JP2017184321A - Power conversion system, method for controlling power conversion system, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique capable of improving controllability of a reverse power flow without complicating construction.SOLUTION: If power of a power line PL1 based on the current detected by a first current detector CT1 changes from a target value when a first power storage device 21 is in a discharge state, a first power conversion device 31 controls discharge power of the first power storage device 21 so that power P0 of the power line PL1 comes closer to the target value during a predetermined first period. If the power of the power line PL1 based on the current detected by a second current detector CT2 changes from the target value when a second power storage device 22 is in the discharge state, a second power conversion device 32 controls discharge power of the second power storage device 22 so that the power of the power line PL1 comes closer to the target value after the first period has elapsed.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power conversion system that converts DC power into AC power, a control method for the power conversion system, and a program.

  There is known a power conversion system that converts generated power of a solar battery and discharged power of a storage battery into AC power, and outputs the AC power to a commercial power system (hereinafter simply referred to as a power system) and a load via a power line. . Of the output power, the power that has not been consumed by the load is reversed to the power system.

  Under the current system, it is not allowed to reverse the discharge power of the storage battery. Therefore, the reverse power flow cannot be continued for a predetermined time or more. Therefore, the power conversion system detects the reverse power flow using a current detector provided on the power line on the power system side of the load, and controls the discharge power of the storage battery so as not to reverse flow during the discharge of the storage battery (for example, Patent Document 1).

JP 2002-171694 A

  In order to increase the capacity of the storage battery and the AC power that can be output, it is conceivable to install two sets of such power conversion systems in one building and supply the AC power from the two sets of power conversion systems to a load or the like. In this case, it is preferable to install two current detectors on the same power line so as not to complicate the construction.

  However, if two current detectors are installed on the same power line, two sets of power conversion systems independently control the discharge power of the storage battery based on the same current detection value, so that hunting occurs in the power flowing through the power line. there is a possibility.

  In addition, it is possible to improve controllability by branching power lines from the power system and connecting them to two sets of power conversion systems, and providing a current detector and a load on each of the two branched power lines. However, construction is complicated.

  This invention is made | formed in view of such a condition, The objective is to provide the technique which can improve the controllability of a reverse power flow, without making construction complicated.

  In order to solve the above-described problem, a power conversion system according to an aspect of the present invention converts discharge power of a first power storage device into AC power, and converts the AC power to a load connected to a power system via a power line. A first power converter to be supplied; a second power converter for converting the discharge power of the second power storage device to AC power; supplying the AC power to the load; and a first current for detecting a current flowing through the power line. A detector and a second current detector for detecting a current flowing through the power line, wherein the first power converter is detected by the first current detector during discharge of the first power storage device. When the power of the power line based on the current changes from the target value, the discharge power of the first power storage device is controlled so that the power of the power line approaches the target value during a predetermined first period, and the second The power converter is the second power storage device When the power of the power line based on the current detected by the second current detector is changed from the target value during discharging, the power of the power line becomes the target value after the first period has elapsed. The discharge power of the second power storage device is controlled to approach.

  Moreover, the control method of the power conversion system according to another aspect of the present invention converts the discharge power of the first power storage device into AC power, and supplies the AC power to a load connected to the power system via the power line. A first power conversion device; a second power conversion device that converts discharge power of the second power storage device into AC power and supplies the AC power to the load; and a first current detector that detects a current flowing through the power line. And a second current detector for detecting a current flowing through the power line, wherein the current detected by the first current detector during discharge of the first power storage device A first step of controlling the discharge power of the first power storage device so that the power of the power line approaches the target value during a predetermined first period when the power of the power line based on Discharging the second power storage device When the power of the power line based on the current detected by the second current detector changes from the target value, the power of the power line approaches the target value after the first period has elapsed. A second step of controlling the discharge power of the second power storage device.

  A program according to another aspect of the present invention is a first power conversion device that converts discharge power of a first power storage device into AC power and supplies the AC power to a load connected to a power system via a power line. A second power conversion device that converts discharge power of the second power storage device into AC power and supplies the AC power to the load, a first current detector that detects a current flowing through the power line, and a power line And a second current detector for detecting a flowing current, wherein the power line is based on the current detected by the first current detector during discharge of the first power storage device. Controlling the discharge power of the first power storage device so that the power of the power line approaches the target value during a predetermined first period when the power of the first power converter changes from the target value. Compu When the power of the power line based on the current detected by the second current detector changes from the target value during the discharge of the second power storage device, the first period has elapsed. To causing the computer of the second power converter to execute the step of controlling the discharge power of the second power storage device so that the power of the power line approaches the target value.

  According to the present invention, controllability of reverse power flow can be improved without complicating construction.

It is a block diagram which shows the structure of the power conversion system which concerns on 1st Embodiment. 2A is a diagram showing a time change of the power of the power line in FIG. 1, and FIG. 2B is a diagram illustrating a discharge power of the first power storage device and a second power storage device corresponding to FIG. 2A. It is a figure which shows the time change of the discharge electric power of. It is a flowchart which shows the process of the 1st power converter device in which the 1st electrical storage apparatus of FIG. 1 is discharging. It is a flowchart which shows the process of the 2nd power converter device in which the 2nd electrical storage apparatus of FIG. 1 is discharging. Fig.5 (a) is a figure which shows the time change of the electric power of the power line which concerns on 3rd Embodiment, FIG.5 (b) shows the discharge electric power of the 1st electrical storage apparatus corresponding to Fig.5 (a), and FIG. It is a figure which shows the time change of the discharge electric power of a 2nd electrical storage apparatus.

(First embodiment)
FIG. 1 is a block diagram illustrating a configuration of a power conversion system 1 according to the first embodiment. The power conversion system 1 includes a first power generation device 11, a second power generation device 12, a first power storage device 21, a second power storage device 22, a first power conversion device 31, a second power conversion device 32, A distribution board 40, a first current detector CT1, a second current detector CT2, a load 50, a power line PL1, and a power system 60 are provided.

The 1st electric power generating apparatus 11 and the 2nd electric power generating apparatus 12 are solar cells, for example, generate electric power based on the energy of sunlight, and output direct-current power.
The first power storage device 21 and the second power storage device 22 include, for example, a lithium ion storage battery, a nickel hydride storage battery, a lead storage battery, an electric double layer capacitor, a lithium ion capacitor, or the like, and store power.

  When the generated power of the first power generation device 11 is relatively small, the first power conversion device 31 converts the generated power of the first power generation device 11 and the discharge power of the first power storage device 21 into alternating current power. The load 50 is supplied via the distribution board 40. Load 50 is also connected to power grid 60 via distribution board 40 and power line PL1. The first power conversion device 31 charges the grid interconnection and the first power storage device 21 with the generated power when the generated power of the first power generation device 11 is relatively large. The first power conversion device 31 can also charge the first power storage device 21 with the power of the power grid 60.

  When the generated power of the second power generation device 12 is relatively small, the second power conversion device 32 converts the generated power of the second power generation device 12 and the discharge power of the second power storage device 22 into AC power, and converts the AC power into the AC power. The load 50 is supplied via the distribution board 40. The second power conversion device 32 charges the grid interconnection and the second power storage device 22 with the generated power when the generated power of the second power generation device 21 is relatively large. The second power conversion device 32 can also charge the second power storage device 22 with the power of the power grid 60. In the following, attention is paid to grid interconnection by generated power and discharged power. The first power converter 31 and the second power converter 32 are also referred to as power conditioners.

Power line PL1 is located closer to power system 60 than load 50. The power flowing through the power line PL1 is defined as power P0.
The first current detector CT1 and the second current detector CT2 are installed on the same power line PL1. First current detector CT1 detects a current flowing through power line PL1. Second current detector CT2 detects a current flowing through power line PL1. The first current detector CT1 and the second current detector CT2 are, for example, current transformers (CT).

  The first power converter 31 and the second power converter 32 basically have the same configuration and can be set as a master device or a slave device. In the present embodiment, the first power conversion device 31 is set as a master device, and the second power conversion device 32 is set as a slave device. As will be described below, the control when the power P0 of the power line PL1 changes from the target value PT differs depending on whether it is set as the master device or the slave device.

  When the power P0 of the power line PL1 based on the current detected by the first current detector CT1 changes from the target value PT during the discharge of the first power storage device 21, the first power conversion device 31 has a predetermined first During the period T1, the discharge power of the first power storage device 21 is controlled so that the power P0 of the power line PL1 approaches the target value. The discharge power of the first power storage device 21 may be controlled by the first power storage device 21 according to the control signal transmitted from the first power conversion device 31 to the first power storage device 21, or the first power storage device 21 may The first power converter 31 itself may control the current flowing through the power converter 31.

The power P0 flowing backward to the power system 60 is a positive value, and the power P0 supplied from the power system 60 to the distribution board 40 is a negative value. That is, when the power P0 is positive, it indicates that power is being sold. When the power P0 is negative, it indicates that power purchase has occurred.
The target value PT is a negative value. Therefore, when the power P0 is equal to the target value PT, no reverse power flow has occurred, and the power P0 is supplied from the power system 60 to the load 50.

  When the reverse power flow continues for a predetermined maximum allowable period, for example, 0.5 seconds while the first power storage device 21 and the second power storage device 22 are discharging, it is necessary to stop the discharge operation of the first power storage device 21 and the second power storage device 22 There is. Therefore, the target value PT is set to be negative in consideration of the measurement error of the power P0. As a result, even if a relatively small change in the load 50 occurs, it is possible to prevent the reverse power flow from occurring frequently.

Specifically, the first power conversion device 31 causes the power P0 to approach the target value PT during the first period T1 when the power P0 becomes larger than the target value PT during the discharge of the first power storage device 21. The discharge power P1 of the first power storage device 21 is reduced as time elapses.
When the power P0 becomes smaller than the target value PT during the discharge of the first power storage device 21, the first power conversion device 31 causes the power P0 to approach the target value PT during the first period T1. The discharge power P1 of 21 is increased with time.

  When the power P0 of the power line PL1 based on the current detected by the second current detector CT2 changes from the target value PT during the discharge of the second power storage device 22, the second power conversion device 32 has a first period T1. , The discharge power of the second power storage device 22 is controlled so that the power P0 of the power line PL1 approaches the target value. The second power conversion device 32 controls the discharge power of the second power storage device 22 during a predetermined second period T2.

Specifically, when the power P0 becomes larger than the target value PT during the discharge of the second power storage device 22, the second power conversion device 32 sets the power P0 to the target value after the first period T1 has elapsed. The discharge power P2 of the second power storage device 22 is decreased with time so as to approach the PT.
In addition, when the power P0 becomes smaller than the target value PT during the discharge of the second power storage device 22, the second power conversion device 32 causes the power P0 to approach the target value PT after the first period T1 has elapsed. The discharge power P2 of the second power storage device 22 is increased as time elapses.

  The first power conversion device 31 includes a first timer (not shown) and measures the first period T1 and the second period T2 asynchronously with the second power conversion device 32. The second power conversion device 32 has a second timer (not shown) and counts the first period T1 and the second period T2 asynchronously with the first power conversion device 31. Therefore, it is not necessary to communicate by connecting the first power converter 31 and the second power converter 32 via a communication line or the like.

When the power P0 becomes substantially equal to the target value PT within the first period T1, the first power conversion device 31 stops the control of the discharge power of the first power storage device 21.
When the power P0 becomes substantially equal to the target value PT within the second period T2, the second power conversion device 32 stops the control of the discharge power of the second power storage device 22.

When the first period T1 and the second period T2 have elapsed and the power P0 is greater than the target value PT, the first power conversion device 31 stops the discharge of the first power storage device 21.
When the first period T1 and the second period T2 have elapsed and the power P0 is greater than the target value PT, the second power conversion device 32 stops the discharge of the second power storage device 22.

  At least a part of the first power conversion device 31 and the second power conversion device 32 can be realized by cooperation of hardware resources and software resources, or only hardware resources. As hardware resources, analog elements, microcomputers, DSPs, ROMs, RAMs, FPGAs, and other LSIs can be used. Firmware and other programs can be used as software resources.

  Next, the overall operation of the power conversion system 1 will be described. The following numerical values are examples for facilitating understanding, and are not limited thereto.

  FIG. 2A is a diagram showing a time change of the power P0 of the power line PL1 of FIG. FIG. 2B is a diagram illustrating a change over time of the discharge power P1 of the first power storage device 21 and the discharge power P2 of the second power storage device 22 corresponding to FIG. 2A.

  2A and 2B, the power generated by the first power generation device 11 and the second power generation device 12 is relatively small, and the first power storage device 21 and the second power storage device 22 are discharged in the initial state. The target value PT is, for example, -100W. The first period T1 and the second period T2 are each 200 milliseconds, for example.

  Until time t1, the electric power P0 is almost the target value PT. At time t1, the load 50 decreases, the power P0 becomes positive, and a reverse power flow occurs.

  The first power conversion device 31 decreases the discharge power P1 with time during the first period T1 from time t2 to time t4. As a result, the power P0 is reduced, but the reverse power flow is not eliminated. Here, the discharge power P1 is zero at time t3 before time t4.

  The second power conversion device 32 decreases the discharge power P2 with time during the second period T2 from time t4 to time t6. As a result, the electric power P0 decreases, and the electric power P0 substantially reaches the target value PT at time t5 before time t6. Therefore, after time t5, the discharge power P2 maintains the value at time t5.

  In this way, before the reverse power flow continues for 0.5 seconds, the reverse power flow can be eliminated and the power P0 can be substantially set to the target value PT.

  FIG. 3 is a flowchart showing processing of the first power conversion device 31 during discharge of the first power storage device 21 of FIG. The following processing is performed by the first power conversion device 31.

  First, the power P0 of the power line PL1 is measured based on the current detected by the first current detector CT1 (S101), and it is determined whether the fluctuation occurrence counter is 0 or less (S102). The initial value of the fluctuation occurrence counter is zero. When the fluctuation occurrence counter is 0 or less (Y in S102), it is determined whether the power P0 has changed by a predetermined value or more from the value 10 milliseconds before (S103). The predetermined value is not particularly limited, but is 10 W, for example. If the power P0 has not changed (N in S103), the process proceeds to S106. When the power P0 changes (Y in S103), the fluctuation occurrence counter is set to 40 (S104), and the process proceeds to S106.

  On the other hand, if the fluctuation occurrence counter is not less than or equal to 0 in S102 (N in S102), the fluctuation occurrence counter is decremented by 1 (S105), and the process proceeds to S106.

  Next, the power P0 is compared with the target value PT (S106). When the power P0 and the target value PT are substantially equal (P0≈PT), the power sale counter is set to 0 (S107), the first timer is used to wait 10 milliseconds (S108), and the process returns to S101.

  When the power P0 is larger than the target value PT in S106 (P0> PT), that is, when there is too little power purchase or reverse power flow (power sale) occurs, the power sale counter is incremented by 1 (S109), Is greater than 45 (S110). When the power sale counter is greater than 45 (Y in S110), since the 450 milliseconds or more have elapsed since the occurrence of the reverse power flow, the discharging operation of the first power storage device 21 is stopped (S111).

  If the power sale counter is 45 or less (N in S110), it is determined whether the fluctuation occurrence counter is greater than 20 (S112). When the fluctuation occurrence counter is larger than 20 (Y in S112), the discharge power P1 of the first power storage device 21 is reduced by α (W) (S113), and the process proceeds to S108. When the fluctuation occurrence counter is 20 or less (N in S112), the process proceeds to S108. Thus, the discharge power P1 is reduced during the first period T1, and thereafter the discharge power P1 is not reduced.

  If the power P0 is smaller than the target value PT in S106 (P0 <PT), that is, if there is too much power purchase, the power sale counter is set to 0 (S114), and it is determined whether the fluctuation occurrence counter is greater than 20 ( S115). When the fluctuation occurrence counter is larger than 20 (Y in S115), the discharge power P1 of the first power storage device 21 is increased by α (W) (S116), and the process proceeds to S108. When the fluctuation occurrence counter is 20 or less (N in S115), the process proceeds to S108. Thus, the discharge power P1 is increased during the first period T1, and thereafter the discharge power P1 is not increased.

  FIG. 4 is a flowchart showing processing of the second power conversion device 32 during discharge of the second power storage device 22 of FIG. In FIG. 4, the processes of S201 to S210 and S214 correspond to the processes of S101 to S110 and S114 of FIG. 3 and are the same except that they are performed by the second power conversion device 32, and thus description thereof will be omitted. Below, it demonstrates centering on a different point from the process of FIG.

  In S211, the discharge operation of the second power storage device 22 is stopped. In S212, when the fluctuation occurrence counter is larger than 20 (Y in S212), the process proceeds to S208. When the fluctuation occurrence counter is 20 or less (N in S212), the discharge power P2 of the second power storage device 22 is reduced by α (W) (S213), and the process proceeds to S208. Thus, the discharge power P2 is not reduced during the first period T1, but the discharge power P2 is reduced during the second period T2.

  In S215, when the fluctuation occurrence counter is larger than 20 (Y in S215), the process proceeds to S208. When the fluctuation occurrence counter is 20 or less (N in S215), the discharge power P2 of the second power storage device 22 is increased by α (W) (S216), and the process proceeds to S208. Thereby, the discharge power P2 is not increased during the first period T1, and the discharge power P2 is increased during the second period T2.

  By changing the values of S110, S112, S115, S210, S212, and S215, the time until the discharge operation is stopped, the first period T1, and the second period T2 can be appropriately changed.

  As described above, according to the present embodiment, when the power P0 changes from the target value PT during the discharge of the first power storage device 21, the discharge power P1 of the first power storage device 21 during the first period T1. To control. Further, when the power P0 changes from the target value PT during the discharge of the second power storage device 22, the discharge power P2 of the second power storage device 22 is controlled after the first period T1 has elapsed. That is, the control of the discharge power P1 by the first power converter 31 and the control of the discharge power P2 by the second power converter 32 are performed in different periods. Thereby, even if the first current detector CT1 and the second current detector CT2 are installed on the same power line PL1, it is difficult to generate hunting of the power P0. Therefore, the controllability of the reverse power flow can be improved without complicating the construction.

  Moreover, since the 2nd power converter device 32 time-measures 1st period T1 and 2nd period T2 asynchronously with the 1st power converter device 31, it is between the 1st power converter device 31 and the 2nd power converter device 32. There is no need to provide a communication line for synchronization. Therefore, the 1st power converter device 31 and the 2nd power converter device 32 can be installed easily, and restrictions on an installation position can be decreased.

(Second Embodiment)
In the first embodiment, the first power conversion device 31 controls the discharge power P1 first, and then the second power conversion device 32 controls the discharge power P2. In the second embodiment, the control is periodically performed. Change the order of. Below, it demonstrates centering around difference with 1st Embodiment.

  Specifically, every time a predetermined replacement period elapses, the order of the control of the discharge power P1 of the first power storage device 21 and the control of the discharge power P2 of the second power storage device 22 are switched. That is, every time the replacement period elapses, the master device and the slave device are switched. When the replacement period elapses in the configuration of the first embodiment, the second power conversion device 32 becomes a master device, and the first power conversion device 31 becomes a slave device. Thus, the second power conversion device 32 controls the discharge power of the second power storage device 22 during the first period T1 when the power P0 changes from the target value PT during the discharge of the second power storage device 22. . When the electric power P0 changes from the target value PT during the discharge of the first power storage device 21, the first power conversion device 31 performs the first power storage device during the second period T2 after the first period T1 has elapsed. 21 discharge power is controlled.

  The replacement period is longer than the sum of the first period T1 and the second period T2. The replacement period is not particularly limited, and may be, for example, several days, one week, one month, or one year.

  Such switching of the order of control may be performed by an operator, or each of the first power conversion device 31 and the second power conversion device 32 may automatically perform the replacement period with a timer. . When switching automatically, it is preferable to switch at night, for example. The reason is that, in many cases, the first power storage device 21 and the second power storage device 22 are not discharged at night, so that an error occurs between the timers of the first power conversion device 31 and the second power conversion device 32. This is because there is little influence even when the timing of setting as a master device occurs.

  In the first embodiment, since the first power conversion device 31 controls the discharge power P1 first, when a reverse power flow occurs, the first power storage device 21 as described with reference to FIGS. 2 (a) and 2 (b). The discharge power P1 is controlled to zero, and the power P0 may become substantially equal to the target value PT during the control of the second power converter 32. Thereafter, the first power storage device 21 does not discharge and the second power storage device 22 continues to discharge, so the discharge frequency of the second power storage device 22 may be higher than the discharge frequency of the first power storage device 21.

  According to the present embodiment, since the order of the control of the discharge power P1 of the first power storage device 21 and the control of the discharge power P2 of the second power storage device 22 are periodically switched, the discharge frequency of the first power storage device 21 and the first 2 The discharge frequency of the power storage device 22 can be made closer. Therefore, the lifetime of the 1st electrical storage apparatus 21 and the 2nd electrical storage apparatus 22 can be approximated, and it can avoid that the lifetime of either one is shortened significantly.

  For example, when the replacement period is one year, the generated power by sunlight is relatively small, and the grid connection by generated power and discharge power is performed at a relatively high frequency, for example, in winter or when there is a lot of cloudiness. The power storage device with the higher discharge frequency can be replaced every year. Therefore, the discharge frequency of the first power storage device 21 and the discharge frequency of the second power storage device 22 can be effectively brought close to each other.

(Third embodiment)
In the third embodiment, when the power P0 is different from the target value PT when the first period T1 and the second period T2 have elapsed, the discharge power P1 of the first power storage device 21 and the discharge power of the second power storage device 22 It differs from the first embodiment in that both of P2 are decreased simultaneously. Below, it demonstrates centering around difference with 1st Embodiment.

  If the power P0 of the power line PL1 is different from the target value PT when the first period T1 and the second period T2 have elapsed, the first power conversion device 31 sets the power P0 to the target value PT during the third period T3. The discharge power P1 of the first power storage device 21 is controlled so as to approach.

  If the power P0 of the power line PL1 is different from the target value PT when the first period T1 and the second period T2 have elapsed, the second power converter 32 sets the power P0 to the target value PT during the third period T3. The discharge power P2 of the second power storage device 22 is controlled so as to approach.

When the third period T3 has elapsed and the power P0 is greater than the target value PT, the first power conversion device 31 stops discharging the first power storage device 21.
When the third period T3 has elapsed and the power P0 is greater than the target value PT, the second power conversion device 32 stops discharging the second power storage device 22.

  In the third period T3, a period obtained by subtracting the first period T1 and the second period T2 from the maximum allowable period of reverse flow can be set as the maximum value. In the numerical example of the first embodiment, the third period T3 may be, for example, 50 milliseconds.

  Fig.5 (a) is a figure which shows the time change of the electric power P0 of the electric power line PL1 which concerns on 3rd Embodiment. FIG. 5B is a diagram illustrating a change over time of the discharge power P1 of the first power storage device 21 and the discharge power P2 of the second power storage device 22 corresponding to FIG. 5A.

Until time t11, the electric power P0 is almost the target value PT. At time t11, compared with the example of FIG. 2A, the load 50 is further reduced and a larger reverse power flow is generated.
The first power conversion device 31 decreases the discharge power P1 with the passage of time during the first period T1 from time t12 to time t13. As a result, the power P0 is reduced, but the reverse power flow is not eliminated.

  The second power conversion device 32 decreases the discharge power P2 with the passage of time during the second period T2 from time t13 to time t14. As a result, the power P0 is reduced, but the reverse power flow is not eliminated.

  The first power conversion device 31 decreases the discharge power P1 with time during the third period T3 from time t14 to time t16. At the same time, the second power conversion device 32 also decreases the discharge power P2 with time. At time t15 prior to time t16, the power P0 becomes substantially the target value PT. Since the discharge powers P1 and P2 are controlled simultaneously, hunting may occur in the power P0, but there is a possibility that the reverse power flow can be eliminated before the reverse power flow continues for 0.5 seconds.

According to the present embodiment, it is possible to cope with a case where a relatively large load change occurs and a reverse power flow remains when the first period T1 and the second period T2 have elapsed.
Further, if the load 50 fluctuates so that the reverse power flow is eliminated before the first period T1 and the second period T2 elapse, it is difficult to generate hunting of the electric power P0 as in the first embodiment.

  Note that the third embodiment may be combined with the second embodiment.

(Fourth embodiment)
The fourth embodiment differs from the first embodiment in that a waiting time is provided between the first period T1 and the second period T2. Below, it demonstrates centering around difference with 1st Embodiment.

  The second power conversion device 32 controls the discharge power P2 of the second power storage device 22 when a predetermined waiting time has elapsed from the elapse of the first period T1. The waiting time can be set as a maximum value by subtracting the first period T1 and the second period T2 from the maximum allowable period of reverse flow. In the numerical example of the first embodiment, the waiting time may be set to 10 to 50 milliseconds, for example.

  According to the present embodiment, even when the first power conversion device 31 is asynchronous with the second power conversion device 32, the discharge power of the first power storage device 21 and the discharge power of the second power storage device 22 can be hardly controlled simultaneously. When there is a period in which the discharge power is controlled simultaneously, hunting may occur when the power P0 is near the target value PT during this period. However, in this embodiment, such hunting can also be suppressed.

  Note that the fourth embodiment may be combined with the second or third embodiment.

  In the above, this invention was demonstrated based on the Example. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications can be made to the respective components or combinations of the respective treatment processes, and such modifications are also within the scope of the present invention. is there.

  The embodiment may be specified by the following items.

[Item 1]
The first power conversion device that converts the discharge power of the first power storage device (21) into AC power and supplies the AC power to the load (50) connected to the power system (60) via the power line (PL1). (31),
A second power converter (32) that converts the discharge power of the second power storage device (22) into AC power and supplies the AC power to the load (50);
A first current detector (CT1) for detecting a current flowing in the power line (PL1);
A second current detector (CT2) for detecting a current flowing through the power line (PL1),
In the first power converter (31), the power of the power line (PL1) based on the current detected by the first current detector (CT1) during the discharge of the first power storage device (21) is a target value. When the electric power of the first power storage device (21) is controlled so that the electric power of the power line (PL1) approaches the target value during a predetermined first period,
In the second power conversion device (32), during the discharge of the second power storage device (22), the power of the power line (PL1) based on the current detected by the second current detector (CT2) is the target. When changing from a value, the discharge power of the second power storage device (22) is controlled so that the power of the power line (PL1) approaches the target value after the first period has elapsed. Power conversion system (1).
[Item 2]
The power flowing backward to the power system (60) is a positive value, the target value is a negative value,
When the electric power of the power line (PL1) becomes larger than the target value during the discharging of the first power storage device (21), the first power conversion device (31) is configured to output the power line during the first period. Decreasing the discharge power of the first power storage device (21) with time so that the power of (PL1) approaches the target value,
When the power of the power line (PL1) becomes larger than the target value during the discharging of the second power storage device (22), the second power conversion device (32) has passed after the first period has elapsed. The power conversion system (1) according to item 1, wherein the discharge power of the second power storage device (22) is decreased with time so that the power of the power line (PL1) approaches the target value. .
[Item 3]
When the power of the power line (PL1) becomes smaller than the target value during the discharging of the first power storage device (21), the first power conversion device (31) is configured to output the power line during the first period. Increasing the discharge power of the first power storage device (21) with time so that the power of (PL1) approaches the target value,
When the power of the power line (PL1) becomes smaller than the target value during the discharge of the second power storage device (22), the second power conversion device (32) has passed after the first period has elapsed. The power conversion system (1) according to item 2, wherein the discharge power of the second power storage device (22) is increased with time so that the power of the power line (PL1) approaches the target value. .
[Item 4]
From the item 1, wherein the order of the control of the discharge power of the first power storage device (21) and the control of the discharge power of the second power storage device (22) is switched every time the predetermined replacement period elapses. 4. The power conversion system (1) according to any one of 3 above.
[Item 5]
The second power conversion device (32) controls the discharge power of the second power storage device (22) during a predetermined second period,
When the power of the power line (PL1) is different from the target value when the first period and the second period have elapsed, the first power conversion device (31) has the power of the power line (PL1) Controlling the discharge power of the first power storage device (21) so as to approach the target value;
When the power of the power line (PL1) is different from the target value when the first period and the second period have elapsed, the second power conversion device (32) has the power of the power line (PL1) The power conversion system (1) according to any one of items 1 to 4, wherein the discharge power of the second power storage device (22) is controlled so as to approach a target value.
[Item 6]
The second power conversion device (32) controls the discharge power of the second power storage device (22) when a predetermined waiting time has elapsed from the elapse of the first period. The power conversion system (1) according to any one of the above.
[Item 7]
The power conversion system according to any one of items 1 to 6, wherein the second power conversion device (32) measures the first period asynchronously with the first power conversion device (31). (1).
[Item 8]
The first power conversion device that converts the discharge power of the first power storage device (21) into AC power and supplies the AC power to the load (50) connected to the power system (60) via the power line (PL1). (31), the second power conversion device (32) for converting the discharge power of the second power storage device (22) to AC power, and supplying the AC power to the load (50), and the power line (PL1) A control method for a power conversion system (1) comprising: a first current detector (CT1) for detecting a flowing current; and a second current detector (CT2) for detecting a current flowing in the power line (PL1). ,
When the power of the power line (PL1) based on the current detected by the first current detector (CT1) changes from a target value during the discharge of the first power storage device (21), a predetermined first period A first step of controlling the discharge power of the first power storage device (21) so that the power of the power line (PL1) approaches the target value during
When the power of the power line (PL1) based on the current detected by the second current detector (CT2) changes from the target value during the discharge of the second power storage device (22), the first period A second step of controlling the discharge power of the second power storage device (22) so that the power of the power line (PL1) approaches the target value after elapse of
A method for controlling the power conversion system (1), comprising:
[Item 9]
The first power conversion device that converts the discharge power of the first power storage device (21) into AC power and supplies the AC power to the load (50) connected to the power system (60) via the power line (PL1). (31), the second power conversion device (32) for converting the discharge power of the second power storage device (22) to AC power, and supplying the AC power to the load (50), and the power line (PL1) A program used in a power conversion system (1) including a first current detector (CT1) for detecting a flowing current and a second current detector (CT2) for detecting a current flowing in the power line (PL1). And
When the power of the power line (PL1) based on the current detected by the first current detector (CT1) changes from a target value during the discharge of the first power storage device (21), a predetermined first period During which the computer of the first power converter (31) executes the step of controlling the discharge power of the first power storage device (21) so that the power of the power line (PL1) approaches the target value,
When the power of the power line (PL1) based on the current detected by the second current detector (CT2) changes from the target value during the discharge of the second power storage device (22), the first period After the elapse of time, the step of controlling the discharge power of the second power storage device (22) so that the power of the power line (PL1) approaches the target value is executed in the computer of the second power conversion device (32) A program characterized by letting

DESCRIPTION OF SYMBOLS 1 ... Power conversion system, 11 ... 1st power generator, 12 ... 2nd power generator, 21 ... 1st electrical storage apparatus, 22 ... 2nd electrical storage apparatus, 31 ... 1st power converter, 32 ... 2nd power converter, 50 ... Load, 60 ... Power system, PL1 ... Power line, CT1 ... First current detector, CT2 ... Second current detector.

Claims (9)

A first power conversion device that converts discharge power of the first power storage device into AC power, and supplies the AC power to a load connected to the power system via a power line;
A second power conversion device that converts discharge power of the second power storage device into AC power and supplies the AC power to the load;
A first current detector for detecting a current flowing in the power line;
A second current detector for detecting a current flowing in the power line,
When the power of the power line based on the current detected by the first current detector is changed from a target value during the discharging of the first power storage device, the first power conversion device has a predetermined first period. And controlling the discharge power of the first power storage device so that the power of the power line approaches the target value,
When the power of the power line based on the current detected by the second current detector is changed from the target value during the discharging of the second power storage device, the second power conversion device determines that the first period is After the elapse of time, the power conversion system controls the discharge power of the second power storage device so that the power of the power line approaches the target value. The power flowing backward to the power system is a positive value, the target value is a negative value,
The first power conversion device causes the power of the power line to approach the target value during the first period when the power of the power line becomes larger than the target value during discharging of the first power storage device. Reducing the discharge power of the first power storage device over time,
When the power of the power line becomes larger than the target value during the discharge of the second power storage device, the second power conversion device causes the power of the power line to reach the target value after the first period has elapsed. 2. The power conversion system according to claim 1, wherein the discharge power of the second power storage device is reduced with the passage of time so as to approach the value of 2. In the first power conversion device, when the power of the power line becomes smaller than the target value during discharging of the first power storage device, the power of the power line approaches the target value during the first period. Increasing the discharge power of the first power storage device over time,
In the second power conversion device, when the power of the power line becomes smaller than the target value during the discharge of the second power storage device, the power of the power line becomes the target value after the first period has elapsed. 3. The power conversion system according to claim 2, wherein discharge power of the second power storage device is increased with time so as to approach the value of 3.   The order of the control of the discharge power of the first power storage device and the control of the discharge power of the second power storage device are switched every time the predetermined replacement period elapses. The power conversion system according to item. The second power conversion device controls the discharge power of the second power storage device during a predetermined second period,
When the power of the power line is different from the target value when the first period and the second period have elapsed, the first power conversion device causes the first power storage device so that the power of the power line approaches the target value. Control the discharge power of the device,
When the power of the power line is different from the target value when the first period and the second period have elapsed, the second power conversion device causes the second power storage device so that the power of the power line approaches the target value. The power conversion system according to any one of claims 1 to 4, wherein discharge power of the device is controlled.   The said 2nd power converter device controls the discharge electric power of a said 2nd electrical storage apparatus, when predetermined | prescribed waiting time passes since progress of the said 1st period. The power conversion system described in 1.   The power conversion system according to any one of claims 1 to 6, wherein the second power conversion device times the first period asynchronously with the first power conversion device. The first power conversion device that converts the discharge power of the first power storage device into AC power and supplies the AC power to a load connected to the power system via the power line, and the discharge power of the second power storage device is AC power A second power converter that converts the power into the load, a first current detector that detects a current that flows through the power line, a second current detector that detects a current that flows through the power line, A method for controlling a power conversion system comprising:
When the power of the power line based on the current detected by the first current detector is changed from a target value during the discharge of the first power storage device, the power of the power line is changed during the predetermined first period. A first step of controlling the discharge power of the first power storage device so as to approach a target value;
When the power of the power line based on the current detected by the second current detector changes from the target value during the discharging of the second power storage device, the power line A second step of controlling the discharge power of the second power storage device so that the power approaches the target value;
A control method for a power conversion system, comprising: The first power conversion device that converts the discharge power of the first power storage device into AC power and supplies the AC power to a load connected to the power system via the power line, and the discharge power of the second power storage device is AC power A second power converter that converts the power into the load, a first current detector that detects a current that flows through the power line, a second current detector that detects a current that flows through the power line, A program used in a power conversion system comprising:
When the power of the power line based on the current detected by the first current detector is changed from a target value during the discharge of the first power storage device, the power of the power line is changed during the predetermined first period. Causing the computer of the first power converter to execute the step of controlling the discharge power of the first power storage device so as to approach the target value;
When the power of the power line based on the current detected by the second current detector changes from the target value during the discharging of the second power storage device, the power line The program which makes the computer of a said 2nd power converter device perform the step which controls the discharge electric power of a said 2nd electrical storage apparatus so that electric power approaches the said target value.

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