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

Abstract

Provided is a power system in which a plurality of power elements are provided, each element comprising: a power converter electrically connected to a commercial AC power grid; and a device electrically connected to the power converter. The power system comprises a control unit that executes primary control on the basis of a reference function having droop characteristics for generating a target value for self-end control of the device by the electric converter in accordance with a voltage measured at the power converter. The power system has a function of secondary control for updating the reference function having the droop characteristics in accordance with a power situation of the plurality of power elements. A control cycle of the primary control and a control cycle of the secondary control differ.

Description

[Technical field]

[0001] The present invention relates to a power system having a plurality of devices that are controlled to follow a reference function having droop characteristics in accordance with the voltage and current measured by the power converter, and in particular to a power converter that is hierarchically controlled using primary control in which each device is controlled to follow a reference function based on the voltage and current at its own end, and secondary control in which the reference function is updated, and a power system that is equipped with such a 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, including photovoltaic power generation devices (PV), which are power generation devices that generate electricity using renewable energy, stationary power storage devices, and electric vehicles (EVs). Since each of the above devices uses a direct current (DC) power source, studies are underway to build a direct current (DC) power network (DC grid).

[0003] Conventionally, as a method of controlling a DC grid, a power converter connected to each of the above devices performs constant current control or constant voltage control on each of the above devices based on an instruction from a central control unit, thereby centrally controlling the amount of power on the DC bus of the DC grid. Although the above centralized control method can easily control the entire DC grid, it has a problem that it is difficult to smoothly respond to sudden fluctuations in power supply and demand. In addition, the above centralized control method has a possibility of unstable voltage control, causing voltage oscillations on the DC bus, especially when constant voltage control is performed at multiple locations over a wide range. In addition, constant voltage control at multiple locations has a problem that it is not possible to share the load of power interchange among the devices, that is, the devices cannot cooperate to supply power to the DC bus at a constant voltage according to the power supply capacity of each device.

[0004] Thus, a reference function based on the power (P) and voltage (V) of the own end is given to each device, and the reference function has a droop characteristic that causes each device to have a droop characteristic in the target voltage value according to the amount of power required for the DC bus, and the DC grid is controlled by controlling each device in an autonomous and decentralized manner using droop control (Patent Document 1, Patent Document 2). By controlling each device in an autonomous and decentralized manner using droop control, the voltage of the DC bus can be stabilized while sharing the load of power interchange of each device according to the amount of power required for the DC bus. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6371603 [Patent Document 2] International Publication No. 2019 / 103059 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in conventional droop control such as those disclosed in Patent Documents 1 and 2, the reference function having droop characteristics is updated in an autonomous and decentralized manner based on the self-end information of each device. Therefore, in conventional droop control, the autonomous and decentralized control of each device and the update of the reference function are not hierarchical, and there was a need for improvement in terms of efficiently supplying the required power to the entire DC grid.

[0007] In view of the above circumstances, the present invention aims to provide a power converter that improves control of the entire power network by accurately reflecting the amount of power required by the entire power network, which varies over time, in the control of each device, and that can efficiently supply the required power to the entire power network, as well as a power system including such a power converter, a control method for a power converter, and a control method and program for a power system. [Means for solving the problem]

[0008] The gist of the configuration of the present invention is as follows. [1] A power converter that is electrically connected to an AC commercial power system and is electrically connected to equipment capable of inputting and / or outputting power, the power converter includes a control unit that executes primary control of the device based on a reference function having a droop characteristic that generates a target value when performing self-end control of the device in response to a voltage measured by the power converter; The power converter is further controlled by a secondary control in which a reference function having the droop characteristic is updated according to a power condition of a power system in which the power converter is provided; A power converter in which a control period of the primary control is different from a control period of the secondary control. [2] The power converter according to [1], wherein the power system further has a central control unit that controls the multiple power converters, and the secondary control is performed based on a command from the central control unit. [3] A power converter as described in [1] or [2], wherein the primary control is performed based on the voltage at the device's own end, without going through the instructions of a central control unit that controls the multiple power converters. [4] A power converter as described in any one of [1] to [3], wherein the reference function having the droop characteristic is configured to change the amount of power or current input or output in response to changes in voltage. [5] A power converter as described in any one of [1] to [4], wherein the secondary control includes updating a reference function having the droop characteristic so that the power of the equipment is constant. [6] A power converter according to any one of [1] to [5], wherein the primary control is performed based on the voltage at the device's own end, and the secondary control is controlled based on the relationship between the amount of power discharged from a line connected to the power converter and the amount of power received by the line. [7] The power converter according to any one of [1] to [6], wherein a control period of the secondary control is longer than a control period of the primary control. [8] The power converter according to any one of [1] to [7], which is a DC / DC converter. [9] A power converter as described in [2], wherein, instead of the central control unit, at least one of the multiple power converters is configured to have the function of a central control unit that controls the multiple power converters.

[10] A plurality of power elements are provided, each of which includes a power converter electrically connected to an AC commercial power system and a device electrically connected to the power converter; a control unit that performs primary control based on a reference function having a droop characteristic that generates a target value when performing self-end control of the device in accordance with a voltage measured by the power converter, The power system has a function of secondary control for updating a reference function having the droop characteristic in response to power conditions of the plurality of power elements, A power system in which a control period of the primary control and a control period of the secondary control are different from each other.

[11] The power system described in

[10] , further comprising a central control unit that controls the plurality of power converters, and the secondary control is performed based on the command of the central control unit.

[12] The power system according to

[10] or

[11] , wherein the primary control is performed based on the voltage at the device's own end, without going through the command of a central control unit that controls the multiple power converters.

[13] The power system of any one of

[10] to

[12] , wherein the reference function having the droop characteristic is configured to change the amount of power or current input or output in response to changes in voltage.

[14] A power system according to any one of

[10] to

[13] , wherein the secondary control includes updating a reference function having droop characteristics performed so that the power of the equipment of the power element is constant.

[15] A power system described in any one of

[10] to

[14] , wherein the primary control is performed based on the voltage at the local end of each of the devices, and the secondary control is controlled based on the relationship between the amount of power discharged from a line to which the multiple power elements are electrically connected and the amount of power received by the line.

[16] The power system according to any one of

[10] to

[15] , wherein the control period of the secondary control is longer than the control period of the primary control.

[17] The power system according to any one of

[10] to

[16] , wherein the line to which the plurality of power elements are electrically connected is a DC bus.

[18] The power system described in

[11] , wherein, instead of the central control unit, at least one of the multiple power converters is configured to have the function of a central control unit that controls the multiple power converters.

[19] A method for controlling a power converter electrically connected to an AC commercial power system and electrically connected to a device capable of inputting and / or outputting power, comprising: a primary control step of controlling the device based on a reference function having a droop characteristic that generates a target value when controlling the device at its own end in response to the measured voltage of the power converter; The power converter is further controlled by a secondary control in which a reference function having the droop characteristic is updated according to a power condition of a power system in which the power converter is provided; Equipped with The control period of the primary control is different from the control period of the secondary control. A method for controlling a power converter.

[20] A method for controlling a power system including a plurality of power elements each including a power converter electrically connected to an AC commercial power system and a device electrically connected to the power converter, comprising: performing a primary control based on a reference function having a droop characteristic that generates a target value when performing a self-end control of the device in response to a measured voltage of the power converter; performing a secondary control to update a reference function having the droop characteristic in response to power conditions of a plurality of the power elements; Equipped with The control period of the primary control is different from the control period of the secondary control. Power system control methods.

[21] A method for controlling a power system including a central control device capable of communicating with an external server that holds information on the power converters and power demand, the method comprising: providing a plurality of power elements each including a power converter electrically connected to an AC commercial power system and a device electrically connected to the power converter; and performing a primary control based on a reference function having a droop characteristic that generates a target value when performing a self-end control of the device in response to a measured voltage of the power converter; acquiring the demand information from the external server; executing a secondary control to update a reference function having the droop characteristic according to the power status of a plurality of the power elements and the demand information; Equipped with The control period of the primary control is different from the control period of the secondary control. Power system control methods.

[22] The processor: A program for executing a control method for a power converter electrically connected to an AC commercial power system and electrically connected to a device capable of inputting and / or outputting power, a primary control step of controlling the device based on a reference function having a droop characteristic that generates a target value when controlling the device at its own end in response to the measured voltage of the power converter; The power converter is further controlled by a secondary control in which a reference function having the droop characteristic is updated according to a power condition of a power system in which the power converter is provided; Equipped with The control period of the primary control is different from the control period of the secondary control. program.

[23] The processor: A program for executing a control method for a power system including a plurality of power elements each including a power converter electrically connected to an AC commercial power system and a device electrically connected to the power converter, the program comprising: performing a primary control based on a reference function having a droop characteristic that generates a target value when performing a self-end control of the device in response to a measured voltage of the power converter; performing a secondary control to update a reference function having the droop characteristic in response to power conditions of a plurality of the power elements; Equipped with The control period of the primary control is different from the control period of the secondary control. program. Effect of the Invention

[0009] According to the aspects of the power converter and the power system including the power converter of the present invention, the power converter has a function of primary control based on a reference function having a droop characteristic for generating a target value for controlling a device connected to the power converter at its own end according to a voltage measured by the power converter, and a function of secondary control for updating the reference function having the droop characteristic according to the power conditions of the plurality of power elements, and by having a hierarchical control in which the control period of the primary control and the control period of the secondary control are different, the control of the entire power network can be improved by accurately reflecting the required power amount of the entire power network, which varies over time, in the control of each device, and the required power can be efficiently supplied to the entire power network. Also, according to the aspects of the power converter and the power system including the power converter of the present invention, the power converter further has a function of secondary control for updating the droop characteristic according to the power conditions of the plurality of power elements, and thus the control of the entire power network can be made flexible, such as by peak cutting or utilizing nighttime power, according to the power conditions of the plurality of power elements.

[0010] According to an aspect of the power converter and a power system including a power converter of the present invention, the power system further has a central control unit that controls a plurality of the power converters, and the secondary control is performed based on instructions from the central control unit. This makes it possible to more accurately reflect the amount of power required across the entire power network, which varies over time, in the control of each device, thereby more reliably improving the control of the entire power network.

[0011] According to the aspects of the power converter and the power system including the power converter of the present invention, the secondary control is performed so that the power of the devices of the power elements is constant, so that when there is a margin in the power supply amount of the power system, the charging rate of the charging / discharging devices such as stationary power storage devices constituting the power system can be increased. Also, since the secondary control is performed so that the power of the devices of the power elements is constant, when the power supply amount required for the power system exceeds the contract power of the commercial power system, peak cutting of the power of the commercial power system can be performed to prevent the power supplied from the commercial power system to the power system from exceeding the contract power.

[0012] According to the aspects of the power converter and power system equipped with a power converter of the present invention, the secondary control is controlled based on the relationship between the amount of power discharged from a line to which a plurality of power elements are electrically connected and the amount of power received by the line, so that the amount of power required by the entire power network, which varies over time, can be more accurately reflected in the control of each device, thereby more reliably improving the control of the entire power network.

[0013] According to the aspects of the power converter and the power system equipped with the power converter of the present invention, the control period of the secondary control is longer than the control period of the primary control, so that it is possible to more flexibly improve the control of the entire power network, such as by peak cutting or utilizing nighttime power, depending on the power usage of multiple power elements.

[0014] According to the power converter control method, power system control method, and program of the present invention, the amount of power required by the entire power network, which varies over time, can be accurately reflected in the control of each device, thereby improving the control of the entire power network and efficiently supplying the required power to the entire power network. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is an explanatory diagram showing an overview of an entire power network that constitutes a power system according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is an explanatory diagram of droop characteristics given to devices used in a power network that constitutes the power system according to the first embodiment of the present invention. [Diagram 3] FIG. 3 is an explanatory diagram showing a state in which the droop characteristic given to the device used in the power system according to the first embodiment of the present invention is updated. [Figure 4] FIG. 4 is an explanatory diagram showing an example of updating the droop characteristic given to the stationary power storage device used in the power system according to the first embodiment of the present invention. [Diagram 5] FIG. 5 is an explanatory diagram showing an overview of the entire power network constituting the power system according to the second embodiment of the present invention. [Figure 6] FIG. 6 is an explanatory diagram showing a first example of updating the droop characteristics given to devices used in a power network that constitutes a power system according to the second embodiment of the present invention. [Figure 7] FIG. 7 is an explanatory diagram showing a second example of updating the droop characteristics given to devices used in a power network that constitutes a power system according to a second embodiment of the present invention. [Figure 8] FIG. 8 is an explanatory diagram showing an overview of the entire power network constituting the power system according to the third embodiment of the present invention. [Figure 9] FIG. 9 is an explanatory diagram showing a first example of updating the droop characteristic given to a stationary power storage device used in a power network that constitutes a power system according to a third embodiment of the present invention. [Figure 10] FIG. 10 is an explanatory diagram showing a second example of updating the droop characteristic given to a stationary power storage device used in a power network that constitutes a power system according to a third embodiment of the present invention. [Figure 11] FIG. 11 is a diagram illustrating the cutoff frequency of the low-pass filter in the second update example of the droop characteristic in FIG. [Figure 12] FIG. 12 is a flow chart showing the control mode determination of the power system of the present invention. [Figure 13]FIG. 13 is a sequence diagram showing an example of a control method for a power system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] First Embodiment First, a power system according to a first embodiment will be described as an embodiment of the power system of the present invention. FIG. 1 is an explanatory diagram showing an overview of an entire power network constituting the power system according to the first embodiment of the present invention. FIG. 2 is an explanatory diagram showing droop characteristics given to devices used in the power network constituting the power system according to the first embodiment of the present invention. FIG. 3 is an explanatory diagram showing a state in which the droop characteristics given to devices used in the power system according to the first embodiment of the present invention are updated. FIG. 4 is an explanatory diagram showing an example of updating the droop characteristics given to a stationary power storage device used in the power system according to the first embodiment of the present invention.

[0017] As shown in FIG. 1, a power network 10 constituting a power system 1 according to the first embodiment is provided with a plurality of power elements each including a power converter electrically connected to an AC commercial power system 100 and a device electrically connected to the power converter. Specifically, the power network 10 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 the DC power, a DC bus 19 connected to the output of the AC / DC converter 11, a first DC / DC converter 13 that is connected to the DC bus 19 and converts DC power input from the DC bus 19 into a charging voltage for a storage battery to be charged and outputs the DC power, 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 DC power input from the DC bus 19 into a charging voltage for a stationary power storage device 14 and outputs the charging voltage, and a photovoltaic 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. From the above, the power network 10 is a DC grid. In the power network 10, the storage battery is, for example, an on-board storage battery that is a storage battery mounted on an electric vehicle (EV) 18. 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 facility of the power network 10. In this way, the device is an element that is electrically connected to the power converter and is capable of inputting power and / or outputting power.

[0018] Each power converter includes, for example, a power conversion unit, a sensor, a control unit, and a communication unit.

[0019] 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.

[0020] The sensor is used in each power converter to measure electrical characteristic values ​​of its own end, such as a current value, a voltage value, a power value, etc. The sensor outputs the measured value to the control unit.

[0021] 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 charging and discharging of a stationary power storage device 14, discharging of a solar power generation device 15, and charging of an on-board storage battery of an electric vehicle 18 connected to an EV charger 17.

[0022] 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).

[0023] 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 the central control unit 110 (described later) via a network NW that is composed 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.

[0024] In the power system 1, the power converter has a function of primary control that controls the device according to the voltage (voltage at the own end) measured by the power converter, i.e., controls the device to follow a reference function having a droop characteristic that generates a target value when controlling the device at the own end. For example, the primary control is executed by a control unit of each power converter. Note that the "droop characteristic" refers to a drooping characteristic, and is a characteristic in which the relationship between the voltage at the own end and the amount of power input / output at the own end has a relationship other than a relationship in which the amount of power input / output is constant over a predetermined voltage range or a relationship in which the voltage is constant over a predetermined range of the amount of power input / output.

[0025] That is, in the power system 1, the AC / DC converter 11, which converts AC power input from the AC commercial power system 100 into DC power and outputs it, has a function of performing primary control so that the relationship between the voltage (V) at its own end and the power (P) output to the DC bus 19 has a predetermined droop (dropping) characteristic. The AC / DC converter 11 has a function of controlling so that the relationship between the voltage (V) at its own end and the power (P) output to the DC bus 19 maintains a reference function having a predetermined droop (dropping) characteristic in a predetermined control period.

[0026] Specifically, as shown in Fig. 2, AC / DC converter 11 connected to commercial power system 100 performs primary control using a function having a droop characteristic that maximizes the droop characteristic in a normal operation zone so that electric power can be stably supplied mainly from commercial power system 100 during normal operation. On the other hand, in a quasi-normal operation zone and a transient operation zone where electric 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 commercial power system 100 is cut off, and in a quasi-normal operation zone and a transient operation zone where electric 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), a dead zone (a vertical zone in Fig. 2) is provided so that the power supply from commercial power system 100 does not exceed the contracted power.

[0027] 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 performing primary control so that the relationship between the voltage (V) at its own end and the power (P) input from the DC bus 19 forms a predetermined characteristic. In other words, the first DC / DC converter 13 has a function of controlling so that the relationship between the voltage (V) at its own end and the power (P) input from the DC bus 19 maintains a function with predetermined characteristics in a predetermined control period.

[0028] Specifically, as shown in FIG. 2, the first DC / DC converter 13 connected to the EV charger 17 controls output in a transient operation zone where power demand is high, and does not control output in a quasi-normal operation zone where power demand is high, a normal operation zone, and the quasi-normal operation zone and transient operation zone where power demand is low.

[0029] The bidirectional DC / DC converter 12 connected to the stationary energy storage device 14 has a primary control function for controlling the relationship between the voltage (V) at its own end and the power (P) input / output from the DC bus 19 so as to follow a reference function having a predetermined droop (dropping) characteristic. In other words, the bidirectional DC / DC converter 12 has a function for controlling the relationship between the voltage (V) at its own end and the power (P) input / output from the DC bus 19 so as to maintain a reference function having a predetermined droop (dropping) characteristic in a predetermined control period.

[0030] 2, bidirectional DC / DC converter 12 connected to stationary power storage device 14 provides a dead zone in a normal operation zone so that no charging or discharging occurs, and performs primary control so that discharging is performed with a reference function having droop characteristics that maximize the droop characteristics in a quasi-normal operation zone where power demand is high. Also, bidirectional DC / DC converter 12 performs primary control so that charging is performed with a reference function having droop characteristics that maximize the droop characteristics in a quasi-normal operation zone where power demand is low.

[0031] The second DC / DC converter 16 connected to the photovoltaic power generation device (PV) 15 has a function of performing primary control so that the relationship between the voltage (V) of its own end and the power (P) output to the DC bus 19 forms a predetermined characteristic. In other words, the second DC / DC converter 16 has a function of controlling so that the relationship between the voltage (V) of its own end and the power (P) output to the DC bus 19 maintains a function having a predetermined characteristic in a predetermined control period.

[0032] Specifically, as shown in FIG. 2, a second DC / DC converter 16 connected to a photovoltaic power generation device (PV) 15 performs output control in a transient operation zone where power demand is low, and performs maximum power point tracking control (MPPT) in other operation zones.

[0033] From the above, in power system 1, a reference function having a droop characteristic is configured so as to change the amount of power (P) input and output of each device such as stationary power storage device 14 in response to a change in the voltage (V) of the entire power system 1. Also, in power system 1, each power element (each device and each power converter connected to each device) performs primary control in a distributed manner based on the voltage and power of its own end. In other words, the primary control is performed based on the voltage of the own end of each device connected to the power converter.

[0034] The power system 1 further has a secondary control function for updating a reference function having the above-mentioned droop characteristics in accordance with the power status of a plurality of power elements. The secondary control is control based on the relationship between the amount of power discharged from a line (DC bus 19) to which a plurality of power elements are electrically connected and the amount of power received by the line (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 constituting the power system 1.

[0035] 3, in the power system 1, in the secondary control, a comprehensive judgment is made regarding the primary control functions provided in each of the power converters, the AC / DC converter 11, the bidirectional DC / DC converter 12, the first DC / DC converter 13, and the second DC / DC converter 16, and the primary control functions provided in each of the power converters, 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 updated. A computer such as an AI (artificial intelligence) can be used to update the primary control functions provided in each power converter.

[0036] Moreover, the power system 1 further includes a central control unit 110 that controls a plurality of power converters (in the power system 1, the AC / DC converter 11, the bidirectional DC / DC converter 12, the first DC / DC converter 13 and the second DC / DC converter 16), and secondary control is performed based on commands from the central control unit 110. The central control unit 110 and each of the power converters, 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 via communication means. Therefore, the secondary control is performed by a centralized control method.

[0037] 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.

[0038] 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.

[0039] The communication unit communicates information with each power converter and the external server 200 via the network NW.

[0040] 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.

[0041] From the above, the power system 1 has a hierarchical control consisting of a primary control, which is a distributed control method, and a secondary control, which is a centralized control method. The primary control is performed based on the voltage at the own end of each device, such as the stationary power storage device 14, without going through commands from the central control unit 110. On the other hand, the secondary control is control based on, for example, the overall condition of the entire power system 1, and can be said to be control at a higher level than the primary control. The central control unit 110 is an EMS. The primary control and secondary control are performed, for example, by a program that causes a processor to execute the primary control and secondary control in each power converter or the central control unit 110.

[0042] Specifically, for example, in the secondary control of the power system 1, the reference function having a predetermined droop characteristic of the bidirectional DC / DC converter 12 connected to the stationary power storage device 14 is updated at a predetermined control period by reflecting not only the power status of the bidirectional DC / DC converter 12 but also the power status of other power converters (AC / DC converter 11, first DC / DC converter 13, second DC / DC converter 16) in response to an instruction from the central control unit 110. More specifically, for example, when the future weather is fine and the amount of power generated by the photovoltaic power generation device (PV) 15 is expected to increase, and the central control unit 110 determines that the function of the primary control of the photovoltaic power generation device (PV) 15 controlled by the second DC / DC converter 16 has a margin in terms of power supply, the reference function of the bidirectional DC / DC converter 12 is updated so as to have a droop characteristic for charging the stationary power storage device 14 even in a normal operation zone. Furthermore, as described above, while updating the reference function of the bidirectional DC / DC converter 12, the power supply from the commercial power grid 100 is cut off in the normal operation zone, and the reference function of the AC / DC converter 11 connected to the commercial power grid 100 is updated so as to have droop characteristics in the quasi-normal operation zone where power demand is high.

[0043] The secondary control may also perform updating of a reference having droop characteristics so that the power of the power element equipment remains constant.

[0044] 4, when charging the stationary energy storage device 14 to maintain its state of charge, in order to increase the charging rate of the stationary energy storage device 14, the function of the primary control of the bidirectional DC / DC converter 12 is updated in the secondary control so that the power value of the charging current to the stationary energy storage device 14 becomes a constant value in the normal operation zone and the quasi-normal operation zone. At this time, when the amount of power generated by the photovoltaic power generation device (PV) 15 is surplus, a charging current may be supplied from the photovoltaic power generation device (PV) 15 to the stationary energy storage device 14 to maintain its state of charge.

[0045] For example, in the secondary control, when information communication between the central control unit 110 and each power converter complies with the TCP / IP protocol, function information is included in the data portion of the IP packet of the command signal for updating the function. The function information is, for example, coordinate information of the boundary of the function (droop function) representing the droop characteristic, intercept information of the droop function, information on the slope (i.e., droop coefficient), and information on the shape (straight line, curve, etc.). This information is, for example, information defined in PV coordinates. The data portion of the IP packet contains, as a data string, information to be updated among the above information. The function information used for updating is stored in the storage unit of the central control unit 110, and is read out and used by the control unit as appropriate.

[0046] As shown in FIG. 4, in order to maintain the operating voltage range of the power system 1, when a sudden voltage fluctuation occurs, the bidirectional DC / DC converter 12 performs maximum discharge control or maximum charge control.

[0047] In the power system 1, the control period of the primary control is different from the control period of the secondary control. The primary control controls the relationship between the voltage at its own end and the power output to the DC bus 19 so as to maintain a reference function having a predetermined droop characteristic, so the control period of the primary control is, for example, one second or less. On the other hand, the secondary control updates the primary control function provided in each power converter based on the overall power supply and demand situation of the entire power system 1, so the control period of the secondary control is, for example, several tens of minutes to several hours. Therefore, the control period of the secondary control is longer than the control period of the primary control.

[0048] According to the power system 1, there is a primary control function for controlling each of the power converters (the commercial power system 100, the stationary battery storage device 14, the EV charger 17, and the solar power generation device (PV) 15) connected to the AC / DC converter 11, the bidirectional DC / DC converter 12, the first DC / DC converter 13, and the second DC / DC converter 16, so as to follow a reference function having droop characteristics that generates a target value when controlling each of the devices (the commercial power system 100, the stationary battery storage device 14, the EV charger 17, and the solar power generation device (PV) 15, respectively) in accordance with a voltage measured by each of the power converters, and a secondary control function for updating the reference function having droop characteristics to reflect the overall power supply and demand situation of the entire power system 1 in accordance with the power situations of each of the power elements 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. By having a hierarchical control in which the control period of the primary control and the control period of the secondary control are different, the required amount of power of the entire power network 10, which varies over time, is accurately reflected in the control of each device, thereby improving the control of the entire power network 10 and enabling the required power to be efficiently supplied to the entire power network 10.

[0049] Furthermore, according to the power system 1, there is further provided a secondary control function that updates a reference function having droop characteristics in accordance with the power status of each power element measured by the AC / DC converter 11, the bidirectional DC / DC converter 12, the first DC / DC converter 13, and the second DC / DC converter 16. This makes it possible to flexibly control the entire power network 10, such as by peak cutting or utilizing nighttime power, in accordance with the power status of each power element measured by the AC / DC converter 11, the bidirectional DC / DC converter 12, the first DC / DC converter 13, and the second DC / DC converter 16.

[0050] Furthermore, the power system 1 further includes a central control unit 110 that controls each of the power converters, the AC / DC converter 11, the bidirectional DC / DC converter 12, the first DC / DC converter 13, and the second DC / DC converter 16. Since the secondary control is performed based on the command of the central control unit 110, the amount of power required for the entire power network 10, which varies over time, can be more accurately reflected in the control of each device, thereby more reliably improving the control of the entire power network 10.

[0051] Furthermore, according to the power system 1, the secondary control is controlled based on the relationship between the amount of power discharged from the DC bus 19 and the amount of power received by the DC bus 19, so that the amount of power required for the entire power network 10, which varies over time, can be more accurately reflected in the control of each device, thereby more reliably improving the control of the entire power network 10.

[0052] Moreover, according to the power system 1, the secondary control is performed so that the power of the devices of the power elements is constant, so that when there is a surplus in the amount of power supply of the power system 1, it is possible to increase the charging rate of the charging / discharging devices such as the stationary power storage device 14 constituting the power system 1. Furthermore, since the secondary control is performed so that the power of the devices of the power elements is constant, when the amount of power supply required of the power system 1 exceeds the contracted power of the commercial power system 100, it is possible to prevent the power supplied from the commercial power system 100 to the power network 10 of the power system 1 from exceeding the contracted power by performing peak cutting of the power of the commercial power system 100.

[0053] Furthermore, according to the power system 1, the control period of the secondary control is longer than the control period of the primary control, so that the control of the entire power network 10 can be more flexibly improved, such as by peak cutting or utilizing nighttime power, depending on the power usage of multiple power elements.

[0054] <Second embodiment> Next, a power system according to a second embodiment will be described as an embodiment of the power system of the present invention. The power system according to the second embodiment has major components in common with the power system according to the first embodiment described above, and the same components will be described using the same reference numerals. FIG. 5 is an explanatory diagram showing an overview of the entire power network constituting the power system according to the second embodiment of the present invention. FIG. 6 is an explanatory diagram showing a first example of updating the droop characteristics given to the devices used in the power network constituting the power system according to the second embodiment of the present invention. FIG. 7 is an explanatory diagram showing a second example of updating the droop characteristics given to the devices used in the power network constituting the power system according to the second embodiment of the present invention.

[0055] As shown in FIG. 5, in the power system 2 according to the second embodiment, a general house 120 is further connected to the commercial power system 100 as a load in the power network 20. When the power demand of the general house 120, which is a general load, is small, the balance of power supply and demand in the power system 2 according to the second embodiment is almost the same as that in the power system 1 according to the first embodiment. Therefore, in the power system 2, the function having the droop characteristic used for the primary control of each power converter, the AC / DC converter 11, the bidirectional DC / DC converter 12, the first DC / DC converter 13, and the second DC / DC converter 16, can be a function having almost the same droop characteristic as that in the power system 1 according to the first embodiment in which the general house 120 is not connected to the commercial power system 100. Note that in FIG. 5, the central control unit 110, the external server 200, the network NW, and the like are omitted.

[0056] In addition, in the power system 2, when the power demand of the general load, that is, the general house 120, is maintained at a low level, the secondary control updates the function having droop characteristics based on a function having approximately the same droop characteristics as the previous power system 1, as shown in FIG. 6.

[0057] 7, when the power demand of ordinary house 120, which is an ordinary load, increases, in order to prevent the power demand from exceeding the contract power of commercial power system 100, i.e., to perform peak cutting of power supply from commercial power system 100, the function having the droop characteristic is updated in the secondary control so that power is output from AC / DC converter 11 to commercial power system 100. In this case, the function of the primary control of AC / DC converter 11 is updated in the secondary control so that the power value output from DC bus 19 to commercial power system 100 becomes a constant value.

[0058] As shown in FIG. 7 , in the event of a sudden voltage drop in the DC bus 19, in order to maintain the operating voltage range of the power system 2, the AC / DC converter 11 performs voltage maintenance control of the DC bus 19 by supplying power from the commercial power system 100 to the DC bus 19 in order to suppress the voltage drop in the DC bus 19.

[0059] <Third embodiment> Next, a power system according to a third embodiment will be described as an embodiment of the power system of the present invention. The power system according to the third embodiment has the same main components as the power system according to the first embodiment described above, and the same components will be described using the same reference numerals. FIG. 8 is an explanatory diagram showing an overview of the entire power network constituting the power system according to the third embodiment of the present invention. FIG. 9 is an explanatory diagram showing a first update example of the droop characteristic given to the stationary power storage device used in the power network constituting the power system according to the third embodiment of the present invention. FIG. 10 is an explanatory diagram showing a second update example of the droop characteristic given to the stationary power storage device used in the power network constituting the power system according to the third embodiment of the present invention. FIG. 11 is an explanatory diagram of the cutoff frequency of the low-pass filter in the second update example of the droop characteristic of FIG. 10.

[0060] In the power system 1 according to the first embodiment, the stationary power storage device 14 is provided in one system, but instead, as shown in Fig. 8, in the power system 3 according to the third embodiment, two systems of stationary power storage devices 14 are provided as the stationary power storage devices 14 constituting the power network 30. That is, the stationary power storage devices 14 include a first stationary power storage device 14-1 (referred to as "stationary power storage device 1" in Fig. 9) and a second stationary power storage device 14-2 (referred to as "stationary power storage device 2" in Fig. 9).

[0061] In the power system 3, in response to the provision of two systems of stationary power storage devices 14, the power network 30 includes a bidirectional DC / DC converter 12-1 connected to the DC bus 19 for converting DC power input from the DC bus 19 into a charging voltage for the first stationary power storage device 14-1 and outputting the same, and a bidirectional DC / DC converter 12-2 connected to the DC bus 19 for converting DC power input from the DC bus 19 into a charging voltage for the second stationary power storage device 14-2 and outputting the same. Note that the central control unit 110, the external server 200, the network NW, and the like are omitted in Fig. 8.

[0062] In the power system 3, due to differences in charge / discharge characteristics between the first stationary energy storage device 14-1 and the second stationary energy storage device 14-2, a state may occur in which the state of charge (SoC) of the first stationary energy storage device 14-1 and the state of charge (SoC) of the second stationary energy storage device 14-2 are significantly different. In this case, as shown in Fig. 9, in updating the reference function having the droop characteristics by the secondary control, the intercept of the reference function of the stationary energy storage device 14 with a high charge rate (the stationary energy storage device 1 in Fig. 9) is shifted upward from the reference function of the power system 1 shown in Fig. 2. In the stationary energy storage device 14 with a high charge rate, by performing an update to shift the intercept of the reference function upward, it becomes easier to discharge in the normal operation zone and the quasi-normal operation zone where power demand is high.

[0063] On the other hand, as shown in Fig. 9, in updating the reference function having droop characteristics by secondary control, the intercept of the reference function of stationary energy storage device 14 with a low charging rate (stationary energy storage device 2 in Fig. 9) is shifted downward compared to the reference function of power system 1 shown in Fig. 2. By performing an update that shifts the intercept of the reference function downward for stationary energy storage device 14 with a low charging rate, charging becomes easier even in a quasi-normal operation zone where power demand is high.

[0064] As described above, even if the state occurs in which the charging rate of the first stationary energy storage device 14-1 and the charging rate of the second stationary energy storage device 14-2 are significantly different from each other, the charging rate of the first stationary energy storage device 14-1 and the charging rate of the second stationary energy storage device 14-2 are equalized by updating the reference functions having droop characteristics related to the first stationary energy storage device 14-1 and the second stationary energy storage device 14-2 by the secondary control. Therefore, even if a plurality of systems of stationary energy storage devices 14 are provided, the charging and discharging efficiency of the entire stationary energy storage device 14 can be improved.

[0065] In addition, when the battery characteristics of the first stationary energy storage device 14-1 and the battery characteristics of the second stationary energy storage device 14-2 are different (for example, when the types of storage batteries installed in the stationary energy storage devices 14 are different), for example, a configuration can be made to share the frequency of the power output from the stationary energy storage device 14.

[0066] For example, as shown in Fig. 10, when the first stationary power storage device 14-1 is equipped with a lithium ion secondary battery (stationary power storage device (Li) in Fig. 10) having a high C rate indicating charge / discharge responsiveness but also being expensive, and the second stationary power storage device 14-2 is equipped with a lead-acid battery (stationary power storage device (Pb) in Fig. 10) having a low C rate but also being inexpensive, the secondary control of the power system 3 updates the function having the droop characteristics based on the function having the same droop characteristics as the previous power system 1. Therefore, the first stationary power storage device 14-1 and the second stationary power storage device 14-2 have functions having almost the same droop characteristics.

[0067] On the other hand, as shown in Fig. 11, when updating a function having droop characteristics in the secondary control, for example, in the first stationary energy storage device 14-1 (stationary energy storage device (Li) in Fig. 11) having a high C rate, when the bidirectional DC / DC converter 12-1 connected to the first stationary energy storage device 14-1 feeds back the observed values ​​of voltage and power in the primary control, the low-pass filter (LPF) is designed to have a large cutoff frequency. On the other hand, in the second stationary energy storage device 14-2 (stationary energy storage device (Pb) in Fig. 11) having a low C rate, when the bidirectional DC / DC converter 12-2 connected to the second stationary energy storage device 14-2 feeds back the observed values ​​of voltage and power in the primary control, the low-pass filter (LPF) is designed to have a small cutoff frequency.

[0068] In this way, by changing the set value of the cutoff frequency depending on the characteristics of the storage battery of the stationary energy storage device 14, the frequency of the power output from the stationary energy storage device 14 can be shared.

[0069] Next, a determination chart for the secondary control mode will be described with reference to Fig. 12. The control mode determination chart for the power system of the present invention is shown in Fig. 12 as a flow chart.

[0070] 12, a determination unit of the central control unit 110 determines whether or not there is a planned operation instruction from another control unit (not shown) based on a manually input instruction or a preset maintenance plan for the storage battery of the stationary power storage device 14. When the determination unit of the central control unit 110 determines that there is a planned operation instruction, the central control unit 110 performs planned operation control as secondary control.

[0071] On the other hand, when the determination unit of the central control unit 110 determines that there is no planned operation instruction, the determination unit determines whether or not there is an instruction from the other control unit (not shown) to keep the power of the power element equipment constant. Examples of instructions to keep the power of the power element equipment constant include peak cut control by the AC / DC converter 11 of the commercial power system 100, and increasing the charging rate of the storage battery mounted on the stationary power storage device 14 using surplus power from the photovoltaic power generation device (PV) 15. When there is an instruction from the other control unit (not shown) to keep the power of the power element equipment constant, the central control unit 110 updates the reference function of the target power element as secondary control so as to keep the power of the power element equipment constant. When there is no instruction from the other control unit (not shown) to keep the power of the power element equipment constant, the central control unit 110 updates the reference function in normal mode.

[0072] Next, an example of a control method for a power system as centralized control will be described with reference to a sequence diagram in Fig. 13. Note that although the control method will be described with reference to the power system 1, it can also be implemented in the other power systems described above.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] Next, in step S206, the control unit of the central control unit 110 reads out each piece of transmitted information, i.e., information regarding 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.

[0078] 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.

[0079] 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.

[0080] 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 status of the power system 1 and the corresponding results of switching or updating the reference function for each power converter as teaching data.

[0081] 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.

[0082] Next, another embodiment of the power system of the present invention will be described. In the power system of each of the above embodiments, the reference function having the droop characteristic is configured to change the amount of input / output power in response to a change in voltage, but instead, the reference function having the droop characteristic may be configured to change the amount of input / output current in response to a change in voltage.

[0083] 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, for example, a method in which a power converter observes the voltage at its own end, sets a target value of power from a 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 a reference function, and makes the voltage follow the target value of voltage may be used.

[0084] In addition, in the power system of each of the above embodiments, a central control unit is provided separately and performs secondary control in a centralized manner, but instead, at least one of the multiple power converters may be configured to have the function of a central control unit that controls the multiple power converters. [Industrial Applicability]

[0085] The power system of the present invention improves the control of the entire power network by accurately reflecting the amount of power required by the entire power network, which fluctuates over time, in the control of each device, and can efficiently supply the necessary power to the entire power network, making it highly useful in the field of DC grids with locally produced and consumed power networks. [Explanation of symbols]

[0086] 1, 2, 3 Power System 10, 20, 30 Power 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 17 EV charger 19 DC Bus 100 Commercial power system 110 Central Control Unit

Claims

1. A power converter electrically connected to an AC commercial power system and electrically connected to a device capable of inputting and / or outputting power, the power converter includes a control unit that executes primary control of the device based on a reference function having a droop characteristic that generates a target value when performing self-end control of the device in response to a voltage measured by the power converter; The power converter is further controlled by a secondary control in which a reference function having the droop characteristic is updated according to a power condition of a power system in which the power converter is provided; A power converter in which a control period of the primary control is different from a control period of the secondary control.

2. The power converter according to claim 1 , wherein the power system further comprises a central control unit that controls a plurality of the power converters, and the secondary control is performed based on a command from the central control unit.

3. 3. The power converter according to claim 1, wherein the primary control is performed based on a voltage at the device's own end without intervention of a command from a central control unit that controls the plurality of power converters.

4. 4. A power converter as claimed in claim 1, wherein the reference function having the droop characteristic is arranged to vary the amount of power or current input or output in response to a change in voltage.

5. 5. A power converter as claimed in claim 1, wherein the secondary control comprises updating a reference function having the droop characteristic such that the power of the equipment is constant.

6. 6. A power converter according to claim 1, wherein the primary control is performed based on a voltage at the terminal of the device, and the secondary control is controlled based on a relationship between an amount of power discharged from a line connected to the power converter and an amount of power received by the line.

7. The power converter according to claim 1 , wherein a control period of the secondary control is longer than a control period of the primary control.

8. 8. A power converter as claimed in any preceding claim which is a DC / DC converter.

9. The power converter according to claim 2 , wherein at least one of the plurality of power converters is configured to have a function as a central control unit that controls the plurality of power converters, instead of the central control unit.

10. A plurality of power elements are provided, each of which includes a power converter electrically connected to an AC commercial power system and a device electrically connected to the power converter; a control unit that performs primary control based on a reference function having a droop characteristic that generates a target value when performing self-end control of the device in accordance with a voltage measured by the power converter, The power system has a function of secondary control for updating a reference function having the droop characteristic in response to power conditions of the plurality of power elements, A power system in which a control period of the primary control and a control period of the secondary control are different from each other.

11. The power system according to claim 10 , further comprising a central control unit that controls a plurality of the power converters, and the secondary control is performed based on a command from the central control unit.

12. The power system according to claim 10 or 11, wherein the primary control is performed based on a voltage at a terminal of the device, without intervention of a command from a central control unit that controls the plurality of power converters.

13. 13. A power system as claimed in any one of claims 10 to 12, wherein the reference function having droop characteristics is arranged to vary the amount of power or current input or output in response to changes in voltage.

14. 14. The power system of claim 10, wherein the secondary control includes updating a reference function having the droop characteristic implemented such that the power of the equipment of the power element is constant.

15. 15. The power system according to claim 10, wherein the primary control is performed based on the voltage at the terminal of each of the devices, and the secondary control is performed based on the relationship between the amount of power discharged from a line to which the multiple power elements are electrically connected and the amount of power received by the line.

16. The power system according to claim 10 , wherein a control period of the secondary control is longer than a control period of the primary control.

17. The power system according to any one of claims 10 to 16, wherein a line to which the plurality of power elements are electrically connected is a DC bus.

18. The power system according to claim 11 , wherein at least one of the plurality of power converters is configured to have a function as a central control unit that controls the plurality of power converters, instead of the central control unit.

19. A method for controlling a power converter electrically connected to an AC commercial power system and electrically connected to a device capable of inputting and / or outputting power, comprising the steps of: a primary control step of controlling the device based on a reference function having a droop characteristic that generates a target value when controlling the device at its own end in response to the measured voltage of the power converter; The power converter is further controlled by a secondary control in which a reference function having the droop characteristic is updated according to a power condition of a power system in which the power converter is provided; Equipped with The control period of the primary control is different from the control period of the secondary control. A method for controlling a power converter.

20. A method for controlling a power system including a plurality of power elements, each of which includes a power converter electrically connected to an AC commercial power system and a device electrically connected to the power converter, comprising: performing a primary control based on a reference function having a droop characteristic that generates a target value when performing a self-end control of the device in response to a measured voltage of the power converter; performing a secondary control to update a reference function having the droop characteristic in response to power conditions of a plurality of the power elements; Equipped with The control period of the primary control is different from the control period of the secondary control. Power system control methods.

21. A control method for a power system including a central control device that is provided with a plurality of power elements each including a power converter electrically connected to an AC commercial power system and a device electrically connected to the power converter, and that is capable of communicating with an external server that holds information on the plurality of power converters and power demand, comprising: performing a primary control based on a reference function having a droop characteristic that generates a target value when performing a self-end control of the device in response to a measured voltage of the power converter; acquiring the demand information from the external server; executing a secondary control to update a reference function having the droop characteristic according to the power status of a plurality of the power elements and the demand information; Equipped with The control period of the primary control is different from the control period of the secondary control. Power system control methods.

22. The processor: A program for executing a control method for a power converter electrically connected to an AC commercial power system and electrically connected to a device capable of inputting and / or outputting power, comprising: a primary control step of controlling the device based on a reference function having a droop characteristic that generates a target value when controlling the device at its own end in response to the measured voltage of the power converter; The power converter is further controlled by a secondary control in which a reference function having the droop characteristic is updated according to a power condition of a power system in which the power converter is provided; Equipped with The control period of the primary control is different from the control period of the secondary control. program.

23. The processor: A program for executing a control method for a power system including a plurality of power elements each including a power converter electrically connected to an AC commercial power system and a device electrically connected to the power converter, the program comprising: performing a primary control based on a reference function having a droop characteristic that generates a target value when performing a self-end control of the device in response to a measured voltage of the power converter; performing a secondary control to update a reference function having the droop characteristic in response to power conditions of a plurality of the power elements; Equipped with The control period of the primary control is different from the control period of the secondary control. program.

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