Information processing system, and information processing method

Abstract

To provide information about a power system for stabilizing frequency control to an outside business operator.SOLUTION: An inertia estimation device 10, which is provided in an inertia force service provision system 601, comprises: a measurement value extraction part 32 for collecting an electric amount measurement value of a power system; a system operation command detection part 31 for detecting a command of a system operation capable of estimating inertia of the power system; a PQ change amount extraction part 33 for extracting a change amount between an electric amount before performing the system operation, and an electric amount after performing the system operation; a phase change amount estimation part 34 for estimating a phase change amount of a voltage phase of a partial system in the power system, based on the change amount; an inertia estimation part 35 of the partial system for estimating inertia of the partial system, based on the phase change amount; and an inertia estimation value database DB3 for storing an inertia estimation value of the inertia of the estimated partial system so as to make it possible to be provided to an outside business operator.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to an information processing system and an information processing method. [Background technology]

[0002] The frequency of the power grid is maintained by controlling power generation so that it matches demand at every moment. If the balance between power generation and demand is disrupted, for example due to the shutdown of generators or demand, the frequency will fluctuate. If the frequency fluctuation exceeds a certain level, protective relays will be activated to disconnect power generation and load from the grid, which can result in a large-scale blackout. To maintain the balance between power generation and demand, that is, to maintain a balance of supply and demand, it is necessary to take immediate control measures, such as changing power generation output or cutting off demand.

[0003] When controlling to maintain the supply and demand balance, for example, the greater the inertial energy (inertial force) of a rotary generator, the greater the inertia. The greater the inertia, the slower the frequency change, and the more time there is for operations to maintain the supply and demand balance, making it possible to reduce the amount of load (demand) that needs to be cut off. Furthermore, the greater the inertia present in the system, the smaller the maximum frequency change in response to the difference between supply and demand (supply and demand imbalance), making it easier to maintain the frequency.

[0004] Here, the rate of change of frequency (RoCoF) is used as an index to represent the magnitude of frequency change per unit time when a supply-demand imbalance occurs, and the maximum frequency deviation (Nadir), which will be described later, is used as an index to represent the maximum value of frequency change.

[0005] In recent years, grid faults caused by natural disasters or lightning strikes have led to generator tripping, making it difficult to maintain frequency and resulting in large-scale power outages. Furthermore, in recent years, there has been an increase in inverter-type power generation facilities, such as solar power generation and wind power generation, which are connected to the grid via power converters (inverters). This has resulted in an increase in the number of rotary generators shutting down, and an increase in the number of periods during which grid inertia decreases. Since a decrease in grid inertia makes frequency more susceptible to change, measures are sometimes taken, such as operating the grid to maintain inertia above a certain level. As mentioned above, inertia is usually maintained by rotary generators. For this reason, there are sometimes restrictions imposed on inverter-type solar and wind power generation, limiting their connection to the grid above a certain level.

[0006] To address these constraints, a simulated inertia control function has been developed that allows the transient behavior of recent inverter-type generators (solar and wind power) and storage equipment to have the same inertia as a rotary generator. This function can also be applied to inverter-type loads such as charging equipment.

[0007] On the other hand, equipment with simulated inertia control functions is often installed as inverter-type power sources distributed across local transmission and distribution systems. For this reason, it is important to monitor where and how much inertia exists, and whether the total amount of inertia is sufficient to maintain frequency stability.

[0008] Furthermore, the amount of simulated inertia generated by an inverter-type power supply varies depending on its operating conditions, such as whether the inverter is activated, its output power, and its control mode. This poses a challenge in that it is difficult to grasp the amount of inertia generated by a large number of distributed inverter-type power supplies. One possible solution to this challenge is to grasp the simulated inertia control mode and the amount of inertia generated by the simulated inertia of each inverter-type power supply through sequential communication. However, the communication system and operation management system required to grasp the status of a huge number of distributed inverter-type power supplies are complex and costly. Furthermore, it would be necessary to establish a system and rules to enable information exchange with all inverter-type power supplies without exception, which would pose significant difficulties in practical operation.

[0009] When the inertia of the grid decreases, frequency changes due to supply-demand imbalances become larger, and more measures (load shedding and generator output changes) are required to maintain the grid frequency. In addition, when inverter-type power generation, which is expected to perform simulated inertia control, is stopped, a decrease in simulated inertia occurs, and frequency maintenance control that takes this decrease in inertia into account is required.

[0010] Regarding the method for measuring the inertia constant of a system, inertia H is generally defined as in equation (1), where H is the unit inertia constant (MW / s / MVA), df / dt is the frequency change rate (Hz / s), fn is the fundamental frequency (Hz), and △P is the amount of change in active power. H=0.5×(△P×fn) / (df / dt) …(1)

[0011] In this way, by incorporating a control that changes the output in response to changes in frequency into an inverter-type power supply, simulated inertia control becomes possible.

[0012] For example, Patent Document 1 describes that an inertia estimation device estimates not only a value related to the inertia of a power system in an abnormal state, but also a value related to the inertia of a power system in a normal state. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] Japanese Patent Publication No. 2022-114035 Summary of the Invention [Problem to be solved by the invention]

[0014] Patent Document 1 discloses a method for estimating the inertia of a system using inertia information of each rotary generator. However, it does not disclose a method for determining the amount of inertia, including the simulated inertia of an inverter in a local system, without using the inertia information of each generator. Therefore, even if the method disclosed in Patent Document 1 is used, it is not possible to determine the simulated inertia of the local system or the inverter-type power source included in the area where the local system is installed, and the problem of reduced frequency control accuracy cannot be solved.

[0015] The present invention has been made in view of the above circumstances, and aims to provide information about a power system for estimating the inertia of a subsystem to stabilize frequency control. [Means for solving the problem]

[0016] The information processing system according to the present invention includes an inertia estimation device that estimates the inertia of a power system, and provides information about the power system to an external business operator. The inertia estimation device includes a measurement value extraction unit that collects electrical quantity measurement values ​​of the power system, a system operation command detection unit that detects system operation commands for the power system that can estimate the inertia of the power system, a change amount extraction unit that extracts the change amount between the electrical quantity before the system operation is performed and the electrical quantity after the system operation is performed, a phase change amount estimation unit that estimates the phase change amount of the voltage phase of a subsystem in the power system based on the change amount, an inertia estimation unit that estimates the inertia of the subsystem based on the phase change amount, and an inertia estimation value database that stores the estimated inertia value of the subsystem inertia so that it can be provided to an external business operator. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide information about the power system for stabilizing frequency control by estimating the inertia of the subsystem. Problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments. [Brief explanation of the drawings]

[0018] [Figure 1] 1 shows an example of a service that utilizes an inertia estimation device according to an embodiment of the present invention. [Figure 2] 1 is a diagram showing an example of a power system including an inverter-type power supply according to an embodiment of the present invention; [Figure 3] 1 is a diagram illustrating a configuration example of an inertia estimation device for a power system according to an embodiment of the present invention. [Figure 4] FIG. 2 is a diagram illustrating an example of data stored in a system model database according to an embodiment of the present invention. [Figure 5] FIG. 4 is a diagram showing an example of data stored in an inverter-type power supply database according to an embodiment of the present invention. [Figure 6] FIG. 4 is a diagram illustrating an example of data stored in an inertia estimate database according to an embodiment of the present invention. [Figure 7] FIG. 4 is a diagram showing an example of data stored in a stability index database according to an embodiment of the present invention. [Figure 8] 1 is a block diagram showing an example of the configuration of a processing function of an inertia estimation device for a power system according to an embodiment of the present invention; [Figure 9] 3 is a flowchart showing an example of a processing algorithm of a method for estimating inertia of a power system according to an embodiment of the present invention. [Figure 10] 10 is a flowchart illustrating an example of a processing algorithm for stability calculation according to an embodiment of the present invention. [Figure 11] 1 is a diagram illustrating an example of an inverter-type power supply having a simulated inertia control function according to an embodiment of the present invention; [Figure 12] 1 is a diagram illustrating an example of an active power output of an inverter-type power supply according to an embodiment of the present invention and a voltage phase of an AC system to which the inverter-type power supply is connected. [Figure 13] FIG. 10 is a diagram illustrating an example of a change in power change amount relative to a phase change amount of a subsystem according to an embodiment of the present invention. [Figure 14] FIG. 10 is a diagram illustrating an example of a change in system frequency when a generator is disconnected from a subsystem according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In this specification and drawings, components having substantially the same functions or configurations are designated by the same reference numerals, and redundant explanations will be omitted. Note that the following is merely an example of the present invention, and the specific content below is not intended to limit the invention itself.

[0020] [One embodiment] The inertia estimation device according to one embodiment described below can be used as a monitoring device, frequency control device, or simulation analysis device for maintaining frequency stability in a power system interconnected with distributed power sources including power converters such as renewable energy power generation. It can also be used as a stabilization measure decision device (frequency maintenance device) used online for anticipated faults. It can also be used as a system equipment design support system for considering the expansion of renewable energy power generation and power storage facilities, and the reinforcement of system equipment to deal with the shutdown of rotary power generation facilities such as thermal power generators. It can also be used as a calculation support system for system stabilization incentives for providing inertia control to inverter-type power sources.

[0021] First, an example of a service provided by the inertial force service providing system 601 will be described with reference to FIG. FIG. 1 is a diagram showing an example of a service that utilizes the inertia estimation device 10 according to this embodiment. FIG. 1 shows an example of an information processing system in which an inertial force service providing system 601 includes a power system inertia estimation device 10 that estimates the inertia of a power system, and provides information about the power system to external businesses. In the following description, the power system inertia estimation device 10 may be abbreviated as "inertia estimation device 10."

[0022] The inertia estimation device 10 estimates the inertia of a power system. The inertia estimated by the inertia estimation device 10 includes the inertia amount, inertial force, etc. of the power system. An inertia force service provider provides information on inertial force to external businesses based on the inertia estimated by the inertia estimation device 10, thereby providing a service (called an inertia force service) that utilizes the value of inertia control. The inertia force service provision system 601 is a system managed and operated by the inertia force service provider. The inertia force service provision system 601 is an example of an aggregator that utilizes the inertia estimation device 10 to provide businesses with services based on the inertia amount of a subsystem estimated by the inertia estimation device 10.

[0023] The inertial force service providing system 601 manages and operates the inertia estimation device 10 installed in the control room of the power system, as well as the information acquisition unit 201, the calculation unit 202, and the information provision unit 203. The inertia estimation device 10, the information acquisition unit 201, the calculation unit 202, and the information provision unit 203 may be installed in the control room, or may be installed in another location as long as they are connected to the control room via a network. A detailed configuration example and operation example of the inertia estimation device 10 will be described later.

[0024] The information acquisition unit 201 acquires information about the power system from external businesses. Examples of the external businesses include an inverter-type power supply operator 602, a power system operator 603, and an inertial force trading market 604.

[0025] The calculation unit 202 performs predetermined calculations based on the information acquired by the information acquisition unit 201. For example, the calculation unit 202 has a function of determining a control incentive, an inertia control amount, a system stabilization control amount, and an inertia control bid amount.

[0026] The information providing unit 203 provides the calculation result to an external business operator. For example, the information providing unit 203 provides information such as the control incentive or compensation, which is the calculation result, to an inverter type power supply operator 602, a power system operator 603, and an inertial force trading market 604.

[0027] The information exchanged between the inertial force service providing system 601 and the inverter type power supply operator 602, the power system operator 603, and the inertial force trading market 604 will be described in order.

[0028] When the external business is an inverter-type power supply operator 602, the information acquisition unit 201 collects operation and control information of the inverter-type power supply, such as the amount of inertia control, from the inverter-type power supply operator 602, which enables simulated inertia control. Then, the calculation unit 202 calculates a control incentive commensurate with the contribution of the inverter to frequency stabilization of the subsystem to which the inverter is connected and the inverter inertia control effect, based on the estimated inertia value estimated by the inertia estimation device 10. The information provision unit 203 provides the calculated control incentive to the inverter-type power supply operator 602 as compensation.

[0029] When the external business operator is a power system operator 603, the information providing unit 203 provides the power system operator 603 with information on the amount of inertia expected by inertia control of the power system based on the estimated inertia value estimated by the inertia estimation device 10, information on system stabilization control when a disturbance actually occurs, and operation information of the power system. Meanwhile, the information acquiring unit 201 acquires a control incentive from the power system operator 603 as compensation commensurate with preparations in a control mode for generating inertia and the amount of control when a disturbance occurs.

[0030] When the external business operator is the inertia force trading market 604, the information providing unit 203 provides information regarding bidding for inertia force control to the inertia force trading market 604 based on the inertia estimated value estimated by the inertia estimation device 10. For example, on the other hand, the information acquiring unit 201 acquires the price, which is the bidding result for inertia force control, from the inertia force trading market 604.

[0031] In this way, a service relationship is established between inertial force service providing system 601 and each business operator. This service relationship enables inertial force service providing system 601 to exert the inertial force of various inverter type power supplies, making it possible to efficiently exert inertial force from a wide variety of inverter type power supplies.

[0032] Next, an example in which the simulated inertia of an inverter-type power supply GI changes during a grid fault will be explained using Figure 2.

[0033] Figure 2 is a diagram showing an example of a power system including inverter-type power sources GI1, GI2, and GI3. The power system shown in Figure 2 is composed of a node (bus) N, a transmission line L connecting multiple nodes (buses) N, a load Ld, a transformer Tr, a rotating machine-type power source, and the like. Note that the numbers in boxes near the node (bus) N indicate node numbers set for convenience. In the following explanation, when there is no need to distinguish between the inverter-type power sources GI1, GI2, and GI3, they will be referred to as inverter-type power sources GI.

[0034] Figure 2 shows a main grid A1 and a regional grid A2. The regional grid A2 represents a partial grid of the power grid that includes an inverter-type power source GI. The partial grid represents a grid that is connected to the transmission grid. This partial grid includes an inverter-type power source with a simulated inertia function that adjusts electrical output in response to fluctuations in the power grid. The ranges of the main grid A1 and the regional grid A2 are set in advance by the grid operator based on the voltage class and the placement of measuring equipment SE.

[0035] Note that many of the inverter-type power supplies GI are installed in local grids. For this reason, it is advisable to set the local grid A2 as a region including the entire lower-level local grid (for example, a transmission and distribution grid of 66 kV, 77 kV, or less) for each substation.

[0036] In this embodiment, the inverter-type power supply GI is a general term for equipment that connects electrical output to a power grid via an inverter. Photovoltaic power generation, wind power generation, and power storage equipment fall under the inverter-type power supply GI. On the other hand, equipment that generates power using a rotating machine such as a synchronous generator is referred to as a generator G to distinguish it from the inverter-type power supply GI.

[0037] In such a system, if a system fault occurs, such as the tripping of generator G2, generator G1 will slow down (reduced rotation speed), and the frequency will drop as it slows down. If this frequency drop occurs at a speed exceeding a certain value, or if it drops by more than a certain value, generator G1 will stop again (trip), or a protective function will be activated to stop demand (load shedding) in order to maintain the frequency.

[0038] The magnitude of the power system frequency fluctuations caused by these factors varies depending on the total inertia of the system, which is the sum of the inertia of the generator G and the simulated inertia of the inverter-type power source GI. The amount of load shedding required to maintain frequency must also be determined according to the total inertia of the system, so it is important to estimate and understand the system inertia.

[0039] However, in reality, there are many relatively small inverter-type power supply GIs that are distributed. Furthermore, whether or not an inverter-type power supply GI operates using simulated inertia control depends on the control mode. For this reason, it is not easy to accurately grasp the inertia of an inverter-type power supply GI. While it is possible to actually generate a large disturbance, such as a generator tripping, to estimate the inertia of the entire system, this should be avoided from the perspective of stable system operation and supply reliability.

[0040] Therefore, it is effective to estimate the inertia of each subsystem using small disturbances that can occur on a daily basis during system operation, and then aggregate these to grasp the inertia of the entire system. Small disturbances can be generated in a simulation by an operator operating the inertia estimation device 10. Small disturbances can also be generated in an actual system. For example, turning on and off a phase modifying device, or opening and closing one of two system circuits (operating a switch or circuit breaker), is one of the operations permitted in system operation.

[0041] The monitoring and control system 101 has a function of monitoring the operation of the main system A1 and the local system A2, and for example, SCADA / EMS is used. The SCADA (Supervisory Control And Data Acquisition) monitors power changes in each system from a remote location. The EMS (Energy Management System) controls the operation of each device by outputting operation commands to devices installed in each system. The power system inertia estimation device 10 is connected to the monitoring and control system 101. A detailed example of the internal configuration and operation of the inertia estimation device 10 will be described later.

[0042] In response to an instruction from the inertia estimation device 10, the monitoring and control system 101 generates, for example, disturbances (1) to (3) in each system. Disturbance (1) is the opening or closing (off or on) of a line switch P1. Disturbance (2) is the on / off of a phase modifying device P2 such as a capacitor. Disturbance (3) is a loop closing (closing of switch P3) in the radial system. In the following description, the disturbances (1) to (3) may be collectively referred to as a small disturbance. Note that the opening or closing (turning off or on) of the switch P4 may also occur as a disturbance.

[0043] In the figure, the communication network is represented by dashed lines connecting the monitoring and control system 101 and each device. Small disturbances are generated by operations based on operation commands sent from the monitoring and control system 101 via the communication network. The operation content and occurrence timing are communicated to the power system inertia estimation device 10. The monitoring and control system 101 may be system-linked with the power system inertia estimation device 10, or may be linked as part of a service provided by an inertial force service providing system 601, which will be described later.

[0044] When the inertia estimation device 10 instructs the monitoring and control system 101 to generate a small disturbance in order to estimate the inertia of the subsystem, the monitoring and control system 101 outputs an operation command to generate the disturbance via this communication network.

[0045] The inertia estimation device 10 grasps the voltage phase change in the regional system A2 before and after the occurrence of a small disturbance in each system by simulation or the like. Furthermore, the power change in the regional system A2 before and after the occurrence of the small disturbance can also be grasped by actually measuring it using a measurement device SE shown as a measurement point in the figure. For example, when the measurement device SE measures the voltage phase change and power change before and after the disturbance, the monitoring and control system 101 acquires the measurement information. The information acquired by the monitoring and control system 101 is sent to the inertia estimation device 10. By grasping the voltage phase change and power change before and after the occurrence of the small disturbance, the inertia estimation device 10 can estimate the inertia in the regional system A2.

[0046] Note that an inertial force service providing system 601 separate from the operator that operates and manages monitoring and control system 101 may perform an operation to instruct monitoring and control system 101 to generate a disturbance.

[0047] FIG. 3 is a diagram showing an example of the configuration of the power system inertia estimation device 10 according to this embodiment.

[0048] The power system inertia estimation device 10 is composed of a computer system. The inertia estimation device 10 includes a display device 11, an input unit 12 such as a keyboard or a mouse, a computer 13, a communication unit 14, a RAM (Random Access Memory) 15, and various databases DB, all of which are connected to a bus line 30. The computer system includes the various databases DB, which are a system model database DB1, an inverter-type power supply database DB2, an inertia estimate value database DB3, a stability index database DB4, and a program database DB5.

[0049] Here, the computer 13 executes a calculation program to specify image data to be displayed, and searches for data in various databases. The communication unit 14 acquires information acquired by the monitoring and control system 101 shown in FIG. 2, and stores the information in each database.

[0050] The RAM 15 is a memory that temporarily stores system model data used by the computer 13 for simulation, inverter-type power supply data such as inertia control characteristics and installation points, data such as the amount of inertia and power control amount generated in each area of ​​the system, and frequency control data such as the amount of control of the generator and load in response to frequency changes. Based on this data stored in the RAM 15, the computer 13 generates necessary image data and displays the image on the display screen of the display device 11.

[0051] The system model database DB1 stores data on the equipment that constitutes the power system, such as the line L (resistance, reactance, capacitance to earth) and the generator G (capacity, transient reactance, etc.), including the system configuration and system constants. Using this data makes it possible to calculate the power flow, state estimation, and frequency fluctuation of the power system, and to grasp changes in the voltage phase of each node due to disturbances that occur in the subsystem.

[0052] The inverter type power supply database DB2 stores, for example, the installation node N of the inverter type power supply GI1, etc., the control configuration and control parameters, and data on inertia simulation characteristics (inverter capacity, upper limit of output, presence or absence of inertia simulation, etc.), such as the grounding point and upper limit of capacity. From this information and information such as the above-mentioned power flow calculation results, the behavior of the inverter type power supply GI1, etc. before and after the occurrence of a small system disturbance (the amount of change in output power in response to a change in voltage phase or frequency, and the inertia constant) is estimated.

[0053] The inertia estimate database DB3 stores at least one inertia estimate, which is the inertia of the local system (e.g., instantaneous inertia), phase change (Δθ), or power change (ΔP). As shown in FIG. 6 (described later), the sensitivity ΔP / Δθ, which is a combination of the phase change (Δθ) and power change (ΔP), may also be stored as the inertia estimate. The inertia estimate database DB3 also stores data such as the total inertia of the local system A2 and the inertia of inverter-type power sources connected to each node. The inertia estimate database DB3 also stores data such as the inertia of the feeder and the power change sensitivity to voltage phase changes. The inertia estimate database DB3 also stores a sensitivity index, which indicates the degree of power change that the inverter-type power source GI of the local system A2 generates in response to a voltage phase change.

[0054] The stability index database DB4 stores a stability determination index for determining whether the inertia of a system including an inverter-type power supply can maintain frequency stability of the system, calculated using an algorithm shown in Fig. 9 (to be described later). The stability index database DB4 also stores data on generator and load control amounts or control correction amounts in response to frequency changes, in order to keep the frequency changes within a specified range.

[0055] The program database DB5 stores the following calculation programs: a power flow calculation program PR1, a state estimation calculation program PR2, a frequency fluctuation calculation program PR3, and a transient stability calculation program PR4. These programs are read into the computer 13 as needed, and calculations are performed.

[0056] Next, an example of the configuration of each database will be described with reference to FIGS.

[0057] Fig. 4 is a diagram showing an example of data stored in the system model database DB1, showing the line connection configuration and line constants of the system.

[0058] The system model database DB1 shown in the upper part of Fig. 4 shows a part of a data set that visualizes a system. Therefore, the system model database DB1 shown in Fig. 4 has the following items: line No., node, R, X, Y / 2, tap, and number of circuits.

[0059] The From node item indicates the start node of each line, and the To node indicates the end node. A line is represented by a pair of a start node and an end node. The R item indicates the resistance of the line, the X item indicates the reactance of the line, and Y / 2 indicates the ground admittance constant of the line. In addition, the tap item indicates the transformation ratio when the line is a transformer, and the number of lines item indicates the number of lines in a parallel line.

[0060] The node table T1 shown in the lower part of Figure 4 indicates information such as the capacity of the generators and loads connected to the nodes. The node table DB11 is linked to the node item in the system model database DB1. The node table DB11 has the following items: Node No., Node, Pg (MW), Qg (Mvar), Capacity (MVA), PI (MW), and QL (Mvar). The same values ​​are stored in the Node No. item and the Node item. The Pg item and the Qg item respectively store the active power Pg and reactive power Qg of the generator at the node. The capacity item stores the capacity of the load. The Pg item and the Qg item respectively store the active power PI and reactive power QI of the inverter-type power source GI at the node.

[0061] 5 is a diagram showing an example of data stored in the inverter-type power supply database DB2. The inverter-type power supply database DB2 has the following items: No., name, installation node, upper limit of power output (MW), and capacity (MVA).

[0062] The No. item stores an identification number assigned to the inverter type power supply GI. The name item stores the name of the inverter type power supply GI. The installation node item stores the number of the installation node where the inverter type power supply GI is installed.

[0063] The upper limit of power output is stored as the upper limit of power that can be output by the inverter type power supply GI. The capacity item stores the output capacity that contributes to the inertia of the inverter-type power supply GI.

[0064] 6 is a diagram showing an example of data stored in the inertia estimation value database DB3. It stores an index indicating the amount of inertia of the subsystem estimated by the inertia estimation device 10, and sensitivity information (such as the sensitivity of power change to voltage phase change). For this reason, the inertia estimation value database DB3 has the following items: No., subsystem name, subsystem connection point, measurement point, sensitivity ΔP / Δθ, and instantaneous inertia (MWs / s).

[0065] The No. item stores an identification number assigned to the subsystem. The item "subsystem name" stores the name of the subsystem. The item "system connection point" stores the identification number of the system connection point to which the subsystem is connected. The measurement point item stores the identification number of the measurement point. Note that the identification number of the grid connection point and the identification number of the measurement point are the same. The item Sensitivity ΔP / Δθ stores a value that expresses the sensitivity of the power change to the voltage phase change. The item of instantaneous inertia stores the instantaneous inertia of the subsystem.

[0066] The inertia estimated value database DB3 also stores data such as connection points of the main system to which the subsystem is connected, and measurement points at which power changes in the subsystem are measured.

[0067] Fig. 7 is a diagram showing an example of data stored in the stability index database DB4. The stability index database DB4 shows the relationship between the effect of inertial force of a subsystem on a contingency fault and the evaluation index RoCoF. A contingency fault represents the situation when a disturbance occurs. For this reason, the stability index database DB4 has the following items: No., contingency type, power generation change (MW), power change due to inertia (MW), RoCoF (Hz / sec), and stability judgment.

[0068] The No. item stores an identification number assigned to the contingency type. The item of contingency type stores the name of the contingency type. The item of power generation change amount stores the amount of change in power generation that occurs due to a contingency failure. The item for power change due to inertia stores the amount of power change in a subsystem due to inertia when a change indicated by the amount of power generation change occurs due to a contingency fault. For this reason, the item for power change due to inertia further includes items for subsystem 1, subsystem 2, subsystem 3, etc., and also includes an item for storing the total value of the power change in each subsystem. The RoCoF item stores the calculated RoCoF value. The stability determination item stores the result of stability determination by the frequency fluctuation index calculation unit 36 ​​shown in FIG. 8, which will be described later, as OK or NG.

[0069] The table in the stability index database DB4 lists the results of simulations performed for various contingency faults. For example, No. 1 shows the case where generator #01 trips as a contingency fault. Here, frequency stability is determined as stable if the rate of change of frequency (RoCoF) is less than 0.2, and unstable if it is 0.2 or greater.

[0070] The results of the transient stability analysis show that when the power generation change (dropout) is 1000MW, a power change of 100MW occurs in subsystem 1, 50MW in subsystem 2, and 40MW in subsystem 3, for a total change of 800MW, with a RoCoF of 0.02Hz / sec. In this case, the rate of change of frequency (RoCoF) is less than 0.2, so frequency stability is maintained and the stability judgment is OK (stable).

[0071] On the other hand, in the case where generators #01, #02, and #03 of No. 3 are tripped, the power generation change is 8000 MW and the RoCoF is 0.25 Hz / sec. In this case, the rate of change of frequency (RoCoF) is 0.2 or more, and frequency stability is not maintained, so the stability judgment is NG (unstable).

[0072] In this way, by evaluating the frequency stability of the entire system while taking into account power fluctuations due to the inertia of the subsystem, it is possible to more accurately evaluate the frequency stability of the system, including the inertia of the inverter-type power supply GI. Furthermore, by presenting the results of this frequency stability calculation for a contingency fault to the monitor, the need for stabilization measures for a contingency fault that has resulted in a stability judgment of NG (unstable) can be considered. For example, measures such as starting up an extra generator can be taken to slightly increase the inertia of the subsystem. Here, RoCoF is used as an example evaluation index, but similar considerations can be made when the maximum frequency deviation (Nadir) is used as the evaluation index.

[0073] In this way, by understanding the impact that inertia and power changes during system disturbances have on the rate of change of frequency (RoCoF) and maximum frequency deviation (Nadir) indices and reflecting the results in frequency control, it is possible to reduce the risk of power outages, as well as reduce the excess or deficiency of power generation and load control amounts required for frequency control, thereby reducing power outages due to load shedding.In addition, because the effect of inertial supply from inverter-type power supply GI can also be calculated, it becomes possible to quantify the inertia control effect and provide incentives accordingly, which has the effect of improving frequency stability by increasing the inertia of the entire system.

[0074] FIG. 8 is a block diagram showing an example of the configuration of the processing functions of the power system inertia estimation device 10 according to this embodiment.

[0075] The power system inertia estimation device 10 includes the functional blocks of a system operation command detection unit 31, a measurement value extraction unit 32, a PQ change amount extraction unit 33, a phase change amount estimation unit 34, a subsystem inertia estimation unit 35, a frequency fluctuation index calculation unit 36, and a frequency stabilization control amount calculation unit 37. The power system inertia estimation device 10 also includes the four databases shown in Fig. 3, namely, a system model database DB1, an inverter-type power supply database DB2, an inertia estimation value database DB3, and a stability index database DB4.

[0076] The system operation command detection unit 31 detects system operation commands that can estimate the inertia of the power system. For example, in the power system shown in FIG. 2, the system operation command detection unit 31 determines disturbance operations that cause disturbances (1) to (3) in a subsystem, or detects disturbances that have occurred in the subsystem. For example, disturbance (1) occurs by opening or closing a switch or circuit breaker on one of two transmission lines. Disturbance (2) occurs by opening or closing a phase modifying device such as a capacitor or reactor in the system. Disturbance (3) occurs by closing or opening a switch in the system to form or break a loop system. Disturbance commands that cause these disturbances (1) to (3) are sent to each switch, etc. by disturbance operations in the monitoring and control system 101. These disturbance commands may be set by user input, or the user may input information about the occurrence of disturbances based on measurement information. The system operation command detection unit 31 acquires measurement values ​​from various measuring devices installed in the system, grasps these disturbances based on the measurement values, and stores the type of disturbance that has occurred and the time of occurrence.

[0077] The measurement value extractor 32 collects measured values ​​of electrical quantities in the power system. For example, the measurement value extractor 32 extracts measurement values ​​such as active power P and reactive power Q measured by sensors installed at measurement devices SE shown as measurement points in Fig. 2, and grasps these measurement values. These measurement values ​​are also called system substation information.

[0078] The PQ change amount extraction unit 33 extracts the amount of change between the amount of electricity before and after the system operation. For example, the PQ change amount extraction unit 33 analyzes the measurement values ​​extracted by the measurement value extraction unit 32 and extracts the amount of change in active power P and reactive power Q (also referred to as PQ change amount). For example, the PQ change amount extraction unit 33 determines the amount of change in active power and reactive power of the subsystem before and after the occurrence of a small disturbance based on the amount of electricity (active power P, reactive power Q) that is the measurement values ​​measured by the measurement value extraction unit 32, using the operation type and time of the system operation command detected by the system operation command detection unit 31 as the time of occurrence of the disturbance.

[0079] The phase change amount estimator 34 estimates the amount of phase change in the voltage phase of a subsystem in the power system based on the amount of change extracted by the PQ change amount extractor 33. For example, the phase change amount estimator 34 creates a system analysis model based on information in a system model database DB1 and an inverter-type power supply database DB2. Next, the phase change amount estimator 34 uses the system analysis model as input to execute a power flow calculation program PR1 and a state estimation calculation program PR2. In the phase change amount estimator 34, a power flow calculation is performed by the power flow calculation program PR1, and a state is estimated by the state estimation calculation program PR2. Based on the calculation results of each program, the phase change amount estimator 34 estimates the amount of voltage phase change in the subsystem and passes the estimated value to an inertia estimation unit 35 for the subsystem.

[0080] The subsystem inertia estimator 35 estimates the inertia of the subsystem based on the phase change estimated by the phase change estimator 34. For example, the subsystem inertia estimator 35 estimates the inertia of the subsystem based on the voltage phase change in the subsystem before and after the occurrence of a small disturbance calculated by the phase change estimator 34 and the active and reactive power changes in the subsystem before and after the occurrence of a small disturbance calculated by the PQ change extractor 33. The subsystem inertia estimator 35 then stores the estimated inertia of the subsystem in an inertia estimate database DB3 so that it can be provided to external operators. The subsystem inertia estimator 35 also passes the estimated inertia to the frequency fluctuation index calculator 36. The inertia estimate database DB3 stores the inertia of each node, area, and feeder. The subsystem inertia estimator 35 can also pass the estimated inertia value in the subsystem to the frequency stabilization control amount calculator 37 without going through the frequency fluctuation index calculator 36 .

[0081] The frequency fluctuation index calculation unit 36 ​​calculates an evaluation index of the frequency fluctuation of the power system based on the voltage phase change amount of the subsystem, the power change amount of the subsystem, or the inertia sensitivity coefficient. For example, the frequency fluctuation index calculation unit 36 ​​aggregates the inertia amounts estimated for each subsystem during a system fault and estimates the inertia amount of the entire target system. Next, the frequency fluctuation index calculation unit 36 ​​calculates an evaluation index of the system frequency fluctuation, such as the rate of change of frequency (RoCoF) or the maximum frequency deviation (Nadir), based on the estimated inertia amounts. Then, the frequency fluctuation index calculation unit 36 ​​determines the system frequency stability with respect to the amount of power source loss based on the evaluation index of the system frequency fluctuation. The frequency fluctuation index calculation unit 36 ​​stores the determination result of the system frequency stability as a stability determination index in the stability index database DB4. The determination result of the system frequency stability is also passed to the frequency stabilization control amount calculation unit 37.

[0082] Based on the determination result of the grid frequency stability, the frequency stabilization control amount calculation unit 37 calculates, as the frequency stabilization control amount, the amount of power shedding (power control amount) and the amount of load shedding (load control amount) required for the frequency and frequency fluctuation index to fall within a specified range.The frequency stabilization control amount calculation unit 37 then stores the frequency stabilization control amount, which is the calculation result, in the stability index database DB4.The frequency stabilization control amount may be provided to the external business operator shown in FIG. 1.

[0083] Next, a processing flow showing an example of a processing algorithm performed by the power system inertia estimation device 10 will be described with reference to FIG. 9 is a flowchart showing an example of a processing algorithm for the power system inertia estimation method. The power system inertia estimation method is part of an information processing method performed by the inertial force service providing system 601. The processing flow for the power system inertia estimation method corresponds to the processing of the system operation command detection unit 31, measurement value extraction unit 32, PQ change amount extraction unit 33, phase change amount estimator 34, subsystem inertia estimator 35, frequency fluctuation index calculation unit 36, and frequency stabilization control amount calculation unit 37 shown in FIG.

[0084] First, an operator sets system operation command information that becomes a disturbance in the system operation command detection unit 31. After that, the system operation command detection unit 31 detects a disturbance caused by system operation (S1). The system operation command detection unit 31 grasps, for example, information on whether a switch is ON or OFF as system operation information that becomes a disturbance.

[0085] The setting of the system operation command information is an operation performed when an operator decides to perform a system operation and sets predetermined conditions. Alternatively, the setting of the system operation command information may be an operation performed when an operator grasps the results of the system operation from measurement values ​​or changes in the status of a monitoring device. As described above, the system operation information includes, for example, the type of operation, such as (1) opening or closing a switch or circuit breaker on one of two transmission lines, (2) closing or opening a phase modifying device such as a capacitor or reactor in the system, or (3) creating or breaking a loop system by closing or opening or closing a switch in the system, the location and equipment (such as a circuit breaker, switch, or SC switch) in the system, and the time of the system operation. Note that the system operation command detection unit 31 may also grasp operations caused by factors other than the above operations (1) to (3), for example, information on the ON / OFF of equipment other than the device that generates the disturbance.

[0086] Next, the measurement value extractor 32 extracts the subsystem's active power P measured by the measuring device SE or sensor installed at the measurement point shown in FIG. 2 as a measurement value. The PQ change extractor 33 extracts the active power change ΔP before and after the disturbance based on the time information at the time of disturbance occurrence determined in processing step S1 and the subsystem's active power P extracted by the measurement value extractor 32 (S2). Specifically, the PQ change extractor 33 calculates the difference between the maximum and minimum values ​​of active power P within a short period (e.g., 0.2 seconds) before and after the disturbance occurrence. For this purpose, the PQ change extractor 33 calculates a range of a certain time before and after the disturbance detection time. To remove noise, the PQ change extractor 33 extracts the active power P that exceeds a certain threshold. The measurement value extractor 32 extracts the subsystem's active power P as a measurement value, and can also extract the subsystem's reactive power Q as a measurement value.

[0087] Next, the phase change estimation unit 34 estimates the phase change of each node (especially the inverter) of the subsystem based on the value of the active power P extracted by the measurement value extraction unit 32 (S3). The phase change estimation unit 34 estimates the phase change of the nodes connected to the inverters, particularly the nodes numbered 11, 12, and 13 in FIG. 2. To this end, the phase change estimation unit 34 calculates or estimates the phase change of each node of the subsystem that will occur based on the system operation information set in processing step S1. This calculation utilizes power flow calculation, circuit calculation (transient stability calculation), state estimation calculation, transient stability calculation, and the like. The phase change estimation unit 34 creates a system analysis model of the subsystem by state estimation using information from the system model database DB1 and measurement information, and calculates the voltage phase change Δθ of the subsystem before and after the system operation by simulation.

[0088] Next, the subsystem inertia estimator 35 calculates the inertia sensitivity coefficient Km=ΔP / Δθ (S4). The inertia sensitivity coefficient Km is an index that represents the relationship between the amount of active power variation ΔP that changes due to the voltage phase change Δθ of the subsystem. The subsystem inertia estimator 35 stores the inertia sensitivity coefficient Km (=ΔP / Δθ) and a combination of the amount of active power variation ΔP of the measured value relative to the phase change Δθ of a node of the estimated subsystem (for example, the node closest to the main system).

[0089] Next, the subsystem inertia estimator 35 estimates the inertia of the subsystem (S5). The subsystem inertia estimator 35 calculates the inertia Ma (MW·s) of the regional subsystem A2 based on the inertia force coefficient Km and a table showing the relationship between the inertia constant and the inertia M (MW·s), which has been calculated in advance by simulation or the like. The subsystem inertia estimator 35 stores the inertia Ma of the regional subsystem A2 as an inertia estimation and monitoring index. Here, s (seconds) is an arbitrarily determined parameter, but setting it to, for example, 1 to 2 seconds can serve as an effective index for understanding the impact on RoCoF.

[0090] The RoCoF, which represents the rate of frequency change, can be calculated using equation (2), where Δf is the frequency deviation from the reference frequency, and Δt is the time during which the frequency drop occurs.

[0091] RoCoF=△f / △t (2)

[0092] Next, the frequency fluctuation index calculation unit 36 ​​calculates the frequency stability for a contingency fault (S6). By calculating the frequency stability, the frequency fluctuation index calculation unit 36 ​​aggregates the inertia estimated for each subsystem and estimates the inertia of the entire target system. Furthermore, the frequency fluctuation index calculation unit 36 ​​calculates an evaluation index for the system's frequency fluctuation based on the estimated inertia, and calculates a frequency stability judgment result for the amount of power supply loss. It calculates indices such as RoCoF for conditions such as a contingency, and judges whether or not measures are necessary for an increase in inertia or a decrease in the proportion of inverter-type power supplies. The judgment result on whether or not measures are necessary is stored, for example, in the stability judgment section of the stability index database DB4 in FIG. 7.

[0093] Next, the frequency fluctuation index calculation unit 36 ​​uses the display function of the monitoring system or the like to display an alarm indicating whether or not countermeasures are required to the monitor based on the result of the determination of whether or not countermeasures are required in processing step S6 (S7). By displaying the alarm, the monitor can determine the inertia surplus or deficiency status of the system and start considering necessary countermeasures.

[0094] Next, the frequency stabilization control amount calculation unit 37 calculates the control amount required for frequency stabilization based on the result of processing step S7 (S8), and ends this processing. The control object for which the control amount is calculated is expected to be, for example, load shedding or emergency discharge control of a power storage facility. Specifically, the frequency stabilization control amount calculation unit 37 repeatedly calculates the frequency stability similar to the calculation performed by the frequency fluctuation index calculation unit 36 ​​in processing step S6, changing the control amount, and finds the required control amount.

[0095] Next, a processing flow showing an example of the processing algorithm of processing step S6 in FIG. 9 will be described with reference to FIG. 10 is a flowchart showing an example of a processing algorithm for stability calculation, which is performed by the frequency fluctuation index calculation unit 36.

[0096] First, the frequency fluctuation index calculation unit 36 ​​sets disturbance conditions such as a generator tripping (S11). A generator tripping is an example of a contingency fault.

[0097] Next, the frequency fluctuation index calculation unit 36 ​​calculates the phase change Δθ of the subsystem when the disturbance occurs (S12). The process performed in process step S12 is similar to the calculation by the phase change amount estimation unit 34 in process step S3 of FIG. 9.

[0098] Specifically, the frequency fluctuation index calculation unit 36 ​​calculates the change in voltage phase of the subsystem before and after the occurrence of a disturbance through simulation using power flow calculations and transient stability calculations. Most regional systems have a generally radial system configuration, in which case the voltage phase changes are approximately similar within the subsystem. Therefore, the phase change Δθ of the subsystem may be the voltage phase change of a representative node. For example, the value of the node closest to the main system or the average value of the nodes within the subsystem may be used as the phase change of the subsystem.

[0099] Next, the frequency fluctuation index calculation unit 36 ​​calculates the amount of power change ΔP in the subsystem (S13). The process performed in processing step S13 is the same as the calculation by the PQ variation extraction unit 33 in processing step S2 in FIG.

[0100] For example, the frequency fluctuation index calculation unit 36 ​​estimates the power change amount ΔP in the subsystem by referring to the calculated phase change value Δθ occurring in the subsystem and a pre-calculated sensitivity table (a table of correspondence between ΔP and Δθ). This becomes the power change amount in the subsystem before and after the occurrence of the set disturbance, and becomes the action (influence or effect) of reducing (increasing) the frequency change due to the inertia of the subsystem. The frequency fluctuation index calculation unit 36 ​​calculates this for each subsystem.

[0101] Next, the frequency fluctuation index calculation unit 36 ​​calculates the frequency change after a disturbance occurs in the subsystem and calculates the RoCoF (S14). In this process, the frequency fluctuation index calculation unit 36 ​​creates an analytical model of the rotary generator in the subsystem according to the current situation. Thereafter, the frequency fluctuation index calculation unit 36 ​​generates the change in ΔP of the subsystem calculated in processing step S13 in the subsystem model simultaneously with the occurrence of a contingency fault such as a generator tripping, and performs frequency fluctuation analysis under this condition. The frequency fluctuation index calculation unit 36 ​​may perform the frequency fluctuation analysis using, for example, transient stability analysis, or a frequency analysis model (such as the AGC30 model of the Institute of Electrical Engineers). The frequency fluctuation index calculation unit 36 ​​changes the contingency fault (such as the amount of generator tripping) and repeats processing steps S11 to S14 to calculate the frequency fluctuation and RoCoF for the contingency fault being considered.

[0102] Next, the frequency fluctuation index calculation unit 36 ​​compiles the results of the frequency fluctuation analysis and calculates the frequency stability (S15). Through this calculation, the frequency fluctuation index calculation unit 36 ​​determines the range of fault conditions (amount of generator tripping) under which frequency stability is maintained. The frequency fluctuation index calculation unit 36 ​​determines whether or not countermeasures are necessary based on the determined range of fault conditions. For example, if the amount of generator tripping exceeds the range of fault conditions, the frequency fluctuation index calculation unit 36 ​​determines that countermeasures are necessary. The determination result on whether or not countermeasures are necessary is returned to processing step S7 in FIG. 9.

[0103] FIG. 11 is a diagram showing an example of an inverter type power supply GI having a simulated inertia control function.

[0104] The inverter-type power supply GI generates inertia when the phase changes. The inverter 40 included in this inverter-type power supply GI is connected to an AC system bus 42 via a transformer 41. A PWM circuit 43 drives the inverter 40. Therefore, the voltage Vinv and phase θinv of the inverter 40 are controlled by the PWM circuit 43 passing a PWM gate pulse to the inverter 40 based on the output of a control transfer function.

[0105] The control transfer function is controlled based on the deviation between the measured values ​​of the active power output P and reactive power output Q of the inverter 40 and their respective command values ​​Pref and Qref. In the active power control, the deviation ΔP between the measured active power value and the active power command value is converted into a phase correction amount Δθ. In this control, inertia control is achieved by setting a phase angle droop based on the power difference, not the frequency. The control transfer function Kpsc, which converts the deviation ΔP into the phase correction amount Δθ, is expressed by equation (3). Kpθ in equation (3) corresponds to the control gain. The phase θ, which is the sum of the phase correction amount Δθ and the reference phase θref, is input to the PWM circuit 43. Like a synchronous machine, the inverter-type power supply GI achieves synchronization with the grid through transient power measurement values ​​and can generate simulated inertia by setting the control gain Kpθ.

[0106]

number

[0107] In reactive power control, the deviation ΔQ between the reactive power measurement value Q and the reactive power command value Qref is converted into a voltage correction amount ΔV by a control transfer function KQv. The voltage Vdref obtained by adding the voltage correction amount ΔV and the voltage command value Vnom is input to the PWM circuit 43.

[0108] Next, the behavior of the inverter-type power supply GI when the system phase changes will be described. The active power output P of the inverter-type power supply GI is expressed as in equation (4) using the voltage Vinv and phase θinv of the inverter 40, the voltage Vac and phase θac of the AC system bus 42, and the reactance Xtr of the transformer 41.

[0109]

number

[0110] Assuming that the voltage phase θac of the AC system bus 42 changes due to a disturbance such as system operation, the inverter output P will also change in accordance with the change in the voltage phase θac. The change in the active power output P is reflected in the input of the control transfer function, and control is performed to follow the active power command value Pref, but the following can be made gentler by setting the control gain Kpθ of the control transfer function Kpsc. As a result, for a while after the disturbance, the inverter 40 will output power that differs from the active power command value Pref, which acts equivalent to the inertia of a synchronous machine.

[0111] Next, an example of the behavior of the inverter type power supply GI when a disturbance occurs will be described with reference to FIG. FIG. 12 is a diagram showing an example of the active power output P of the inverter type power supply GI and the voltage phase of the AC system to which the inverter type power supply GI is connected.

[0112] The upper part of Fig. 12 shows changes in the active power output P of the inverter-type power supply GI. The horizontal axis of this diagram represents time (seconds), and the vertical axis represents the active power output P (GW).

[0113] The active power output P is 0.5 GW from 0.9 seconds to 1 second. At 1 second, a disturbance occurs due to the tripping of a generator or the ON / OFF of a subsystem, causing the active power output P to change. Therefore, the inertia estimation device 10 determines the active power change amount ΔP based on the change in the active power output P. After the disturbance occurs, the active power output P gradually decreases as the inertia of the subsystem decreases.

[0114] The lower part of Fig. 12 shows changes in the voltage phase of the AC system to which the inverter type power supply GI (inverter type power supply GI3 shown in Fig. 2) is connected. The horizontal axis of this diagram represents time (seconds), and the vertical axis represents the voltage phase θ (°) of the AC system.

[0115] The voltage phase θ before the disturbance occurs is -65°. When the disturbance occurs at 1 second, a change in the voltage phase θ occurs, so the inertia estimation device 10 estimates the phase change Δθ. After the disturbance occurs, the voltage phase θ gradually decreases as the inertia of the subsystem decreases.

[0116] As shown in Figure 12, when a disturbance occurs and the voltage phase θ changes by an amount equal to the voltage phase change △θ, the power output of the inverter-type power supply GI also changes simultaneously by an amount equal to the change in active power △P. After that, the active power of the inverter-type power supply GI gradually decreases and returns to near the output level before the disturbance. The increase in active power during the period from when the disturbance occurs until the active power returns to near the output level before the disturbance plays the role of a pseudo-inertial force in the subsystem.

[0117] In this way, the inertia estimation device 10 is thought to be able to estimate the inertia of the inverter-type power supply GI by grasping the magnitude of the active power change ΔP of the inverter-type power supply GI relative to the phase change Δθ of the subsystem and grasping the relationship between the two.

[0118] Next, the inertia force sensitivity coefficient Km (=ΔP / Δθ) of the regional system A2 will be described with reference to FIG. Fig. 13 is a diagram showing an example of a change in power change ΔP relative to a phase change Δθ of the subsystem. The horizontal axis of Fig. 13 represents the phase change Δθ of the subsystem, and the vertical axis represents the active power change ΔP of the regional system A2.

[0119] The phase change amount △θ is a value calculated by system analysis such as simulation (power flow calculation, transient stability calculation, etc.) of the phase change before and after the occurrence of an expected disturbance. The active power change amount △P is a value determined by measurement values ​​before and after the occurrence of a disturbance or by simulation analysis. By plotting these relationships for different types of disturbances, the inertia force sensitivity coefficient Km (= △P / △θ) can be estimated. The slope of the straight line that is a linear approximation of the plot shown in the figure corresponds to the inertia force sensitivity coefficient Km.

[0120] Next, we will explain the procedure for stabilizing frequency using the inertial force of the subsystem thus determined. First, we will explain RoCoF and Nadir, which are indices used to consider frequency stability.

[0121] Fig. 14 is a diagram showing an example of a change in the system frequency when a generator is disconnected from a partial system. Here, the change in the system frequency when the generator is stopped by a certain amount at time 0 seconds is shown.

[0122] Immediately after a generator stops, the system frequency (Hz) drops sharply. The rate of change of the system frequency drop over time is defined by the index of rate of change of frequency (RoCoF). In addition, the value at which the frequency drops the most is defined by the index of maximum frequency deviation (Nadir) as the maximum deviation from the rated frequency.

[0123] Nadir can be calculated using equation (5), where fn is the reference frequency and fb is the frequency at the maximum drop. Nadir=fn-fb (5)

[0124] In Figure 14, graph (a) shows the case where the inertia of the subsystem is large, and graph (b) shows the case where the inertia of the subsystem is small, as a solid line, and graph (b) shows the case where the inertia of the subsystem is small, as a dashed line. Graph (b), which has small inertia, has a steeper slope of the rate of change of frequency (RoCoF) and a larger value of the maximum frequency deviation (Nadir) than graph (a).

[0125] In the event of a grid fault, it is necessary to maintain a supply-demand balance so that the rate of change of frequency and maximum frequency deviation are below a certain level. If control of the rate of change of frequency and maximum frequency deviation fails, the area of ​​the grid outage may expand, or in some circumstances, the grid may even be completely blacked out. Therefore, it is important to understand the effect (sensitivity) of the inertia and power lost by inverter-type power sources (GI) on the indexes for the rate of change of frequency (RoCoF) and maximum frequency deviation (Nadir), and to reflect this in determining the amount of frequency control.

[0126] The inertia estimation device 10 of the inertial force service providing system 601 according to the embodiment described above grasps the inertia within a subsystem of a power system, including power generation and charging / discharging facilities connected to the system via a power converter, and provides information useful for system frequency control. The inertia estimation device 10 can estimate the inertia, including the simulated inertia of the subsystem. Therefore, the inertia estimation device 10 can accurately grasp the contribution to maintaining the system frequency. The inertia estimation device 10 can also increase the number of rotary generators shut down and the number of inverter-type generators connected to the system, and provide information useful for system stabilization. The inertia estimation device 10 can also estimate the total inertia from the measured value of the subsystem. Therefore, the inertial force service providing system 601 can provide external businesses with information about the power system, which is used to stabilize frequency control by estimating the inertia of the subsystem, thereby stabilizing the power system.

[0127] Furthermore, the inertia estimation device 10 can quantify the contribution of simulated inertia control to frequency maintenance, and can also provide incentives. This increases power generation revenue for power generation companies and provides grid stabilization benefits for grid operators.

[0128] Furthermore, the inertia estimation device 10 can estimate the inertia within a local grid without having to individually grasp the operation and control status of each inverter-type power source GI that has an inertia simulation function. This has the effect of eliminating the need to build communication equipment and information collection systems for a large number of distributed inverter-type power sources.

[0129] Furthermore, the inertia estimation device 10 can estimate inertia without causing large-scale disturbances to the system, such as simulating a power supply failure or load shedding, thereby contributing to improving the reliability of maintaining the power quality and stability of the system.

[0130] In addition to the above-described inertial force service providing system 601, the present invention can also be applied to a power system stabilization system and a power system reliability monitoring system as examples of information processing systems. In a power system stabilization system, information about the power system for stabilizing frequency control is provided to a power system monitoring and control system 101, thereby stabilizing the power system. Furthermore, by using the information about the power system for stabilizing frequency control as reliability, the monitoring and control system 101 can control the power system so that the reliability is higher than a predetermined value.

[0131] The inertia estimation device 10 can also estimate inertia from existing measurement information of the subsystem. A system calculation may be performed using the measured values ​​of active power P and reactive power Q measured in the subsystem to estimate a change in voltage phase in the subsystem. The inertia estimation device 10 can also use the estimated change in voltage phase for inertia estimation.

[0132] For example, a PMU (Phase Measurement Unit) may be installed in the power system. The PMU is a device that directly measures changes in voltage phase in a subsystem, and the measurement results are sent to the inertia estimation device 10 via a monitoring and control system 101. The inertia estimation device 10 can also estimate phase changes at system points other than the measurement points by performing system calculations using the measurement results obtained from the PMU. Furthermore, the inertia estimation device 10 can improve the accuracy of inertia estimation by measuring the phase at the PMU installation point.

[0133] Furthermore, the inertia estimation device 10 can extract measurement information when a change in the state of the system that allows inertia estimation occurs. Examples of such timing include when the change in power over time exceeds a predetermined value, when a circuit breaker is turned on or off, or when a loop is connected to the system. This allows the inertia estimation device 10 to improve the accuracy of inertia estimation and reduce the amount of estimation calculation.

[0134] The inertia estimation device 10 can also generate a change in the system status at a timing when inertia estimation is required. Examples of such a change include turning on or off a circuit breaker, turning on or off a phase modifying device in a partial system, or turning on or off a system loop. This allows the inertia estimation device 10 to improve the accuracy of inertia estimation.

[0135] Furthermore, the inertia estimation device 10 can also estimate the inertia capacity that the inverter-type power supply can generate (for example, the P change capacity when the frequency changes) by combining operation information (start / stop, output) of the simulated inertial power supply. This allows the inertia estimation device 10 to estimate the frequency maintenance capacity based on inertia.

[0136] The present invention is not limited to the above-described embodiment, and it goes without saying that various other applications and modifications are possible without departing from the gist of the present invention as set forth in the claims. For example, the above-described embodiment has described the system configuration in detail and specifically to clearly explain the present invention, and is not necessarily limited to a system including all of the described configurations. Furthermore, it is also possible to add, delete, or replace part of the configuration of this embodiment with other configurations. In addition, the control lines and information lines shown are those that are considered necessary for the explanation, and do not necessarily show all the control lines and information lines in the product. In reality, it can be assumed that almost all components are interconnected. [Explanation of symbols]

[0137] 10...Inertia estimation device, 31...System operation command detection unit, 32...Measurement value extraction unit, 33...PQ change amount extraction unit, 34...Phase change amount estimation unit, 35...Inertia estimation unit, 36...Frequency fluctuation index calculation unit, 37...Frequency stabilization control amount calculation unit, 101...Monitoring control system, 201...Information acquisition unit, 202...Calculation unit, 203...Information provision unit, 601...Inertia force service provision system, DB1...System model database, DB2...Inverter type power supply database, DB3...Inertia estimated value database, DB4...Stability index database, DB5...Program database, PR1...Power flow calculation program, PR2...State estimation calculation program, PR3...Frequency fluctuation calculation program, PR4...Transient stability calculation program

Claims

1. An information processing system that includes an inertia estimation device that estimates the inertia of a power system and provides information about the power system to an external business operator, The inertia estimation device a measurement value extracting unit that collects measured values ​​of electrical quantities of the power system; a system operation command detection unit configured to detect a system operation command for the power system that can estimate the inertia of the power system; a change amount extraction unit that extracts a change amount between an amount of electricity before the grid operation is performed and an amount of electricity after the grid operation is performed; a phase change estimation unit that estimates a phase change amount of a voltage phase of a subsystem in the power system based on the change amount; an inertia estimation unit that estimates the inertia of the subsystem based on the phase change amount; an inertia estimation value database that stores the estimated inertia values ​​of the subsystems so that the estimated inertia values ​​can be provided to the external business operator. Information processing system.

2. the subsystem includes an inverter-type power supply having a simulated inertia function that adjusts an electrical output in response to fluctuations in the power grid; The electric output is connected to the power system via the inverter type power supply. The information processing system according to claim 1 .

3. a frequency fluctuation index calculation unit that calculates an evaluation index of frequency fluctuation of the power system based on one of a voltage phase change amount of the subsystem, a power change amount of the subsystem, and an inertia force sensitivity coefficient, and determines the frequency stability of the subsystem; a frequency stabilization control amount calculation unit that calculates a frequency stabilization control amount based on the determination result of the frequency stability of the subsystem. The information processing system according to claim 2 .

4. The evaluation index of the frequency fluctuation is the frequency change rate or the maximum frequency deviation. The information processing system according to claim 3 .

5. The estimated inertia value is at least one of an inertia amount, a phase change amount, and a power change amount of the subsystem. The information processing system according to claim 4 .

6. an information acquisition unit that acquires information about the power grid from the external business; a calculation unit that performs a predetermined calculation based on the acquired information and an estimated inertia value estimated by the inertia estimation device; an information providing unit that provides the calculation result to the external business operator; The information processing system according to any one of claims 1 to 5.

7. If the external business operator is an inverter-type power source operator, the information acquisition unit acquires operation and control information of the inverter type power supply from the inverter type power supply operator, the calculation unit calculates a contribution of the inverter to frequency stabilization of the subsystem to which the inverter is connected and a control incentive commensurate with an inverter inertia control effect, based on the inertia estimated value estimated by the inertia estimation device; The information providing unit provides the control incentive as compensation. The information processing system according to claim 6 .

8. If the external business operator is a power system operator, the information providing unit provides, to the power system operator, information on an amount of inertia expected by inertia control of the power system, information on system stabilization control when a disturbance occurs, and operation information of the power system based on the estimated inertia value estimated by the inertia estimation device; The information acquisition unit acquires a control incentive from the power system operator as compensation commensurate with the amount of control when a disturbance occurs. The information processing system according to claim 6 .

9. If the external business is an inertial trading market, the information providing unit provides information regarding bidding for inertia force control to the inertia force trading market based on the inertia estimated value estimated by the inertia estimation device; The information acquisition unit acquires a price, which is a bidding result for the inertial force control, from the inertial force trading market. The information processing system according to claim 6 .

10. An information processing method for an information processing system that includes an inertia estimation device that estimates the inertia of a power grid and provides information about the power grid to an external business operator, the method comprising: collecting electrical quantity measurements of the power system; detecting a system operation command for the power system that allows estimation of inertia of the power system; extracting a change in the amount of electricity between before the grid operation is performed and after the grid operation is performed; estimating a phase change amount of a voltage phase of a subsystem in the power system based on the change amount; estimating the inertia of the subsystem based on the phase change amount; and storing the estimated inertia value of the subsystem in an inertia estimate database so that the estimated inertia value can be provided to the external operator. Information processing methods.

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