Power grid stabilization device, computer program for power grid stabilization device, and power grid stabilization method

Abstract

To provide a power system stabilization device and method that efficiently perform power supply limitation of a renewable energy power supply and a synchronous power generator while ensuring synchronization power in a power system including both the synchronous power generator and the renewable energy power supply.SOLUTION: A power system stabilization device 1 includes: a stability calculation unit that calculates the stability when a power system 9a including synchronous power generators 2-1 to 2-3 and a renewable energy power supply 3 break down; a contraction system model creation unit that creates a contraction system model by using one or more nodes as contraction starting point nodes to make a topology of a power system including unstable power generators in a radial shape and contracting the power system including a stable power generator at an upper level from the contraction starting point node; a P-δ curve calculation unit that extracts the synchronous power generator that steps out based on the contraction system model and calculates a P-δ curve showing a relation between a phase angle and output effective power for each synchronous power generator; and a power control device selection unit that selects a target to limit the power supply from the synchronous power generator and the renewable energy power supply based on power supply limitation effect calculated based on the P-δ curve.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This embodiment relates to a power grid stabilization device that controls multiple generators that supply power to stabilize a power grid, a computer program for the power grid stabilization device, and a method for stabilizing a power grid. [Background technology]

[0002] A power grid stabilization device is known that controls multiple generators that supply power. Multiple generators are controlled by the power grid stabilization device, and the power grid is stabilized. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-096472 [Overview of the project] [Problems that the invention aims to solve]

[0004] In recent years, large-scale renewable energy sources, such as offshore wind power, have attracted attention and are being introduced. When a power grid failure occurs and synchronous generators lose synchronization, power grid stabilization devices perform power restriction (hereinafter referred to as electric control) by disconnecting some of the synchronous generators from the power grid, thereby stabilizing the power grid.

[0005] When a large amount of renewable energy is introduced, if the number of synchronous generators connected to the power grid decreases, the synchronizing force will decline, and the power grid will become more unstable. For this reason, it is desirable that not only synchronous generators but also renewable energy sources be subject to electric control, and that electric control be implemented for both renewable energy sources and synchronous generators while ensuring synchronizing force.

[0006] Conventional grid stabilization systems select the power source to be controlled based on the expansion of the internal phase difference angle of synchronous generators. However, renewable energy sources generate DC power that does not have an internal phase difference angle, so it is not possible to select the power source to be controlled based on the internal phase difference angle. For this reason, in a power grid that includes both synchronous generators and renewable energy sources, it is not possible to select the synchronous generators and renewable energy sources as power sources to be controlled using the same calculation.

[0007] For example, one conventional power grid stabilization device calculates the deceleration sensitivity when the output of a renewable energy source decreases relative to a synchronous generator with an accelerating tendency, using this as an indicator of the electric control effect, and determines the amount of renewable energy output reduction that can be stabilized. The above power grid stabilization device selects electric control units only for renewable energy sources. Therefore, in a power grid that includes both synchronous generators and renewable energy sources, it does not select an appropriate electric control unit that compares the electric control effects of both synchronous generators and renewable energy sources.

[0008] This embodiment aims to provide a power grid stabilization device, a computer program for the power grid stabilization device, and a power grid stabilization method that fairly and efficiently control the electric currents of renewable energy sources and synchronous generators in a power grid that includes both synchronous generators and renewable energy sources. [Means for solving the problem]

[0009] The power system stabilization device of this embodiment is characterized by having the following configuration. (1) A stability calculation unit that calculates the stability of a power system including synchronous generators and renewable energy sources in the event of a failure. (2) A reduced system model creation unit that, when the stability calculated by the stability calculation unit is determined to be unstable, extracts stable and unstable generators from the synchronous generators, sets one or more nodes as reduction starting nodes so that the topology of the power system including the unstable generators becomes radial, reduces the power system including the stable generators in a higher voltage class close to the main system from the set reduction starting nodes, and creates a reduced system model. (3) If the stability calculated by the stability calculation unit is determined to be unstable, the P-δ curve calculation unit extracts the synchronous generators that will lose synchronism based on the reduced system model created by the reduced system model creation unit, and calculates a P-δ curve showing the relationship between the phase angle and the active power output for each of the synchronous generators that will lose synchronism. (4) A control unit that calculates an electric control effect based on the P-δ curve calculated by the P-δ curve calculation unit, based on at least one of the acceleration energy and deceleration energy generated when the renewable energy power source or the synchronous generator that is out of step is electrically controlled, and selects an object to be electrically controlled from the synchronous generator and the renewable energy power source based on the calculated electric control effect. [Brief explanation of the drawing]

[0010] [Figure 1] Overall diagram showing the configuration of a system using a power grid stabilization device according to the first embodiment. [Figure 2] This figure shows the configuration of the calculation unit of the power grid stabilization device according to the first embodiment. [Figure 3] This diagram shows the program flow of the calculation unit of the power grid stabilization device according to the first embodiment. [Figure 4] This diagram shows the program flow for determining the range to be reduced by the power grid stabilization device according to the first embodiment. [Figure 5] This diagram shows the program flow for determining the reduction starting node by the power grid stabilization device according to the first embodiment. [Figure 6] This diagram shows the program flow for extracting a step-out locus by a power system stabilizer according to the first embodiment. [Figure 7] This diagram shows the program flow for grouping reduction starting nodes based on out-of-synchronization locus by a power system stabilizer according to the first embodiment. [Figure 8] This figure shows an example of a reduced power system model using a power system stabilization device according to the first embodiment. [Figure 9]Figure showing an example of a power system model when the stable generator group by the power system stabilizer according to the first embodiment is reduced [Figure 10] Figure showing the flow of a program related to the selection of an electric control machine by the power system stabilizer according to the first embodiment [Figure 11] Figure showing an example of the timing of transient stability calculation related to the creation of a P-δ curve by the power system stabilizer according to the first embodiment [Figure 12] Figure showing the flow of a program related to the phase difference correction of the P-δ curve by the power system stabilizer according to the first embodiment [Figure 13] Figure for explaining the calculation of accelerating energy and decelerating energy based on the P-δ curve by the power system stabilizer according to the first embodiment [Figure 14] Figure for explaining the comparison of accelerating energy and decelerating energy after electric control by the power system stabilizer according to the first embodiment [Figure 15] Figure for explaining an example of calculating the electric control effect by the power system stabilizer according to the first embodiment [Figure 16] Figure for explaining the comparison of the electric control effects by the power system stabilizer according to the first embodiment

Embodiments for Carrying Out the Invention

[0011] [1. First Embodiment] [1-1. Overall Configuration] FIG. 1 is an overall view showing the configuration of a system related to a power system 9a using a power system stabilizer 1 according to the first embodiment. In the present embodiment, when there are a plurality of devices or members having the same configuration, they are described with the same number, and when each of the individual devices or members having the same configuration is described, they are distinguished by attaching a suffix to the common number with a hyphen.

[0012] The power system 9a includes a synchronous generator 2 and a renewable energy power source 3. The renewable energy power source may be referred to as a renewable energy power source.

[0013] Synchronous generator 2-1 is connected to power system 9b via transformer 6-1, circuit breaker 5-1, transmission line 4-2 and transmission line 4-1. Similarly, synchronous generator 2-2 is connected to power system 9b via transformer 6-2, circuit breaker 5-2, transmission line 4-2 and transmission line 4-1, and synchronous generator 2-3 is connected to power system 9b via transformer 6-3, circuit breaker 5-3, transmission line 4-2 and transmission line 4-1.

[0014] Synchronous generators 2-1, 2-2, and 2-3 are composed of power generation devices such as nuclear, hydroelectric, and thermal power plants. Transformers 6-1, 6-2, and 6-3 convert the voltage of the power output from synchronous generators 2-1, 2-2, and 2-3 to a predetermined voltage, respectively.

[0015] Circuit breakers 5-1, 5-2, and 5-3 are composed of switches that interrupt the power supply, interrupting the power output from synchronous generators 2-1, 2-2, and 2-3, respectively. Circuit breakers 5-1, 5-2, and 5-3 are connected to the power system stabilization device 1 by communication lines, and their switching is controlled by the power system stabilization device 1.

[0016] Renewable energy source 3 is connected to power grid 9b via transformer 6-4, circuit breaker 5-4, transmission line 4-3, and transmission line 4-1. Renewable energy source 3 consists of power generation devices such as solar and wind power. Transformer 6-4 converts the voltage of the power output from renewable energy source 3 to a predetermined voltage.

[0017] Information gathering devices 7-1, 7-2, 7-3, 7-4, 7-5, 7-6, and 7-7 consist of detection devices that detect state quantities such as frequency, voltage, current, phase, active power, and reactive power. Information gathering devices 7-1, 7-2, and 7-3 are installed on synchronous generators 2-1, 2-2, and 2-3, respectively. Information gathering devices 7-1, 7-2, and 7-3 detect state quantities such as frequency, voltage, current, phase, active power, and reactive power of synchronous generators 2-1, 2-2, and 2-3, respectively, and transmit them to the power system stabilization device 1.

[0018] The information gathering device 7-4 is installed at the renewable energy power source 3. The information gathering device 7-4 detects state quantities of the renewable energy power source 3, such as frequency, voltage, current, phase, active power, and reactive power, and transmits them to the power system stabilization device 1.

[0019] Information gathering devices 7-5, 7-6, and 7-7 are installed on transmission lines 4-1, 4-2, and 4-3, respectively. Information gathering devices 7-5, 7-6, and 7-7 detect state quantities of transmission lines 4-1, 4-2, and 4-3, such as frequency, voltage, current, phase, active power, and reactive power, and transmit them to the power system stabilization device 1.

[0020] The fault detection device 8 consists of detection devices that detect faults based on abnormal voltage, ground fault current, etc. The fault detection device 8 detects faults in the power generation system, which consists of power grids 9a and 9b, synchronous generators 2-1, 2-2, and 2-3, and renewable energy source 3, and transmits the information to the power grid stabilization device 1.

[0021] [1-2. Configuration of Power System Stabilization Device 1] The power system stabilization device 1 is a device that disconnects the synchronous generators 2-1, 2-2, 2-3 and the renewable energy source 3 from the power system 9 using circuit breakers 5-1, 5-2, 5-3, and 5-4 when a fault occurs in the power generation system which consists of power systems 9a and 9b, synchronous generators 2-1, 2-2, 2-3, and renewable energy source 3. The control that disconnects the synchronous generators 2-1, 2-2, 2-3 and the renewable energy source 3 from the power system 9 is called electric control.

[0022] The power system stabilization device 1 has a calculation unit 10 and a control unit 20. The calculation unit 10 and the control unit 20 are each composed of computers and are connected inside the power system stabilization device 1. Alternatively, the calculation unit 10 and the control unit 20 are composed of a single computer. The power system stabilization device 1 is installed in a command room such as a power dispatch center, system control center, or central control center that monitors and controls power systems 9a and 9b.

[0023] The calculation unit 10 receives state quantities such as frequency, voltage, current, phase, active power, and reactive power of synchronous generators 2-1, 2-2, 2-3, renewable energy source 3, and transmission lines 4-1, 4-2, 4-3 from information collection devices 7-1, 7-2, 7-3, 7-4, 7-5, 7-6, and 7-7, and selects the generators necessary to stabilize power systems 9a and 9b as electric control targets. Generators to be electric control targets are called electric control units. One or more of the synchronous generators 2-1, 2-2, 2-3 and renewable energy source 3 are selected as electric control units necessary to stabilize power systems 9a and 9b.

[0024] The control unit 20 receives fault information from the fault detection device 8, and if it determines that a fault has occurred, it transmits control commands to the circuit breakers 5-1, 5-2, 5-3, and 5-4 based on instructions from the calculation unit 10.

[0025] (A. Configuration of the arithmetic unit 10) The calculation unit 10 is comprised of a computer and is connected to the control unit 20 inside the power system stabilization device 1. Figure 2 shows the configuration of the calculation unit 10. The calculation unit 10 includes a stability calculation unit 11, a reduced system model creation unit 12, a P-δ curve calculation unit 13, and a power control unit selection unit 14. The stability calculation unit 11, the reduced system model creation unit 12, the P-δ curve calculation unit 13, and the power control unit selection unit 14 are comprised of calculation units within a computer or software modules.

[0026] When the calculation unit 10 is composed of software modules, the stability calculation unit 11 may be called the stability calculation step, the reduced system model creation unit 12 the reduced system model creation step, the P-δ curve calculation unit 13 the P-δ curve calculation step, and the electric control unit selection unit 14 the electric control unit selection step. Furthermore, the procedure performed by the stability calculation unit 11 may be called the stability calculation procedure, the procedure performed by the reduced system model creation unit 12 the reduced system model creation procedure, the procedure performed by the P-δ curve calculation unit 13 the P-δ curve calculation procedure, and the procedure performed by the electric control unit selection unit 14 the electric control unit selection procedure.

[0027] The stability calculation unit 11 calculates the stability of the power system 9 in the event of a failure. The stability calculation unit 11 calculates the stability of the power system 9a, which includes synchronous generators 2-1, 2-2, 2-3 and renewable energy source 3, for the assumed target failure cases.

[0028] The reduced system model creation unit 12 reduces a portion of the power system 9a to a 1-unit, 2-load model, and creates a reduced system model in which the topology of the entire power system 9 is transformed to be radial. If the stability calculated by the stability calculation unit 11 is determined to be unstable, the reduced system model creation unit 12 extracts stable and unstable generator groups from the synchronous generators 2, sets one or more nodes as reduction starting nodes so that the topology of the power system 9 including the unstable generator group becomes radial, and reduces the power system 9 including the higher-level stable generator groups close to the voltage class of the main system from the set reduction starting nodes to create a reduced system model. A radial topology refers to a shape that extends in two or more directions from a single point.

[0029] The reduced system model creation unit 12 extracts the synchronous generators 2 that are out of step, belonging to the reduction starting node set in the reduced system model created so that the topology is radial, extracts the synchronous generators 2 that are out of step, belonging to each synchronous locus, which are out of step, based on the branch phase difference angle, and when the synchronous generators 2 that are out of step belonging to the reduction starting node and the synchronous generators 2 that are out of step belonging to the synchronous locus match, it newly groups the reduction starting nodes by synchronous locus, and creates a reduced system model for each newly grouped group of reduction starting nodes.

[0030] A "loose-stepping locus" refers to a location where the phase angle fluctuates significantly. A location where the phase angle fluctuates beyond a predetermined reference value is called a loose-stepping locus. For example, if the phase angle difference between the primary and secondary sides of transformer 6 is greater than or equal to a predetermined reference value, transformer 6 is considered a loose-stepping locus. Similarly, if the phase angle difference between the sending and receiving ends of transmission line 4 is greater than or equal to a predetermined reference value, transmission line 4 is considered a loose-stepping locus.

[0031] The P-δ curve calculation unit 13 calculates the P-δ curves for each of the candidate generators to be electrically controlled among the synchronous generators 2-1, 2-2, 2-3 and the renewable energy source 3, based on the reduced system model created by the reduced system model creation unit 12. The P-δ curve is a graph showing the relationship between the internal phase difference angle and the active power output in the synchronous generators 2-1, 2-2, and 2-3.

[0032] If the stability calculated by the stability calculation unit 11 is determined to be unstable, the P-δ curve calculation unit 13 extracts the synchronous generators 2 that will lose synchronism based on the reduced system model created by the reduced system model creation unit 12, and calculates and creates a P-δ curve for each of the synchronous generators 2 that will lose synchronism, showing the relationship between the phase angle and the active power output.

[0033] The P-δ curve calculation unit 13 calculates and creates individual P-δ curves for the synchronous generators 2 included in the portion of the power system 9 that falls outside the reduction range of the reduced system model, based on a radial system model that combines the reduced system model created by the reduced system model creation unit 12 with the portion of the power system 9 that falls outside the reduction range of the reduced system model.

[0034] The P-δ curve calculation unit 13 calculates the P-δ curve using state variables as parameters, based on the stability calculated by the stability calculation unit 11 and state variables relating at least voltage, phase, active power, and reactive power at any time cross-section after fault removal in a hypothetical fault case. The state variables at any time cross-section after fault removal may be state variables of the synchronous generator 2 that is losing synchronism immediately before or immediately after electric control.

[0035] The P-δ curve calculation unit 13 calculates the phase difference between the base generator and the other synchronous generators 2, renewable energy sources 3, and loads, corresponding to the change in the internal phase difference angle of the base generator, which is the subject of the P-δ curve calculation, based on the stability calculated by the stability calculation unit 11, the internal phase difference angle of the synchronous generator 2 that is losing synchronism, and the time-series changes in the terminal voltage phases of the renewable energy source 3 and the load. The P-δ curve is then calculated using the phase difference as a parameter. The base generator refers to the generator among the P-δ curve calculation targets that is subject to evaluation of the effect of electric control.

[0036] The electric control unit selection unit 14 selects the electric control target necessary for stabilization, using the deceleration energy, acceleration energy, and electric control effect when electric control is applied to candidate generators, based on the P-δ curve created by the P-δ curve calculation unit 13. Based on the P-δ curve calculated by the P-δ curve calculation unit 13, the electric control unit selection unit 14 calculates the electric control effect based on at least one of the acceleration energy and deceleration energy generated when electric control is applied to the renewable energy power source 3 or the synchronous generator 2 that is out of synchronism, and selects the target to be electric controlled from the synchronous generator 2 and the renewable energy power source 3 based on the calculated electric control effect.

[0037] The electric control unit 14 calculates the electric control effect for each synchronous generator 2 that loses synchronism, based on the P-δ curve calculated by the P-δ curve calculation unit 13. This effect is calculated from the difference between the energy calculated from the output before electric control of the renewable energy source 3 or the synchronous generator 2 that loses synchronism (excluding the base generator which is the subject of the P-δ curve calculation) and the energy calculated from the output after electric control. Based on the calculated magnitude of the electric control effect for each renewable energy source 3 or the synchronous generator 2 that loses synchronism, the unit selects the target for electric control.

[0038] The electric control unit 14 calculates the deceleration energy and acceleration energy when electrically controlled for each renewable energy source 3 or synchronous generator 2 that loses synchronism, based on the P-δ curve calculated by the P-δ curve calculation unit 13, for each renewable energy source 3 (excluding the base generator that is subject to the P-δ curve calculation) and each synchronous generator 2 that loses synchronism, and selects the renewable energy source 3 or synchronous generator 2 that loses synchronism whose deceleration energy exceeds the acceleration energy as the target for electric control.

[0039] (B. Configuration of the control unit 20) The control unit 20 is composed of a computer and is connected to the calculation unit 10 inside the power system stabilization device 1. Based on instructions from the calculation unit 10, the control unit 20 transmits commands to the circuit breakers 5-1, 5-2, 5-3, and 5-4, which are connected via a communication line, to open and close the circuit breakers.

[0040] The above describes the configuration of the power system stabilization device 1 according to this embodiment.

[0041] [1-2. Effect]

[0042] Next, an overview of the operation of the power system stabilization device 1 of this embodiment will be described based on Figures 1 to 16. Figure 3 is a diagram showing the program flow of the calculation unit 10. The program shown in Figure 3 is built into the calculation unit 10. As an example, the selection of an electric control unit corresponding to an online pre-calculation type stabilization system will be described. The power system stabilization device 1 is not limited to those corresponding to an online pre-calculation type stabilization system. The power system stabilization device 1 operates and calculates according to the following procedure at predetermined cycles such as 30 seconds. Below, the operation of the power system stabilization device 1 will be described based on Figure 3.

[0043] (Step S1: Stability calculation) The calculation unit 10, using the stability calculation unit 11, calculates the stability for assumed target fault cases in the power system 9a, which includes synchronous generators 2-1, 2-2, 2-3 and renewable energy source 3. Assumed target fault cases include ground faults in transmission line 4, voltage drops and frequency drops in synchronous generator 2 due to overload, etc. The stability is calculated by transient stability calculation for assumed target fault cases based on state quantities at various points in the power system 9a measured by information collection devices 7-1, 7-2, 7-3, 7-4, 7-5, 7-6, and 7-7, as well as system configuration such as impedance and topology of pre-set transmission lines 4-1, 4-2, 4-3 and transformers 6-1, 6-2, 6-3, 6-4 (hereinafter sometimes referred to as branches), generator constants, and excitation control system information.

[0044] (Step S2: Determining stability / instability) The calculation unit 10 determines whether the power system 9a is stable or unstable based on the calculation results of the stability calculation unit 11. For example, the stability or instability of the power system 9a is determined based on whether or not there are any synchronous generators that lose synchronization (hereinafter sometimes referred to as "loose-synchronization generators") among the synchronous generators 2-1, 2-2, and 2-3. If there is one or more loose-synchronization generators, the power system 9a is determined to be unstable (NO in step S2), and the program proceeds to step S3. If there are no loose-synchronization generators, the power system 9a is determined to be stable (YES in step S2), and the program terminates. If the power system 9a is determined to be stable, electric control is not required.

[0045] (Step S3: Determining the scope to be reduced) The calculation unit 10 determines the range of the power system 9a to be reduced to a 1-unit, 2-load model using the reduced system model creation unit 12. As an example, in this embodiment, when representing the positional relationship of nodes and branches on the system, positions closer to the 500kV system are expressed as upper-level, and positions further away are expressed as lower-level. Figure 4 shows the program flow for determining the range to be reduced. The operation for determining the range to be reduced will be explained below according to the program flow shown in Figure 4.

[0046] (Step S31: Grouping of stable generators / unstable generators) The calculation unit 10 groups stable generators or unstable generators as follows, based on the stability calculation results from the stability calculation unit 11. The stable generator group consists of the generators included in the reduction target. • Generators that do not lose synchronization → Stable generator group • Generators that lose synchronization → Group of unstable generators

[0047] (Step S32: Determination of the starting node for reduction) The calculation unit 10 determines the starting node of the reduced system model (hereinafter sometimes referred to as the reduction starting node). The system including the stable generator group above the reduction starting node becomes the reduction target range, while the lower system including the unstable generator group is excluded from the reduction target range. The calculation unit 10 determines the reduction starting node according to the program flow shown in Figure 5, provided that the topology of the lower system is radial. Figure 5 shows the program flow for determining the reduction starting node.

[0048] As shown in the program flow for determining the reduction starting node in Figure 5, the calculation unit 10 sequentially moves the search point to a higher node, sets the nodes constituting the radiation system as reduction starting nodes, and searches for reduction starting nodes until all the out-of-sync generators are included below one of the reduction starting nodes.

[0049] (Step S33: Extraction of the out-of-sync locus) Next, the calculation unit 10 extracts the out-of-synchronization locus. An out-of-synchronization locus is a location where the phase angle fluctuates significantly. A location where the phase angle fluctuates above a predetermined reference value is called an out-of-synchronization locus. For example, if the phase difference angle between the primary and secondary sides of transformer 6 is above a predetermined reference value, then transformer 6 is considered an out-of-synchronization locus. For example, if the phase difference angle between the sending and receiving ends of transmission line 4 is above a predetermined reference value, then transmission line 4 is considered an out-of-synchronization locus. Out-of-synchronization locus of generators that are not the main cause of instability (generators that have lost synchronization due to the acceleration of other generators) is not necessary. As an example, in this embodiment, only the out-of-synchronization locus of generators that are the main cause of instability is treated as an out-of-synchronization locus.

[0050] Figure 6 shows the program flow for extracting the desynchronic locus. The operation of extracting the desynchronic locus will be explained below according to the program flow shown in Figure 6.

[0051] In step S331, the calculation unit 10 obtains the phase difference angle of each transmission line 4 and transformer 6 in the power system 9a based on the stability calculation result, and extracts branches that exceed a predetermined threshold (e.g., 180 degrees) as locus candidates.

[0052] Next, in step S332, the calculation unit 10 determines that the branch whose phase difference angle first exceeds the threshold is the first out-of-sync locus.

[0053] Next, the calculation unit 10 determines the second and subsequent out-of-sync locus in step S333. If there are multiple out-of-sync generators below each locus candidate, the calculation unit 10 determines it to be an out-of-sync locus because the selection of an electric control unit is required. Also, locus candidates that have the same out-of-sync generator as an already extracted out-of-sync locus below them are not determined to be out-of-sync locus. On the other hand, if there is only one out-of-sync generator below a locus candidate, there is no room for electric control selection, and therefore it is not determined to be an out-of-sync locus in this invention. These are treated as out-of-sync generators that do not belong to any out-of-sync locus.

[0054] Next, in step S334, the calculation unit 10 records the out-of-synchronization locus and the out-of-synchronization generators belonging to the lower levels of each out-of-synchronization locus as a pair. The number of out-of-synchronization locuses extracted here will become the number of reduction starting node groups, which will be described later.

[0055] (Step S34: Grouping of reduction starting nodes based on desync locus) The calculation unit 10 groups the reduction starting nodes based on the out-of-sync locus. When there are multiple reduction starting nodes, reducing reduction starting nodes belonging to different out-of-sync locuses as the same model may significantly degrade the accuracy of the reduction system model. Therefore, for reduction starting nodes belonging to different out-of-sync locuses, a separate reduction system model is created for each out-of-sync locus. In order to create a reduction system model for each out-of-sync locus, the reduction starting nodes are grouped based on the out-of-sync locus.

[0056] The calculation unit 10 determines the reduction starting node according to the program flow shown in Figure 7, based on the reduction starting node determined in step S32 and the desync locus extracted in step S33. Figure 7 shows the program flow for grouping reduction starting nodes based on desync locus.

[0057] As shown in the program flow for grouping reduction starting nodes based on the out-of-synchronization locus in Figure 7, the calculation unit 10 sequentially determines whether the reduction starting node and the out-of-synchronization locus contain the same out-of-synchronization generator, and includes the reduction starting node containing the same out-of-synchronization generator in the group of out-of-synchronization locus containing the same out-of-synchronization generator.

[0058] The calculation unit 10 creates a reduced system model for each of the reduction starting node groups determined here and selects an electric control unit. Note that reduction starting nodes that cannot be associated with a loss-of-synchronization locus (reduction starting nodes that include only loss-of-synchronization generators that do not belong to a loss-of-synchronization locus) are excluded from the electric control unit selection and are included in the reduction target range.

[0059] (Step S4: Creating a reduced system model) The calculation unit 10, using the reduced system model creation unit 12, reduces the systems above the reduction starting node to a 1-unit, 2-load model for each reduction starting node group within the reduction target range determined in step S3. Figure 8 shows an example of a reduced system model. The reduced system model is a multi-point interconnection model corresponding to the number of reduction starting nodes included in each reduction starting node group.

[0060] This reduced system model is based on a reduction method called the two-load method, and includes reduced branch reactances X1, X2, X3 and active power flow P. L2 Reactive power flow Q L2 These are each calculated and created through optimization calculations. The procedure for calculating the reduced branch reactances X1, X2, and X3 is shown below. The reduced branch reactances X1, X2, and X3 are calculated by performing optimization calculations on the objective function (Equation A) shown below.

number

[0061] However, the short-circuit impedances X1 and X2 when looking at the reduced system side from each reduction starting node are as shown in (Equation 1) and (Equation 2).

number

number

[0062] The reduced system short-circuit impedance obtained from the simulation is X S1_S , X S2_S Assuming this, the relative error ΔX of the short-circuit impedance between the reduced system and the actual system. S1 ΔX S2 This is as shown in (Equation 3) and (Equation 4).

number

number

[0063] The relative phase error Δθ between each reduction starting node is calculated by (Equation 5).

number

[0064] Relative error ΔQ of reactive power loss before and after reduction loss This is calculated by (Equation 6). However, the reactive power loss Q of the reduced system model is included. loss_S This calculation assumes that all reduced loads are located at the reduced generator terminals, similar to the two-load method.

number

[0065] Active power flow P L2 and reactive power flow Q L2 are calculated by performing an optimization calculation for the objective function (Equation B) shown below. [Number] ·····(Equation B)

[0066] When the reduced generator terminal is used as the phase reference (θt = 0), the intermediate node voltage V0 is calculated by Equation (7). [Number] ·····(Equation 7)

[0067] When the reduced generator terminal is used as the phase reference, the voltages V1 and V2 of the reduced starting nodes are calculated by Equation (8). [Number] ·····(Equation 8)

[0068] Therefore, the phase differences θ1 and θ2 between the reduced generator terminal and the reduced starting nodes derived from the reduced system model are as shown in Equation (9). [Number] ·····(Equation 9)

[0069] Let the phase difference between the reduced starting node and the reduced generator terminal be θ 1t , θ 2t . Then, the relative phase errors Δθ1 and Δθ2 of the reduced system model are as shown in Equation (10). [Number] ·····(Equation 10)

[0070] Regarding the absolute value of the reduced starting node voltage, V 1_S , V 2_SUsing this, the relative errors ΔV1 and ΔV2 of the reduced system model are calculated as shown in (Equation 11).

number

[0071] Next, the effect of creating a reduced system model will be explained using an example of a power system model when the stable generator group shown in Figure 9 is reduced. Figure 9 is an example in which the topology of the power system is transformed into a radial topology by the reduced system model. A radial topology refers to a shape that extends in two or more directions from a single point. A radial topology includes not only a star shape that extends in three or more directions from a single point, but also a shape that extends in two directions from a single point. Using this power system model, the output P1-jQ1 of the synchronized generator G1 is calculated from the power equation as shown in (Equation 12).

number

[0072] In the right-hand side of (Equation 12), the second term represents the renewable energy source, the third term represents the load included in the unstable generator group, the fourth term represents the generator included in the unstable generator group, and the fifth term represents the effect of the reduced load. Focusing on the impedance coefficients of each term, the denominator is the impedance from generator G1, which is the subject of the electric control effect evaluation, to the reduced generator GS. The numerator, on the other hand, is the impedance from the node where the elements of each term are connected to the reduced generator GS, along the route from generator G1 to the reduced generator GS.

[0073] By rearranging and simplifying (Equation 12), the P-δ curve for generator G1 is expressed by (Equation 13).

number

[0074] The second and fourth terms on the right-hand side of (Equation 13) represent the influence of renewable energy sources and synchronous generators. By setting these terms to zero, the influence of each generator's electric control on generator G1 can be evaluated. As described above, in the case of a radial system, it is possible to derive the formula for calculating the P-δ curve by a simple regularity based on the impedance relationship from generator G1 to reduced generator GS.

[0075] Equation 13 is used to evaluate the effect of the electric control of other generators on a single generator G1. To evaluate the stability of the power system, it is desirable to derive the P-δ curve calculation formula for other generators G2 to Gn, similar to generator G1, and evaluate the effect of electric control on each generator. The generator whose effect of electric control is being evaluated (corresponding to generator G1 in Equation 13) is sometimes called the base generator.

[0076] (Step S5: Select electric brake) The calculation unit 10, using the reduced system model created by the reduced system model creation unit 12, performs the electric control unit selection using the electric control unit selection unit 14. Figure 10 shows an example of the program flow related to electric control unit selection. The operation related to electric control unit selection will be explained below according to the program flow shown in Figure 10.

[0077] (Step S501: Assignment of reduction starting node group number) In step S3, if there are two or more reduction starting node groups, the calculation unit 10 determines which of the multiple reduction starting node groups will initiate the selection of the electric control unit. It compares the order of the timing of each loss of synchronization for each generator and assigns numbers to the reduction starting node groups in order of those that include the generator with the highest loss of synchronization priority (the generator that loses synchronization earlier). Starting with the reduction starting node groups with the lowest numbers, the unit selects the electric control units one by one.

[0078] (Step S502: Initial setting of the starting node group number for reduction) The calculation unit 10 sets an initial value for the counter in order to determine which reduction starting node group to use for selecting the electric control unit.

[0079] (Step S503: Selection of the starting node group for reduction) The calculation unit 10 selects a reduction starting node group for selecting the electric control unit.

[0080] (Step S504: Determining the stability / instability of the reduction starting node group) The calculation unit 10 determines whether the reduction starting node group subject to electric control selection is stable or unstable based on the stability calculated by the stability calculation unit 11. For example, the stability or instability of the reduction starting node group is determined based on whether or not there are synchronous generators that lose synchronization. If one or more generators belonging to the reduction starting node group lose synchronization, it is determined to be unstable; if there are no generators that lose synchronization, it is determined to be stable. If the reduction starting node group is determined to be unstable (YES in step S504), the program proceeds to step S505. If the reduction starting node group is determined to be stable (NO in step S504), the program proceeds to step S514.

[0081] (Step S505: Creating the P-δ curve) The calculation unit 10 calculates the P-δ curve of the out-of-sync generator included in the reduction starting node group using the P-δ curve calculation unit 13. At this time, the state variables (voltage, phase, active power, reactive power) used to create the P-δ curve are values ​​obtained from an arbitrary time cross-section of the transient stability calculation results.

[0082] Figure 11 shows an example of the timing for transient stability calculations when creating a P-δ curve. Assume there are three run-out generators, A, B, and C, and select a control unit from among them. The control timings for generators A, B, and C are all different. The control timing is pre-set for each generator. When selecting the first control unit, the P-δ curve is calculated based on the earliest control timing, for example, the state variable at a time cross-section of 1.15 seconds for generator A.

[0083] If generator C is selected as the first electric control unit, and stabilization cannot be achieved with just generator C, then a second electric control unit is selected. In the selection of the second electric control unit, the P-δ curve is calculated using the time section immediately after the electric control of the already selected generator C. In the selection of the second and subsequent electric control units, the P-δ curve is calculated using the time section immediately after the electric control of the generator with the latest electric control timing among the already selected electric control units. For example, if generator C is selected as the first unit, generator B as the second unit, and then a third electric control unit is selected, the P-δ curve is calculated using the state variables in the time section immediately after the electric control of generator C, which has the latest electric control timing.

[0084] In conventional methods for creating P-δ curves, the state variables such as voltage and phase used in calculations are treated as fixed values. However, these state variables have dynamic characteristics and actually change over time. To calculate a more accurate P-δ curve, it is desirable to reproduce the dynamic characteristics of these state variables.

[0085] In P-δ curve calculations, it is common to use a fixed value as the absolute value of the voltage. In power systems, a sharp drop in voltage occurs due to the instability of the power system immediately after a generator loses synchronism. If the sharply dropped voltage is used in the P-δ curve calculation, it is not possible to calculate an accurate P-δ curve, making it difficult to reflect the dynamic characteristics of the voltage in the P-δ curve.

[0086] On the other hand, since the phase is given as a relative value to the base generator, the movement immediately after losing synchronism, unlike voltage, does not significantly degrade the accuracy of the P-δ curve calculation. Therefore, the dynamic characteristics of the phase difference are reflected in the P-δ curve calculation using the transient stability calculation results.

[0087] As an example of a means of reflecting the dynamic characteristics of the phase difference in the P-δ curve, Figure 12 shows the program flow for phase difference correction of the P-δ curve. The calculation unit 10 performs phase difference correction of the P-δ curve according to the program flow shown in Figure 12. The calculation unit 10 successively increases the internal phase difference angle δbase of the base generator, and when δbase becomes greater than or equal to the internal phase difference angle of the base generator in the P-δ curve calculation cross section, it obtains the time t until the internal phase angle of the base generator reaches δbase based on the transient stability calculation result, and calculates the difference between the internal phase angle δbase of the base generator and the internal phase difference angle δk of each generator at time t, and the difference between the internal phase angle δbase of the base generator and the voltage phase θk of the load.

[0088] Here, the transient stability calculation result refers to the calculation result under non-electrostatic control when the first electrostatic control unit is selected, and the calculation result under electrostatic control when the first unit is selected when the second electrodeposition unit is selected. Since the P-δ curve is calculated by arbitrarily changing the internal phase difference angle of the base generator, the phase angles of generators other than the base generator and loads are obtained from the transient stability calculation result, corresponding to the internal phase difference angle of the base generator.

[0089] The calculation unit 10 calculates the P-δ curve for each out-of-synchronization generator included in the reduction starting node group, assuming that each out-of-synchronization generator is the base generator.

[0090] (Step S506: Calculation of acceleration energy and deceleration energy) The calculation unit 10 calculates the acceleration energy (hereinafter sometimes referred to as AE) and deceleration energy (hereinafter sometimes referred to as DE) for each P-δ curve. Figure 13 shows a diagram illustrating the calculation of acceleration energy and deceleration energy based on the P-δ curve.

[0091] In Figure 13, t0 is the fault occurrence time, t1 is the fault removal time, and t2 is the electric control implementation time. δ0, δ1, and δ2 are the internal phase difference angles of the base generator corresponding to each time. In Figure 13, the area between the curve from δ0 to δ1 [2] and Pm is the AE, and the area between the curve from δ1 to δ2 [3] and Pm is the DE before electric control. AE and DE are directly calculated using the transient stability calculation results when electric control is not applied.

[0092] The curve [4] representing the P-δ curve when each generator is electrically controlled is calculated by setting the active power output and reactive power output of the generator to be electrically controlled to 0 in the P-δ curve calculation formula. The internal phase difference angle of a runaway generator where Pe=Pm is taken as δ3, and the area between the curve [4] from δ2 to δ3 and Pm is calculated as DE after electric control.

[0093] (Step S507: Determine if there are any electronically controlled targets where DE > AE) The calculation unit 10 compares the acceleration energy AE and deceleration energy DE calculated from the P-δ curve and determines whether there are any electrically controlled objects for all base generators where DE > AE. If it is determined that there are electrically controlled objects where DE > AE (YES in step S507), the program proceeds to step S508. If it is determined that there are no electrically controlled objects where DE > AE (NO in step S507), the program proceeds to step S509.

[0094] Figure 14 shows a diagram illustrating the comparison of acceleration energy AE and deceleration energy DE after electric control. In Figure 14, generators B and C are the only generators for which DE > AE for all base generators. Based on the evaluation using the P-δ curve, it is determined that all generators can be stabilized by electric control of either generator B or generator C; therefore, one of these two generators is selected as the electric control unit.

[0095] (Step S508: Selection of the generator with the minimum output) In step S507, if it is determined that there is an electric control target for all base generators where DE > AE, the calculation unit 10 determines that controlling any of the electric control targets where DE > AE will contribute significantly to stabilization, and therefore selects the generator with the lowest output among them as the electric control unit.

[0096] (Step S509: Calculation of the electric braking effect) In step S507, if it is determined that there are no electrically controlled generators for which DE > AE for all base generators, it is determined that the system cannot be stabilized by electrically controlling just one electrically controlled generator. In order to select the generator with the greatest electric control effect as the electrically controlled generator, the calculation unit 10 calculates the electric control effect. Figure 15 shows an example of how the electric control effect is calculated. For each base generator, the calculation unit 10 calculates the difference area of ​​the P-δ curve before and after electric control as the electric control effect SE.

[0097] (Step S510: Select the generator that maximizes the sum of the electric braking effects SE) The calculation unit 10 calculates the sum of the electric control effect SE for each base generator for each electric control target, and selects the generator with the largest sum of electric control effect SE as the electric control unit. Figure 16 shows an example illustrating the comparison of electric control effect SE. In Figure 16, generator C is selected as the electric control unit because the sum of electric control effect SE is maximized when generator C is electrically controlled.

[0098] (Step S511: Calculation of transient stability after selecting electric control) The calculation unit 10 adds one generator selected in step S508 or step S510 as an electric control unit, and the stability calculation unit 11 performs transient stability calculations.

[0099] (Step S512: Determining stability) The calculation unit 10 determines whether the power system is stable or unstable based on the calculation results of the stability calculation unit 11. For example, the presence or absence of a step-out generator is used as a criterion to determine whether the power system is stable or unstable. If one or more step-out generators are present, it is determined to be unstable; if no step-out generators are present, it is determined to be stable. If it is determined to be unstable (NO in step S512), the program proceeds to step S513. If it is determined to be stable (YES in step S512), the program related to the selection of the electric control unit terminates.

[0100] (Step S513: Selection of additional electric control units and exclusion from base generators) In step S512, if it is determined that the selected generator would be unstable even with electric control, the calculation unit 10 selects an additional electric control unit. At this time, generators whose step loss is prevented by the electric control units selected so far are excluded from the candidates for electric control and the base generators.

[0101] (Step S514: Determining whether all reduction origin node groups have been evaluated) In step S34, if multiple reduction starting node groups are created, the calculation unit 10 selects an electric control unit from each reduction starting node group in the order determined in step S501. If it determines that all reduction starting node groups have been evaluated (YES in step S514), the calculation unit 10 returns to the first reduction starting node group and proceeds to step S503 to select an additional electric control unit. If it does not determine that all reduction starting node groups have been evaluated (NO in step S514), the calculation unit 10 changes the reduction starting node group and proceeds to step S503.

[0102] Through the above operations, the power system stabilization device 1 compares the synchronous generators 2-1, 2-2, and 2-3 and the renewable energy source 3, which are both included as targets for electric control selection in a power system 9a, based on an index of stability, and selects an appropriate electric control device.

[0103] The above describes the operation of the power system stabilization device 1 according to this embodiment.

[0104] [1-3. Effects] (1) According to this embodiment, the power system stabilization device 1 includes a stability calculation unit 11, a reduced system model creation unit 12, a P-δ curve calculation unit 13, and a power control unit selection unit 14. The stability calculation unit 11 calculates the stability of the power system 9, including the synchronous generator 2 and the renewable energy source 3, in the event of a failure. The stability is calculated for assumed failure cases. If the stability calculated by the stability calculation unit 11 is determined to be unstable, the reduced system model creation unit 12 extracts stable and unstable generators from the synchronous generator 2 and the renewable energy source 3, sets one or more nodes as reduction starting nodes so that the topology of the power system 9 including the unstable generators becomes radial, reduces the power system 9 including the higher-level stable generators from the set reduction starting nodes, and creates a reduced system model. If the stability calculated by the stability calculation unit 11 is determined to be unstable, the P-δ curve calculation unit 13 extracts the synchronous generators 2 that will lose synchronization based on the reduced system model created by the reduced system model creation unit 12, and calculates a P-δ curve for each synchronous generator 2 that will lose synchronization, showing the relationship between the internal phase difference angle and the active power output. The electric control unit 14 calculates the electric control effect based on the P-δ curve calculated by the P-δ curve calculation unit 13, based on at least one of the acceleration energy and deceleration energy generated when the renewable energy power source 3 or the synchronous generator 2 that will lose synchronization is electrically controlled, and selects the target to be electrically controlled from among the synchronous generators 2 and the renewable energy power source 3 based on the calculated electric control effect. The power system stabilization device 1 includes a stability calculation unit 11, a reduced system model creation unit 12, a P-δ curve calculation unit 13, and a power control unit selection unit 14. Therefore, in a power system 9 that includes both a synchronous generator 2 and a renewable energy source 3, the power system stabilization device can provide a fair and efficient way to control the renewable energy source 3 and the synchronous generator 2.

[0105] The reduced system model creation unit 12 reduces the power system 9 so that its topology is radial and creates a reduced system model. Therefore, based on the impedance from the synchronous generator 2 and renewable energy source 3 to the generator in the reduced system model, the P-δ curve can be calculated using a simple calculation formula.

[0106] The electric control unit 14 calculates the electric control effect based on the P-δ curve calculated by the P-δ curve calculation unit 13, and based on at least one of the acceleration energy and deceleration energy generated when the renewable energy source 3 or the synchronous generator 2 that is out of step is electrically controlled. Based on the calculated electric control effect, it selects the target to be electrically controlled from the synchronous generator 2 and the renewable energy source 3. This ensures that the electric control of the renewable energy source 3 and the synchronous generator 2 is carried out fairly and efficiently, and that stable electric control is performed in the power system 9.

[0107] (2) According to this embodiment, the P-δ curve calculation unit 13 calculates a P-δ curve individually for the synchronous generators 2 included in the portion of the power system 9 that is outside the scope of the reduction

[0108] Since the P-δ curves are calculated for each synchronous generator 2 and renewable energy source 3 under individual electric control, it is possible to fairly and efficiently evaluate the electric control not only for the synchronous generator 2 but also for the renewable energy source 3.

[0109] (3) According to this embodiment, the P-δ curve calculation unit 13 calculates the P-δ curve using state quantities as parameters, based on the stability calculated by the stability calculation unit 11 and state quantities relating to at least voltage, phase, active power, and reactive power at any time cross-section after fault removal. As a result, the P-δ curve at each time cross-section is calculated with high accuracy, and the effect of electric control on the synchronous generator 2 and renewable energy power source 3 can be evaluated with high accuracy. This enables fair and efficient electric control in the power system 9.

[0110] (4) According to this embodiment, the P-δ curve calculation unit 13 calculates the phase difference between the base generator and the other synchronous generators 2, renewable energy sources 3, and loads that are losing synchronism, based on the stability calculated by the stability calculation unit 11, the internal phase difference angle of the synchronous generator 2 that is losing synchronism, and the time-series changes in the terminal voltage phases of the renewable energy source 3 and the load, in accordance with the change in the internal phase difference angle of the base generator that is the subject of the P-δ curve calculation, and calculates the P-δ curve using the phase difference as a parameter, so that the P-δ curve is calculated with high accuracy and the effect of electric control on the synchronous generator 2 and renewable energy source 3 can be evaluated with high accuracy. As a result, fair and efficient electric control can be performed in the power system 9.

[0111] (5) According to this embodiment, the reduced system model creation unit 12 extracts the out-of-sync synchronous generators 2 belonging to the reduction starting node set in the reduced system model created so that the topology is radial, extracts the out-of-sync locus extracted based on the branch phase difference angle and the out-of-sync synchronous generators 2 belonging to each out-of-sync locus, and when the out-of-sync synchronous generators 2 belonging to the reduction starting node and the out-of-sync synchronous generators 2 belonging to the out-of-sync locus match, the reduction starting node is newly grouped by out-of-sync locus, and a reduced system model is created for each newly grouped group of reduction starting nodes, so that the target for power control can be efficiently selected from the synchronous generators 2 and renewable energy sources 3 based on the reduced system model created for each newly grouped group of reduction starting nodes. As a result, an appropriate synchronous generator 2 and renewable energy source 3 are selected as the target for power control, and fair and efficient power control can be performed in the power system 9.

[0112] (6) According to this embodiment, for each synchronous generator 2 that loses synchronism, the electric control unit 14 calculates the electric control effect from the difference between the energy calculated from the output before electric control of the renewable energy source 3 or the synchronous generator 2 that loses synchronism (excluding the base generator that is the subject of the P-δ curve calculation) and the energy calculated from the output after electric control, based on the P-δ curve calculated by the P-δ curve calculation unit 13. Based on the calculated magnitude of the electric control effect for each renewable energy source 3 or synchronous generator 2 that loses synchronism, the electric control unit 14 selects the electric control target. This makes it possible to accurately evaluate the impact of electric control on the synchronous generator 2 and renewable energy source 3. This makes it possible to perform fair and efficient electric control in the power system 9.

[0113] (7) According to this embodiment, the electric control unit 14 calculates the deceleration energy and acceleration energy when electric control is applied to each renewable energy source 3 or synchronous generator 2 that loses synchronism, based on the P-δ curve calculated by the P-δ curve calculation unit 13, for each renewable energy source 3 and synchronous generator 2 that loses synchronism, excluding the base generator which is the subject of the P-δ curve calculation. The electric control unit 14 selects the renewable energy source 3 or synchronous generator 2 that loses synchronism, in which the deceleration energy exceeds the acceleration energy, as the target for electric control. As a result, electric control of the synchronous generator 2 and renewable energy source 3 can be performed without losing synchronism. This enables fair and efficient electric control in the power system 9.

[0114] [2. Other Embodiments] While embodiments, including variations, have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents. The following is an example.

[0115] (1) In the above embodiment, the reduced system model was assumed to be a 1-unit, 2-load model. However, the shape of the reduced system model is not limited to a 1-unit, 2-load model. The shape of the reduced system model can be any shape having a radial topology.

[0116] (2) In the above embodiment, the reduced system model uses a conditional branch to select between electric control selection based on a comparison of acceleration energy and deceleration energy in step S508 and electric control selection based on a comparison of electric control effects in steps S509 and S510. However, the reduced system model may also perform only one of the electric control selections: electric control selection based on a comparison of acceleration energy and deceleration energy, or electric control selection based on a comparison of electric control effects.

[0117] (3) In the above embodiment, the reduced system model selects the generator with the minimum output as the electric control unit in step S508 by electric control selection based on a comparison of acceleration energy and deceleration energy. However, the selection criteria for the electric control unit in the reduced system model are not limited to the above. The selection of the electric control unit in the reduced system model may be made by other selection criteria.

[0118] (4) In the above embodiment, the electric braking effect was calculated by calculating the difference in acceleration energy and deceleration energy before and after electric braking in step S506. However, the calculation of the electric braking effect is not limited to the above. The electric braking effect may be calculated by, for example, only the difference in deceleration energy.

[0119] (5) In the above embodiment, the selection of an electric control unit by comparing the electric control effects was performed by comparing the electric control effects in step S509 and selecting the generator with the maximum electric control effect in step S510. However, the criteria for selecting an electric control unit by comparing the electric control effects are not limited to the above. The selection of an electric control unit by comparing the electric control effects may be based on, for example, the electric control sensitivity calculated by (electric control effect / generator output). [Explanation of Symbols]

[0120] 1...Power system stabilization device 2, 2-1, 2-2, 2-3... Synchronous generators 3. Renewable energy sources 4, 4-1, 4-2, 4-3... Power transmission lines 5, 5-1, 5-2, 5-3, 5-4... Circuit breakers 6, 6-1, 6-2, 6-3, 6-4... Transformers 7, 7-1, 7-2, 7-3, 7-4, 7-5, 7-6, 7-7... Information gathering device 8. Fault detection device 9, 9a, 9b...Power system 10... Arithmetic section 11... Stability calculation section 12. Reduced System Model Creation Section 13. P-δ curve calculation section 14. Electrical Control System Selection Section 20.. Control Unit

Claims

1. A stability calculation unit that calculates the stability of a power system including synchronous generators and renewable energy sources in the event of a failure, If the stability calculated by the stability calculation unit is determined to be unstable, stable and unstable generators are extracted from the synchronous generators. A reduced system model creation unit sets one or more nodes as reduction starting nodes so that the topology of the power system including the unstable generator is radial, reduces the power system including the stable generator above the set reduction starting nodes, and creates a reduced system model. If the stability calculated by the stability calculation unit is determined to be unstable, the P-δ curve calculation unit extracts the synchronous generators that are out of step based on the reduced system model created by the reduced system model creation unit, and calculates a P-δ curve showing the relationship between the phase angle and the output active power for each of the synchronous generators that are out of step. Based on the P-δ curve calculated by the P-δ curve calculation unit, the electric control effect is calculated based on at least one of the acceleration energy and deceleration energy generated when the renewable energy power source or the synchronous generator that is out of synchronism is electrically controlled, and based on the calculated electric control effect, the electric control unit selects the target to be electrically controlled from the synchronous generator and the renewable energy power source. A power grid stabilization device having the following features.

2. The P-δ curve calculation unit is, Based on the radial system model created by the reduced system model creation unit and the portion of the power system that falls outside the reduction range of the reduced system model, the P-δ curve is calculated when the synchronous generator and the renewable energy power source included in the portion of the power system that falls outside the reduction range of the reduced system model are individually controlled. The power grid stabilization device according to claim 1.

3. The P-δ curve calculation unit is, Based on the stability calculated by the stability calculation unit and state variables relating at least voltage, phase, active power, and reactive power at any time cross-section after fault removal, a P-δ curve is calculated using the state variables as parameters. The power grid stabilization device according to claim 2.

4. The P-δ curve calculation unit is, Based on the stability calculated by the stability calculation unit, the internal phase difference angle of the synchronous generator that is losing synchronization, and the time-series changes in the terminal voltage phases of the renewable energy power source and the load, The phase difference between the base generator and other synchronous generators that are out of synchronism, the renewable energy power source, and the load is calculated according to the change in the internal phase difference angle of the base generator that is the subject of the P-δ curve calculation, and the P-δ curve is calculated using the phase difference as a parameter. The power grid stabilization device according to claim 2.

5. The aforementioned reduced system model creation unit, In the reduced system model created such that the topology is radial, the synchronous generators that are out of step belong to the reduction starting node set, Based on the branch phase difference angle, the out-of-synchronization locus and the out-of-synchronization synchronous generators belonging to each of the out-of-synchronization locus are extracted. When the synchronous generators that lose synchronization belonging to the reduction starting node and the synchronous generators that lose synchronization belonging to the loss-of-synchronization locus coincide, the reduction starting nodes are newly grouped by loss-of-synchronization locus, and the reduction system model is created for each newly grouped group of reduction starting nodes. The power grid stabilization device according to claim 1.

6. The aforementioned electric control unit is, For each synchronous generator that loses synchronization, the electric control effect is calculated from the difference between the energy calculated from the output before electric control of the renewable energy power source or the synchronous generator that loses synchronization (excluding the base generator that is the subject of the P-δ curve calculation) and the energy calculated from the output after electric control, based on the P-δ curve calculated by the P-δ curve calculation unit. Based on the calculated magnitude of the electric control effect for each renewable energy source or the synchronous generator that loses synchronization, the target of electric control is selected. The power grid stabilization device according to claim 1.

7. The aforementioned electric control unit is, For each synchronous generator that loses synchronization, based on the P-δ curve calculated by the P-δ curve calculation unit, The deceleration energy and acceleration energy when electrically controlled are calculated for each of the renewable energy power sources, excluding the base generator which is the subject of the P-δ curve calculation, and for each of the synchronous generators that lose synchronization. Select the renewable energy power source or the synchronous generator that loses synchronization, in which the deceleration energy exceeds the acceleration energy, as the target for electric control. The power grid stabilization device according to claim 1.

8. A stability calculation step for calculating the stability of a power system including synchronous generators and renewable energy sources in the event of a failure, If the stability calculated in the stability calculation step is determined to be unstable, stable and unstable generators are extracted from the synchronous generators. A reduced system model creation step involves setting one or more nodes as reduction starting nodes so that the topology of the power system including the unstable generator is radial, reducing the power system including the stable generator above the set reduction starting nodes, and creating a reduced system model. If the stability calculated in the stability calculation step is determined to be unstable, the P-δ curve calculation step involves extracting the synchronous generators that will lose synchronization based on the reduced system model created in the reduced system model creation step, and calculating a P-δ curve showing the relationship between the phase angle and the output active power for each of the synchronous generators that will lose synchronization. A control device selection step in which, based on the P-δ curve calculated in the P-δ curve calculation step, the control effect is calculated based on at least one of the acceleration energy and deceleration energy generated when the renewable energy power source or the synchronous generator that is out of synchronism is electrically controlled, and based on the calculated control effect, the target to be electrically controlled is selected from the synchronous generator and the renewable energy power source. A computer program for a power grid stabilization device having the following features.

9. A stability calculation procedure for calculating the stability of a power system including synchronous generators and renewable energy sources in the event of a failure, If the stability calculated by the stability calculation procedure is determined to be unstable, stable and unstable generators are extracted from the synchronous generators. A procedure for creating a reduced power system model involves setting one or more nodes as reduction starting nodes so that the topology of the power system including the unstable generator is radial, reducing the power system including the stable generator above the set reduction starting nodes, and creating a reduced power system model. If the stability calculated by the stability calculation procedure is determined to be unstable, the P-δ curve calculation procedure extracts the synchronous generators that lose synchronization based on the reduced system model created by the reduced system model creation procedure, and calculates a P-δ curve showing the relationship between the phase angle and the output active power for each of the synchronous generators that lose synchronization. A control device selection procedure which involves calculating the electric control effect based on the P-δ curve calculated by the P-δ curve calculation procedure, based on at least one of the acceleration energy and deceleration energy generated when the renewable energy power source or the synchronous generator that is out of synchronism is electrically controlled, and selecting the target to be electrically controlled from the synchronous generator and the renewable energy power source based on the calculated electric control effect, A method for stabilizing a power grid.

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