Power converter, control method of power converter, power system, control method of power system, and computer-readable recording medium having program recorded

Abstract

A power converter is connected to a power transmission line, the power converter including: an input portion electrically connected to a device capable of inputting power from the power transmission line and / or outputting power to the power transmission line; a voltage variation portion connected to the input portion and varying voltage; a voltage adjustment portion connected to the voltage variation portion and adjusting voltage to be supplied to the power transmission line; a target setting portion defining a first target value of the voltage variation portion; a voltage monitoring portion connected to the power transmission line and observing voltage of the power transmission line; and a threshold value determination mechanism connected to the voltage monitoring portion and calculating a second target value of the voltage adjustment portion based on voltage of the power transmission line, the target setting portion generating the first target value as an output target of the voltage variation portion based on voltage observed by the voltage monitoring portion, the first target value having a characteristic in which a threshold voltage for output control of the voltage adjustment portion varies with time.

Description

Technical Field

[0001] The present invention relates to a power converter and a power system having said power converter, the power converter being electrically connected to an AC commercial power system via a power transmission line, electrically connected to a device capable of inputting power from and / or outputting power to the power transmission line, and the power converter having the function of controlling the device based on a reference function that generates a target value for local control of the device according to the voltage observed by the power converter. Background Technology

[0002] In recent years, power networks utilizing locally generated electricity have attracted attention as an alternative to large-scale power grids reliant on fossil fuels and nuclear energy. These networks connect various devices that generate electricity using renewable energy sources, such as solar power (PV) systems, stationary energy storage devices, and EV chargers for electric vehicles (EVs). Since these devices are DC power sources, research is underway on constructing DC power networks (DC grids) equipped with power converters.

[0003] Previously, as a control method for DC power grids, power converters connected to solar power generation devices (PV), stationary energy storage devices, etc., performed constant current control and constant voltage control on the solar power generation devices (PV), stationary energy storage devices, etc., based on instructions from a centralized control unit, thereby centrally controlling the power of the DC bus of the DC power grid.

[0004] Furthermore, droop control is implemented by assigning a reference function based on the local power (P) and local voltage (V) to solar power generation devices (PV) and stationary energy storage devices. This reference function, according to the electrical force required by the DC bus, causes the PV and stationary energy storage devices to exhibit droop characteristics at a target voltage value. Droop control, by controlling the relationship between output power or output current and output voltage to exhibit droop characteristics, creates virtual impedance for devices electrically connected to the power converter, enabling load sharing among the power converters. Through droop control, solar power generation devices (PV) and stationary energy storage devices are autonomously and decentralizedly controlled, thereby optimizing the adjustment of the output from the solar power generation device (PV) and the input / output of the stationary energy storage device according to the electrical force required by the DC bus, thus stabilizing the DC bus voltage.

[0005] As a conventional droop control, for example, in order to stabilize the voltage of the DC bus and the charging state of the stationary energy storage device, sometimes the intercept of a reference function with droop characteristics (the overall voltage (V) of the DC grid) is shifted towards the higher voltage side or the lower voltage side according to the change in the charging rate of the stationary energy storage device. Examples of such updated reference functions include those with a constant input-output domain that covers a specified voltage range and aims to maintain the input and output of the energy storage device at 0 (Patent Document 1).

[0006] Prior art literature

[0007] Patent documents

[0008] Patent Document 1: International Publication No. 2019 / 103059 Summary of the Invention

[0009] -The problem the invention aims to solve-

[0010] While the aforementioned centralized control method for DC power grids can easily control the entire DC power grid, it suffers from the problem of difficulty in smoothly coping with rapid fluctuations in power supply and demand. In Patent Document 1, by setting a constant input-output domain with zero input and output in the reference function, the power supply of the DC power grid can be maintained without charging or discharging the energy storage device, provided by power supplied from external commercial power systems and solar power (PV) devices, under stable DC power grid operation.

[0011] On the other hand, for example, when maintaining at least a portion of the power supply to the DC grid by power supplied from solar power generation devices (PV), as a reference function for controlling the output of solar power generation devices (PV), examples include: Figure 6 As shown, this is a reference function for suppressing the output (power) P of a solar power generation device (PV) when the voltage V on the DC bus rises to the threshold V thresh. Figure 6 The reference function shown stabilizes the DC bus voltage by suppressing the output (power) P of the solar power generation device (PV) based on the rise of the DC bus voltage V.

[0012] However, in order to suppress the power supply from external commercial power systems, if... Figure 6 The reference function shown has a high threshold Vthresh set to improve the power efficiency of the solar power generation device (PV). However, there are concerns that stabilizing the DC bus voltage may be difficult when interference occurs due to load variations. On the other hand, to stabilize the DC bus voltage even when interference occurs due to load variations, if... Figure 6If the threshold V_thresh of the reference function shown is set too low, there is a problem that the output suppression of the solar power generation device (PV) is likely to occur, and the power efficiency of the solar power generation device (PV) cannot be improved.

[0013] Based on the above, the object of the present invention is to provide a power converter that can stabilize the voltage of the transmission line even when the power network is disturbed, and can improve the power efficiency of the equipment constituting the power network, as well as a power system having the power converter, a control method for the power converter, a control method and program for the power system.

[0014] -Methods for solving the problem-

[0015] The main idea of ​​the structure of this invention is described below.

[0016] [1] A power converter connected to a power transmission line, the power converter comprising:

[0017] The input unit is electrically connected to a device capable of inputting power from the power transmission line and / or outputting power to the power transmission line;

[0018] A voltage fluctuation unit is connected to the input unit to cause voltage fluctuation;

[0019] A voltage adjustment unit, connected to the voltage fluctuation unit, adjusts the voltage supplied to the power transmission line;

[0020] The target setting unit specifies the target value for the voltage fluctuation unit;

[0021] A voltage monitoring unit, connected to the power transmission line, observes the voltage of the power transmission line; and

[0022] A threshold determination mechanism, connected to the voltage monitoring unit, calculates the target value of the voltage adjustment unit based on the voltage of the power transmission line.

[0023] In the power converter, based on the voltage observed by the voltage monitoring unit, the target setting unit generates a target value as the output target of the voltage fluctuation unit.

[0024] The target value has the characteristic that the threshold voltage controlled by the output of the voltage adjustment unit changes over time.

[0025] [2] In the power converter described in [1], the device is controlled based on a reference function that generates a target value for local control of the device according to the voltage observed by the voltage monitoring unit.

[0026] [3] In the power converter described in [2], the reference function has a specified time-limited characteristic.

[0027] [4] In the power converter described in [2] or [3], if the threshold voltage value is set to Vr, the capacitance of the transmission line is set to C, and the time constant determined according to the capacitance is set to Tr, then the reference function has the following relationship as shown in equation (1).

[0028] Tr = function(Vr, C) (1)

[0029] If the observed voltage at the local terminal of the power converter is set to V0, then when the state of V0 > Vr continues for more than Tr, the voltage fluctuation unit controls the output of power from the device to the transmission line to suppress the output of power.

[0030] [5] In any of the power converters described in [2] to [4], if the threshold voltage value is set to Vr, the capacitance of the transmission line is set to C, and the time constant determined according to the capacitance is set to Tr, then the reference function has the following relationship as shown in equation (1).

[0031] Tr = function(Vr, C) (1)

[0032] If the observed voltage at the local terminal of the power converter is set to V0, then when the state of V0 < Vr continues for more than Tr, the voltage fluctuation unit controls the output of power from the device to the transmission line to promote the output of power, and stops promoting the output if V0 reaches Vr.

[0033] [6] In the power converter described in [4] or [5], the device is a power generation device.

[0034] [7] In the power converter described in [6], the power generation device is a power generation device that generates electricity using renewable energy or a power generation device that generates electricity using fuel.

[0035] [8] In the power converter described in [2] or [3], if the threshold voltage value is set to Vr, the capacitance of the transmission line is set to C, and the time constant determined according to the capacitance is set to Tr, then the reference function has the following relationship as shown in equation (1).

[0036] Tr = function(Vr, C) (1)

[0037] If the observed voltage at the local terminal of the power converter is set to VO, then when the state of V0 < Vr continues for more than Tr, the voltage fluctuation unit controls the power input from the transmission line to the equipment to suppress the power input.

[0038] [9] In the power converter described in [2], [3] or [8], if the threshold voltage value is set to Vr, the capacitance of the transmission line is set to C, and the time constant determined according to the capacitance is set to Tr, then the reference function has the following relationship as shown in equation (1).

[0039] Tr = function(Vr, C) (1)

[0040] If the observed voltage at the local terminal of the power converter is set to V0, then when the state of V0 > Vr continues for more than Tr, the voltage fluctuation unit controls the input of power from the transmission line to the equipment to promote the input of power, and stops the input promotion if V0 reaches Vr.

[0041]

[10] In the power converter described in [8] or [9], the device is a load.

[0042]

[11] In the power converter described in

[10] , the load is an EV charger for charging the on-board battery of an electric vehicle.

[0043]

[12] An electric power system includes a power unit, the power unit comprising a power converter and devices electrically connected to the power converter.

[0044] The power converter includes:

[0045] The input unit is electrically connected to a device capable of inputting power from the power transmission line and / or outputting power to the power transmission line;

[0046] A voltage fluctuation unit is connected to the input unit to cause voltage fluctuation;

[0047] A voltage adjustment unit, connected to the voltage fluctuation unit, adjusts the voltage supplied to the power transmission line;

[0048] The target setting unit specifies the target value for the voltage fluctuation unit;

[0049] A voltage monitoring unit, connected to the power transmission line, observes the voltage of the power transmission line; and

[0050] A threshold determination mechanism, connected to the voltage monitoring unit, calculates the target value of the voltage adjustment unit based on the voltage of the power transmission line.

[0051] In the power converter, based on the voltage observed by the voltage monitoring unit, the target setting unit generates a target value as the output target of the voltage fluctuation unit.

[0052] The target value has the characteristic that the threshold voltage controlled by the output of the voltage adjustment unit changes over time.

[0053]

[13] In the power system described in

[12] , the device is controlled based on a reference function of the target value when the device is controlled locally, generated according to the voltage observed by the voltage monitoring unit.

[0054]

[14] In the power system described in

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

[0055]

[15] In the power system described in

[13] or

[14] , if the threshold voltage value is set as Vr, the capacitance of the transmission line is set as C, and the time constant determined according to the capacitance is set as Tr, then the reference function has the following relationship as shown in equation (1).

[0056] Tr = function(Vr, C) (1)

[0057] If the observed voltage at the local terminal of the power converter is set to V0, then when the state of V0 > Vr continues for more than Tr, the voltage fluctuation unit controls the output of power from the device to the transmission line to suppress the output of power.

[0058]

[16] In any of the power systems described in

[13] to

[15] , if the threshold voltage value is set as Vr, the capacitance of the transmission line is set as C, and the time constant determined according to the capacitance is set as Tr, then the reference function has the following relationship as Equation (1).

[0059] Tr = function(Vr, C) (1)

[0060] If the observed voltage at the local terminal of the power converter is set to V0, then when the state of V0 < Vr continues for more than Tr, the voltage fluctuation unit controls the output of power from the device to the transmission line to promote the output of power, and stops promoting the output if V0 reaches Vr.

[0061]

[17] In the power system described in

[15] or

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

[0062]

[18] In the power system described in

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

[0063]

[19] In the power systems described in

[13] or

[14] ,

[0064] If the threshold voltage is set to Vr, the capacitance of the transmission line is set to C, and the time constant determined based on the capacitance is set to Tr, then the reference function has the following relationship as shown in equation (1).

[0065] Tr = function(Vr, C) (1)

[0066] If the observed voltage at the local terminal of the power converter is set to V0, then when the state of V0 < Vr continues for more than Tr, the voltage fluctuation unit controls the power input from the transmission line to the equipment to suppress the power input.

[0067]

[20] In the power system described in

[13] or

[19] , if the threshold voltage value is set as Vr, the capacitance of the transmission line is set as C, and the time constant determined according to the capacitance is set as Tr, then the reference function has the following relationship as shown in equation (1).

[0068] Tr = function(Vr, C) (1)

[0069] If the observed voltage at the local terminal of the power converter is set to V0, then when the state of V0 > Vr continues for more than Tr, the voltage fluctuation unit controls the input of power from the transmission line to the equipment to promote the input of power, and stops the input promotion if V0 reaches Vr.

[0070]

[21] In the power system described in

[19] or

[20] , the device is a load.

[0071]

[22] In the power system described in

[21] , the load is an EV charger for charging the on-board battery of an electric vehicle.

[0072]

[23] In any of the power systems described in

[12] to

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

[0073]

[24] A control method for a power converter, the power converter being connected to a transmission line, and the input section of the power converter being connected to a device capable of inputting power from the transmission line and / or outputting power to the transmission line, the control method for the power converter comprising:

[0074] The step of changing the voltage using a voltage regulating unit connected to the input unit;

[0075] The step of adjusting the voltage supplied to the power transmission line by a voltage adjustment unit connected to the voltage fluctuation unit;

[0076] The prescribed steps are performed on the first target value of the voltage fluctuation unit;

[0077] The steps for observing the voltage of the transmission line; and

[0078] The step of calculating the second target value of the voltage adjustment unit based on the observed voltage of the transmission line.

[0079] The first target value is generated based on the observed voltage of the transmission line, which serves as the output target of the voltage fluctuation unit.

[0080] The target value has the characteristic that the threshold voltage controlled by the output of the voltage adjustment unit changes over time.

[0081]

[25] A control method for a power system, wherein the power system is provided with a power unit, the power unit having a power converter and a device electrically connected to the power converter.

[0082] The power converter is connected to a transmission line, and the input section of the power converter is connected to a device capable of inputting power from the transmission line and / or outputting power to the transmission line. The control method of the power system includes:

[0083] The step of changing the voltage using a voltage regulating unit connected to the input unit;

[0084] The step of adjusting the voltage supplied to the power transmission line by a voltage adjustment unit connected to the voltage fluctuation unit;

[0085] The prescribed steps are performed on the first target value of the voltage fluctuation unit;

[0086] The steps for observing the voltage of the transmission line; and

[0087] The step of calculating the second target value of the voltage adjustment unit based on the observed voltage of the transmission line.

[0088] The first target value is generated based on the observed voltage of the transmission line, which serves as the output target of the voltage fluctuation unit.

[0089] The target value has the characteristic that the threshold voltage controlled by the output of the voltage adjustment unit changes over time.

[0090]

[26] A control method for a power system, wherein the power system is provided with a power unit, the power unit having a power converter and a device electrically connected to the power converter.

[0091] The power converter is connected to the power transmission line, and the input section of the power converter is connected to the device capable of inputting power from the power transmission line and / or outputting power to the power transmission line.

[0092] The power system includes a central control device, which is capable of communicating with the power converter and an external server storing power demand information. The control method of the power system includes:

[0093] The step of changing the voltage using a voltage regulating unit connected to the input unit;

[0094] The step of adjusting the voltage supplied to the power transmission line by a voltage adjustment unit connected to the voltage fluctuation unit;

[0095] The prescribed steps are performed on the first target value of the voltage fluctuation unit;

[0096] The steps for observing the voltage of the power transmission line;

[0097] The step of calculating the second target value of the voltage adjustment unit based on the observed voltage of the transmission line; and

[0098] The step of obtaining the requirement information from the external server.

[0099] The first target value is generated based on the observed voltage of the transmission line, which serves as the output target of the voltage fluctuation unit.

[0100] The target value has the characteristic that the threshold voltage controlled by the output of the voltage adjustment unit changes over time.

[0101]

[27] A program that causes a processor to execute a control method for a power converter, the power converter being connected to a power transmission line, and the input section of the power converter being connected to a device capable of inputting power from the power transmission line and / or outputting power to the power transmission line, the control method for the power converter comprising:

[0102] The step of changing the voltage using a voltage regulating unit connected to the input unit;

[0103] The step of adjusting the voltage supplied to the power transmission line by a voltage adjustment unit connected to the voltage fluctuation unit;

[0104] The prescribed steps are performed on the first target value of the voltage fluctuation unit;

[0105] The steps for observing the voltage of the transmission line; and

[0106] The step of calculating the second target value of the voltage adjustment unit based on the observed voltage of the transmission line.

[0107] The first target value is generated based on the observed voltage of the transmission line, which serves as the output target of the voltage fluctuation unit.

[0108] The target value has the characteristic that the threshold voltage controlled by the output of the voltage adjustment unit changes over time.

[0109]

[28] A program that causes a processor to execute a control method for a power system, the power system comprising a power unit having a power converter and a device electrically connected to the power converter, the power converter being connected to a transmission line, and the input section of the power converter being connected to the device capable of inputting power from the transmission line and / or outputting power to the transmission line, the control method for the power system comprising:

[0110] The step of changing the voltage using a voltage regulating unit connected to the input unit;

[0111] The step of adjusting the voltage supplied to the power transmission line by a voltage adjustment unit connected to the voltage fluctuation unit;

[0112] The prescribed steps are performed on the first target value of the voltage fluctuation unit;

[0113] The steps for observing the voltage of the transmission line; and

[0114] The step of calculating the second target value of the voltage adjustment unit based on the observed voltage of the transmission line.

[0115] The first target value is generated based on the observed voltage of the transmission line, which serves as the output target of the voltage fluctuation unit.

[0116] The target value has the characteristic that the threshold voltage controlled by the output of the voltage adjustment unit changes over time.

[0117] -Invention Effects-

[0118] According to the present invention, the power converter and the power system equipped with the power converter generate a target value as the output target of the voltage fluctuation section of the power converter based on the voltage of the transmission line observed by the voltage monitoring section of the power converter. The target value has the characteristic that the threshold voltage controlled by the output of the voltage adjustment section of the power converter changes over time. As a result, when the power network is disturbed, the voltage of the transmission line electrically connected to the device via the power converter can be stabilized, and the power efficiency of the device constituting the power network can be improved.

[0119] According to the present invention, in the form of a power converter and a power system equipped with the power converter, if the threshold voltage value is set to Vr, the capacitance of the transmission line is set to C, and the time constant determined according to the capacitance is set to Tr, then a reference function having the characteristic of changing the threshold voltage for output suppression according to time has the relationship Tr = function(Vr, C). If the observed voltage at the local terminal of the power converter is set to V0, then when the state of V0 > Vr continues for more than Tr, the voltage fluctuation section of the power converter is controlled to suppress the output of power from the device to the transmission line. As a result, the voltage stabilization of the power network can be achieved more reliably, and the power efficiency of the device that outputs power can be improved more reliably.

[0120] According to the present invention, in the form of a power converter and a power system equipped with the power converter, if the threshold voltage value is set to Vr, the capacitance of the transmission line is set to C, and the time constant determined according to the capacitance is set to Tr, then a reference function having the characteristic of changing the threshold voltage for input suppression according to time has the relationship Tr = function(Vr, C). If the observed voltage at the local terminal of the power converter is set to V0, then when the state of V0 < Vr continues for more than Tr, the voltage fluctuation section of the power converter is controlled to suppress the input of power from the transmission line to the equipment, thereby more reliably stabilizing the voltage of the power network and more reliably improving the power efficiency of the equipment receiving the power supply.

[0121] According to the control method of the power converter, the control method of the power system, and the programmatic approach of the present invention, when interference occurs in the power network, it is possible to stabilize the voltage of the transmission line to which the equipment is electrically connected via the power converter, and to improve the power efficiency of the equipment constituting the power network. Attached Figure Description

[0122] Figure 1 This is an explanatory diagram showing an overview of the power network constituting a power system equipped with a power converter as an embodiment of the present invention.

[0123] Figure 2 This is an explanatory diagram illustrating the reference functions assigned to devices used in a power network that constitutes a power system equipped with a power converter as an embodiment of the present invention.

[0124] Figure 3 This is an explanatory diagram illustrating the situation where the reference function assigned to a device used in a power system equipped with a power converter as an embodiment of the present invention is updated.

[0125] Figure 4This is an example of a reference function with time-limited characteristics assigned to a solar power generation device (PV) used in a power system equipped with a power converter as an embodiment of the present invention.

[0126] Figure 5 This is a block diagram illustrating a construction example of the power converter of the present invention.

[0127] Figure 6 It is a reference function with existing time-limited characteristics assigned to solar power generation devices (PV) used in power systems equipped with power converters.

[0128] Figure 7 This is a sequence diagram illustrating an example of a control method for a power system.

[0129] Figure 8 This is an example of a reference function with time-limited characteristics assigned to a solar power generation device (PV) used in a power system equipped with a power converter as an embodiment of the present invention.

[0130] Figure 9 This is an example of a reference function with time-limited characteristics assigned to an EV charger used in a power system that has a power converter as an embodiment of the present invention. Detailed Implementation

[0131] <Implementation Method>

[0132] A power system incorporating a power converter as an embodiment of the present invention will be described. Furthermore, Figure 1 This is an explanatory diagram showing an overview of the power network constituting a power system equipped with a power converter as an embodiment of the present invention. Figure 2 This is an explanatory diagram illustrating the reference functions assigned to devices used in a power network that constitutes a power system equipped with a power converter as an embodiment of the present invention. Figure 3 This is an explanatory diagram illustrating the situation where the reference function assigned to a device used in a power system equipped with a power converter as an embodiment of the present invention is updated. Figure 4 This is an example of a reference function with time-limited characteristics assigned to a solar power generation device (PV) used in a power system equipped with a power converter as an embodiment of the present invention. Figure 5 This is a block diagram illustrating a construction example of the power converter of the present invention. Figure 7 This is a sequence diagram illustrating an example of a control method for a power system.

[0133] Furthermore, the "time-limited characteristic" of the reference function with so-called time-limited characteristics in this specification refers to the following characteristics: When an abnormal voltage with a significant impact on the voltage stability of the power transmission line to which the equipment is electrically connected is observed, the input / output of power / current is stopped during the short duration of the abnormal voltage; and when an abnormal voltage with a minor impact on the voltage stability of the power transmission line is observed, the input / output of power / current is stopped when the abnormal voltage persists for a certain period of time. Additionally, in this specification, the power transmission line is sometimes referred to simply as a line.

[0134] like Figure 1 As shown, a power system 1 formed in a power network 10 equipped with a power converter as an embodiment of the present invention includes a power converter electrically connected to an AC commercial power system 100 via a line (DC bus 19), and electrically connected to a device capable of inputting power from the line (DC bus 19) and / or outputting power to the line (DC bus 19). In other words, a power unit is provided in the power system 1, which includes a power converter electrically connected to the AC commercial power system 100 via a line (DC bus 19), and a device electrically connected to the power converter and capable of inputting power from the line (DC bus 19) and / or outputting power to the line (DC bus 19) via the power converter.

[0135] Specifically, it includes: an AC / DC converter 11, which can be connected to an AC commercial power system 100, converting AC power input from the AC commercial power system 100 into DC power and outputting it; a DC bus 19, which is connected to the output of the AC / DC converter 11; a first DC / DC converter 13, which is connected to the DC bus 19, converting DC power input from the DC bus 19 into a charging voltage for a battery to be charged and outputting it; a charger (EV charger 17 in the power network 10), which is connected to the first DC / DC converter 13 and can be connected to a battery to be charged; a bidirectional DC / DC converter 12, which is connected to the DC bus 19, converting DC power input from the DC bus 19 into a charging voltage for a stationary energy storage device 14 and outputting it; and a solar power generation device (PV) 15, which is connected to the DC bus 19 via a second DC / DC converter 16 and is a power generation device that generates electricity using renewable energy.

[0136] Based on the above, the power network 10 constituting the power system 1 is a direct current power network, i.e., a DC power grid. In the power network 10, the battery is, for example, an on-board battery mounted on an electric vehicle (EV) 18 that serves as a load. The output of the DC bus 19 is connected to the EV charger 17, and the on-board battery of the electric vehicle 18 is connected to the EV charger 17 so that the on-board battery is charged. The stationary energy storage device 14 is an in-equipment energy storage device within the power network 10.

[0137] Each power converter, as an example, has a power conversion unit, a sensor, a control unit, and a communication unit.

[0138] The power conversion section is the part of each power converter that performs AC / DC conversion or DC / DC conversion, i.e., power conversion. It is typically composed of circuits including coils, capacitors, diodes, and switching elements. Switching elements may include, for example, field-effect capacitors or insulated-gate bipolar transistors (IGBTs). The power conversion section can, for example, control its power conversion characteristics using PWM (Pulse Width Modulation) control.

[0139] Sensors are used to observe the electrical characteristics of current, voltage, and power in various power converters. The sensors output the observed electrical characteristic values ​​(current, voltage, power, etc.) to the control unit as observed values.

[0140] In the power system 1 equipped with the power grid 10, the power received from the commercial power system 100 is controlled by the control unit. In addition, the control unit controls the charging and discharging of the stationary energy storage device 14, the discharging of the solar power generation device 15, and the charging of the on-board battery of the electric vehicle 18 connected to the EV charger 17.

[0141] Each control unit comprises a processor and a storage unit that perform various computational processes for controlling power conversion functions. The processor may be, for example, a CPU (Central Processing Unit), an ASIC (Application Specific Integrated Circuit), a FPGA (Field-Programmable Gate Array), a DSP (Digital Signal Processor), or a GPU (Graphics Processing Unit). The storage unit includes, for example, ROM (Read Only Memory) for storing various programs and data used by the processor for computational processing. Furthermore, the storage unit includes, for example, RAM (Random Access Memory) for providing working space for the processor's computational processing and storing the results of the processor's computational processing. The storage unit may also include auxiliary storage devices such as HDD (Hard Disk Drive) or SSD (Solid State Drive). The functions of each control unit are implemented as functional units by the processor reading various programs from the storage unit and executing them. For example, each control unit outputs a PWM signal containing information about the operation quantities (e.g., duty cycle) for PWM (Pulse Width Modulation) to the power conversion unit to perform PWM control on each power converter. In addition, each control unit can output the operation quantity directly to the power conversion unit, or it can output it to the power conversion unit via other functional units (such as the cycle control unit) not shown.

[0142] The communication unit comprises a communication module for information communication via wired or wireless means, and a communication control unit for controlling the operation of the communication module. The communication unit communicates with the central control unit 110 (described later) via a network NW, including the Internet, mobile phone networks, etc. For example, the communication unit receives instructions from the central control unit 110 and outputs them to the control unit. For example, the communication unit sends information related to the power status input from the control unit to the central control unit 110. Furthermore, if the power status information is a sensor measurement, the communication unit can, for example, send the measurement value input from the sensor to the central control unit 110.

[0143] Here is an example of a central control unit 110. The central control unit 110 includes a control unit, a storage unit, and a communication unit. The structures of the control unit, storage unit, and communication unit can be illustrated using the structures of the control unit, storage unit, and communication unit as exemplified in a power converter.

[0144] The function of the control unit is realized by reading various programs from the storage unit and executing them.

[0145] The communications department communicates with each power converter and external server 200 via the network NW.

[0146] Furthermore, the external server 200 is a server located outside the power system 1. The external server 200 is, for example, an information processing device that functions as an energy management system (EMS) in other power systems and 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.

[0147] In power system 1, the second DC / DC converter 16 has the following function: to control the output of the solar power generation device (PV) 15 based on the target value generated when the target value of the solar power generation device (PV) 15 is controlled based on the voltage (V) observed at the local terminal of the second DC / DC converter 16.

[0148] The second DC / DC converter 16, connected to the solar power generation device (PV) 15, has the following function: controlling the operation of the solar power generation device (PV) 15 so that the relationship between its own voltage (V) and its own power (P), i.e., the relationship between its own voltage (V) and the power (P) output from the solar power generation device (PV) 15, follows a predetermined reference function. That is, the second DC / DC converter 16 performs control within a predetermined control cycle to maintain the relationship between its own voltage (V) and its own power (P) within the predetermined reference function.

[0149] As a specific example, such as Figure 2 As shown, the second DC / DC converter 16 connected to the solar power generation device (PV) 15 operates in a transitional zone of the power grid 10 where power demand is low. Figure 2 In the case of the transitional operating zone on the upper side of the medium voltage (V) value, output control of the solar power generation device (PV) 15 is implemented. Figure 2 In the case of no output from the solar power generation device (PV) 15 (i.e., power (P) = 0), maximum power point tracking control (MPPT) is implemented for the solar power generation device (PV) 15 in the other operating range. Therefore, in Figure 2 In this configuration, the output control of the solar power generation device (PV) 15 is not droop control.

[0150] Furthermore, in power system 1, other power converters besides the second DC / DC converter 16 also have the following function: controlling the operation of the equipment so as to follow the generation of a reference function that controls the target value of the equipment connected to the other power converters based on the observed voltage of the other power converters at the local end.

[0151] In power system 1, the AC / DC converter 11, which converts AC power input from the commercial power system 100 into DC power and outputs it, has the following function: performing droop control so that the relationship between the voltage (V) at its own terminal and the power (P) at its own terminal, i.e., the voltage (V) at its own terminal and the power (P) output to the DC bus 19, has a predetermined droop characteristic. That is, the AC / DC converter 11 has the following function: during a predetermined control cycle, it performs droop control on the input and output from the commercial power system 100 so that the relationship between the voltage (V) at its own terminal and the power (P) input and output to the DC bus 19 follows a reference function with a predetermined droop characteristic. Furthermore, the term "droop characteristic" refers to a characteristic where the relationship between the voltage at its own terminal and the input and output quantities of the power at its own terminal has a relationship that is either constant within a predetermined voltage range or, within a predetermined range of power input and output quantities, a relationship other than constant voltage.

[0152] As a specific example, such as Figure 2 As shown, the AC / DC converter 11 connected to the commercial power system 100, during normal operation of the power network 10, performs droop control on the input from the commercial power system 100 by setting the droop characteristic to the maximum reference function in the normal operating range, thereby enabling a stable power supply to the power network 10 centered on the power supply from the commercial power system 100. On the other hand, input-output constant domains are set to maintain constant values ​​for both the power input and output. Figure 2 (to become a vertical zone), so that: in the power network 10, it is a quasi-normal operating zone or a transitional operating zone with low power demand ( Figure 2 In the case of a quasi-normal operating zone or a transitional operating zone with a higher voltage (V) value, the power supply from the commercial power system 100 is cut off. Furthermore, in the case of a quasi-normal operating zone or a transitional operating zone where the power network 10 has a higher power demand, the power supply from the commercial power system 100 is cut off. Figure 2 In the case of the lower voltage (V) value in the quasi-normal operating area and transitional operating area, the power supply from the commercial power system 100 shall not exceed the contracted power.

[0153] The first DC / DC converter 13, which converts the DC power input from DC bus 19 into the charging voltage of the on-board battery of the electric vehicle 18 to be charged and outputs it, has the following function: It controls the output of the EV charger 17 to ensure that the relationship between its voltage (V) and power (P), i.e., the relationship between its voltage (V) and the power (P) input from DC bus 19, has a predetermined characteristic. Specifically, the first DC / DC converter 13 controls the output of the EV charger 17 during a predetermined control cycle so that the relationship between its voltage (V) and the power (P) input from DC bus 19 follows a reference function with a predetermined characteristic.

[0154] As a specific example, such as Figure 2 As shown, the first DC / DC converter 13 connected to the EV charger 17 implements phased control of the output of the EV charger 17 when the power network 10 is in a transitional operating zone with high power demand. On the other hand, when the power network 10 is in a quasi-normal operating zone with high power demand, a normal operating zone, a quasi-normal operating zone with low power demand, or a transitional operating zone with low power demand, the output of the EV charger 17 is not controlled. Figure 2 In this context, the reference function used as the control objective function of the EV charger 17 is not a reference function with droop characteristics, and the output control of the EV charger 17 is not droop control.

[0155] The bidirectional DC / DC converter 12 connected to the stationary energy storage device 14 has the following function: it performs droop control on the operation of the stationary energy storage device 14 so that the relationship between the voltage (V) at its own terminal and the power (P) at its own terminal, i.e., the relationship between the voltage (V) at its own terminal and the power (P) charged and discharged from the stationary energy storage device 14, follows a reference function with a predetermined droop characteristic. In other words, the bidirectional DC / DC converter 12 performs control within a predetermined control cycle so that the relationship between the voltage (V) at its own terminal and the power (P) at its own terminal maintains a reference function with a predetermined droop characteristic.

[0156] Specifically, such as Figure 2 As shown, the bidirectional DC / DC converter 12 connected to the stationary energy storage device 14 has a dead zone set in the normal operating region as an input-output constant domain, so that there is no charging or discharging. In the quasi-normal operating region with higher power demand, droop control is performed so that discharging is implemented through a reference function with droop characteristics. Furthermore, the bidirectional DC / DC converter 12 performs droop control in the quasi-normal operating region with lower power demand so that charging is implemented through a reference function with droop characteristics.

[0157] Based on the above, in power system 1, the system is configured to follow a predetermined reference function, such that the output of the solar power generation device (PV) 15 and the EV charging port 17 changes according to the voltage variation of the power system 1 as a whole. Furthermore, in power system 1, each power unit (each device and each power converter connected to each of the devices) implements primary control decentralizedly based on its own voltage and power supply. That is, the control of the device's operation based on the reference function is primary control, and primary control is implemented based on the local voltage of each device connected to the power converter.

[0158] Furthermore, power system 1 also includes a secondary control function that updates a reference function based on the power status of multiple power units. This secondary control is based on the relationship between the discharge quantity output from the DC bus 19, which is electrically connected to the multiple power units, and the amount of electricity received by the DC bus 19. In other words, the secondary control is a function of the primary control provided by a specified power converter, which is updated not only to reflect the power status at its own terminal but also to reflect the power status of other power converters constituting power system 1.

[0159] like Figure 3 As shown, in power system 1, secondary control comprehensively evaluates the reference functions of each power converter—AC / DC converter 11, bidirectional DC / DC converter 12, first DC / DC converter 13, and second DC / DC converter 16—to optimally update these reference functions. The updating of the reference functions for each power converter can, for example, utilize a computer with AI (artificial intelligence) capabilities.

[0160] The secondary control of updating the reference function is implemented, for example, based on instructions from the central control unit 110. Therefore, the power system 1 also has a central control unit 110 that controls each of the power converters: AC / DC converter 11, bidirectional DC / DC converter 12, first DC / DC converter 13, and second DC / DC converter 16. In the power system 1, the central control unit 110 performs secondary control on the AC / DC converter 11, bidirectional DC / DC converter 12, first DC / DC converter 13, and second DC / DC converter 16. The central control unit 110 is connected to each of the power converters, for example, via a communication mechanism. Therefore, the secondary control based on the central control unit 110 is a centralized control method. The central control unit 110 is an energy management system (EMS). In addition, primary control and secondary control, for example in each power converter or central control unit 110, cause the processor to execute programs.

[0161] For example, in secondary control, when the information communication between the central control unit 110 and each power converter is based on the TCP / IP protocol, the data portion of the IP packet of the instruction signal for function update includes function information of the reference function. For example, if the reference function has droop characteristics, the function information includes the coordinates of the boundary of the function representing the droop characteristics (droop function), the intercept information of the droop function, the slope (i.e., droop coefficient) information, and the shape (straight line, curve, etc.) information. The function information also includes information on the constant domain of the input and output. Furthermore, for function information where the reference function does not have droop characteristics, for example, in constant voltage control, it includes information representing constant voltage control, the target voltage value as the control value, the maximum power as the upper limit of power, the minimum power as the lower limit of power, etc. For example, in constant power control, it includes information representing constant power control, the target power value as the control value, etc. This information is, for example, information defined in PV coordinates. In the data portion of the IP packet, the information of the object to be updated is included as a data string. The function information used in the update is stored in the storage section of the central control unit 110, and the control unit reads and uses it appropriately.

[0162] In contrast, the operation of the solar power generation device (PV) 15, EV charger 17, etc. is controlled by a reference function and is implemented based on the voltage of the local terminal of the solar power generation device (PV) 15, EV charger 17, etc., without the instruction of the central control unit 110.

[0163] The secondary control, which updates the reference function, is implemented based on instructions from the central control unit 110. The primary control, which controls the input and output of the devices based on the reference function, is implemented without instructions from the central control unit 110, based on the voltage at the local terminals of the solar power generation device (PV) 15, EV charger 17, etc. This allows the power demand of the entire power network 10, which varies over time, to be accurately reflected in the output control of the solar power generation device (PV) 15 and EV charger 17. Therefore, the overall control of the power network 10, which includes various devices such as the solar power generation device (PV) 15 and EV charger 17, is optimized, and the required power can be supplied to the entire power network 10 effectively.

[0164] In power system 1, when the overall control of the power network 10, which includes various devices such as solar power generation devices (PV) 15 and EV chargers 17, is optimized, the reference function for controlling the operation of the solar power generation device (PV) 15 has the characteristic that the threshold voltage for output suppression, which controls the output of the solar power generation device (PV) 15, varies over time. Specifically, the reference function for controlling the operation of the solar power generation device (PV) 15 has a defined time-limited characteristic.

[0165] The reference function used to control the operation of the solar power generation device (PV) 15 has an inverse time-limited characteristic as a specified time-limited characteristic. Specifically, if the threshold voltage value is set to Vr, the capacitance of the line (DC bus 19 in power system 1) is set to C, and the time constant determined according to the capacitance is set to Tr, then the reference function with the specified time-limited characteristic has the following relationship as shown in equation (1).

[0166] Tr = function(Vr, C) (1)

[0167] Here, function(Vr, C) is a function of Vr and C. For example, if the output of the solar power generation device (PV) 15 is suppressed due to a voltage rise in the DC bus 19, function(Vr, C) is set such that the higher the threshold voltage value Vr for determining the implementation of output suppression, the shorter Tr is. Furthermore, since the capacitance C of the DC bus 19 is larger, according to the relationship Q=CV, the voltage is more difficult to change relative to changes in the input and output current (charge) of the DC bus 19, so function(Vr, C) is set such that Tr can be relatively long.

[0168] Furthermore, if the observed voltage at the local terminal of the second DC / DC converter 16 is set to V0, then when the state of V0 > Vr lasts for a time Tr (time constant Tr) or longer, the switching element of the second DC / DC converter 16 is controlled to suppress the output of power from the solar power generation device (PV) 15 to the DC bus 19.

[0169] For example, if the observed voltage V0 at the local terminal of the second DC / DC converter 16 is a voltage V1 that exceeds a predetermined value by a threshold voltage Vr, and the voltage V1 persists for a time T1 or more as a time constant Tr determined by the capacitor C, the switching elements of the second DC / DC converter 16 are suppressed so that the power output P from the solar power generation device (PV) 15 to the DC bus 19 is 0. Furthermore, if the observed voltage V0 at the local terminal of the second DC / DC converter 16 is a voltage V2 that exceeds a predetermined value by a voltage V1, and the voltage V2 persists for a time T2 or more as a time constant Tr that is shorter than T1, the switching elements of the second DC / DC converter 16 are suppressed so that the power output P from the solar power generation device (PV) 15 to the DC bus 19 is 0. Furthermore, when the observed voltage V0 at the local terminal of the second DC / DC converter 16 is a voltage V3 that exceeds a predetermined value compared to voltage V2, and voltage V3 persists as a time constant Tr for a time T3 or longer than T2, the switching elements of the second DC / DC converter 16 are suppressed so that the power output P from the solar power generation device (PV) 15 to the DC bus 19 is 0. That is, the higher the observed voltage V0, the shorter the time from when the state of V0 > Vr is observed until the power output is suppressed.

[0170] As a specific example, such as Figure 4 As shown, when the observed voltage V0 at the local terminal of the second DC / DC converter 16 is 420V, which is 20V higher than the threshold voltage Vr (for simplicity, for example, 400V), and 420V is maintained as a time constant Tr for a time T1 (for simplicity, for example, 1.0 second) or more, the switching elements of the second DC / DC converter 16 are suppressed, so that the power output P from the solar power generation device (PV) 15 to the DC bus 19 is 0. Furthermore, when the observed voltage V0 at the local terminal of the second DC / DC converter 16 is 440V, which is 40V higher than the threshold voltage Vr (e.g., 400V), and 440V is maintained as a time constant Tr for a time T2 (for simplicity, for example, 0.1 seconds) or more, the switching elements of the second DC / DC converter 16 are suppressed, so that the power output P from the solar power generation device (PV) 15 to the DC bus 19 is 0. Furthermore, when the observed voltage V0 at the local terminal of the second DC / DC converter 16 is 460V, which is 60V higher than the threshold voltage Vr (e.g., 400V), and 460V is maintained as a time constant Tr for a time T3 (for simplicity, for example, 0.01 seconds) or longer, the switching elements of the second DC / DC converter 16 are suppressed, so that the power P output from the solar power generation device (PV) 15 to the DC bus 19 is 0. Additionally, Figure 4In this context, the reference function used to control the operation of the solar power generation device (PV) 15 does not have a droop characteristic; therefore, the control of the output of the solar power generation device (PV) 15 is not droop control.

[0171] Furthermore, the reference function for controlling the operation of the solar power generation device (PV) 15 has the characteristic that the threshold voltage for output promotion, which controls the output of the solar power generation device (PV) 15, varies over time. Specifically, the reference function for controlling the output promotion operation of the solar power generation device (PV) 15 has a defined time-limited characteristic.

[0172] For example, if the threshold voltage value is set to Vr2, the capacitance of the line (DC bus 19 in power system 1) is set to C, and the time constant determined according to the capacitance is set to Tr2, then the reference function having the specified time-limited characteristics for controlling the output promotion action of the solar power generation device (PV) 15 has the following relationship (2).

[0173] Tr2 = function(Vr2, C) (2)

[0174] Here, function(Vr2, C) is a function of Vr2 and C. For example, if the output of the solar power generation device (PV) 15 is promoted due to a voltage drop in the DC bus 19, function(Vr2, C) is set such that the lower the threshold voltage value Vr2 for determining the implementation of output promotion, the shorter Tr2 is. Furthermore, since the capacitance C of the DC bus 19 is large, according to the relationship Q=CV, the voltage is difficult to change relative to the change in the amount of input and output current (charge) to the DC bus 19, so function(Vr2, C) can be set to a relatively long Tr2.

[0175] Furthermore, if the observed voltage at the local terminal of the second DC / DC converter 16 is set to V0, and the state of V0 < Vr2 lasts for a time Tr2 (time constant Tr2) or longer, the switching element of the second DC / DC converter 16 is controlled to promote the output of power from the solar power generation device (PV) 15 to the DC bus 19.

[0176] For example, when the observed voltage V0 at the local terminal of the second DC / DC converter 16 is a voltage V11 that is a predetermined value lower than the threshold voltage Vr2, and this voltage range is maintained as a time constant Tr2 determined according to the capacitor C for a time T11 or more, the switching element of the second DC / DC converter 16 increases the output power P from the solar power generation device (PV) 15 to the DC bus 19. Furthermore, when the observed voltage V0 at the local terminal of the second DC / DC converter 16 is a voltage V12 that is a predetermined value lower than the voltage V11, and this voltage range is maintained as a time constant Tr2 for a time T12 or more shorter than T11, the switching element of the second DC / DC converter 16 increases the output power P from the solar power generation device (PV) 15 to the DC bus 19. Furthermore, when the observed voltage V0 at the local terminal of the second DC / DC converter 16 is a voltage V13 lower than voltage V12, and this voltage range is maintained as a time constant Tr2 for a time T13 or longer than T12, the switching element of the second DC / DC converter 16 causes the output of power P from the solar power generation device (PV) 15 to the DC bus 19 to increase. Furthermore, when the observed voltage V0 at the local terminal of the second DC / DC converter 16 is a voltage V14 or lower than voltage V13, the switching element of the second DC / DC converter 16 causes the output of power P from the solar power generation device (PV) 15 to increase instantaneously. That is, the lower the observed voltage V0, the shorter the time from when V0 < Vr2 is observed until the output of power P increases. Additionally, the switching element of the second DC / DC converter 16 stops the increase of power P when V0 = Vr2 by causing the output of power P to increase.

[0177] As a specific example, such as Figure 8As shown, when the observed voltage V0 at the local terminal of the second DC / DC converter 16 is 400V, which is 5V lower than the threshold voltage Vr2 (for simplicity, for example, 405V), and the voltage remains below 400V for a time T11 (for simplicity, for example, 1.0 second) or more as a time constant Tr2, the switching element of the second DC / DC converter 16 increases the output power P from the solar power generation device (PV) 15 to the DC bus 19. Furthermore, when the observed voltage V0 at the local terminal of the second DC / DC converter 16 is 380V, which is 25V lower than the threshold voltage Vr2, and the voltage remains below 380V for a time constant Tr2 for a time T12 (for simplicity, for example, 0.5 seconds) or more, the switching element of the second DC / DC converter 16 increases the output power P from the solar power generation device (PV) 15 to the DC bus 19. Furthermore, when the observed voltage V0 at the local terminal of the second DC / DC converter 16 is 360V, which is 45V lower than the threshold voltage Vr2, and the voltage remains below 360V for a time T13 (for simplicity, for example, 0.1 seconds) or more as a time constant Tr2, the switching element of the second DC / DC converter 16 causes the output power P from the solar power generation device (PV) 15 to the DC bus 19 to increase. Furthermore, when the observed voltage V0 at the local terminal of the second DC / DC converter 16 is below 350V, the switching element of the second DC / DC converter 16 causes the output power P from the solar power generation device (PV) 15 to the DC bus 19 to increase instantaneously. Specifically, for example, if timing begins when the observed voltage V0 is below 400V, and if the observed voltage V0 remains between 380V and 400V for 0.4 seconds, and then remains between 360V and 380V for 0.1 seconds, the total timing time is 0.5 seconds, thus causing an increase in the power output P from the solar power generation device (PV) 15 to the DC bus 19. Furthermore, for example, if timing begins when the observed voltage V0 is below 400V, even if the observed voltage V0 remains between 380V and 400V for 0.8 seconds, and then remains below 380V, the total timing time exceeds 0.5 seconds, thus causing an immediate increase in the power output P from the solar power generation device (PV) 15 to the DC bus 19. Additionally, Figure 8 In this context, since the reference function used to control the operation of the solar power generation device (PV) 15 does not have a droop characteristic, the control of the output of the solar power generation device (PV) 15 is not droop control.

[0178] The reference function used to control the operation of the solar power generation device (PV) 15 has the characteristic that the threshold voltage for output suppression / output promotion of the solar power generation device (PV) 15 varies over time. Specifically, it has a time-limited characteristic. As a result, when interference occurs in the power network 10, the output control of the solar power generation device (PV) 15 is adjusted according to the degree of voltage fluctuation, and thus the voltage of the DC bus 19 electrically connected to the solar power generation device (PV) 15 via the second DC / DC converter 16 is also stabilized. Furthermore, by having the aforementioned time-limited characteristic, the frequency of output suppression / output promotion of the solar power generation device (PV) 15 can be suppressed, thereby improving the power efficiency of the solar power generation device (PV) 15.

[0179] Specifically, by using a reference function for controlling the operation of the solar power generation device (PV) 15, and by utilizing the threshold voltage value of the local terminal of the solar power generation device (PV) 15, the capacitance of the DC bus 19, and the time constant determined based on the capacitance of the DC bus 19, a time-limiting characteristic is added, thereby enabling more reliable voltage stabilization of the power network 10 and more reliable improvement of the power efficiency of the solar power generation device (PV) 15.

[0180] Furthermore, when the overall control of the power network 10, which includes various devices such as solar power generation devices (PV) 15 and EV chargers 17, is optimized, the reference function controlling the operation of the EV charger 17 as a load has the characteristic that the threshold voltage for suppressing the output of the EV charger 17 varies with time. Specifically, the reference function controlling the operation of the EV charger 17 has a defined time-limited characteristic.

[0181] Specifically, if the threshold voltage value is set to Vr, the capacitance of the line (DC bus 19 in power system 1) is set to C, and the time constant determined according to the capacitance is set to Tr, for example, the reference function with the specified time-limited characteristics has the following relationship (1).

[0182] Tr = function(Vr, C) (1)

[0183] Here, function(Vr, C) is a function of Vr and C, but Vr and function(Vr, C) can be the same as Vr and function(Vr, C) for the solar power generation device (PV) 15, or they can be different with respect to Tr. For example, if the output of the EV charger 17 is suppressed due to a voltage drop in the DC bus 19, function(Vr, C) is set such that the lower the threshold voltage value Vr for determining the implementation of output suppression, the shorter Tr is. Furthermore, since the capacitance C of the DC bus 19 is large, the voltage is difficult to change relative to the change in the amount of input and output current (charge) to the DC bus 19, function(Vr, C) can also be set to a relatively long Tr.

[0184] Furthermore, if the observed voltage at the local terminal of the first DC / DC converter 13 is set to V0, then when the state of V0 < Vr continues for more than Tr, the switching element of the first DC / DC converter 13 is controlled to suppress the input of power from the DC bus 19 to the EV charger 17, that is, to suppress the output from the EV charger 17 to the electric vehicle 18.

[0185] For example, when the observed voltage V0 at the local terminal of the first DC / DC converter 13 is a voltage V4 that is a predetermined value lower than the threshold voltage Vr, and the voltage V4 lasts for a time T4 or more as a time constant Tr determined by the capacitor C, the switching element of the first DC / DC converter 13 controls the input of power P from the DC bus 19 to the EV charger 17 (i.e., the output of power P from the EV charger 17 to the electric vehicle 18). That is, the switching element of the first DC / DC converter 13 suppresses the amount of charging current supplied from the DC bus 19 to the EV charger 17. Furthermore, when the observed voltage V0 at the local terminal of the first DC / DC converter 13 is a voltage V5 that is a predetermined value lower than the voltage V4, and the voltage V5 lasts for a time T5 or more that is shorter than T4 as a time constant Tr, the switching element of the first DC / DC converter 13 suppresses the input of power P from the DC bus 19 to the EV charger 17. Furthermore, when the observed voltage V0 at the local terminal of the first DC / DC converter 13 is a voltage V6 that is lower than voltage V5 by a predetermined value, if voltage V6 is sustained for a time T6 or more that is shorter than T5 (which is a time constant Tr), the switching elements of the first DC / DC converter 13 suppress the input of power P from the DC bus 19 to the EV charger 17. That is, the higher the observed voltage V0, the shorter the time from when the state of V0 > Vr is observed until the power input suppression is performed.

[0186] As a specific example, when the observed voltage V0 at the local terminal of the first DC / DC converter 13 is 340V, which is 20V lower than the threshold voltage Vr (for simplicity, for example, 360V), and 340V is maintained as a time constant Tr for a time T4 (for simplicity, for example, 1.0 second) or more, the switching elements of the first DC / DC converter 13 suppress the input of power P from the DC bus 19 to the EV charger 17, i.e., the supply of charging current. Furthermore, when the observed voltage V0 at the local terminal of the first DC / DC converter 13 is 320V, which is 40V lower than the threshold voltage Vr (e.g., 360V), and 320V is maintained as a time constant Tr for a time T5 (for simplicity, for example, 0.1 seconds) or more, the switching elements of the first DC / DC converter 13 suppress the input of power P from the DC bus 19 to the EV charger 17. Furthermore, when the observed voltage V0 at the local terminal of the first DC / DC converter 13 is 300V, which is 60V lower than the threshold voltage Vr (e.g., 360V), and 300V is maintained as a time constant Tr for a time T6 (for simplicity, for example, 0.01 seconds) or more, the switching elements of the first DC / DC converter 13 suppress the input of power P from the DC bus 19 to the EV charger 17. Since the reference function used to control the operation of the EV charger 17 does not have a droop characteristic, the control of the input to the EV charger 17 is not droop control.

[0187] Furthermore, the reference function controlling the operation of the EV charger 17 has the characteristic that the threshold voltage that promotes the output of the EV charger 17 varies with time. Specifically, the reference function controlling the operation of the EV charger 17 has a defined time-limited characteristic.

[0188] Specifically, for example, if the threshold voltage value is set to Vr3, the capacitance of the line (DC bus 19 in power system 1) is set to C, and the time constant determined according to the capacitance is set to Tr3, then the reference function with the specified time-limited characteristics has the following relationship as shown in equation (3).

[0189] Tr3 = function(Vr3, C) (3)

[0190] Here, function(Vr3, C) is a function of Vr3 and C. For example, in the case where the output of the EV charger 17 is boosted by a voltage rise in the DC bus 19, function(Vr3, C) is set such that the larger the threshold voltage value Vr3 for determining the implementation of output boosting, the shorter Tr3 is. Furthermore, since the larger the capacitance C of the DC bus 19, the more difficult it is for the voltage to change relative to changes in the amount of input and output current (charge) to the DC bus 19, function(Vr3, C) can also be set to a relatively long Tr3.

[0191] Furthermore, if the observed voltage at the local terminal of the first DC / DC converter 13 is set to V0, and the state of V0 > Vr3 continues for more than Tr3, the switching element of the first DC / DC converter 13 is controlled to promote the input from the DC bus 19 to the EV charger 17, that is, to promote the output from the EV charger 17 to the electric vehicle 18.

[0192] For example, when the observed voltage V0 at the local terminal of the first DC / DC converter 13 is a voltage V15 that exceeds a predetermined value of the threshold voltage Vr3, and this voltage range is maintained for a time T14 or more as a time constant Tr3 determined by the capacitor C, the switching element of the first DC / DC converter 13 causes the output of power P from the DC bus 19 to the EV charger 17 (i.e., the output of power P from the EV charger 17 to the electric vehicle 18) to increase. That is, the switching element of the first DC / DC converter 13 causes the supply of charging current from the DC bus 19 to the EV charger 17 to increase. Furthermore, when the observed voltage V0 at the local terminal of the first DC / DC converter 13 is a voltage V16 that exceeds a predetermined value of the voltage V15, and this voltage range is maintained for a time T15 or more as a time constant Tr3 determined by the capacitor C that is shorter than T14, the switching element of the first DC / DC converter 13 causes the output of power P from the DC bus 19 to the EV charger 17 to increase. Furthermore, when the observed voltage V0 at the local terminal of the first DC / DC converter 13 is a voltage V17 that exceeds a predetermined value compared to voltage V16, and this voltage range is maintained for a time T16 or more shorter than T15 as a time constant Tr3 determined according to capacitor C, the switching element of the first DC / DC converter 13 causes the power P output from the DC bus 19 to the EV charger 17 to increase. Furthermore, when the observed voltage V0 at the local terminal of the first DC / DC converter 13 is a voltage V18 or more that exceeds a predetermined value compared to voltage V17, the switching element of the first DC / DC converter 13 causes the power P output from the DC bus 19 to the EV charger 17 to increase instantaneously. That is, the higher the observed voltage V0, the shorter the time from when V0 > Vr3 is observed until power output is boosted.

[0193] As a specific example, such as Figure 9As shown, when the observed voltage V0 at the local terminal of the first DC / DC converter 13 is 350V, which is 5V higher than the threshold voltage Vr3 (for simplicity, for example, 345V), and the voltage is maintained above 350V for a time T14 (for simplicity, for example, 1.0 second) or more as a time constant Tr3, the switching element of the first DC / DC converter 13 increases the input of power P from the DC bus 19 to the EV charger 17, i.e., the supply of charging current. Furthermore, when the observed voltage V0 at the local terminal of the first DC / DC converter 13 is 360V, which is 15V higher than the threshold voltage Vr3, and the voltage is maintained above 360V for a time T15 (for simplicity, for example, 0.5 seconds) or more as a time constant Tr3, the switching element of the first DC / DC converter 13 increases the input of power P from the DC bus 19 to the EV charger 17. Furthermore, when the observed voltage V0 at the local terminal of the first DC / DC converter 13 is 370V, which is 25V higher than the threshold voltage Vr3, and the voltage is maintained above 370V for a time T16 (for simplicity, for example, 0.1 seconds) or more as a time constant Tr3, the switching element of the first DC / DC converter 13 causes the power P input from the DC bus 19 to the EV charger 17 to increase. Furthermore, when the observed voltage V0 at the local terminal of the first DC / DC converter 13 is 380V or more, which is 35V higher than the threshold voltage Vr3, the switching element of the first DC / DC converter 13 causes the power P input from the DC bus 19 to the EV charger 17 to increase instantaneously. Since the reference function used to control the operation of the EV charger 17 does not have a droop characteristic, the control of the output of the EV charger 17 is not droop control.

[0194] In addition, a reference function with time-limited characteristics can be used as a method to limit the input to the EV charger 17. For example, a method to suppress the amount of charging current to the EV charger 17 is listed. In the case of multiple EV chargers 17, a method to maintain the amount of charging current to a portion of the EV chargers 17 in a stable state and to cut off the supply of charging current to another portion of the EV chargers 17 is listed.

[0195] The reference function for controlling the operation of the EV charger 17 as a load has the characteristic described above that the threshold voltage for input suppression / input promotion to the EV charger 17 varies over time; specifically, it has a time-limited characteristic. Therefore, when an disturbance occurs in the power network 10, the input control to the EV charger 17 is adjusted according to the degree of voltage fluctuation, and thus the voltage of the DC bus 19 electrically connected to the EV charger 17 via the first DC / DC converter 13 is stabilized. Furthermore, by having the aforementioned time-limited characteristic, the frequency of input suppression / input promotion to the EV charger 17 (i.e., output suppression / output promotion from the EV charger 17 to the electric vehicle 18) can be suppressed, thereby improving the power efficiency of the EV charger 17.

[0196] Specifically, by using a reference function for controlling the operation of the EV charger 17, and by adding a time-limiting characteristic using the threshold voltage value of the EV charger 17 at its local end, the capacitance of the DC bus 19, and a time constant determined based on the capacitance of the DC bus 19, the voltage stabilization of the power network 10 can be achieved more reliably, and the power efficiency of the EV charger 17 receiving the power supply can be improved more reliably.

[0197] Next, specific structural examples of the power converters, such as the first DC / DC converter 13 and the second DC / DC converter 16, will be described. Here, the second DC / DC converter 16 will be used as an example for explanation.

[0198] like Figure 5 As shown, the power converter (second DC / DC converter 16) includes: an input section 16a, and a device capable of inputting power from the line (DC bus 19) and / or outputting power to the line. Figure 5 The solar power generation device (PV) 15 is electrically connected in the middle; a voltage fluctuation unit 16b is a switching element connected to the input unit 16a that fluctuates the voltage; a voltage adjustment unit 16c is connected to the voltage fluctuation unit 16b and the line, and adjusts the voltage supplied to the line; a target setting unit 16d sets a first target value for the voltage fluctuation unit 16b; a voltage monitoring unit 16g is connected to the line and observes the voltage of the line; a threshold judgment mechanism 16e is connected to the voltage monitoring unit 16g and the target setting unit 16d, and calculates a second target value for the voltage adjustment unit 16c based on the voltage of the line. The threshold judgment mechanism 16e functions as a determination unit that judges whether the voltage value observed by the voltage monitoring unit 16g is abnormal. In addition, a memory 16f is connected to the threshold judgment mechanism 16e. The memory 16f is a storage unit that stores a table showing the relationship between the voltage (voltage magnitude, voltage duration) exceeding or falling below the specified value relative to the above-mentioned threshold voltage value and the voltage time constant Tr.

[0199] In the second DC / DC converter 16, based on the voltage of the DC bus 19 line observed by the voltage monitoring unit 16g, the target setting unit 16d generates a first target value as the output target of the voltage fluctuation unit 16b. This first target value has the characteristic that the threshold voltage that suppresses the output of the voltage adjustment unit 16c changes over time.

[0200] That is, the reference function, which serves as the control objective function, generates a first target value for local control of the device (solar power generation device 15) based on the voltage of the line (DC bus 19) observed by the voltage monitoring unit 16g, and the second DC / DC converter 16 controls the solar power generation device 15 according to the reference function.

[0201] Additionally, the input unit 16a has, for example, electrical terminals. The voltage fluctuation unit 16b and the voltage adjustment unit 16c correspond to a power conversion unit with power conversion function. The target setting unit 16d, the threshold judgment mechanism 16e, and the memory 16f correspond to a control unit for controlling the power conversion function. The voltage monitoring unit 16g corresponds to a sensor used to observe electrical characteristics.

[0202] (Control methods for power systems)

[0203] Next, refer to Figure 7 The sequence diagram is used to illustrate an example of a centralized control method for power systems.

[0204] First, in step S201, the central control unit 110 calls the timer of the self-operated device to start timing. Next, in step S202, the central control unit 110 requests local measurement information from each power converter. The so-called local measurement information is an example of information related to the power status of the power system 1, including the measurement values ​​and measurement times measured by the sensors of each power converter.

[0205] Next, in step S203, each power converter sends its local measurement information to the central control unit 110. The central control unit 110 stores the local measurement information in its storage unit.

[0206] Next, in step S204, as an example of information related to the power status of power system 1, the central control unit 110 requests various information from the external server 200 that may affect the operation of power system 1. In this example, the central control unit 110 requests power generation / demand forecast information from the external server 200. The power generation / demand forecast information includes forecast information on power generation in power system 1 and forecast information on power demand, and may also include information such as the season, current weather, and future weather forecasts for the region where power system 1 is located. Furthermore, if the external server 200 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 forecast information on power generation and power demand in that other power system.

[0207] Next, in step S205, the external server 200 sends power generation / demand forecast information to the central control unit 110. The central control unit 110 stores the power generation / demand forecast information in its storage unit.

[0208] Next, in step S206, the control unit of the central control unit 110 reads the various information sent from the storage unit, namely information related to the power status of the power system 1, and performs an operation optimization calculation of the power system 1 based on this.

[0209] Optimized calculations are performed to suit various conditions. For example, power system 1 is controlled to operate at a predetermined voltage level for DC bus 19. In this state, the central control unit 110, based on power generation / demand forecast information, anticipates that the area where the solar power generation device 15 is located will experience sunny weather in the future, resulting in increased power generation. Furthermore, based on local measurement information obtained from the second DC / DC converter 16 connected to the solar power generation device 15, it determines that there is a power surplus in the solar 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 fixed energy storage device 14, so that the fixed energy storage device 14 is charged at this operating point. Additionally, the central control unit 110 determines to update the reference function of the AC / DC converter 11 simultaneously with this update, so that no power is supplied from the commercial power system 100. Alternatively, the reference function may be switched instead of updated.

[0210] Furthermore, by using optimization calculations, conditions can be set and implemented from the perspectives of peak shaving, efficient use of nighttime electricity, and contracted electricity that will not exceed 100% of the commercial power system, as well as from the perspective of optimizing electricity costs.

[0211] Furthermore, the storage unit of the central control unit 110 can also store the learned model, which the central control unit 110 uses to perform application optimization calculations. The learned model can be, for example, a learned model generated using deep learning of a neural network, taking information related to the power status of the power system 1 and the update results of reference functions for each corresponding power converter as teaching data.

[0212] Next, in step S207, the central control unit 110 outputs an update instruction for the reference function to each power converter that is being updated, 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 local control. These local controls reflect the power status of power system 1, and all power converters are controlled in a coordinated manner.

[0213] Next, other embodiments of the power converter and power system of the present invention will be described. In the power converter and power system of the above embodiments, a solar power generation device (PV) 15 is provided as a power generation device using a reference function with added time-limited characteristics; however, a power generation device that generates electricity using fuel may be used instead. Furthermore, in the power converter and power system of the above embodiments, an EV charger 17 is provided as a load; however, other loads such as a residence may be provided instead of the EV charger 17 or together with the EV charger 17. Figure 5 As shown in the load L), the other loads mentioned above can also be connected to the AC / DC converter 11.

[0214] In the power converter and power system described above, the reference function with added time-limited characteristics is configured to change the amount of power input and output at the local terminal according to the change in voltage at the local terminal. However, it can also be configured to change the amount of current input and output at the local terminal according to the change in voltage at the local terminal.

[0215] Furthermore, as a way to make the relationship between the voltage and the power at this terminal follow a reference function with additional finite-time characteristics, for example, the power converter can observe the voltage at this terminal and set the power of the target value according to the reference function, so that the power follows the power of the target value, or the power converter can observe the power at this terminal and set the voltage of the target value according to the reference function, so that the voltage follows the voltage of the target value.

[0216] Furthermore, in the power system of the above embodiment, other power converters besides the second DC / DC converter 16 connected to the solar power generation device (PV) 15 as a power generation device and / or the first DC / DC converter 13 connected to the EV charger 17 as a load also control the operation of the equipment, so that they follow the reference function that generates the target value when controlling the equipment connected to the other power converters based on the observed voltage of the other power converters. However, it is also possible that the control of the second DC / DC converter 16 and / or other power converters besides the first DC / DC converter 13 is not based on the reference function.

[0217] Furthermore, in the power system of the above embodiment, a central control unit 110 is separately provided. The central control unit 110 centrally implements the updating of the reference function as secondary control. However, it can also be replaced by not implementing secondary control based on the central control unit. Furthermore, in the power system of the above embodiment, the central control unit centrally implements secondary control. However, it can also be replaced by at least one of the multiple power converters being configured to have the function of a central control unit controlling the multiple power converters.

[0218] Industrial availability

[0219] The power converter and power system of the present invention can stabilize voltage and improve the power efficiency of the equipment constituting the power network when interference occurs in the power network. Therefore, it has high application value, especially in the field of DC power grids with local power generation and local consumption.

[0220] Explanation of symbols

[0221] 1. Power System

[0222] 10. Power Grid

[0223] 11 AC / DC converter

[0224] 12 Bidirectional DC / DC Converter

[0225] 13. First DC / DC Converter

[0226] 14. Stationary energy storage devices

[0227] 15 Solar power generation devices

[0228] 16. Second DC / DC Converter

[0229] 16a Input Section

[0230] 16b Voltage Variation Section

[0231] 16c Voltage Regulator

[0232] 16d Target Setting Department

[0233] 16e Threshold Judgment Mechanism

[0234] 16f memory

[0235] 16g Voltage Monitoring Unit

[0236] 17 EV charger

[0237] 19 DC bus.

Claims

1. A power converter is connected to a power transmission line, and the power converter includes: An input section is electrically connected to a device capable of inputting power from the power transmission line and / or outputting power to the power transmission line; A voltage variation section is connected to the input section to vary the voltage; A voltage adjustment section is connected to the voltage variation section to adjust the voltage sent to the power transmission line; A target setting section defines a first target value for the voltage variation section; A voltage monitoring section is connected to the power transmission line to observe the voltage of the power transmission line; And A threshold judgment mechanism is connected to the voltage monitoring section to calculate a second target value for the voltage adjustment section based on the voltage of the power transmission line, In the power converter, the first target value is generated by the target setting section as the output target of the voltage variation section according to the voltage observed by the voltage monitoring section, The first target value has a characteristic that the threshold voltage for controlling the output of the voltage adjustment section varies with time, Based on a reference function that generates the first target value for local control of the device according to the voltage observed by the voltage monitoring section, the device is controlled.

2. The power converter according to claim 1, wherein The reference function has a specified time-limited characteristic.

3. The power converter according to claim 1, wherein If the threshold voltage value is set as Vr, the capacitance of the power transmission line is set as C, and the time constant determined according to the capacitance is set as Tr, then the reference function has the relationship of the following formula (1), Tr = function(Vr, C) (1) If the observed voltage at the local end of the power converter is set as V0, when the state of V0 > Vr lasts for more than Tr, the voltage variation section performs control to suppress the output of power from the device to the power transmission line.

4. The power converter according to claim 1, wherein If the threshold voltage value is set as Vr, the capacitance of the power transmission line is set as C, and the time constant determined according to the capacitance is set as Tr, then the reference function has the relationship of the following formula (1), Tr = function(Vr, C) (1) If the observed voltage at the local end of the power converter is set as V0, when the state of V0 < Vr lasts for more than Tr, the voltage variation section performs control to promote the output of power from the device to the power transmission line and stop the output promotion when V0 reaches Vr.

5. The power converter according to claim 3 or 4, wherein The device is a power generation device.

6. The power converter according to claim 5, wherein The power generation device is a power generation device that generates power using renewable energy or a power generation device that generates power using fuel.

7. The power converter according to claim 1, wherein If the threshold voltage value is set as Vr, the capacitance of the power transmission line is set as C, and the time constant determined according to the capacitance is set as Tr, then the reference function has the relationship of the following formula (1), Tr = function(Vr, C) (1) If the observed voltage at the local end of the power converter is set as V0, when the state of V0 < Vr lasts for Tr or more, the voltage variation unit performs control to suppress the input of power from the power transmission line to the device.

8. The power converter according to claim 1, wherein If the threshold voltage value is set as Vr, the capacitance of the power transmission line is set as C, and the time constant determined according to the capacitance is set as Tr, the reference function has the relationship of the following formula (1), Tr = function(Vr, C) (1) If the observed voltage at the local end of the power converter is set as V0, when the state of V0 > Vr lasts for Tr or more, the voltage variation unit performs control to: promote the input of power from the power transmission line to the device, and stop the input promotion when V0 reaches Vr.

9. The power converter according to claim 7 or 8, wherein The device is a load.

10. The power converter according to claim 9, wherein The load is an EV charger for charging an in-vehicle battery mounted on an electric vehicle.

11. A power system is provided with a power unit, and the power unit includes a power converter and a device electrically connected to the power converter, The power converter includes: An input unit electrically connected to a device capable of inputting power from a power transmission line and / or outputting power to the power transmission line; A voltage variation unit connected to the input unit to vary the voltage; A voltage adjustment unit connected to the voltage variation unit to adjust the voltage sent to the power transmission line; A target setting unit that specifies a first target value of the voltage variation unit; A voltage monitoring unit connected to the power transmission line to observe the voltage of the power transmission line; And A threshold judgment mechanism connected to the voltage monitoring unit to calculate a second target value of the voltage adjustment unit according to the voltage of the power transmission line, In the power converter, according to the voltage observed by the voltage monitoring unit, the first target value is generated by the target setting unit as the output target of the voltage variation unit, The first target value has the characteristic of making the threshold voltage for output control of the voltage adjustment unit change with time, The power system has the following function: controlling the device based on a reference function that generates the first target value for local control of the device according to the voltage observed by the voltage monitoring unit.

12. The power system according to claim 11, wherein The reference function has a specified time-limited characteristic.

13. The power system according to claim 11, wherein If the threshold voltage value is set as Vr, the capacitance of the power transmission line is set as C, and the time constant determined according to the capacitance is set as Tr, the reference function has the relationship of the following formula (1), Tr = function(Vr, C) (1) If the observed voltage at the local end of the power converter is set as V0, when the state of V0 > Vr lasts for more than Tr, the voltage variation unit performs control to suppress the power output from the device to the power transmission line.

14. The power system according to claim 11, wherein if the threshold voltage value is set as Vr, the capacitance of the power transmission line is set as C, and the time constant determined according to the capacitance is set as Tr, the reference function has the following relationship of formula (1), Tr = function(Vr, C) (1) If the observed voltage at the local end of the power converter is set as V0, when the state of V0 < Vr lasts for more than Tr, the voltage variation unit performs control to: promote the power output from the device to the power transmission line, and stop the output promotion when V0 reaches Vr.

15. The power system according to claim 13 or 14, wherein the device is a power generation device.

16. The power system according to claim 15, wherein the power generation device is a power generation device that generates electricity using renewable energy or a power generation device that generates electricity using fuel.

17. The power system according to claim 11, wherein if the threshold voltage value is set as Vr, the capacitance of the power transmission line is set as C, and the time constant determined according to the capacitance is set as Tr, the reference function has the following relationship of formula (1), Tr = function(Vr, C) (1) If the observed voltage at the local end of the power converter is set as V0, when the state of V0 < Vr lasts for more than Tr, the voltage variation unit performs control to suppress the power input from the power transmission line to the device.

18. The power system according to claim 11, wherein if the threshold voltage value is set as Vr, the capacitance of the power transmission line is set as C, and the time constant determined according to the capacitance is set as Tr, the reference function has the following relationship of formula (1), Tr = function(Vr, C) (1) If the observed voltage at the local end of the power converter is set as V0, when the state of V0 > Vr lasts for more than Tr, the voltage variation unit performs control to: promote the power input from the power transmission line to the device, and stop the input promotion when V0 reaches Vr.

19. The power system according to claim 17 or 18, wherein the device is a load.

20. The power system according to claim 19, wherein the load is an EV charger for charging an in-vehicle battery mounted on an electric vehicle.

21. The power system according to any one of claims 11 to 14, 17, and 18, wherein the power transmission line is a DC bus.

22. A control method for a power converter, the power converter being connected to a transmission line, and the input section of the power converter being connected to a device capable of inputting power from the transmission line and / or outputting power to the transmission line, the control method for the power converter comprising: The step of changing the voltage using a voltage regulating unit connected to the input unit; The step of adjusting the voltage supplied to the power transmission line by a voltage adjustment unit connected to the voltage fluctuation unit; The prescribed steps are performed on the first target value of the voltage fluctuation unit; The steps for observing the voltage of the power transmission line; and The step of calculating the second target value of the voltage adjustment unit based on the observed voltage of the transmission line. The first target value is generated based on the observed voltage of the transmission line, which serves as the output target of the voltage fluctuation unit. The first target value has the characteristic that the threshold voltage controlled by the output of the voltage adjustment unit changes with time. The device is controlled based on a reference function that generates the first target value for local control of the device according to the observed voltage.

23. A control method for a power system, wherein the power system includes a power unit, the power unit comprising a power converter and equipment electrically connected to the power converter. The power converter is connected to a transmission line, and the input section of the power converter is connected to a device capable of inputting power from the transmission line and / or outputting power to the transmission line. The control method of the power system includes: The step of changing the voltage using a voltage regulating unit connected to the input unit; The step of adjusting the voltage supplied to the power transmission line by a voltage adjustment unit connected to the voltage fluctuation unit; The prescribed steps are performed on the first target value of the voltage fluctuation unit; The steps for observing the voltage of the power transmission line; and The step of calculating the second target value of the voltage adjustment unit based on the observed voltage of the transmission line. The first target value is generated based on the observed voltage of the transmission line, which serves as the output target of the voltage fluctuation unit. The first target value has the characteristic that the threshold voltage controlled by the output of the voltage adjustment unit changes with time. The power system has the following function: to control the device based on a reference function that generates a first target value for local control of the device according to the observed voltage.

24. A control method for a power system, wherein the power system includes a power unit, the power unit comprising a power converter and equipment electrically connected to the power converter. The power converter is connected to the power transmission line, and the input section of the power converter is connected to the device capable of inputting power from the power transmission line and / or outputting power to the power transmission line. The power system includes a central control device, which is capable of communicating with the power converter and an external server storing power demand information. The control method of the power system includes: The step of changing the voltage using a voltage regulating unit connected to the input unit; The step of adjusting the voltage supplied to the power transmission line by a voltage adjustment unit connected to the voltage fluctuation unit; The prescribed steps are performed on the first target value of the voltage fluctuation unit; The steps for observing the voltage of the power transmission line; The step of calculating the second target value of the voltage adjustment unit based on the observed voltage of the transmission line; and The step of obtaining the requirement information from the external server. The first target value is generated based on the observed voltage of the transmission line, which serves as the output target of the voltage fluctuation unit. The first target value has the characteristic that the threshold voltage controlled by the output of the voltage adjustment unit changes with time. The power system has the following function: to control the device based on a reference function that generates a first target value for local control of the device according to the observed voltage.

25. A computer-readable recording medium containing a program that causes a processor to execute a control method for a power converter connected to a power transmission line, and the input section of the power converter being connected to a device capable of inputting power from the power transmission line and / or outputting power to the power transmission line, the control method for the power converter comprising: The step of changing the voltage using a voltage regulating unit connected to the input unit; The step of adjusting the voltage supplied to the power transmission line by a voltage adjustment unit connected to the voltage fluctuation unit; The prescribed steps are performed on the first target value of the voltage fluctuation unit; The steps for observing the voltage of the power transmission line; and The step of calculating the second target value of the voltage adjustment unit based on the observed voltage of the transmission line. The first target value is generated based on the observed voltage of the transmission line, which serves as the output target of the voltage fluctuation unit. The first target value has the characteristic that the threshold voltage controlled by the output of the voltage adjustment unit changes with time. The device is controlled based on a reference function that generates the first target value for local control of the device according to the observed voltage.

26. A computer-readable recording medium containing a program that causes a processor to execute a control method for a power system, the power system comprising a power unit having a power converter and a device electrically connected to the power converter, the power converter being connected to a transmission line, and the input portion of the power converter being connected to the device capable of inputting power from the transmission line and / or outputting power to the transmission line, the control method for the power system comprising: The step of changing the voltage using a voltage regulating unit connected to the input unit; The step of adjusting the voltage supplied to the power transmission line by a voltage adjustment unit connected to the voltage fluctuation unit; The prescribed steps are performed on the first target value of the voltage fluctuation unit; The steps for observing the voltage of the power transmission line; and The step of calculating the second target value of the voltage adjustment unit based on the observed voltage of the transmission line. The first target value is generated based on the observed voltage of the transmission line, which serves as the output target of the voltage fluctuation unit. The first target value has the characteristic that the threshold voltage controlled by the output of the voltage adjustment unit changes with time. The power system has the following function: to control the device based on a reference function that generates a first target value for local control of the device according to the observed voltage.

Images