Power converter, power converter control method, power system, power system control method and program

Abstract

This power converter is connected to a transmission line and comprises: an input unit that is electrically connected to a device to which power from the transmission line can be input and / or which can output power to the transmission line; a voltage varying unit that is connected to the input unit and varies voltage; a voltage adjusting unit that is connected to the voltage varying unit and adjusting voltage to the transmission line; a target setting unit for setting a first target value of the voltage varying unit; a voltage monitoring unit that is connected to the transmission line and monitors the voltage of the transmission line; and a threshold determination mechanism that is connected to the voltage monitoring unit and calculates a second target value of the voltage adjusting unit in accordance with the voltage of the transmission line. The target setting unit generates the first target value as an output target of the voltage varying unit in accordance with the voltage monitored by the voltage monitoring unit, and the first target value has a characteristic of changing, in accordance with time, a threshold value for controlling the output of the voltage adjusting unit.

Description

[Technical field]

[0001] The present invention relates to a power converter that is electrically connected to an AC commercial power system via a transmission line that transports power and is electrically connected to an equipment that can input power from the transmission line and / or output power to the transmission line, the power converter having a function of controlling the equipment based on a reference function that generates a target value when performing self-end control of the equipment in accordance with a voltage observed by the power converter, and a power system including the power converter. [Background technology]

[0002] In recent years, power networks that use locally produced electricity have been attracting attention as an alternative to large-scale power networks that rely on fossil energy and nuclear energy. A wide variety of devices are connected to power networks that use locally produced electricity, such as photovoltaic power generation devices (PV), which are power generation devices that generate electricity using renewable energy, stationary power storage devices, and EV chargers for charging electric vehicles (EVs). Since each of the above devices is a direct current (DC) power source, studies are underway to build a direct current (DC) power network (DC grid) equipped with a power converter.

[0003] Conventionally, the method of controlling a DC grid has been to centrally control the amount of power in the DC bus of the DC grid by having power converters connected to photovoltaic power generation equipment (PV) and stationary energy storage devices, etc., perform constant current control and constant voltage control of the photovoltaic power generation equipment (PV) and stationary energy storage devices, etc. based on instructions from a centralized control unit.

[0004] Droop control is also performed by providing a reference function based on the power (P) and voltage (V) at the self-end to a photovoltaic power generation device (PV) or a stationary power storage device, etc., and making the photovoltaic power generation device (PV) or a stationary power storage device have a droop characteristic in the target voltage value according to the amount of power required by the DC bus from the reference function. Droop control is a control that performs control with a droop characteristic in the relationship between the output power or output current and the output voltage, thereby giving a virtual impedance to the device electrically connected to the power converter, and performing load sharing between the power converters. By controlling the photovoltaic power generation device (PV) or the stationary power storage device in an autonomous and decentralized manner by droop control, the adjustment of the output amount from the photovoltaic power generation device (PV) and the input / output amount of the stationary power storage device are optimized according to the amount of power required by the DC bus, and the voltage of the DC bus can be stabilized.

[0005] Conventional droop control involves, for example, updating a reference function that has droop characteristics and shifts its intercept (the voltage (V) of the entire DC grid) to the high-voltage side or the low-voltage side in response to changes in the charging rate of the stationary energy storage device while stabilizing the voltage of the DC bus, in order to stabilize the state of charge of the stationary energy storage device. An example of a reference function that is updated as described above is a reference function that provides a constant input / output range in which the target input / output of the energy storage device is maintained at 0 over a predetermined voltage range (Patent Document 1). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2019 / 103059 Summary of the Invention [Problem to be solved by the invention]

[0007] Although the above-mentioned centralized control method of the DC grid can easily control the entire DC grid, it has a problem that it is difficult to smoothly respond to sudden fluctuations in supply and demand of power. In Patent Document 1, by providing a constant input / output range in which the input / output is 0 in the reference function, when the DC grid is in steady operation, it is possible to cover the power supply of the DC grid with power supplied from an external commercial power system or a photovoltaic power generation device (PV) without charging / discharging the power storage device.

[0008] On the other hand, for example, when at least a part of the power supply of the DC grid is provided by power supplied from a photovoltaic power generation device (PV), a reference function for controlling the output of the photovoltaic power generation device (PV) may be a reference function that suppresses the output (power) P of the photovoltaic power generation device (PV) when the voltage V of the DC bus rises to a threshold value V_thresh, as shown in Fig. 6. The reference function shown in Fig. 6 aims to stabilize the voltage of the DC bus by suppressing the output (power) P of the photovoltaic power generation device (PV) due to an increase in the voltage V of the DC bus.

[0009] However, if the threshold value V_thresh of the reference function shown in Fig. 6 is set high to reduce power supply from an external commercial power system and improve the power efficiency of the photovoltaic power generation device (PV), it may be difficult to stabilize the voltage of the DC bus when a disturbance occurs due to a load change, etc. On the other hand, if the threshold value V_thresh of the reference function shown in Fig. 6 is set low to stabilize the voltage of the DC bus even when a disturbance occurs due to a load change, etc., output suppression of the photovoltaic power generation device (PV) becomes more likely, and there is a problem that the power efficiency of the photovoltaic power generation device (PV) cannot be improved.

[0010] In view of the above circumstances, the present invention aims to provide a power converter that can stabilize the voltage of a transmission line even when a disturbance occurs in the power network, while improving the power efficiency of equipment that constitutes the power network, and a power system including the power converter, as well as a method for controlling the power converter, a method for controlling the power system, and a program. [Means for solving the problem]

[0011] The gist of the configuration of the present invention is as follows. [1] A power converter connected to a power transmission line, an input unit electrically connected to a device capable of inputting electric power from the power transmission line and / or outputting electric power to the power transmission line; A voltage fluctuation unit that is connected to the input unit and that fluctuates a voltage; a voltage adjustment unit connected to the voltage fluctuation unit and adjusting a voltage to the power transmission line; a target setting unit that determines a target value of the voltage fluctuation unit; a voltage monitoring unit connected to the power transmission line and configured to monitor a voltage of the power transmission line; a threshold determination mechanism connected to the voltage monitoring unit and configured to calculate a target value for the voltage adjustment unit in response to a voltage of the power transmission line; Equipped with the target setting unit of the power converter generates a target value as an output target of the voltage fluctuation unit in response to the voltage observed by the voltage monitoring unit; The power converter has a characteristic in which the target value changes a threshold voltage of output control of the voltage adjusting unit according to time. [2] The power converter according to [1], which controls the device based on a reference function that generates the target value when controlling the device at its own end, depending on the voltage observed by the voltage monitoring unit. [3] The power converter according to [2], wherein the reference function has a predetermined time-limited characteristic. [4] The reference function is expressed by the following equation (1), where Vr is a threshold voltage value, C is the capacitance of the power transmission line, and Tr is a time constant determined according to the capacitance. Tr = function (Vr, C) (1) The relationship is as follows: The power converter according to claim 2 or 3, wherein, when an observed voltage at a terminal of the power converter is V0, and a state in which V0>Vr continues for Tr or longer, the voltage fluctuation unit controls to suppress the output of power from the equipment to the transmission line. [5] When the reference function has a threshold voltage value of Vr, the capacitance of the transmission line is C, and the time constant determined according to the capacitance is Tr, the following formula (1) Tr = function(Vr, C) (1) has the relationship of When the observed voltage at the self-terminal of the power converter is V0, when the state of V0 < Vr continues for Tr or more, the voltage fluctuation unit promotes the output of power from the device to the transmission line, and when V0 reaches Vr, the output promotion is stopped. The power converter according to any one of [2] to [4]. [6] The power converter according to [4] or [5], wherein the device is a power generation device. [7] The power converter according to [6], wherein the power generation device is a power generation device that generates power using renewable energy or a power generation device that generates power using fuel. [8] When the reference function has a threshold voltage value of Vr, the capacitance of the transmission line is C, and the time constant determined according to the capacitance is Tr, the following formula (1) Tr = function(Vr, C) (1) has the relationship of When the observed voltage at the self-terminal of the power converter is V0, when the state of V0 < Vr continues for Tr or more, the voltage fluctuation unit controls to suppress the input of power from the transmission line to the device. The power converter according to [2] or [3]. [9] When the reference function has a threshold voltage value of Vr, the capacitance of the transmission line is C, and the time constant determined according to the capacitance is Tr, the following formula (1) Tr = function(Vr, C) (1) has the relationship of When the observed voltage at the self-terminal of the power converter is V0, when the state of V0 > Vr continues for Tr or more, the voltage fluctuation unit promotes the input of power from the transmission line to the device, and when V0 reaches Vr, the input promotion is stopped. The power converter according to [2], [3] or [8].

[10] The power converter according to [8] or [9], wherein the device is a load.

[11] The power converter according to

[10] , wherein the load is an EV charger for charging an on-board storage battery mounted in an electric vehicle.

[12] A power element is provided, the power element including a power converter and a device electrically connected to the power converter; an input unit electrically connected to a device capable of receiving power from a power transmission line and / or outputting power to the power transmission line; A voltage fluctuation unit that is connected to the input unit and that fluctuates a voltage; a voltage adjustment unit connected to the voltage fluctuation unit and adjusting a voltage to the power transmission line; a target setting unit that determines a target value of the voltage fluctuation unit; a voltage monitoring unit connected to the power transmission line and configured to monitor a voltage of the power transmission line; a threshold determination mechanism connected to the voltage monitoring unit and configured to calculate a target value for the voltage adjustment unit in response to a voltage of the power transmission line; A power system comprising: the target setting unit of the power converter generates a target value as an output target of the voltage fluctuation unit in response to the voltage observed by the voltage monitoring unit; The power system has a characteristic in which the target value changes a threshold voltage of output control of the voltage regulator over time.

[13] The power system described in

[12] has a function of controlling the equipment based on the reference function that generates a target value when controlling the equipment at its own end in accordance with the voltage observed by the voltage monitoring unit.

[14] The power system of

[13] , wherein the reference function has a predetermined time-limited characteristic.

[15] The reference function is expressed by the following equation (1), where Vr is a threshold voltage value, C is the capacitance of the power transmission line, and Tr is a time constant determined according to the capacitance. Tr = function (Vr, C) (1) The relationship is as follows: When the observed voltage at the self-terminal of the power converter is V0, when the state of V0 > Vr continues for Tr or more, the voltage fluctuation unit controls so as to suppress the power output from the device to the power transmission line, the power system according to

[13] or

[14] .

[16] When the reference function has a threshold voltage value of Vr, the capacitance of the power transmission line is C, and the time constant Tr determined according to the capacitance is as follows in formula (1) Tr = function(Vr, C) (1) has the relationship of When the observed voltage at the self-terminal of the power converter is V0, when the state of V0 < Vr continues for Tr or more, the voltage fluctuation unit promotes the power output from the device to the power transmission line, and controls to stop the output promotion when V0 reaches Vr, the power system according to any one of

[13] to

[15] .

[17] The power system according to

[15] or

[16] , wherein the device is a power generation device.

[18] The power system according to

[17] , wherein the power generation device is a power generation device that generates power using renewable energy or a power generation device that generates power using fuel.

[19] When the reference function has a threshold voltage value of Vr, the capacitance of the power transmission line is C, and the time constant Tr determined according to the capacitance is as follows in formula (1) Tr = function(Vr, C) (1) has the relationship of When the observed voltage at the self-terminal of the power converter is V0, when the state of V0 < Vr continues for Tr or more, the voltage fluctuation unit controls so as to suppress the power input from the power transmission line to the device, the power system according to

[13] or

[14] .

[20] When the reference function has a threshold voltage value of Vr, the capacitance of the power transmission line is C, and the time constant Tr determined according to the capacitance is as follows in formula (1) Tr = function(Vr, C) (1) has the relationship of The power system of

[13] or

[19] , wherein when an observed voltage at a local end of the power converter is V0, when a state in which V0>Vr continues for Tr or longer, the voltage fluctuation unit promotes the input of power from the transmission line to the equipment, and when V0 reaches Vr, the input promotion is stopped.

[21] The power system according to

[19] or

[20] , wherein the equipment is a load.

[22] The power system according to

[21] , wherein the load is an EV charger for charging an on-board storage battery installed in an electric vehicle.

[23] The power system according to any one of

[12] to

[22] , wherein the transmission line is a DC bus.

[24] A method for controlling a power converter connected to a power transmission line and having an input unit connected to a device capable of inputting power from the power transmission line and / or outputting power to the power transmission line, comprising: A voltage fluctuation unit connected to the input unit fluctuates a voltage; A voltage adjusting unit connected to the voltage fluctuation unit adjusts a voltage to the power transmission line; determining a first target value of the voltage fluctuation unit; Observing a voltage of the power transmission line; calculating a second target value of the voltage adjusting unit in response to the observed voltage of the power transmission line; Equipped with generating the first target value as an output target of the voltage fluctuation unit in response to the observed voltage of the power transmission line; A control method for a power converter, wherein the target value has a characteristic that causes a threshold voltage of output control of the voltage regulator to change with time.

[25] A power element is provided, the power element including a power converter and a device electrically connected to the power converter; A method for controlling a power system, the power converter being connected to a power transmission line, and an input unit of the power converter being connected to a device capable of inputting power from the power transmission line and / or outputting power to the power transmission line, comprising: A voltage fluctuation unit connected to the input unit fluctuates a voltage; A voltage adjusting unit connected to the voltage fluctuation unit adjusts a voltage to the power transmission line; determining a first target value of the voltage fluctuation unit; Observing a voltage of the power transmission line; calculating a second target value of the voltage adjusting unit in response to the observed voltage of the power transmission line; Equipped with generating the first target value as an output target of the voltage fluctuation unit in response to the observed voltage of the power transmission line; A control method for a power system, wherein the target value has a characteristic of changing a threshold voltage of output control of the voltage regulator over time.

[26] A power element is provided, the power element including a power converter and a device electrically connected to the power converter; The power converter is connected to a power transmission line, and an input unit of the power converter is connected to the device capable of inputting power from the power transmission line and / or outputting power to the power transmission line; A control method for a power system including the power converter and a central control device capable of communicating with an external server that holds power demand information, A voltage fluctuation unit connected to the input unit fluctuates a voltage; A voltage adjusting unit connected to the voltage fluctuation unit adjusts a voltage to the power transmission line; determining a first target value of the voltage fluctuation unit; Observing a voltage of the power transmission line; calculating a second target value of the voltage adjusting unit in response to the observed voltage of the power transmission line; acquiring the demand information from the external server; Equipped with generating the first target value as an output target of the voltage fluctuation unit in response to the observed voltage of the power transmission line; A control method for a power system, wherein the target value has a characteristic of changing a threshold voltage of output control of the voltage regulator over time.

[27] The processor: A program for executing a control method for a power converter connected to a power transmission line and having an input unit connected to a device capable of inputting power from the power transmission line and / or outputting power to the power transmission line, the program comprising: A voltage fluctuation unit connected to the input unit fluctuates a voltage; A voltage adjusting unit connected to the voltage fluctuation unit adjusts a voltage to the power transmission line; determining a first target value of the voltage fluctuation unit; Observing a voltage of the power transmission line; calculating a second target value of the voltage adjusting unit in response to the observed voltage of the power transmission line; Equipped with generating the first target value as an output target of the voltage fluctuation unit in response to the observed voltage of the power transmission line; The target value has a characteristic of changing a threshold voltage of the output control of the voltage adjusting unit according to time. program.

[28] The processor: A program for executing a control method for a power system in which a power element is provided, the power element including a power converter and a device electrically connected to the power converter, the power converter being connected to a power transmission line, and an input unit of the power converter being connected to the device capable of inputting power from the power transmission line and / or outputting power to the power transmission line, A voltage fluctuation unit connected to the input unit fluctuates a voltage; A voltage adjusting unit connected to the voltage fluctuation unit adjusts a voltage to the power transmission line; determining a first target value of the voltage fluctuation unit; Observing a voltage of the power transmission line; calculating a second target value of the voltage adjusting unit in response to the observed voltage of the power transmission line; Equipped with generating the first target value as an output target of the voltage fluctuation unit in response to the observed voltage of the power transmission line; The target value has a characteristic of changing a threshold voltage of the output control of the voltage adjusting unit according to time. program. Effect of the Invention

[0012] According to an aspect of the power converter and a power system including a power converter of the present invention, the power converter generates a target value as an output target of the voltage fluctuation section of the power converter in accordance with the voltage of the transmission line observed by the voltage monitoring section of the power converter, and the target value has a characteristic of changing the threshold voltage of the output control of the voltage adjustment section of the power converter in accordance with time.As a result, when a disturbance occurs in the power network, it is possible to stabilize the voltage of the transmission line to which the equipment is electrically connected via the power converter, while improving the power efficiency of the equipment that constitutes the power network.

[0013] According to an embodiment of the power converter and a power system including a power converter of the present invention, a reference function having a characteristic of changing a threshold voltage for output suppression depending on time has a relationship of Tr=function(Vr,C), where Vr is the threshold voltage value, C is the capacitance of the transmission line, and Tr is a time constant determined depending on the capacitance. If the observed voltage at the own end of the power converter is V0, when the state of V0>Vr continues for Tr or more, the voltage fluctuation section of the power converter is controlled to suppress the output of power from the equipment to the transmission line, thereby more reliably stabilizing the voltage of the power network and more reliably improving the power efficiency of the equipment that outputs power.

[0014] According to an aspect of the power converter and the power system including the power converter of the present invention, a reference function having a characteristic of changing the input suppression threshold voltage according to time has a threshold voltage value of Vr, a capacitance of the transmission line is C, and a time constant determined according to the capacitance is Tr. When Tr = function(Vr, C) and the observed voltage at the self-terminal of the power converter is V0, when the state of V0 < Vr continues for Tr or more, the voltage fluctuation part of the power converter controls to suppress the input of power from the transmission line to the device, thereby more surely stabilizing the voltage of the power network and more surely improving the power efficiency of the device receiving power supply.

[0015] According to an aspect of the control method of the power converter of the present invention, the control method of the power system, and the program, when a disturbance occurs in the power network, it is possible to stabilize the voltage of the transmission line to which the device is electrically connected via the power converter, and at the same time, it is possible to improve the power efficiency of the devices constituting the power network.

Brief Description of Drawings

[0016] [Figure 1] FIG. 1 is an explanatory diagram showing an overview of the entire power network constituting a power system including a power converter according to an embodiment of the present invention. [Diagram 2] FIG. 2 is an explanatory diagram of a reference function given to a device used in a power network constituting a power system including a power converter according to an embodiment of the present invention. [Diagram 3] FIG. 3 is an explanatory diagram showing how the reference function given to a device used in a power system including a power converter according to an embodiment of the present invention is updated. [Figure 4] FIG. 4 is an example of a reference function having a time-limited characteristic given to a photovoltaic power generation device (PV) used in a power system including a power converter according to an embodiment of the present invention. [Diagram 5] FIG. 5 is a block diagram showing a structural example of the power converter of the present invention. [Figure 6]FIG. 6 shows a reference function having a conventional time-limited characteristic applied to a photovoltaic (PV) device used in a power system with a power converter. [Figure 7] FIG. 7 is a sequence diagram showing an example of a control method for a power system. [Figure 8] FIG. 8 is an example of a reference function having a time-limited characteristic that is given to a photovoltaic power generation device (PV) used in a power system including a power converter according to an embodiment of the present invention. [Figure 9] FIG. 9 shows an example of a reference function having a time-limited characteristic that is applied to an EV charger used in a power system including a power converter according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] <Embodiment> A power system including a power converter according to an embodiment of the present invention will be described. FIG. 1 is an explanatory diagram showing an overview of an entire power network constituting a power system including a power converter according to an embodiment of the present invention. FIG. 2 is an explanatory diagram showing a reference function given to a device used in a power network constituting a power system including a power converter according to an embodiment of the present invention. FIG. 3 is an explanatory diagram showing a state in which a reference function given to a device used in a power system including a power converter according to an embodiment of the present invention is updated. FIG. 4 is an example of a reference function having a time-limited characteristic given to a photovoltaic power generation device (PV) used in a power system including a power converter according to an embodiment of the present invention. FIG. 5 is a block diagram showing an example of the structure of a power converter according to the present invention. FIG. 7 is a sequence diagram showing an example of a control method for a power system.

[0018] In this specification, the "time-limited characteristic" of the reference function having the time-limited characteristic means a characteristic that, when an abnormal voltage that has a large effect on the voltage stabilization of the transmission line to which the equipment is electrically connected is observed, the input / output of power and current is stopped if the abnormal voltage continues for a short period of time, and, when an abnormal voltage that has a small effect on the voltage stabilization of the transmission line is observed, the input / output of power and current is stopped if the abnormal voltage continues for a certain period of time. In this specification, the transmission line may be simply referred to as a line.

[0019] As shown in Fig. 1, a power system 1 formed in a power network 10 equipped with a power converter according to an embodiment of the present invention includes a power converter that is electrically connected to an AC commercial power system 100 via a line (DC bus 19) and is electrically connected to a device capable of inputting power from the line (DC bus 19) and / or outputting power to the line (DC bus 19). That is, the power system 1 is provided with power elements including a power converter electrically connected to the AC commercial power system 100 via the line (DC bus 19) and a device electrically connected to the power converter and capable of inputting power from the line (DC bus 19) and / or outputting power to the line (DC bus 19) via the power converter.

[0020] Specifically, the system includes an AC / DC converter 11 that can be connected to an AC commercial power system 100 and converts AC power input from the AC commercial power system 100 into DC power and outputs it, a DC bus 19 connected to the output of the AC / DC converter 11, a first DC / DC converter 13 connected to the DC bus 19 and converts the DC power input from the DC bus 19 into a charging voltage for a storage battery to be charged and outputs it, a charger (EV charger 17 in the power network 10) that can be connected to the storage battery to be charged and is connected to the first DC / DC converter 13, a bidirectional DC / DC converter 12 that is connected to the DC bus 19 and converts the DC power input from the DC bus 19 into a charging voltage for a stationary energy storage device 14 and outputs it, and a solar power generation device (PV) 15 that is a power generation device that generates power using renewable energy and is connected to the DC bus 19 via a second DC / DC converter 16.

[0021] From the above, the power network 10 constituting the power system 1 is a DC grid, which is a direct current power network. In the power network 10, the storage battery is, for example, an on-board storage battery mounted on an electric vehicle (EV) 18, which is a load. The output of the DC bus 19 is connected to an EV charger 17, and the on-board storage battery of the electric vehicle 18 is connected to the EV charger 17 to charge the on-board storage battery. The stationary power storage device 14 is a power storage device within the power network 10 facility.

[0022] Each power converter includes, for example, a power conversion unit, a sensor, a control unit, and a communication unit.

[0023] The power conversion unit is a part in each power converter that has a power conversion function, which is AC / DC conversion or DC / DC conversion, and is composed of an electric circuit including, for example, a coil, a capacitor, a diode, a switching element, etc. The switching element is, for example, a field effect capacitor or an insulated gate bipolar transistor. The power conversion unit can control the power conversion characteristics by, for example, PWM (Pulse Width Modulation) control.

[0024] The sensors are used in each power converter to observe electrical characteristics such as current, voltage, power, etc. The sensors output the observed values ​​of the electrical characteristics (current value, voltage value, power value, etc.) to the control unit as observed values.

[0025] In a power system 1 equipped with a power network 10, a control unit controls the amount of power received from a commercial power system 100. The control unit also controls the charging and discharging of a stationary power storage device 14, the discharging of a solar power generation device 15, and the charging of an on-board storage battery of an electric vehicle 18 connected to an EV charger 17.

[0026] Each control unit includes a processor that performs various arithmetic processing for controlling the power conversion function and a storage unit. The processor is, for example, a central processing unit (CPU), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a digital signal processor (DSP), or a graphics processing unit (GPU). The storage unit includes, for example, a read only memory (ROM) in which various programs and data used by the processor to perform arithmetic processing are stored. The storage unit also includes, for example, a random access memory (RAM) used to store a working space when the processor performs arithmetic processing and results of the processor's arithmetic processing. The storage unit may include an auxiliary storage device such as a hard disk drive (HDD) or a solid state drive (SSD). The functions of each control unit are realized as functional units by the processor reading and executing various programs from the storage unit. For example, each control unit outputs a PWM signal including information on an operation amount (for example, a duty ratio) for PWM (Pulse Width Modulation) to the power conversion unit, and controls each power converter by PWM. Each control unit may output the manipulated variable directly to the power conversion unit, or may output the manipulated variable to the power conversion unit via another functional unit (not shown) (for example, a loop control unit).

[0027] The communication unit includes a communication module that communicates information by wire or wirelessly, and a communication control unit that controls the operation of the communication module. The communication unit communicates information with a central control unit 110, which is a central control device described later, via a network NW consisting of an Internet line network, a mobile phone line network, etc. The communication unit, for example, receives commands from the central control unit 110 and outputs them to the control unit. The communication unit, for example, transmits information on the power status input from the control unit to the central control unit 110. Note that if the information on the power status is a measurement value of a sensor, the communication unit may transmit the measurement value input from the sensor to the central control unit 110, for example.

[0028] An example of the central control unit 110 will be described. The central control unit 110 includes a control unit, a storage unit, and a communication unit. The configurations of the control unit, the storage unit, and the communication unit may be the same as those exemplified as the configurations of the control unit, the storage unit, and the communication unit of the power converter.

[0029] The functions of the control unit are realized as functional units by the control unit reading out and executing various programs from the storage unit.

[0030] The communication unit communicates information with each power converter and the external server 200 via the network NW.

[0031] The external server 200 is a server provided outside the power system 1. The external server 200 is, for example, an information processing device configured to function as an energy management system (EMS) in another power system, or an information processing device that includes a database and functions as a data server for the central control unit 110. The external server 200 stores various types of information that may affect the operation of the power system 1.

[0032] In the power system 1, the second DC / DC converter 16 has a function of controlling the photovoltaic power generation device (PV) 15 to follow a reference function, which is a control target function that generates a target value when controlling the photovoltaic power generation device (PV) 15 at its own end in accordance with the voltage (V) observed by the second DC / DC converter 16 at its own end, i.e., a function of controlling the output of the photovoltaic power generation device (PV) 15 based on the reference function.

[0033] The second DC / DC converter 16 connected to the photovoltaic power generation device (PV) 15 has a function of controlling the operation of the photovoltaic power generation device (PV) 15 so that the relationship between the voltage (V) at its own end and the power (P) at its own end, i.e., the voltage (V) at its own end and the power (P) output from the photovoltaic power generation device (PV) 15, follows a predetermined reference function. In other words, the second DC / DC converter 16 controls the relationship between the voltage (V) at its own end and the power (P) at its own end to maintain the predetermined reference function in a predetermined control period.

[0034] As a specific example, as shown in Fig. 2, the second DC / DC converter 16 connected to the photovoltaic power generation device (PV) 15 performs output control of the photovoltaic power generation device (PV) 15 when the power network 10 is in a transient operation zone with low power demand (in Fig. 2, the upper transient operation zone with a high voltage (V) value) (in Fig. 2, there is no output from the photovoltaic power generation device (PV) 15, i.e., power (P) = 0), and performs maximum power point tracking control (MPPT) on the photovoltaic power generation device (PV) 15 in other operation zones. Therefore, in Fig. 2, the output control of the photovoltaic power generation device (PV) 15 is not droop control.

[0035] In addition, in the power system 1, other power converters than the second DC / DC converter 16 also have a function of controlling the operation of the equipment so as to follow a reference function that generates a target value when controlling the equipment connected to the other power converter in accordance with the observed voltage of the other power converter at its own end.

[0036] In the power system 1, the AC / DC converter 11, which converts AC power input from an AC commercial power system 100 into DC power and outputs it, has a function of performing droop control so that the relationship between the voltage (V) at its own end and the power (P) at its own end, i.e., the voltage (V) at its own end and the power (P) output to the DC bus 19, has a predetermined droop characteristic. That is, the AC / DC converter 11 has a function of droop control of the input / output from the commercial power system 100 so that the relationship between the voltage (V) at its own end and the power (P) input / output to the DC bus 19 follows a reference function having a predetermined droop characteristic in a predetermined control period. Note that the "droop characteristic" means a droop characteristic, and is a characteristic in which the relationship between the voltage at its own end and the input / output amount of power at its own end has a relationship other than a relationship in which the input / output amount of power is constant over a predetermined voltage range or a relationship in which the voltage is constant over a predetermined range of the input / output amount of power.

[0037] As a specific example, as shown in Fig. 2, an AC / DC converter 11 connected to a commercial power system 100 droop controls the input from the commercial power system 100 using a reference function that maximizes the droop characteristic in a normal operation zone so that power can be stably supplied to the power network 10, mainly with power supply from the commercial power system 100, during normal operation of the power network 10. On the other hand, when the power network 10 is in a quasi-normal operation zone or a transient operation zone where power demand is low (in Fig. 2, the upper quasi-normal operation zone and the transient operation zone where the voltage (V) value is high), the power supply from the commercial power system 100 is cut off, and when the power network 10 is in a quasi-normal operation zone or a transient operation zone where power demand is high (in Fig. 2, the lower quasi-normal operation zone and the transient operation zone where the voltage (V) value is low), constant input / output zones (vertical zones in Fig. 2) are provided in which the input / output of power is kept constant so that the power supply from the commercial power system 100 does not exceed the contracted power.

[0038] The first DC / DC converter 13, which converts the DC power input from the DC bus 19 into a charging voltage for the on-board storage battery of the electric vehicle 18 to be charged and outputs it, has a function of controlling the relationship between the voltage (V) at its own end and the power (P) at its own end, i.e., the voltage (V) at its own end and the power (P) input from the DC bus 19, so that they have predetermined characteristics. In other words, the first DC / DC converter 13 has a function of controlling the output of the EV charger 17 so that the relationship between the voltage (V) at its own end and the power (P) input from the DC bus 19 follows a reference function with predetermined characteristics in a predetermined control period.

[0039] As a specific example, as shown in Fig. 2, a first DC / DC converter 13 connected to an EV charger 17 controls the output of the EV charger 17 in a stepwise manner when the power network 10 is in a transient operation zone with high power demand. On the other hand, when the power network 10 is in a quasi-normal operation zone with high power demand, a normal operation zone, a quasi-normal operation zone with low power demand, or a transient operation zone with low power demand, the first DC / DC converter 13 does not control the output of the EV charger 17. In Fig. 2, the reference function that is the control target function of the EV charger 17 is not a reference function having droop characteristics, and the output control of the EV charger 17 is not droop control.

[0040] The bidirectional DC / DC converter 12 connected to the stationary energy storage device 14 has a function of droop controlling the operation of the stationary energy storage device 14 so that the relationship between the voltage (V) at its own end and the power (P) at its own end, i.e., the voltage (V) at its own end and the power (P) charged and discharged from the stationary energy storage device 14, follows a reference function having predetermined droop characteristics. In other words, the bidirectional DC / DC converter 12 controls the relationship between the voltage (V) at its own end and the power (P) at its own end in a predetermined control period so as to maintain a reference function having predetermined droop characteristics.

[0041] 2, the bidirectional DC / DC converter 12 connected to the stationary power storage device 14 provides a dead zone as a constant input / output range so that no charging or discharging occurs in a normal operation zone, and performs droop control so that discharging is performed with a reference function having droop characteristics in a quasi-normal operation zone where power demand is high. Also, the bidirectional DC / DC converter 12 performs droop control so that charging is performed with a reference function having droop characteristics in a quasi-normal operation zone where power demand is low.

[0042] From the above, the power system 1 is configured to follow a predetermined reference function so as to change the output of the photovoltaic power generation device (PV) 15 and the EV charger 17 in response to a change in the voltage of the entire power system 1. Also, in the power system 1, each power element (each device and each power converter connected to each of the devices) performs primary control in a distributed manner based on the voltage at its own end and the power at its own end. In other words, the control of the operation of the device based on the reference function is primary control, and the primary control is performed based on the self-end voltage of each device connected to the power converter.

[0043] Furthermore, the power system 1 further has a secondary control function that updates a reference function according to the power status of multiple power elements. The secondary control is control based on the relationship between the amount of discharge output from the DC bus 19 to which the multiple power elements are electrically connected and the amount of power received by the DC bus 19. In other words, the secondary control is control in which the primary control function of a given power converter is updated to reflect not only the power status of the converter itself but also the power status of other power converters that make up the power system 1.

[0044] 3, in power system 1, in secondary control, a comprehensive judgment is made regarding the reference functions provided in each of the power converters, AC / DC converter 11, bidirectional DC / DC converter 12, first DC / DC converter 13, and second DC / DC converter 16, and the reference functions provided in each of the power converters, AC / DC converter 11, bidirectional DC / DC converter 12, first DC / DC converter 13, and second DC / DC converter 16, are optimally updated. A computer such as an AI (artificial intelligence) can be used to update the reference functions provided in each power converter.

[0045] The secondary control for updating the reference function is performed, for example, based on a command from the central control unit 110. Therefore, the power system 1 further includes a central control unit 110 for controlling each of the power converters, namely, the AC / DC converter 11, the bidirectional DC / DC converter 12, the first DC / DC converter 13, and the second DC / DC converter 16. In the power system 1, the central control unit 110 performs secondary control of the AC / DC converter 11, the bidirectional DC / DC converter 12, the first DC / DC converter 13, and the second DC / DC converter 16. The central control unit 110 and each of the power converters, namely, the AC / DC converter 11, the bidirectional DC / DC converter 12, the first DC / DC converter 13, and the second DC / DC converter 16, are connected, for example, via a communication means. Therefore, the secondary control by the central control unit 110 is a centralized control method. The central control unit 110 is an energy management system (EMS). Note that the primary control and the secondary control are performed, for example, by a program in each power converter or the central control unit 110, which causes a processor to execute the program.

[0046] For example, in the secondary control, when the information communication between the central control unit 110 and each power converter complies with the TCP / IP protocol, the data portion of the IP packet of the command signal for updating the function contains function information of the reference function. For example, when the reference function has droop characteristics, the function information is coordinate information of the boundary of the function (droop function) representing the droop characteristics, intercept information of the droop function, information of the slope (i.e., droop coefficient), and information of the shape (straight line, curve, etc.). The function information also contains information of the constant input / output range. Furthermore, when the reference function does not have droop characteristics, the function information is, for example, in the case of constant voltage control, information indicating constant voltage control, a control target voltage value as a control value, maximum power as a power upper limit value, and minimum power as a power lower limit value, and, for example, in the case of constant power control, information indicating constant power control, a control target power value as a control value, and other information. These pieces of information are, for example, information specified in PV coordinates. The data portion of the IP packet contains information to be updated among these pieces of information as a data string. Function information used for updating is stored in the storage unit of the central control unit 110, and is read and used by the control unit as appropriate.

[0047] In contrast, the primary control for making the reference function track the operation of the photovoltaic power generation device (PV) 15, the EV charger 17, etc. is performed based on the voltages at the respective terminals of the photovoltaic power generation device (PV) 15, the EV charger 17, etc., as described above, without going through commands from the central control unit 110.

[0048] The secondary control for updating the reference function is performed based on commands from the central control unit 110, and the primary control for controlling the input / output of the devices based on the reference function is performed based on the voltages of the self-terminals of the photovoltaic power generation device (PV) 15, the EV charger 17, etc., without via commands from the central control unit 110, so that the required amount of power that varies over time for the entire power network 10 can be accurately reflected in the output control of the photovoltaic power generation device (PV) 15 and the EV charger 17. Therefore, the control of the entire power network 10 equipped with various devices such as the photovoltaic power generation device (PV) 15 and the EV charger 17 is optimized, and the required power can be efficiently supplied to the entire power network 10.

[0049] In the power system 1, when optimizing the control of the entire power network 10 including various devices such as the photovoltaic power generation device (PV) 15 and the EV charger 17, the reference function that controls the operation of the photovoltaic power generation device (PV) 15 has a characteristic that changes, over time, the threshold voltage for output suppression, which is one form of output control of the photovoltaic power generation device (PV) 15. Specifically, the reference function that controls the operation of the photovoltaic power generation device (PV) 15 has a predetermined time-limited characteristic.

[0050] A reference function for controlling the operation of the photovoltaic power generation device (PV) 15 has an inverse time-limited characteristic as a predetermined time-limited characteristic. Specifically, for example, the reference function having the predetermined time-limited characteristic has the relationship of the following formula (1), where Vr is a threshold voltage value, C is a capacitance of a line (DC bus 19 in the power system 1), and Tr is a time constant determined according to the capacitance. Tr = function (Vr, C) (1) Here, function(Vr,C) is a function of Vr and C. For example, in the case of output suppression of the photovoltaic power generation device (PV) 15 in response to a voltage rise of the DC bus 19, function(Vr,C) is set so that Tr becomes shorter as the threshold voltage value Vr for determining whether or not to perform output suppression is higher. Also, function(Vr,C) is set so that Tr can be somewhat longer as the capacitance C of the DC bus 19 becomes larger, because the voltage is less likely to change in response to changes in the amount of current (amount of charge) input / output to the DC bus 19 due to the relationship Q=CV.

[0051] In addition, assuming that the observed voltage at the own end of the second DC / DC converter 16 is V0, when the state of V0>Vr continues for a time Tr (time constant Tr) or more, the switching element of the second DC / DC converter 16 is controlled to suppress the output of power from the photovoltaic power generation device (PV) 15 to the DC bus 19.

[0052] For example, when the observed voltage V0 at its own end of the second DC / DC converter 16 is a voltage V1 that exceeds the threshold voltage value Vr by a predetermined value, if the voltage V1 continues for a time T1 or more with a time constant Tr determined according to the capacitance C, the switching element of the second DC / DC converter 16 suppresses the output of the power P from the photovoltaic power generation device (PV) 15 to the DC bus 19 to be 0. Also, when the observed voltage V0 at its own end of the second DC / DC converter 16 is a voltage V2 that exceeds the voltage V1 by a predetermined value, if the voltage V2 continues for a time T2 or more that is shorter than T1 with the time constant Tr, the switching element of the second DC / DC converter 16 suppresses the output of the power P from the photovoltaic power generation device (PV) 15 to the DC bus 19 to be 0. Furthermore, when the observed voltage V0 at its own end of the second DC / DC converter 16 is a voltage V3 that is higher than the voltage V2 by a predetermined value, if the voltage V3 continues for a time T3 or more that is shorter than T2 with the time constant Tr as the time constant, the switching element of the second DC / DC converter 16 suppresses the output of power P from the photovoltaic power generation device (PV) 15 to the DC bus 19 to 0. In other words, the higher the observed voltage V0, the shorter the time from when the state of V0>Vr is observed until the power output suppression is performed.

[0053] 4, when the observed voltage V0 at the own end of the second DC / DC converter 16 is 420V, which is 20V higher than the threshold voltage value Vr (for convenience of explanation, for example, 400V), if 420V continues for a time T1 (for convenience of explanation, for example, 1.0 second) or more with a time constant Tr, the switching element of the second DC / DC converter 16 suppresses the output of the power P from the photovoltaic power generation device (PV) 15 to the DC bus 19 to 0. Also, when the observed voltage V0 at the own end of the second DC / DC converter 16 is 440V, which is 40V higher than the threshold voltage value Vr (for example, 400V), if 440V continues for a time T2 (for convenience of explanation, for example, 0.1 second) or more with a time constant Tr, the switching element of the second DC / DC converter 16 suppresses the output of the power P from the photovoltaic power generation device (PV) 15 to the DC bus 19 to 0. Furthermore, when the observed voltage V0 at the own end of the second DC / DC converter 16 is 460V that is 60V higher than the threshold voltage value Vr (e.g., 400V), when 460V continues as the time constant Tr for a time T3 or more (for convenience of explanation, for example, 0.01 seconds), the switching element of the second DC / DC converter 16 suppresses the output of power P from the photovoltaic power generation device (PV) 15 to the DC bus 19 to be 0. Note that in Fig. 4, the reference function for controlling the operation of the photovoltaic power generation device (PV) 15 does not have droop characteristics, and therefore the control of the output of the photovoltaic power generation device (PV) 15 is not droop control.

[0054] Moreover, the reference function that controls the operation of the photovoltaic power generation device (PV) 15 has a characteristic that changes, with time, a threshold voltage for output promotion, which is one form of output control of the photovoltaic power generation device (PV) 15. Specifically, the reference function that controls the output promotion operation of the photovoltaic power generation device (PV) 15 has a predetermined time limit characteristic.

[0055] For example, a reference function having a predetermined time-limit characteristic for controlling the output promotion operation of the photovoltaic power generation device (PV) 15 has the relationship of the following equation (2), where the threshold voltage value is Vr2, the capacitance of the line (in the power system 1, the DC bus 19) is C, and the time constant determined according to the capacitance is Tr2. Tr2 = function(Vr2, C) (2) Here, function(Vr2, C) is a function of Vr2 and C. For example, in the case of promoting the output of the photovoltaic power generation device (PV) 15 with respect to the voltage drop of the DC bus 19, function(Vr2, C) is set such that the lower the threshold voltage value Vr2 for determining the implementation of output promotion, the shorter Tr2 becomes. Also, the larger the capacitance C of the DC bus 19, the less likely the voltage is to change with respect to the change in the input / output current amount (charge amount) to / from the DC bus 19 due to the relationship Q = CV. Therefore, function(Vr2, C) is set such that Tr2 may be somewhat longer.

[0056] Also, when the observed voltage at the self-terminal of the second DC / DC converter 16 is V0, when the state of V0 < Vr2 continues for a time Tr2 (time constant Tr2) or more, the switching element of the second DC / DC converter 16 is controlled to promote the output of power from the photovoltaic power generation device (PV) 15 to the DC bus 19.

[0057] For example, when the observed voltage V0 at the self-terminal of the second DC / DC converter 16 is a voltage V11 that is lower than the threshold voltage value Vr2 by a predetermined value, when this range of voltage continues for a time T11 or more as a time constant Tr2 determined according to the capacitance C, the switching element of the second DC / DC converter 16 increases the output of the power P from the photovoltaic power generation device (PV) 15 to the DC bus 19. Also, when the observed voltage V0 at the self-terminal of the second DC / DC converter 16 is a voltage V12 that is lower than the voltage V11 by a predetermined value, when this range of voltage continues for a time T12 or more, which is shorter than T11, as the time constant Tr2, the switching element of the second DC / DC converter 16 increases the output of the power P from the photovoltaic power generation device (PV) 15 to the DC bus 19. Also, when the observed voltage V0 at the self-terminal of the second DC / DC converter 16 is a voltage V13 that is lower than the voltage V12 by a predetermined value, when this range of voltage continues for a time T13 or more, which is shorter than T12, as the time constant Tr2, the switching element of the second DC / DC converter 16 increases the output of the power P from the photovoltaic power generation device (PV) 15 to the DC bus 19. Also, when the observed voltage V0 at the self-terminal of the second DC / DC converter 16 is a voltage V14 or lower that is lower than the voltage V13 by a predetermined value, the switching element of the second DC / DC converter 16 instantaneously increases the output of the power P from the photovoltaic power generation device (PV) 15 to the DC bus 19. That is, the lower the observed voltage V0, the shorter the time from when the state of V0 < Vr2 is observed until the output promotion of the power P is performed. Note that when the switching element of the second DC / DC converter 16 stops increasing the output of the power P when V0 = Vr2 due to the increase in the output of the power P.

[0058] 8, when the observed voltage V0 at the own end of the second DC / DC converter 16 is 400V, which is 5V lower than the threshold voltage value Vr2 (for convenience of explanation, for example, 405V), if the observed voltage V0 at the own end of the second DC / DC converter 16 continues to be 400V or lower for time T11 (for convenience of explanation, for example, 1.0 second) or more with a time constant Tr2 of 400V or lower, the switching element of the second DC / DC converter 16 increases the output of the power P from the photovoltaic power generation device (PV) 15 to the DC bus 19. Also, when the observed voltage V0 at the own end of the second DC / DC converter 16 is 380V, which is 25V lower than the threshold voltage value Vr2, if the observed voltage V0 at the own end of the second DC / DC converter 16 continues to be 380V or lower for time T12 (for convenience of explanation, for example, 0.5 second) or more with a time constant Tr2 of 380V or lower, the switching element of the second DC / DC converter 16 increases the output of the power P from the photovoltaic power generation device (PV) 15 to the DC bus 19. Furthermore, when the observed voltage V0 at its own end of the second DC / DC converter 16 is 360V, which is 45V lower than the threshold voltage value Vr2, if the observed voltage V0 at its own end continues to be 360V or less for time T13 (for convenience of explanation, for example, 0.1 seconds) or more with a time constant Tr2, the switching element of the second DC / DC converter 16 increases the output of power P from the photovoltaic power generation device (PV) 15 to the DC bus 19. Furthermore, when the observed voltage V0 at its own end of the second DC / DC converter 16 is 350V or less, the switching element of the second DC / DC converter 16 instantaneously increases the output of power P from the photovoltaic power generation device (PV) 15 to the DC bus 19. Specifically, for example, if the time count is started when the observed voltage V0 becomes 400V or less, 0.4 seconds pass while the observed voltage V0 is between 380V and 400V, and 0.1 seconds pass while the observed voltage V0 is between 360V and 380V, the total counted time is 0.5 seconds, so the output of the power P from the photovoltaic power generation device (PV) 15 to the DC bus 19 is increased. Also, for example, if the time count is started when the observed voltage V0 becomes 400V or less, 0.8 seconds pass while the observed voltage V0 is between 380V and 400V, and then the observed voltage V0 becomes 380V or less, the total counted time exceeds 0.5 seconds, so the output of the power P from the photovoltaic power generation device (PV) 15 to the DC bus 19 is immediately increased.In addition, in FIG. 8, the reference function for controlling the operation of the photovoltaic power generation device (PV) 15 does not have a droop characteristic, and therefore the control of the output of the photovoltaic power generation device (PV) 15 is not droop control.

[0059] The reference function for controlling the operation of the photovoltaic power generation device (PV) 15 has a characteristic of changing the threshold voltage of the output suppression / output promotion of the photovoltaic power generation device (PV) 15 according to time, specifically, by having a time-limited characteristic, even when a disturbance occurs in the power network 10, the output control of the photovoltaic power generation device (PV) 15 is adjusted according to the degree of voltage fluctuation, and the voltage of the DC bus 19 to which the photovoltaic power generation device (PV) 15 is electrically connected via the second DC / DC converter 16 is stabilized. In addition, by having the time-limited characteristic, the frequency of output suppression / output promotion of the photovoltaic power generation device (PV) 15 can be reduced, and the power efficiency of the photovoltaic power generation device (PV) 15 can be improved.

[0060] In particular, by adding a time-limit characteristic to a reference function for controlling the operation of the photovoltaic power generation device (PV) 15 using a threshold voltage value of the photovoltaic power generation device (PV) 15's own end, the capacitance of the DC bus 19, and a time constant determined according to the capacitance of the DC bus 19, it is possible to more reliably stabilize the voltage of the power network 10 while more reliably improving the power efficiency of the photovoltaic power generation device (PV) 15.

[0061] In addition, when optimizing the control of the entire power network 10 equipped with various devices such as the photovoltaic power generation device (PV) 15 and the EV charger 17, the reference function that controls the operation of the EV charger 17, which is a load, has a characteristic that changes the threshold voltage for output suppression of the EV charger 17 according to time. Specifically, the reference function that controls the operation of the EV charger 17 has a predetermined time limit characteristic.

[0062] Specifically, for example, if a reference function having a predetermined time-limited characteristic has a threshold voltage value of Vr, the capacitance of the line (DC bus 19 in the power system 1) is C, and the time constant determined according to the capacitance is Tr, it has the relationship of the following formula (1). Tr = function(Vr, C) (1) Here, function(Vr, C) is a function of Vr and C, but Vr and function(Vr, C) do not have to be the same as Vr and function(Vr, C) for the photovoltaic power generation device (PV) 15, and the same applies to Tr. For example, in the case of suppressing the output of the EV charger 17 with respect to the voltage drop of the DC bus 19, function(Vr, C) is set so that Tr becomes shorter as the threshold voltage value Vr for determining the implementation of the output suppression is lower. Also, as the capacitance C of the DC bus 19 is larger, the voltage is less likely to change with respect to the change in the input / output current amount (charge amount) to / from the DC bus 19, so function(Vr, C) is set so that Tr may be somewhat longer.

[0063] Also, when the observed voltage at the self-terminal of the first DC / DC converter 13 is V0, when the state of V0 < Vr continues for Tr or more, the switching element of the first DC / DC converter 13 controls to suppress the input of power from the DC bus 19 to the EV charger 17, that is, to suppress the output from the EV charger 17 to the electric vehicle 18.

[0064] For example, when the observed voltage V0 at the own end of the first DC / DC converter 13 is a voltage V4 that is lower than the threshold voltage Vr by a predetermined value, if the voltage V4 continues for a time T4 or more with a time constant Tr determined according to the capacitance C, the switching element of the first DC / DC converter 13 suppresses the input of power P from the DC bus 19 to the EV charger 17 (i.e., the output of power P from the EV charger 17 to the electric vehicle 18). That is, the switching element of the first DC / DC converter 13 suppresses the supply of charging current from the DC bus 19 to the EV charger 17. Also, when the observed voltage V0 at the own end of the first DC / DC converter 13 is a voltage V5 that is lower than the voltage V4 by a predetermined value, if the voltage V5 continues for a time T5 or more that is shorter than T4 with the time constant Tr, the switching element of the first DC / DC converter 13 suppresses the input of power P from the DC bus 19 to the EV charger 17. Furthermore, when the observed voltage V0 at its own end of the first DC / DC converter 13 is a voltage V6 that is lower than the voltage V5 by a predetermined value, if the voltage V6 continues for a time T6 or more that is shorter than T5 with the time constant Tr as the time constant, the switching element of the first DC / DC converter 13 suppresses the input of power P from the DC bus 19 to the EV charger 17. In other words, the higher the observed voltage V0, the shorter the time from when the state of V0>Vr is observed until the power input is suppressed.

[0065] As a specific example, when the observed voltage V0 at the own end of the first DC / DC converter 13 is 340V, which is 20V lower than the threshold voltage value Vr (for convenience of explanation, for example, 360V), if 340V continues for a time T4 (for convenience of explanation, for example, 1.0 second) or more with a time constant Tr, the switching element of the first DC / DC converter 13 suppresses the input of power P from the DC bus 19 to the EV charger 17, i.e., the supply amount of charging current. Also, when the observed voltage V0 at the own end of the first DC / DC converter 13 is 320V, which is 40V lower than the threshold voltage value Vr (for example, 360V), if 320V continues for a time T5 (for convenience of explanation, for example, 0.1 second) or more with a time constant Tr, the switching element of the first DC / DC converter 13 suppresses the input of power P from the DC bus 19 to the EV charger 17. Furthermore, when the observed voltage V0 at its own end of the first DC / DC converter 13 is 300V, which is 60V lower than the threshold voltage value Vr (e.g., 360V), if 300V continues as the time constant Tr for a time T6 or more (for convenience of explanation, for example, 0.01 seconds), the switching element of the first DC / DC converter 13 suppresses the input of power P from the DC bus 19 to the EV charger 17. The reference function for controlling the operation of the EV charger 17 does not have droop characteristics, and therefore the control of the input to the EV charger 17 is not droop control.

[0066] Furthermore, the reference function that controls the operation of the EV charger 17 has a characteristic that changes the threshold voltage of the output boost of the EV charger 17 according to time. Specifically, the reference function that controls the operation of the EV charger 17 has a predetermined time-limited characteristic.

[0067] Specifically, for example, a reference function having a predetermined time-limit characteristic has the relationship of the following equation (3), where the threshold voltage value is Vr3, the capacitance of the line (in the power system 1, the DC bus 19) is C, and the time constant determined according to the capacitance is Tr3. Tr3 = function (Vr3, C) (3) Here, function(Vr3, C) is a function of Vr3 and C. For example, in the case of output promotion of the EV charger 17 in response to a voltage rise of the DC bus 19, function(Vr3, C) is set so that Tr3 is shorter as the threshold voltage value Vr3 for determining whether or not to perform output promotion is larger. Also, function(Vr3, C) is set so that Tr3 may be somewhat longer since the voltage is less likely to change in response to changes in the amount of current (amount of charge) input / output to the DC bus 19 as the capacitance C of the DC bus 19 is larger.

[0068] Furthermore, if the observed voltage at the own end of the first DC / DC converter 13 is V0, when the state of V0>Vr3 continues for Tr3 or longer, the switching element of the first DC / DC converter 13 is controlled to promote input from the DC bus 19 to the EV charger 17, i.e., to promote output from the EV charger 17 to the electric vehicle 18.

[0069] For example, when the observed voltage V0 at the own end of the first DC / DC converter 13 is a voltage V15 that exceeds the threshold voltage value Vr3 by a predetermined value, if the voltage in this range continues for a time T14 or more with a time constant Tr3 determined according to the capacitance C, the switching element of the first DC / DC converter 13 increases the output of the power P from the DC bus 19 to the EV charger 17 (i.e., the output of the power P from the EV charger 17 to the electric vehicle 18). That is, the switching element of the first DC / DC converter 13 increases the supply of the charging current from the DC bus 19 to the EV charger 17. Also, when the observed voltage V0 at the own end of the first DC / DC converter 13 is a voltage V16 that exceeds the voltage V15 by a predetermined value, if the voltage in this range continues for a time T15 or more that is shorter than T14 with a time constant Tr3 determined according to the capacitance C, the switching element of the first DC / DC converter 13 increases the output of the power P from the DC bus 19 to the EV charger 17. Furthermore, when the observed voltage V0 at its own end of the first DC / DC converter 13 is a voltage V17 that exceeds the voltage V16 by a predetermined value, if this range of voltages continues for a time T16 or more that is shorter than T15 with the time constant Tr3 determined according to the capacitance C, the switching element of the first DC / DC converter 13 increases the output of the power P from the DC bus 19 to the EV charger 17. Furthermore, when the observed voltage V0 at its own end of the first DC / DC converter 13 is a voltage V18 or more that exceeds the voltage V17 by a predetermined value, the switching element of the first DC / DC converter 13 instantaneously increases the output of the power P from the DC bus 19 to the EV charger 17. In other words, the higher the observed voltage V0, the shorter the time from when the state of V0>Vr3 is observed until the power output is promoted.

[0070] 9, when the observed voltage V0 at the own end of the first DC / DC converter 13 is 350V, which is 5V higher than the threshold voltage value Vr3 (for convenience of explanation, for example, 345V), if the observed voltage V0 at the own end of the first DC / DC converter 13 continues to be 350V or higher for a time T14 (for convenience of explanation, for example, 1.0 second) or more with a time constant Tr3, the switching element of the first DC / DC converter 13 increases the input of power P from the DC bus 19 to the EV charger 17, i.e., the supply amount of charging current. Also, when the observed voltage V0 at the own end of the first DC / DC converter 13 is 360V, which is 15V higher than the threshold voltage value Vr3, if the observed voltage V0 at the own end of the first DC / DC converter 13 continues to be 360V or higher for a time T15 (for convenience of explanation, for example, 0.5 second) or more with a time constant Tr3, the switching element of the first DC / DC converter 13 increases the input of power P from the DC bus 19 to the EV charger 17. Furthermore, when the observed voltage V0 at the own end of the first DC / DC converter 13 is 370V, which is 25V higher than the threshold voltage value Vr3, if the observed voltage V0 at the own end of the first DC / DC converter 13 continues to be 370V or higher for a time T16 (for convenience of explanation, for example, 0.1 seconds) or more with a time constant Tr3, the switching element of the first DC / DC converter 13 increases the input of power P from the DC bus 19 to the EV charger 17. Furthermore, when the observed voltage V0 at the own end of the first DC / DC converter 13 is 380V or higher, which is 35V higher than the threshold voltage value Vr3, the switching element of the first DC / DC converter 13 instantaneously increases the input of power P from the DC bus 19 to the EV charger 17. The reference function for controlling the operation of the EV charger 17 does not have a droop characteristic, so the control of the output of the EV charger 17 is not droop control.

[0071] In addition, as a method for a reference function having a time-limited characteristic to limit the input to the EV charger 17, for example, a method of suppressing the amount of charging current to the EV charger 17 is exemplified. In a case where multiple EV chargers 17 are provided, a method of maintaining the amount of charging current to some of the EV chargers 17 at a steady state while cutting off the supply of charging current to the other EV chargers 17 is exemplified.

[0072] The reference function for controlling the operation of the EV charger 17, which is a load, has a characteristic of changing the threshold voltage of the input suppression / input promotion to the EV charger 17 according to time, specifically, by having a time-limited characteristic, even when a disturbance occurs in the power network 10, the input control to the EV charger 17 is adjusted according to the degree of voltage fluctuation, and the voltage of the DC bus 19 to which the EV charger 17 is electrically connected via the first DC / DC converter 13 is stabilized. In addition, by having the above-mentioned time-limited characteristic, the frequency of input suppression / input promotion to the EV charger 17 (i.e., output suppression / output promotion from the EV charger 17 to the electric vehicle 18) can be reduced, thereby improving the power efficiency of the EV charger 17.

[0073] In particular, by adding a time-limited characteristic to the reference function for controlling the operation of EV charger 17 using the threshold voltage value of its own end, the capacitance of DC bus 19, and a time constant determined according to the capacitance of DC bus 19, it is possible to more reliably stabilize the voltage of the power network 10 while more reliably improving the power efficiency of EV charger 17 receiving power.

[0074] Next, a description will be given of specific configuration examples of power converters such as the first DC / DC converter 13 and the second DC / DC converter 16. Here, the second DC / DC converter 16 will be described as an example.

[0075] As shown in FIG. 5, the power converter (second DC / DC converter 16) includes an input unit 16a electrically connected to a device (a photovoltaic power generation device (PV) 15 in FIG. 5) capable of inputting power from a line (DC bus 19) and / or outputting power to the line, a voltage fluctuation unit 16b which is a switching element that fluctuates the voltage and is connected to the input unit 16a, a voltage adjustment unit 16c which is connected to the voltage fluctuation unit 16b and the line and adjusts the voltage to the line, a target setting unit 16d which determines a first target value of the voltage fluctuation unit 16b, a voltage monitoring unit 16g which is connected to the line and observes the line voltage, and a threshold value determination mechanism 16e which is connected to the voltage monitoring unit 16g and the target setting unit 16d and calculates a second target value of the voltage adjustment unit 16c according to the line voltage. The threshold value determination mechanism 16e functions as a determination unit which determines the presence or absence of an abnormality in the voltage value observed by the voltage monitoring unit 16g. A memory 16f is also connected to the threshold value determination mechanism 16e. The memory 16f is a storage means that stores a table showing the relationship between a voltage (voltage magnitude, duration of voltage) that exceeds or falls below the aforementioned threshold voltage value by a predetermined value and the time constant Tr of the voltage.

[0076] The second DC / DC converter 16 has a characteristic in which the target setting unit 16d generates a first target value as an output target of the voltage fluctuation unit 16b in response to the voltage of the DC bus 19 line observed by the voltage monitoring unit 16g, and this first target value changes the threshold voltage for output suppression of the voltage adjustment unit 16c in response to time.

[0077] That is, the reference function, which is a control target function, generates a first target value for self-end control of the equipment (photovoltaic power generation device 15) in accordance with the voltage of the line (DC bus 19) observed by the voltage monitoring unit 16g, and the second DC / DC converter 16 controls the photovoltaic power generation device 15 based on the reference function.

[0078] The input unit 16a includes, for example, an electric terminal. The voltage fluctuation unit 16b and the voltage adjustment unit 16c correspond to a power conversion unit having a power conversion function. The target setting unit 16d, the threshold determination mechanism 16e, and the memory 16f correspond to a control unit for controlling the power conversion function. The voltage monitoring unit 16g corresponds to a sensor used to observe electrical characteristics.

[0079] (Control method for power systems) Next, an example of a control method for a power system as centralized control will be described with reference to a sequence diagram of FIG.

[0080] First, in step S201, the central control unit 110 calls its own timer and starts timing. Then, in step S202, the central control unit 110 requests each power converter to transmit its own-end measurement information. The own-end measurement information is an example of information related to the power status of the power system 1, and includes the measurement value measured by the sensor of each power converter and the measurement time.

[0081] Next, in step S203, each power converter transmits its own-end measurement information to the central control unit 110. The central control unit 110 stores the respective own-end measurement information in a storage unit.

[0082] Next, in step S204, the central control unit 110 requests various pieces of information that may affect the operation of the power system 1 from the external server 200, as an example of information on the power situation of the power system 1. In this example, the central control unit 110 requests power generation and demand forecast information from the external server 200. The power generation and demand forecast information includes forecast information on the amount of power generation in the power system 1 and forecast information on the demand for power, and may include, for example, information on the season of the area in which the power system 1 is installed, the current weather, and future weather forecasts. In addition, when the external server 200 functions as an EMS for another power system, and when the operational state of the other power system may affect the operation of the power system 1, the power generation and demand forecast information may include forecast information on the amount of power generation and the demand for power in the other power system.

[0083] Next, in step S205, the external server 200 transmits the power generation amount / demand forecast information to the central control unit 110. The central control unit 110 stores the power generation amount / demand forecast information in the storage unit.

[0084] Next, in step S206, the control unit of the central control unit 110 reads out each piece of transmitted information, i.e., information related to the power situation of the power system 1, from the memory unit, and performs operational optimization calculations for the power system 1 based on this.

[0085] The operation optimization calculation is executed so as to be applicable to various conditions. For example, it is assumed that the power system 1 is controlled so that the DC bus 19 is at an operating point of a predetermined voltage. In this state, it is assumed that the central control unit 110 determines that the future weather in the area where the photovoltaic power generation device 15 is installed is expected to be sunny and the amount of power generation is expected to increase, based on the power generation amount and demand forecast information, and that the photovoltaic power generation device 15 has a margin in terms of power supply, based on the self-terminal measurement information acquired from the second DC / DC converter 16 connected to the photovoltaic power generation device 15. In this case, the central control unit 110 determines to update the reference function of the bidirectional DC / DC converter 12 connected to the stationary power storage device 14 so that the stationary power storage device 14 is charged at the operating point. In addition, the central control unit 110 determines to update the reference function of the AC / DC converter 11 so that power is not supplied from the commercial power system 100 at the same time as the update. Note that the reference function may be switched instead of being updated.

[0086] In addition, the operation optimization calculation can also be performed with conditions set from the perspective of not exceeding the contracted power of the commercial power system 100, such as peak cutting and utilization of nighttime power, and from the perspective of optimizing electricity rates.

[0087] Furthermore, the storage unit of the central control unit 110 may store a trained model, and the central control unit 110 may execute the operation optimization calculation using the trained model. The trained model may be, for example, a trained model generated by deep learning using a neural network, using information on the power situation of the power system 1 and the corresponding results of updating the reference function for each power converter as teacher data.

[0088] Next, in step S207, the central control unit 110 outputs an update command for the reference function to the power converter to be updated among the power converters, and executes the update step. Next, in step S208, the central control unit 110 resets the timer. Next, in step S209, each power converter executes its own end control. This own end control is the own end control that reflects the power situation of the power system 1, and all the power converters are controlled in a coordinated manner.

[0089] Next, other embodiments of the power converter and power system of the present invention will be described. In the power converter and power system of the above embodiment, a photovoltaic power generation device (PV) 15 is provided as a power generation device using a reference function with a time-limited characteristic, but instead of this, a power generation device that generates power using fuel may be used. In addition, in the power converter and power system of the above embodiment, an EV charger 17 is provided as a load, but instead of or together with the EV charger 17, another load such as a house (for example, load L shown in FIG. 5) may be provided, and the other load may be connected to the AC / DC converter 11.

[0090] In the power converter and power system of the above embodiments, the reference function with the time-limit characteristic is configured to change the amount of power input and output at the own end in response to changes in the voltage at the own end. Alternatively, the reference function may be configured to change the amount of current input and output at the own end in response to changes in the voltage at the own end.

[0091] In addition, as a method for making the relationship between the voltage at its own end and the power at its own end follow a reference function with a time-limited characteristic, for example, a method in which a power converter observes the voltage at its own end, sets a target value of power from the reference function, and makes the power follow the target value of power may be used, or a method in which a power converter observes the power at its own end, sets a target value of voltage from the reference function, and makes the voltage follow the target value of voltage may be used.

[0092] Furthermore, in the power system of the above embodiment, other power converters than the second DC / DC converter 16 connected to the photovoltaic power generation device (PV) 15 as a power generation device and / or the first DC / DC converter 13 connected to the EV charger 17 as a load also control the operation of the equipment to follow a reference function that generates a target value for self-end control of equipment connected to the other power converter in accordance with the voltage observed by the other power converter, but instead, the control by the other power converters than the second DC / DC converter 16 and / or the first DC / DC converter 13 does not have to be control based on a reference function.

[0093] In the power system of the above embodiment, a central control unit 110 is separately provided, and the central control unit 110 centrally performs the update of the reference function, which is the secondary control, but instead, the secondary control by the central control unit does not have to be performed. In the power system of the above embodiment, the central control unit centrally performs the secondary control, but instead, at least one of the multiple power converters may be configured to have a function as a central control unit that controls the multiple power converters. [Industrial Applicability]

[0094] The power converter and power system of the present invention can stabilize voltage even when a disturbance occurs in the power network while improving the power efficiency of the devices that make up the power network, and are therefore particularly useful in the field of DC grids that have locally produced and consumed power networks. [Explanation of symbols]

[0095] 1. Power System 10. Electricity Network 11 AC / DC converter 12 Bidirectional DC / DC converter 13 First DC / DC converter 14 Stationary energy storage device 15. Solar power generation equipment 16 Second DC / DC converter 16a Input section 16b Voltage fluctuation section 16c Voltage regulator 16d Goal setting section 16e Threshold Judgment Mechanism 16f Memory 16g Voltage monitoring unit 17 EV charger 19 DC Bus

Claims

1. A power converter connected to a power transmission line, an input unit electrically connected to a device capable of inputting electric power from the power transmission line and / or outputting electric power to the power transmission line; A voltage fluctuation unit that is connected to the input unit and that fluctuates a voltage; a voltage adjustment unit connected to the voltage fluctuation unit and adjusting a voltage to the power transmission line; a target setting unit that determines a first target value of the voltage fluctuation unit; a voltage monitoring unit connected to the power transmission line and configured to monitor a voltage of the power transmission line; a threshold determination mechanism connected to the voltage monitoring unit and configured to calculate a second target value of the voltage adjusting unit in response to a voltage of the power transmission line; Equipped with the target setting unit of the power converter generates the first target value as an output target of the voltage fluctuation unit in response to a voltage observed by the voltage monitoring unit; The power converter has a characteristic in which the first target value changes a threshold voltage of output control of the voltage adjusting unit according to time.

2. The power converter according to claim 1 , wherein the device is controlled based on a reference function that generates the first target value when performing self-end control of the device, in response to the voltage observed by the voltage monitoring unit.

3. 3. The power converter of claim 2, wherein the reference function has a predetermined time-limited characteristic.

4. The reference function is expressed by the following equation (1), where Vr is a threshold voltage value, C is the capacitance of the power transmission line, and Tr is a time constant determined according to the capacitance. Tr=function(Vr,C) (1) The relationship is as follows:

4. The power converter according to claim 2, wherein when an observed voltage at a terminal of the power converter is V0, and a state in which V0>Vr continues for Tr or more, the voltage fluctuation unit controls to suppress the output of power from the device to the power transmission line.

5. The reference function is expressed by the following equation (1), where Vr is a threshold voltage value, C is the capacitance of the power transmission line, and Tr is a time constant determined according to the capacitance. Tr=function(Vr,C) (1) The relationship is as follows:

5. The power converter according to claim 2, wherein when an observed voltage at a terminal of the power converter is V0, when a state in which V0<Vr continues for Tr or more, the voltage fluctuation unit promotes the output of power from the device to the power transmission line, and when V0 reaches Vr, the output promotion is stopped.

6. 6. The power converter according to claim 4, wherein the device is a power generation device.

7. The power converter according to claim 6 , wherein the power generation device is a power generation device that generates power using renewable energy or a power generation device that generates power using fuel.

8. The reference function is expressed by the following equation (1), where Vr is a threshold voltage value, C is the capacitance of the power transmission line, and Tr is a time constant determined according to the capacitance. Tr=function(Vr,C) (1) The relationship is as follows:

3. The power converter according to claim 2, wherein when an observed voltage at a terminal of the power converter is V0, and a state in which V0<Vr continues for Tr or more, the voltage fluctuation unit controls to suppress the input of power from the transmission line to the device.

9. The reference function is expressed by the following equation (1), where Vr is a threshold voltage value, C is the capacitance of the power transmission line, and Tr is a time constant determined according to the capacitance. Tr=function(Vr,C) (1) The relationship is as follows:

9. The power converter according to claim 2 or 8, wherein when an observed voltage at a terminal of the power converter is V0, when a state in which V0>Vr continues for Tr or more, the voltage fluctuation unit promotes the input of power from the transmission line to the device, and when V0 reaches Vr, the input promotion is stopped.

10. The power converter according to claim 8 or 9, wherein the device is a load.

11. The power converter according to claim 10 , wherein the load is an EV charger for charging an on-board storage battery mounted in an electric vehicle.

12. A power element is provided, the power element including a power converter and a device electrically connected to the power converter; an input unit electrically connected to a device capable of receiving power from a power transmission line and / or outputting power to the power transmission line; A voltage fluctuation unit that is connected to the input unit and that fluctuates a voltage; a voltage adjustment unit connected to the voltage fluctuation unit and adjusting a voltage to the power transmission line; a target setting unit that determines a first target value of the voltage fluctuation unit; a voltage monitoring unit connected to the power transmission line and configured to monitor a voltage of the power transmission line; a threshold determination mechanism connected to the voltage monitoring unit and configured to calculate a second target value of the voltage adjusting unit in response to a voltage of the power transmission line; A power system comprising: the target setting unit of the power converter generates the first target value as an output target of the voltage fluctuation unit in response to a voltage observed by the voltage monitoring unit; A power system in which the first target value has a characteristic that causes a threshold voltage of output control of the voltage regulator to change over time.

13. The power system according to claim 12 , further comprising a function of controlling the device based on a reference function that generates the first target value when performing self-end control of the device in response to the voltage observed by the voltage monitoring unit.

14. The power system of claim 13 , wherein the reference function has a predetermined time-limited characteristic.

15. The reference function is expressed by the following equation (1), where Vr is a threshold voltage value, C is the capacitance of the power transmission line, and Tr is a time constant determined according to the capacitance. Tr=function(Vr,C) (1) The relationship is as follows:

15. The power system according to claim 13 or 14, wherein when an observed voltage at the own end of the power converter is V0, and a state of V0>Vr continues for Tr or more, the voltage fluctuation unit controls to suppress the output of power from the device to the power transmission line.

16. The reference function is expressed by the following equation (1), where Vr is a threshold voltage value, C is the capacitance of the power transmission line, and Tr is a time constant determined according to the capacitance. Tr=function(Vr,C) (1) The relationship is as follows:

16. The power system according to claim 13, wherein when an observed voltage at a terminal of the power converter is V0, when a state in which V0<Vr continues for Tr or more, the voltage fluctuation unit promotes the output of power from the device to the power transmission line, and when V0 reaches Vr, the output promotion is stopped.

17. The power system according to claim 15 or 16, wherein the device is a power generation device.

18. The power system according to claim 17 , wherein the power generation device is a power generation device that generates power using renewable energy or a power generation device that generates power using fuel.

19. The reference function is expressed by the following equation (1), where Vr is a threshold voltage value, C is the capacitance of the power transmission line, and Tr is a time constant determined according to the capacitance. Tr=function(Vr,C) (1) The relationship is as follows:

14. The power system according to claim 13, wherein when an observed voltage at a terminal of the power converter is V0, and a state in which V0<Vr continues for Tr or more, the voltage fluctuation unit controls to suppress an input of power from the transmission line to the device.

20. The reference function is expressed by the following equation (1), where Vr is a threshold voltage value, C is the capacitance of the power transmission line, and Tr is a time constant determined according to the capacitance. Tr=function(Vr,C) (1) The relationship is as follows:

20. The power system according to claim 13 or 19, wherein when an observed voltage at a terminal of the power converter is V0, when a state in which V0>Vr continues for Tr or more, the voltage fluctuation unit promotes the input of power from the transmission line to the device, and when V0 reaches Vr, the input promotion is stopped.

21. The power system according to claim 19 or 20, wherein the device is a load.

22. 22. The power system according to claim 21, wherein the load is an EV charger for charging an on-board storage battery mounted in an electric vehicle.

23. 23. The power system of claim 12, wherein the transmission line is a DC bus.

24. A control method for a power converter connected to a power transmission line and having an input unit connected to a device capable of receiving power from the power transmission line and / or outputting power to the power transmission line, comprising: A voltage fluctuation unit connected to the input unit fluctuates a voltage; A voltage adjusting unit connected to the voltage fluctuation unit adjusts a voltage to the power transmission line; determining a first target value of the voltage fluctuation unit; Observing a voltage of the power transmission line; calculating a second target value of the voltage adjusting unit in response to the observed voltage of the power transmission line; Equipped with generating the first target value as an output target of the voltage fluctuation unit in response to the observed voltage of the power transmission line; A method for controlling a power converter, wherein the first target value has a characteristic that causes a threshold voltage of output control of the voltage adjusting unit to change with time.

25. A power element is provided, the power element including a power converter and a device electrically connected to the power converter; A control method for a power system, the power converter being connected to a power transmission line, and an input unit of the power converter being connected to an apparatus capable of inputting power from the power transmission line and / or outputting power to the power transmission line, comprising: A voltage fluctuation unit connected to the input unit fluctuates a voltage; A voltage adjusting unit connected to the voltage fluctuation unit adjusts a voltage to the power transmission line; determining a first target value of the voltage fluctuation unit; Observing a voltage of the power transmission line; calculating a second target value of the voltage adjusting unit in response to the observed voltage of the power transmission line; Equipped with generating the first target value as an output target of the voltage fluctuation unit in response to the observed voltage of the power transmission line; A method for controlling a power system, wherein the first target value has a characteristic of changing a threshold voltage of output control of the voltage regulator according to time.

26. A power element is provided, the power element including a power converter and a device electrically connected to the power converter; The power converter is connected to a power transmission line, and an input unit of the power converter is connected to the device capable of inputting power from the power transmission line and / or outputting power to the power transmission line, A control method for a power system including the power converter and a central control device capable of communicating with an external server that holds power demand information, A voltage fluctuation unit connected to the input unit fluctuates a voltage; A voltage adjusting unit connected to the voltage fluctuation unit adjusts a voltage to the power transmission line; determining a first target value of the voltage fluctuation unit; Observing a voltage of the power transmission line; calculating a second target value of the voltage adjusting unit in response to the observed voltage of the power transmission line; acquiring the demand information from the external server; Equipped with generating the first target value as an output target of the voltage fluctuation unit in response to the observed voltage of the power transmission line; A method for controlling a power system, wherein the first target value has a characteristic of changing a threshold voltage of output control of the voltage regulator according to time.

27. The processor: A program for executing a control method for a power converter connected to a power transmission line and having an input unit connected to a device capable of inputting power from the power transmission line and / or outputting power to the power transmission line, the program comprising: A voltage fluctuation unit connected to the input unit fluctuates a voltage; A voltage adjusting unit connected to the voltage fluctuation unit adjusts a voltage to the power transmission line; determining a first target value of the voltage fluctuation unit; Observing a voltage of the power transmission line; calculating a second target value of the voltage adjusting unit in response to the observed voltage of the power transmission line; Equipped with generating the first target value as an output target of the voltage fluctuation unit in response to the observed voltage of the power transmission line; The first target value has a characteristic of changing a threshold voltage of the output control of the voltage adjusting unit according to time. program.

28. The processor: A program for executing a control method for a power system in which a power element including a power converter and a device electrically connected to the power converter is provided, the power converter is connected to a power transmission line, and an input unit of the power converter is connected to the device capable of inputting power from the power transmission line and / or outputting power to the power transmission line, A voltage fluctuation unit connected to the input unit fluctuates a voltage; A voltage adjusting unit connected to the voltage fluctuation unit adjusts a voltage to the power transmission line; determining a first target value of the voltage fluctuation unit; Observing a voltage of the power transmission line; calculating a second target value of the voltage adjusting unit in response to the observed voltage of the power transmission line; Equipped with generating the first target value as an output target of the voltage fluctuation unit in response to the observed voltage of the power transmission line; The first target value has a characteristic of changing a threshold voltage of the output control of the voltage adjusting unit according to time. program.

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