Power grid stabilizing system and power grid stabilizing method

Abstract

This power grid stabilizing system comprises: a grid state estimation unit that estimates the grid state of a power grid by using grid configuration data and grid measurement data of the power grid; a grid stability calculation unit that calculates the grid stability of the power grid by using an event case; a grid stability evaluation unit that evaluates the grid stability on the basis of the calculation result of the grid stability calculation unit; a control mode setting unit that sets a control mode of an inverter power source connected to the power grid, on the basis of the evaluation result of the grid stability by the grid 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 source.

Description

Title of Invention: POWER GRID STABILIZING SYSTEM AND POWER GRID STABILIZING METHOD Technical Field

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

[0002] Regarding a power system, it has been proposed to connect a power system stabilization apparatus, calculate a control target (on a generation-side or a load-side) in advance (pre-calculation) using system information before event occurrence of an anticipated event such as a fault, and perform control based on event information and a precalculation result when the event occurs.

[0003] PTL 1 proposes a power system stabilization system that preferentially controls a renewable energy power source (inverter power source) over a synchronous machine. That is, PTL 1 discloses a power system stabilization apparatus that detects occurrence of an accident in a power system incorporating a renewable energy power generation apparatus in addition to a plurality of generators and prevents generator step-out at the time of the accident. PTL 1 discloses a technique for preventing generator step-out by stopping the renewable energy power generation apparatus . Citation List Patent Literature

[0004] PTL 1: JP6223833B Summary of Invention Technical Problem

[0005] In recent years, along with expansion of an inverter power source, in order to cope with a decrease in stability of a system when the inverter power source is connected to the system, it has been studied to provide power source stabilization to the inverter power source. For example, a smart inverter is one of inverter power sources having power source stabilization. The smart inverter has a communication function and a plurality of control modes having a system stabilization effect such as Frequency-Watt control and Volt-Var control. Details of these control modes will be described in embodiments to be described later.

[0006] In addition, there is an inverter power source called a grid forming inverter that operates as a voltage source to contribute to system stabilization. The grid forming inverter includes, as control modes, a plurality of control modes such as virtual synchronous generator (VSG) control, droop control, and virtual oscillator control.

[0007] In contrast to these smart inverters and grid forming inverters, an inverter power source in the related art is called a grid following inverter. Since this grid following inverter outputs active power and reactive power by synchronizing with voltage and current phases of a system, an ability to support the system at the time of system disturbances is low. The smart inverter described above is defined as a grid following inverter .

[0008] Meanwhile, the grid forming inverter can output independently of the voltage and current phases of the system, and can support the system with the same or similar characteristics as those of a synchronous generator in the related art even at the time of system disturbances.

[0009] Changing the control mode of these inverter power sources contributes to stabilization of a connected power source system, but in the related art, as disclosed in PTL 1, control for changing the control mode of the inverter power sources is not performed when controlling for an event such as a fault. That is, control by the smart inverter envisioned in the related art involves, for example, when power generation of renewable energy such as solar power generation greatly fluctuates, changing the control mode of the inverter connected to the power generation apparatus to stabilize the system. Therefore, an inverter power source such as a smart inverter does not cope with a fault in the power system, and it cannot be said that sufficient stabilization processing is performed at the time of a system fault.

[0010] An object of the invention is to provide a power system stabilization system and a power system stabilization method that can determine an effective control method according to a state of a power system in the power system interconnected with a power conversion apparatus having a plurality of control methods contributing to system stabilization. Solution to Problem

[0011] In order to solve the above problems, for example, a configuration described in the claims is adopted. The present application includes a plurality of methods for solving the above problems, and an example thereof is a power system stabilization apparatus for stabilizing a predetermined power system, the power system stabilization system including: a system state estimation unit configured to estimate a system state of the power system using system configuration data and system measurement data of the power system; a system stability calculation unit configured to calculate system stability of the power system using an event case; a system stability evaluation unit configured to evaluate the system stability based on a calculation result of the system stability calculation unit; a control mode setting unit configured to set a control mode of an inverter power source connected to the power system based on an evaluation result of the system stability by the system stability evaluation unit; and a control mode transmission unit configured to transmit the control mode set by the control mode setting unit to the inverter power source . Advantageous Effects of Invention

[0012] According to the invention, an effective control mode of an inverter power source can be set, thereby stabilizing a power system. Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments. Brief Description of Drawings

[0013] [FIG. 1] FIG. 1 is a configuration diagram showing an example of a power system stabilization system according to a first embodiment of the invention. [FIG. 2] FIG. 2 is a configuration diagram showing an example of a power system stabilization apparatus according to the first embodiment of the invention. [FIG. 3] FIG. 3 is a configuration diagram showing an example of a configuration database according to the first embodiment of the invention. [FIG. 4] FIG. 4 is a configuration diagram showing an example of a system measurement database according to the first embodiment of the invention. [FIG. 5] FIG. 5 is a configuration diagram showing an example of an event case database according to the first embodiment of the invention. [FIG. 6] FIG. 6 is a configuration diagram showing an example of an inverter power source equipment information database according to the first embodiment of the invention. [FIG. 7] FIG. 7 is a configuration diagram showing an example of a system state estimation result database according to the first embodiment of the invention. [FIG. 8] FIG. 8 is a configuration diagram showing an example of a system stability calculation result database according to the first embodiment of the invention. [FIG. 9] FIG. 9 is a configuration diagram showing an example of a control mode setting result database according to the first embodiment of the invention. [FIG. 10] FIG. 10 is a flowchart showing a processing example of a control mode determination unit of the power system stabilization system according to the first embodiment of the invention. [FIG. 11] FIG. 11 is a flowchart showing a processing example of a control mode setting unit according to the first embodiment of the invention. [FIG. 12] FIG. 12 shows an example of a control mode setting method in the control mode determination unit according to the first embodiment of the invention. [FIG. 13] FIG. 13 shows an example of setting an inverter power source control mode by the power system stabilization apparatus according to the first embodiment of the invention. [FIG. 14] FIG. 14 is a diagram showing a display example of a display unit according to the first embodiment of the invention. [FIG. 15] FIG. 15 is a configuration diagram showing an example of a power system stabilization system according to a second embodiment of the invention. [FIG. 16] FIG. 16 is a configuration diagram showing an example of a power system stabilization apparatus according to a second embodiment of the invention. [FIG. 17] FIG. 17 is a diagram showing an example of a power source control target power source database according to the second embodiment of the invention. [FIG. 18] FIG. 18 shows an example of a system fault database according to the second embodiment of the invention. [FIG. 19] FIG. 19 is a flowchart showing a processing example of a system stabilization calculation unit according to the second embodiment of the invention. [FIG. 20] FIG. 20 is a flowchart showing a processing example of a control determination unit according to the second embodiment of the invention. [FIG. 21] FIG. 21 is a configuration diagram showing another example of the power system stabilization apparatus according to the second embodiment of the invention. [FIG. 22] FIG. 22 is a diagram showing an output example according to the example in FIG. 21. Description of Embodiments

[0014] <First Embodiment> Hereinafter, a power system stabilization system and a power system stabilization method according to a first embodiment of the invention will be described with reference to FIGS. 1 to 14.

[0015] [Configuration of Power System Stabilization System] FIG. 1 shows an overall configuration of a power system stabilization apparatus 10 when the power system stabilization system according to the first embodiment of the invention is applied to a power system. An upper part in FIG. 1 shows a hardware structure of the power system stabilization apparatus 10. The power system stabilization apparatus 10 includes an input unit 101, a display unit 102, a communication unit 103, a processor 104, a memory 105, a program database DB9, and a bus 107. The program database DB9 stores programs for operating a computer as the power system stabilization apparatus 10. These components and databases DB1 to DB8 to be described later are connected via the bus 107. The communication unit 103 communicates with a measuring instrument and a control terminal of a power system 1 via a communication network 106.

[0016] The following databases DB1 to DB8 are connected to the bus 107. These databases DB1 to DB8 are also implemented by executing the programs stored in the program database DB9. That is, the power system stabilization apparatus 10 includes a system configuration database DB1, a system measurement database DB2, an event case database DB3, an inverter power source 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 input equipment operated by an operator, such as a keyboard or a mouse, and inputs information to the system via a universal serial bus (USB). The display unit 102 includes, for example, a monitor, and displays input and output data of the system as an image. The display unit 102 may output sound or vibration, such as audio output, alarm sound output, or vibration output linked to alarm activation.

[0018] The communication unit 103 communicates with other equipment in the power system 1 via the communication network 106. The processor 104 executes a calculation program acquired from the program database DB9 to instruct image data to be displayed, search for data in various databases, and the like. The processor 104 may be implemented as one or a plurality of semiconductor chips, or may be implemented as a computer device such as a calculation server.

[0019] The memory 105 includes, for example, a random access memory (RAM) and a read only member (ROM). For example, the ROM stores a computer program, and the RAM temporarily stores calculation result data, image data, a processing program, and the like required for each processing step. The communication network 106 such as a wide-area Ethernet (registered trademark) or a public line exchanges data between the system and equipment in the power system 1. The bus 107 connects various elements of the power system stabilization apparatus 10. Data transfer between various elements is executed through the bus 107.

[0020] Next, the databases DB1 to DB8 provided in the power system stabilization apparatus 10 will be described. The system configuration database DB1 stores a power system connection configuration, a generator model, a load model, a load position, a generator position, a parameter of a power transmission route (a power transmission line or a transformer), a bus position, a breaker position, and the like. A system model as a system configuration uses a busbranch model simply representing a connection configuration of equipment or a node-breaker model representing a physical connection configuration of equipment. The system configuration includes a system connection configuration generated from breaker information obtained from measurement information. In general, in the embodiment, if the system configuration is estimated by a topology processor, the system configuration is considered to be preprocessed via the communication unit.

[0021] The system measurement database DB2 stores measurement information on the power system 1. The event case database DB3 stores information on an event that may occur in the power system 1. The inverter power source equipment information database DB4 stores information on inverter power source equipment. The system state estimation result database DB5 stores a state of the power system estimated based on the measurement information and system configuration data. The system stability calculation result database DB6 stores a system stability calculation result obtained using a system estimation result created by a system state estimation unit 21 (see FIG. 2) and an event case stored in the event case database DB3.

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

[0023] [Power System Configuration] Next, the power system 1 shown on a lower part in FIG. 1 will be described. The power system 1 to which the power system stabilization apparatus 10 of the embodiment is applied refers to a power transmission system 1A in a narrow sense, and is shown as a concept including a power generation system in a broad sense. As shown in the lower part in FIG. 1, the power system 1 includes a generator 2, buses 3 (3A, 3B, 3C, and 3D), transformers 4 (4A and 4B), power transmission lines 5 (5A and 5B), a renewable energy power source 6, and a load 7.

[0024] The configuration of the power system 1 shown in FIG. 1 is an example, and the power system 1 may include, in addition to the elements shown in FIG. 1, phase modifying equipment or any one or a plurality of pieces of equipment among power storage apparatuses such as a battery, a rechargeable secondary battery, an electric vehicle storage battery, a flywheel, and phase modifying equipment.

[0025] These devices and equipment constituting the power system 1 are monitored and controlled from the viewpoint of securing stability of the power system 1, and for example, control and protection are appropriately executed by a control signal from a monitoring control apparatus 200 connected to the communication network 106. Meanwhile, for such monitoring control, measurement data such as a current, a voltage, and other state signals at each place is directly or indirectly taken into the monitoring control apparatus 200 via the communication network 106 from various measurement apparatuses (not shown) provided at each place in the power system.

[0026] Similarly, the power system stabilization apparatus 10 receives a measurement signal from the measurement apparatus at each part of the power system 1. Here, the generator 2 includes a large-scale power source such as a thermal power generator, a hydroelectric generator, or a nuclear power generator. The renewable energy power source 6 includes a distributed power source such as solar power generation or wind power generation. The renewable energy power source 6 includes an inverter power source and generates a power source to be output to the power system 1. As the inverter power source provided in the renewable energy power source 6 here, a smart inverter, a grid forming inverter, or the like is used The inverter power source has a communication function and a plurality of control modes such as Frequency-Watt control and Volt-Var control. Examples of the plurality of control modes will be described later with reference to FIG. 6.

[0027] The measurement apparatus for measuring the power system 1 is an apparatus that measures any one or a plurality of a node voltage V, a branch current I, a power factor ¢, active power P, reactive power Q, and a fault condition. Specifically, instrument transformers (a voltage transformer (VT) and a potential transformer (PT) ) , a current transformer (CT), a bus protection (BP) relay, a power transmission line protection (LP) relay, and a transformer protection (TP) relay are used.

[0028] These measurement apparatuses have a function as a telemeter (TM) that transmits data including a data measurement location identification ID and an internal timestamp of the measurement apparatuses. Each measurement apparatus may be an apparatus that measures power information with an absolute time (voltage phasor information) using a global positioning system (GPS), a phase measurement apparatus (phasor measurement unit (PMU)), or other measurement equipment. Further, the measurement apparatus is described as being located in the power system 1A in a narrow sense, and may alternatively be provided at the bus 3, the line (power transmission line) 5, or the like connected to the generator 2, the transformer 4, a measurement apparatus 150, and the load 7.

[0029] The measurement data is each piece of data measured by the measurement apparatus (system measurement data), is received by the power system stabilization apparatus 10 via the communication network 106, and is stored in the system measurement database DB2. However, instead of directly receiving system data from the measurement apparatus, the measurement data may be first aggregated in the monitoring control apparatus 200 and then stored in the system measurement database DB2 via the communication network 106. Alternatively, the power system stabilization apparatus 10 may receive data from both the measurement apparatus and the monitoring control apparatus 200 via the communication network 106 and store the data in the system measurement database DB2. The system measurement data may include a unique number for identifying data and a timestamp. The system measurement data in the past may be retained in the system measurement database DB2 in advance.

[0030] [Processing Configuration of Power System Stabilization Apparatus] FIG. 2 is a configuration diagram showing processing performed by the power system stabilization apparatus 10. As described above, the power system stabilization apparatus 10 includes the system configuration database DB1, the system measurement database DB2, the event case database DB3, the inverter power source equipment information database DB4, the system state estimation result database DB5, the system stability calculation result database DBS, the system stability evaluation result database DB7, the control mode setting result database DB8, and a control mode determination unit 20.

[0031] The control mode determination unit 20 includes the 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 system state estimation processing of estimating a system state using system configuration information stored in the system configuration database DB1 and system measurement information stored in the system measurement database DB2. Then, the system state estimation unit 21 transmits the estimated system state to the system stability calculation unit 22 and stores the estimated system state in the system state estimation result database DB5. The system stability calculation unit 22 performs system stability calculation processing of calculating system stability for a target system section using a system state estimation result of 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 processing to the system stability evaluation unit 23 and stores the system stability in the system stability evaluation result database DB7.

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

[0033] [Description of Database (DB1 to DB8)] Here, the databases DB1 to DB8 retained by the power system stabilization apparatus 10 will be described. The system configuration database DB1 stores data constituting the power system 1. FIG. 3 shows an example of the system configuration database DB1 of the power system stabilization apparatus 10. The system configuration database DB1 stores impedance of a power transmission line connecting the buses 3 (for example, the bus 3A and the bus 3B) in the power system 1. By storing the data in this manner, it is possible to predict and calculate a route through which electric power flows when power generation and consumption are determined. The system configuration database DB1 also stores a switching state (SV state) of the power transmission line.

[0034] FIG. 4 shows an example of the system measurement database DB2 of the power system stabilization apparatus 10. The system measurement database DB2 stores a measured time and a measured value as the measurement information on the power system. For example, active power (P) and reactive power (Q) of each power transmission line, and a voltage (V) of each bus are stored in the system measurement database DB2. A value stored at this time may be a unit of direct measurement information (for example, MW), or may be a normalized p.u value. In the example in FIG. 4, the latter case is shown as an example where the value is stored as the p.u value.

[0035] FIG. 5 shows an example of the event case database DB3 of the power system stabilization apparatus 10. The event case indicates, for example, an event such as a fault in the power transmission line, and includes information on a fault location (such as a power receiving end of a power transmission line A) and a fault condition. By retaining such an event case database DB3, innumerable events can be narrowed down to an appropriate range.

[0036] FIG. 6 shows an example of the inverter power source equipment information database DB4 of the power system stabilization apparatus 10. The inverter power source equipment information database DB4 stores a name, a rated output, an equipment capacity, an interconnection position (connected bus), a voltage class, an inverter type, and a control mode of the target inverter power source. Examples of the inverter type include wind power (GEM) and solar power (GEL). Examples of the control mode 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 such information in the inverter power source equipment information database DB4, it is possible to evaluate an influence of the inverter when a simulation is executed. The information in the inverter power source 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 apparatus 10. The system state indicates a voltage (V) , a phase (5), active power (P), and reactive power (Q) of each element (a generator, a load, and the like) of the power system, and indicates states in which each element of the power system is operated. The power system stabilization apparatus 10 executes fault calculation based on such states stored in the system state estimation result database DB5. For example, the power system stabilization apparatus 10 executes fault calculation using one or more of state estimation for estimating a voltage phase of the power system based on limited measurement information and power flow calculation for calculating power flows (P and Q) based on electric power received by and output from the power system. A power system state may be generated based on the measurement information or may be generated based on future prediction information.

[0038] FIG. 8 shows an example of the system state estimation result database DB5 of the power system stabilization apparatus 10. The system state estimation result database DB5 stores time-series data of a voltage, a phase angle, active power, and reactive power for each power source as a numerical simulation result that is the system state estimation result The time-series data here is represented as, for example, a time (0.00) when an accident occurs, a next time (0.01), and so on. The system state estimation result database DB5 may store the time-series data not only for the power source but also for a bus, a power transmission line, and the like. Instead of the time-series data, a maximum value or an average value 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 stabilization apparatus 10. The control mode setting result database DB8 stores the control mode set for each inverter power source. That is, the control mode setting result database DB8 stores the control mode set for each inverter power source, such as VSG control and droop control. The control mode setting result database DBS may store a control parameter and the like in addition to the control mode setting.

[0040] [Processing of Control Mode Determination Unit] FIG. 10 is a flowchart showing processing performed by the control mode determination unit 20 of the power system stabilization apparatus 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). An estimation result of the system state obtained by the system state estimation unit 21 is stored in the system state estimation result database DB8. In estimation calculation of the system state, the system state estimation unit 21 estimates active power P, reactive power Q, a voltage V, a voltage phase angle 6, a current I, and a power factor ¢, which are most plausible for each node, branch, generator, load, and control device of the system.

[0041] Next, the control mode determination unit 20 selects an assumed event (fault) using the event case database DB3 (step SI01) . Then, the system stability calculation unit 22 of the control mode determination unit 20 calculates the system stability based on the assumed fault selected in step S101 (step S102). The system stability here is transient stability, frequency stability, voltage stability, or the like. Such calculation of the system stability is performed, for example, by calling a stability analysis program installed in advance in the power system stabilization apparatus 10.

[0042] The stability evaluation unit 23 of the control mode determination unit 20 performs stability evaluation by checking for a stability violation (step S103). For example, regarding the transient stability, the stability evaluation unit 23 uses an internal rotor angle of a synchronous generator as an evaluation index, and determines transient instability when a deviation from an internal rotor angle of a reference generator exceeds a threshold. Regarding the voltage stability, the stability evaluation unit 23 uses, as an evaluation index, a stability margin of a P-V curve where a vertical axis represents active power and a horizontal axis represents a voltage, and determines voltage instability when the stability margin exceeds a threshold. Such stability evaluation is performed for example, by calling the stability analysis program installed in advance in the power system stabilization apparatus 10.

[0043] Further, the stability evaluation unit 23 of the control mode determination unit 20 checks whether all assumed faults (events) have been selected (step S104). When there is an unselected assumed fault (event) in step S104 (NO in step S104), the processing returns to step S101.

[0044] When all assumed 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 source using the system stability evaluation result in step S103 and the inverter power source equipment information database DB4 (step S105). As a method for setting the control mode of the inverter power source here, for example, there is a method of creating a combination related to the control mode of each inverter power source, calculating an influence on the system stability for each combination, and setting a combination having a highest effect of improving the system stability as the control mode. Details of the processing 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 source 6 via the communication network 106 (step S106).

[0046] [Processing of Control Mode Setting Unit] FIG. 11 is a flowchart showing processing performed by the control mode setting unit 24 of the control mode determination unit 20. First, the control mode setting unit 24 reads inverter power source equipment information from the inverter power source equipment information database DB4 and sets a power source that is a control mode setting target (step S200). As a method for setting the target power source, all inverter power sources connected to the system may be targeted, or the target power source may be limited by a voltage class or an interconnection position. Target power sources may be grouped, and the control mode may be set for each group.

[0047] The control mode setting unit 24 determines a combination (pattern) of the control modes of the inverter power sources (step S201). The combination of the control modes may allow overlapping of the control modes between the inverter power sources. As the combination of the control modes, all combinations may be created, or the combination may be created by limiting the control modes of the inverter power sources. When the combination of the control modes is determined, the control mode setting unit 24 acquires a system stability calculation result according to each combination created in step S201 (step S202) . Further, the control mode setting unit 24 acquires an evaluation of the system stability calculation result obtained in step S202 (step S203).

[0048] The control mode setting unit 24 checks whether all combinations have been selected (step S204). When there is an unselected combination in step S204 (NO in step S204), the processing returns to step S201. When 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 source using the system stability evaluation result of each combination (step S205) .

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

[0050] [Operation Example of Control Mode Setting Unit] Next, an example of a method for setting the control mode of the inverter power source in the control mode setting unit 24 will be described. The control mode setting unit 24 creates a pattern in which the control modes for the respective power sources are combined, and calculates the system stability in a target system section for each pattern. Then, the control mode setting unit 24 performs processing of setting a pattern having a high degree of system stability improvement as the control mode. That is, the control mode setting unit 24 performs processing for selecting an effective inverter power source control mode. FIG. 12 shows an example of a control mode setting method of the control mode determination unit 20 in the embodiment. A series of examples up to the setting of the control mode will be described with reference to an upper part, a middle part, and a lower part in the figure.

[0051] The upper part in FIG. 12 shows a system stability determination result for each event case by the system stability evaluation unit 23. For example, the upper part in FIG. 12 shows whether there is transient stability, whether there is frequency stability, and whether there is voltage stability. In the figure, "o" indicates stability, and "x" indicates instability. The system stability evaluation unit 23 determines the stability using a threshold set for each type of stability. Accordingly, an important stability indicator for each event is known.

[0052] The middle part in FIG. 12 shows a combination pattern of the power source control modes. A gray portion (a portion that is not white) in the background of characters in the figure is designated control. For example, in a pattern 1, VSG control is designated for a power source A, droop control for a power source B, and Volt-Watt control for a power source C. Other control in the figure is other selectable control modes. By setting the designated pattern in this manner, the control mode can be determined in the same manner as a countermeasure table of the power control target described above .

[0053] A lower part in FIG. 12 shows a system stability evaluation result for each event case of each pattern (the combination pattern selected in the middle part in FIG. 12) . In the pattern 1, transient stability and voltage stability in an event 1 are improved. In a pattern 2, frequency stability in an event 2 is improved. Among system evaluation results of the respective patterns, a pattern having a greatest total number of improvements is determined as the control mode. In addition to the number of improvements, the number of deteriorations may be considered, and the system stability evaluation result may be set by "number of improvements - number of deteriorations". In addition, instead of the number of improvements, a margin from a stability limit threshold, a degree of violation, or the like may be used.

[0054] Further, in order to reduce the number of combinations, for example, the voltage class of the target inverter power source may be limited to an extra-high voltage system. Grouping may be performed by interconnection positions of the inverter power sources, and the control mode may be determined for each group. When inverter power sources having different control modes are contained in a group, the control modes may be classified according to effectiveness for each type of stability to set the control modes . In this way, the system stabilization system 100 according to the embodiment can determine an appropriate control mode pattern using the combination of control modes and a stability improvement index generated in the lower part in FIG. 12.

[0055] When determining stability, as an indicator and a threshold for stability, for example, in the case of transient stability, a generator internal phase angle may be used as the indicator and the threshold may be 180 degrees (magnitude of the generator internal phase angle at which generator step-out occurs). For example, in the case of voltage stability, a total system demand (active power) may be used as the indicator, and the threshold may be critical active power at which voltage collapse occurs. For example, in the case of frequency stability, a frequency change rate at the time of power source disconnection may be used as the indicator, and the threshold may be the frequency change rate when the inverter power source is disconnected.

[0056] Further, as a determination method, in the example shown in FIG. 12, pass or fail ("o" or "x") is determined using the stability threshold, and alternatively, a numerical value may be used as a difference from the stability threshold.

[0057] When the inverter power sources are grouped, for example, inverter power sources having a close electrical distance (power transmission line impedance or the like) may be grouped, or inverter power sources having geographically close interconnection positions may be grouped. In addition to these grouping factors, grouping may be performed by dividing according to inverter power source types (for example, grid forming inverters and grid following inverters).

[0058] Further, in the example shown in FIG. 12, the determination is performed based on the total number of improvements. By performing the determination based on the total number of improvements in this manner, an effect enabling easy and appropriate selection is obtained. Meanwhile, when determining the system stability, the determination may be performed based on a numerical value indicating the degree of system stability improvement. By performing the determination using the numerical value indicating the degree of stability improvement indicating the degree of improvement and performing appropriate selection, the stability is reliably improved. In addition, the control mode may be set by limiting the target event case and the target system stability as desired. Based on the system stability evaluation result, an event having lowest stability may be set as a control target

[0059] Further, after an event such as a system fault or power source disconnection occurs, the control mode may be updated again to perform setting. This can contribute to system stabilization after the occurrence of the event.

[0060] The control mode setting unit 24 may set the control parameter in addition to setting the control mode of the inverter power source. The control parameter is, for example, a virtual inertia constant or a virtual damping coefficient incorporated in a control algorithm in the case of VSG control of a grid forming inverter. In addition, the control parameter includes a parameter of proportionalintegral-differential (PID) control in a current control system or a voltage control system of the inverter power source . As a method for determining the control parameter, for example, the control parameter may be added to the combination pattern of the control modes, or the control parameter of each inverter power source may be determined by trial and error after the control mode is determined. By including the control parameter in this way, the inverter power source can be controlled more appropriately, which contributes to system stabilization.

[0061] <Example of Setting Control Mode by Power System Stabilization Apparatus 10> FIG. 13 shows an example of a method for setting the control mode of the inverter power source by the power system stabilization apparatus 10. In the diagram showing a control state shown in FIG. 13, power sources indicated by "SGI", "SG2", and the like are power sources other than inverter power sources, and power sources indicated by "INV1", "INV2", and the like are inverter power sources. In addition, "L" indicates a load, "W" indicates a transformer, a thick line connecting therebetween is a bus, a thin line indicates a transmission line, and a broken line indicates a communication network. An upper part in FIG. 13 shows a system section at 2022 / 4 / 1 8:00. Here, as a system stability evaluation result, it is determined that the section has unstable transient stability, and VSG control, Volt-Var control, and the like, which are highly effective for transient stability, are set.

[0062] A lower part in FIG. 13 shows a system section at 2022 / 4 / 1 12: 00. Here, as a system stability evaluation result, it is determined that the section has unstable frequency stability, and droop control, Frequency-Watt control, and the like, which are highly effective for frequency stability, are set. As described above, the power system stabilization apparatus 10 can appropriately set the control mode of the inverter power source according to the state of the power system.

[0063] [Display Example of Power System Stabilization Apparatus] FIG. 14 shows an example of the display unit 102. The display unit 102 displays the state of the power system and the control mode of the target power source. In FIG. 14, the state of the power system at each time shown in FIG. 13 is shown, and the control mode of each inverter power source is shown. FIG. 14 shows a list of control modes of the target power source. Symbols such as "SGI", "SG2", "INV1", and "INV2" shown in FIG. 14 have the same meanings as those in FIG. 13.

[0064] In this embodiment, computer system monitor display is shown as an example of a display method, and alternatively, a mobile terminal or a screen display accessory may be used. As shown in a lower right part in FIG. 14, control for each event case may be displayed. By displaying the control mode of the target power source on the display unit 102 in this manner, an operation using the control mode of the inverter power source is enabled.

[0065] [Effects of First Embodiment] As described above, according to the embodiment, since the control mode determination unit 20 determines the control mode of the inverter power source based on the system stability calculation result, the most effective control mode of the inverter power source can be set. In particular, in the embodiment, the control mode set for the inverter power source changes according to the system state, and the system state can be appropriately controlled by inverter power source mode setting. In addition, the inverter power source is an inverter power source connected to the renewable energy power source, and has an effect of stabilizing the system state using a configuration provided in the renewable energy power source. In addition, since the control mode that can be set for each inverter power source is acquired and selected in advance as shown in FIG. 6, 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 invention will be described with reference to FIGS. 15 to 20. In FIGS. 15 to 20 showing the second embodiment, locations corresponding to those in FIGS. 1 to 14 described in the first embodiment are denoted by the same reference signs, and redundant descriptions thereof will be omitted.

[0067] [Configuration of Power System Stabilization System] FIG. 15 shows an overall configuration of a power system stabilization apparatus 10A when the power system stabilization system according to the second embodiment is applied to a power system. The power system stabilization apparatus 10A shown in FIG. 15 is different from the power system stabilization apparatus 10 shown in the first embodiment (see FIG. 1) in that a power control target power source database DB10, a system fault database DB11, a control table creation result database DB12, and a control target determination result database DB13 are newly provided.

[0068] The power control target power source database DB10 stores a target of power source control (power control) when a system event occurs. The system fault database DB11 stores system fault information. The system fault information is received from the measurement apparatus 150 via the communication network 106. The control table creation result database DB12 stores a control table setting result. The control target determination result database DB13 stores a command result for a control target. Other configurations of the power system stabilization apparatus 10A are the same as those of the power system stabilization apparatus 10 shown in FIG. 1.

[0069] [Processing Configuration of Power System Stabilization Apparatus] FIG. 16 is a configuration diagram showing an example of processing of the power system stabilization apparatus 10A. The power system stabilization apparatus 10A is different from the power system stabilization apparatus 10 shown in the first embodiment (see FIG. 2) in that a system stabilization calculation unit 30, a control determination unit 40, the power control target power source database DB10 the system fault database DB11, the control table creation result database DB12, and the control target determination result database DB13 are provided. The control mode setting unit 24 transmits a control mode setting result to the system stability calculation unit 32 .

[0070] The system stabilization calculation unit 30 includes a system state estimation unit 31, a system stability calculation unit 32, a control table creation unit 33, and a control table transmission unit 34. 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, transmits a result thereof to the system stability calculation unit 32, and stores the result 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 of the system state estimation unit 31, the control mode setting result of the control mode setting unit 24, and the event information stored in the event case database DB3, transmits a result thereof to the control table creation unit 33, and stores the result in the control table creation result database DB12. The control table creation unit 33 creates a control table using the system stability calculation result of the system stability calculation unit 32 and power control target power source information in the power control target power source database DB10, transmits the control table to the control table transmission unit 34, and stores the control table in the control table creation result database DB12 . The control table transmission unit 34 transmits a control table creation result of the control table creation unit 33 to the control determination unit 40.

[0072] The control determination unit 40 includes a control target determination unit 41 and a control command unit 42. The control target determination unit 41 determines a control target power source using the system fault information stored in the system fault 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 a result thereof to the control command unit 42 and stores the result in the control target determination result database DB13. The control command unit 42 transmits a control command result of the control target determination unit 41 to the command target power source via the communication network 106.

[0073] [Description of Databases DB10 to DB13] FIG. 17 shows an example of the power control target power source database DB10. Here, the power control (power source control) is a general term for equipment whose state is changed to maintain stability and reliability of the system, and in the embodiment, a thermal power unit and an inverter power source are shown. A power source type refers to a specific type of a generator in a power plant, such as a synchronous machine or an induction machine in the case of the thermal power unit. By categorizing into types in this way, it is possible to narrow down power control targets when calculating a stabilization measure (control table).

[0074] FIG. 18 shows an example of the system fault database DB11. The system fault database DB11 stores data such as a fault location and a fault condition as system fault data.

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

[0076] The system state estimation unit 31 selects an assumed fault using the event case database DB3 (step S301) . Further, the system state estimation unit 31 reads a control mode currently set for the inverter power source and reflects the control mode in a system stability analysis condition (step S302) . Thereafter, the system stability calculation unit 32 calculates system stability based on the assumed fault selected in step S301 (step S303). The system stability here is transient stability, frequency stability, voltage stability, or the like.

[0077] Further, the control table creation unit 33 creates a control table using a 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 creation unit 33 checks whether all assumed faults (events) have been selected (step S305) . When there is an unselected assumed fault (event) in step S305 (NO in step S305) , the processing returns to step S301. When all assumed faults (events) have been selected in step S305 (YES in step S305), the control table transmission unit 34 transmits the control table created in step S304 to the control determination unit 40 (step S306).

[0078] [Processing of Control Determination Unit] FIG. 20 is a flowchart showing processing of the control determination unit 40. First, the control target determination unit 41 of the control determination unit 40 receives the system fault data (step S400) . Then, the control target determination unit 41 determines a control target using the system fault data received from the system fault database DB11 and the control table transmitted from the control table transmission unit 34, and stores the control target in the control target 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 Second Embodiment] As described above, according to the embodiment, since the system stabilization calculation unit 30 creates the control table using the control mode of the inverter power source determined by the control mode determination unit 20, it is possible to perform power source control or the like in consideration of system stabilization of the inverter power source, and to reduce an amount of power source 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 calculation at a relatively short cycle each time the system state is acquired, and calculation for determining the control mode may be performed at a longer cycle to reduce a load of the calculation for determining the control mode.

[0081] In the second embodiment, the generator control table is created using the inverter power source control mode setting determined by the control mode determination unit 20, and alternatively, a reverse approach may be used. In this case, the control mode setting unit 24 of the control mode determination unit 20 may perform setting by the method described in the first embodiment, or may set the control mode for an event case having a greatest amount of power source control in the control table creation unit 33.

[0082] [Example of Another Configuration of Power System Stabilization Apparatus 10A] When the power system stabilization apparatus 10A sets the control mode of the inverter power source, a supply and demand plan may be referred to. That is, as shown in FIG. 21, the power system stabilization apparatus 10A may include a supply and demand plan device 50. The supply and demand plan device 50 includes a supply plan unit 51, a renewable energy output control unit 52, and a supply plan database DB14.

[0083] The supply plan unit 51 creates a supply plan (supply and demand plan) for the power system 1 and stores the supply plan in the supply plan database DB14. The renewable energy output control unit 52 controls a 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 sets the control mode of the inverter power source after determining a control state of the renewable energy output created by the supply and demand plan device 50. In this way, by setting the control mode of the inverter power source in consideration of the supply and demand plan in the supply and demand plan device 50, it is possible to set the control mode of the inverter power source in an optimal system state even when certain control is applied to the renewable energy output or when the renewable energy output changes according to weather, a wind speed, or the like.

[0085] FIG. 22 shows an example in which the control mode is set in consideration of the supply and demand plan in the supply and demand plan device 50. The supply plan database DB14 of the supply and demand plan device 50 stores a planned output value of solar power generation or wind power generation, which is renewable energy. Here, a generator that obtains renewable energy may perform an operation with a pre-restricted power generation output (deload operation) or output curtailment based on the supply and demand plan.

[0086] That is, as shown in FIG. 22, in a certain time period, the corresponding generator may reach an output upper limit and be restricted. On the other hand, as shown in FIG. 21, when the power system stabilization apparatus 10A sets the control mode of the inverter power source, by setting the control mode of the inverter power source with reference to the supply and demand plan, it is possible to perform an operation taking advantage of headroom obtained by restricting by the deload operation or the output curtailment. In this way, by setting the control mode of the inverter power source in cooperation with the supply and demand plan in the supply and demand plan device 50, it is possible to set the control mode in more detail. That is, in the power system stabilization apparatus 10A, the control mode of the inverter power source is dynamically set according to the supply and demand plan, and more appropriate power source system stabilization can be achieved. The dynamic setting of the control mode of the inverter power source according to the supply and demand plan is an example, and the control mode of the inverter power source may be dynamically set according to another factor.

[0087] <Modi fication> The embodiments described so far have been described in detail to facilitate understanding of the invention, and the invention is not necessarily limited to those including all the configurations described above. In addition, various modifications and changes can be made to the configurations and processing described in the abovedescribed embodiments.

[0088] For example, when communication between the power system stabilization apparatus 10 or 10A and the inverter power source is unavailable, each inverter power source may operate in a control mode set in advance for the time when communication is unavailable, or may continue the latest control mode setting.

[0089] When a power distribution system operates alone due to system disconnection, the inverter power source may prioritize an islanding operation mode instead of the control mode set in the power system stabilization system.

[0090] In the above-described embodiments, the power system stabilization apparatuses 10 and 10A shown in FIGS. 1 and 15 include the calculation processing unit including the processor and the memory, and alternatively, another calculation processing unit may be used. For example, in the power system stabilization apparatuses 10 and 10A, a part or all of processing functions of the processor 104 may be implemented by dedicated hardware such as a field programmable gate array (FPGA) or an application specific integrated circuit (ASIC).

[0091] In each configuration diagram such as FIGS. 1 and 2, only control lines and information lines considered to be required for descriptions are shown, and not all control lines and information lines in a product are necessarily shown. Actually, it may be considered that almost all the configurations are connected to one another. In the flowcharts shown in FIGS. 10, 11, 19, and 20, a processing order may be changed or a plurality of processing steps may be simultaneously executed as long as processing results are the same.

[0092] Further, it is required to install a program for executing the processing described in the flowcharts in FIGS 10, 11, 19, 20, and the like in the program database DB9, the program may be prepared in a memory for storing the program, or may be placed in a recording medium such as an external memory, an IC card, an SD card, or an optical disk and transferred to the power system stabilization apparatus 10 or 10A. Reference Signs List

[0093] 1, 1A. . . power system 2 . . . generator 3, 3A, 3B... bus 4, 4A, 4B... transformer 5... power transmission line 6... inverter power source (renewable energy power source) 7 . . . load 10, 10A. . . power system stabilization apparatus 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 plan device 51... supply plan unit 52... renewable energy output control unit 100... system stabilization system 101... input unit 102... display unit 103... communication unit 104... processor 105... memory 106... communication network 107... bus 150... measurement apparatus 200... monitoring control apparatus 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 source 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 control target power source database 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 system that is a power system stabilization apparatus for stabilizing a predetermined power system, the power system stabilization system comprising:a system state estimation unit configured to estimate a system state of the power system using system configuration data and system measurement data of the power system;a system stability calculation unit configured to calculate system stability of the power system using an event case;a system stability evaluation unit configured to evaluate the system stability based on a calculation result of the system stability calculation unit;a control mode setting unit configured to set a control mode of an inverter power source connected to the power system based on an evaluation result of the system stability by the system stability evaluation unit; anda control mode transmission unit configured to transmit the control mode set by the control mode setting unit to the inverter power source.

2. The power system stabilization system according to claim 1, whereinthe control mode setting unit targets the inverter power source connected to a renewable energy power source.

3. The power system stabilization system according to claim 1, whereina plurality of the control modes are settable for the inverter power source, and the control mode setting unit acquires the control mode settable in the inverter power source connected to the power system.

4. The power system stabilization system according to claim 1, whereinthe control mode setting unit dynamically changes the control mode according to a target power system state.

5. The power system stabilization system according to claim 1, whereinthe control mode setting unit sets, as the control mode, a combination having a greatest number of systemstability improvements from among combinations of the control modes of the target inverter power source.

6. The power system stabilization system according to claim 1, whereinthe control mode setting unit sets, as the control mode, a combination having a highest degree of power system improvement from among combinations of the control modes of the target inverter power source.

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

8. The power system stabilization system according to claim 1, further comprising:a system stabilization calculation unit configured to create a control table using data of the inverter power source to be controlled and the calculation result of the system stability; anda control determination unit configured to determineand control the inverter power source to be controlled using system fault data.

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

10. A power system stabilization method of executing processing for stabilizing a predetermined power system by calculating with a computer, the power system stabilization method comprising:executing, by the computer,system state estimation processing of estimating a system state of the power system using system configuration data and system measurement data of the power system;system stability calculation processing of calculating system stability of the power system using an event case;system stability evaluation processing of evaluating the system stability based on a calculation result by the system stability calculation processing;control mode setting processing of setting a control mode of an inverter power source connected to the power system based on an evaluation result of the system stability by the system stability evaluation processing; andcontrol mode transmission processing of transmitting the control mode set by the control mode setting processing to the inverter power source.

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