Control equipment and power systems

Abstract

The present invention provides a control device that can perform appropriate settings depending on whether or not there is a connection between the higher-level system and the microgrid, without burdening the workers. [Solution] The control equipment included in the microgrid includes a voltage input unit that receives the voltage input from the distribution lines within the microgrid. When the microgrid is in a first state, connected to a higher-level system, the voltage input unit receives the voltage input from the higher-level system via the distribution lines, and when the microgrid is in a second state, disconnected from the higher-level system, it receives the voltage input from the main power supply unit included in the microgrid via the distribution lines. The control equipment further includes a monitoring unit that monitors the input voltage input to the voltage input unit and determines whether the microgrid is in the first or second state based on the results of the monitoring, and a setting unit that sets the set value of the control equipment based on the determination result of the monitoring unit.

Description

Technical Field

[0001] The present disclosure relates to a control device and a power system.

Background Art

[0002] A power system is composed of devices related to power generation, transmission, and consumption, including, for example, power plants, substations, power transmission and distribution lines, towers, switches, substations, protective relays, distributed power sources, etc. With these devices, it is possible to supply power to many consumers and a wide area, and a large-scale power system is being operated. On the other hand, in recent years, stable power supply has been demanded even during power outages due to natural disasters, etc., and microgrids that can be operated separately from large-scale power systems have attracted attention.

[0003] Japanese Unexamined Patent Application Publication No. 2023-75985 (Patent Document 1) discloses a microgrid control system. This system includes a first intelligent electronic device that detects the open / closed state of a switch that connects a microgrid and a higher-level system, a protection relay that disconnects a consumer from the microgrid when an accident current is detected, and a second intelligent electronic device that sets a setting value corresponding at least to the open / closed state of the switch in the protection relay.

Prior Art Documents

Patent Documents

[0004] [[ID=**************]]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Patent Document 1 describes how an intelligent electronic device (IED) detects the open / closed state of a switch connecting a higher-level system and a microgrid, and transmits a notification indicating that open / closed state to other IEDs via a network. The other IEDs then set a setting value for the protective relay according to the open / closed state indicated in the received notification. Patent Document 1 explores how this can enable the detection of fault current in the protective relay even when switching between island mode and grid connection mode.

[0006] In Patent Document 1, in order for IEDs to set appropriate values ​​for protective relays, each IED needs to be connected via a network. However, in many existing facilities, such a network is not already in place. In this case, there is a problem in that constructing a new network would incur significant costs. It is also conceivable that workers would have to go to the installation location of each protective relay to perform various settings, but this would be a great burden on the workers.

[0007] In one aspect of this disclosure, the objective is to provide control equipment and a power system that can be appropriately configured depending on whether or not there is a connection between the higher-level system and the microgrid, without burdening workers. [Means for solving the problem]

[0008] According to one embodiment, a control device included in a microgrid is provided. The control device includes a voltage input unit that receives voltage input from a distribution line within the microgrid. When the microgrid is in a first state, connected to a higher-level system, the voltage input unit receives voltage input from the higher-level system via the distribution line, and when the microgrid is in a second state, disconnected from the higher-level system, it receives voltage input from a main power supply unit included in the microgrid via the distribution line. The control device further includes a monitoring unit that monitors the input voltage input to the voltage input unit and determines whether the microgrid is in the first or second state based on the results of the monitoring, and a setting unit that sets a set value for the control device based on the determination result of the monitoring unit.

[0009] A power system according to another embodiment comprises a control device and a main power supply unit included in a microgrid. The control device includes a voltage input unit that receives voltage input from distribution lines within the microgrid. The voltage input unit receives voltage input from the upstream system via the distribution lines when the microgrid is in a first state, connected to an upstream system, and receives voltage input from the main power supply unit via the distribution lines when the microgrid is in a second state, disconnected from the upstream system. The control device further includes a monitoring unit that monitors the input voltage input to the voltage input unit and determines whether the microgrid is in the first or second state based on the results of said monitoring, and a setting unit that sets a set value for the control device based on the determination result of the monitoring unit. [Effects of the Invention]

[0010] According to this disclosure, appropriate settings can be made depending on whether or not the microgrid is connected to the higher-level system, without burdening workers. [Brief explanation of the drawing]

[0011] [Figure 1] This diagram shows the overall configuration of the power system. [Figure 2] This figure shows an example of the hardware configuration of a protective relay. [Figure 3]This is a block diagram showing an example of the functional configuration of a protective relay. [Figure 4] This is a block diagram showing a modified functional configuration of a protective relay. [Figure 5] This flowchart shows an example of the procedure for handling protective relays. [Modes for carrying out the invention]

[0012] This embodiment will be described below with reference to the drawings. In the following description, identical parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed descriptions of them will not be repeated.

[0013] <Overall Structure> Figure 1 shows the overall configuration of the power system. Referring to Figure 1, the power system 1000 includes switches 21 and 22, a microgrid 100, and a higher-level system 200. The microgrid 100 includes distribution lines 30, consumer facilities 110_1, 110_2, and 110_3 (hereinafter also collectively referred to as "consumer facilities 110"), and small-scale power plants 120. Distribution lines 30 are, for example, 6.6kV distribution lines.

[0014] The upstream system 200 is a large-scale power system operated by power companies, etc., and includes transmission systems and large-scale power plants, etc. The upstream system 200 is configured to allow power to be supplied from multiple power plants, for example.

[0015] The microgrid 100 is a system capable of receiving power from and transmitting power to the higher-level system 200. The microgrid 100 is connected to the higher-level system 200 via switch 21. The microgrid 100 may also be connected to other microgrids 100 or to other higher-level systems via switch 22. When switches 21 and 22 are closed, the microgrid 100 is connected to the higher-level system 200. Hereinafter, the power operation mode when the microgrid 100 is connected to the higher-level system 200 (hereinafter also referred to as the "connected state") will also be referred to as the "normal operation mode".

[0016] On the other hand, when switches 21 and 22 are open, the microgrid 100 is disconnected from the higher-level system 200. Hereinafter, the power operation mode when the microgrid 100 is disconnected from the higher-level system 200 (hereinafter also referred to as the "disconnected state") will also be referred to as the "microgrid operation mode". The switching control of switches 21 and 22 is performed using a control device (not shown) in accordance with the instructions of the operator of the power system 1000 (e.g., power company, microgrid operator, etc.).

[0017] As indicated by the "Normal Power Transmission Direction" arrow in Figure 1, under normal conditions when switches 21 and 22 are closed, power from the upstream system 200 is supplied to the distribution lines 30 installed in the microgrid 100. In this case, the microgrid 100 is in a state where it can receive power from the upstream system 200.

[0018] On the other hand, in an emergency when switches 21 and 22 are open, power from the main power supply unit 60 included in the small-scale power plant 120 installed in the microgrid 100 is supplied to the distribution line 30, as indicated by the "Emergency Power Transmission Direction" arrow. In this case, the microgrid 100 is not receiving power from the higher-level system 200. An emergency is envisioned, for example, when a large-scale earthquake, a large typhoon, etc., damages the power plants, transmission towers, etc., of the higher-level system 200, making it difficult to supply power from the higher-level system 200 to the microgrid 100.

[0019] The customer equipment 110_1 includes a protective relay 50_1 and a load 40. The load 40 includes electrical equipment that consumes power. The load 40 receives power supply via a distribution line 30. The protective relay 50_1 is an example of control equipment included in the customer equipment. Note that the control equipment may be a current source, a slave station, a storage device, etc. provided within the customer equipment.

[0020] The protective relay 50_1 performs various protection relay operations (such as current differential relay operation, distance relay operation, overcurrent relay operation, etc.) using the electrical quantities input from an instrument transformer (e.g., instrument current transformer, instrument voltage transformer) not shown in the figure. The protective relay 50_1 determines whether an accident such as a short circuit or ground fault has occurred in the protected object based on the result of the protection relay operation. For example, when the operation value of the protection relay operation exceeds (or is less than) the setting value, the protective relay 50_1 determines that the accident has occurred. When the protective relay 50_1 determines that an accident has occurred, it outputs an opening command (e.g., a trip signal) to the circuit breaker provided within the customer equipment 110_1 to open the circuit breaker. Thereby, the connection between the load 40 and the distribution line 30 is interrupted.

[0021] The configurations of the customer equipment 110_2 and 110_3 are the same as that of the customer equipment 110_1. However, the customer equipment 110_2 and 110_3 may include equipment (e.g., slave station, storage device, etc.) not provided in the customer equipment 110_1.

[0022] The small-scale power plant 120 is a power supply source that supplies power to the microgrid 100 through solar power generation, wind power generation, or other power generation. Specifically, the small-scale power plant 120 includes a protective relay 50_2 and a main power supply device 60. The protective relay 50_2 has the same function as the protective relay 50_1. When the protective relay 50_2 determines that an accident has occurred, it outputs an opening command to the circuit breaker provided within the small-scale power plant 120 to open the circuit breaker. Thereby, the connection between the main power supply device 60 and the distribution line 30 is interrupted.

[0023] The main power supply unit 60 is composed of power sources capable of ensuring the power quality of the microgrid 100. The main power supply unit 60 may be composed of power sources utilizing renewable energy such as solar power generation and wind power generation, or it may be composed of power sources such as storage batteries, small-scale hydroelectric power generation, geothermal power generation, and engine generators that use gasoline as fuel. The main power supply unit 60 stops supplying power in the normal operating mode when the microgrid 100 is connected to the higher-level system 200, and starts supplying power in the microgrid operating mode when the microgrid 100 is disconnected from the higher-level system 200.

[0024] Here, the settings for protective relays 50_1 and 50_2 (hereinafter collectively referred to as "protective relay 50") are basically made before the operation of the power system 1000, and the settings of protective relay 50 are rarely changed during operation. This is because the power system 1000 is often operated for long periods of time.

[0025] However, if a disaster or other event causes a power outage in the higher-level system 200, and the operator of the power system 1000 (e.g., a power company) switches from normal operation mode to microgrid operation mode, it is necessary to change the settings of the protective relay 50 in accordance with this switch. This is because, in microgrid operation mode, the magnitude of the fault current changes due to a decrease in short-circuit capacity and a reduction in system size. In particular, it is necessary to change the setting values ​​of the protective relay 50 in order to prevent malfunctions and failures of the protective relay 50.

[0026] During the above-mentioned switchover, it is conceivable to change the setting values ​​of each protective relay 50 installed within the microgrid 100 by transmitting setting values ​​for the microgrid operation mode to each protective relay 50. However, since many of the existing protective relays 50 are not connected to a communication network, establishing a new communication environment would incur significant costs.

[0027] Therefore, in this embodiment, the protective relay 50 has the function of monitoring the voltage received via the distribution line 30 and determining, based on the monitoring results, whether the current operating mode is normal operating mode or microgrid operating mode. As will be described in detail later, the main power supply unit 60 is configured to output voltage to the distribution line 30 in a different manner than the upstream system 200. This allows the protective relay 50 to determine whether the voltage received via the distribution line 30 was supplied from the upstream system 200 or the main power supply unit 60. The protective relay 50 sets an appropriate setting value according to this determination.

[0028] <Hardware Configuration> Figure 2 shows an example of the hardware configuration of a protective relay. Referring to Figure 2, the protective relay 50 includes an auxiliary transformer 51, a signal conversion unit 52, and an arithmetic processing unit 70.

[0029] The auxiliary transformer 51 takes in the amount of electricity detected by the instrument transformer and converts it into a voltage signal suitable for signal processing in the relay's internal circuitry, then outputs it. The signal conversion unit 52 takes in the voltage signal output from the auxiliary transformer 51 and converts it into digital data. Specifically, the signal conversion unit 52 includes an analog filter, a sample-and-hold circuit, a multiplexer, and an A / D (Analog to Digital) converter.

[0030] The analog filter removes high-frequency components from the current waveform signal output from the auxiliary transformer 51. The sample-and-hold circuit samples the current waveform signal output from the analog filter at a predetermined sampling period. The multiplexer sequentially switches the waveform signals input from the sample-and-hold circuit in time series based on the timing signal input from the arithmetic processing unit 70 and inputs them to the A / D converter. The A / D converter converts the waveform signal input from the multiplexer from analog data to digital data. The A / D converter outputs the digitally converted waveform signal (i.e., digital data) to the arithmetic processing unit 70.

[0031] The arithmetic processing unit 70 is mainly composed of a microcomputer and includes a CPU (Central Processing Unit) 72, ROM 73, RAM 74, a digital input circuit 75 (corresponding to the DI (digital input) circuit in the figure), a digital output circuit 76 (corresponding to the DO (Digital output) circuit in the figure), and an input interface (I / F) 77. These are connected by a bus 71.

[0032] The CPU 72 controls the operation of the protective relay 50 by reading and executing a program pre-stored in the ROM 73. The RAM 74, as volatile memory, and the ROM 73, as non-volatile memory, are used as the main memory of the CPU 72. The ROM 73 stores programs and setting values ​​for signal processing.

[0033] The CPU 72 acquires digital data from the signal conversion unit 52 via the bus 71. The CPU 72 performs relay calculations using the acquired digital data according to the program stored in the ROM 73. Based on the results of each relay calculation, the CPU 72 determines whether or not there is a fault (i.e., detects a fault).

[0034] When the CPU 72 detects a fault, it outputs a signal to the outside via the digital output circuit 76. For example, the digital output circuit 76 outputs a trip signal to a circuit breaker. The CPU 72 receives signals from the outside via the digital input circuit 75. The input interface 77 is typically a set of buttons, etc., and accepts various setting operations from the system operator.

[0035] Furthermore, at least a portion of the protective relay 50 may be configured using circuits such as FPGA (Field Programmable Gate Array) and ASIC (Application Specific Integrated Circuit). Also, at least a portion of the protective relay 50 may be configured using analog circuits.

[0036] <Functional Configuration> Figure 3 is a block diagram showing an example of the functional configuration of a protective relay. Referring to Figure 3, the protective relay 50 includes a voltage input unit 310, a monitoring unit 320, a setting unit 330, and a normal processing unit 360. Each of these functions is typically realized by the CPU 72 of the arithmetic processing unit 70 executing a program stored in the ROM 73. The protective relay 50 also further includes a non-volatile storage unit 340 and a volatile storage unit 350. The non-volatile storage unit 340 is realized by, for example, the ROM 73, flash memory, etc. The volatile storage unit 350 is realized by, for example, the RAM 74, etc. Some or all of these functions may be configured to be realized by using dedicated circuits.

[0037] The voltage input unit 310 receives the voltage input from the distribution line 30 within the microgrid 100. Specifically, when the microgrid 100 is in a first state (i.e., connected state) connected to the upstream system 200, the voltage input unit 310 receives the voltage input from the upstream system 200 via the distribution line 30. Typically, since the voltage supplied from the upstream system 200 is the rated voltage, the voltage input unit 310 receives the voltage input of the rated voltage value.

[0038] On the other hand, when the microgrid 100 is in a second state (i.e., disconnected state) that is disconnected from the higher-level system 200, the voltage input unit 310 receives a voltage input from the main power supply unit 60 included in the microgrid 100 via the distribution line 30. As described above, the main power supply unit 60 supplies voltage to the distribution line 30 in a different manner than the higher-level system 200.

[0039] The monitoring unit 320 monitors the input voltage input to the voltage input unit 310 and determines whether the microgrid 100 is connected or disconnected based on the monitoring results. Specifically, the monitoring unit 320 determines whether the input voltage is supplied from the upstream system 200 or the main power supply unit 60 based on the voltage change of the input voltage. The monitoring unit 320 determines that the microgrid 100 is connected if the input voltage is supplied from the upstream system 200, and determines that the microgrid 100 is disconnected if the input voltage is supplied from the main power supply unit 60. The method by which the monitoring unit 320 determines the state of the microgrid 100 will be described in detail below.

[0040] The determination method X1 will now be explained. Here, we assume that the voltage within the microgrid 100 rises with a soft start. Specifically, when the upstream system 200 experiences a power outage and the operator of the power system 1000 switches from normal operation mode to microgrid operation mode, the main power supply unit 60 gradually increases the voltage value supplied to the distribution line 30 to a target value (for example, the rated voltage value) according to the operator's instructions. As a result, the system voltage within the microgrid 100 (i.e., the voltage of the distribution line 30) gradually rises from the power outage state to the rated voltage.

[0041] Therefore, in microgrid operation mode, the voltage supplied to the protective relay 50 (i.e., the voltage of the distribution line 30) gradually increases, and when this voltage reaches the starting voltage, the protective relay 50 starts up. More specifically, the CPU 72 of the arithmetic processing unit 70 included in the protective relay 50 starts up. However, the starting voltage value is assumed to be less than the rated voltage value. The monitoring unit 320 implemented by the CPU 72 is configured to monitor the input voltage at the time of startup (i.e., the input voltage input to the voltage input unit 310), and determines whether the input voltage is less than the voltage threshold Vs. For example, the voltage threshold Vs is set to the rated voltage value.

[0042] If the input voltage at startup is less than the voltage threshold Vs, the monitoring unit 320 determines that the voltage from the main power supply unit 60, which is configured for soft start, is being supplied to the protective relay 50. Therefore, the monitoring unit 320 determines that the microgrid 100 is disconnected.

[0043] On the other hand, if the input voltage at startup is equal to or greater than the voltage threshold Vs, the monitoring unit 320 determines that the voltage from the higher-level system 200 is being supplied to the protective relay 50. This is because the voltage from the higher-level system 200 is supplied at the rated voltage value, and therefore the input voltage at startup is also equal to the rated voltage value (i.e., equal to or greater than the voltage threshold Vs). Therefore, the monitoring unit 320 determines that the microgrid 100 is connected.

[0044] The determination method X2 will now be explained. Similar to the determination method X1, when the power operation is switched from normal operation mode to microgrid operation mode, the main power supply unit 60 is configured to gradually increase the voltage value supplied to the distribution line 30 to the target value.

[0045] Therefore, in microgrid operation mode, the voltage supplied to the protective relay 50 gradually increases to the target value. When the voltage supplied to the protective relay 50 reaches the starting voltage, the protective relay 50 (for example, the CPU 72) starts up. The monitoring unit 320 implemented in the CPU 72 is configured to monitor the rate of change of the input voltage input to the voltage input unit 310, and determines whether the rate of change is less than or equal to the threshold Rs. For example, if the voltage increases to 110V in 5 seconds due to soft start, it increases by 22V per second, so the rate of change is 22 [V / sec]. In this case, the threshold Rs is set to, for example, 22 [V / sec]. However, the threshold Rs may be a value with a margin added to 22 [V / sec] (for example, 23 [V / sec]).

[0046] If the rate of change is less than or equal to the threshold Rs, the monitoring unit 320 determines that the voltage from the main power supply unit 60 is being supplied to the protective relay 50. This is because the input voltage is increasing gradually. Therefore, the monitoring unit 320 determines that the microgrid 100 is disconnected.

[0047] On the other hand, if the rate of change is greater than the threshold Rs, the monitoring unit 320 determines that voltage from the upstream system 200 is being supplied to the protective relay 50. This is because the voltage from the upstream system 200 is supplied at the rated voltage value, so the rate of change of the input voltage is steep (i.e., greater than the threshold Rs). Therefore, the monitoring unit 320 determines that the microgrid 100 is connected.

[0048] The determination methods X1 and X2 described above may be used in combination as appropriate. For example, if at least one of the first condition, that the input voltage at startup is less than the voltage threshold Vs, and the second condition, that the rate of change of the input voltage is less than or equal to the threshold Rs, is met, the monitoring unit 320 may determine that the voltage from the main power supply 60 is being supplied to the protective relay 50 and that the microgrid 100 is in a disconnected state.

[0049] The determination method X3 will now be explained. Here, we assume that when there is a power outage in the upstream system 200, the voltage in the microgrid 100 rises to the rated voltage value instead of a soft start. Specifically, the main power supply unit 60 is configured to supply a specified voltage (for example, the rated voltage) to the distribution line 30 after repeatedly supplying and stopping voltage to the distribution line 30 a certain number of times.

[0050] In this case, during microgrid operation mode, the voltage supplied to the protective relay 50 repeatedly fluctuates between the rated voltage and zero voltage before converging to the rated voltage. For example, consider the following scenario:

[0051] First, when the upstream system 200 experiences a power outage and the main power supply unit 60 begins supplying voltage for the first time (i.e., applying the rated voltage), the CPU 72 (for example, the monitoring unit 320) starts up. When the monitoring unit 320 detects the input voltage rising sharply to the rated voltage (i.e., detects the rising edge of the input voltage), it counts the number of rising edges (i.e., 1). Next, the main power supply unit 60 stops supplying voltage for the first time (i.e., applying the rated voltage). Then, when the main power supply unit 60 begins supplying voltage for the second time, the activated monitoring unit 320 detects the rising edge of the input voltage and counts the number of rising edges (i.e., 2). The main power supply unit 60 continues to supply voltage at the rated voltage. If the input voltage does not become zero voltage even after a certain period of time has elapsed since the input voltage reached the rated voltage, the monitoring unit 320 determines the number of rising edges. In this case, the number of rising edges is 2.

[0052] If the number of rising edge cycles is greater than or equal to a specified number (for example, 2 cycles), the monitoring unit 320 determines that voltage from the main power supply unit 60 is being supplied to the protective relay 50. Therefore, the monitoring unit 320 determines that the microgrid 100 is disconnected.

[0053] On the other hand, if the number of rising edge cycles is less than the specified number, the monitoring unit 320 determines that voltage from the upstream system 200 is being supplied to the protective relay 50. This is because, in the case of voltage from the upstream system 200, the number of rising edge cycles exceeding the specified number is not observed. Therefore, the monitoring unit 320 determines that the microgrid 100 is connected.

[0054] In addition, in the normal operating mode when voltage from the higher-level system 200 is supplied to the protective relay 50, a power restoration method requiring two power outages (for example, a timed sequential method) may be adopted. In this case, it is preferable to set the specified number to three or more in order to clearly distinguish between the number of rising edges in the normal operating mode and the number of rising edges in the microgrid operating mode.

[0055] The setting unit 330 sets the setting value of the protective relay 50 based on the judgment result of the monitoring unit 320. Typically, this setting value is the set value of the protective relay 50. If the control device is a device other than the protective relay 50, the setting value set by the setting unit 330 may be a setting value appropriate for that device.

[0056] In one scenario, if the monitoring unit 320 determines that the microgrid 100 is connected, the setting unit 330 sets the protective relay 50 to the setting value Pu used in normal operation mode. In another scenario, if the monitoring unit 320 determines that the microgrid 100 is disconnected, the setting unit 330 sets the protective relay 50 to the setting value Pm used in microgrid operation mode.

[0057] The non-volatile memory unit 340 stores the setting value Pu and the setting value Pm. When the microgrid 100 is connected, the setting unit 330 sets the setting value Pu on the protective relay 50 by writing the setting value Pu obtained from the non-volatile memory unit 340 to the operating area of ​​the volatile memory unit 350. This operating area is for storing the setting values ​​actually used by the protective relay 50. When the microgrid 100 is disconnected, the setting unit 330 sets the setting value Pm on the protective relay 50 by writing the setting value Pm obtained from the non-volatile memory unit 340 to the operating area of ​​the volatile memory unit 350.

[0058] When the setting value is a current value, typically, the larger the power from the power source, the larger the setting value. Specifically, in normal operation mode, the power supplied from the upstream system 200 is greater than the power supplied from the main power supply unit 60 in microgrid operation mode. Therefore, the fault current that occurs in normal operation mode is greater than the fault current that occurs in microgrid operation mode. Consequently, the setting value Pu will be greater than the setting value Pm. Assume that the protective relay 50 performs ground fault direction relay calculation. In this case, the setting value Pu used in normal operation mode is, for example, 200mA. On the other hand, the setting value Pm used in microgrid operation mode is, for example, 150mA.

[0059] The normal processing unit 360 refers to the set value stored in the operating area of ​​the volatile memory unit 350 and uses the set value to perform normal processing to protect the protected object. Specifically, the normal processing unit 360 performs various protective relay calculations using the amount of electricity input from the instrument transformer and the set value. If the normal processing unit 360 determines, based on the results of the protective relay calculation, that an accident such as a short circuit or ground fault has occurred in the protected object, it outputs an open command to the circuit breaker installed in the customer equipment 110 and opens the circuit breaker.

[0060] (modified version) In the modified example, determination method X4, which is a modified method of determining the state of the microgrid 100 by the monitoring unit 320, will be described. Here, when the power operation is switched from normal operation mode to microgrid operation mode, the main power supply unit 60 is configured to supply a voltage with the fundamental wave component and harmonic components superimposed to the distribution line 30.

[0061] Figure 4 is a block diagram showing a modified example of the functional configuration of a protective relay. Referring to Figure 4, the functional configuration of protective relay 50A is the same as that of protective relay 50 shown in Figure 3, but with the addition of a filter unit 370 and the replacement of the monitoring unit 320 in Figure 3 with a monitoring unit 320A. Detailed explanations of functions identical to those described in Figure 3 will not be repeated.

[0062] The filter unit 370 extracts the fundamental wave component and harmonic components contained in the input voltage input to the voltage input unit 310. The monitoring unit 320A monitors the fundamental wave component and harmonic components contained in the input voltage and determines whether the ratio of the harmonic component to the fundamental wave component is greater than or equal to the threshold K. The threshold K is, for example, 5% to 10%.

[0063] If the ratio is greater than or equal to the threshold K, the monitoring unit 320 determines that voltage from the main power supply unit 60 is being supplied to the protective relay 50. In this case, the monitoring unit 320 determines that the microgrid 100 is disconnected.

[0064] On the other hand, if the ratio is less than the threshold K, the monitoring unit 320 determines that voltage from the upstream system 200 is being supplied to the protective relay 50. This is because, generally, the ratio of harmonic components to fundamental components in the voltage from the upstream system 200 is small (for example, less than the threshold K). In this case, the monitoring unit 320 determines that the microgrid 100 is connected.

[0065] In the main power supply unit 60, the harmonic components superimposed on the fundamental wave component only need to be second-order or higher harmonics. However, when determining the presence or absence of inrush current, the ratio of the second-order harmonic component to the fundamental wave component is used. This is because inrush current contains a large amount of second-order harmonic components. Therefore, in order to distinguish this from the determination of the presence or absence of inrush current, the harmonic components superimposed on the fundamental wave component in the voltage from the main power supply unit 60 may be third-order or higher harmonics.

[0066] <Processing Procedure> Figure 5 is a flowchart showing an example of the processing procedure of a protective relay. Typically, each of the following steps is performed by the calculation processing unit 70 of the protective relay 50.

[0067] Referring to Figure 5, the protective relay 50 receives the voltage input from the distribution line 30 (step S10). The protective relay 50 monitors the input voltage (step S12). Based on the monitoring results, the protective relay 50 determines whether or not the microgrid 100 is disconnected (step S14). Specifically, the protective relay 50 performs this determination using one of the determination methods X1 to X4 described above.

[0068] If the microgrid 100 is disconnected (YES in step S14), the protective relay 50 obtains the setting group number corresponding to the microgrid operating mode (step S16). On the other hand, if the microgrid 100 is not disconnected (i.e., connected) (NO in step S14), the protective relay 50 obtains the setting group number corresponding to the normal operating mode (step S18). For example, in steps S16 and S18, the CPU 72 reads the setting group number stored in the non-volatile memory (e.g., ROM 73).

[0069] The protective relay 50 obtains a setting value corresponding to the setting group number obtained in step S16 or step S18 (step S20). For example, the CPU 72 reads the setting value stored in the non-volatile memory (e.g., ROM 73) by referring to the setting group number. The protective relay 50 stores the obtained setting value in the operating area (step S22). For example, the CPU 72 writes the setting value to the operating area of ​​the volatile memory (e.g., RAM 74).

[0070] The protective relay 50 performs normal processing using the setting value written in the operating area (step S24). Specifically, the protective relay 50 performs various protective relay calculations to protect the protected object based on the amount of electricity input from the instrument transformer and the setting value. Furthermore, if the protective relay 50 determines that a fault has occurred in the protected object based on the result of the protective relay calculation, it outputs an open command to the circuit breaker.

[0071] <Advantages> According to this embodiment, appropriate settings can be set in the control equipment (e.g., protective relay 50) depending on whether or not there is a connection between the higher-level system and the microgrid, without the need to construct a new communication environment in the existing equipment. By utilizing existing equipment in this way, cost reduction can also be achieved. In particular, the protective relay 50 is a device that protects various equipment from system faults, and it is necessary to set appropriate settings from the time of startup. Therefore, it is useful to be able to appropriately determine whether or not there is a connection between the higher-level system and the microgrid during startup processing. In addition, since workers do not need to go to the installation location of each protective relay to perform various settings, the burden on workers can be reduced.

[0072] Other embodiments. The configuration described above as an example of the embodiment is just one example of the configuration of this embodiment, and it is possible to combine it with other known technologies, and to modify it by omitting parts of it, etc., without departing from the gist of this disclosure.

[0073] <Note> The various aspects of this disclosure are summarized below as an appendix.

[0074] (Note 1) A control device included in a microgrid, comprising a voltage input unit that receives the voltage input of a distribution line within the microgrid, wherein the voltage input unit receives the voltage input from the upper system via the distribution line when the microgrid is in a first state connected to an upper system, and receives the voltage input from a main power supply unit included in the microgrid via the distribution line when the microgrid is in a second state disconnected from the upper system, monitors the input voltage input to the voltage input unit, and determines whether the microgrid is in the first or second state based on the result of the monitoring, and further comprises a setting unit that sets a set value for the control device based on the determination result of the monitoring unit.

[0075] (Note 2) The control device as described in Appendix 1, wherein the monitoring unit determines, based on the voltage change of the input voltage, whether the input voltage is supplied from the upstream system or the main power supply unit, and determines that the microgrid is in the first state if the input voltage is supplied from the upstream system, and determines that the microgrid is in the second state if the input voltage is supplied from the main power supply unit.

[0076] (Note 3) The control device as described in Appendix 1 or Appendix 2, wherein the main power supply unit is configured to gradually increase the voltage value of the voltage supplied to the distribution line to a target value, and the monitoring unit monitors the input voltage at startup of the control device, and determines that the microgrid is in the second state if the input voltage at startup is less than a voltage threshold.

[0077] (Note 4) The control device as described in Appendix 3, wherein the monitoring unit monitors the rate of change of the input voltage, and determines that the microgrid is in the second state if the rate of change is less than or equal to a first threshold.

[0078] (Note 5) The control device described in Appendix 1 or Appendix 2, wherein the main power supply unit is configured to supply a specified voltage to the distribution line after repeatedly supplying and stopping voltage to the distribution line a certain number of times, and the monitoring unit monitors the rising edge of the input voltage, and determines that the microgrid is in the second state if the number of rising edges is equal to or greater than a specified number.

[0079] (Note 6) The control device described in Appendix 1 or Appendix 2, wherein the main power supply unit supplies a voltage with a fundamental wave component and a harmonic component superimposed to the distribution line, and the monitoring unit monitors the fundamental wave component and the harmonic component included in the input voltage, and determines that the microgrid is in the second state if the ratio of the harmonic component to the fundamental wave component is greater than or equal to a second threshold.

[0080] (Note 7) The aforementioned control device is a protective relay, and is a control device as described in any of the appendices 1 to 6.

[0081] (Note 8) The aforementioned setting value is the setting value of the protective relay, as described in Appendix 7 of the control equipment.

[0082] (Note 9) A power system comprising a control device and a main power supply unit included in a microgrid, wherein the control device includes a voltage input unit that receives voltage input from a distribution line within the microgrid, the voltage input unit receiving voltage input from the upper system via the distribution line when the microgrid is in a first state connected to an upper system, and receiving voltage input from the main power supply unit via the distribution line when the microgrid is in a second state disconnected from the upper system, the control device further includes a monitoring unit that monitors the input voltage input to the voltage input unit and determines whether the microgrid is in the first or second state based on the result of said monitoring, and a setting unit that sets a set value for the control device based on the determination result of the monitoring unit.

[0083] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of this disclosure is indicated by the claims rather than by the foregoing description, and all modifications within the meaning and scope equivalent to the claims are intended. [Explanation of symbols]

[0084] 21,22 Switches, 30 Distribution lines, 40 Loads, 50,50A Protective relays, 51 Auxiliary transformers, 52 Signal conversion unit, 60 Main power supply unit, 70 Arithmetic processing unit, 71 Bus, 73 ROM, 74 RAM, 75 Digital input circuit, 76 Digital output circuit, 77 Input interface, 100 Microgrid, 110 Consumer equipment, 120 Small-scale power plant, 200 Higher-level system, 310 Voltage input unit, 320,320A Monitoring unit, 330 Setting unit, 340 Non-volatile memory unit, 350 Volatile memory unit, 360 Normal processing unit, 370 Filter unit, 1000 Power system.

Claims

1. Control equipment included in a microgrid, The microgrid includes a voltage input unit that receives the voltage input of the distribution lines within the microgrid, The aforementioned voltage input section is When the microgrid is in a first state, connected to a higher-level system, it receives voltage input from the higher-level system via the distribution line. When the microgrid is in a second state, disconnected from the higher-level system, it receives voltage input from the main power supply unit included in the microgrid via the distribution line. A monitoring unit monitors the input voltage input to the voltage input unit and determines whether the microgrid is in the first state or the second state based on the results of the monitoring, A control device further comprising a setting unit that sets the set value of the control device based on the judgment result of the monitoring unit.

2. The aforementioned monitoring unit, Based on the voltage change of the input voltage, it is determined whether the input voltage is supplied from the upstream system or the main power supply unit. The control device according to claim 1, wherein the microgrid is determined to be in the first state if the input voltage is a voltage supplied from the upstream system, and the microgrid is determined to be in the second state if the input voltage is a voltage supplied from the main power supply unit.

3. The main power supply unit is configured to gradually increase the voltage value of the voltage supplied to the distribution line up to a target value. The aforementioned monitoring unit, The input voltage is monitored when the control device is started up. The control device according to claim 1 or 2, wherein the microgrid is determined to be in the second state if the input voltage at startup is less than a voltage threshold.

4. The aforementioned monitoring unit, The rate of change of the input voltage is monitored, The control device according to claim 3, wherein if the rate of change is less than or equal to a first threshold, it is determined that the microgrid is in the second state.

5. The main power supply unit is configured to supply a specified voltage to the distribution line after repeatedly supplying and stopping voltage to the distribution line a certain number of times. The aforementioned monitoring unit, The rising edge of the aforementioned input voltage is monitored, The control device according to claim 1 or 2, wherein if the number of rising edges is greater than or equal to a specified number, the microgrid is determined to be in the second state.

6. The main power supply unit supplies a voltage to the distribution line that has the fundamental wave component and the harmonic component superimposed on it. The aforementioned monitoring unit, The fundamental wave component and the harmonic component included in the input voltage are monitored. The control device according to claim 1 or 2, wherein the microgrid is determined to be in the second state if the ratio of the harmonic component to the fundamental component is greater than or equal to a second threshold.

7. The control device is a protective relay, as described in claim 1 or claim 2.

8. The control device according to claim 7, wherein the set value is the setting value of the protective relay.

9. The microgrid includes control equipment and a main power supply, The control device includes a voltage input section that receives the voltage input of the distribution lines within the microgrid. The aforementioned voltage input section is When the microgrid is in a first state, connected to a higher-level system, it receives voltage input from the higher-level system via the distribution line. When the microgrid is in a second state, disconnected from the higher-level system, it receives a voltage input from the main power supply via the distribution line. The aforementioned control device is A monitoring unit monitors the input voltage input to the voltage input unit and determines whether the microgrid is in the first state or the second state based on the results of the monitoring, A power system further comprising a setting unit that sets the set values ​​of the control equipment based on the judgment results of the monitoring unit.

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