Power system stabilization system and power system stabilization method

Abstract

To make it possible to determine an effective control method according to the state of a power system in which power conversion devices having a plurality of control methods that contribute to system stabilization are interconnected.SOLUTION: A power system stabilization system includes: a system state estimation unit 21 that estimates the system state of a power system using system configuration data and system measurement data of the power system; a system stability calculation unit 22 that calculates the system stability of the power system using event cases; a system stability evaluation unit 23 that evaluates the system stability on the basis of a calculation result of the system stability calculation unit 22; a control mode setting unit 24 that sets a control mode of an inverter power supply connected to the power system on the basis of a result of the evaluation of the system stability by the system stability evaluation unit 23; and a control mode transmission unit 25 that transmits the control mode set by the control mode setting unit to the inverter power supply.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a power system stabilization system and a power system stabilization method. [Background technology]

[0002] With regard to power systems, it has been proposed to connect a power system stabilization device and use system information before an event such as a predicted failure to calculate in advance (pre-calculation) the control target (power generation side or load side), and then perform control based on the event information and the pre-calculation results when the event occurs.

[0003] Patent Document 1 proposes a power system stabilization system that controls power by giving priority to renewable energy power sources (inverter power sources) over synchronous machines. That is, Patent Document 1 describes a power system stabilization device that detects the occurrence of an accident in a power system that has introduced renewable energy power generation devices in addition to multiple generators, and prevents the generators from losing synchronization when an accident occurs. Patent Document 1 describes a technology that prevents the generators from losing synchronization by shutting down the renewable energy power generation devices. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6223833 Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, in recent years, with the spread of inverter power supplies, in order to cope with a decrease in system stability when connecting the inverter power supply to a system, it has been considered to provide the inverter power supply with a power supply stabilizer. For example, a smart inverter is one type of inverter power supply with power supply stabilization. This smart inverter is equipped with a communication function and multiple control modes that have a system stabilization effect, such as frequency-watt control and volt-variable control. Details of these control modes will be explained in the embodiment examples below.

[0006] There is also an inverter power supply called a grid-forming inverter, which contributes to grid stabilization by operating as a voltage source.Grid-forming inverters have multiple control modes, such as VSG (Virtual Synchronous Generator) control, droop control, and virtual oscillator control.

[0007] In contrast to these smart inverters and grid-forming inverters, conventional inverter power supplies are called grid-following inverters. This grid-following inverter outputs active and reactive power by synchronizing with the voltage and current phase of the grid, and therefore has a low ability to support the grid during grid disturbances.The smart inverter mentioned above is defined as a grid-following inverter.

[0008] On the other hand, grid-forming inverters can output power independently of the voltage and current phases of the grid, and can support the grid with characteristics that are the same as or similar to those of conventional synchronous generators even during grid disturbances.

[0009] Changing the control mode of these inverter power supplies contributes to stabilizing the connected power supply system, but as described in Patent Document 1, control to change the control mode of the inverter power supply has not been performed in the past when controlling events such as failures. That is, the control assumed in the past using smart inverters is to stabilize the system by changing the control mode of the inverter connected to the power generation device when the amount of power generated by renewable energy such as solar power generation fluctuates significantly. Therefore, inverter power supplies such as smart inverters have not been used to respond to power system failures, and it cannot be said that sufficient stabilization processing is performed in the event of a system failure.

[0010] In view of the above, an object of the present invention is to provide a power system stabilization system and a power system stabilization method that can determine an effective control method depending on the state of a power system in which power conversion devices having multiple control methods that contribute to system stabilization are interconnected. [Means for solving the problem]

[0011] In order to solve the above problems, for example, the configurations described in the claims are adopted. The present application includes a plurality of means for solving the above-mentioned problems. One example is a power system stabilization device for stabilizing a predetermined power system, the device comprising: a system state estimation unit that estimates a system state of the power system using system configuration data and system measurement data of the power system; a system stability calculation unit that calculates the system stability of the power system using event cases; a system stability evaluation unit that evaluates the system stability based on a calculation result of the system stability calculation unit; a control mode setting unit that sets a control mode of an inverter power supply connected to the power system based on the evaluation result of the system stability by the system stability evaluation unit; and a control mode transmission unit that transmits the control mode set by the control mode setting unit to the inverter power supply. [Effects of the Invention]

[0012] According to the present invention, an effective control mode of the inverter power supply can be set, thereby stabilizing the power system. Problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a configuration diagram showing an example of a power system stabilization system according to a first embodiment of the present invention. [Figure 2] 1 is a configuration diagram showing an example of a power system stabilization device according to a first embodiment of the present invention. [Figure 3] FIG. 2 is a configuration diagram showing an example of a configuration database according to the first embodiment of the present invention. [Figure 4] FIG. 2 is a configuration diagram showing an example of a system measurement database according to the first embodiment of the present invention. [Figure 5] FIG. 2 is a configuration diagram showing an example of an event case database according to the first embodiment of the present invention. [Figure 6] FIG. 2 is a configuration diagram showing an example of an inverter power supply equipment information database according to the first embodiment of the present invention. [Figure 7] FIG. 2 is a configuration diagram showing an example of a system state estimation result database according to the first embodiment of the present invention. [Figure 8] FIG. 2 is a configuration diagram showing an example of a system stability calculation result database according to the first embodiment of the present invention. [Figure 9] FIG. 3 is a configuration diagram showing an example of a control mode setting result database according to the first embodiment of the present invention. [Figure 10] 5 is a flowchart showing an example of processing by a control mode determination unit of the power system stabilization system according to the first embodiment of the present invention. [Figure 11] 5 is a flowchart showing an example of processing by a control mode setting unit according to the first embodiment of the present invention. [Figure 12] FIG. 3 is a diagram illustrating an example of a control mode setting method in a control mode determination unit according to the first embodiment of the present invention. [Figure 13] FIG. 3 is a diagram showing an example of control mode settings of an inverter power supply of the power system stabilizer according to the first embodiment of the present invention. [Figure 14] FIG. 2 is a diagram showing a display example of a display unit according to the first embodiment of the present invention. [Figure 15] FIG. 10 is a configuration diagram showing an example of a power system stabilization system according to a second embodiment of the present invention. [Figure 16] FIG. 4 is a configuration diagram showing an example of a power system stabilization device according to a second embodiment of the present invention. [Figure 17] FIG. 10 is a diagram showing an example of a controllable power supply database according to the second embodiment of the present invention. [Figure 18] FIG. 10 is a diagram showing an example of a system fault database according to a second embodiment of the present invention. [Figure 19] 10 is a flowchart showing an example of processing by a system stabilization calculation unit according to the second embodiment of the present invention. [Figure 20] 10 is a flowchart showing an example of processing by a control decision unit according to the second embodiment of the present invention. [Figure 21] FIG. 4 is a configuration diagram showing another example of a power system stabilization device according to the second embodiment of the present invention. [Figure 22] FIG. 22 is a diagram showing an example of output from the example of FIG. 21. DETAILED DESCRIPTION OF THE INVENTION

[0014] <First embodiment> A power system stabilization system and a power system stabilization method according to a first embodiment of the present invention will be described below with reference to FIGS.

[0015] [Configuration of power system stabilization system] FIG. 1 illustrates the overall configuration of a power system stabilization device 10 when a power system stabilization system according to a first embodiment of the present invention is applied to a power system. The upper part of FIG. 1 shows the hardware configuration of the power system stabilization device 10. The power system stabilizing device 10 includes an input unit 101 , a display unit 102 , a communication unit 103 , a processor 104 , a memory 105 , a program database DB 9 , and a bus 107 . The program database DB9 stores a program for operating a computer as the power system stabilizer 10. These components and databases DB1 to DB8, which will be described next, are connected via a bus 107. A communication unit 103 communicates with measuring instruments and control terminals of the power system 1 via a communication network .

[0016] Furthermore, the following databases DB1 to DB8 are connected to the bus 107. These databases DB1 to DB8 are also configured by executing programs stored in the program database DB9. That is, the power system stabilizing device 10 includes a system configuration database DB1, a system measurement database DB2, an event case database DB3, an inverter power supply equipment information database DB4, a system state estimation result database DB5, a system stability calculation result database DB6, a system stability evaluation result database DB7, and a control mode setting result database DB8.

[0017] The input unit 101 is an input device such as a keyboard or a mouse that is operated by an operator, and inputs information to the system via a USB (Universal Serial Bus). The display unit 102 is configured, for example, by a monitor, and displays input / output data of the system as an image. Note that the display unit 102 may also be configured to output sounds, vibrations, etc., to output voice, alarm sounds, or vibrations linked to alarm on.

[0018] The communication unit 103 communicates with other devices in the power system 1 via a communication network 106 . The processor 104 executes a calculation program obtained from the program database DB9 to specify image data to be displayed, search for data in various databases, etc. The processor 104 may be configured as one or more semiconductor chips, or may be configured as a computer device such as a calculation server.

[0019] The memory 105 is configured by incorporating, for example, a RAM (Random Access Memory) and a ROM (Read Only Memory). For example, the ROM stores computer programs, and the RAM temporarily stores calculation result data, image data, processing programs, etc., required for each process. The communication network 106 is, for example, a wide area Ethernet or a public line, and is responsible for communication between the system and devices in the power system 1. The bus 107 connects the various elements of the power system stabilizer 10. Data transfer between the various elements is carried out through the bus 107.

[0020] Next, the databases DB1 to DB8 included in the power system stabilizing device 10 will be described. The system configuration database DB1 stores the connection configuration of the power system, the generator model, the load model, the load position, the generator position, the parameters of the power transmission route (power transmission line and transformer), the bus position, the breaker position, etc. The system model as the system configuration utilizes either a bus branch model that simply represents the connection configuration of the equipment, or a node breaker model that represents the physical connection configuration of the equipment. The system configuration also includes the system connection configuration generated from breaker information obtained from measurement information. Generally, if it is estimated by a topology processor, in this embodiment, it is considered to have been preprocessed via the communication unit.

[0021] The system measurement database DB2 stores measurement information of the power system 1. The event case database DB3 stores information about events that may occur in the power system 1. The inverter power supply equipment information database DB4 stores information on the inverter power supply equipment. The system state estimation result database DB5 stores measurement information and the state of the power system estimated from the system configuration data. The system stability calculation result database DB6 stores the calculation results of the system stability using the system estimation results created by the system state estimation unit 21 (FIG. 2) and the event cases stored in the event case database DB3.

[0022] The system stability evaluation result database DB7 stores the results of the system stability evaluation. The control mode setting result database DB8 stores the control mode setting results of each inverter power supply. The program database DB9 stores various execution programs for the power system stabilization device 10. These programs include numerical simulation programs required for evaluating system stability. Specifically, the programs include a power flow calculation program, a transient stability calculation program, a frequency stability calculation program, and a voltage stability calculation program.

[0023] [Power system configuration] Next, the power system 1 shown in the lower part of FIG. 1 will be described. The power system 1 to which the power system stabilization device 10 of this embodiment is applied means a power transmission system 1A in the narrow sense, and is shown as a concept including a power generation system in the broad sense. As shown in the lower part of Figure 1, the power system 1 is composed of a generator 2, buses 3 (3A, 3B, 3C, 3D), transformers 4 (4A, 4B), transmission lines 5 (5A, 5B), renewable energy sources 6, and loads 7.

[0024] The configuration of the power system 1 shown in FIG. 1 is one example, and in addition to the elements shown in FIG. 1, the power system may be configured to include one or more of a phase modifying device, a battery, a rechargeable secondary battery, a storage battery for an electric vehicle, a flywheel, a phase modifying device, or other power storage device.

[0025] These facilities and devices that make up the power system 1 are monitored and controlled from the perspective of ensuring the stability of the power system 1, and control and protection are performed as appropriate, for example, by control signals from a monitoring and control device 200 connected to a communication network 106. On the other hand, for such monitoring and control, measurement data such as current, voltage, and other status signals at various locations are taken into the monitoring and control device 200 directly or indirectly via the communication network 106 from various measuring devices (not shown) installed at various locations in the power system.

[0026] Similarly, the power system stabilization device 10 also receives measurement signals from measurement devices in various parts of the power system 1. Here, the generators 2 include large power sources such as thermal power generators, hydroelectric power generators, and nuclear power generators. Furthermore, the renewable energy power sources 6 include distributed power sources such as solar power generation and wind power generation. The renewable energy power supply 6 includes an inverter power supply, and generates power to be output to the power grid 1. The inverter power supply included in the renewable energy power supply 6 here may be a smart inverter, a grid-forming inverter, or the like. This inverter power supply is equipped with a communication function and multiple control modes such as frequency-watt control and volt-variable control. Examples of the multiple control modes will be described later with reference to FIG.

[0027] The measuring devices that measure the power system 1 are devices that measure one or more of the node voltage V, branch current I, power factor Φ, active power P, reactive power Q, and fault mode. Specifically, these devices include voltage transformers (VT, PT), current transformers (CT), bus protection relays (BP), line protection relays (LP), and transformer protection relays (TP).

[0028] These measuring devices have a function as a telemeter (TM) that transmits data including a data measurement location identification ID and a built-in timestamp of the measuring device. The measurement device may also be a device that measures power information (voltage phasor information) with absolute time using the Global Positioning System (GPS), a phase measurement device (PMU: Phasor Measurement Units), or other measurement equipment. Furthermore, although the measuring device is described as being within the narrowly defined power system 1A, it may also be installed on a bus 3 or line (transmission line) 5 that connects the generator 2, transformer 4, measuring device 150, and load 7.

[0029] The measurement data is data measured by a measurement device (system measurement data), which is received by the power system stabilization device 10 via the communication network 106 and stored in the system measurement database DB2. However, instead of receiving the system data directly from the measuring devices, the measurement data may be once collected in the monitoring and control device 200 and then stored in the system measurement database DB2 via the communication network 106. Alternatively, the power system stabilization device 10 may receive the measurement data from both the measuring devices and the monitoring and control device 200 via the communication network 106 and store it in the system measurement database DB2. The system measurement data may include a unique number for identifying the data and a time stamp. Past system measurement data may be stored in advance in the system measurement database DB2.

[0030] [Processing configuration of power system stabilization device] FIG. 2 is a configuration diagram showing the processing performed by the power system stabilizing device 10. As shown in FIG. As described above, the power system stabilizing device 10 is made up of a system configuration database DB1, a system measurement database DB2, an event case database DB3, an inverter power supply equipment information database DB4, a system state estimation result database DB5, a system stability calculation result database DB6, a system stability evaluation result database DB7, a control mode setting result database DB8, and a control mode determination unit 20.

[0031] The control mode determination unit 20 includes a system state estimation unit 21 , a system stability calculation unit 22 , a system stability evaluation unit 23 , a control mode setting unit 24 , and a control mode transmission unit 25 . The system state estimation unit 21 performs a system state estimation process to estimate the system state using the system configuration information stored in the system configuration database DB1 and the system measurement information stored in the system measurement database DB2. The system state estimation unit 21 then transmits the estimated system state to the system stability calculation unit 22 and stores it in the system state estimation result database DB5. The system stability calculation unit 22 performs a system stability calculation process to calculate the system stability in the target system cross section using the system state estimation result from the system state estimation unit 21 and the event information stored in the event case database DB3. Then, the system stability calculation unit 22 transmits the system stability obtained by the system stability calculation process to the system stability evaluation unit 23, and also stores it in the system stability evaluation result database DB7.

[0032] The system stability evaluation unit 23 performs a system stability evaluation process to evaluate system stability using the system stability calculation result of the system stability calculation unit 22. Then, the system stability evaluation unit 23 transmits the system stability calculation result to the control mode setting unit 24 and stores it in the system stability evaluation result database DB7. The control mode setting unit 24 performs a control mode setting process to set the control mode of each inverter power supply using the equipment information of the inverter power supply stored in the inverter power supply equipment information database DB4 and the system stability evaluation result of the system stability evaluation unit 23. Then, the control mode setting unit 24 transmits the control mode setting result to the control mode transmission unit 25 and stores it in the control mode setting result database DB8. Control mode transmission unit 25 transmits the control mode setting result of control mode setting unit 24 to each inverter power supply via communication network 106 (FIG. 1). Here, the inverter power supply of the transmission destination is provided in renewable energy power supply 6 (FIG. 1).

[0033] [Database (DB1~DB8) description] Here, the databases DB1 to DB8 held by the power system stabilizing device 10 will be explained. The system configuration database DB1 stores data that configures the power system 1. FIG. 3 shows an example of the system configuration database DB1 of the power system stabilization device 10. As shown in FIG. The system configuration database DB1 stores information such as the impedance of the transmission lines connecting each bus 3 (for example, bus 3A and bus 3B) in the power system 1. Storing data in this way makes it possible to predict and calculate the route through which power will flow once power generation and consumption have been determined. The system configuration database DB1 also stores the on / off state (SV state) of the transmission lines.

[0034] FIG. 4 shows an example of the system measurement database DB2 of the power system stabilization device 10. As shown in FIG. The system measurement database DB2 stores the measurement time and the measured value as measurement information for the power system. For example, the system measurement database DB2 stores the active power (P) and reactive power (Q) of each transmission line, and the voltage (V) of each bus. The values ​​stored at this time may be in the unit of the direct measurement information (e.g., MW), or may be in the unitized pu value. The example in Figure 4 shows an example where the latter is stored in pu value.

[0035] FIG. 5 shows an example of the event case database DB3 of the power system stabilizing device 10. As shown in FIG. An event case indicates an event such as a failure of a power transmission line, and includes information on the location of the failure (such as the receiving end of power transmission line A) and the nature of the failure. By maintaining such an event case database DB3, it is possible to narrow down the countless events that exist to a reasonable range.

[0036] FIG. 6 shows an example of the inverter power supply equipment information database DB4 of the power system stabilizing device 10. As shown in FIG. The inverter power supply equipment information database DB4 stores the name of the target inverter power supply, rated output, equipment capacity, connection position (connected bus), voltage class, inverter type, and control mode. Examples of inverter types include wind power (GFM) and solar power (GFL), and examples of control modes include VSG control, droop control, virtual oscillator control, Volt-Var control, Volt-Watt control, Frequency-Watt control, dynamic reactive power control, and power factor adjustment. By storing this information in the inverter power supply equipment information database DB4, it becomes possible to evaluate the influence of the inverter when a simulation is executed. The information in the inverter power supply equipment information database DB4 is acquired and stored in advance.

[0037] FIG. 7 shows an example of the system state estimation result database DB5 of the power system stabilization device 10. As shown in FIG. The system state indicates the voltage (V), phase (δ), active power (P), and reactive power (Q) of each element (generator, load, etc.) of the power system, and indicates the state in which each element of the power system is operating. The power system stabilization device 10 performs fault calculations based on these states stored in the system state estimation result database DB5. The power system stabilization device 10 performs fault calculations by utilizing, for example, one or more of state estimation, which estimates the voltage phase of the power system from limited measurement information, and power flow calculation, which calculates power flows (P and Q) from the power input and output to the power system. The power system state may be generated from measurement information or from future prediction information.

[0038] FIG. 8 shows an example of the system state estimation result database DB5 of the power system stabilizing device 10. As shown in FIG. The system state estimation result database DB5 stores time-series data of the voltage, phase angle, active power, and reactive power for each power source as the results of numerical simulations that are system state estimation results. The time-series data here is expressed as, for example, the time when the accident occurred (0.00), the next time (0.01), and so on. The grid state estimation result database DB5 may store time series data of not only power sources but also buses, transmission lines, etc. Also, instead of time series data, maximum values ​​and average values ​​of the time series data may be stored.

[0039] FIG. 9 shows an example of the control mode setting result database DB8 of the power system stabilizing device 10. As shown in FIG. The control mode setting result database DB8 stores the control mode set for each inverter power supply. That is, the control mode setting result database DB8 stores the control mode set for each inverter power supply, such as VSG control or droop control. In addition to the control mode setting, the control mode setting result database DB8 may also store control parameters and the like.

[0040] [Control mode determination processing] FIG. 10 is a flowchart showing the processing performed by the control mode determination unit 20 of the power system stabilizing device 10. First, the system state estimation unit 21 of the control mode determination unit 20 estimates the system state using the system model database DB1, the system configuration database DB1, and the system measurement database DB2 (step S100). The system state estimation results obtained by the system state estimation unit 21 are stored in a system state estimation result database DB8. In the system state estimation calculation, the system state estimation unit 21 estimates the active power P, reactive power Q, voltage V, voltage phase angle δ, current I, and power factor Φ of each node, branch, generator, load, and control device of the system as plausible.

[0041] Next, the control mode determination unit 20 selects an expected event (fault) using the event case database DB3 (step S101). Then, the system stability calculation unit 22 of the control mode determination unit 20 calculates the system stability based on the contingency fault selected in step S101 (step S102). The system stability here refers to transient stability, frequency stability, voltage stability, etc. These system stability calculations are performed, for example, by calling a stability analysis program pre-installed in the power system stabilization device 10.

[0042] The stability evaluation unit 23 of the control mode determination unit 20 evaluates stability by checking for stability violations (step S103). For example, the stability evaluation unit 23 uses the internal operating angle of the synchronous generator as an evaluation index for transient stability, and determines that transient instability exists when the deviation from the internal operating angle of the reference generator exceeds a threshold value. Furthermore, the stability evaluation unit 23 uses the stability margin of a PV curve, in which the vertical axis represents active power and the horizontal axis represents voltage, as an evaluation index for voltage stability, and determines that voltage is unstable when the stability margin exceeds a threshold. These stability evaluations are performed, for example, by calling a stability analysis program pre-installed in the power system stabilization device 10.

[0043] Furthermore, the stability evaluation unit 23 of the control mode determination unit 20 checks whether all contingencies (events) have been selected (step S104). If there are any contingencies (events) that have not been selected in step S104 (NO in step S104), the process returns to step S101.

[0044] If all anticipated faults (events) have been checked in step S104 (YES in step S104), the control mode setting unit 24 of the control mode determination unit 20 sets the control mode of the inverter power supply using the system stability evaluation result in step S103 and the inverter power supply equipment information database DB4 (step S105). Here, the method for setting the control mode of the inverter power supply may be, for example, to create combinations of control modes for each inverter power supply, calculate the effect on system stability for each combination, and set the combination that has the greatest effect of improving system stability as the control mode. Details of the process for setting the control mode will be described later with reference to FIG. 11.

[0045] Thereafter, the control mode transmission unit 25 of the control mode determination unit 20 transmits the control mode set in step S105 to each inverter power supply 6 via the communication network 106 (step S106).

[0046] [Control mode setting processing] FIG. 11 is a flowchart showing the processing performed by the control mode setting unit 24 of the control mode determination unit 20. First, the control mode setting unit 24 reads the equipment information of the inverter power supplies from the inverter power supply equipment information database DB4 and sets the power supplies for which the control mode is to be set (step S200). The target power supplies may be set to all inverter power supplies connected to the grid, or may be limited by voltage class or grid interconnection position. Alternatively, the target power supplies may be grouped and a control mode may be set for each group.

[0047] Then, the control mode setting unit 24 determines a combination (pattern) of the control modes of each inverter power supply (step S201). The control mode combinations may overlap between the inverter power supplies. Furthermore, all possible combinations of the control modes may be created, or the control modes of the inverter power supplies may be limited to create combinations. Once the combination of control modes has been determined, the control mode setting unit 24 acquires the calculation results of the system stability for each combination created in step S201 (step S202). Furthermore, the control mode setting unit 24 acquires an evaluation of the system stability calculation results obtained in step S202 (step S203).

[0048] Then, the control mode setting unit 24 checks whether all the combinations have been selected (step S204). If there are any combinations that have not been selected in step S204 (NO in step S204), the process returns to step S201. Furthermore, if all combinations have been selected in step S204 (YES in step S204), the control mode setting unit 24 sets the control mode of the inverter power supply using the system stability evaluation result of each combination (step S205).

[0049] The combination set by the control mode setting unit 24 as the control mode may be, for example, the combination that provides the greatest improvement in system stability across all event cases, or the combination that provides the greatest improvement in a specific event case. Then, the control mode set in step S205 is transmitted by the control mode transmission unit 25 to the control mode setting result database DB8 and stored therein.

[0050] [Example of control mode setting section operation] Next, an example of a method for setting the control mode of the inverter power supply in the control mode setting unit 24 will be described. The control mode setting unit 24 creates patterns that combine control modes for each power source, and calculates the system stability in the target system cross section for each pattern.The control mode setting unit 24 then performs processing to set the pattern that provides the highest degree of improvement in system stability as the control mode.In other words, the control mode setting unit 24 performs processing to select an effective control mode for the inverter power source. 12 shows an example of a control mode setting method of the control mode determination unit 20 in this embodiment. The upper, middle, and lower drawings show a series of examples up to the setting of the control mode.

[0051] The upper part of Fig. 12 shows the determination result of the system stability for each event case by the system stability evaluation unit 23. For example, the upper part of Fig. 12 shows whether there is transient stability, whether there is frequency stability, whether there is voltage stability, etc. In the figure, "○" indicates stability, and "×" indicates lack of stability. The system stability evaluation unit 23 determines these stabilities using thresholds set for each stability. This provides important stability indicators for each event.

[0052] The middle section of Figure 12 shows combination patterns of power supply control modes. For example, in pattern 1, VSG control is specified for power supply A, droop control for power supply B, and Volt-Watt control for power supply C. The other controls in the figure are other selectable control modes. In this way, by setting a specified pattern, the control mode can be determined in the same way as the countermeasures table for power control targets described above.

[0053] The bottom part of FIG. 12 shows the results of evaluating the system stability for each event case of each pattern (the combination pattern selected in the middle part of FIG. 12). In Pattern 1, the transient stability and voltage stability of Event 1 are improved. In Pattern 2, the frequency stability of Event 2 is improved. From the system evaluation results of each pattern, the pattern with the largest total number of improvements is determined as the control mode. In addition to the number of improvements, the number of deteriorations may also be taken into consideration, and the system stability evaluation result may be set as "number of improvements - number of deteriorations." Alternatively, instead of the number of improvements, the margin and violation from the threshold value that is the stability limit may be used.

[0054] Furthermore, to reduce the number of combinations, the voltage class of the target inverter power supply may be limited to extra-high voltage systems, for example. Also, the inverter power supplies may be grouped by their interconnection positions, and a control mode may be determined for each group. If a group contains inverter power supplies with different control modes, the control modes may be classified by effective stability, and the control mode may be set. In this way, by using the control mode combinations and stability improvement indexes generated in the lower part of FIG. 12, the power system stabilization system 100 of this embodiment can determine an appropriate control mode pattern.

[0055] When determining stability, the stability index and threshold may be, for example, in the case of transient stability, the generator internal phase angle may be used as the index and the threshold may be 180 degrees (the magnitude of the generator internal phase angle at which the generator loses synchronism). For example, in the case of voltage stability, the total demand (active power) of the system may be used as the index and the critical active power at which voltage collapse occurs may be used as the threshold. For example, in the case of frequency stability, the frequency change rate at the time of power supply failure may be used as the index and the frequency change rate at which the inverter power supply fails may be used as the threshold.

[0056] Furthermore, in the example shown in FIG. 12, the stability threshold is used to determine whether the item is acceptable or unacceptable ("◯" or "X"), but a numerical value may be used as the difference from the stability threshold.

[0057] Furthermore, when grouping inverter power sources, for example, inverter power sources that are close in electrical distance (such as transmission line impedance) may be grouped together, or inverter power sources that are geographically close in interconnection position may be grouped together. In addition to these grouping factors, groups may also be formed according to the type of inverter power supply (for example, grid forming inverter or grid following inverter).

[0058] Furthermore, in the example shown in FIG. 12, the determination is made based on the total number of improvements. By determining based on the total number of improvements in this way, an appropriate one can be easily selected. On the other hand, when determining system stability, the determination may be made based on a numerical value indicating the degree of improvement in system stability. By determining based on a numerical value indicating the degree of improvement in stability and selecting an appropriate one, stability can be reliably improved. Furthermore, the target event cases or target system stability may be arbitrarily limited to set the control mode. Furthermore, based on the evaluation results of the system stability, the event with the lowest stability may be set as the control target.

[0059] Furthermore, the control mode may be set to be updated again after an event such as a grid failure or power outage occurs, which can contribute to grid stabilization after the event occurs.

[0060] Furthermore, the control mode setting unit 24 may set control parameters in addition to setting the control mode of the inverter power supply. For example, in the case of VSG control of a grid-forming inverter, the control parameters are the pseudo inertia number and pseudo damping coefficient incorporated in the control algorithm. Other control parameters include PID (Proportional-Integral-Differential) control parameters included in the current control system and voltage control system of the inverter power supply. As a method for determining the control parameters, for example, the control parameters may be added to the combination patterns of the control modes, or the control parameters of each inverter power supply may be determined by trial and error after the control modes have been determined. By including control parameters in this way, it becomes possible to control the inverter power supply more appropriately, which contributes to grid stabilization.

[0061] <Example of control mode setting by power system stabilization device 10> FIG. 13 shows an example of a method for setting the control mode of the inverter power supply by the power system stabilization device 10. In FIG. The top part of Figure 13 shows an example of a system cross section as of 8:00 on April 1, 2022. Here, as a result of the system stability assessment, it has been determined that the cross section has unstable transient stability, and VSG control, Volt-Var control, and other controls that are highly effective in improving transient stability have been set.

[0062] The bottom part of Figure 13 shows an example of a system cross section as of 12:00 on April 1, 2022. Here, as a result of the system stability assessment, it has been determined that the cross section has unstable frequency stability, and droop control, frequency-watt control, and other controls that are highly effective in improving frequency stability have been set. As described above, the power system stabilizing device 10 can appropriately set the control mode of the inverter power supply depending on the state of the power system.

[0063] [Example of power system stabilizer display] 14 shows an example of the display unit 102. The display unit 102 displays the state of the power grid and the control mode of the target power source. In Fig. 14, the state of the power system is illustrated as the state at each time shown in Fig. 13, and the control mode of each inverter power supply is shown. Fig. 14 also shows a list of the control modes of the target power supplies.

[0064] In this embodiment, the display method is exemplified by a monitor display on a computer system, but a mobile terminal or a screen display type accessory may also be used. Also, as shown in the lower right of Fig. 14, the control for each event case may be displayed. By displaying the control mode of the target power supply on the display unit 102 in this way, it becomes possible to operate the system by utilizing the control mode of the inverter power supply.

[0065] [Effects of the first embodiment] As described above, according to this embodiment, the control mode determination unit 20 determines the control mode of the inverter power supply based on the system stability calculation result, and therefore the most effective control mode for the inverter power supply can be set. In particular, in this embodiment, the control mode set for the inverter power supply changes depending on the system state, and the system state can be appropriately controlled by the mode setting of the inverter power supply. The inverter power supply is connected to a renewable energy power supply, and has the effect of stabilizing the grid state by using the configuration of the renewable energy power supply. Furthermore, the control modes that can be set for each inverter power supply are acquired and selected in advance as shown in Figure 6, so that an appropriate control mode can be set.

[0066] <Second embodiment> Next, a power system stabilization system and a power system stabilization method according to a second embodiment of the present invention will be described with reference to Figures 15 to 20. In Figures 15 to 20 illustrating the second embodiment, parts corresponding to Figures 1 to 14 described in the first embodiment are given the same reference numerals, and duplicated explanations will be omitted.

[0067] [Configuration of power system stabilization system] FIG. 15 illustrates the overall configuration of a power system stabilization device 10A when the power system stabilization system according to the second embodiment is applied to a power system. The power system stabilization device 10A shown in FIG. 15 differs from the power system stabilization device 10 shown in the first embodiment (FIG. 1) in that it newly includes a database DB10 of power sources to be controlled, a system fault database DB11, a control table creation result database DB12, and a control object determination result database DB13.

[0068] The database DB10 for power supply to be controlled stores targets for power supply control (power control) when a system event occurs. The system failure database DB11 stores system failure information. This system failure information is received from the measurement device 150 via the communication network 106. The control table creation result database DB12 stores the control table setting results. The control object determination result database DB13 stores the results of commands given to the control object. The rest of the configuration of the power system stabilization device 10A is the same as that of the power system stabilization device 10 shown in FIG.

[0069] [Processing configuration of power system stabilization device] FIG. 16 is a configuration diagram showing an example of processing by the power system stabilization device 10A. The power system stabilization device 10A differs from the power system stabilization device 10 shown in the first embodiment (FIG. 2) in that it includes a system stabilization calculation unit 30, a control decision unit 40, a database DB10 of power sources to be controlled, a system fault database DB11, a control table creation result database DB12, and a control target determination result database DB13. Furthermore, the control mode setting unit 24 transmits the control mode setting result to the system stability calculation unit 32 .

[0070] The system stabilization calculation unit 30 is made up of a system state estimation unit 31, a system stability calculation unit 32, a control table creation unit 33, and a control table transmission unit . The system state estimation unit 31 estimates the system state using the system configuration information stored in the system configuration database DB1 and the system measurement information stored in the system measurement database DB2, and transmits the result to the system stability calculation unit 32 and stores it in the system state estimation result database DB5.

[0071] The system stability calculation unit 32 calculates the system stability using the system state estimation result from the system state estimation unit 31, the control mode setting result from the control mode setting unit 24, and the event information stored in the event case database DB3, and transmits the result to the control table creation unit 33 and stores it in the control table creation result database DB12. The control table creation unit 33 creates a control table using the system stability calculation results from the system stability calculation unit 32 and the power source information to be controlled from the power source database DB10, and transmits the control table to the control table transmission unit 34 and stores it in the control table creation result database DB12. The control table transmitting unit 34 transmits the control table creation result of the control table creating unit 33 to the control determining unit 40 .

[0072] The control decision unit 40 is composed of a control target decision unit 41 and a control command unit 42. The control target determination unit 41 determines a power source to be controlled by using the system failure information stored in the system failure database DB11 and the control table creation result transmitted from the control table transmission unit 34 of the system stabilization calculation unit 30. Then, the control target determination unit 41 transmits the result to the control command unit 42 and stores it in the control target determination result database DB13. The control command unit 42 transmits the control command result from the control target determination unit 41 to the power source that is the command target via the communication network 106.

[0073] [Explanation of databases DB10 to DB13] FIG. 17 shows an example of the database DB10 for power control-target power sources. Here, power control (power supply control) is a general term for equipment that changes its state to maintain the stability and reliability of the grid, and in this embodiment refers to thermal power plants and inverter power supplies. The power supply type refers to the specific type of generator in the power plant, such as a synchronous machine or an induction machine in the case of a thermal power plant. By classifying the types in this way, it is possible to narrow down the targets for power control when calculating stabilization measures (control tables).

[0074] 18 shows an example of the system failure database DB11. The system failure database DB11 stores data such as the location of the failure and the state of the failure as system failure data.

[0075] [Processing of the system stabilization calculation unit 30] FIG. 19 is a flowchart showing the processing performed by the system stabilization calculation unit 30. First, the system state estimation unit 31 of the system stabilization calculation unit 30 estimates the state using the system configuration database DB1, the system configuration database DB1, and the system measurement database DB2, and stores the state estimation result in the system state estimation result database DB8 (step S300).

[0076] Then, the system state estimation unit 31 selects a contingency fault using the event case database DB3 (step S301). Furthermore, the system state estimation unit 31 reads the control mode currently set in the inverter power supply and reflects it in the analysis conditions for system stability (step S302). Thereafter, the system stability calculation unit 32 calculates system stability based on the contingency fault selected in step S301 (step S303). The system stability here includes transient stability, frequency stability, voltage stability, and the like.

[0077] Furthermore, the control table creating unit 33 creates a control table using the system stability calculation result in step S303, and stores the control table in the control table creation result database DB12 (step S304). Then, the control table creating unit 33 checks whether all contingencies (events) have been selected (step S305). If there are any contingencies (events) that have not been selected in step S305 (NO in step S305), the process returns to step S301. If all contingency faults (events) have been selected in step S305 (YES in step S305), the control table transmitting unit 34 transmits the control table created in step S304 to the control determining unit 40 (step S306).

[0078] [Control decision processing] FIG. 20 is a flowchart showing the processing of the control decision unit 40. First, the control target determining unit 41 of the control determining unit 40 receives the system failure data (step S400). Then, the control object determination unit 41 determines a control object using the received system failure data from the system failure database DB11 and the control table transmitted from the control table transmission unit 34, and stores the determined control object in the control object result database DB13 (step S401). When the control target is determined in step S401, the control command unit 42 transmits a control command to the control target via the communication network 106 (step S402).

[0079] [Effects of the second embodiment] As described above, according to this embodiment, the system stabilization calculation unit 30 creates a control table using the control mode of the inverter power supply determined by the control mode determination unit 20. This enables power supply control that takes into account the system stabilization of the inverter power supply, thereby reducing the amount of power supply control.

[0080] In the second embodiment, the control mode determination unit 20 and the system stabilization calculation unit 30 may operate at different cycles. For example, the system stabilization calculation unit 30 may perform calculations at a relatively short cycle each time the system state is acquired, and the calculations for determining the control mode may be performed at a longer cycle, thereby reducing the burden of calculations for determining the control mode.

[0081] In the second embodiment, the generator control table is created using the control mode setting of the inverter power supply determined by the control mode determination unit 20, but the reverse may also be true. In this case, the control mode setting unit 24 of the control mode determination unit 20 may set the control mode using the method described in the first embodiment, or the control table creation unit 33 may set the control mode for the event case with the largest power supply control amount.

[0082] [Example of another configuration of the power system stabilization device 10A] When the power system stabilizing device 10A sets the control mode of the inverter power supply, it may refer to the supply and demand plan. That is, as shown in FIG. 21, a power system stabilizing device 10A may include a supply and demand planning device 50. The supply and demand planning device 50 includes a supply planning unit 51, a renewable energy output control unit 52, and a supply plan database DB14.

[0083] The supply planning unit 51 creates a supply plan (supply and demand plan) for the power system 1 and stores it in the supply plan database DB14. The renewable energy output control unit 52 controls the power generator as a renewable energy output, based on the supply plan created by the supply plan unit 51.

[0084] The control mode setting unit 24 of the control mode determination unit 20 determines the control state of the renewable energy output created by the supply and demand planning device 50, and then sets the control mode of the inverter power supply. In this way, by setting the control mode of the inverter power supply taking into account the supply and demand plan in the supply and demand planning device 50, it is possible to set the control mode of the inverter power supply that will result in the optimal system state even when some control is applied to the renewable energy output or when there is a change in the renewable energy output due to weather, wind speed, etc.

[0085] FIG. 22 shows an example of setting a control mode in consideration of the supply and demand plan in the supply and demand planning device 50. The supply plan database DB14 of the supply and demand planning device 50 stores output plan values ​​of renewable energy such as solar power generation and wind power generation. Here, a power generator that obtains renewable energy may perform an operation that limits power generation output in advance (deload operation) or output suppression based on a supply and demand plan.

[0086] That is, in a certain time period, the output of the corresponding generator may reach its upper limit and be restricted, as shown in Fig. 22. In response to this, as shown in Fig. 21, when the power system stabilization device 10A sets the control mode of the inverter power supply, it sets the control mode of the inverter power supply by referring to the supply and demand plan, which may enable operation that makes use of the increase margin that is limited by deload operation or output suppression. In this way, a more detailed control mode can be set by setting the control mode of the inverter power supply in cooperation with the supply and demand plan in the supply and demand planning device 50. That is, in the power system stabilization device 10A, the control mode of the inverter power supply is dynamically set in accordance with the supply and demand plan, and more appropriate stabilization of the power system can be achieved. Dynamically setting the control mode of the inverter power supply in accordance with the supply and demand plan is just one example, and the control mode of the inverter power supply may be dynamically set based on other factors.

[0087] <Modification> The embodiments described above have been described in detail to make the present invention easier to understand, and are not necessarily limited to those having all of the configurations described. Furthermore, the configurations and processes described in the above-described embodiments can be modified or changed in various ways.

[0088] For example, when communication between the power system stabilization device 10 or 10A and the inverter power supply is disabled, each inverter power supply may operate in a control mode set in advance for when communication is disabled, or may continue to be set in the latest control mode.

[0089] Furthermore, when the power distribution system is in islanding operation due to system division, the inverter power supply may prioritize the islanding operation mode rather than the control mode set by the power system stabilization system.

[0090] 1 and 15 are configured to include an arithmetic processing unit having a processor and a memory, other arithmetic processing units may be used. For example, the power system stabilization devices 10 and 10A may implement part or all of the processing functions of the processor 104 using dedicated hardware such as an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit).

[0091] In addition, in each configuration diagram such as Figures 1 and 2, only control lines and information lines that are considered necessary for explanation are shown, and not all control lines and information lines in the product are necessarily shown. In reality, it can be assumed that almost all components are interconnected. Also, with regard to the flowcharts shown in Figures 10, 11, 19, and 20, the processing order may be changed or multiple processes may be executed simultaneously as long as the processing results are the same.

[0092] Furthermore, the program database DB9 needs to be equipped with a program that executes the processes described in the flowcharts of Figures 10, 11, 19, 20, etc., and the program may be stored in a memory that stores the program, or may be stored in an external memory, an IC card, an SD card, an optical disk, or other recording medium and transferred to the power system stabilization device 10 or 10A. [Explanation of symbols]

[0093] 1,1A...power system, 2...generator, 3,3A,3B...bus, 4,4A,4B...transformer, 5...transmission line, 6...inverter power supply (renewable energy power supply), 7...load, 10,10A...power system stabilization device, 20...control mode determination unit, 21...system state estimation unit, 22...system stability calculation unit, 23...system stability evaluation unit, 24...control mode determination unit, 25...control mode transmission unit, 30...system stabilization calculation unit, 31...system state estimation unit, 32...system stability calculation unit, 33...control table creation unit, 34...control table transmission unit, 40...control determination unit, 41...control target determination unit, 42...control command unit, 50...supply and demand planning device, 51...supply planning unit, 52...renewable energy output control unit, 100...system stabilization system, 101...input unit, 102...display unit, 103...communication unit, 104...processor processor, 105...memory, 106...communication network, 107...bus, 150...measuring device, 200...monitoring control device, 204...control mode setting unit, 205...control mode transmission unit, DB1...system configuration database, DB2...system measurement database, DB3...event case database, DB4...inverter power supply equipment information database, DB5...system state estimation result database, DB6...system stability calculation result database, DB7...system stability evaluation result database, DB8...control mode setting result database, DB9...program database, DB10...power supply database to be controlled, DB11...system fault database, DB12...control table creation result database, DB13...control target determination result database, DB14...supply plan database

Claims

1. A power system stabilization device that stabilizes a predetermined power system, a system state estimation unit that estimates a system state of the power system using system configuration data and system measurement data of the power system; a system stability calculation unit that calculates the system stability of the power system using an event case; a system stability evaluation unit that evaluates system stability based on the calculation result of the system stability calculation unit; a control mode setting unit that sets a control mode of an inverter power supply connected to the power grid based on a result of the grid stability evaluation by the grid stability evaluation unit; a control mode transmission unit that transmits the control mode set by the control mode setting unit to the inverter power supply. Power system stabilization system.

2. The control mode setting unit is for an inverter power supply connected to a renewable energy power supply. The power system stabilization system according to claim 1 .

3. The inverter power supply can be set to a plurality of control modes, and the control mode setting unit acquires the control mode that can be set in the inverter power supply connected to the power grid. The power system stabilization system according to claim 1 .

4. The control mode setting unit dynamically changes the control mode depending on the state of the target power system. The power system stabilization system according to claim 1 .

5. The control mode setting unit sets the combination of control modes of the target inverter power supplies that results in the greatest improvement in system stability as the control mode. The power system stabilization system according to claim 1 .

6. The control mode setting unit sets, as a control mode, a combination that provides the highest degree of improvement in the power grid from among combinations of control modes of the target inverter power supplies. The power system stabilization system according to claim 1 .

7. The control mode set by the control mode setting unit includes a control parameter. The power system stabilization system according to claim 1 .

8. Furthermore, a system stabilization calculation unit that creates a control table using data on the inverter power supply to be controlled and calculation results of system stability; A control decision unit is provided that decides and controls the inverter power supply to be controlled using system fault data. The power system stabilization system according to claim 1 .

9. The system stabilization calculation unit and the control decision unit operate at different cycles. The power system stabilization system according to claim 8.

10. A power system stabilization method for executing a process for stabilizing a predetermined power system by calculation using a computer, The computer a system state estimation process for estimating a system state of the power system using system configuration data and system measurement data of the power system; a system stability calculation process for calculating the system stability of the power system using an event case; a system stability evaluation process for evaluating system stability based on a calculation result of the system stability calculation process; a control mode setting process for setting a control mode of an inverter power supply connected to the power grid based on an evaluation result of the grid stability in the grid stability evaluation process; a control mode transmission process of transmitting the control mode set by the control mode setting process to the inverter power supply. Power system stabilization method.

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