KR101444732B1 - Grid converter and method thereof - Google Patents

Abstract

The present invention relates to a control apparatus for reducing direct current link ripples when three-phase imbalance occurs at a grid-connected converter and a control method thereof, wherein the grid-connected converter comprises a power component extracting device for extracting an alternating current and a direct current component from a three phase alternating current power source; a reference voltage generating device for receiving the alternating current and the direct current component from the power component extracting device and generating alternating current and a direct current reference voltage; a space vector pulse modulation part for receiving the alternating current and the direct current reference voltage from the reference voltage generating device and adjusting voltage to be applied to a gate of an insulated gate bipolar transistor bridge; and the insulated gate bipolar transistor bridge for receiving gate voltage from a space vector pulse modulation control part and transforming the three phase alternating power source into direct current voltage. The present invention controls a ripple of direct current (DC) link voltage to be minimized even if three phase grid voltage is unbalanced, thereby controlling current, flowing in the insulated gate bipolar transistor (IGBT) bridge, under a set level.

Description

[0001] The present invention relates to a grid-connected converter and a control method thereof.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grid-connected converter for converting a three-phase AC power source to a direct current (DC) voltage, and more particularly, to a grid-type converter capable of stably operating in a three-phase unbalanced state.

A grid-connected converter is a device that forms a direct current voltage on a capacitor called a direct current (DC) link from three-phase ac system voltage. It is a component widely used such as a regenerative motor drive driver and a grid-connected wind turbine. The inverter uses a direct current (DC) link voltage to generate the amplitude and frequency of the alternating current (AC) voltage that achieves the control purpose.

FIG. 13 is a configuration diagram of a conventional grid-connected converter system.

The conventional grid-connected converter includes a phase locked loop 20 that detects a phase from a three-phase power supply 10 and an insulated gate bipolar transistor bridge (IGBT) 20 that forms a direct current (DC) Gate Bipolar Transistor (Bride) 40, a DC Link Voltage Control 50 for controlling the DC link voltage, a current control unit for controlling the current for charging the DC link capacitor, 60, and a PWM control section (Pulse Width Modulation) 70 for applying a gate signal required for switching to an insulated gate bipolar transistor (IGBT) bride 40. Here, the inductor 30 is used for boosting the DC link voltage.

This conventional grid-connected converter assumes a state in which the three-phase power supply is balanced, and therefore, when the ripple of the DC link voltage is largely generated in the three-phase unbalance condition, . If the DC link voltage becomes less than the target value in the situation where the ripple of the DC link voltage becomes large, the system side converter draws the power from the system toward the DC (DC) link to charge the capacitor voltage, ) If the link voltage is greater than the target value, the power is sent to the system to discharge the capacitor voltage. Therefore, if the ripple increases, there is a risk that the overcurrent flows through the insulated gate bipolar transistor (IGBT) The protection operation control for protecting the device is activated and the control is stopped so that the availability of the converter operation is degraded.

In addition, there is a problem that adversely affects the control of an inverter using a direct current (DC) link voltage.

Korean Registered Patent No. 20-0416152 Korean Patent Publication No. 10-2009-0053009

SUMMARY OF THE INVENTION It is an object of the present invention to provide a grid-connected converter that minimizes the ripple of a DC link voltage even if a three-phase system voltage imbalance occurs.

In addition, even if an unbalance occurs in the three-phase system voltage, the current flowing through the insulated gate bipolar transistor bridge (IGBT) is controlled to be small so that an excessive current flows through the insulated gate bipolar transistor bridge (IGBT) To provide a grid-connected converter.

According to an aspect of the present invention, there is provided a power component extractor for extracting an AC component and a DC component from a three-phase AC power source; A reference voltage generator receiving the AC and DC components of the power component extractor and generating a reference voltage of AC and DC; A space vector pulse modulator receiving the AC and DC reference voltages from the reference voltage generator and adjusting a voltage to be applied to the gate of the insulated gate bipolar transistor bridge; And an insulated gate bipolar transistor bridge that receives the gate voltage output from the space vector pulse modulation control unit and converts the three-phase alternating current power to a direct current voltage.

The power component extractor may include a DC component extractor and an AC component extractor, and the DC component extractor and the AC component extractor may include a static coordinate converter, a rotation coordinate converter, and a crossflow extractor.

Further, the crossflow extractor provides a grid-connected converter including a band elimination filter and an adder.

Also, the reference voltage generator provides a grid-connected converter including a voltage controller composed of a proportional integral controller, a d-axis current controller, a q-axis current controller, and an adder.

Further, the present invention provides a method of driving a three-phase AC power supply, comprising: extracting AC and DC components from a three-phase AC power supply; Generating an AC and a DC reference voltage using the AC and DC components; And adjusting a voltage to be applied to the gate of the insulated gate bipolar transistor bridge using the reference voltage.

Also, before the step of extracting the AC and DC components from the three-phase AC power supply, the method further comprises a step of converting the three-phase power supply to the stationary coordinate system and converting the three-phase power to the rotating coordinate system.

The step of extracting the AC component and the DC component from the three-phase AC power source includes extracting a DC component through a band-elimination filter having a cut-off frequency that is twice the frequency of the three-phase power source, A method of controlling a grid-connected converter for extracting an AC component in addition to an upper power supply is provided.

The step of generating AC and DC reference voltages using the AC and DC components may include generating a DC reference value using the DC components extracted from the three phase power source and using the AC components extracted from the three- A method of controlling a grid-connected converter for generating an AC reference value is provided.

Also, a method of generating the q-axis DC PWM reference voltage among the methods for generating the q-axis DC reference value is to generate a q-axis current reference value that makes the difference between the target DC link voltage and the voltage value of the DC link sensor proportional to zero , The q-axis current reference value and the q-axis DC current component extracted from the three-phase power source are proportionally integrated, and the q-axis current component extracted from the q- A method of controlling a grid-connected converter for obtaining a shaft DC PWM reference voltage is provided.

The method of generating the d-axis DC reference voltage among the methods for generating the d-axis reference value may include a method of proportionally integrating the difference between the d-axis current reference value set to zero (0) and the d-axis dc current component extracted from the three- The present invention provides a control method of a grid-connected converter for obtaining a d-axis DC PWM reference voltage by reflecting a reactor value of a q-axis DC current component affecting a d-axis.

Also, a method of generating the q-axis AC reference voltage among the methods of generating the q-axis reference value is characterized by setting the target ac link voltage value to zero and proportionally integrating the difference from the voltage value of the d- 0), and the difference between the q-axis AC reference value and the q-axis AC current component extracted from the three-phase power source is proportionally integrated, and the feed forward power value and the d- The present invention also provides a method of controlling a grid-connected converter that obtains a q-axis alternating-current PWM reference voltage by reflecting a reactor value affecting the q-axis ac PWM reference voltage.

The method for generating the d-axis alternating current PWM reference voltage among the methods for generating the alternating current reference value may comprise the steps of: integrating the difference between the d-axis alternating current reference value set to zero (0) and the d-axis alternating current component extracted from the three- there is provided a control method of a grid-connected converter for obtaining a d-axis ac PWM reference voltage by reflecting a reactor value that a q-axis ac current component affects a d-axis.

The step of adjusting the voltage to be applied to the gate of the insulated gate bipolar transistor bridge using the reference voltage may include adding the DC and AC component values extracted from the three-phase power source to a voltage intended for the DC link, The present invention provides a method of controlling a grid-connected converter that obtains a voltage, obtains a final PWM reference voltage by adding an AC PWM reference voltage to a DC PWM reference voltage, converts the resulting PWM reference voltage to a stationary coordinate system,

A method of generating a final PWM reference voltage by adding an AC PWM reference voltage to the DC PWM reference voltage includes dividing the DC and AC PWM reference voltages into voltages of a d axis and a q axis, And a q-axis component to generate a final PWM reference voltage for each of the d-axis and the q-axis.

As described above, according to the grid-connected converter and the control method thereof, even when the three-phase system voltage is unbalanced, the insulated gate bipolar transistor bridge (IGBT) can be minimized by controlling the ripple of the DC link voltage to the minimum, It is possible to control the current flowing through the resistor R to a predetermined level or less. Accordingly, the overcurrent generated in the control method to which the present invention is not applied is prevented to protect the insulated gate bipolar transistor bridge (IGBT) power device, and control disruption does not occur, thereby increasing the availability of the system.

Further, the case where the control of the grid-connected type converter can not be controlled can be solved and the availability can be increased. Therefore, reliability and stability are improved.

In addition, since a minimum configuration is added to the existing grid-connected converter, high efficiency and miniaturization can be achieved without increasing the cost.

1 is a block diagram of a grid-connected converter according to a preferred embodiment of the present invention.
FIG. 2 is a view showing an internal configuration of an insulated gate bipolar transistor bridge (IGBT).
3 is a block diagram showing the operation of the current component extractor and the voltage component extractor in the power component extractor.
4 is a view for defining a voltage and a current to be used by the power component extractor of FIG.
5, the still coordinate converter and the rotation coordinate converter are converted into a stationary reference frame by using a matrix or a complex number vector, and then converted into a rotating reference frame FIG.
6 is a waveform when the three-phase power source in the equilibrium state is dq converted.
7 is a waveform showing the result of dq conversion of the current or voltage in the unbalanced state.
8 is an internal block diagram of a cross flow extractor that separates an alternating current (AC) component and a direct current (DC) component after dq conversion.
FIG. 9 is a graph showing the values of DC (direct current) and AC (alternating current) components after the dq converted power has passed through the AC extractor.
FIG. 10 is a block diagram showing the structure of a direct current (DC) PWM reference unit.
FIG. 11 is a block diagram illustrating the structure of the AC PWM reference portion of the reference voltage generator.
12 is a block diagram showing the internal structure of the space vector pulse modulator 400. Referring to FIG.
FIG. 13 is a configuration diagram of a conventional grid-connected converter system.
14 is a waveform showing the operation of the conventional grid-connected converter controller.
FIG. 15 is a diagram illustrating operation of an existing converter controller in a three-phase unbalanced state.
FIG. 16 is an operation waveform when the grid-connected converter according to the preferred embodiment of the present invention operates in a three-phase unbalanced power supply state.

The present invention proposes a method of reducing the direct current (DC) link voltage ripple due to the three-phase system voltage imbalance by constituting a controller that compensates for the unbalance of the three-phase power source. That is, the conversion result is classified into a DC component and an AC component through a mathematical conversion process using the values of the three-phase voltage sensor. From this, a reference voltage is generated and the voltage applied to the gate of the insulated gate bipolar transistor bridge by the space vector modulation section is adjusted to minimize the ripple of the direct current (DC) link voltage.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the invention is not intended to be limited to the particular forms disclosed, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

1 is a block diagram of a grid-connected converter according to a preferred embodiment of the present invention.

The grid-connected converter of the present invention includes a phase locked loop (PLL) 500 for detecting the phase of a three-phase system, an insulated gate bipolar transistor (IGBT) for converting a three- ] Bride, 100) and a three-phase AC power source, a power component extractor (200) for extracting voltage and current of DC and AC components, a voltage generator (DC) and alternating current (AC) from the reference voltage generator 300 and the reference voltage generator 300 and outputs the reference voltage to the gate of the insulated gate bipolar transistor (IGBT) And a space vector pulse modulator 400 for generating a voltage signal to be applied and adjusting a (DC) link voltage.

An insulated gate bipolar transistor (IGBT) bridge 100 forms a direct current (DC) link voltage through switching. This insulated gate bipolar transistor (IGBT) bridge 100 transfers power from a system to a direct current (DC) link when power is required at the load side, And controls the insulated gate bipolar transistor (IGBT) bridge 100 to transmit power to the system.

However, in the conventional grid-connected converter, when the ripple increases in the process of moving power between the load and the system, there is a risk that the overcurrent flows to the insulated gate bipolar transistor bridge (IGBT) .

In order to solve this problem, the present invention extracts direct current and alternating current components from a three-phase power source, generates these reference voltages, and controls the space vector pulse modulator 400 to generate an insulated gate bipolar transistor (IGBT) 100 are controlled.

FIG. 2 is a view showing an internal configuration of an insulated gate bipolar transistor (IGBT) bridge 100.

마다 1쌍은 다이오드의 애노드(Anode)가 3상 전원에 연결되고, 나머지 1쌍은 다이오드의 캐소드(Cathode)가 3상 전원에 연결된다. 이렇게 총 6쌍이 3상 전원에 연결된다. An insulated gate bipolar transistor (IGBT) bridge 100 includes a pair of insulated gate bipolar transistors (IGBTs) 110 and diodes 120, Consists of. Each three-phase power source

One pair is connected to the anode of the diode to the three-phase power supply, and the other pair is connected to the three-phase power supply of the cathode of the diode. Thus, a total of six pairs are connected to the three-phase power supply.

An insulated gate bipolar transistor (IGBT) 110 is connected in parallel with a diode 120 to determine a conduction of a diode 120 according to a signal applied from a gate driving circuit, Respectively.

3 is a block diagram showing operations of a current component extractor 210, a voltage component extractor 220 and a DC link component extractor 230 in a power source component extractor 200, And a voltage and a current to be used by the power component extractor 200 of FIG.

는 3상 전원에서의 각 상의 전원을 나타내는 기호이고,

은 중성점과 a상, b상 및 c상과의 상전압을 나타낸다. 그리고, 3상 교류 전원에서 나오는 선전류를

, 직류(DC)링크 캐패시터 양단의 전압을

, 부하단으로 빠지는 전류를

이라고 정의한다. 여기서,

은 각각

에 대응되며,

는

에 대응될 수 있다.In FIG. 4

Is a symbol representing the power of each phase in the three-phase power source,

Represents the phase voltage between the neutral point and the phases a, b, and c. Then, the line current from the three-phase AC power source

, The voltage across the DC (DC) link capacitor

, The current that flows into the negative terminal

. here,

Respectively

Respectively,

The

Lt; / RTI >

3, the power component extractor 200 includes a stationary coordinate converter 211 for converting a three-phase power source, which is a time-varying function, into a stationary coordinate system, a rotational coordinate converter 212 for converting the stationary coordinate system into a rotational coordinate system, And a cross AC extractor 213 for extracting a direct current (DC) component and an alternating current (AC) component.

When the power source extractor 200 receives the three-phase voltage and the current, the applied three-phase voltage and current are divided and applied to the voltage component extractor 220 and the current component extractor 210, respectively. The three-phase voltage applied to the voltage component extractor 220 is converted into a d-q-axis voltage equation via the stationary coordinate transformer 211 and the rotation coordinate transformer 212. Similarly, the three-phase current applied to the current component extractor 210 is also converted into a d-q-axis current equation through the stationary coordinate converter 211 and the rotational coordinate converter 212. The converted voltage and current are finally input to the AC extractor 213 to detect DC and AC components. The direct current (DC) link extractor 230 receives a voltage across the direct current (DC) link capacitor and extracts a direct current (DC) component and an alternating current (AC) component on the direct current (DC) link side. The direct current (DC) link component extractor 230 has the same structure as the crossflow extractor 213.

In Figure 3, the reason for converting the three-phase power source to the d-q coordinate axis is to quickly interpret the component values from the three-phase power source. The mutual inductance, which indicates the degree of linkage of magnetic flux between two windings in a generator generating three-phase power, is a time varying function as a function of the rotor speed. Due to this time-varying characteristic, a generator generating a three-phase power source is represented by a time variant differential equation having a time-varying coefficient as shown in Equation 1 below.

(수식 1)

(Equation 1)

Here, the time-varying coefficient is removed from the equation (1) by passing through the stationary coordinate transformer 211 and the rotation coordinate transformer 212, so that the analysis can be easily performed. Also, by using these coordinate transformations, the physical quantities of the abc 3-phase generators are converted into the values of the orthogonal coordinate system composed of d and q axes. Based on this, the power control of the alternator can be quickly analyzed There is a number.

5, the stationary coordinate converter 211 and the rotational coordinate converter 212 convert the stationary reference frame into a stationary reference frame using a matrix or a complex number vector, Rotating Reference Frame). Referring to FIG.

The stationary coordinate transformer 211 is convenient to handle because it expresses each state variable as a direct current (DC) quantity by expressing power of the equation represented by three phases as a two-phase coordinate system rotating at an angular frequency ω.

The transformation formula of the stationary coordinate transformer 211 is expressed by a matrix as follows.

(수식 2)

(Equation 2)

Here, if the values of [alpha] and [beta] are input to the rotation coordinate transformer 212 except for the neutral axis or the image axis n,

(수식 3)

(Equation 3)

The voltage and current of the d-q axis are converted.

The voltage and current values converted to the rotational coordinate system of the d-q axis are input to the AC extractor 213 to extract a DC value and an AC value.

6 is a waveform when the three-phase power source in a balanced state is d-q converted.

로 일정한 값을 갖는 것을 알 수 있다.In case of 3-phase equilibrium state, as shown in the figure, the d-axis value of 6-2 is '0' and the q-axis value is a peak value of 3-phase power

As shown in Fig.

On the other hand, FIG. 7 shows waveforms when the three-phase power source in the unbalanced state is converted to dq. The result of dq conversion of the unbalanced current or voltage shows a waveform that does not have a constant value as shown in FIG. Can be seen. That is, the d-axis 7-1 vibrates with ripple near '0', and the q-axis vibrates as in 7-2.

Such a ripple causes the value of the DC (DC) link and the value of the current flowing in the insulated gate bipolar transistor (IGBT) to diverge. Accordingly, the present invention provides a grid-connected converter and a control method thereof that can stably operate not only in a three-phase balanced state but also in a three-phase unbalanced state.

8 is an internal block diagram of a cross flow extractor that separates an alternating current (AC) component and a direct current (DC) component after dq conversion. The crossflow extractor 213 is constituted by a band elimination filter 213-1 and an adder 213-2

로 회전하는

축에서The reason why the alternating current (AC) component and the direct current (DC) component are separated again from the power source after the dq conversion is for ease of control. Counterclockwise

Spinning

On axis

(수식 4)

(Equation 4)

는 시계방향으로

로 회전하는

축에서의 음(negative sequence)의 값이다. 따라서 직교류추출기(213)의 대역제거필터(213-1)을 사용하여 수식 4의 음(negative sequence)의 값을 없애주면 직류(DC)성분과 교류(AC)성분으로 분류할 수 있다.here,

Clockwise

Spinning

The value of the negative sequence in the axis. Therefore, if the negative sequence value of Equation 4 is removed by using the band elimination filter 213-1 of the crossflow extractor 213, it can be classified into a direct current (DC) component and an alternating current (AC) component.

가 중심주파수

인 대역제거필터(Band Stop Filter,213-1)을 통과하면 직류(DC)성분을 얻을 수 있다. 이를 다시 덧셈기(213-2)를 통하여 처음 신호인

에서 빼주면 교류(AC)성분을 얻을 수 있다. 여기서,

는 3상 전원의 주파수이다. The crossflow extractor 213 is constituted by a band elimination filter 213-1 and an adder 213-2. dq converted voltage

Center frequency

A direct current (DC) component can be obtained through the band stop filter 213-1. Then, the adder 213-2 adds the first signal

The AC component can be obtained. here,

Is the frequency of the three-phase power supply.

The process of extracting direct current (DC) and alternating current (AC) from the d-q converted current is the same as the process of FIG.

The transfer function equation G (s) of the band elimination filter 213-1 used in the present invention is as follows.

However, the above transfer function is a transfer function according to an embodiment of the present invention, and the transfer function can be variously converted according to the application of the present invention.

FIG. 9 is a diagram showing the values of components of direct current (DC) and alternating current (AC) after the d-q converted power has passed through the direct current AC extractor 213.

9-1 is a direct current (DC) component, and 9-2 is an alternating current (AC) component.

Now, the reference voltage generator 300 for determining the voltage to be applied to the gate of the insulated gate bipolar transistor (IGBT) bridge 100 will be described with reference to the above values.

The reference voltage generator 300 of FIG. 1 includes a direct current (DC) PWM reference unit 310 and an alternating current (AC) PWM reference unit 320.

10 is a block diagram illustrating the structure of a direct current (DC) PWM reference unit 310. Referring to FIG.

,

을 생성하게 된다. 여기서,

,

은 계통 연계형 컨버터가 변환하고자 하는 직류 전압의 목적 값이다.When the dq-converted current and voltage extracted from the power source component extractor 200 are input to the DC (direct current) PWM reference unit 310, an internal operation is performed to convert the reference voltage of the DC voltage of the dq axis

,

. here,

,

Is the target value of the DC voltage to be converted by the grid-connected converter.

,

전압을 생성하는 과정은 다음과 같다.In the direct current (DC) PWM reference unit 310

,

The process of generating the voltage is as follows.

(10-1), 직류(DC)링크의 센서 값

(10-2)는 덧셈기(311)로 입력된 후, 비례적분제어기(Proportional-Integral Controller,312)로 입력되게 된다. 첫번째 비례적분제어기(Proportional-Integral Controller)를 전압제어기(312)라고 한다. 전압제어기(312)는

의 신호를 적분(integral)하여 제어신호를 만든다. 이때, 전압제어기(312)의 전달함수는

이다. 이러한 전압제어기(312)는

와

의 차이값을 0으로 만드는 q축의 전류 레퍼런스(10-4)를 구하게 된다. 이런 q축의 전류 레퍼런스(10-4)는 전원성분추출기(200)에서 생성한

와 다시 덧셈기(311)에서 더해지고 그 결과 q축의 전류 레퍼런스(10-4)와

차가 다시 q축 전류제어기(314)로 입력되어 적분 제어신호를 만든다. 이 전류제어기(314)에서 출력된 값은 d축에서 q축으로의 간섭분

와 더해지고 여기에 전원전압 성분

도 피드포워드 보상이 된다. 따라서, 전압제어기(312)에서 출력은 q축 전류의 기준 지령치가 되고, 실제 q축 전류와 비교된 편차가 q축 전류제어기(314)에 의해 q축 전압지령

를 생성하게 되는 것이다. 이때, q축 전류제어기(314)의 전달함수는

이다.First, the DC (DC) link reference value

(10-1), the sensor value of the direct current (DC) link

(10-2) is input to the adder 311 and then input to the proportional-integral controller 312. The proportional- The first proportional-integral controller is referred to as a voltage controller 312. The voltage controller 312

And the control signal is integrated. At this time, the transfer function of the voltage controller 312 is

to be. This voltage controller 312

Wow

The current reference (10-4) of the q-axis which makes the difference value of 0 is obtained. The current reference (10-4) of the q axis is generated by the power component extractor 200

And the adder 311. As a result, the q-axis current reference 10-4 and the q-

The difference is input to the q-axis current controller 314 to generate an integral control signal. The value output from the current controller 314 is the sum of the interference from the d axis to the q axis

And the power voltage component

Feed forward compensation. Therefore, the output from the voltage controller 312 becomes the reference command value of the q-axis current, and the deviation compared with the actual q-axis current is supplied to the q-axis current controller 314 by the q-

. At this time, the transfer function of the q-axis current controller 314 is

to be.

의 편차는

의 전달함수를 갖는 d축 전류제어기(313)에 입력되어 d축의 전압지령을 만든다. 이 과정에서 앞에서 살핀 바와 같이, q축에서 d축으로 간섭분

가 더해져서, 최종적으로 d축 전압지령

를 생성하게 된다.The d-axis current reference 10-3 is also input to the DC (DC) PWM reference unit 310, which has a value of zero. This is because the d-axis current does not generate effective power. d axis current command and actual d axis current

The deviation of

Axis current controller 313 having a transfer function of the d-axis voltage command. In this process, as we have already seen, the interference from the q axis to the d axis

And finally, the d-axis voltage command

.

To simplify this by the equation, the voltage of the DC (DC) link capacitor is

(수식 3)

(Equation 3)

to be. When this equation (3) is d-q axis transformed,

(수식 4)

(Equation 4)

.

를 0으로 제어하면 캐패시터 전압은

에 의해서 결정된다. 따라서,

의 목표값과 현재의

값의 차이값을 0으로 만드는

값을 비례 적분하여

를 만든다. 그리고, 수식 4에서

를 0으로 만드는 PI 제어기에서

값을 계산하여 PWM 레퍼런스를 만든다. In Equation 4,

Is controlled to be 0, the capacitor voltage becomes

. therefore,

Target value and current

Make the difference value of the value 0

By proportionally integrating the values

. In Equation 4,

To the PI controller

Calculate the value to create the PWM reference.

11 is a block diagram illustrating the structure of the AC PWM reference unit 320 of the reference voltage generator 300. Referring to FIG.

(11-1)와 q축 전류의 교류(AC)성분인

(11-2), 직류(DC) 링크 전압의 교류(AC) 성분인

(11-5)를 이용하여 d축 전류의 레퍼런스(11-3)과 직류(DC)링크 전압의 교류(AC)성분의 목표 값, 즉 레퍼런스 값을 0으로 하여

(11-6)과

(11-7)의 교류(AC) PWM 레퍼런스를 구한다.The AC PWM reference unit 320 has the same structure as the DC PWM reference unit 310. However, the AC component of the d-axis current

(11-1) and the alternating current (AC) component of the q-axis current

(11-2), the AC (DC) component of the DC (DC) link voltage

(11-3) of the d-axis current and the AC value of the AC (DC) link voltage, that is, the reference value is set to 0

(11-6) and

(AC) PWM reference of the inverter 11-7.

12 is a block diagram showing the internal structure of the space vector pulse modulator 400. Referring to FIG.

,

에 직류(DC) 성분의 전압 레퍼런스 값인

,

를 더하는 덧셈기(311)과 회전좌표변환기의 역변환기(420), 정지좌표변환기의 역변환기(430), 공간벡터변조기(SVPWM[Space Vector Pulse Width Modulation], 410)으로 구성되어 있다.The spatial vector pulse modulator 400 receives the AC voltage component of the AC component in the d-

,

(DC) component voltage reference value

,

And an inverse transformer 420 of the rotation coordinate transformer, an inverse transformer 430 of the stationary coordinate transformer, and a space vector pulse width modulation (SVPWM) 410. The adder 311 adds the adder 311,

를 구한 다음, 공간벡터변조기(SVPWM[Space Vector Pulse Width Modulation],410)으로 인가된다. 공간벡터변조기(SVPWM[Space Vector Pulse Width Modulation],410)은 입력된

값에 따라 절연 게이트 양극성 트랜지스터 브릿지(IGBT[Insulated Gate Bipolar Transistor] Bridge,100)의 게이트에 인가할 전압을 조절하게 된다.The controller result values of the two-phase rotational coordinate system are restored to three phases so that the space vector pulse modulator 400 can use the space vector pulse modulator (SVPWM) 410 contrary to the power source component extractor 200 do. In order to achieve this, the inverse transformation of the rotational coordinate system and the inverse transformation of the stationary coordinate system are performed,

And then applied to a space vector pulse width modulation (SVPWM) 410. Space Vector Pulse Width Modulation (SVPWM), 410,

The voltage to be applied to the gate of the insulated gate bipolar transistor (IGBT) bridge 100 is controlled according to the value of the gate voltage.

Accordingly, the insulated gate bipolar transistor (IGBT) 111 of the insulated gate bipolar transistor (IGBT) bridge 100 is connected to a three-phase AC power source And the voltage value of the DC link capacitor is adjusted by adjusting the value of the DC link capacitor. That is, even if a current flows from the load side to the DC (direct current) link side, the ripple value generated here is measured to actively adjust the signal applied to the gate of the insulated gate bipolar transistor (IGBT) (DC) link voltage to be constant.

The advantages of the grid-connected converter according to the present invention over the conventional grid-connected type converter are shown in the following graphs.

14 is a diagram showing the results when the conventional grid-connected converter of FIG. 13 is operated under the condition of three-phase balance. FIG.

In FIG. 14, a graph A is a graph showing a voltage of a direct current (DC) link, a graph B is a graph showing a current value flowing into a direct current (DC) link from a load, a graph C shows an inductor current, 3-phase power supply. In the A, B, and C graphs, section 14-3 shows the initial transient state, so it is not included in the scope of analysis. In the following three-phase equilibrium state, the relationship between voltage and current between the load side and the DC link is examined. In the D graph, it can be seen that the power of each phase is equilibrated in a constant size and phase. Therefore, it can be confirmed that the grid-connected converter is operating in the state of three-phase equilibrium. In this state, when looking at point 14-1 of the B graph, it can be seen that the load current temporarily increases and flows into the direct current (DC) link. As a result, the graph A showing the voltage of the direct current (DC) link is temporarily raised at the time of 14-4, but it maintains a stable value after a certain time by the control operation. At the 10-7 point of the C graph, an inductor current is used to send the current from the load side to the DC link side to the system. Also, the 14-2 point of the B graph shows that the current flows from the DC (DC) link side to the load side. As a result, it can be seen that the DC (DC) link voltage temporarily drops at the time point A of FIG. 14-5, but the original value is maintained after a certain time by the control operation. At point 10-8 of the C graph, the inductor (Inductor) current is the waveform to send the load to the direct current (DC) link. As described above, when the three-phase power supply is in the equilibrium state, the DC link is controlled to a constant value after a variation of about 10 [V] even in a transient state in which the direction of the current in the load changes.

FIG. 15 is a diagram illustrating operation of an existing converter controller in a three-phase unbalanced state.

The graphs A, B and C show graphs of the DC link voltage, load current graph, inductor current graph, and three-phase power graph, respectively, as shown in FIG. In FIG. 11, since the time point 15-1 is an initial transient state, it is not included in the category of interpretation. Since the magnitude and phase of each phase in the D graph are not constant, it can be seen that the applied three-phase power source is in an unbalanced state. When the current flows from the load side to the DC link side at point 15-2 in the graph B showing the load current graph, the current flowing to the DC link side at the point 15-5 of the A graph shows the DC link voltage The current flowing through the insulated gate bipolar transistor (IGBT) at the time point 15-4 of the C graph is larger than that of FIG. 14, although it is controlled while generating a small ripple after temporarily rising.

When the current flows from DC (DC) link to the load at 15-3 point of B graph, it can be seen that the voltage fluctuates to about 50 [V] like 15-6 of A graph. In addition, it can be seen that the C graph representing the inductor current oscillates largely at the time point 15-5, and at about 15-5, about 100 [A] current flows, and the insulated gate bipolar transistor (IGBT [Insulated Gate Bipolar Transistor].

Therefore, when the three-phase power supply is in an unbalanced state, there is a risk that the insulated gate bipolar transistor (IGBT [Insulated Gate Bipolar Transistor]) can be easily destroyed by only generating a small ripple of the DC link voltage, .

On the contrary, FIG. 16 is an operation waveform when the grid-connected converter according to the preferred embodiment of the present invention operates in a three-phase unbalanced power supply state.

In the three-phase unbalanced grid voltage conditions such as the D graph, the 16-2 point part is excluded from the analysis as the initial transient section. At point 16-5 of the B graph showing the current flowing to the DC link at the load, the DC link voltage of the A graph also temporarily increases by 20 [V]. However, it remains constant at 700 [V] after a certain time.

In the B graph, the voltage value of the direct current (DC) link of the A graph drops by 40 [V] at 16-6 when the current flows from the direct current (DC) link to the load. However, after a certain period of time, it is maintained at 700 [V] again, and the ripple is greatly reduced.

Also, it can be seen that the C graph indicating the current flowing through the inductor is controlled within a certain range. It can be seen that the C graph in FIG. 15 differs from the large value as it diverges over time. Therefore, in view of such waveform values, the grid-connected converter according to the preferred embodiment of the present invention is capable of controlling the voltage of the direct current (DC) link or the current flowing in the insulated gate bipolar transistor (IGBT [Insulated Gate Bipolar Transistor] It is ensured that stable operation is ensured.

Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. It will be understood that the invention may be varied and varied without departing from the scope of the invention.

10: Three phase power
20: Piel el
30: Inductor
40: Isolation gate bipolar transistor bridge
50:
60:
70: PWM control section
100: Insulated gate bipolar transistor bridge
110: insulated gate bipolar transistor
120: Diode
200: Power component extractor
210: current component extractor
211: stationary coordinate transformer
212: Rotational coordinate converter
213: Crossflow extractor
213-1: band reject filter
213-2: adder
220: Voltage component extractor
230: DC link component extractor
300: Reference voltage generator
311: adder
312: Voltage controller
313: d axis current controller
314: q-axis current controller
400: space vector pulse modulation unit
410: space vector modulator
420: Inverse converter of the rotation coordinate converter
430: Inverse transformer of stationary coordinate transformer
500: Power phase detector

Claims (14)

A power component extractor for extracting AC and DC components from a three-phase AC power source;
A reference voltage generator receiving the AC and DC components of the power component extractor and generating a reference voltage of AC and DC;
A space vector pulse modulator receiving the AC and DC reference voltages from the reference voltage generator and adjusting a voltage to be applied to the gate of the insulated gate bipolar transistor bridge; And
An insulated gate bipolar transistor bridge receiving the gate voltage output from the space vector pulse modulation control unit and converting the three-phase alternating current power to a direct current voltage;
Lt; / RTI >
Wherein the power component extractor includes a DC component extractor and an AC component extractor, wherein the DC component extractor and the AC component extractor include a stationary coordinate transformer, a rotational coordinate transformer, and a crossflow extractor.
delete The method according to claim 1,
Wherein the crossflow extractor includes a band reject filter and an adder.
The method according to claim 1,
Wherein the reference voltage generator includes a voltage controller configured as a proportional integral controller, a d-axis current controller, a q-axis current controller, and an adder.
Extracting AC and DC components from a three-phase AC power source;
Generating an AC and a DC reference voltage using the AC and DC components;
Adjusting a voltage to be applied to the gate of the insulated gate bipolar transistor bridge using the reference voltage;
Lt; / RTI >
The step of extracting AC and DC components from a three-phase AC power supply includes extracting a DC component from a three-phase power supply through a band-elimination filter having a cutoff frequency that is twice the frequency of the three-phase power supply, And a control method of the grid-connected converter for extracting an AC component.
6. The method of claim 5,
Further comprising the step of converting the three-phase power source to a stationary coordinate system and converting the three-phase power source to a rotating coordinate system prior to the step of extracting the AC and DC components from the three-phase AC power source.
delete 6. The method of claim 5,
Wherein the step of generating the AC and DC reference voltages using the AC and DC components comprises generating a DC reference value using the DC components extracted from the three phase power source and using the AC components extracted from the three phase power source, Of the grid-connected converter.
9. The method of claim 8,
A method for generating a q-axis direct current PWM reference voltage among the methods for generating the direct current reference value comprises the steps of: q-axis current reference value for making the difference between the target direct link voltage and the voltage value of the direct link sensor proportional to zero, The q-axis DC current component extracted from the q-axis current reference value and the q-axis DC current component extracted from the q-axis current source are proportionally integrated, and the q-axis DC current component reflecting the feed- Control method of grid - connected converter for obtaining PWM reference voltage.
9. The method of claim 8,
The method for generating the d-axis DC PWM reference voltage comprises the steps of proportionally integrating the difference between the d-axis current reference value set to zero (0) and the d-axis DC current component extracted from the three-phase power source, A method of controlling a grid-connected converter that obtains a d-axis DC PWM reference voltage by reflecting a reactor value of a DC current component affecting a d-axis.
9. The method of claim 8,
A method of generating a q-axis ac PWM reference voltage is a method of generating a q-axis ac PWM reference voltage by setting a target ac link voltage value to zero and proportional-integrating a difference from a voltage value of the dc- Axis AC reference value and the q-axis alternating current component extracted from the three-phase power source is proportionally integrated, and the feed forward power value and the d-axis alternating current component affect the q-axis To obtain a q-axis alternating-current PWM reference voltage by reflecting the reactor value of the q-axis alternating-current PWM reference voltage.
9. The method of claim 8,
The method of generating the d-axis ac PWM reference voltage comprises the steps of: integrating the difference between the d-axis ac reference value set to zero and the d-axis ac current component extracted from the three-phase power source, A method of controlling a grid-connected converter that obtains a d-axis ac PWM reference voltage by reflecting a reactor value of an ac current component affecting a d-axis.
9. The method of claim 8,
The step of adjusting the voltage to be applied to the gate of the insulated gate bipolar transistor bridge using the reference voltage includes adding the DC and AC component values extracted from the three-phase power source to the desired voltage on the DC link, A method of controlling a grid-connected converter that converts an AC PWM reference voltage to a DC PWM reference voltage to obtain a final PWM reference voltage, converts the PWM reference voltage to a still coordinate system, and then converts the same to a three-
14. The method of claim 13,
A method of generating a final PWM reference voltage by adding an AC PWM reference voltage to the DC PWM reference voltage includes dividing the DC and AC PWM reference voltages into voltages of a d axis and a q axis, A method of controlling a grid-connected converter that generates a final PWM reference voltage for each of the d-axis and the q-axis in addition to the axis components.

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