Power system

Abstract

To provide a power system capable of reducing that output power is unnecessarily suppressed when system overvoltage occurs and a voltage rise suppression function operates.SOLUTION: A power system S1 includes: a plurality of power conversion devices A1 each of which can allow reverse power flow to a power system D; and a detection unit 12 which monitors system voltage of the power system D and detects whether system voltage is system overvoltage which is equal to or exceeds an overvoltage level. Each power conversion device A1 includes an output control unit 13 which has a voltage rise suppression function and controls output power to a power system D side. The voltage rise suppression function includes a phase advance operation control function and an output suppression function. In each power conversion device A1, the output control unit 13 performs the phase advance operation control function when any of the detection unit 12 in the plurality of power conversion devices A1 detects system overvoltage, and performs the output suppression function when system voltage does not fall below a function stop level for determining elimination of system overvoltage even if the phase advance operation control function is performed.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to power systems. [Background technology]

[0002] In recent years, power systems that are connected to a power grid and capable of reverse power flow to the power grid have become known. For example, Patent Document 1 discloses a solar power generation system, which is an example of a power system. The solar power generation system described in Patent Document 1 includes a plurality of power conditioners. A plurality of solar cells are individually connected to each of the plurality of power conditioners. Each of the plurality of power conditioners converts DC power output by the solar cells into AC power of a predetermined frequency (e.g., commercial power frequency), and supplies power to a load facility connected to the AC grid or to the power grid.

[0003] Furthermore, conventional power conditioners incorporate a function (voltage rise suppression function) for suppressing the system voltage when a system overvoltage occurs so that the system voltage does not exceed a preset appropriate voltage. This voltage rise suppression function is specified in Non-Patent Document 1, "General Rules for Test Methods of Low-Voltage System Interconnection Protection Devices, etc.", and includes, for example, a function for controlling the power factor of the output power (leading-phase reactive power control function) and a function for suppressing the output power (output control function). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2012-205322 A [Non-patent literature]

[0005] [Non-Patent Document 1] General Rules for Test Methods for Low-Voltage Grid-Interconnection Protection Devices, etc. (JETGR00002-1-15.0(2022)) Summary of the Invention [Problem to be solved by the invention]

[0006] In a power system having a plurality of power conversion devices (power conditioners), in a configuration in which each power conversion device detects an overvoltage of the grid voltage individually and executes the voltage rise suppression function, for example, due to variations in the detection accuracy of the grid voltage detected by each power conversion device, only a power conversion device with a large detection error may detect an overvoltage. In this case, there is a risk that the voltage rise suppression function will operate only in one power conversion device, and the output power will be suppressed to 0% by the output suppression function before the other power conversion devices detect the overvoltage.

[0007] The present disclosure has been devised in consideration of the above circumstances, and has a purpose to provide a power system that can reduce unnecessary suppression of output power when a grid overvoltage occurs and a voltage rise suppression function is activated. [Means for solving the problem]

[0008] The power system provided by the present disclosure comprises a plurality of power conversion devices, each capable of reverse power flow to a power grid, and a detection unit that monitors the system voltage of the power grid and detects whether the system voltage is a system overvoltage that is equal to or higher than an overvoltage level, each of the plurality of power conversion devices includes an output control unit that has a voltage rise suppression function and controls the output power to the power grid, and the voltage rise suppression function includes a leading phase operation control function that changes the power factor of the output power in a leading direction as viewed from the output control unit, and an output suppression function that suppresses the output power, and in each of the plurality of power conversion devices, when the detection unit detects the system overvoltage, the output control unit executes the voltage rise suppression function, and in executing the voltage rise suppression function, executes the leading phase operation control function, and if the system voltage does not become less than a function shutdown level for determining the elimination of the system overvoltage even after executing the leading phase operation control function, executes the output suppression function.

[0009] In a preferred embodiment of the power system, the detection unit is provided in each of the multiple power conversion devices, and in each of the multiple power conversion devices, the corresponding detection unit monitors the output end voltage of the corresponding power conversion device on the power system side as the system voltage, and when the corresponding detection unit of each of the multiple power conversion devices detects the system overvoltage, the output control unit executes the voltage rise suppression function while transmitting an overvoltage detection signal indicating the occurrence of the system overvoltage to each of the other power conversion devices, and in each of the other power conversion devices, the output control unit executes the voltage rise suppression function upon receiving the overvoltage detection signal.

[0010] In a preferred embodiment of the power system, the multiple power conversion devices include a first power conversion device which is a master device and at least one second power conversion device which is a slave device, the detection unit is provided in the first power conversion device and monitors the output end voltage of the first power conversion device on the power grid side as the grid voltage, and when the detection unit of the first power conversion device detects the grid overvoltage, the first power conversion device transmits an overvoltage detection signal indicating the occurrence of the grid overvoltage to each of the at least one second power conversion device while executing the voltage rise suppression function by the output control unit, and in each of the at least one second power conversion device, the output control unit executes the voltage rise suppression function upon receiving the overvoltage detection signal.

[0011] In a preferred embodiment of the power system, the power system further includes a detection device that is provided separately from each of the plurality of power conversion devices and includes the detection unit, and when the detection unit detects the system overvoltage, the detection device transmits an overvoltage detection signal indicating the occurrence of the system overvoltage to each of the plurality of power conversion devices, and in each of the plurality of power conversion devices, the output control unit executes the voltage rise suppression function upon receiving the overvoltage detection signal. Effect of the Invention

[0012] According to the power system of the present disclosure, in each power conversion device, the output control unit executes a voltage rise suppression function when the detection unit detects a grid overvoltage. At this time, in executing the voltage rise suppression function, the output control unit first executes a leading phase operation control function, and executes an output suppression function if the grid voltage does not become less than a function stop level that is equal to or lower than the overvoltage level even after executing the leading phase operation control function. According to this configuration, the detection of a grid overvoltage by the detection unit triggers the execution of the leading phase operation control function in all of the multiple power conversion devices. Therefore, by executing the leading phase operation suppression function in all of the multiple power conversion devices, the possibility of suppressing the grid overvoltage is increased, and therefore it is possible to suppress the execution of unnecessary output suppression functions. In other words, the power system of the present disclosure can reduce unnecessary suppression of output power when a grid overvoltage occurs and the voltage rise suppression function is activated. [Brief description of the drawings]

[0013] [Figure 1] 1 is a diagram illustrating an example of the overall configuration of a power system according to a first embodiment. [Diagram 2] 5 is a flowchart showing control performed by each power electronics device in an overvoltage suppression process of the power system according to the first embodiment. [Diagram 3] FIG. 11 is a diagram illustrating an example of the overall configuration of a power system according to a second embodiment. [Figure 4] 10 is a flowchart showing control performed by a first power conversion device in an overvoltage suppression process of a power system according to a second embodiment. [Diagram 5] 10 is a flowchart showing control performed by each second power electronics device in an overvoltage suppression process of a power system according to a second embodiment. [Figure 6] FIG. 11 is a diagram illustrating an example of the overall configuration of a power system according to a third embodiment. [Figure 7] 13 is a flowchart showing control performed by a detection device in an overvoltage suppression process of a power system according to a third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the power system of the present disclosure will be described below with reference to the drawings. In the following, identical or similar components are designated by the same reference numerals and duplicated descriptions will be omitted.

[0015] FIG. 1 shows a power system S1 according to a first embodiment. The power system S1 is connected to a power system D. In order to keep the voltage of the power system D (hereinafter referred to as "system voltage") within an appropriate range, the power system S1 detects an overvoltage of the system voltage (hereinafter referred to as "system overvoltage"), and performs an overvoltage suppression process when the power system S1 detects a system overvoltage. The power system S1 includes a plurality of power conversion devices A1. Unlike the example shown in FIG. 1, the power system S1 may further include a load.

[0016] Each of the multiple power electronics devices A1 is connected to the power system D via a connection point K. Each of the multiple power electronics devices A1 is capable of outputting power to the power system D. Thus, the power system S1 is capable of reverse power flow to the power system D.

[0017] A power device X is connected to each of the multiple power conversion devices A1. Each power device X is, for example, a solar cell, a storage battery, a generator, etc. Specific examples of the power device X are not limited to these. The power conversion device A1 to which a solar cell is connected as the power device X is a power conditioner for photovoltaic power generation, and controls the power generated by the solar cell. The power conversion device A1 to which a storage battery is connected as the power device X is a power conditioner for the storage battery, and controls the charging power and discharging power of the storage battery. The power conversion device A1 to which a generator is connected as the power device X is a generator control device, and controls the power generated by the generator. The generator is a device that generates power using fuel, hydroelectric power, or wind power.

[0018] Each of the multiple power electronics devices A1 executes a voltage rise suppression function in the overvoltage suppression process of the power system S1. Each of the multiple power electronics devices A1 includes a communication unit 11, a detection unit 12, and an output control unit 13. The communication unit 11, the detection unit 12, and the output control unit 13 described below are common to each of the power electronics devices A1 unless otherwise specified.

[0019] The communication unit 11 communicates with other power electronics devices A1. The communication may be wireless communication or wired communication.

[0020] The detection unit 12 is installed on a power line 90 connecting the connection point K and the output control unit 13. The detection unit 12 monitors the output end voltage of the corresponding power conversion device A1 on the power system D side as a system voltage. Each power conversion device A1 is connected in parallel, and the system voltage of the power system D and the above-mentioned output end voltage are the same. The detection unit 12 monitors the system voltage of the power system D and detects whether or not there is a system overvoltage. Whether or not there is a system overvoltage is determined based on whether or not the system voltage is equal to or higher than an overvoltage level. The overvoltage level is, for example, a value (set value) specified in "General Rules for Test Methods of Low-Voltage System Interconnection Protection Devices, etc." in Non-Patent Document 1, but may be a value specified by other rules or standards (for example, JIS: Japanese Industrial Standards). The overvoltage level is, for example, instructed by a power company, but may be set in advance. The detection unit 12 detects a system overvoltage when the system voltage is equal to or higher than the overvoltage level, and does not detect a system overvoltage when the system voltage is lower than the overvoltage level. When the detection unit 12 detects a system overvoltage, it outputs an overvoltage detection signal to the output control unit 13 and transmits it to each of the other power electronics devices A1 via the communication unit 11. The transmitted overvoltage detection signal is received by the communication unit 11 in the other power electronics devices A1 and output to the output control unit 13. Furthermore, if there is no system overvoltage, the detection unit 12 does not output or transmit the overvoltage detection signal.

[0021] After detecting a grid overvoltage, the detection unit 12 determines whether the grid overvoltage has been resolved based on whether the grid voltage has become less than the malfunction level. The malfunction level is a value for determining whether the grid overvoltage has been resolved, and is, for example, the same as the overvoltage level. Unlike this example, the malfunction level may be a value lower than the overvoltage level. If the malfunction level is set to a value lower than the overvoltage level, it is possible to prevent repeated switching between the determination of the occurrence of a grid overvoltage and the resolution of the grid overvoltage. When the grid overvoltage is resolved, the detection unit 12 cancels (stops) the output and transmission of the overvoltage detection signal.

[0022] The output control unit 13 is connected to a corresponding power device X and controls the power device X. The output control unit 13 converts the power input from the power device X into power in the power system D and outputs the power. In this power conversion, the output control unit 13 controls the output power to the power system D side.

[0023] In the overvoltage suppression process performed by the power system S1, the output control unit 13 executes a voltage rise suppression function. The voltage rise suppression function is a function for maintaining the system voltage of the power system D within an appropriate range and preventing failures and shortening of the lifespan of loads (such as electrical appliances). In other words, the output control unit 13 uses the voltage rise suppression function to control the output power so that the system voltage of the power system D falls within the appropriate range. When an overvoltage detection signal is input from the detection unit 12 or the communication unit 11, the output control unit 13 executes the voltage rise suppression function.

[0024] The voltage rise suppression function includes a leading phase operation control function and an output suppression function. In the leading phase operation control function, the power factor of the output power is changed in a leading direction as viewed from the corresponding output control unit 13. In the leading phase operation control function, the change in the power factor suppresses the rise in the system voltage. The leading phase operation control function corresponds to the leading phase reactive power control function in Non-Patent Document 1. When the output control unit 13 executes the leading phase operation control function, the output control unit 13 changes the power factor of the output power stepwise or linearly over time to a set power factor (e.g., 85%). In the output suppression function, the output power is suppressed. In the output suppression function, the increase in the system voltage is suppressed by suppressing the output power. The output suppression function corresponds to the output control function in Non-Patent Document 1. When the output control unit 13 executes the output suppression function, the output control unit 13 suppresses the output power stepwise or linearly over time to a set limit (e.g., 0%).

[0025] In executing the voltage rise suppression function, the output control unit 13 first executes the leading phase operation control function. In the leading phase operation control function, as described above, the power factor of the output power is gradually changed to a set power factor (e.g., 85%). After that, if the power factor of the output power becomes the set power factor but the grid overvoltage is not eliminated, the output suppression function is subsequently executed. In the output suppression function, as described above, the output power is gradually suppressed to a set limit (e.g., 0%). In this embodiment, when executing the output suppression function, the output control unit 13 continues the leading phase operation control function. Note that the output control unit 13 may determine whether the grid overvoltage has been eliminated based on the determination result by the detection unit 12 (determination result of whether the grid voltage has become less than the function stop level). For example, when the detection unit 12 determines that the grid overvoltage has been eliminated, it stops outputting and transmitting the overvoltage detection signal. As a result, the output control unit 13 of each power conversion device A1 determines that the grid overvoltage has been eliminated because the overvoltage detection signal is not input, and stops the voltage rise suppression function. The method by which the output control unit 13 determines whether the grid overvoltage has been eliminated is not limited to the absence of an input of an overvoltage detection signal. For example, the detection unit 12 may output a signal (overvoltage elimination signal) notifying that the grid overvoltage has been eliminated to the output control unit 13 and transmit it to another power conversion device A1, and the output control unit 13 may determine that the grid overvoltage has been eliminated based on the input of the overvoltage elimination signal.

[0026] Fig. 2 is a flowchart showing control executed by each power conversion device A1 in the overvoltage suppression process performed by the power system S1. The control shown in Fig. 2 is continued while the power system S1 is interconnected with the power grid D, and ends when the interconnection is released.

[0027] First, the detection unit 12 checks whether or not an overvoltage detection signal has been received from the other power conversion device A1 (S101). In step S101, if an overvoltage detection signal has not been received (S101: NO), the detection unit 12 detects the system voltage (output end voltage) (S102). Next, the detection unit 12 checks whether or not the detected system voltage is equal to or higher than an overvoltage level (S103). In step S103, if the system voltage is equal to or higher than the overvoltage level (S103: YES), the detection unit 12 determines that a system overvoltage has occurred, and outputs an overvoltage detection signal to the output control unit 13 and transmits the signal to the other power conversion device A1 via the communication unit 11 (S104). In step S104, when the detection unit 12 outputs an overvoltage detection signal to the output control unit 13, the output control unit 13 to which the overvoltage detection signal has been input executes a leading phase operation control function of a voltage rise suppression function (S105). In this step S105, if the leading phase operation control function has already been executed, the output control unit 13 changes the power factor of the output power by a predetermined change amount. That is, every time the output control unit 13 proceeds to the process of step S105, the output control unit 13 changes the power factor of the output power by a predetermined change amount, gradually changing it up to the set power factor (e.g., 85%). Also, in the case where an overvoltage detection signal is received in step S101 (S101: YES), since a system overvoltage is detected in the other power conversion device A1 and the process of step S104 is executed, an overvoltage detection signal is output from the communication unit 11 to the output control unit 13, and the output control unit 13 executes the process of step S105 (executing the leading phase operation control function).

[0028] In step S105, when the output control unit 13 executes the leading phase operation control function, the detection unit 12 checks whether the power factor of the current output power is the set power factor (S106). In step S106, if the current power factor is not the set power factor (S106: NO), the process returns to step S101. On the other hand, in step S106, if the current power factor is the set power factor (S106: YES), the output control unit 13 executes the output suppression function of the voltage rise suppression function (S107). Note that, when the output suppression function is executed, the leading phase operation control function is continued as it is. In this step S107, if the output suppression function has already been executed, the output control unit 13 suppresses the output power by a predetermined change amount. That is, each time the process of step S107 is shifted to, the output control unit 13 suppresses the output power by a predetermined change amount, gradually suppressing it up to the above-mentioned set limit (for example, 0%). In step S107, if the output power is restricted to the set limit, this state is maintained.

[0029] In step S103, if the system voltage is less than the overvoltage level (S103: NO), the detection unit 12 checks whether or not the system is in a state of outputting and transmitting an overvoltage detection signal (S108). In step S108, if the system is not in an output and transmission state (S108: NO), the detection unit 12 determines that the system is not currently in an overvoltage state, and then the detection unit 12 checks whether or not the output control unit 13 is executing an output suppression function (S111). On the other hand, in step S108, if the system is in an output and transmission state (S108: YES), the detection unit 12 then checks whether or not the system voltage is less than the function stop level (S109). In step S109, if the system voltage is equal to or greater than the function stop level (S109: NO), the detection unit 12 determines that the system overvoltage has not been resolved, and proceeds to the process of step S104, where the detection unit 12 outputs and transmits an overvoltage detection signal. On the other hand, in step S109, if the system voltage is less than the function failure level (S109: YES), the detection unit 12 determines that the system overvoltage has been resolved, and stops outputting and transmitting the overvoltage detection signal (S110). This stops the transmission of the overvoltage detection signal to the other power electronics devices A1. Then, the process proceeds to step S111.

[0030] In step S111, if the output suppression function is being executed (S111: YES), the detection unit 12 causes the output control unit 13 to cancel the output suppression function (S112). Then, the process proceeds to step S101. On the other hand, in step S111, if the output suppression function is not being executed (S111: NO), the detection unit 12 checks whether the output control unit 13 is executing the leading phase operation control function (S113). In step S113, if the leading phase operation control function is being executed (S113: YES), the detection unit 12 causes the output control unit 13 to cancel the leading phase operation control function (S114). Then, the process returns to step S101. On the other hand, in step S112, if the leading phase operation control function is not being executed (S113: NO), the process returns to step S101.

[0031] In the overvoltage suppression process of the power system S1, when any one of the power conversion devices A1 detects an occurrence of a system overvoltage in response to an overvoltage (system overvoltage) in the power system D by the control of FIG. 2 described above, the power conversion device A1 that detects the occurrence of the system overvoltage transmits an overvoltage detection signal to the other power conversion devices A1. As a result, a voltage rise suppression function (first, a leading phase operation control function) is executed in all of the multiple power conversion devices A1. Note that the control executed by each power conversion device A1 shown in FIG. 2 is an example and is not limited to this.

[0032] The functions and effects of the power system S1 are as follows.

[0033] In the power system S1, in each of the multiple power conversion devices A1, the output control unit 13 executes a voltage rise suppression function when the detection unit 12 of any of the multiple power conversion devices A1 detects a grid overvoltage. In executing this voltage rise suppression function, the output control unit 13 first executes a leading phase operation control function. After that, the output control unit 13 executes an output suppression function when the grid voltage does not become less than the function stop level even if the leading phase operation control function is executed. According to this configuration, the detection of a grid overvoltage by the detection unit 12 of any of the multiple power conversion devices A1 is triggered, and the leading phase operation control function is executed in all of the multiple power conversion devices A1 first. That is, even in the power conversion device A1 that has not detected a grid overvoltage, the leading phase operation control function is executed. Therefore, by executing the leading phase operation suppression function in all of the multiple power conversion devices A1, the possibility of suppressing the grid overvoltage is increased, so that the execution of an unnecessary output suppression function can be suppressed. That is, in the power system S1, when a grid overvoltage occurs and the voltage rise suppression function is activated, unnecessary suppression of output power can be reduced. Furthermore, since unnecessary suppression of output power can be reduced in this manner, if the power device X connected to the power conversion device A1 generates power using renewable energy, the renewable energy can be utilized to the maximum extent, and if the power device X connected to the power conversion device A1 charges and discharges a storage battery or the like, the possibility of affecting the operation of the electricity trading market, etc. is reduced.

[0034] In the power system S1, each of the multiple power conversion devices A1 includes a detection unit 12, and when the detection unit 12 in each of the multiple power conversion devices A1 detects a grid overvoltage, it transmits an overvoltage detection signal indicating the detection of the grid overvoltage to each of the other power conversion devices A1. Then, in the power conversion device A1 that receives the overvoltage detection signal, the output control unit 13 executes a voltage rise suppression function upon receiving the overvoltage detection signal. According to this configuration, if a grid overvoltage is detected in any of the multiple power conversion devices A1, each of the multiple power conversion devices A1 can determine that a grid overvoltage has occurred regardless of the detection result of the corresponding detection unit 12 (whether the grid voltage has reached or exceeded the overvoltage level). In other words, in the power system S1, the detection of a grid overvoltage by any of the multiple power conversion devices A1 can be used to cause each of the multiple power conversion devices A1 to execute a voltage rise suppression function (first, a leading phase operation control function).

[0035] 3 shows a power system S2 according to the second embodiment. The power system S2 is different from the power system S1 in the following respect: one of the multiple power electronics devices A1 is a master device, the others are slave devices, and only the master power electronics device A1 is provided with a detection unit 12.

[0036] In the power system S2, the multiple power electronics devices A1 include a first power electronics device A11 that is a master device and multiple second power electronics devices A12 that are slave devices. The number of second power electronics devices A12 may be one. As shown in FIG. 3, the first power electronics device A11 includes a communication unit 11, a detection unit 12, and an output control unit 13. Each second power electronics device A12 includes the communication unit 11 and the output control unit 13, but does not include a detection unit 12. Therefore, the detection unit 12 of the first power electronics device A11 can detect a system overvoltage, similar to the power electronics device A1 in the power system S1. On the other hand, each second power electronics device A12 does not detect a system overvoltage individually because it does not include a detection unit 12.

[0037] The communication unit 11 of the first power conversion device A11 communicates with each of the communication units 11 of the multiple second power conversion devices A12. The communication unit 11 of each of the multiple second power conversion devices A12 communicates with the communication unit 11 of the first power conversion device A11. Communication between the communication units 11 of the multiple second power conversion devices A12 does not have to be performed.

[0038] Similar to each power conversion device A1 of the power system S1, when the detection unit 12 of the first power conversion device A11 detects a grid overvoltage, it outputs an overvoltage detection signal to the output control unit 13 and transmits the overvoltage detection signal to each second power conversion device A12 via the communication unit 11. Furthermore, the detection unit 12 of the first power conversion device A11 does not output or transmit the overvoltage detection signal unless a grid overvoltage occurs.

[0039] The overvoltage detection signal is a signal that notifies detection of a system overvoltage, similar to the power system S1. The overvoltage detection signal is output or transmitted by the detection unit 12 of the first power conversion device A11 when the system voltage (output end voltage) becomes equal to or higher than the overvoltage level. The output control unit 13 of the first power conversion device A11 to which the overvoltage detection signal is input, and the output control unit 13 of each of the second power conversion devices A12 that receives the overvoltage detection signal, each executes a voltage rise suppression function, a leading phase operation control function, and an output suppression function in this order based on the overvoltage detection signal.

[0040] Fig. 4 is a flowchart showing the control executed by the first power conversion device A11 in the grid overvoltage suppression process performed by the power system S2, and Fig. 5 is a flowchart showing the control executed by each second power conversion device A12 in the grid overvoltage suppression process performed by the power system S2. Each control shown in Fig. 4 and Fig. 5 continues while the power system S2 is connected to the power system D, and ends when the connection is released.

[0041] As shown in Fig. 4, the control executed by the first power conversion device A11 does not include the process of step S101, as compared with the control executed by each power conversion device A1 of the power system S1 (see Fig. 2). The first power conversion device A11 does not receive an overvoltage detection signal from each second power conversion device A12. Therefore, the first power conversion device A11 does not execute a voltage rise suppression function upon receiving an overvoltage detection signal. That is, the first power conversion device A11 does not need to perform a process of checking whether or not an overvoltage detection signal has been received. Other processes are performed in the same manner as each power conversion device A1 of the power system S1.

[0042] As shown in Fig. 5, the control executed by each second power conversion device A12 does not include the processes of steps S102 to S104 and S108 to S110, as compared with the control executed by each power conversion device A1 of the power system S1 (see Fig. 2). Each second power conversion device A12 executes and cancels a voltage rise suppression function in accordance with a signal (overvoltage detection signal) from the first power conversion device A11, and does not include a detection unit 12. Therefore, each second power conversion device A12 does not need to perform processes such as detection of a system voltage and detection of a system overvoltage (transmission of an overvoltage detection signal). Other processes are performed in the same manner as each power conversion device A1 of the power system S1.

[0043] In the overvoltage suppression process of the power system S2, when the first power conversion device A11 detects an occurrence of a system overvoltage in the power system D (system overvoltage) by each of the controls of Fig. 4 and Fig. 5 described above, the first power conversion device A11 transmits an overvoltage detection signal to each of the second power conversion devices A12. As a result, a voltage rise suppression function (first, a leading phase operation control function) is executed in all of the multiple power conversion devices A1 (the first power conversion device A11 and the multiple second power conversion devices A12). Note that the control executed by the first power conversion device A11 shown in Fig. 4 and the control executed by each of the second power conversion devices A12 shown in Fig. 5 are merely examples and are not limited thereto.

[0044] The actions and effects of the power system S2 are as follows.

[0045] In the power system S2, in the multiple power conversion devices A1 (the first power conversion device A11 and the multiple second power conversion devices A12), the output control unit 13 executes a voltage rise suppression function when the detection unit 12 of the first power conversion device A11 detects a grid overvoltage. In executing this voltage rise suppression function, the output control unit 13 of each power conversion device A1 (the first power conversion device A11 and the multiple second power conversion devices A12) first executes a leading phase operation control function. Thereafter, the output control unit 13 of each power conversion device A1 (the first power conversion device A11 and the multiple second power conversion devices A12) executes an output suppression function when the grid voltage does not become less than a function stop level even if the leading phase operation control function is executed. According to this configuration, the detection of a grid overvoltage by the detection unit 12 of the first power conversion device A11 triggers the leading phase operation control function to be executed in all of the multiple power conversion devices A1 (the first power conversion device A11 and the multiple second power conversion devices A12). That is, even the second power conversion device A12 that cannot individually detect a grid overvoltage executes the leading phase operation control function. Therefore, by executing the leading phase operation suppression function in all of the multiple power conversion devices A1, it becomes more likely that the grid overvoltage can be suppressed, and therefore it is possible to suppress the execution of unnecessary output suppression functions. That is, the power system S2 can reduce unnecessary suppression of output power when a grid overvoltage occurs and the voltage rise suppression function is activated.

[0046] In the power system S2, the multiple power electronics devices A1 include a first power electronics device A11 serving as a master device and multiple second power electronics devices A12 serving as slave devices. When the first power electronics device A11 detects a grid overvoltage, it transmits an overvoltage detection signal indicating the detection of the grid overvoltage to each of the multiple second power electronics devices A12. Then, in each of the second power electronics devices A12 that has received the overvoltage detection signal, the output control unit 13 executes a voltage rise suppression function upon receiving the overvoltage detection signal. According to this configuration, if the first power electronics device A11 detects a grid overvoltage, each of the multiple second power electronics devices A12 can determine that a grid overvoltage has occurred without detecting the grid voltage. That is, in the power system S2, the detection of the grid overvoltage by the first power electronics device A11 can be used to cause each of the multiple power electronics devices A1 (the first power electronics device A11 and the multiple second power electronics devices A12) to execute a voltage rise suppression function (first, a leading phase operation control function).

[0047] Fig. 6 shows a power system S3 according to a third embodiment. The power system S3 is different from the power system S1 in the following respects. First, as shown in Fig. 6, the power system S3 includes a detection device B1 in addition to a plurality of power electronics devices A1. Second, as shown in Fig. 6, none of the plurality of power electronics devices A1 includes a detection unit 12.

[0048] The detection device B1 is capable of monitoring the system voltage and detecting a system overvoltage, similar to the power conversion device A1 in the power system S1 and the first power conversion device A11 in the power system S2. The detection device B1 includes a communication unit 21 and a detection unit 22.

[0049] The communication unit 21 communicates with each of the multiple power electronics devices A1 (each communication unit 11). The communication may be wireless communication or wired communication.

[0050] The detection unit 22 is configured similarly to the detection unit 12, and monitors the system voltage of the power system D to detect whether or not there is a system overvoltage. The detection unit 22 is installed on a power line connecting the connection point K and the power system D, and detects the system voltage of the power system D. The detection unit 22 transmits the above-mentioned overvoltage detection signal to each power conversion device A1 via the communication unit 21 based on the detected system voltage. Each power conversion device A1 executes a voltage rise suppression function (leading phase operation control function and output suppression function) upon receiving an overvoltage detection signal, and stops the voltage rise suppression function (leading phase operation control function and output suppression function) upon not receiving an overvoltage detection signal.

[0051] Fig. 7 is a flowchart showing the control executed by the detection device B1 in the overvoltage suppression process performed by the power system S3. The control shown in Fig. 7 is continued while the power system S3 is connected to the power grid D, and ends when the connection is released.

[0052] As shown in FIG. 7, the control executed by the detection device B1 does not include the processes of steps S101, S105 to S107, S111, and S112, as compared with the control executed by each power electronics device A1 of the power system S1 (see FIG. 2). The detection device B1 detects the grid voltage and the grid overvoltage (transmits an overvoltage detection signal), and does not execute a voltage rise suppression function. Therefore, the detection device B1 does not need to perform processes related to the execution and release of the voltage rise suppression function. The other processes are performed in the same manner as in each power electronics device A1 of the power system S1. In the process of detecting the grid voltage in step S102, the detection unit 22 detects the voltage at the connection position (the power line connecting the connection point K and the power system D).

[0053] As described above, the detection device B1 appropriately transmits a signal to each power electronics device A1 based on the relationship between the system voltage and the overvoltage level or the function stop level. Each power electronics device A1 performs the control shown in FIG. 5 in the same manner as each of the second power electronics devices A12, and starts and stops the voltage rise suppression function (the leading phase operation control function and the output suppression function) depending on whether an overvoltage detection signal is received or not.

[0054] In the overvoltage suppression process of the power system S3, when the detection device B1 detects an occurrence of a system overvoltage in the power system D (system overvoltage) by the control of Fig. 7 described above, it transmits an overvoltage detection signal to each power conversion device A1. As a result, a voltage rise suppression function (first, a leading phase operation control function) is executed in all of the multiple power conversion devices A1. Note that the control executed by the detection device B1 shown in Fig. 7 is an example and is not limited to this.

[0055] The functions and effects of the power system S3 are as follows.

[0056] In the power system S3, in the plurality of power conversion devices A1, the output control unit 13 executes a voltage rise suppression function when the detection unit 22 of the detection device B1 detects a system overvoltage. In executing this voltage rise suppression function, the output control unit 13 of each power conversion device A1 first executes a leading phase operation control function. After that, when the output control unit 13 of each power conversion device A1 executes the leading phase operation control function, the output suppression function is executed when the system voltage does not become less than the function stop level even if the leading phase operation control function is executed. According to this configuration, the detection of the system overvoltage by the detection unit 22 of the detection device B1 is triggered, and the leading phase operation control function is executed in all of the plurality of power conversion devices A1 first. That is, even in the power conversion device A1 that has not detected the system overvoltage, the leading phase operation control function is executed. Therefore, by executing the leading phase operation suppression function in all of the plurality of power conversion devices A1, the possibility of suppressing the system overvoltage is increased, so that the execution of the unnecessary output suppression function can be suppressed. That is, in the power system S3, when a system overvoltage occurs and the voltage rise suppression function is operated, unnecessary suppression of the output power can be reduced.

[0057] The power system S3 includes a detection device B1 that monitors the system voltage, and when the detection device B1 detects a system overvoltage, it transmits an overvoltage detection signal indicating the occurrence of a system overvoltage to each of the multiple power conversion devices A1. Then, in each power conversion device A1 that receives the overvoltage detection signal, the output control unit 13 executes a voltage rise suppression function upon receiving the overvoltage detection signal. With this configuration, if the detection device B1 detects a system overvoltage, each of the multiple power conversion devices A1 can determine that a system overvoltage has occurred without detecting the system voltage. In other words, the power system S3 can cause each of the multiple power conversion devices A1 to execute a voltage rise suppression function (first, a leading phase operation control function) upon detection of a system overvoltage by the detection device B1.

[0058] The power system according to the present disclosure is not limited to the above-described embodiment. The specific configuration of each part of the power system according to the present disclosure can be freely designed in various ways. [Explanation of symbols]

[0059] S1, S2, S3: power system, A1: power conversion device, A11: first power conversion device, A12: second power conversion device, B1: detection device, D: power system, 12, 22: detection unit, 13: output control unit

Claims

1. A plurality of power conversion devices each capable of reverse power flow to a power grid; a detection unit that monitors a system voltage of the power system and detects whether the system voltage is a system overvoltage that is equal to or higher than an overvoltage level; Equipped with Each of the plurality of power conversion devices includes an output control unit that has a voltage rise suppression function and controls an output power to the power grid side, The voltage rise suppression function includes a leading phase operation control function for changing the power factor of the output power in a leading direction as viewed from the output control unit, and an output suppression function for suppressing the output power, a power control unit that, in each of the plurality of power conversion devices, executes the voltage rise suppression function when the detection unit detects the system overvoltage, and in executing the voltage rise suppression function, executes the leading phase operation control function, and if the system voltage does not become less than a function shutdown level for determining the elimination of the system overvoltage even after executing the leading phase operation control function, executes the output suppression function.

2. The detection unit is provided in each of the plurality of power conversion devices, In each of the plurality of power electronics devices, the corresponding detection unit monitors an output end voltage of the corresponding power electronics device on the power grid side as the grid voltage, When the corresponding detection unit detects the grid overvoltage, each of the plurality of power conversion devices transmits an overvoltage detection signal indicating an occurrence of the grid overvoltage to each of the other power conversion devices while executing the voltage rise suppression function by the output control unit; The power system according to claim 1 , wherein in each of the other power electronics devices, the output control unit executes the voltage rise suppression function upon receiving the overvoltage detection signal.

3. the plurality of power electronics devices include a first power electronics device serving as a master device and at least one second power electronics device serving as a slave device, the detection unit is provided in the first power conversion device and monitors an output end voltage of the first power conversion device on the power grid side as the grid voltage; When the detection unit detects the grid overvoltage, the first power conversion device transmits an overvoltage detection signal indicating an occurrence of the grid overvoltage to each of the at least one second power conversion device while executing the voltage rise suppression function by the output control unit; The power system according to claim 1 , wherein in each of the at least one second power conversion device, the output control unit executes the voltage rise suppression function upon receiving the overvoltage detection signal.

4. A detection device including the detection unit and provided separately from each of the plurality of power conversion devices, When the detection unit detects the grid overvoltage, the detection device transmits an overvoltage detection signal indicating an occurrence of the grid overvoltage to each of the plurality of power conversion devices; The power system according to claim 1 , wherein in each of the plurality of power conversion devices, the output control unit executes the voltage rise suppression function upon receiving the overvoltage detection signal.

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