive power Q0. Output voltage V of centralized inverteroacAnd an output current IoacAnd can be obtained by voltage detection and current detection methods which are conventional in the art. For example, the output voltage V of the concentrated inverter may be obtained by a voltage transformeroacObtaining the output current I of the centralized inverter through the current transformeroacBut is not limited thereto.
A power calculation module for calculating the obtained active power P0And reactive power Q0And sending the data to a power outer loop control module.
The maximum power available includes the maximum active power available and the maximum reactive power available.
The maximum power dynamic estimation module can be used for estimating the input current i of the centralized inverterbusAnd an input voltage VbusObtaining the maximum active power available for the centralized inverterAnd maximum available reactive power
The available maximum power dynamic estimation module acquires the available maximum active power of the centralized inverterAnd maximum available reactive powerAnd sending the data to a power outer loop control module.
A power outer loop control module for receiving and concentrating the active power P output by the inverter sent by the power calculation module0And reactive power Q0And the maximum active power available from the centralized inverter sent by the maximum power dynamic estimation moduleAnd maximum available reactive powerPerforming power outer loop control on the centralized inverter and generating a reference voltage Vrsinωrt。
Active power P output by centralized inverter0And reactive power Q0And concentrating the maximum active power available for the inverterAnd maximum available reactive powerIs the basis for controlling the centralized inverter. The control of the concentrated inverter of each two-stage photovoltaic power generation subsystem enables the available maximum active power and output power of the concentrated inverter of each two-stage photovoltaic power generation subsystemThe difference is equal.
A power outer loop control module for converting the reference voltage Vrsinωrt is sent to the voltage current control module.
A voltage current control module for receiving the reference voltage V generated by the power outer loop control modulersinωrAnd t, carrying out double closed loop tracking control on the output capacitor voltage and the inductive current of the inverter to generate a voltage reference signal in the centralized inverter.
And the voltage current control module is used for sending the voltage reference signal in the centralized inverter to the PWM module.
And a PWM modulation module that performs PWM (Pulse-width modulation) on the voltage reference signal in the central inverter generated by the voltage/current control module, generates a control signal for the central inverter, and controls a duty ratio of semiconductor switches of the central inverter.
According to the embodiment of the invention, the output power of the centralized inverter is controlled by the centralized inverter control unit according to the available maximum power of the centralized inverter, so that the coordination control of a plurality of photovoltaic power generation subsystems under the condition of no communication is realized, the reasonable distribution of load power and the stability of the voltage and frequency of the photovoltaic micro-grid system are ensured, and the plug-and-play performance and the higher reliability are realized.
Based on the embodiment, the power calculation module acquires the active power P output by the centralized inverter0And reactive power Q0Are respectively as
Wherein, VoacTo concentrate the output voltage of the inverter, IoacFor concentrating the output current of the inverter, Vo'acIs a VoacThe voltage lagging by 90 degrees, τ, is the low pass filter constant.
Available maximum active power of centralized inverter obtained by available maximum power dynamic estimation moduleAnd maximum available reactive powerRespectively as follows:
when concentrating the input voltage V of the inverterbusBelow Vbus,minThe maximum active power available from the central inverterAnd maximum available reactive powerAre respectively as
Wherein,in order to concentrate the maximum available active power of the inverter,to concentrate the maximum available reactive power, P, of the inverterrealtimeFor concentrating the real-time power of the inverter, SmaxFor concentrating the maximum value of the apparent capacity of the inverter, Vbus,minFor concentrating the minimum output voltage allowed by the inverter, ibusFor concentrating the input current of the inverter, VbusIs the input voltage of the concentrated inverter;
when concentrating the input voltage V of the inverterbusHigher than Vbus,maxThe maximum active power available from the central inverterAnd maximum available reactive powerAre respectively as
Wherein,to concentrate the maximum active power available to the inverter at the kth beat,for the (k +1) th beat the maximum active power available for the inverter is concentrated,centralizing the available maximum reactive power of the inverter for the (k +1) th beat, SmaxFor concentrating the maximum value of the apparent capacity of the inverter, Vbus,maxTo concentrate the maximum output voltage allowed by the inverter.
Omega in the reference voltage acquired by the power outer loop control modulerAnd VrAre respectively as
Wherein, ω isr、VrRespectively the angular frequency and amplitude reference values of the concentrated inverter output voltage,ω*、V*the angular frequency and the amplitude of the output voltage of the centralized inverter in a rated state are respectively shown, m and n are respectively the droop coefficients of active-angular frequency droop (P-omega) and reactive-voltage droop (Q-V) of the centralized inverter,respectively the maximum active power available and the maximum reactive power available, V, of the central inverterbus、The input voltage of the concentrated inverter and the rated reference value thereof are respectively, and k is a regulating coefficient.
According to the input voltage rated reference value of the centralized inverterThe minimum output voltage allowed by the concentrated inverter and the maximum output voltage allowed by the concentrated inverter are determined.
In particular, the power calculation module calculates the output voltage V of the inverter according to the concentrationoacAnd an output current IoacDetermining the active power P output by the central inverteroAnd reactive power Qo. Active power P output by centralized inverteroAnd reactive power QoEach can be calculated by the following formula:
wherein, VoacTo concentrate the output voltage of the inverter, IoacFor concentrating the output current of the inverter, Vo'acIs a VoacThe voltage lagging by 90 degrees, τ, is the low pass filter constant.
A power calculation module for obtaining active power P0And reactive power Q0Then, the active power P is obtained0And reactive power Q0Send to outside of powerAnd a ring control module.
In actual operation, the photovoltaic power generation subsystem has unstable working state. When the working state is unstable, the available maximum power of the centralized inverter can change. Therefore, the maximum power dynamic estimation module is used for acquiring the maximum power available for the centralized inverter according to the working state of the photovoltaic power generation subsystem.
The photovoltaic power generation subsystem is limited by natural environmental conditions, and the output power of the centralized inverter is limited by the input power of the centralized inverter. When the input power and the output power of the centralized inverter are matched with each other, the photovoltaic power generation subsystem stably operates; when the input power and the output power of the centralized inverter are not matched, the photovoltaic power generation subsystem is unstable in operation.
When the input power of the centralized inverter is smaller than the output power, the available maximum power of the centralized inverter is insufficient, the voltage of a direct-current bus capacitor is continuously reduced, the photovoltaic power generation subsystem is unstable in operation, and a front-stage power optimizer operates in a Maximum Power Point Tracking (MPPT) working mode. Therefore, a need exists for a reduced centralized inverter output with a maximum power available dynamic prediction module that dynamically refreshes the maximum power available to the centralized inverter.
When the input power of the centralized inverter is larger than the output power, the available maximum power of the centralized inverter is excessive, the voltage of the direct-current bus capacitor starts to rise, and the available maximum power dynamic estimation module does not need to dynamically refresh the available maximum power reference value at the moment. The output of the power optimizer at the front stage is reduced, namely the input power of the centralized inverter is reduced until the balance between the input power and the output power of the centralized inverter is achieved.
Whether the running state of the photovoltaic power generation subsystem is stable or not can be determined according to the input voltage V of the centralized inverterbusAnd (4) determining.
When concentrating the input voltage V of the inverterbusBelow Vbus,minAnd in time, the photovoltaic power generation subsystem is unstable in operation. Wherein, Vbus,minFor concentrating the minimum output voltage allowed by the inverter, VbusTo concentrate the input voltage of the inverter.
Minimum output voltage V allowed by centralized inverterbus,minAccording to the input voltage rated reference value of the centralized inverterAnd (4) determining.
Wherein k is1For concentrating the minimum output voltage coefficient, k, of the inverter1<1，k1The value of (a) is determined according to the actual condition of the photovoltaic microgrid.
Preferably, k is10.85. At this time, the process of the present invention,
when concentrating the input voltage V of the inverterbusBelow Vbus,minAnd in time, the maximum power dynamic estimation module can be used for dynamically refreshing the available maximum power of the centralized inverter. Maximum active power available for a concentrated inverterAnd maximum available reactive powerCan be obtained by the following formula:
wherein,in order to concentrate the maximum available active power of the inverter,to concentrate the maximum available reactive power, P, of the inverterrealtimeFor concentrating the real-time power of the inverter, SmaxFor concentrating the maximum value of the apparent capacity of the inverter, Vbus,minFor concentrating the minimum output voltage allowed by the inverter, ibusFor concentrating the input current of the inverter, VbusTo concentrate the input voltage of the inverter.
Input current i of the concentrated inverterbusAnd an input voltage VbusAnd can be obtained by voltage detection and current detection methods which are conventional in the art. The input voltage V of the central inverter can be obtained, for example, by means of a voltage transformerbusObtaining the input current i of the concentrated inverter through the current transformerbusBut is not limited thereto.
When concentrating the input voltage V of the inverterbusHigher than Vbus,maxAnd when the photovoltaic power generation subsystem is operated in a stable state. Wherein, Vbus,maxFor concentrating the maximum output voltage, V, allowed by the inverterbusTo concentrate the input voltage of the inverter.
Maximum output voltage V allowed by centralized inverterbus,maxAccording to the input voltage rated reference value of the centralized inverterAnd (4) determining.
Wherein k is2For concentrating the maximum output voltage coefficient, k, of the inverter2>1，k2The value of (a) is determined according to the actual condition of the photovoltaic microgrid.
Preferably, k is21.05. At this time, the process of the present invention,
when concentrating the input voltage V of the inverterbusHigher than Vbus,maxIn the method, the available maximum power of the concentrated inverter is not required to be dynamically refreshed, and the available maximum power of the concentrated inverter in the last beat is usedCaching for the next beatMaximum active power available for a concentrated inverterAnd maximum available reactive powerCan be obtained by the following formula:
wherein,to concentrate the maximum active power available to the inverter at the kth beat,for the (k +1) th beat the maximum active power available for the inverter is concentrated,centralizing the available maximum reactive power of the inverter for the (k +1) th beat, SmaxFor concentrating the maximum value of the apparent capacity of the inverter, Vbus,maxTo concentrate the maximum output voltage allowed by the inverter.
Available maximum power dynamic estimation module, and obtained available maximum active power of centralized inverterAnd maximum available reactive powerThen, the available maximum active power of the centralized inverter is obtainedAnd maximum available reactive powerAnd sending the data to a power outer loop control module.
A power outer loop control module for receiving the active power P output by the centralized inverter sent by the power calculation module0And reactive power Q0And the maximum active power available from the centralized inverter sent by the maximum power dynamic estimation moduleAnd maximum available reactive powerThen according to the active power P of the central inverteroReactive power QoAvailable maximum active powerAnd maximum available reactive powerCan control the centralized inverter to generate a reference voltage Vrsinωrt。
Reference voltage Vrsinωrω in trAnd VrCan be obtained by the following formula:
wherein, ω isr、VrReference values of angular frequency and amplitude, omega, respectively, for the output voltage of the central inverter*、V*The angular frequency and the amplitude of the output voltage of the centralized inverter in a rated state are respectively shown, m and n are respectively the droop coefficients of active-angular frequency droop (P-omega) and reactive-voltage droop (Q-V) of the centralized inverter,respectively the maximum active power available and the maximum reactive power available, V, of the central inverterbus、The input voltage of the concentrated inverter and the rated reference value thereof are respectively, and k is a regulating coefficient.
A power outer loop control module for generating a reference voltage VrsinωrAfter t, the reference voltage V is setrsinωrt is sent to the voltage current control module.
When a photovoltaic microgrid system is formed by a plurality of photovoltaic power generation subsystems connected in parallel, due to the frequency consistency of the photovoltaic microgrid system, each photovoltaic power generation subsystem can reach the same output frequency value under the steady state condition, and therefore, the control method of the photovoltaic microgrid system provided by the embodiment can control the concentrated inverter of each photovoltaic power generation subsystem, so that the purpose of controlling the concentrated inverter of each photovoltaic power generation subsystem can be achieved
Wherein,Po_ithe maximum available active power and the output power of the concentrated inverter of the ith photovoltaic power generation subsystem are respectively, i is more than or equal to 1 and less than or equal to M;Po_Mthe maximum active power and output power available for the concentrating inverter of the mth photovoltaic power generation subsystem.
The power calculation module, the power outer-loop control module and the available maximum power dynamic estimation module provided by the embodiment of the invention control the concentrated inverter based on the available maximum active power of the concentrated inverter, realize the coordinated control of a plurality of photovoltaic power generation subsystems under the condition of no communication, ensure the autonomous and reasonable distribution of load power and the stability of the voltage and frequency of the photovoltaic micro-grid system, and have plug-and-play performance and higher reliability. The subsystem with stronger photovoltaic power generation capacity at the source end outputs a higher power value, and the subsystem with weaker photovoltaic power generation capacity at the source end outputs a lower power value, so that the same power allowance is kept for all photovoltaic power generation subsystems, and better dynamic power adjustment is facilitated; and because the output power of the photovoltaic power generation subsystem is unbalanced, the service life of part of the photovoltaic power generation subsystem is shortened. Further, the power calculation module, the power outer-loop control module and the available maximum power dynamic estimation module provided by the embodiment of the invention control the concentrated inverter based on the available maximum active power of the concentrated inverter, fully considers the stable operation area and the limited capacity of the concentrated inverter, can quickly recover the working state of the photovoltaic power generation subsystem from instability to stability, and better ensures the stability of the voltage and the frequency of the photovoltaic microgrid system.
Fig. 3 is a schematic control principle diagram of a power optimizer control unit in the photovoltaic microgrid system according to an embodiment of the present invention. Based on the above embodiment, as shown in fig. 3, the power optimizer control unit switches to two different operation modes according to the output voltage of the power optimizer,further comprising: output voltage V of power optimizerdcBelow Vdc,minWhen the power optimizer is in the maximum power tracking mode, the control unit of the power optimizer is switched to the maximum power tracking working mode; wherein, Vdc,minThe minimum output voltage allowed for the power optimizer; output voltage V of power optimizerdcHigher than Vdc,maxWhen the power optimizer control unit is switched to a direct-through working mode; wherein, Vdc,maxThe maximum output voltage allowed by the power optimizer.
Specifically, since the output characteristics of the photovoltaic panel assembly affect the output characteristics of the power optimizer, when a portion of the photovoltaic panel assembly is shielded, the operation state of the photovoltaic panel assembly is unstable, thereby causing the operation state of the power optimizer to be unstable.
When the operating point of the power optimizer is located at the left half of its P-U output characteristic curve, i.e. theThe running state of the power optimizer is unstable; when the operating point of the power optimizer is located in the right half of its P-U output characteristic curve, i.e. theAnd when the power optimizer is in the normal operation state, the operation state of the power optimizer is stable. Therefore, it is necessary to ensure that the operating point of the power optimizer is stable in the right half, that is, when a large disturbance occurs, the operating point of the power optimizer is located in the left half of the P-U output characteristic curve of the power optimizer, and the operating point of the power optimizer returns to the right half from the left half of the P-U output characteristic curve of the power optimizer through the control of the power optimizer control unit.
And correspondingly switching the control unit of the power optimizer between two different working modes according to whether the working state of the power optimizer is stable or not.
When the running state of the power optimizer is stable, the control unit of the power optimizer is switched to a direct-current working mode, so that the power optimizer continues to run in a stable state.
When the operation state of the power optimizer is unstable, the control unit of the power optimizer is switched to a maximum power tracking working mode to control the output of the power optimizer, so that the power optimizer returns to a stable operation state from the unstable operation state.
Output voltage V of power optimizerdcBelow Vdc,minWhen the power optimizer is in the maximum power tracking mode, the control unit of the power optimizer is switched to the maximum power tracking working mode; wherein, Vdc,minThe minimum output voltage allowed for the power optimizer;
output voltage V of power optimizerdcHigher than Vdc,maxWhen the power optimizer control unit is switched to a direct-through working mode; wherein, Vdc,maxThe maximum output voltage allowed by the power optimizer.
Specifically, whether the operation state of the power optimizer is stable or not is judged by the output voltage of the power optimizer. The steady state signal of the power optimizer may be set to 1 and the unstable state signal to-1.
Output voltage V of power optimizerdcBelow Vdc,minWhen the power optimizer is in an unstable operation state; output voltage V of power optimizerdcHigher than Vdc,maxAnd when the power optimizer is in the unstable operation state, the power optimizer returns to the stable operation state. Wherein, Vdc,minFor the minimum output voltage, V, allowed by the power optimizerdc,maxThe maximum output voltage allowed by the power optimizer.
Output voltage V of power optimizerdcReduced to below Vdc,minIn the meantime, the power optimizer is in an unstable operation state, and the operation working point of the power optimizer is located at the left half section of the P-U output characteristic curve of the power optimizer. The power optimizer control unit operates in a Maximum Power Point Tracking (MPPT) working mode, generates a control signal of the power optimizer, controls hysteresis loop of output side capacitance of the power optimizer by controlling duty ratio of a semiconductor switching tube of the power optimizer, and controls power optimizationThe output of the device. The specific control process comprises the following steps: the capacitor on the output side of the power optimizer is charged quickly, the output voltage of the power optimizer is increased gradually, the operation working point of the power optimizer is separated from the unstable state of the left half section of the P-U output characteristic curve gradually, and the power optimizer returns to the stable state of the right half section of the P-U output characteristic curve. Output voltage V of power optimizerdcIncrease to above Vdc,maxAnd when the power optimizer is in the unstable operation state, the power optimizer returns to the stable operation state.
When the running state of the power optimizer is stable, the running working point of the power optimizer is located on the right half section of the P-U output characteristic curve, the power optimizer control unit runs in a direct-connection working mode to control the power optimizer, the duty ratio of a semiconductor switch tube of the power optimizer is 0 at the moment, and the output characteristic of the photovoltaic panel assembly is the output characteristic of the power optimizer.
Referring to fig. 3, for the nth power optimizer control unit, the output voltage V according to the nth power optimizerdcnAnd switching to two different working modes to generate corresponding control signals. When the nth power optimizer control unit operates in the maximum power tracking operation mode, the output voltage V of the photovoltaic panel assembly connected with the nth power optimizer is determined according to the input voltage and the input current of the nth power optimizerpvnAnd an output current ipvnGenerating a control signal of the nth power optimizer; and when the nth power optimizer control unit operates in a direct-through working mode, generating a control signal of the nth power optimizer, wherein the duty ratio of a semiconductor switching tube of the nth power optimizer is 0.
According to the embodiment of the invention, the working modes are switched through the power optimizer control unit to stabilize the running state of the corresponding power optimizer, the dynamic response and stable running area of the photovoltaic panel assembly are fully considered, the autonomous power distribution among the power optimizers connected in series when part of the photovoltaic panel assembly is shielded is realized, the effectiveness and the feasibility are realized in practical engineering application, and the shortening of the service life of the photovoltaic panel assembly or the power optimizer caused by the imbalance of the output power of a plurality of photovoltaic panel assemblies or the power optimizers is avoided.
Based on the above embodiment, the minimum output voltage V allowed by the power optimizerdc,minAnd the maximum output voltage V allowed by the power optimizerdc,maxAccording to the output voltage reference value of the power optimizerDetermining;
output voltage reference value of power optimizerIs composed of
Wherein,and n is the total number of the power optimizers in the two-stage off-grid photovoltaic power generation subsystem.
In particular, the minimum output voltage V allowed by the power optimizerdc,minAnd the maximum output voltage V allowed by the power optimizerdc,maxAre all based on the output voltage reference value V of the power optimizer* dcAnd (4) determining.
Output voltage reference value of power optimizerAccording to the input voltage rated reference value of the centralized inverterAnd determining the total number n of power optimizers in the two-stage off-grid photovoltaic power generation subsystem. Input voltage nominal reference value of concentrated inverterNamely the rated reference value of the output voltage after the n power optimizers are connected in series. Therefore, the rated reference value of the output voltage after the n power optimizers are connected in series can be evenly distributed to each power optimizer. Output voltage reference value of power optimizerIs composed of
Minimum output voltage V allowed by power optimizerdc,minReference value of output voltage from power optimizerAnd (4) determining.
Wherein k is3For the power optimizer minimum output voltage coefficient, k3<1，k3The value of (a) is determined according to the actual condition of the photovoltaic microgrid.
Preferably, k is30.9. At this time, the process of the present invention,
maximum output voltage V allowed by power optimizerdc,minReference value of output voltage from power optimizerAnd (4) determining.
Wherein k is4For the maximum output voltage coefficient, k, of the power optimizer4>1，k4According to the actual photovoltaic microgrid conditionAnd (4) determining.
Preferably, k is41.1. At this time, the process of the present invention,
according to the embodiment of the invention, the minimum output voltage allowed by the power optimizer and the maximum output voltage allowed by the power optimizer are determined through the output voltage reference value of the power optimizer, whether the working state of the power optimizer is stable or not can be conveniently and accurately determined, the working mode of the power optimizer is timely switched, and the reasonable distribution of load power and the stability of the voltage and the frequency of the photovoltaic microgrid system are quickly realized.
Fig. 4 is a flowchart of a control method of a photovoltaic microgrid system according to an embodiment of the present invention. As shown in fig. 4, a method for controlling a photovoltaic microgrid system includes: for any photovoltaic power generation subsystem, S1, according to the output voltage V of the centralized inverteroacAnd an output current IoacObtaining the active power P output by the centralized inverteroAnd reactive power Qo(ii) a S2, according to the input current i of the concentrated inverterbusAnd an input voltage VbusObtaining the maximum active power available for the centralized inverterAnd maximum available reactive powerS3, according to the active power P of the centralized inverteroReactive power QoAvailable maximum active powerAnd maximum available reactive powerObtaining a reference voltage Vrsinωrt; s4, according to the reference voltage Vrsinωrt, generating control signals for the central inverter。
Step S4 further includes: s41, according to the reference voltage Vrsinωrt, generating a voltage reference signal in the centralized inverter; and S42, modulating the voltage reference signal in the centralized inverter and generating a control signal of the centralized inverter.
Specifically, the step S1, the step S2, and the step S3 may be implemented by the power calculation module, the available maximum power dynamic estimation module, and the power outer loop control module in the above embodiment of the photovoltaic microgrid system, respectively. Step S1 is to obtain the active power P output by the central inverteroAnd reactive power QoStep S2, the available maximum active power of the centralized inverter is obtainedAnd maximum available reactive powerAnd obtaining the reference voltage V in step S3rsinωrthe specific process of t is described in detail in the embodiment of the photovoltaic microgrid system, and is not described herein again.
Step S4, according to the reference voltage VrsinωrAnd t, generating a control signal of the centralized inverter.
According to a reference voltage VrsinωrAnd t, generating a control signal of the centralized inverter, and performing double closed loop tracking control on the output capacitor voltage and the inductive current of the centralized inverter by controlling the duty ratio of semiconductor switches of the centralized inverter so as to control the output power of the centralized inverter. For a typical single-phase full-bridge voltage-type inverter, the output power of the concentrated inverter is controlled by generating control signals for the concentrated inverter to control the duty cycles of the four semiconductor switches of the concentrated inverter.
In step S41 of step S4, the reference voltage V is usedrsinωrt, performing double closed loop tracking control on the output capacitor voltage and the inductive current of the centralized inverter to generate a centralized setAnd (4) a voltage reference signal in the middle inverter.
In step S42 of step S4, the intra-concentrated-inverter voltage reference signal is modulated to generate a control signal for the concentrated inverter. For the modulation of the voltage reference signal in the central inverter, PWM modulation is generally used.
According to the photovoltaic microgrid system control method provided by the embodiment of the invention, when a plurality of photovoltaic power generation subsystems connected in parallel form a photovoltaic microgrid system, due to the frequency consistency of the photovoltaic microgrid system, each photovoltaic power generation subsystem reaches the same output frequency value under the steady state condition, so that the control of the concentrated inverter of each photovoltaic power generation subsystem by the photovoltaic microgrid system control method provided by the embodiment can be realized
Wherein,Po_iestimating and outputting the maximum available active power of a concentrated inverter of the ith photovoltaic power generation subsystem, wherein i is more than or equal to 1 and less than or equal to M;Po Mthe maximum active power and output power available for the concentrating inverter of the mth photovoltaic power generation subsystem.
The embodiment of the invention realizes the coordination control of a plurality of photovoltaic power generation subsystems under the condition of no communication through a control method of available maximum power based on a centralized inverter, ensures the autonomous and reasonable distribution of load power and the stability of voltage and frequency of a photovoltaic micro-grid system, and has plug-and-play performance and higher reliability. The subsystem with stronger photovoltaic power generation capacity at the source end outputs a higher power value, and the subsystem with weaker photovoltaic power generation capacity at the source end outputs a lower power value, so that the same power allowance is kept for all photovoltaic power generation subsystems, and better dynamic power adjustment is facilitated; and because the output power of the photovoltaic power generation subsystem is unbalanced, the service life of part of the photovoltaic power generation subsystem is shortened. Further, the photovoltaic microgrid control method provided by the embodiment of the invention fully considers the stable operation area and the capacity limitation of the centralized inverter, can quickly recover the working state of the photovoltaic power generation subsystem from instability to stability, and better ensures the stability of the voltage and the frequency of the photovoltaic microgrid system.
Finally, the system provided by the present invention is only a preferred embodiment, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A photovoltaic microgrid system, comprising: a plurality of two-stage photovoltaic power generation subsystems connected in parallel;
any of the two-stage photovoltaic power generation subsystems, comprising: the system comprises a plurality of power optimizers, a plurality of power optimizer control units, a centralized inverter and a centralized inverter control unit;
the plurality of power optimizers are connected in series; the output end of the plurality of power optimizers connected in series is connected with the input end of the centralized inverter;
each power optimizer corresponds to one power optimizer control unit; the power optimizer control unit is used for switching into two different working modes according to the output voltage of the power optimizer and performing hysteresis control on the power optimizer;
the centralized inverter control unit is used for controlling the output power of the centralized inverter according to the available maximum active power of the centralized inverter, so that the difference between the available maximum active power and the output power of the centralized inverter of each two-stage photovoltaic power generation subsystem is equal.
2. The photovoltaic microgrid system of claim 1, wherein the centralized inverter control unit comprises: the device comprises a power calculation module, a power outer ring control module, an available maximum power dynamic estimation module, a voltage and current control module and a PWM (pulse width modulation) module;
the power calculation module is used for acquiring the active power P output by the centralized inverter according to the output voltage and the output current of the centralized inverter0And reactive power Q0；
The available maximum power dynamic estimation module is used for acquiring the available maximum active power of the centralized inverter according to the input current and the input voltage of the centralized inverterAnd maximum available reactive power
The power outer ring control module is used for controlling the output of the centralized inverter according to the active power P0Reactive power Q0Available maximum active powerAnd maximum available reactive powerObtaining a reference voltage Vrsinωrt；
The voltage current control module is used for controlling the current according to the reference voltage Vrsinωrt, generating a voltage reference signal in the centralized inverter;
and the PWM modulation module is used for modulating the voltage reference signal in the centralized inverter and generating a control signal of the centralized inverter.
3. The photovoltaic microgrid system of claim 2, wherein the active power P output by the centralized inverter and obtained by the power calculation module0And reactive power Q0Are respectively as
<mrow> <msub> <mi>P</mi> <mi>o</mi> </msub> <mo>=</mo> <mfrac> <mrow> <msub> <mi>V</mi> <mrow> <mi>o</mi> <mi>a</mi> <mi>c</mi> </mrow> </msub> <msub> <mi>I</mi> <mrow> <mi>o</mi> <mi>a</mi> <mi>c</mi> </mrow> </msub> </mrow> <mrow> <mi>&tau;</mi> <mi>s</mi> <mo>+</mo> <mn>1</mn> </mrow> </mfrac> <mo>;</mo> <msub> <mi>Q</mi> <mi>o</mi> </msub> <mo>=</mo> <mfrac> <mrow> <msubsup> <mi>V</mi> <mrow> <mi>o</mi> <mi>a</mi> <mi>c</mi> </mrow> <mo>&prime;</mo> </msubsup> <msub> <mi>I</mi> <mrow> <mi>o</mi> <mi>a</mi> <mi>c</mi> </mrow> </msub> </mrow> <mrow> <mi>&tau;</mi> <mi>s</mi> <mo>+</mo> <mn>1</mn> </mrow> </mfrac> </mrow>
Wherein, VoacTo concentrate the output voltage of the inverter, IoacIs the output current of the central inverter, V'oacIs a VoacThe voltage lagging by 90 degrees, τ, is the low pass filter constant.
4. The photovoltaic microgrid system of claim 2, wherein the maximum available active power of the concentrated inverters obtained by the maximum available power dynamic estimation moduleAnd maximum available reactive powerRespectively as follows:
when the input voltage V of the concentrated inverter is higher than the reference voltage VbusBelow Vbus,minWhen, the available maximum active power of the concentrated inverterAnd maximum available reactive powerAre respectively as
<mrow> <msubsup> <mi>P</mi> <mrow> <mi>max</mi> <mo>_</mo> <mi>t</mi> </mrow> <mo>*</mo> </msubsup> <mo>=</mo> <msub> <mi>P</mi> <mrow> <mi>r</mi> <mi>e</mi> <mi>a</mi> <mi>l</mi> <mi>t</mi> <mi>i</mi> <mi>m</mi> <mi>e</mi> </mrow> </msub> <mo>=</mo> <msub> <mi>V</mi> <mrow> <mi>b</mi> <mi>u</mi> <mi>s</mi> </mrow> </msub> <msub> <mi>i</mi> <mrow> <mi>b</mi> <mi>u</mi> <mi>s</mi> </mrow> </msub> <mo>;</mo> <msubsup> <mi>Q</mi> <mrow> <mi>max</mi> <mo>_</mo> <mi>t</mi> </mrow> <mo>*</mo> </msubsup> <mo>=</mo> <msqrt> <mrow> <msubsup> <mi>S</mi> <mrow> <mi>m</mi> <mi>a</mi> <mi>x</mi> </mrow> <mn>2</mn> </msubsup> <mo>-</mo> <msubsup> <mi>P</mi> <mrow> <mi>max</mi> <mo>_</mo> <mi>t</mi> </mrow> <mrow> <mo>*</mo> <mn>2</mn> </mrow> </msubsup> </mrow> </msqrt> </mrow>
Wherein,in order to concentrate the maximum available active power of the inverter,to concentrate the maximum available reactive power, P, of the inverterrealtimeFor concentrating the real-time power of the inverter, SmaxFor concentrating the maximum value of the apparent capacity of the inverter, Vbus,minFor concentrating the minimum output voltage allowed by the inverter, ibusFor concentrating the input current of the inverter, VbusIs the input voltage of the concentrated inverter;
when the input voltage V of the concentrated inverter is higher than the reference voltage VbusHigher than Vbus,maxThe maximum active power available from the central inverterAnd maximum available reactive powerAre respectively as
<mrow> <msubsup> <mi>P</mi> <mrow> <mi>max</mi> <mo>_</mo> <mi>t</mi> </mrow> <mo>*</mo> </msubsup> <mrow> <mo>(</mo> <mi>k</mi> <mo>+</mo> <mn>1</mn> <mo>)</mo> </mrow> <mo>=</mo> <msubsup> <mi>P</mi> <mrow> <mi>max</mi> <mo>_</mo> <mi>t</mi> </mrow> <mo>*</mo> </msubsup> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> </mrow>
<mrow> <msubsup> <mi>Q</mi> <mrow> <mi>max</mi> <mo>_</mo> <mi>t</mi> </mrow> <mo>*</mo> </msubsup> <mrow> <mo>(</mo> <mi>k</mi> <mo>+</mo> <mn>1</mn> <mo>)</mo> </mrow> <mo>=</mo> <msqrt> <mrow> <msubsup> <mi>S</mi> <mrow> <mi>m</mi> <mi>a</mi> <mi>x</mi> </mrow> <mn>2</mn> </msubsup> <mo>-</mo> <msubsup> <mi>P</mi> <mrow> <mi>max</mi> <mo>_</mo> <mi>t</mi> </mrow> <mrow> <mo>*</mo> <mn>2</mn> </mrow> </msubsup> <mrow> <mo>(</mo> <mi>k</mi> <mo>+</mo> <mn>1</mn> <mo>)</mo> </mrow> </mrow> </msqrt> </mrow>
Wherein,to concentrate the maximum active power available to the inverter at the kth beat,for the (k +1) th beat the maximum active power available for the inverter is concentrated,centralizing the available maximum reactive power of the inverter for the (k +1) th beat, SmaxFor concentrating the maximum value of the apparent capacity of the inverter, Vbus,maxTo concentrate the maximum output voltage allowed by the inverter.
5. The photovoltaic microgrid system of claim 4, wherein the power outer loop control module obtains ω in the reference voltagerAnd VrAre respectively as
<mrow> <msub> <mi>&omega;</mi> <mi>r</mi> </msub> <mo>=</mo> <msup> <mi>&omega;</mi> <mo>*</mo> </msup> <mo>-</mo> <mi>m</mi> <mrow> <mo>(</mo> <msub> <mi>P</mi> <mi>o</mi> </msub> <mo>-</mo> <msubsup> <mi>P</mi> <mrow> <mi>max</mi> <mo>_</mo> <mi>t</mi> </mrow> <mo>*</mo> </msubsup> <mo>)</mo> </mrow> <mo>+</mo> <mi>k</mi> <mrow> <mo>(</mo> <msub> <mi>V</mi> <mrow> <mi>b</mi> <mi>u</mi> <mi>s</mi> </mrow> </msub> <mo>-</mo> <msubsup> <mi>V</mi> <mrow> <mi>b</mi> <mi>u</mi> <mi>s</mi> </mrow> <mo>*</mo> </msubsup> <mo>)</mo> </mrow> </mrow>
<mrow> <msub> <mi>V</mi> <mi>r</mi> </msub> <mo>=</mo> <msup> <mi>V</mi> <mo>*</mo> </msup> <mo>-</mo> <mi>n</mi> <mrow> <mo>(</mo> <msub> <mi>Q</mi> <mi>o</mi> </msub> <mo>-</mo> <msubsup> <mi>Q</mi> <mrow> <mi>max</mi> <mo>_</mo> <mi>t</mi> </mrow> <mo>*</mo> </msubsup> <mo>)</mo> </mrow> </mrow>
Wherein, ω isr、VrReference values of angular frequency and amplitude, omega, respectively, for the output voltage of the central inverter*、V*The angular frequency and the amplitude of the output voltage of the centralized inverter in a rated state are respectively shown, m and n are respectively the droop coefficients of active-angular frequency droop (P-omega) and reactive-voltage droop (Q-V) of the centralized inverter,respectively the maximum active power available and the maximum reactive power available, V, of the central inverterbus、The input voltage of the concentrated inverter and the rated reference value thereof are respectively, and k is a regulating coefficient.
6. The photovoltaic microgrid system of claim 4, characterized in that reference values are rated according to input voltages of the concentrated invertersDetermining a minimum output voltage allowed by the centralized inverter and a maximum output voltage allowed by the centralized inverter.
7. The photovoltaic microgrid system of claim 1 or 2, wherein the power optimizer control unit switches to two different operating modes according to the output voltage of the power optimizer, further comprising:
when the output voltage V of the power optimizerdcBelow Vdc,minWhen the power optimizer control unit is switched to a maximum power tracking working mode; wherein, Vdc,minIs a power advantageThe minimum output voltage allowed by the quantizer;
when the output voltage V of the power optimizerdcHigher than Vdc,maxWhen the power optimizer control unit is switched to a direct-through working mode; wherein, Vdc,maxThe maximum output voltage allowed by the power optimizer.
8. The photovoltaic microgrid system of claim 7, wherein the reference value is based on an output voltage of the power optimizerDetermining the minimum output voltage V allowed by the power optimizerdc,minAnd the maximum output voltage V allowed by the power optimizerdc,max；
Output voltage reference value of the power optimizerIs composed of
<mrow> <msubsup> <mi>V</mi> <mrow> <mi>d</mi> <mi>c</mi> </mrow> <mo>*</mo> </msubsup> <mo>=</mo> <mfrac> <msubsup> <mi>V</mi> <mrow> <mi>b</mi> <mi>u</mi> <mi>s</mi> </mrow> <mo>*</mo> </msubsup> <mi>n</mi> </mfrac> </mrow>
Wherein,and n is the total number of the power optimizers in the two-stage off-grid photovoltaic power generation subsystem.
9. A photovoltaic micro-grid system control method is characterized by comprising the following steps: for any one of the photovoltaic power generation sub-systems,
s1, according to the output voltage V of the centralized inverteroacAnd an output current IoacObtaining the active power P output by the centralized inverteroAnd reactive power Qo；
S2, according to the input current i of the centralized inverterbusAnd an input voltage VbusObtaining the maximum active power available for the centralized inverterAnd maximum available reactive power
S3, according to the active power P of the centralized inverteroReactive power QoAvailable maximum active powerAnd maximum available reactive powerObtaining a reference voltage Vrsinωrt；
S4, according to the reference voltage VrsinωrAnd t, generating a control signal of the centralized inverter.
10. The photovoltaic microgrid system control method according to claim 9, wherein the step S4 further comprises:
s41, according to the reference voltage Vrsinωrt, generating a voltage reference signal in the centralized inverter;
and S42, modulating the voltage reference signal in the centralized inverter and generating a control signal of the centralized inverter.
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107994614A (en) * | 2017-12-22 | 2018-05-04 | 上能电气股份有限公司 | A kind of collecting and distributing type photovoltaic inverting system cooperative control method |
| CN109787289A (en) * | 2019-03-15 | 2019-05-21 | 矽力杰半导体技术(杭州)有限公司 | Power conversion system, photovoltaic optimizer and power tracking method |
| CN110474556A (en) * | 2018-05-10 | 2019-11-19 | Ls产电株式会社 | Inverter control method |
| CN111009918A (en) * | 2019-12-13 | 2020-04-14 | 珠海格力电器股份有限公司 | Method and device for controlling power optimizer in photovoltaic grid-connected system |
| CN113992050A (en) * | 2021-10-19 | 2022-01-28 | 浙江腾圣储能技术有限公司 | Inverter circuit, inverter control method and photovoltaic system |
| CN115411771A (en) * | 2022-08-24 | 2022-11-29 | 华为数字能源技术有限公司 | Photovoltaic power generation system and control method thereof |
| CN118426536A (en) * | 2024-07-03 | 2024-08-02 | 浙江明禾新能科技股份有限公司 | Maximum power point tracking control method based on photovoltaic cell unit |
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| CN107994614A (en) * | 2017-12-22 | 2018-05-04 | 上能电气股份有限公司 | A kind of collecting and distributing type photovoltaic inverting system cooperative control method |
| CN110474556A (en) * | 2018-05-10 | 2019-11-19 | Ls产电株式会社 | Inverter control method |
| CN110474556B (en) * | 2018-05-10 | 2021-05-14 | Ls产电株式会社 | Inverter control method |
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| CN111009918A (en) * | 2019-12-13 | 2020-04-14 | 珠海格力电器股份有限公司 | Method and device for controlling power optimizer in photovoltaic grid-connected system |
| CN113992050A (en) * | 2021-10-19 | 2022-01-28 | 浙江腾圣储能技术有限公司 | Inverter circuit, inverter control method and photovoltaic system |
| CN115411771A (en) * | 2022-08-24 | 2022-11-29 | 华为数字能源技术有限公司 | Photovoltaic power generation system and control method thereof |
| CN118426536A (en) * | 2024-07-03 | 2024-08-02 | 浙江明禾新能科技股份有限公司 | Maximum power point tracking control method based on photovoltaic cell unit |
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