Power system, control device, and control method

Abstract

An electric power system is provided with: a plurality of electric power converters that acquire an electric characteristic value of input or output electric power, use the acquired electric characteristic value as an input value, and use the acquired electric characteristic value as an output value as a direct-current electric line to which the plurality of electric power converters are connected; the control device updates the stored reference function to the acquired reference function on the basis of a power conversion characteristic for controlling the output of the power on the basis of a reference function that defines the electrical characteristic value of the output of the power from the input value, sets the reference function for each of the power converters, outputs the set reference function to the plurality of power converters, and outputs the set reference function to the plurality of power converters. The control device calculates, for each of the plurality of power converters, a voltage drop in the electrical line from a target value of the output power and a line impedance of the electrical line, and sets the reference function on the basis of the calculated voltage drop.

Description

Technical Field

[0001] The present invention relates to a power system, a control device and a control method. Background Art

[0002] Power grids that utilize local production and consumption are attracting attention as an alternative to large-scale power grids that rely on fossil fuels and nuclear energy. These grids are connected to a variety of devices, including photovoltaic (PV) generators (generators that generate electricity using renewable energy), stationary power storage systems, and electric vehicles (EVs). Because each of these devices uses direct current (DC) power sources, research is underway to develop power grids operating on DC (DC grids).

[0003] For example, in the system disclosed in Patent Document 1, each power converter is assigned a reference function based on its own terminal power (P) and voltage (V), and autonomous, decentralized control is performed to control the DC grid. Using a reference function that causes the target voltage value to droop according to the amount of power required by the DC bus, or in other words, a drooping characteristic, is sometimes referred to as droop control. By autonomously and decentralizedally controlling each power converter, load sharing of power flows between devices can be achieved based on the amount of power required by the DC bus, while also stabilizing the DC bus voltage.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: International Publication No. 2019 / 103059 Summary of the Invention

[0007] -Problems to be solved by the invention-

[0008] When autonomous distributed control is implemented by each power converter, in an ideal DC grid, regardless of DC bus line length, the DC bus voltage level is equal between each power converter. This allows accurate control of the power being exchanged and the target power to be blended between the supply and demand sides. However, due to the length of lines in a real DC grid, voltage drops caused by line resistance result in different voltage levels between the power converter on the supply side and the power converter on the demand side. Independent distributed control determines power blending by measuring the voltage level of each power converter on its own DC bus. Therefore, if the voltage levels differ between the supply and demand sides, blending the desired power using a reference function is difficult.

[0009] The present invention has been made in view of the above circumstances, and an object of the present invention is to perform power facilitation at a target power value even if a voltage drop occurs between the power supply side and the power demand side.

[0010] -Methods for solving the problem-

[0011] In order to solve the above-mentioned problems and achieve the purpose, the power system involved in one embodiment of the present invention comprises: a plurality of power converters, a control device and a DC power line connecting the plurality of power converters, the plurality of power converters having: a power conversion unit that converts and outputs the input power; a measuring unit that obtains the electrical characteristic value of the input or output power; a storage unit that stores a reference function that defines the electrical characteristic value of the output of the power conversion unit according to the input value; a characteristic control unit that uses the electrical characteristic value obtained by the measuring unit as an input value and controls the power conversion characteristic of the output of the power conversion unit based on the reference function; and an updating unit that obtains a reference function and updates the reference function stored in the storage unit to the obtained reference function. The control device comprises: a reference function setting unit for setting a reference function for each of the plurality of power converters; an output unit for outputting the set reference function to the plurality of power converters, wherein the reference function setting unit calculates the voltage drop in the power line according to the power target value output by the power conversion unit and the line impedance of the power line for each of the plurality of power converters, and calculates the voltage target value of the self-terminal voltage of the power converter when the power target value is output within the operating voltage range of the power converter based on the calculated voltage drop, and the reference function is set as a reference function that defines the electrical characteristic value of the output of the power conversion unit when the self-terminal voltage is the voltage target value as the power target value.

[0012] In the power system involved in one embodiment of the present invention, it may be that, when the line impedance changes due to a change in the structure of the electric line, the reference function setting unit calculates the voltage drop in the electric line based on the power target value output by the power conversion unit and the changed line impedance, calculates the voltage target value of the self-end voltage of the power converter when the power target value is output within the operating voltage range of the power converter based on the calculated voltage drop, updates the reference function to a reference function that defines the electrical characteristic value of the output of the power conversion unit when the self-end voltage is the voltage target value as the power target value, and the output unit outputs the updated reference function.

[0013] In the power system involved in one embodiment of the present invention, it may also be that, when the demand for power in the power element connected to the power converter or the supply of power from the power element changes, the reference function setting unit calculates the voltage drop in the power line based on the power target value of the output of the power conversion unit corresponding to the change and the line impedance of the power line, calculates the voltage target value of the self-end voltage of the power converter when the power target value is output within the operating voltage range of the power converter based on the calculated voltage drop, and updates the reference function to define the electrical characteristic value of the output of the power conversion unit when the self-end voltage is the voltage target value as a reference function of the power target value.

[0014] In the electric power system involved in one embodiment of the present invention, it may be that, when the number of the power converters connected to the electric line increases or decreases, the reference function setting unit calculates the voltage drop in the electric line based on the power target value output by the power conversion unit of the power converter connected to the electric line after the increase or decrease and the line impedance of the electric line, calculates the voltage target value of the self-end voltage of the power converter when the power target value is output within the operating voltage range of the power converter based on the calculated voltage drop, and updates the reference function to define the electrical characteristic value of the output of the power conversion unit when the self-end voltage is the voltage target value as a reference function of the power target value.

[0015] In the power system according to one embodiment of the present invention, the power target value may be set based on power supply and demand in the plurality of power converters, power supply and demand forecasts in power elements connected to the power converters, or optimization calculations of outputs of the power converters.

[0016] In the power system according to one embodiment of the present invention, the plurality of power converters may include: a power converter connected to a power element capable of supplying power and charging and discharging power; a power converter connected to a power element that supplies power; and a power converter that consumes power.

[0017] A control device according to one embodiment of the present invention comprises: a reference function setting unit for setting a reference function for each of a plurality of power converters; and an output unit for outputting the set reference function to the plurality of power converters, wherein the plurality of power converters comprise: a power conversion unit for converting and outputting input power; a measuring unit for obtaining an electrical characteristic value of the input or output power; a storage unit for storing a reference function for defining the electrical characteristic value of the output of the power conversion unit according to the input value; a characteristic control unit for controlling the power conversion characteristic of the output of the power conversion unit based on the reference function using the electrical characteristic value obtained by the measuring unit as an input value; and an updating unit for obtaining A reference function is obtained, and the reference function stored in the storage unit is updated to the obtained reference function. The reference function setting unit calculates the voltage drop in the power line according to the power target value of the output of the power conversion unit and the line impedance of the DC power line connecting the multiple power converters for each of the multiple power converters. Based on the calculated voltage drop, the voltage target value of the self-terminal voltage of the power converter when the power target value is output within the operating voltage range of the power converter is calculated. The reference function is set to define the electrical characteristic value of the output of the power conversion unit when the self-terminal voltage is the voltage target value as a reference function of the power target value.

[0018] A control method according to one embodiment of the present invention comprises the following steps: a reference function setting step for setting a reference function for each of a plurality of power converters; and an output step for outputting the set reference function to the plurality of power converters, wherein the plurality of power converters comprise: a power conversion unit for converting and outputting input power; a measuring unit for obtaining an electrical characteristic value of the input or output power; a storage unit for storing a reference function for defining the electrical characteristic value of the output of the power conversion unit according to the input value; a characteristic control unit for controlling the power conversion characteristic of the output of the power conversion unit based on the reference function using the electrical characteristic value obtained by the measuring unit as an input value; and an updating unit. Obtain a reference function, and update the reference function stored in the storage unit to the obtained reference function. In the reference function setting step, for each of the multiple power converters, calculate the voltage drop in the power line based on the power target value of the output of the power converter and the line impedance of the DC power line connecting the multiple power converters. Based on the calculated voltage drop, calculate the voltage target value of the self-terminal voltage of the power converter when the power target value is output within the operating voltage range of the power converter. Set the reference function as a reference function that defines the electrical characteristic value of the output of the power converter when the self-terminal voltage is the voltage target value as the power target value.

[0019] -Effects of the Invention-

[0020] According to the present invention, even if a voltage drop occurs between the power supply side and the power demand side, power convergence at a target power value can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a diagram showing the configuration of a power system according to the embodiment.

[0022] Figure 2 This is a block diagram showing the configuration of the control unit of the EMS.

[0023] Figure 3 This is the functional block diagram of EMS.

[0024] Figure 4 This is a block diagram showing the structure of a power converter.

[0025] Figure 5 This is a diagram showing functional units implemented in a control unit of a power converter.

[0026] Figure 6A This is a diagram showing an example of a reference function.

[0027] Figure 6B This is a diagram showing an example of a reference function.

[0028] Figure 7 This is a sequence diagram showing an example of the operation of the central control of the power system.

[0029] Figure 8 This is a flowchart showing the flow of processing performed by the control unit of the EMS.

[0030] Figure 9 This is a diagram showing an example of the relationship between power supply and demand.

[0031] Figure 10 This is a flowchart showing the flow of processing performed by the control unit of the power converter.

[0032] Figure 11 This is a diagram showing power elements and power converters included in the first embodiment.

[0033] Figure 12A This is a diagram showing an example of a reference function.

[0034] Figure 12B This is a diagram showing an example of a reference function.

[0035] Figure 13A This is a diagram showing an example of a reference function.

[0036] Figure 13B This is a diagram showing an example of a reference function.

[0037] Figure 14This is a diagram showing power elements and power converters included in the third embodiment.

[0038] Figure 15A This is a diagram showing an example of a reference function.

[0039] Figure 15B This is a diagram showing an example of a reference function.

[0040] Figure 16 This is a diagram showing power elements and power converters included in the fourth embodiment.

[0041] Figure 17A This is a diagram showing an example of a reference function.

[0042] Figure 17B This is a diagram showing an example of a reference function.

[0043] Figure 18 This is a diagram showing power elements and power converters included in the fifth embodiment.

[0044] Figure 19A This is a diagram showing an example of a reference function.

[0045] Figure 19B This is a diagram showing an example of a reference function.

[0046] Figure 20A This is a diagram showing an example of a reference function.

[0047] Figure 20B This is a diagram showing an example of a reference function.

[0048] Figure 21 This is a diagram showing power elements and power converters included in the seventh embodiment.

[0049] Figure 22A This is a diagram showing an example of a reference function.

[0050] Figure 22B This is a diagram showing an example of a reference function. DETAILED DESCRIPTION

[0051] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The present invention is not limited to the embodiments described below. In the drawings, identical parts are appropriately denoted by the same reference numerals.

[0052] [Implementation Method]

[0053] <Power System Structure>

[0054] Figure 1This diagram shows the configuration of a power system according to an embodiment of the present invention. Power system 1 includes a plurality of power converters 11 to 14 , power elements 21 to 24 , and a bus 30 . Furthermore, power system 1 includes an EMS (Energy Management System) 40 . EMS 40 is an example of a central control device.

[0055] Bus 30 is a DC bus in power system 1, connecting power converters 11 to 14. Bus 30 is an electrical line that transmits DC power. Power converters 11, 12, and 13 are DC / DC converters that convert DC voltage, while power converter 14 is an AC / DC converter that converts alternating current (AC) to DC. Power converters 11 to 14 are capable of communicating information via wired or wireless communication. The structure and function of power converters 11 to 14 will be described in detail later.

[0056] As an example, power element 21 is a stationary power storage device capable of charging and discharging electric power and is connected to power converter 11. A stationary power storage device is an example of a permanent, in-equipment power storage device. Power converter 11 has the following functions: it converts the voltage of the DC power supplied by power element 21 and outputs it to bus 30; it also converts the voltage of the DC power supplied from bus 30 and outputs it to power element 21, thereby charging power element 21.

[0057] As an example, power element 22 is a solar power generation device capable of generating and supplying electric power, and is connected to power converter 12. A solar power generation device is an example of a power generation device that generates electricity using renewable energy. Power converter 12 has the function of converting the voltage of the DC power supplied by power element 22 and outputting it to bus 30.

[0058] As an example, the power element 23 is an onboard power storage device capable of supplying, consuming, and charging power, and is connected to the power converter 13. The onboard power storage device is mounted on an electric vehicle (EV) and is an example of a mobile, non-stationary power storage device. The power converter 13 has the following functions: it converts the voltage of the DC power supplied by the power element 23 and outputs it to the bus 30, and it also converts the voltage of the DC power supplied from the bus 30 and outputs it to the power element 23 for charging. The power converter 13 is installed, for example, at a charging station or residential charging facility, but can also be mounted on an electric vehicle (EV).

[0059] As an example, power element 24 is a commercial power system and is connected to power converter 14. Power converter 14 converts AC power supplied by power element 24 into DC power and outputs it to bus 30, and also converts DC power supplied from bus 30 into AC power and outputs it to power element 24. The output of power from bus 30 to power element 24 is also called reverse power flow.

[0060] The EMS 40 has a function of comprehensively managing the state of the power system 1. The EMS 40 includes a control unit 41, a storage unit 42, and a communication unit 43.

[0061] Figure 2 This is a block diagram showing the structure of the control unit 41. The control unit 41 is composed of a processor 401, memory 402, storage 403, input / output I / F 404, and communication I / F 405, connected to a bus 406. Memory 402 is, for example, RAM, and is composed of volatile or non-volatile memory. Memory 402 serves as a workspace for the processor 401 when performing computations, storing the results of the processor's computations. Storage 403 is composed of ROM (Read Only Memory), an auxiliary storage device such as an HDD (Hard Disk Drive), or an SSD (Solid State Drive). Storage 403 stores programs and data used by the processor 401 for computations. The input / output I / F 404 is connected to the storage unit 42 to write information to and read information from the storage unit 42. The communication I / F 405 is connected to the communication unit 43 to control it. Processor 401, for example, a CPU (Central Processing Unit), reads programs from storage 403 and executes them using memory 402 as a workspace. Processor 401 can be an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), a DSP (Digital Signal Processor), or a GPU (Graphics Processing Unit). The functions of EMS 40 are realized by executing programs on processor 401.

[0062] The storage unit 42 includes, for example, an HDD or SSD, and stores various data used by the control unit 41 for computational processing. For example, the storage unit 42 stores data indicating the line impedance of the bus 30, data indicating the wiring topology of the bus 30, and data indicating the operating voltage range for voltage conversion of the power converters 11 to 14.

[0063] The communication unit 43 includes a communication module for performing information communication via wired or wireless communication. The communication unit 43 performs information communication with each power converter included in the power system 1 and the external server 200 via a network NW composed of an Internet network, a mobile phone network, or the like.

[0064] Figure 3 This diagram illustrates functional units according to the present invention implemented in the control unit 41 by the processor 401 executing a program. The reference function setting unit 411 sets a reference function for each of the power converters 11 to 14. The output unit 412 outputs an update command including the reference function set by the reference function setting unit 411 to the power converters 11 to 14.

[0065] Furthermore, external server 200 is a server installed outside power system 1. External server 200 is, for example, an information processing device configured to function as an EMS in another power system, and includes a database and functions as a data server for EMS 40. External server 200 stores various information that may affect the operation of power system 1.

[0066] <Power Converter Structure>

[0067] Next, the specific structure of the power converter 11 will be described. Figure 4 1 is a diagram showing the configuration of the power converter 11. The power converter 11 includes a power conversion unit 110, a sensor 120, a control unit 100, and a communication unit 130.

[0068] The power conversion unit 110 performs DC / DC conversion, converting the voltage of the DC power input from the discharged power element 21 and outputting it to the bus 30. The power conversion unit 110 can also convert the voltage of the DC power input from the bus 30 and output it to the power element 21 to charge the power element 21. The power conversion unit 110 is composed of, for example, circuits including coils, capacitors, diodes, switching elements, and the like. Examples of switching elements include field-effect transistors and insulated-gate bipolar transistors. The power conversion unit 110 can control the power conversion characteristics, for example, through PWM (Pulse Width Modulation) control.

[0069] Sensor 120 measures the electrical characteristic values of the power on the bus 30 side of power converter 110. Therefore, sensor 120 measures the electrical characteristic values of the power input to or output from power converter 11. Sensor 120 can measure current values, voltage values, power values, and the like. Sensor 120 is an example of a measuring unit that obtains electrical characteristic values. Sensor 120 outputs the measured electrical characteristic values to control unit 100.

[0070] To primarily implement the power conversion function of the power converter 11, the control unit 100 includes a processor that performs various computations to control the operation of the power converter 110 and a storage unit. The processor can use the configuration illustrated as processor 401, and the storage unit can use the configuration illustrated as memory 403. The functions of the control unit 100 are implemented as functional units by the processor reading and executing various programs from the storage unit. For example, the control unit 100 controls the power conversion characteristics of the power converter 110 according to a reference function based on the local power (P) and local voltage (V). Specifically, the control unit 100 outputs a PWM signal containing information on the manipulated variable (e.g., duty cycle) used for PWM control to the power converter 110, thereby performing PWM control on the power converter 110. The manipulated variable can be output directly to the power converter 110 or via other functional units (e.g., a loop control unit) (not shown).

[0071] The communication unit 130 is configured to include a communication module that communicates information via wired or wireless communication, and a communication control unit that controls the operation of the communication module. The communication unit 130 communicates information with the EMS 40 via the network NW. For example, the communication unit 130 receives information and commands from the EMS 40 and outputs them to the control unit 100. Furthermore, the communication unit 130 transmits information related to the power status, for example, input from the control unit 100, to the EMS 40. Furthermore, if the information related to the power status is a measurement value from the sensor 120, the communication unit 130 may also transmit the measurement value input from the sensor 120 to the EMS 40.

[0072] Figure 5 This diagram shows the functional units according to the present invention implemented in control unit 100. Control unit 100 includes an operation variable setting unit 100a, an information providing unit 100b, and an updating unit 100c, functional units implemented as software through program execution. Information providing unit 100b obtains electrical characteristic values output from sensor 120 and outputs the obtained electrical characteristic values to communication unit 130.

[0073] The manipulated variable setting unit 100a, an example of a characteristic control unit, controls the power conversion characteristics of the power conversion unit 110. Specifically, the manipulated variable setting unit 100a sets a target value for the output of the power conversion unit 110 based on the electrical characteristic value measured by the sensor 120 and reference function information stored in the storage unit 102 of the control unit 100. The target value is an electrical characteristic value, such as a voltage or power value. Furthermore, the manipulated variable setting unit 100a performs feedback control to set the manipulated variable (e.g., duty cycle) used for PWM control so that the difference between the electrical characteristic value measured by the sensor 120 and the set target value is within a predetermined range. The feedback control performed by the manipulated variable setting unit 100a can be performed using a well-known method such as PID control, which reads parameters such as proportional gain, integral time, and derivative time pre-stored in the storage unit 102 of the control unit 100. The manipulated variable setting unit 100a outputs information about the set manipulated variable to the power conversion unit 110 to control the power conversion unit 110.

[0074] The update unit 100c stores the reference function information included in the update command input from the communication unit 130 in the storage unit 102 of the control unit 100, thereby updating the reference function information stored in the storage unit 102. The update command is a command sent from the EMS 40. Here, the reference function information is various information used to specify the reference function, which will be described in detail later.

[0075] The other power converters 12, 13, and 14 may also have the same structure as the power converter 11. However, the power conversion unit 110 of the power converter 14 performs AC / DC conversion to convert the AC power supplied from the power element 24 into DC power and output it to the bus 30, and performs DC / AC conversion to convert the DC power supplied from the bus 30 into AC power and output it to the power element 24.

[0076] <Reference function characteristics>

[0077] Next, a reference function serving as a basis for the control unit 100 to control the power conversion characteristics of the power conversion unit 110 will be described. Figure 6A : is a diagram showing an example of a reference function indicated by reference function information. Reference function information is various information used to determine the reference function. Figure 6A In the figure, the vertical axis is voltage V and the horizontal axis is power P. Figure 6A The reference function represented by the line DL1 in the figure represents the relationship between the power P and the voltage V on the bus 30 side of the power conversion unit 110 of the power converter 11, that is, the VP characteristic, and represents the power conversion characteristics of the power conversion unit 110. Figure 6AThe reference function represented by line DL3 represents the power conversion characteristics of power conversion unit 110 of power converter 13. Power P is positive when power conversion unit 110 is supplying power to bus 30, that is, when power element 21 is discharging. It is negative when power is supplied from bus 30, that is, when power element 21 is charging. A power P = 0 state indicates neither charging nor discharging.

[0078] The reference function represented by line DL1 consists of a function defined according to the input value interval. The reference function represented by line DL3 consists of a connection of multiple functions defined according to the input value interval and having different droop characteristics. Lines DL1 and DL3 are determined by reference function information. Furthermore, the reference function may be a curved straight line or curve, formed by connecting multiple functions defined according to the input value interval and having different droop characteristics. Reference function information includes, for example, coordinate information of the function's boundaries, with the horizontal axis being P and the vertical axis being V, function intercept information, slope information (i.e., droop coefficient), and shape information (straight line, curve, etc.).

[0079] The control unit 100 of the power converter 11 controls the power conversion characteristics of the power converter 110 to correspond to the characteristics of the reference function represented by line DL1. Specifically, the control unit 100 of the power converter 111 controls the power converter 110 so that the operating point defined by the values of V and P lies on line DL1. The reference function is not limited to a droop characteristic function; any other function may be used as long as it defines a target value for the electric characteristic value based on the input value.

[0080] The control method of the power conversion unit 110 executed by the control unit 100 includes, for example, droopP control and droopV control. The droopP control is a control method that determines a target power value as a target value based on a voltage value as an electrical characteristic value measured by the sensor 120 and a reference function, and makes the difference between the power measurement value of the sensor 120 and the target power value fall below an allowable range. The droopV control is a control method that determines a target voltage value as a target value based on an electrical characteristic value, i.e., a power value or a current value, measured by the sensor 120 and a reference function, and makes the difference between the voltage measurement value of the sensor 120 and the target voltage value fall below an allowable range. In addition, as an electrical characteristic value such as a measurement value or a target value, a current value may be used instead of a power value. In this case, for example, the reference function is defined as the relationship between the current (I) on the horizontal axis and the voltage (V) on the vertical axis, i.e., a VI characteristic. In addition, for example, the control unit 100 performs feedback control called droopI control instead of droopP control, in which the current value of the target value, i.e., the target current value, is determined based on the measured value of the voltage of the sensor 120 and the reference function information, and the operation amount is set so that the difference between the target current value and the measured value of the current of the sensor 120 is below the allowable range.

[0081] Furthermore, the power converters 12 , 13 , and 14 also have reference function information corresponding to each power converter stored in the storage unit 102 , and are controlled so as to have the characteristics of the reference function determined by the stored reference function information.

[0082] <Control Method>

[0083] Next, the control methods for power converters 11-14 and power system 1 are described. Power system 1 can perform both so-called distributed control, in which power converters 11-14 independently and autonomously control themselves, and centralized control, in which EMS 40 coordinates control of power converters 11-14 based on the power conditions of power system 1. For example, distributed control is repeatedly executed in a relatively short cycle, while centralized control is executed at intervals longer than the distributed control cycle. Distributed control is also referred to as primary control, and centralized control is also referred to as secondary control. These control methods are executed, for example, by a processor executing a program in each power converter or EMS 40.

[0084] Central Control

[0085] First, the central control will be described. In the example shown below, the storage unit 102 of each of the power converters 11 to 14 stores reference function information in an updateable manner. The EMS 40 performs central control by updating the reference function used in the control of the power converters 11 to 14 according to instructions. Updating the reference function by instructions means that the instructions sent from the EMS 40 to the power converters 11 to 14 include reference function information related to the reference function, and a part or all of the reference function information stored in the power converters 11 to 14 is updated by the instructions. As described above, the reference function information is the coordinate information of the boundary of the function, the intercept information of the function, the slope information (i.e., the droop coefficient), and the shape information (straight line, curve, etc.). The reference function information used in the update is stored in the storage unit 42 of the EMS 40, and the control unit 41 reads and uses it as appropriate.

[0086] Next, refer to Figure 7 The sequence diagram of FIG1 illustrates an example of the central control operation in the power system 1. In the power system 1, the central control is performed at a predetermined period. Figure 7 First, the EMS 40 requests local measurement information from each of the power converters 11 to 14 (step S101). The local measurement information is an example of information related to the power status of the power system 1 and includes the electrical characteristic values measured by the sensors 120 of each of the power converters 11 to 14 and the times at which the electrical characteristic values were measured.

[0087] Next, power converters 11-14 transmit their respective acquired local measurement information to EMS 40 (step S102). EMS 40 stores each local measurement information in storage unit 42. Next, as an example of information related to the power status of power system 1, EMS 40 requests various information from external server 60 that may affect the operation of power system 1 (step S103). In this example, EMS 40 requests power generation / demand forecast information from external server 60. Power generation / demand forecast information includes power generation forecast information and power demand forecast information for power system 1. For example, it may also include information such as the season, current weather, and future weather forecast for the region where power system 1 is located. Furthermore, if external server 60 functions as an EMS for another power system, and the operating status of that other power system may affect the operation of power system 1, the power generation / demand forecast information may also include power generation forecast information and power demand forecast information for that other power system. Next, external server 60 transmits the power generation / demand forecast information to EMS 40 (step S104). The EMS 40 stores the power generation amount / demand forecast information in the storage unit 42 .

[0088] Next, the control unit 41 of the EMS 40 reads the transmitted information, ie, information on the power status of the power system 1 , from the storage unit 42 , and generates reference functions for the power converters 11 to 14 based on the information (step S105 ). Figure 8 4 is a flowchart showing the flow of a process for generating a reference function. This process is performed by the reference function setting unit 411 and is an example of a reference function setting step.

[0089] First, the control unit 41 sets target power values for supply or demand of the power converters 11-14 based on the power generation / demand forecast information stored in the storage unit 42 (step S201). This target power value can be set by executing an operation optimization calculation for the power system 1, or by an operator in the EMS 40 based on the power generation / demand forecast information. Furthermore, the target power value can be set based on local measurement information obtained from the power converters 11-14.

[0090] Operational optimization calculations are performed to apply to various conditions. For example, assume that power system 1 is controlled so that bus 30 reaches an operating point with a predetermined voltage. In this state, EMS 40, based on power generation / demand forecast information, predicts that the region where power element 22, a solar power generator, is located will experience sunny weather and increase power generation. Furthermore, based on local measurement information obtained from power converter 12 connected to power element 22, EMS 40 determines that power element 22 has a surplus in power supply. In this case, EMS 40 determines to update the reference function of power converter 11 connected to power element 21 so that power element 21, a stationary power storage device, is charged at this operating point. Furthermore, EMS 40 simultaneously determines to update the reference function of power converter 14 connected to power element 24 so that power is not supplied from power element 24, a commercial power system. Furthermore, operational optimization calculations can be performed based on conditions set to ensure that the power contracted for power element 24, a commercial power system, is not exceeded, such as by reducing peak loads and utilizing nighttime power, and to optimize electricity rates.

[0091] Next, the control unit 41 sets the shape of the reference function for the power converters 11 to 14 (step S202). For example, if the target power value for the power converter 13 set in step S201 is negative and the power element 23 is charged, the control unit 41 sets the shape of the reference function for the power converter 13 to Figure 6AThe shape of the line DL3 shown in FIG2 is such that the power converter 13 charges the power element 23. In addition, when the power target value of the power converter 11 set in step S201 is a positive value and the power element 23 is charged by the power supply from the power element 21, the control unit 41 sets the shape of the reference function of the power converter 11 to Figure 6A The shape of the line DL1 shown is such that the power converter 11 supplies electric power.

[0092] Next, the control unit 41 uses the power target value set in step S201, the data representing the line impedance of the bus 30 stored in the storage unit 42, the data representing the wiring topology of the bus 30 stored in the storage unit 42, the data representing the operating voltage range of the power converters 11 to 14 stored in the storage unit 42, etc. to calculate the voltage drop in the circuit of the bus 30, and sets the target value of the self-terminal voltage of the power converters 11 to 14 when outputting the power target value set in step S201, that is, the voltage target value, based on the calculated voltage drop (step S203).

[0093] Figure 9 : is a diagram showing an example of the relationship between the supply and demand of electric power in the electric power system 1. Figure 9 As shown in FIG. 1 , assuming that the power element 23 is charged by the power supply from the power element 21, the target power value of the power converter 11 is P + The target value of the self-terminal voltage of the power converter 11 is V + The target power value of the power converter 13 is P - The target value of the self-terminal voltage of the power converter 13 is V - When the line impedance of the power converter 11 is R1 and the line impedance of the power converter 13 is Rev, the control unit 41 sets V + and V - , so that P + =P - , V + falls within the operating voltage range of the power converter 11, and V - It falls within the operating voltage range of the power converter 13 .

[0094] Next, the control unit 41 optimizes the reference function of the shape set in step S202 based on the target value of the self-terminal voltage set in step S203 so that the power value output by the power converter when the self-terminal voltage is the target voltage value becomes the power target value (step S204). Figure 6A and Figure 6B An example of the processing of step S204 will be described. Figure 6A and Figure 6BThe illustrated single-dot chain line indicates a voltage drop between power converter 11 and power converter 13 . Figure 6A This is an example of a reference function before optimization in step S204.

[0095] In the case where no voltage drop occurs in the bus 30, for example, when the terminal voltages in the power converter 11 and the power converter 13 are Figure 6A At Va shown in FIG. 1 , the power converter 11 supplies power to the bus 30 at the target power value of 50 kW when the terminal voltage on line DL1 is Va, and the power converter 13 charges the power element 23 at the target power value of -50 kW when the terminal voltage on line DL3 is Va. However, the power converter 11 and the power converter 13 are connected at a voltage of 100 kW. Figure 6A When a voltage drop occurs along the dashed line shown, the operating point of the power converter 11 becomes Figure 6A At the position of Po1 shown in FIG. 1 , the operating point of the power converter 13 becomes Figure 6A When the operating point is at Po3, power converter 13 performs constant voltage control according to line DL3, charging power element 23 at -30 kW. Furthermore, when the operating point is at Po1, power converter 11 suppresses the output from power element 21 to 30 kW according to line DL1.

[0096] Therefore, the control unit 41 performs optimization processing in step S204, changes the intercept information of the line DL1 and shifts it upward, and sets it as Figure 6B In addition, the control unit 41 changes the intercept information of the line DL3 and shifts it downward, so that Figure 6B When this optimization is performed, the position of the operating point of the power converter 11 becomes Figure 6B At the position of Po1a shown in FIG. 1 , the operating point of the power converter 13 becomes Figure 6B The position of Po3a is shown. When the operating point is at Po3a, power converter 13 enters constant power control according to line DL3a, charging power element 23 at -50 kW. Furthermore, when the operating point is at Po1, power converter 11 sets the output from power element 21 to 50 kW according to line DL1a. Thus, even if a voltage difference occurs between power converter 11 and power converter 13 due to voltage drop, power flow is not inhibited, allowing power converter 11 to supply power at 50 kW and charging power element 23 at -50 kW. Alternatively, control unit 41 can achieve the target power value by changing the slope instead of the intercept information of line DL1.

[0097] return Figure 7 The EMS 40, having generated the reference function, outputs an update command containing the generated reference function information (step S106). The output unit 412 outputs the update command. Step S106 is an example of an output step. Next, the power converters 11 to 14 to be updated receive the reference function update command and update the reference function information (step S107). After completing the reference function information update, the power control device executes distributed control (step S108).

[0098] In addition, the control unit 41 may also execute the control mode when the wiring topology is changed, the number of power converters connected to the bus 30 is increased or decreased, the self-end measurement information of the power converter is changed, or the supply and demand power of the power converter is suppressed when the self-end measurement information sent from the power converter is detected. Figure 8 The processing shown.

[0099] Distributed Control

[0100] Next, the control method of distributed control in the power converters 11 to 14 will be described using the power converter 11 as an example. Note that the same control method as described below can also be appropriately executed in the other power converters 12 to 14.

[0101] In the control method of the power converter 11, the control unit 100 performs a control step of controlling the power conversion characteristics of the power converter 11, that is, the power conversion characteristics of the power conversion unit 110, based on a reference function. Figure 10 An example of the content of this control step will be described in detail. Figure 10 1 is a flowchart showing the flow of processing performed by the control unit 100 .

[0102] The control unit 100 executes, for example, Figure 10 First, the control unit 100 obtains the electrical characteristic value measured by the sensor 120 (step S301). Next, the control unit 100 obtains reference function information from the storage unit 102 (step S302).

[0103] Next, the control unit 100 sets a target value for the output of the power converter 11 (step S303). When performing droopP control, the control unit 100 sets the target value to the power value of the reference function where the voltage value measured by the sensor 120 intersects when plotted along the horizontal axis. Furthermore, when performing droopV control, if the reference function is a VP characteristic, the control unit 100 sets the target value to the voltage value of the reference function where the power value measured by the sensor 120 intersects when plotted along the vertical axis. If the reference function is a VI characteristic, the control unit 100 sets the target value to the voltage value of the reference function where the current value measured by the sensor 120 intersects when plotted along the vertical axis.

[0104] Next, control unit 100 sets the manipulated variable for PWM control so that the difference between the electrical characteristic value measured by sensor 120 and the target value set in step S203 is within a predetermined range, and outputs the set manipulated variable to power converter 110 (step S304). This controls power converter 110.

[0105] [First embodiment]

[0106] Next, a first embodiment of the optimization of the aforementioned reference function will be described. Figure 11 This diagram shows the power elements and power converters included in the first embodiment. Components identical to those in the previous embodiment are denoted by the same reference numerals, and their descriptions are omitted. In the first embodiment, power elements 21A, 21B, 21C, power element 23, power converters 11A, 11B, 11C, and power converter 13 are included in power system 1. Power elements 21A, 21B, and 21C are stationary power storage devices similar to power element 21. Power element 21A is connected to power converter 11A, power element 21B is connected to power converter 11C, and power element 21C is connected to power converter 11C.

[0107] Power converters 11A, 11B, and 11C are similar to power converter 11. Power converter 11A converts the voltage of the DC power supplied by power element 21A and outputs it to bus 30. It also converts the voltage of the DC power supplied from bus 30 and outputs it to power element 21A, thereby charging power element 21A. Power converter 11B converts the voltage of the DC power supplied by power element 21B and outputs it to bus 30. It also converts the voltage of the DC power supplied from bus 30 and outputs it to power element 21B, thereby charging power element 21B. Power converter 11C converts the voltage of the DC power supplied by power element 21C and outputs it to bus 30. It also converts the voltage of the DC power supplied from bus 30 and outputs it to power element 21C, thereby charging power element 21B.

[0108] In the first embodiment, the line impedance of the power converter 13 is Rev, the line impedance of the power converter 11A is R1, the line impedance of the power converter 11B is R2, and the line impedance of the power converter 11C is R3, and Rev=R1=R2=R3.

[0109] Figure 12A This is a diagram showing an example of the reference function set in step S202 in the first embodiment. For example, when the power element 23 is charged by the power supply from the power elements 21A, 21B, and 21C, the control unit 41 sets the shape of the reference function of the power converter 11A to Figure 12A The shape of the line DL11a shown in FIG. 1 is the shape of the reference function of the power converter 11B. Figure 12A The shape of the line DL11b shown in FIG. 1 is the shape of the reference function of the power converter 11C. Figure 12A Furthermore, when the power element 23 is charged by the power supply from the power elements 21A, 21B, and 21C, the shape of the reference function of the power converter 13 is set to Figure 12A The shape of line DL31a is shown.

[0110] In the case where no voltage drop occurs in the bus 30, for example, if the voltage at the terminal of each power converter is Figure 12AAs shown in FIG1 , power converter 11A supplies power to bus 30 at a target power value of 5 kW when the terminal voltage on line DL11a is V1, power converter 11B supplies power to bus 30 at a target power value of 15 kW when the terminal voltage on line DL11b is V1, and power converter 11C supplies power to bus 30 at a target power value of 30 kW when the terminal voltage on line DL11c is V1. Furthermore, power converter 13 charges power element 23 at a target power value of −50 kW when the terminal voltage on line DL31a is V1.

[0111] Figure 12A The dashed line shown is a line that approximates the voltage drop in the bus 30. In other figures showing reference functions, the dashed lines are also lines that approximate the voltage drop in the bus connected to the power converter. Figure 12A When a voltage drop occurs along the dashed line shown, power converter 13 controls the charging power so that the power value reaches the intersection of the dashed line and line DL31a, charging power element 23 at -21 kW. Furthermore, power converter 11A controls the power so that the power value reaches the intersection of the dashed line and line DL11a, suppressing output to bus line 30 to 1 kW. Power converter 11B controls the power so that the power value reaches the intersection of the dashed line and line DL11b, suppressing output to bus line 30 to 5 kW. Power converter 11C controls the power so that the power value reaches the intersection of the dashed line and line DL11c, suppressing output to bus line 30 to 15 kW.

[0112] For this purpose, the control unit 41 optimizes the line DL11a, the line DL11b, and the line DL11c in the aforementioned step S204. Specifically, the control unit 41 changes the slope of the line DL11a to Figure 12B The line DL11aa shown in FIG. 1 changes the slope of the line DL11b to Figure 12B The line DL11ba shown in FIG. 1 changes the slope of the line DL11c to Figure 12B The control unit 41 changes the intercept information of the line DL31a and shifts it downward, thereby setting it to Figure 12B Line DL31aa is shown.

[0113] Thus, even if a voltage difference occurs in bus 30 due to a voltage drop, power flow is not inhibited, and the output of power converter 11A can be set to 5 kW, the output of power converter 11B can be set to 15 kW, and the output of power converter 11C can be set to 30 kW, thereby charging power element 23 at -50 kW. Alternatively, control unit 41 can change the intercept information of the reference function each time lines DL11a, DL11b, and DL11c are optimized, thereby setting the output of power converter 11A to 5 kW, the output of power converter 11B to 15 kW, and the output of power converter 11C to 30 kW.

[0114] [Second embodiment]

[0115] Next, a second embodiment of the aforementioned reference function optimization will be described. In this second embodiment, as in the first embodiment, power converters 11A, 11B, and 11C, power converter 13, power elements 21A, 21B, 21C, and power element 23 are included in power system 1. In this second embodiment, the line impedance associated with power converter 13 is Rev, the line impedance associated with power converter 11A is R1, the line impedance associated with power converter 11B is R2, and the line impedance associated with power converter 11C is R3, where Rev = R1 = R2 < R3.

[0116] Figure 13A 202 in the second embodiment. For example, when the power element 23 is charged by the power supply from the power elements 21A, 21B, and 21C, the control unit 41 sets the shape of the reference function of the power converter 11A to Figure 13A The shape of the line DL12a shown in FIG. 1 is the shape of the reference function of the power converter 11B. Figure 13A The shape of the line DL12b shown in FIG. 1 is the shape of the reference function of the power converter 11C. Figure 13A Furthermore, when the power element 23 is charged by the power supply from the power elements 21A, 21B, and 21C, the control unit 41 sets the shape of the reference function of the power converter 13 to Figure 13A The shape of line DL32a is shown.

[0117] In the case where no voltage drop occurs in the bus 30, for example, if the voltage at the terminal of each power converter is Figure 13AAs shown in FIG2 , power converter 11A supplies power to bus 30 at a target power value of 5 kW when the terminal voltage on line DL12a is V2, power converter 11B supplies power to bus 30 at a target power value of 15 kW when the terminal voltage on line DL12b is V2, and power converter 11C supplies power to bus 30 at a target power value of 30 kW when the terminal voltage on line DL12c is V2. Furthermore, power converter 13 charges power element 23 at a target power value of −50 kW when the terminal voltage on line DL32a is V2.

[0118] Figure 13A and Figure 13B The single-dot chain line and the double-dot chain line shown are lines that approximate the voltage drop in the bus 30. Figure 13A The single-dot chain line shown generates a voltage drop between the power converter 11C and the power converter 13. Figure 13A When a voltage drop occurs along the dashed double-dashed line, power converter 13 controls the charging power so that the power value reaches the intersection of the dashed double-dashed line, the dashed double-dashed line, and line DL32a, thereby charging power element 23 at -9 kW. Furthermore, power converter 11A controls the power so that the power value reaches the intersection of the dashed double-dashed line and line DL12a, suppressing the output to bus line 30 to 1 kW. Power converter 11B controls the power so that the power value reaches the intersection of the dashed double-dashed line and line DL12b, suppressing the output to bus line 30 to 5 kW. Power converter 11C controls the power so that the power value reaches the intersection of the dashed double-dashed line and line DL12c, suppressing the output to bus line 30 to 3 kW.

[0119] For this purpose, the control unit 41 optimizes the line DL12a, the line DL12b, and the line DL12c in the aforementioned step S204. Specifically, the control unit 41 changes the intercept information of the line DL12a and shifts it upward, thereby setting it to Figure 13B The line DL12aa shown in FIG. 1 is shifted upward by changing the intercept information with respect to the line DL12b. Figure 13B The line DL12ba shown in FIG. 1 is shifted upward by changing the intercept information with respect to the line DL12c. Figure 13B The control unit 41 changes the intercept information of the line DL32aa and shifts it downward, thereby setting it to Figure 13B Line DL32aa is shown.

[0120] Thus, even if a voltage difference occurs in bus 30 due to a voltage drop, power flow is not inhibited, and the output of power converter 11A can be set to 5 kW, the output of power converter 11B to 15 kW, and the output of power converter 11C to 30 kW, thereby charging power element 23 at -50 kW. Furthermore, when optimizing lines DL12a, DL12b, and DL12c, control unit 41 can also change the slope of the reference function to set the output of power converter 11A to 5 kW, the output of power converter 11B to 15 kW, and the output of power converter 11C to 30 kW.

[0121] [Third embodiment]

[0122] Next, a third embodiment of the optimization of the aforementioned reference function will be described. Figure 14 1 is a diagram showing the power elements and power converters included in the third embodiment. In the third embodiment, the same reference numerals are used for the same structures as those in the previous embodiments, and their descriptions are omitted. In the third embodiment, power elements 21A, 21B, and 21C, power elements 23A and 23B, power converters 11A, 11B, and 11C, and power converters 13A and 13B are included in the power system 1. Power elements 23A and 23B are the same power elements as power element 23. Power converter 13A has the following functions: converting the voltage of the DC power supplied to power element 23A and outputting it to bus 30, and converting the voltage of the DC power supplied from bus 30 and outputting it to power element 23A, thereby charging power element 23A. The power converter 13B has the function of converting the voltage of the DC power supplied from the power element 23B and outputting it to the bus 30 , and converting the voltage of the DC power supplied from the bus 30 and outputting it to the power element 23B to charge the power element 23B.

[0123] In the third embodiment, the line impedance involved in the power converter 13A is Rev1, the line impedance involved in the power converter 13B is Rev2, the line impedance involved in the power converter 11A is R1, the line impedance involved in the power converter 11B is R2, and the line impedance involved in the power converter 11C is R3, and Rev1 = Rev2 = R1 = R2 = R3.

[0124] Figure 15A This is a diagram showing an example of the reference function set in step S202 in the third embodiment. For example, when the power elements 23A and 23B are charged by the power supply from the power elements 21A, 21B, and 21C, the control unit 41 sets the shape of the reference function of the power converter 11A to Figure 15A The shape of the line DL13a shown in FIG. 1 is the shape of the reference function of the power converter 11B. Figure 15A The shape of the line DL13b shown in FIG. 1 is the shape of the reference function of the power converter 11C. Figure 15A The shape of the line DL13c shown in FIG. 4 is shown in FIG. 4. In addition, the control unit 41 sets the shape of the reference function of the power converter 13A to Figure 15A The shape of the line DL33a shown in FIG. 1 is the shape of the reference function of the power converter 13B. Figure 15A The shape of line DL33b is shown.

[0125] In the case where no voltage drop occurs in the bus 30, for example, if the voltage at the terminal of each power converter is Figure 15A As shown in FIG3 , power converter 11A supplies power to bus 30 at a target power value of 5 kW when the terminal voltage on line DL13a is V3, power converter 11B supplies power to bus 30 at a target power value of 25 kW when the terminal voltage on line DL13b is V3, and power converter 11C supplies power to bus 30 at a target power value of 50 kW when the terminal voltage on line DL13c is V3. Furthermore, power converter 13A charges power element 23A at a target power value of -50 kW when the terminal voltage on line DL33a is V3, and power converter 13B charges power element 23B at a target power value of -30 kW when the terminal voltage on line DL33b is V3.

[0126] However, between the power converters 11A, 11B, 11C and the power converters 13A, 13B, Figure 15A When a voltage drop occurs along the dashed line shown, power converter 13A performs charging power control so that power element 23A is charged at -15 kW, which is the power value at the intersection of the dashed line and line DL33a. Power converter 13B performs charging power control so that power element 23B is charged at -20 kW, which is the power value at the intersection of the dashed line and line DL33b. Furthermore, power converter 11A performs power control so that the output to bus line 30 is suppressed to 3 kW, which is the power value at the intersection of the dashed line and line DL13a. Power converter 11B performs power control so that the output to bus line 30 is suppressed to 12 kW, which is the power value at the intersection of the dashed line and line DL13b. Power converter 11C performs power control so that the output to bus line 30 is suppressed to 20 kW, which is the power value at the intersection of the dashed line and line DL13c.

[0127] For this purpose, the control unit 41 optimizes the line DL13a, the line DL13b, and the line DL13c in the aforementioned step S204. Specifically, the control unit 41 changes the intercept information of the line DL13a and shifts it upward, thereby setting it to Figure 13B The line DL13aa shown in FIG. 1 is shifted upward by changing the intercept information with respect to the line DL13b. Figure 13B The line DL13ba shown is shifted upward by changing the intercept information with respect to the line DL13c. Figure 13B The control unit 41 changes the intercept information of the line DL33a and shifts it downward, thereby setting it to Figure 15B The line DL33aa shown in FIG. 1 is shifted downward by changing the intercept information with respect to the line DL33b. Figure 15B Line DL33ba is shown.

[0128] Thus, even if a voltage drop occurs in bus 30, power flow is not inhibited, and the output of power converter 11A can be set to 5 kW, the output of power converter 11B to 25 kW, and the output of power converter 11C to 50 kW, allowing power element 23A to be charged at -50 kW and power element 23B to be charged at -30 kW. Furthermore, when optimizing lines DL13a, DL13b, and DL13c, control unit 41 can also change the slopes to set the output of power converter 11A to 5 kW, the output of power converter 11B to 25 kW, and the output of power converter 11C to 50 kW.

[0129] [Fourth embodiment]

[0130] Next, a fourth embodiment of the optimization of the aforementioned reference function will be described. Figure 16 This diagram shows the power elements and power converters included in the fourth embodiment. In the fourth embodiment, identical components to those in the embodiment or the previous embodiment are denoted by the same reference numerals, and their descriptions are omitted. In the fourth embodiment, a bus 30A, a switch 31, power elements 21, 22, 23A and 23B, and 24, power converters 11, 12, 13A and 13B, and power converter 14 are included in a power system 1.

[0131] In the fourth embodiment, power system 1 includes bus 30A in place of bus 30. Bus 30A has a ring-shaped wiring topology. Switch 31 is a device that opens and closes the circuit of ring-shaped bus 30A. In the fourth embodiment, switch 31 is closed. Furthermore, in the fourth embodiment, the bus side of power converter 13A and the bus side of power converter 13B are connected before connecting to bus 30A.

[0132] Figure 17A This is an example of the reference function set in step S202 of the fourth embodiment. For example, when the power elements 23A and 23B are charged by the power supply from the power elements 21, 22, and 24, the control unit 41 sets the shape of the reference function of the power converter 11 to Figure 17A The shape of the line DL14a shown is the shape of the reference function of the power converter 12. Figure 17A The shape of the line DL24a shown in FIG. 1 is the shape of the reference function of the power converter 14. Figure 17A The shape of the line DL44a shown in FIG. 4 is shown in FIG. 4. In addition, the control unit 41 sets the shape of the reference function of the power converter 13A to Figure 17A The shape of the line DL34a shown is the shape of the reference function of the power converter 13B. Figure 17A The shape of line DL34b is shown.

[0133] In the case where no voltage drop occurs in the bus 30A, for example, if the voltage at the terminal of each power converter is Figure 17A As shown in FIG4 , power converter 11 supplies power to bus 30 at a target power value of 20 kW when its terminal voltage is V4 on line DL14a. Power converter 12 supplies power to bus 30 at a target power value of 20 kW when its terminal voltage is V4 on line DL24a. Power converter 14 supplies power to bus 30 at a target power value of 40 kW when its terminal voltage is V4 on line DL44a. Furthermore, power converter 13A charges power element 23A at a target power value of -50 kW when its terminal voltage is V4 on line DL34a. Power converter 13B charges power element 23B at a target power value of -30 kW when its terminal voltage is V4 on line DL34b.

[0134] However, when there is a voltage drop in the bus 30A, in the figure, if the operating point of the power converter 11 is set to OP1, the operating point of the power converter 12 is set to OP2, the operating point of the power converter 13A is set to OP31, the operating point of the power converter 13B is set to OP32, and the operating point of the power converter 14 is set to OP4, the positions of the respective operating points become Figure 17A The position of each action point is Figure 17A In the case of the position shown, the power converter 13A does not charge the power element 23A, and the power converter 13B charges the power element 23B at -30kW. Figure 17AIn the illustrated position, power converter 11 sets the output to bus line 30A to 0 kW, power converter 12 sets the output to bus line 30A to 20 kW, and power converter 14 suppresses the output to bus line 30A to 10 kW.

[0135] For this purpose, the control unit 41 optimizes the line DL14a and the line DL44a in the aforementioned step S204. Specifically, the control unit 41 changes the intercept information of the line DL14a and shifts it upward, thereby setting it to Figure 17B The line DL14aa shown is shifted upward by changing the intercept information with respect to the line DL44a. Figure 17B The control unit 41 changes the intercept information of the line DL34a and shifts it downward, thereby setting it to Figure 17B The line DL34aa shown is shifted downward by changing the intercept information with respect to the line DL34b. Figure 17B Line DL34ba shown.

[0136] Thus, even if a voltage difference occurs in bus 30A due to voltage drop, power flow is not inhibited. The output of power converter 11 can be set to 20 kW, the output of power converter 12 can be set to 20 kW, and the output of power converter 14 can be set to 40 kW. Power element 23A can be charged at -50 kW, and power element 23B can be charged at -30 kW. Furthermore, whenever control unit 41 optimizes lines DL14a and DL44a, it can also change the slope to set the output from power converter 11 to 20 kW and the output from power converter 14 to 40 kW.

[0137] [Fifth embodiment]

[0138] Next, a fifth embodiment of the optimization of the aforementioned reference function will be described. Figure 18 This diagram shows the power elements and power converter included in the fifth embodiment. In the fifth embodiment, components identical to those in the first embodiment or the previous embodiment are denoted by the same reference numerals, and their descriptions are omitted. The fifth embodiment differs from the fourth embodiment in that the switch 31 is in the open state.

[0139] When the switch 31 is in the closed state, the reference functions of the power converters 11, 12, 13A, 13B, and 14 are as follows: Figure 17BAs shown in Figure 1 , when switch 31 changes from a closed state to an open state, the wiring topology changes from a ring to a bus. This changes the line impedance of bus 30A, increasing the voltage drop between the power converters. For example, between power converter 14 and power converters 13A and 13B, when switch 31 is closed, they are connected in parallel, but when switch 31 is open, they are connected in series. This change in the structure of bus 30A increases the line impedance, resulting in a larger voltage drop.

[0140] As a result, the positions of the operating points of the power converters 11, 12, 13A, 13B, and 14 are respectively Figure 19A The position shown, as Figure 19A As shown, power converter 11 supplies 20 kW of power to bus 30A, power converter 12 supplies 20 kW of power from power element 22 to bus 30A, and power converter 14 supplies 25 kW of power from power element 24 to bus 30A. Furthermore, power converter 13A charges power element 23A at -35 kW, and power converter 13B charges power element 23B at -30 kW, making it difficult to achieve the desired power convergence.

[0141] Therefore, when the data indicating the wiring topology stored in the storage unit 32 is changed due to the change in the state of the switch 31, the control unit 41 executes Figure 7 as well as Figure 8 Specifically, the control unit 41 changes the intercept information of the line DL44aa and shifts it upward, thereby setting it to Figure 19B The control unit 41 changes the intercept information of the line DL34aa and shifts it downward, thereby setting it to Figure 19B Line DL35aa is shown.

[0142] Thus, even if a voltage difference occurs in bus line 30A due to a voltage drop, power flow is not inhibited. The output from power converter 11 can be set to 20 kW, the output from power converter 12 can be set to 20 kW, and the output from power converter 14 can be set to 40 kW. Power element 23A can be charged at -50 kW, and power element 23B can be charged at -30 kW. Furthermore, control unit 41 can also change the slope each time line DL44aa is optimized to maintain the output from power converter 14 at 40 kW.

[0143] [Sixth embodiment]

[0144] Next, the sixth embodiment of the optimization of the reference function is described. The sixth embodiment is a method in which each power converter in the fourth embodiment is optimized. Figure 17BThis is an example of a case where the output of the power element 22 decreases when the reference function shown is operated.

[0145] For example, when the output of the power element 22 becomes 0 kW, the reference function of the power converter 12 is updated to Figure 20A When the output of the power element 22 becomes 0 kW, the voltage drop between the power converter 14 and the power converters 13A and 13B becomes smaller. When the voltage drop between the power converters becomes smaller, the positions of the operating points of the power converters 11, 12, 13A, 13B, and 14 become Figure 20A Here, in the power converters 11 and 14, the voltage at the terminals is reduced, as shown in FIG. Figure 20A As shown, power converter 11 supplies 30 kW of power to bus 30A, and power converter 14 supplies 50 kW of power to bus 30A. Furthermore, power converter 13A charges power element 23A at -50 kW, and power converter 13B charges power element 23B at -30 kW, increasing the power supply from power element 24, which is the commercial power system.

[0146] Therefore, the control unit 41 optimizes the reference function of each power converter when the output of the power element 22 decreases. Specifically, the control unit 41 changes the intercept information of the line DL44aa and shifts it downward, thereby setting it to Figure 20B The control unit 41 changes the intercept information of the line DL14aa and shifts it upward, thereby setting it as Figure 20B As shown in line DL16aa. Thus, even if a voltage drop causes a voltage difference between power converters 11 and 14 and power converters 13A and 13B, the power supply from power element 24 can be suppressed, the output of power converter 11 can be set to 40 kW, the output of power converter 14 can be suppressed to 40 kW, power element 23A can be charged at -50 kW, and power element 23B can be charged at -30 kW. Furthermore, whenever control unit 41 optimizes lines DL14aa and DL44aa, it can also change the slope to maintain the output of power converter 11 at 40 kW and the output of power converter 14 at 40 kW.

[0147] [Seventh embodiment]

[0148] Next, a seventh embodiment of the optimization of the aforementioned reference function will be described. Figure 21This figure shows the power elements and power converters included in the seventh embodiment. Components identical to those in the embodiment or previous embodiments are denoted by the same reference numerals, and their descriptions are omitted. The seventh embodiment is an example of the fourth embodiment with the addition of a power converter 11D and a power element 21D. Power element 21D is a stationary power storage device similar to power element 21, and power converter 11D is a power converter similar to power converter 11.

[0149] In from Figure 16 From the state shown, the power converter 11D connected to the power element 21D is Figure 21 When the position shown is connected to bus 30A, the reference function of each power converter before updating by central control is as follows: Figure 22A As shown, the reference function of power converter 11 is line DL14aa, the reference function of power converter 12 is line DL24a, the reference function of power converter 13A is line DL34aa, the reference function of power converter 13B is line DL34ba, the reference function of power converter 14 is line DL24a, and the reference function of power converter 11D is line DL17d.

[0150] When the power element 21D and the power converter 11D are added to the power system 1, the power supplied to the bus 30A increases. Therefore, the voltage drop between the power converters in the bus 30A increases, and the positions of the operating points of the power converters 11, 11D, 12, 13A, 13B, and 14 become Figure 22A In the figure, the operating point of the power converter 11D is set to OP12.

[0151] Here, in the power converters 11, 11D, 12, and 14, the terminal voltage rises, as shown in FIG. Figure 22A As shown, the output of power converter 11 is 0 kW, power converter 11D supplies power to bus line 30A at 10 kW, power converter 12 supplies power to bus line 30A at 20 kW, and power converter 14 supplies power to bus line 30 at 40 kW. Furthermore, power converter 13A charges power element 23A at -40 kW, and power converter 13B charges power element 23B at -30 kW, thereby suppressing the amount of charged power.

[0152] Therefore, the control unit 41 optimizes the reference function of each power converter when the power element 21D and the power converter 11D are added to the power system 1. Specifically, the control unit 41 changes the intercept information of the line DL44aa and shifts it upward, setting Figure 22B The control unit 41 changes the intercept information of the line DL14aa and shifts it upwards, so that Figure 22BThe control unit 41 changes the intercept information of the line DL34aa and shifts it downward, setting it as Figure 22B Line DL37aa is shown.

[0153] Thus, even if a voltage difference occurs in bus line 30A due to a voltage drop, power flow is not inhibited. The output of power converter 11 can be set to 10 kW, the output of power converter 14 can be set to 40 kW, power element 23A can be charged at -50 kW, and power element 23B can be charged at -30 kW. Furthermore, control unit 41 can also change the slope each time it optimizes lines DL14aa and DL44aa, thereby maintaining the output of power converter 11 at 10 kW and the output of power converter 14 at 40 kW.

[0154] [Modification]

[0155] The embodiments of the present invention have been described above, but the present invention is not limited to the above-mentioned embodiments and can be implemented in various other ways. For example, the above-mentioned embodiments can be modified as follows to implement the present invention. In addition, the above-mentioned embodiments and the following modifications can also be combined respectively. Structures formed by appropriately combining the structural elements of the above-mentioned embodiments and modifications are also included in the present invention. In addition, those skilled in the art can easily derive further effects and modifications. Therefore, the broader aspects of the present invention are not limited to the above-mentioned embodiments and modifications and can be variously modified.

[0156] In the above-described embodiment, for example, the EMS 40 may also update the reference function when the demand for electric power in the power element 23 decreases.

[0157] In the above-described embodiment, a power converter connected to a power element consuming power may be connected to bus 30 or bus 30A. The power element consuming power is, for example, a device that converts electric power into kinetic energy or thermal energy.

[0158] In the present invention, the EMS 40 may send an update instruction only to the power converter that updates the reference function. In this case, the EMS 40 may notify the power converter that does not update the reference function that the update is not performed.

[0159] Industrial applicability

[0160] The present invention can be utilized in a power system, a control device, and a control method.

[0161] -Description of Reference Numerals-

[0162] 1 Power System

[0163] 11-14, 11A, 11B, 11C, 11D, 13A, 13B power converters

[0164] 21A, 21B, 21C, 21D, 22, 23, 23A, 23B, 24 Power Elements

[0165] 30, 30A bus

[0166] 31 switch

[0167] 40 EMS

[0168] 41 Control Department

[0169] 42, 102 Storage Department

[0170] 43.130 Ministry of Communications

[0171] 60 External Servers

[0172] 100 Control Department

[0173] 110 Power conversion unit

[0174] 120 sensors

[0175] 100a Operation amount setting unit

[0176] 100b Information Provision Department

[0177] 100c Update Department

[0178] 411 Reference function setting unit

[0179] 412 Output

[0180] NW Network.

Claims

1. A power system, characterized in that: have: a plurality of power converters, a control device, and a DC line connecting the plurality of power converters; The plurality of power converters include: A power conversion unit converts the input power and outputs it; a measuring unit that obtains an electrical characteristic value of the input or output power; a storage unit storing a reference function defining an electrical characteristic value of an output of the power conversion unit according to an input value; a characteristic control unit that uses the electrical characteristic value obtained by the measuring unit as an input value and controls the power conversion characteristic of the output of the power conversion unit based on the reference function; and an updating unit that obtains a reference function and updates the reference function stored in the storage unit to the obtained reference function, The control device has: a reference function setting unit configured to set a reference function for each of the plurality of power converters; an output unit, outputting the set reference function to the plurality of power converters, The reference function setting unit calculates the voltage drop in the electric line according to the power target value of the output of the power conversion unit and the line impedance of the electric line for each of the multiple power converters, calculates the voltage target value of the self-terminal voltage of the power converter when the power target value is output within the operating voltage range of the power converter based on the calculated voltage drop, and sets the reference function as a reference function that defines the electrical characteristic value of the output of the power conversion unit when the self-terminal voltage is the voltage target value as the power target value.

2. The power system according to claim 1, wherein: When the line impedance changes due to a change in the structure of the electric line, the reference function setting unit calculates a voltage drop in the electric line based on the target power value output by the power conversion unit and the changed line impedance, calculates a target voltage value of the self-terminal voltage of the power converter when the power target value is output within the operating voltage range of the power converter based on the calculated voltage drop, and updates the reference function to a reference function that defines the electrical characteristic value of the output of the power conversion unit when the self-terminal voltage is the target voltage value as the target power value. The output unit outputs the updated reference function.

3. The power system according to claim 1, wherein: When the demand for power in the power element connected to the power converter or the supply of power from the power element changes, the reference function setting unit calculates the voltage drop in the power line based on the power target value of the output of the power conversion unit corresponding to the change and the line impedance of the power line, calculates the voltage target value of the self-terminal voltage of the power converter when the power target value is output within the operating voltage range of the power converter based on the calculated voltage drop, and updates the reference function to define the electrical characteristic value of the output of the power conversion unit when the self-terminal voltage is the voltage target value as a reference function of the power target value.

4. The power system according to claim 1, wherein: When the number of the power converters connected to the electric line increases or decreases, the reference function setting unit calculates the voltage drop in the electric line based on the power target value output by the power conversion unit of the power converter connected to the electric line after the increase or decrease and the line impedance of the electric line, and calculates the voltage target value of the self-terminal voltage of the power converter when the power target value is output within the operating voltage range of the power converter based on the calculated voltage drop, and updates the reference function to define the electrical characteristic value of the output of the power conversion unit when the self-terminal voltage is the voltage target value as a reference function of the power target value.

5. The power system according to claim 1, wherein: The power target value is set based on power supply and demand in the plurality of power converters, power supply and demand forecast in power elements connected to the power converters, or optimization calculation of outputs of the power converters.

6. The power system according to claim 1, wherein: The plurality of power converters include a power converter to which a power element capable of supplying power and performing charge and discharge is connected; a power converter to which a power element that supplies power is connected; and a power converter that consumes power.

7. A control device, characterized in that: have: a reference function setting unit that sets a reference function for each of the plurality of power converters; and an output unit, outputting the set reference function to the plurality of power converters, Wherein, the plurality of power converters include: A power conversion unit converts the input power and outputs it; a measuring unit that obtains an electrical characteristic value of the input or output power; a storage unit storing a reference function defining an electrical characteristic value of an output of the power conversion unit according to an input value; a characteristic control unit that uses the electrical characteristic value obtained by the measuring unit as an input value and controls the power conversion characteristic of the output of the power conversion unit based on the reference function; and an updating unit that obtains a reference function and updates the reference function stored in the storage unit to the obtained reference function, The reference function setting unit calculates the voltage drop in the power line for each of the multiple power converters based on the power target value of the output of the power conversion unit and the line impedance of the DC power line connecting the multiple power converters, and calculates the voltage target value of the self-terminal voltage of the power converter when the power target value is output within the operating voltage range of the power converter based on the calculated voltage drop, and sets the reference function as a reference function that defines the electrical characteristic value of the output of the power conversion unit when the self-terminal voltage is the voltage target value as the power target value.

8. A control method, characterized in that: The steps are as follows: a reference function setting step of setting a reference function for each of the plurality of power converters; and an output step of outputting the set reference function to the plurality of power converters, Wherein, the plurality of power converters include: A power conversion unit converts the input power and outputs it; a measuring unit that obtains an electrical characteristic value of the input or output power; a storage unit storing a reference function defining an electrical characteristic value of an output of the power conversion unit according to an input value; a characteristic control unit that uses the electrical characteristic value obtained by the measuring unit as an input value and controls the power conversion characteristic of the output of the power conversion unit based on the reference function; and an updating unit that obtains a reference function and updates the reference function stored in the storage unit to the obtained reference function, In the reference function setting step, for each of the multiple power converters, the voltage drop in the power line is calculated based on the power target value of the output of the power conversion unit and the line impedance of the DC power line connecting the multiple power converters. Based on the calculated voltage drop, the voltage target value of the self-terminal voltage of the power converter when the power target value is output within the operating voltage range of the power converter is calculated. The reference function is set to define the electrical characteristic value of the output of the power conversion unit when the self-terminal voltage is the voltage target value as a reference function of the power target value.

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