Power grid stabilization system and power grid stabilization method

Abstract

To provide a power grid stabilizing system capable of suppressing computational resources while keeping computational accuracy for evaluating a state of a power grid.SOLUTION: A power grid stabilizing system comprises: a power grid computational unit for receiving a power grid state, a power grid model, and an event case as inputs to execute one or more of a simple event computation and an event computation; and a margin setting unit for receiving a margin setting parameter as an input to compute a screening margin from a simple event computation result and an event computation result with respect to the event case targeted by the power grid computational unit. The margin setting unit computes the screening margin from results of both the simple event computation and the event computation, which suppresses possibility of erroneous screening to keep computational accuracy, and reduces grid states to be evaluated using power flow computation to suppress computational resources.SELECTED DRAWING: Figure 4

Description

Technical Field

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

Background Art

[0002] In recent years, with the increase in renewable energy power sources connected to the power system and the electrification of consumer equipment, there is concern that overloading of transmission lines, which was not conventionally assumed, may occur. And even when an overload occurs in the electrical system, a power system stabilization system (SPS: Special Protection Schemes) that can eliminate the overload by using the output of the renewable energy power source as alternative energy has attracted attention.

[0003] In a general recent power system stabilization system, the impact of changes in the power system state is calculated in advance by simulation to formulate countermeasures when an overload occurs. On the other hand, it is known that the scale of calculation of the power system simulation becomes extremely large as the scale of the power system increases. This is considered to be due to two reasons: the increase in the calculation process of the power flow state calculation accompanying the expansion of the power system scale and the expansion of the assumed number of state changes, and therefore requires a large amount of calculation resources. Therefore, efforts have been made to suppress the calculation resources.

[0004] Patent Document 1 describes a calculation method related to the generation of Thevenin equivalent circuits. Patent Document 2 describes a method that utilizes two-stage screening. Patent Document3 describes a method of screening using eigenvalue analysis.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] The method described in Patent Document 1 reduces the computational scale by simplifying the model being analyzed when analyzing power systems. While such a method is suitable for analyzing phenomena over a wide area, it simplifies the connection configuration of the power system itself. For this reason, it is difficult to evaluate overloads occurring in power systems using the method described in Patent Document 1. Furthermore, while Patent Document 2 introduces a method for reducing constraints in optimal power flow calculations through a two-stage screening process, the method described in Patent Document 2 is difficult to apply to the evaluation of state changes required by grid stabilization systems. Moreover, while the method described in Patent Document 3 can be used for voltage stability analysis of power systems, it cannot be used for power system overload analysis.

[0007] Thus, in order to reduce the computational resources used in power grid stabilization systems, it is necessary to reduce computational resources while simultaneously increasing the computational accuracy required for the use case. Furthermore, in systems with a significant social impact, such as grid stabilization systems, increasing computational accuracy becomes even more important.

[0008] In view of these points, the present invention aims to provide a power grid stabilization system and a power grid stabilization method that can reduce computational resources while maintaining the calculation accuracy for evaluating the state of the power grid. [Means for solving the problem]

[0009] To solve the above problems, for example, the configuration described in the claims may be adopted. The present invention includes several means for solving the above problems, but to give one example, the power system stabilization system of the present invention comprises a power system calculation unit that takes power system status, power system model and event cases as input and performs one or more of either a simplified event calculation or an event calculation, and a margin setting unit that takes margin setting parameters as input and calculates a screening margin from the results of the simplified event calculation and the results of the event calculation for the event cases targeted by the power system calculation unit. [Effects of the Invention]

[0010] According to the present invention, it is possible to maintain calculation accuracy while suppressing the possibility of erroneous screening, and to reduce the number of system conditions to be evaluated by power flow calculations, thereby reducing computational resources. Other issues, configurations, and effects not mentioned above will be clarified by the following description of the embodiments. [Brief explanation of the drawing]

[0011] [Figure 1] This is a configuration diagram showing an example of a power system to which the power system stabilization system according to the first embodiment of the present invention is applied. [Figure 2] This figure shows an example of a power system event to which the power system stabilization system according to the first embodiment of the invention is applied. [Figure 3] This figure shows an example of the hardware configuration of a power grid stabilization system according to a first embodiment of the present invention. [Figure 4] This is a functional block diagram of a power grid stabilization system according to a first embodiment of the present invention. [Figure 5] This is a flowchart showing the entire process by the power grid stabilization system according to the first embodiment of the present invention. [Figure 6] This is a flowchart showing the processing of the margin setting unit of a power grid stabilization system according to a first embodiment of the present invention. [Figure 7]A diagram showing an example of simple power flow calculation and the difference in power flow calculation by the power system stabilization system according to the first embodiment of the present invention. [Figure 8] A diagram showing an example of setting a margin for each event by the power system stabilization system according to the first embodiment of the present invention. [Figure 9] A diagram showing an example of setting a margin for each voltage class by the power system stabilization system according to the first embodiment of the present invention. [Figure 10] A flowchart showing the processing of the event case screening unit of the power system stabilization system according to the first embodiment of the present invention. [Figure 11] A diagram showing an example of the event evaluation result of the power system stabilization system according to the first embodiment of the present invention. [Figure 12] A diagram showing an example of the display of the event evaluation result of the power system stabilization system according to the first embodiment of the present invention. [Figure 13] A block diagram showing an example of the power system stabilization system according to the second embodiment of the present invention.

Embodiments for Carrying Out the Invention

[0012] <First Embodiment Example> Hereinafter, the power system stabilization system and the power system stabilization method according to the first embodiment of the present invention will be described with reference to FIGS. 1 to 12.

[0013] [Example of Power System] FIG. 1 is a diagram simply showing the connection configuration of a power system to which the power system stabilization system according to the first embodiment of the present invention is applied. The power system GR1 shown in FIG. 1 is composed of generators G1 to G3, Loads 1 to 3, buses B1 to B8, and transmission lines L1 to L9. The power system GR1 is intended to supply power to Loads 1 to 3. For example, when an event occurs in the power system, power is supplied to Loads 1 to 3 by changing the outputs of generators G1 to G3.

[0014] [Example of an event] Figure 2 shows examples of event types that may occur in power grid GR1. In power systems, a wide range of events can occur due to various factors. For example, as shown in power system GR1a in Figure 2, if generator G1 is a renewable energy source, the output of generator G1 will fluctuate. Also, as shown in power system GR1b in Figure 2, lightning strikes can cause transmission lines to open at specific locations (indicated by ×), altering the system configuration. Furthermore, as shown in power system GR1c in Figure 2, cold waves can cause specific loads to increase sharply. In all of these events, the power flow through each transmission line and the voltage at each busbar change.

[0015] Power system equipment is designed on the assumption that voltage and power flow will operate within specified ranges. Therefore, if voltage and power flow exceed the design values ​​for a certain period, protective devices designed to prevent equipment damage will activate, potentially leading to a chain reaction of events. Consequently, power system stabilization systems must implement appropriate countermeasures in response to such anticipated events.

[0016] [Hardware configuration of power grid stabilization system] Next, we will describe the hardware configuration of power grid stabilization system 1. Figure 3 shows an example of the hardware configuration of the power grid stabilization system 1. The power grid stabilization system 1 is composed of, for example, a computer, and includes a program database DB1, a database DB2, an input unit 91, an arithmetic unit 92, a display unit 93, a memory 94, and a communication unit 95. These components of the power grid stabilization system 1 can exchange data with each other via the bus BD1. Furthermore, the computer constituting the power grid stabilization system 1 is connected to a measuring instrument 97 and a control terminal 98 via a communication network 96. These measuring instrument 97 and control terminal 98 are also components of the power grid stabilization system 1.

[0017] The program database DB1 stores a complete set of programs for calculation processing related to the power grid stabilization system 1. Database DB2 stores the results of calculations and other data. The input unit 91 can be, for example, a keyboard, mouse, or style La This includes input devices such as microphones and other microphones. The arithmetic unit 92 is composed of, for example, a CPU (Central Processing Unit), a GPU (Graphic Processing Unit), an FPGA (Field Programmable Gate Array), a TPU (Tensor Processing Unit), etc., and is used to perform arithmetic processing. The display unit 93 displays input data and system calculation results, for example, on a monitor or speaker. Memory 94 stores programs when various programs are executed, as well as intermediate results from the arithmetic unit 92. The communication unit 95 communicates data with measuring instruments 97 and control terminals 98 via the communication network 96.

[0018] The program database DB1, database DB2, input unit 91, calculation unit 92, display unit 93, memory 94, and communication unit 95 send and receive data from each other via bus BD1. For example, the results of the calculation unit 92 are sent to memory 94, and the data from memory 94 is sent to display unit 93. In this case, bus BD1 does not necessarily have to be the physical bus of a single computer; it may be a bus that performs a similar role when multiple computers are combined.

[0019] The measuring instrument 97 is installed within the power system and measures, for example, one or more of the following: RMS value, phasor type, or three-phase instantaneous value for voltage, current, voltage phase, frequency, and current phase. Examples include SV / TM and PMU, and it transmits the measurement data to the communication unit 95 of the power system stabilization system 1 via the communication network 96. The control terminal 98 consists of relays and other components that can change the configuration of the power system, and can change the state of the power system itself.

[0020] [Configuration from the perspective of the functions of the power grid stabilization system] Figure 4 is a functional block diagram of the power grid stabilization system 1. Power System Stabilization System 1 is a computer-operated system. Input data for Power System Stabilization System 1 includes various data from sources such as the power system model DB3, power system status DB4, event case DB5, and margin setting parameter DB6. Output data for Power System Stabilization System 1 includes screening margin DB10, screening results DB11, event evaluation results DB12, and event countermeasures DB13. Furthermore, the power system stabilization system 1 includes, as processing units, a power system calculation unit 2, a margin setting unit 3, an event case screening unit 4, an event evaluation unit 5, an event countermeasure planning unit 6, an event matching unit 7, and a countermeasure execution unit 8.

[0021] Here, we will explain the input data for the power grid stabilization system 1. The DB3 power system model stores and models the configuration and components of a power system, such as transmission line impedance, load location, and generator upper and lower limits. The power system status DB4 represents the state of the power system and stores at least one of the following: the voltage and voltage phase of each busbar, the active and reactive power flowing through transmission lines and transformers, and the on / off status of transmission equipment.

[0022] Event Case DB5 stores a list of events in the target power system. As mentioned above, the list of events includes equipment failures, increases in power demand and generation, etc. In this embodiment, a transmission line failure is used as the event. The margin setting parameter DB6 stores parameters that specify the groups for which margins are set. For example, one or more margin setting parameters can be specified, such as by transmission line voltage class, by event, by transmission line, by transmission line owner, or by time. By adjusting the margin setting parameters, it may be possible to improve the screening rate to suit the specific situation.

[0023] Next, we will explain the output data of the power grid stabilization system 1. The screening margin DB10 is a margin used to correct the results of simplified event calculations when they are performed, and it can be set for each transmission route characteristic and event characteristic. The screening results DB11 contains the events screened using the correction results of the simplified event calculation and the screening margin, as well as the results of the simplified event evaluation used for screening. Event evaluation results DB12 shows the results of evaluating screened events using a simplified event calculation. Event countermeasure DB13 is a database that outlines countermeasures for events based on event evaluation results.

[0024] The power system calculation unit 2 has the function of calculating the assumed state of the power system. Specifically, the power system calculation unit 2 has internal functions including a simplified event calculation function 2a and an event calculation function 2b, and performs power system calculation processing. Furthermore, the internal data held by the power system calculation unit 2 includes the internal power system model DB7, the internal power system status DB8, and the internal event case DB9. The power system calculation unit 2 reads the power system model DB3, the power system status DB4, and the event case DB5. Then, the power system calculation unit 2 stores them as the internal power system model DB7, the internal power system status DB8, and the internal event case DB9, respectively, which enables smooth execution of subsequent processing.

[0025] In this embodiment, the power system calculation unit 2 performs power flow calculation using the DC method as a simplified event calculation function 2a, and performs power flow calculation using the AC method as an event calculation function 2b. However, the power system calculation unit 2 performing power flow calculation using the DC method as a simplified event calculation function 2a and power flow calculation using the AC method as an event calculation function 2b is just one example, and the simplified event calculation function 2a and event calculation function 2b may also perform two other types of power flow calculations with different calculation scales, other than the DC method and the AC method. For example, the event calculation function 2b may perform event calculations using one or more of the following functions: power system power flow calculation function, circuit calculation function, transient stability calculation, voltage stability calculation, and short-circuit calculation function. Furthermore, the simplified event calculation function 2a reduces the computational processing of the event calculation function 2b, and can be implemented by using one or more of the following methods: model degradation, reduction of calculation steps, relaxation of calculation conditions, reduction of calculation precision, change of numerical precision, or creation of a substitute model.

[0026] The margin setting unit 3 takes the margin setting parameter DB6 as input and calculates the screening margin DB10 by calling the simplified event calculation function 2a and the event calculation function 2b of the power system calculation unit 2. The margin setting unit 3 calculates the screening margin DB10 for each group set by the margin setting parameter DB6, for example.

[0027] The event case screening unit 4 takes the screening margin DB10 as input and calculates the screening result DB11 by calling the simplified event calculation function 2a of the power system calculation unit 2. Here, the event case screening unit 4 calculates the screening result by adding a margin to the result of the simplified event calculation function of the power system calculation unit 2. The event evaluation unit 5 takes the screening result DB 11 as input and generates the event evaluation result DB 12 by using the event calculation function of the power system calculation unit 2.

[0028] The Event Countermeasure Planning Unit 6 calculates the Event Countermeasure DB 13 using the Event Evaluation Results DB 12 as input. The event matching unit 7 matches events from the power system status DB 4 and sends the appropriate countermeasure to the countermeasure execution unit 8. The countermeasure execution unit 8 executes the countermeasures that have been verified by the event verification unit 7. When executing the countermeasures, the countermeasure execution unit 8 controls the control terminal 98.

[0029] [Processing performed by the power grid stabilization system] Figure 5 is a flowchart showing an example of the overall processing of power grid stabilization system 1. In Figure 5, the operation of the power grid stabilization system 1 is explained using different flowcharts, separating it into normal operation and event occurrence. However, it may also be explained as a continuous series of flowcharts, assuming that normal operation and event occurrences occur consecutively.

[0030] First, let's explain the normal operation shown in the flowchart on the left side of Figure 5. The power system calculation unit 2 reads the power system model DB3 and event case DB5 (step S1). Next, the power system calculation unit 2 and the margin setting unit 3 read the power system status DB4 and margin setting parameter DB6 (step S2). Then, the margin setting unit 3 sets the margin (step S3).

[0031] Next, the event case screening unit 4 screens events (step S4). The event evaluation unit 5 evaluates events (step S5). Furthermore, the event countermeasure planning unit 6 plans countermeasures for the events (step S6). Furthermore, the countermeasure execution unit 8 updates the event countermeasures to be executed based on the event countermeasures planned by the event countermeasure planning unit 6 (step S7). Then, the display unit 93 displays various results, such as the event countermeasures (step S8). An example of the display performed here will be described later. Furthermore, the processes from step S2 to step S8 are repeatedly executed using periodic calculations.

[0032] Next, we will explain the processing flow when an event occurs, as shown in the flowchart on the right side of Figure 5. First, the power system calculation unit 2 acquires the status of the power system (step S9). Next, the event matching unit 7 matches the events (step S10). Then, the countermeasure execution unit 8 executes the event countermeasure based on the matching by the event matching unit 7 (step S11).

[0033] As explained above, by executing the series of processes shown in the flowchart of Figure 5, computing resources can be reduced, allowing for the handling of more events. Furthermore, event countermeasures can be planned more quickly.

[0034] [Processing performed by the margin setting unit] Figure 6 is a flowchart showing the details of the process performed by the margin setting unit 3. First, the margin setting unit 3 reads the power system status from the power system calculation unit 2 and obtains the margin setting parameter DB6 (step S31). Then, the margin setting unit 3 checks the system configuration of the obtained power system status and determines whether or not there has been a change in the system configuration (step S32).

[0035] If there is a change in the system configuration in step S32 (YES in step S32), the margin setting unit 3 performs an event evaluation calculation using the event calculation function 2b (step S33). Furthermore, the margin setting unit 3 performs a simplified event evaluation calculation using the simplified event calculation function 2a (step S34). After that, the margin setting unit 3 calculates the difference between the event evaluation calculation result and the simplified event evaluation calculation result (step S35). Also, the margin setting unit 3 calculates the margin from the difference between the result of the simplified event evaluation calculation and the result of the event evaluation calculation based on the margin setting parameters (step S36).

[0036] Furthermore, if there was no change in the system configuration in step S32 (NO in step S32), the margin setting unit 3 reloads the calculated margin (step S37). Then, after calculating the margin in step S36 and after rereading the margin in step S37, the margin setting unit 3 outputs the obtained margin (step S38).

[0037] In the simplified event evaluation calculation in step S33 and the event evaluation calculation in step S34, the margin setting unit 3 performs DC power flow calculation and AC power flow calculation, respectively, for events such as the opening of power transmission lines in the power system. In DC power flow calculations, it is assumed that the voltage of the power system is constant, and the margin setting unit 3 determines the power flow of the power system by linearizing the resistance of the transmission route and the nonlinear elements of the power flow equation. With appropriate measures, the aforementioned power system events can be evaluated without iterative calculations, which is advantageous when evaluating multiple events. On the other hand, there are errors in the power flow calculated using DC power flow calculations.

[0038] Here, using Figure 7, we will explain an example of obtaining the difference between the event evaluation calculation result and the simplified event evaluation calculation result in step S35. In step S35 of Figure 6, the margin setting unit 3 obtains the difference between the simplified event evaluation calculation and the event evaluation calculation for each event. The example in Figure 7 shows the difference between the simplified event evaluation calculation and the event evaluation calculation (vertical axis in Figure 7) for an event (horizontal axis in Figure 7). Here, Figure 7 shows an example of the error in apparent power S of a power transmission route, but active power P may also be used. Furthermore, when using apparent power S, if the reactive power Q after an event cannot be determined by simplified event evaluation, it may be corrected using the reactive power Q before the event.

[0039] Figure 7 shows the error for each event and for each voltage class of the power transmission route. Specifically, in Figure 7, the voltage classes are divided into 110kV (values ​​indicated by stars in Figure 7), 275kV (values ​​indicated by triangles in Figure 7), and 500kV (values ​​indicated by circles in Figure 7). As can be seen from Figure 7, there is a tendency for errors to be larger at certain voltage levels and for certain events. This is due to the principles of the simplified event evaluation and event evaluation described above. Here, the margin is used to account for the error between the simplified event evaluation and the event evaluation, and is maintained in various forms.

[0040] As an example, let's explain the case where margins are set for each event (or group). Figure 8 shows an example where margins are set to events. In the example in Figure 8, Event 1 has a maximum margin value of 0.15 (15%). Similarly, Event 2 has a maximum margin value of 0.20 (20%). Thus, the screening margin DB10 shown in Figure 8 represents the maximum error between the simplified event evaluation and the event evaluation for each event.

[0041] As mentioned above, by understanding the maximum error between the simplified event evaluation and the event evaluation for each event, the results of the simplified event evaluation can be used as a reliable indicator for each event. For example, if the event is the opening of a power transmission line, the error will differ for each event, demonstrating that this metric is an effective tool. By understanding the maximum error for each event in this way, a reliable metric can be created for the results of the simplified event evaluation for each event. For example, if the event is the opening of a power transmission line, the error will differ for each event, demonstrating that this metric is an effective tool.

[0042] Figure 9 shows an example of setting margins for each voltage class of the power transmission route. That is, the voltage class of the power transmission route is set to 110kV (Figure 9). 9 (Values ​​indicated by the asterisk) and 275kV (Figure) 9 (The value shown by the triangle in the figure) and 500kV (Figure 9 The voltage is divided into three categories (indicated by the circle), and the highest value within each voltage category is used as the margin for that category. For example, in the 110kV voltage class, the highest margin value for that voltage class is 0.20 (20%). Similarly, in the 275kV voltage class, the highest margin value is 0.10 (10%). Furthermore, in the 500kV voltage class, the highest margin value is 0.05 (5%).

[0043] By setting appropriate margins for each voltage class in this way, misjudgments (false negatives and false positives) caused by uniform margins can be avoided. Furthermore, setting margins for each voltage class improves explainability compared to setting them for each event.

[0044] In the explanation so far, we have described the process separately for each event and each voltage class, but it is also possible to combine both processes, and you may set a margin using at least one of the following factors: geographical location, transmission line owner, number of transmission lines, etc.

[0045] As explained above, by setting a margin for each event and each voltage class, the power system stabilization system 1 of this embodiment can take into account the error of simplified event evaluation.

[0046] [Processing performed by the Event Case Screening Unit] Figure 10 is a flowchart showing the details of the processing in the event case screening unit 4. First, the event case screening unit 4 reads the margin (step S41). Next, the event case screening unit 4 performs a simplified event calculation using the simplified event calculation function 2a (step S42). The event case screening unit 4 also corrects the results of the simplified event calculation (step S43). Then, the event case screening unit 4 determines whether an event violation has occurred using a margin (step S44). Finally, the event case screening unit 4 outputs a violation event (step S45).

[0047] As already explained, evaluation based on simplified event calculation does not require computational resources, but it carries the risk of misjudgment due to errors during event evaluation. Here, as in this embodiment, by fixing the margin once for each system configuration, it is possible to reduce the computational scale in a reasonable manner while suppressing the risk of incorrectly screening events that would result in violations.

[0048] Furthermore, if the event exceeds the margin limit, the event evaluation unit 5 will only use the screened results for the event evaluation function, thus allocating computational resources only to important events.

[0049] [Examples of screening results and event evaluation results] Next, we will explain examples of screening results and event evaluation results with reference to Figure 11. The example in Figure 11 summarizes the maximum overload of transmission lines for each event, for the benefit of power system operators. Specifically, it shows power system operators the event cases that require detailed calculations of the simplified event evaluation results (center) included in the screening results DB11, and the event cases that require detailed calculations of the event evaluation results DB12 (right). By displaying this information on the display unit 93, it becomes clear why a particular event was screened based on the information about the event case for which detailed calculation was required. As a result, power system operators can clearly understand the basis for the screening.

[0050] For example, in the example in Figure 11, Event 2 was calculated to have an overload rate of 85%, but because there is a 20% margin, it is excluded from screening. Therefore, the power system operator can see that it is an overload according to the event evaluation results. On the other hand, in the case of Event 1, although it is an 80% overload, it is excluded because even with an additional 15% margin it does not become an overload.

[0051] Based on the event evaluation results, for cases where countermeasures are required, as explained in the flowchart in Figure 5, the countermeasure execution unit 8 calculates countermeasures to resolve the violation in step S6 and updates the countermeasures in step S7. Then, in step S8, the display unit 93 displays the results. Furthermore, when an event occurs, the event matching unit 7 matches the event, allowing the pre-prepared countermeasures to be executed.

[0052] [Examples of screening results and event evaluation results] Next, Figure 12 shows an example of the display screen 93a of the display unit 93. The display screen 93a shown in Figure 12 shows the target electric power The margins for each voltage class when the margins shown in Figure 8 are set for system GR1, the screening margin DB10 as a screening result, and the screening results and event evaluation results shown in Figure 11 are displayed. Figure 12 shows an example where these are displayed simultaneously, but you may choose to display at least one of them and omit the others. Alternatively, you may use multiple screens so that these display elements are shown on separate screens. In addition to what is shown in Figure 12, details of the measures to rectify the violation may also be displayed.

[0053] <Second Embodiment Example> Next, a power grid stabilization system and a power grid stabilization method according to a second embodiment of the present invention will be described with reference to Figure 13. In the configuration of this embodiment shown in Figure 13, the power grid stabilization system 1 is the same as the power grid stabilization system 1 described in Figures 1 to 12 in the first embodiment. The second embodiment of the present invention differs from the first embodiment in that it includes a control amount calculation system 10 to which the results (margin) obtained by the power system stabilization system 1 are supplied.

[0054] The control variable calculation system 10 shown in Figure 13 calculates the control using a preventative control function that avoids the effects of an event before the event occurs. As shown in Figure 13, the control variable calculation system 10 includes an optimization model generation unit 11, an optimization model margin assignment unit 12, and an optimization calculation unit 13.

[0055] The optimization model generation unit 11 takes the screening margin, power system state, power system model, and event cases output by the power system stabilization system 1 as input and generates an optimization model with simplified constraints. The optimization model margin assignment unit 12 assigns a margin to the optimization model using the screening margin of the optimization model generation unit 11. The optimization calculation unit 13 calculates a solution to the optimization model and determines control points that can avoid all anticipated violations.

[0056] Here, when calculating the control point that avoids all anticipated violations, the control point can be found by minimizing the evaluation index of the function that evaluates the controlled quantity, as shown in the following equation.

[0057] [Mathematics 1] Min f(C) st g(V,θ,C)=b A(V,θ,C) ≤ b

[0058] Here, f(C) is the objective function for evaluating the controlled variable, and st g(V,θ,C)=b is an equality constraint calculated from the voltage (V), phase (θ), and controlled variable (C). Also, A(V,θ,C)≦b is an inequality constraint calculated from the voltage (V), phase (θ), and controlled variable (C). Examples of objective functions include the amount controlled by the generator, the number of times equipment is controlled, and the cost of control. Similarly, an example of an equality constraint is that the inflow power and output power of the power system must be equal.

[0059] Furthermore, inequality constraints include, for example, when considering multiple time cross-sections, the control amount between time cross-sections being within a predetermined range, and the control amount being within a specific range. The power flow equation is a type of equality constraint and is known to mainly contain nonlinear elements. In this technical field, it is also called Optimal Power Flow (OPF).

[0060] In solving the optimization problem described above, conventional approaches include linearizing the nonlinear elements to find the solution while keeping them nonlinear, or removing as many nonlinear elements as possible by changing the form. When the solution is found while keeping the nonlinear, the optimization problem takes on a non-convex form, and therefore, the likelihood of converging to a useful solution is generally low. Furthermore, when the optimization problem is made more linear, the computation time increases compared to simply linearizing it. In environments with limited computational resources, there is a need to perform calculations with constraints as linear as possible. However, as already explained, linearization involves errors, which may prevent the calculation of control points that satisfy the constraints.

[0061] Therefore, in this embodiment, by using the screening margin of the margin setting unit 3 (Figure 4) of the power grid stabilization system 1, a margin can be added to the linearized constraint equation. In the control variable calculation system 10, the optimization model generation unit 11 takes the screening margin output by the power system stabilization system 1, the power system state, the power system model, and the event cases as input to generate an optimization model with simplified constraints. Then, the optimization model margin assignment unit 12 adds a margin to the optimization model using the screening margin, and the optimization calculation unit 13 calculates the solution to the optimization model.

[0062] Specifically, the control variable is calculated by adding a margin to the optimization model mentioned above.

[0063] [Math 2] Min f(C) st g′(V,θ,C,M)=b A(V,θ,C)≦b

[0064] Here, st g′(V,θ,C,M)=b is a simplified constraint, representing the state in which a margin (M) is added to the optimization model. By generating the model in this way, for example, the solution space can be narrowed while preserving the linearized state, thus shortening convergence and the time to convergence.

[0065] <Variation> The embodiments described above are explained in detail for the purpose of clearly illustrating the present invention, and are not necessarily limited to those having all the configurations described. Furthermore, the configurations and processes described in the above embodiments can be modified or altered in various ways.

[0066] Furthermore, although a CPU was used as the arithmetic unit (Figure 3) in the above-described embodiment, other arithmetic processing units may also be used. For example, as the arithmetic unit 92, some or all of the processing functions may be implemented by dedicated hardware such as an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit).

[0067] Furthermore, in configuration diagrams such as Figures 3 and 4, only control lines and information lines deemed necessary for explanation are shown, and not all control lines and information lines are necessarily shown in the actual product. In reality, it can be assumed that almost all components are interconnected. Also, in the flowcharts shown in Figures 5, 6, and 10, the processing order may be changed or multiple processes may be executed simultaneously, as long as the processing result is the same.

[0068] Furthermore, the arithmetic unit (CPU) needs to implement a program that executes the processes described in the flowcharts in Figures 8 and 9. This program may be stored in the memory where the program database DB1 is stored, or it may be stored on an external memory, IC card, SD card, optical disc, or other recording medium and transferred to the power system stabilization system 1. [Explanation of Symbols]

[0069] 1...Power system stabilization system, 2...Power system calculation unit, 2a...Simplified event calculation function, 2b...Event calculation function, 3...Margin setting unit, 4...Event case screening unit, 5...Event evaluation unit, 6...Event countermeasure planning unit, 7...Event matching unit, 8...Countermeasure execution unit, 10...Control amount calculation system, 11...Optimization model generation unit, 12...Optimization model margin application unit, 13...Optimization calculation unit, 35...Display, 91...Input unit, 92...Calculation unit, 93...Display unit, 93a...Display screen, 94...Memory, 95...Communication unit, 96...Communication network, 97...Total Measuring instrument, 98...Control terminal, B1...Bus, BD1...Bus, DB1...Program database, DB2...Database, DB3...Power system model, DB4...Power system status, DB5...Event case, DB6...Margin setting parameter, DB7...Internal power system model, DB8...Internal power system status, DB9...Internal event case, DB10...Screening margin, DB11...Screening result, DB12...Event evaluation result, DB13...Event countermeasure, G1...Generator, GR1,GR1a,GR1b,GR1c...Power system, L1...Transmission line

Claims

1. A power system calculation unit takes power system status, power system model, and event cases as input and performs one or more of either simplified event calculations or event calculations. The system includes a margin setting unit that takes margin setting parameters as input and calculates a screening margin from the results of the simplified event calculation and the event calculation for the event cases targeted by the power system calculation unit. Power grid stabilization system.

2. The margin setting unit calculates a screening margin for each group set by the margin setting parameter. The power grid stabilization system according to claim 1.

3. The margin setting unit uses the maximum error between the simplified event calculation and the event calculation as the screening margin. The power grid stabilization system according to claim 2.

4. The aforementioned margin setting parameter is a parameter that specifies the group for which the margin is set, and specifies the target for setting the margin by at least one of the following: per transmission line voltage class, per event, per transmission line, per transmission line owner, or per time. The power grid stabilization system according to claim 3.

5. Furthermore, the system includes an event case screening unit that takes the aforementioned screening margin as input and calculates a screening result by adding the margin to the result of the simplified event calculation of the power system calculation unit. The power grid stabilization system according to claim 4.

6. The event case screening unit screens event cases using the screening margin calculated by the margin setting unit. The power grid stabilization system according to claim 5.

7. The screening results include the results of the simplified event calculation and event cases for which detailed calculation was required. The power grid stabilization system according to claim 6.

8. Furthermore, the system includes an event evaluation unit that takes the screening results as input and performs the event calculation in the power system calculation unit to calculate the event evaluation result. The power grid stabilization system according to claim 7.

9. The event calculation in the power system calculation unit is at least one of the following: power flow calculation, circuit calculation, transient stability calculation, voltage stability calculation, and short-circuit calculation of the power system. The power grid stabilization system according to claim 8.

10. The simplified event calculation in the power system calculation unit reduces the computational processing of the event calculation by simplifying the calculation using at least one of the following methods: model degradation, reduction of calculation steps, relaxation of calculation conditions, reduction of calculation precision, change of numerical precision, or creation of a substitute model. The power grid stabilization system according to claim 9.

11. Furthermore, the system includes an event countermeasure planning unit that calculates countermeasures for events, taking the event evaluation results from the event evaluation unit as input. The power grid stabilization system according to claim 8.

12. Furthermore, an event matching unit takes the power system status and event countermeasures as input, matches the events, and selects an event countermeasure. The countermeasure execution unit executes the event countermeasures selected by the event matching unit, It includes a display unit that displays one or more input and output data. The power grid stabilization system according to claim 11.

13. Furthermore, the system includes an optimization model generation unit that generates an optimization model with simplified constraints, using the screening margin, power system state, power system model, and event cases output by the power system stabilization system as inputs. An optimization model margin assignment unit characterized by assigning a margin to the optimization model using the screening margin of the optimization model generation unit, The system comprises an optimization calculation unit that calculates a solution to the optimization model. The power grid stabilization system according to claim 10.

14. This is a power grid stabilization method that performs power grid stabilization processing using computer calculations. A power system calculation process that takes power system status, power system model, and event cases as input and performs one or more of either a simplified event calculation or an event calculation, The process includes a margin setting process that takes margin setting parameters as input and calculates a screening margin from the results of the simplified event calculation and the event calculation results for the event cases targeted when the power system calculation process is performed. Power system stabilization method.

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