Power system stabilizer and power system stabilizing method

Abstract

To provide an index and a power control algorithm using the same capable of performing an equal evaluation of the stabilizing effect against transient voltage drops by power control of synchronous generators and renewable energy power sources.SOLUTION: The power system stabilizer for identifying a power control target for which stabilization control is implemented in the event of a fault in a power system includes: an electricity control candidate determination unit that determines power control candidates of synchronous generators and renewable energy power sources based on the results of transient stability calculations for the power systems under assumed fault conditions; a transient voltage drop determination unit that determines transient voltage drops based on the transient stability calculation results; a transient voltage drop busbar identification unit that identifies transient voltage drop buses based on the transient stability calculation results; a sensitivity calculation unit that calculates the sensitivity from the transient voltage drop improvement amount at the transient voltage drop bus for the power control; and a transient voltage drop countermeasures planning unit that selects the power control candidates based on the sensitivity.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a power system stabilization device and a power system stabilization method for maintaining the stability (stability, voltage) of a power system. [Background technology]

[0002] When a fault (fault) occurs in a power system due to a lightning strike or other cause, the output of some synchronous generators (SG) may become unstable. If effective measures are not taken to prevent this instability, the number of unstable synchronous generators will increase over time, and this could ultimately lead to a major blackout.

[0003] To address the above-mentioned problems, conventional power system stabilizers have maintained the transient stability of a power system by isolating unstable synchronous generators from the power system in the event of a fault, i.e., by limiting power supply (shunting). For example, the power system stabilizer described in Non-Patent Document 1 uses numerical simulations to calculate in advance which synchronous generators to shut down in order to maintain transient stability in the event of a contingency fault in the power system, and then performs stabilization control to shut down those synchronous generators when the contingency fault actually occurs. This power system stabilizer aims to maintain transient stability by first shutting down the synchronous generators with the largest internal phase difference angle in the event of a fault. Note that stabilization control does not only involve the above-mentioned shedding, but also includes methods of suppressing or stopping generator output. However, in the following, the term "shunting" will be used to refer to both suppressing and stopping generator output.

[0004] On the other hand, in recent years, in order to reduce CO2 emissions, the introduction of renewable energy sources such as solar power generation and wind power generation has been actively promoted as an alternative to synchronous generators such as thermal power generation, and the proportion of synchronous generators in the power system is on a downward trend.However, as the proportion of synchronous generators decreases, the inertia and voltage maintenance capacity of the power system, which were previously handled by synchronous generators, decreases, which may result in a decrease in transient stability (transient stability and transient voltage).

[0005] Furthermore, a reduction in the number of synchronous generators means a reduction in the stabilization means in conventional power system stabilizers. Because renewable energy power sources do not have the internal phase difference angle that is an indicator for selecting generators to be sheared in conventional power system stabilizers, conventional power system stabilizers cannot select renewable energy power sources as targets for shearing. This could make it difficult for conventional power system stabilizers to maintain transient stability, or could increase the total amount of shearing required to maintain transient stability (increasing the cost required to restore from shearing).

[0006] To address the above-mentioned issues, adding renewable energy sources, which are expected to be introduced in increasing numbers in the future, to the list of candidates for power control will increase the possibility of maintaining transient stability and is expected to reduce the total amount of power control required for stabilization (reducing the costs required to recover from power control).

[0007] In this regard, Patent Document 1 is known as an invention relating to a power system stabilization device that includes renewable energy power sources as candidates for power control. Patent Document 1 aims to provide a power system stabilization device that can efficiently ensure the stability of the power system by selecting renewable energy power generation devices (renewable energy power sources) whose output will be reduced or stopped, and describes the power system stabilization device as including: "a stability calculation unit 11 that calculates stability for a predicted target failure case; an acceleration tendency synchronous generator extraction unit 12 that extracts one or more synchronous generators 4 with an acceleration tendency; a sensitivity calculation unit 13 that calculates the deceleration sensitivity of the acceleration tendency synchronous generator 6 when the output of the renewable energy power generation device 6 is reduced by a first reduction amount P1; a renewable energy reduction amount addition unit 14 that determines a total output reduction amount P3 of the extracted renewable energy power generation devices 6 that is determined to have stable stability; and a reduction target determination unit 15 that determines the renewable energy power generation devices 6 whose output will be reduced." [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 2020-96472 [Non-patent literature]

[0009] [Non-Patent Document 1] Hiroshi Yoshida, Ryuji Tate, Koya Takafuji, Hironori Imaeda, Masaru Takeishi, Hiroyuki Taguchi, and Kenichiro Kusaba: "Development of an Integrated Online Power System Stabilization System (ISC) for Next-Generation Grids," Journal of Electrical Engineering B, Vol. 137, No. 6, pp. 434-445 (2017) Summary of the Invention [Problem to be solved by the invention]

[0010] Patent Document 1 describes a method in which, in a power system where a large number of renewable energy power sources are connected and the number of operating synchronous generators is small, if a synchronous generator is powered down in the event of a fault or the like, the power system may become unstable. The method expresses the stabilizing effect of power control of renewable energy power sources as sensitivity, and based on that sensitivity, selects renewable energy power sources to be powered down in preference to synchronous generators, and selects synchronous generators to be powered down when power control of renewable energy power sources alone is insufficient.

[0011] However, depending on the area where the failure occurs, it is possible that the proportion of renewable energy sources in the power system is small, or that there are few renewable energy sources that have a high stabilizing effect through shearing control.In such cases, the method of Patent Document 1, which selects renewable energy sources to be sheared in preference to synchronous generators, may result in problems such as an increase in the total amount of shearing required for stabilization (increased costs required to recover from shearing control), adverse effects on the system due to excessive shearing control, and an increase in the amount of calculation required to select shearing control devices.

[0012] Therefore, a method is needed to prioritize the selection of synchronous generators or renewable energy sources to be shedding, based on the stabilizing effect of shedding, regardless of the proportion of renewable energy sources in the power system. This can result in not only a decrease in transient stability but also transient voltage sag. Furthermore, if an attempt is made to improve transient voltage sag as well as transient stability using an index used to improve transient stability, it may be impossible to select the appropriate generators to be shedding, resulting in an increase in the amount of shedding or inability to improve transient voltage sag.

[0013] In light of the above, the problem that the present invention aims to solve is to provide an index that can uniformly evaluate the stabilization effect against transient voltage drops caused by the shedding of synchronous generators and renewable energy power sources, either after transient stability measures have been formulated or before transient stability measures have been formulated, and a shedding control algorithm that uses the index. [Means for solving the problem]

[0014] In view of the above, the present invention provides "a power system stabilization device that determines targets for power control that perform stabilization control when a fault occurs in a power system, depending on stability in the event of a contingency in the power system including synchronous generators and renewable energy power sources, the power system stabilization device comprising: a power control candidate determination unit that determines candidates for power control of synchronous generators and renewable energy power sources based on transient stability calculation results in the event of a contingency in the power system; a transient voltage sag determination unit that determines a transient voltage sag based on the transient stability calculation results; a transient voltage sag bus identification unit that identifies a transient voltage sag bus based on the transient stability calculation results; a sensitivity calculation unit that calculates sensitivity from the amount of transient voltage sag improvement at the transient voltage sag bus with respect to the power control of the power control candidate and the active power output deviation of the power control candidate; and a transient voltage sag countermeasure planning unit that selects the power control candidate as a target for power control depending on the sensitivity."

[0015] Furthermore, the present invention provides a "power system stabilization method using a computer to determine targets for power control to be subjected to stabilization control in the event of a fault in the power system, depending on stability in the event of a contingency fault in the power system including synchronous generators and renewable energy power sources, wherein the calculation unit of the computer sequentially executes a power control candidate determination step of determining candidates for power control of synchronous generators and renewable energy power sources based on transient stability calculation results in the event of a contingency fault in the power system, a transient voltage dip determination step of determining a transient voltage dip based on the transient stability calculation results, a transient voltage dip bus identification step of identifying a transient voltage dip bus based on the transient stability calculation results, a sensitivity calculation step of calculating sensitivity from the transient voltage dip improvement amount of the transient voltage dip bus relative to the power control of the power control candidate and the active power output deviation of the power control candidate, and a transient voltage dip countermeasure planning step of selecting the power control candidate as a target for power control in accordance with the sensitivity." [Effects of the Invention]

[0016] According to the present invention, the stabilization effect of shearing control of synchronous generators and renewable energy power sources can be evaluated in the same way, and at least one of the synchronous generators or renewable energy power sources can be selected as the shearing control source in order of the stabilization effect. This makes it possible to improve transient stability (transient stability and transient voltage) regardless of the proportion of renewable energy power sources in the power system, and reduce the total amount of shearing control required for stabilization (the cost required to recover from shearing control). [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a diagram showing an example of the functional configuration of a power system stabilizing device 1 according to a first embodiment of the present invention. [Figure 2] 1 is a diagram showing an example of the hardware configuration of a power system stabilization device 1 according to a first embodiment and an example of the power system configuration; [Figure 3] FIG. 2 is a diagram showing programs held in a program database DB20. [Figure 4] FIG. 10 is a diagram showing an example of system configuration data D11. [Figure 5] FIG. 10 is a diagram showing an example of systematic measurement data D12. [Figure 6] FIG. 10 is a diagram showing an example of system model data D13. [Figure 7] FIG. 10 is a diagram showing an example of contingency data D14. [Figure 8] FIG. 10 is a diagram showing an example of threshold data D15. [Figure 9] FIG. 10 is a diagram showing an example of power control constraint data D16. [Figure 10] FIG. 10 is a diagram showing an example of sensitivity calculation setting data D17. [Figure 11] 1 is a diagram showing an overall flow of processing of a power system stabilizing device 1 according to a first embodiment. [Figure 12] FIG. 12 is a diagram showing detailed processing content of processing step S23 in FIG. 11. [Figure 13A] FIG. 12 is a diagram showing detailed processing content of processing step S25 in FIG. 11. [Figure 13B] FIG. 12 is a diagram showing detailed processing content of processing step S25 in FIG. 11. [Figure 14] 12 is a diagram showing an image of the definition of the numerator and denominator of voltage sensitivity in processing step S27 of FIG. 11. [Figure 15] 12 is a diagram showing a detailed flow of the power control selection process for the transient voltage drop countermeasure in processing step S28 of FIG. 11. [Figure 16] FIG. 12 is a diagram showing an image of selecting electrical control as a measure against transient voltage drop in processing step S28 of FIG. 11. [Figure 17] FIG. 4 is a diagram showing an example of a result display on the display unit 4. [Figure 18] FIG. 4 is a diagram showing an example of a result display on the display unit 4. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. [Example]

[0019] First, an example of the functional configuration of a power system stabilizing device 1 according to a first embodiment of the present invention will be described with reference to FIG.

[0020] In FIG. 1, the power system stabilization device 1, which is configured as a computer, is configured from an input database DB1 that stores input data D1 held in advance by a power system operator or planner, a calculation unit 2 that determines stabilization control commands for the power system based on the input data D1, an output database DB2 that stores output data D2, which is the calculation result of the calculation unit 2, and a display unit 4, which is an example of an output unit that displays the contents of the input data D1 and the output data D2.

[0021] The control device 3 receives the control command determined by the calculation unit 2, and transmits a control command (power control command) to the generator when a contingency fault (contingency fault) occurs in the power system.

[0022] The input database DB1 that stores the input data D1 is composed of a system configuration database DB11 that holds system configuration data D11, a system measurement database DB12 that holds system measurement data D12, a system model database DB13 that holds system model data D13, a contingency database DB14 that holds contingency data D14, a threshold database DB15 that holds threshold data D15, a shearing control constraint database DB16 that holds shearing control constraint data D16, and a sensitivity calculation setting database DB17 that holds sensitivity calculation setting data D17.

[0023] If the processing content of the calculation unit 2 is expressed functionally, it can be said to be composed of the functions of an analysis cross section creation unit 21, a transient stability calculation unit 22, a power control candidate determination unit 23, a transient stability countermeasure planning unit 24, a transient voltage drop determination unit 25, a transient voltage drop bus identification unit 26, a voltage sensitivity calculation unit 27, and a transient voltage drop countermeasure planning unit 28, and the processing is performed in this order.

[0024] The output database DB2 for storing the output data D2 includes an analysis cross section database DB21 that holds analysis cross section data D21 that is the result of the analysis cross section creation unit 21, a transient stability calculation result database DB22 that holds transient stability calculation result data D22 that is the result of the transient stability calculation unit 22, a power control candidate determination result database DB23 that holds power control candidate determination result data D23 that is the result of the power control candidate determination unit 23, and a transient stability measure database DB2 that holds transient stability measure data D24 that is the result of the transient stability measure planning unit 24. 4. It is composed of a transient voltage drop determination result database DB25 which holds transient voltage drop determination result data D25 which is the result of the transient voltage drop determination unit 25, a transient voltage drop bus database DB26 which holds transient voltage drop bus data D26 which is the result of the transient voltage drop bus identification unit 26, a sensitivity calculation result database DB27 which holds sensitivity calculation result data D27 which is the result of the voltage sensitivity calculation unit 27, and a transient voltage drop countermeasure database DB28 which holds transient voltage drop countermeasure data D28 which is the result of the transient voltage drop countermeasure planning unit 28.

[0025] Fig. 2 is a diagram showing an example of the hardware configuration of the power system stabilization device 1 and an example of the power system configuration of the embodiment 1. The upper part of Fig. 2 shows an example of the hardware configuration of the power system stabilization device 1 configured by a computer, and the lower part shows an example of the configuration of the power system that is the object of control.

[0026] The power system stabilizing device 1 includes various input databases DB11 to DB17, a program database DB20, various output databases DB21 to DB28, a display unit 4, an input unit 5, a communication unit 6, a processor 7, a memory 8, and a bus line 9 connecting these.

[0027] The group of programs held by the program database DB20 (not shown in Fig. 1) is shown in Fig. 3. The program database DB20 consists of an analytical section creation program Pr1, a transient stability calculation program Pr2, a power control candidate determination program Pr3, a transient stability measures planning program Pr4, a transient voltage drop determination program Pr5, a transient voltage drop bus identification program Pr6, a voltage sensitivity calculation program Pr7, and a transient voltage drop measures planning program Pr8.

[0028] The display unit 4, which is an output unit, is configured by, for example, any one or more of a display device, a printer device, a projector device, an audio output device, etc. The display unit 4 displays any one or more of various input data D1 (D11 to D17) and various output data D2 (D21 to D28) on a screen. Examples of the screen to be displayed will be described later.

[0029] The input unit 5 is configured with, for example, one or more of a keyboard, a switch, a mouse, a touch panel, a voice input device, and the like.

[0030] The communication unit 6 exchanges data with the power system 100 via the communication network 200 .

[0031] The processor 7 reads a program required for processing by the calculation unit 2 from the various programs constituting the program database DB20 and executes the calculation. The processor may be configured with one or more semiconductor chips, or may be configured with a computer or calculator.

[0032] The memory 8 is configured by a storage device such as a RAM (Random Access Memory), and stores the program Pr read from the program database DB20, the input data D1, the output data D2, and the like.

[0033] An example power system 100 shown in the lower part of Figure 2 is composed of generators 110a to 110c, such as synchronous generators and renewable energy power sources, nodes (buses) 120a to 120c and 121a to 121c, transformers 130a to 130c, branches (lines) 140a to 140c, etc.

[0034] The power system 100 also includes measuring devices 30a to 30b. The measuring devices 30a to 30b are linked to the power system stabilization device 1 via a communication network 200.

[0035] The measuring devices 30a to 30b acquire one or more of the following as system measurement data D12: the output of the generators 110a to 110c, the voltage values ​​at each of the nodes 120a to 120c and 121a to 121c, the values ​​of the active and reactive power flowing through the transformers 130a to 130c and branches 140a to 140c, and on / off information of circuit breakers at the nodes, transformers, branches, and phase modifying equipment, and transmit this data to the communication unit 6.

[0036] Furthermore, when a fault occurs in the power system 100, the measuring devices 30a to 30b detect information such as the location and nature of the fault and transmit the information to the control device 3 via the communication network 200.

[0037] The control device 3 receives the power control target calculation result data D28 from the power system stabilization device 1 via the communication network 200. When a fault occurs in the power system 100, the control device 3 compares the fault information acquired from the measurement devices 30a to 30b with one or more of the transient stability countermeasure data D24 and the transient voltage drop countermeasure data D28, and transmits a control command to the generators 110a to 110c.

[0038] The measurement devices 30a-30b acquire one or more of the following as system measurement data D14: TM (Telemeter) information such as the output P of the generators 110a-110c, the voltage values ​​V at the nodes 120a-120c and 121a-121c, the values ​​of the active power P and reactive power Q flowing through the transformers 130a-130c and branches 140a-140c, and SV (Super Vision) information on the on / off status of circuit breakers at the nodes, transformers, branches, and phase modifying equipment, and transmit it to the communication unit 13. Specifically, measurements are made using voltage transformers (VT), potential transformers (PT), current transformers (CT), etc.

[0039] The power system stabilizing device 10 can periodically acquire TM information and SV information from the measuring devices 30a to 30b via the communication network 200 and store the information in the power system measurement value DB.

[0040] Furthermore, some of the measuring devices 30a to 30b detect information such as the location and nature of a fault when a fault occurs in the power system 100, and transmit the information to the control device 3 via the communication network 200.

[0041] The control device 3 (slave station) receives the transient stability countermeasure data D24 and the transient voltage sag countermeasure data D28 from the power system stabilization device 10 via the communication network 200. When a fault occurs in the power system 100, the control device 3 compares the fault information acquired from the measurement devices 30a to 30b with one or more of the transient stability countermeasure data D24 and the transient voltage sag countermeasure data D28, and transmits a control command to a generator terminal station (transfer cutoff device) that cuts off the generators 110a to 110c.

[0042] Here, the data D11 to D17 held in the various input databases DB11 to DB17 constituting the power system stabilizing device 1 will be described with reference to the drawings.

[0043] 4 shows an example of system configuration data D11 held in the system configuration database DB11. As shown expanded vertically, the system configuration database DB11 stores information on the branches (lines) and synchronous generators that make up the power system, as well as information on loads, renewable energy power sources, transformers, phase modifying equipment, and the like (which can be considered equipment that makes up the power system).

[0044] The data that should be held for these devices is, as shown horizontally, for branches, the transmission line number, number of lines, node numbers at both ends, resistance, reactance, etc., and for the same devices, it is good to hold the synchronous generator number, interconnecting node, number of parallel units, rated capacity, rated output, reactance, etc. In the cases of loads, renewable energy sources, transformers, phase modifying equipment, etc., appropriate information will also be held.

[0045] 5 shows an example of system measurement data D12 held in the system measurement database DB12. The system measurement database DB12 stores one or more of the following information acquired via the communication network 200: the output of generators 110a-110c of the power system 100; voltage values ​​at each of nodes 120a-120c and 121a-121c; values ​​of active power and reactive power flowing through transformers 130a-130c and branches 140a-140c; and on / off information for circuit breakers at nodes, transformers, branches, and phase modifying equipment. This information is stored in chronological order for each measurement location, linked to timestamp information indicating the date and time of measurement.

[0046] Figure 6 shows an example of system model data D13 stored in the system model database DB13. In the system model database DB13 of Figure 6, synchronous generators, renewable energy power sources, and loads required for numerical analysis of power systems using computers or calculators are vertically developed and described, and information on the model types related to these models and the constants used therein is stored. In Figure 6, the notation "SG" in the equipment name column represents a synchronous generator, and "RES" represents a renewable energy power source, and these notations will be used where appropriate in the following illustrations.

[0047] FIG. 7 shows an example of the contingency data D14 held in the contingency database DB14. The contingency database DB14 stores information about the location (fault point), the nature of the fault, fault removal means, and the like for each contingency fault in the power system.

[0048] Fig. 8 shows an example of threshold data D15 held in threshold database DB15. In the threshold database DB15, the threshold data used for judgment, extraction, identification, and planning in each processing flow of the transient stability calculation unit 22, the power control candidate determination unit 23, the transient stability measure planning unit 24, the transient voltage sag determination unit 25, the transient voltage sag bus identification unit 26, and the transient voltage sag measure planning unit 28, which are processing functions of the calculation unit 2 shown in Fig. 1, are stored, in the illustrated example, for each of contingent faults A, B, and C in the power system, including an internal phase difference angle threshold for out-of-step judgment, an output change rate threshold, a voltage sag threshold, a voltage sag monitoring start time, and a voltage sag continuation monitoring time.

[0049] 9 shows an example of the shedding constraint data D16 stored in the shedding constraint database DB16. The shedding constraint database DB16 stores information regarding generators such as the generator SG and the renewable energy power source RES, such as whether each generator can be shedding or not, and if so, the timing of shedding. In the example shown, it is set that the renewable energy power source RES will not be used for shedding.

[0050] 10 shows an example of sensitivity calculation setting data D17 held in the sensitivity calculation setting database DB17. The sensitivity calculation setting database DB17 stores setting values ​​required by the voltage sensitivity calculation unit 27 and the transient voltage sag countermeasure planning unit 28, such as the voltage sag monitoring start time for each type of contingent fault and a voltage sag improvement threshold (a threshold for excluding power control candidates for which transient voltage sag improvement is not expected).

[0051] Next, the processing contents of the calculation unit 2 will be described with reference to Fig. 11. Fig. 11 shows the overall flow of processing of the power system stabilization device 1 in the first embodiment. The flow of the calculation processing will be described for each processing step.

[0052] First, in processing step S21 (corresponding to the analysis cross section creation unit 21), the analysis cross section creation program Pr1 is executed using the system configuration data D11 (Figure 4), system measurement data D12 (Figure 5), and system model data D13 (Figure 6), and analysis cross section data D21 of the power system 100 at the current time is created and registered in the analysis cross section database DB21.

[0053] Next, in processing step S22a (which corresponds to the transient stability calculation unit 22 together with 22b below), the analysis cross-section data D21 and the expected fault data D14 (Figure 7) are used to execute the transient stability calculation program Pr2 under the condition that none of the generators are powered down, and transient stability calculation result data D22 for the power system 100 is created and registered in the transient stability calculation result database DB22.

[0054] Next, in process step S22b, it is determined whether the power system 100 is transiently stable or unstable based on the transient stability calculation result data D22. Stability is determined using, for example, the internal phase difference angle, frequency, and voltage of a synchronous generator as indicators. If it is stable ("YES" in process step S22b), the process proceeds to process step S25, which will be described later. If it is unstable ("NO" in process step S22b), the process proceeds to process step S23, which will be described later.

[0055] Next, in processing step S23 (corresponding to the power control candidate determination unit 23), the power control candidate determination program Pr3 is executed using the threshold data D15 (Figure 8), the power control constraint data D16 (Figure 9), and the transient stability calculation result data D22, and power control candidate determination result data D23 is output and registered in the power control candidate determination result database DB23.

[0056] As a method for determining candidates for power control, for example, synchronous generators and renewable energy power sources for which the value of formula (1) is below the threshold value specified by the threshold data D15 are determined to be candidates for power control. i represents the rate of change of the active power output of the synchronous generator or renewable energy source i just before and after the occurrence of a contingency fault, and P i1 represents the active power output of the synchronous generator or renewable energy source i immediately before the occurrence of a contingency fault, and P i2 represents the active power output of synchronous generators or renewable energy sources i immediately after a contingency fault occurs. Also, G represents the set of all synchronous generators and renewable energy sources that can be dispatched.

[0057]

number

[0058] The formula for determining candidates for power control is not limited to formula (1). For example, the deviation or rate of change of the voltage of a synchronous generator or a renewable energy power source immediately before and after the occurrence of a contingency fault may be used as the formula for determination.

[0059] The detailed processing content of processing step S23 will be explained using Figure 12. Figure 12 is a diagram showing the concept of determining candidates for shedding control. The right side of this figure shows a power system including synchronous generators SG1, SG2, and SG3 and renewable energy power sources RES1 and RES2, in which a fault has occurred in the transmission line to which synchronous generator SG1 is connected. The left side of Figure 12 shows the time changes in the active power change rate of each of the synchronous generators SG1, SG2, and SG3 and the renewable energy power sources RES1 and RES2 before and after the fault occurred. In comparison with Figure 9, Figure 12 also shows the renewable energy power source RES3, but this is omitted from the illustration.

[0060] According to the rate of change in active power of each power source before and after the fault occurs shown on the left side of Figure 12, the change in active power is displayed as a percentage, with the active power before the fault occurring as the reference. According to this, generators that show a change of more than the threshold of 30% from the fault period from the occurrence of the fault to its removal are designated as candidates for shedding, namely, synchronous generators SG1 and SG2 and renewable energy power sources RES1 and RES2, while synchronous generator SG3, which shows a change of less than 30%, is not designated as a candidate for shedding. This is because even if a generator with a small change during this period is used for shedding, it is thought that the shedding effect will be small, so generators with a higher shedding effect are designated as candidates.

[0061] The shedding candidate determination process in processing step S23 determines shedding candidates for the countermeasure planning in processing steps S24 and S28, which will be described later. The purpose is to narrow down the calculation targets and reduce the amount of calculation in the transient stability countermeasure planning process in processing step S24 and the voltage sensitivity calculation process in processing step S27, which will be described later. If there is no need to reduce the amount of calculation, processing step S23 may be omitted, and all generators that are indicated as being shedding-capable in the shedding constraint data D16 may be set as shedding candidates.

[0062] Next, in processing step S24 (corresponding to the transient stability countermeasure planning unit 24), using the out-of-tune determination internal phase difference angle threshold of the threshold data D15 (Fig. 8), until the transient stability is stabilized, an electric control machine is selected from the electric control candidates, and the transient stability when performing the electric control process according to the selected electric control candidate is obtained and stored in the transient stability countermeasure planning database DB24 as transient stability countermeasure planning data. For the index of this electric control selection, the methods of Non-Patent Document 1 and Patent Document 1 can be used, etc.

[0063] Next, in processing step S25 (corresponding to the transient voltage drop determination unit 25), using the threshold data D15 (Fig. 8) and the transient stability countermeasure data D24 (the transient stability calculation result data after the electric control of the transient stability countermeasure, but when electric control is not required, the transient stability calculation result data D22 without electric control), the transient voltage drop determination program Pr5 is executed, the transient voltage drop determination result data D25 is output, and registered in the transient voltage drop determination result database DB25.

[0064] The method for determining the transient voltage drop is, in the time range from after the occurrence of the fault to the end time of the transient stability calculation, after the voltage drop monitoring start time (for example, 50 ms after the fault removal), if the voltage drop duration (t0) during which each monitored bus voltage falls below the voltage drop threshold (for example, 0.75 p.u.) is longer than the voltage drop continuous monitoring time (t) (for example, 100 ms) (t0≧t), it is determined that "there is a transient voltage drop". There are methods such as this.

[0065] Figs. 13A and 13B are diagrams showing the concept of transient voltage drop determination. Fig. 13A shows an example in which in the transient stability calculation waveform of a certain monitored bus voltage, when t0≧t, it is determined that "there is a transient voltage drop". Fig. 13B shows an example in which in the transient stability calculation waveform of a certain monitored bus voltage, when t0<t, it is determined that "there is no transient voltage drop". In this case, it is judged as a voltage drop based on the fact that the voltage drop continues for a predetermined time or more.

[0066] If it is determined that there is a transient voltage drop in one or more monitored bus voltages, the process proceeds to step S26; if it is determined that there is no transient voltage drop in any of them, the process ends and prepares for the next period calculation.

[0067] Next, in processing step S26 (corresponding to the transient voltage drop bus identification unit 26), the threshold data D15 (Figure 8), transient stability countermeasure data D24 (transient stability calculation result data after power control of transient stability countermeasures, but when power control is not required, transient stability calculation result data D22 without power control), and transient voltage drop judgment result data D25 are used to execute the transient voltage drop bus identification program Pr6, output transient voltage drop bus data D26, and register it in the transient voltage drop bus database DB26.

[0068] Methods for identifying a busbar with a transient voltage drop include, for example, selecting one busbar with the smallest minimum voltage since the start of voltage drop monitoring, or selecting multiple busbars with minimum voltages since the start of voltage drop monitoring that are less than a threshold value (for example, 0.75 pu).

[0069] Next, in processing step S27 (corresponding to voltage sensitivity calculation unit 27), the voltage sensitivity calculation program Pr7 is executed using the sensitivity calculation setting data D17 (FIG. 10) and the transient voltage drop bus data D26, and sensitivity calculation result data D27 is output and stored in the sensitivity calculation result database DB27.

[0070] If shedding is selected as a transient stability measure in processing step S24, transient stability calculations are performed assuming that each of the shedding candidate devices determined in processing step S23 (excluding devices selected for shedding as a transient stability measure) is additionally shedding independently (the target time for transient stability calculations may be the minimum target time for which sensitivity, described below, can be calculated), and sensitivity (hereinafter referred to as voltage sensitivity) is calculated from the transient voltage dip improvement in the transient voltage sag bus for shedding of each shedding candidate and the active power output deviation of the shedding candidate. The shedding candidate devices are then ranked in descending order of voltage sensitivity. Data related to the voltage sensitivity calculation results and rankings are output as sensitivity calculation result data D27. The method for calculating voltage sensitivity will be described later.

[0071] In processing step S27, the short-term transient stability is calculated for each candidate for shedding (excluding those targeted for shedding as a transient stability measure) at the time of additional shedding. Here, the definition of the voltage sensitivity calculated in processing step S27 will be explained using equation (2), Figure 14, and equation (3).

[0072] The sensitivity of the bus with the largest transient voltage sag is defined by equation (2), where VS stands for voltage sensitivity, the denominator is the active power output ΔP of the shedding machine k immediately before it is shedding (right side of Fig. 14), the numerator is the change in the minimum voltage value ΔV of the bus with the largest transient voltage sag after the start of voltage sag monitoring due to the additional shedding of the shedding machine k after shedding to prevent loss of synchronism (left side of Fig. 14), and S represents the set of synchronous generators SG and renewable energy sources RES that are candidates for shedding.

[0073]

number

[0074] Figure 14 shows an image of the calculation of equation (2) in processing step S27. Figure 14 shows an image of the calculation of voltage sensitivity when a synchronous generator or renewable energy power source that is a candidate for shedding is shedding-controlled. The right side of Figure 14 shows the denominator ΔP k、shedding The left side of Figure 14 shows the numerator ΔV on the right side of equation (2). j,k shedding This is an image of the calculation.

[0075] The sensitivity denominator shown on the right side of Fig. 14 shows the waveforms when the synchronous generator or renewable energy power source is controlled and when it is not controlled on the time series waveforms that are the transient stability calculation results when a fault occurs in the active power output Pk of the controlled generator k. The active power output ΔP k、shedding represents.

[0076] The sensitivity numerator shown on the left side of Fig. 14 shows the waveforms with and without the control of synchronous generators or renewable energy power sources on the time-series waveform of the voltage of transient voltage sag bus j under the same conditions as the sensitivity denominator shown on the right side of Fig. 14. This shows the voltage deviation ΔV of transient voltage sag bus j, which indicates how much the bottom value of the transient voltage sag near the peak of the first wave of the synchronous generator, which mainly accelerates after the fault is cleared, has improved. j,k shedding represents.

[0077] The sensitivity definition formula (2) can be found for all synchronous generators and renewable energy power source shedding, which has the effect of making it possible to uniformly evaluate the stabilizing effect of shedding for synchronous generators and renewable energy power sources. Also, by finding sensitivity for only accelerated synchronous generators rather than for all synchronous generators, it is possible to efficiently find shedding targets that are most effective in improving transient voltage drops.

[0078] In addition, when calculating the average sensitivity of multiple transient voltage sag buses, it is defined by equation (3). Here, the denominator is the same as equation (2), and the numerator is the average change in the minimum voltage of transient voltage sag bus j (j∈N) after the voltage sag monitoring start time due to additional shedding of shedding machine k after the out-of-step prevention shedding (average value is ΔP k、shedding ) and N indicates a set of transient voltage sag buses.

[0079]

number

[0080] When equation (3) is used instead of equation (2), it is possible to select a shedding machine that is effective in preventing transient drops not only in one location in the system but in the entire monitored bus.

[0081] Here, either formula (2) or formula (3) can be used for the voltage sensitivity. In formula (2), the bus with the largest transient voltage drop is used as the voltage sensitivity numerator, but formula (3), which calculates the average improvement level of multiple buses with large transient voltage drops, does not use the bus with the largest transient voltage drop.

[0082] It is also possible that it may not be possible to find a target for shedding that is highly effective in improving transient voltage sags. In such cases, it is advisable to set a calculation termination count to avoid a situation where calculations are continued for a long period of time without obtaining an appropriate solution, and to adopt a method in which transient voltage sag shedding control is not executed at all.

[0083] Next, in processing step S28 (corresponding to the transient voltage drop countermeasure planning unit 28), the sensitivity calculation setting data D17 (FIG. 10), the sensitivity calculation result data D27, the threshold data D15 (FIG. 8), etc. (including system-related data required for transient stability calculation, etc.) are used to execute the transient voltage drop countermeasure planning program Pr8, output transient voltage drop countermeasure data D28, and store it in the transient voltage drop countermeasure database DB28.

[0084] Here, a detailed flow of transient voltage drop countermeasure planning in processing step S28 is shown in Fig. 15. The procedure for selecting targets for power control will be explained for each processing step in Fig. 15.

[0085] First, in processing step S281, it is determined whether there is a candidate for power control whose voltage sensitivity is greater than the voltage drop improvement threshold (set to 0 in the example of FIG. 10, but it may be a constant other than 0) based on the voltage sensitivity of each candidate for power control calculated in processing step S27. If there is a candidate for power control whose voltage sensitivity is greater than the voltage drop improvement threshold (if "YES" in S281), the process proceeds to processing step S282, which will be described later. If there is no candidate for power control whose voltage sensitivity is greater than the voltage drop improvement threshold (if "NO" in S281), a message to that effect is output, and the process ends without formulating any measures against transient voltage drops. Note that the voltage drop improvement threshold may be set to a constant other than 0.

[0086] Next, in process step S282, a target for shedding is selected from the shedding candidate candidates in descending order of voltage sensitivity. However, ascending order may be used if the voltage sensitivity is an inverse number, for example. The number of targets for shedding may be the highest-ranked candidate, or multiple candidates. When selecting multiple targets for shedding, it is necessary to avoid selecting excessive targets for shedding to ensure stabilization. One method for determining this is to select multiple candidates for shedding in descending order of voltage sensitivity within a range in which the total shedding amount is equal to or less than the value specified in threshold data D15. The shedding candidate selection in process step S282 is repeated until the transient voltage drop is resolved in the transient stability calculation in process step S283, described below. Therefore, allowing multiple targets to be selected at once shortens the number of iterative calculations in this flow and reduces the amount of calculations.

[0087] Next, in processing step S283, transient stability calculation is performed under the condition that all of the power control targets selected in processing step S282 are controlled.

[0088] Next, in process step S284, the presence or absence of a transient voltage drop is determined based on the transient stability calculation result obtained in process step S283. The determination method is the same as in process step S25 described above. If a transient voltage drop is present (YES in S284), the process returns to process step S281. If no transient voltage drop is present (NO in S284), the process proceeds to process step S285, which will be described later.

[0089] Next, in processing step S285, the target of power control selected in processing step S282 is determined as the target of power control for the transient voltage drop countermeasure, and the processing ends.

[0090] Figure 16 shows an image of the shedding selection in processing step S282. In the table shown, the vertical axis shows the transient voltage sag improvement amount of the transient voltage sag bus, which is the numerator of the voltage sensitivity, and the active power output deviation, voltage sensitivity, ranking, and selection status of each shedding candidate, which is the denominator of the voltage sensitivity, immediately before and after shedding, for each shedding candidate. The horizontal axis lists SG1, SG2, and RES1 and RES2 as examples of sensitivity calculation candidates (shedding candidates) for synchronous generators and renewable energy power sources. As mentioned above, SG3 was excluded from the shedding candidates because it would have little shedding effect.

[0091] Of the candidates for shedding, those that have already been selected as a transient stability measure are not subject to voltage sensitivity calculations, so the numerator and denominator of voltage sensitivity, voltage sensitivity, and ranking columns are indicated with a bar (-), and the selection status indicates that they have been selected as a transient stability measure. The other candidates for shedding can be shedding as a measure against transient voltage drops, so they are ranked from 1st to 3rd in descending order of voltage sensitivity. In processing step S282, one or more units are selected for shedding based on this ranking.

[0092] In the example shown in Figure 16, the numerator of the voltage sensitivity (ΔV / ΔP) is an example in which the average value of the voltage improvement range of multiple transient voltage sag buses is used, which makes it possible to deal with cases in which only one transient voltage sag bus is identified.

[0093] The procedure of the processing steps S22a to S28 described above is performed for each contingency fault and is repeated until the calculations for all contingencies are completed. When the calculations for all contingencies are completed, the power control target calculation result data D28 is transmitted to the control device 3.

[0094] In Patent Document 1, sensitivity, which indicates the degree of improvement in transient stability, is used as an index for selecting shedding control as a means of improving the stability of the power system, but this sensitivity does not take into account the degree of improvement in transient voltage sag. If an attempt is made to improve not only transient stability but also transient voltage sag using an index used to improve transient stability, it may not be possible to select an appropriate shedding control unit, which may increase the amount of shedding control, or it may not be possible to improve transient voltage sag.

[0095] In contrast, the present invention has the effect of addressing the above-mentioned issues by calculating an index that can be used to evaluate the transient voltage drop improvement effect of power control of synchronous generators and renewable energy power sources in the same way, separate from transient stability measures, and selecting targets for power control as transient voltage drop countermeasures based on this index.

[0096] Next, an example of the result display when the display unit 4 having a monitor screen or the like is used as the output unit will be described with reference to FIGS.

[0097] In the display example in Figure 17, sensitivity calculation result data D27 and transient voltage sag countermeasure data D28 are displayed in the form of a table and graph. In the "Search Settings" field in Figure 17, you set the time and contingency for the power flow cross section for which you want to display the results of the shedding machine selection. The "Results" field in Figure 17 displays the shedding combination, total shedding amount, and voltage sensitivity table. The "Effect" field in Figure 17 shows a graph of the transient voltage sag improvement effect of shedding as a result of shedding measures against transient voltage sag. These screens allow power system operators and planners to easily check the shedding targets and total shedding amount for each power flow cross section and contingency, the degree of transient voltage sag improvement effect, and so on.

[0098] In the display example of Figure 18, transient stability countermeasure data D24, transient voltage sag bus data D26, and transient voltage sag countermeasure data D28 are displayed on a power system diagram. In addition to the locations of contingent faults and transient voltage sag buses, this system diagram also displays synchronous generators and renewable energy power sources connected to the system, categorizing them as targets for transient stability countermeasure shedding, targets for transient voltage sag countermeasure shedding, and non-targets for shedding. In addition, candidates for shedding may also be shown on the system diagram. This has the advantage of allowing power system operators and planners to easily grasp the relative locations of contingent faults, transient voltage sag buses, and targets for shedding.

[0099] The present invention is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and are not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations. Furthermore, part or all of the above-described configurations, functions, processing units, etc. may be realized in hardware, for example, by designing them as integrated circuits. [Explanation of symbols]

[0100] 1: Power system stabilizer 2: Arithmetic section 3: Control device 4: Output section 5: Input section 6: Communications Department 7: Processor 8: Memory 9: Bus line D1: Input data D2: Output data D11: System configuration data D12: System measurement data D13: System model data D14: Contingency data D15: Threshold data D16: Power control constraint data D17: Sensitivity calculation setting data D21: Analysis cross-sectional data D22: Transient stability calculation result data D23: Power control candidate evaluation result data D24: Transient stability measures data D25: Transient voltage drop judgment result data D26: Transient voltage sag bus data D27: Sensitivity calculation result data D28: Transient voltage drop countermeasure data DB1: Input database DB2: Output database DB11: System configuration database DB12: System Measurement Database DB13: System model database DB14: Contingency Database DB15: Threshold database DB16: Power control constraint database DB17: Sensitivity calculation setting database DB20: Program Database DB21: Analysis cross section database DB22: Transient stability calculation results database DB23: Database of power control candidate evaluation results DB24: Transient stability countermeasure database DB25: Transient voltage drop judgment result database DB26: Transient Voltage Sag Bus Database DB27: Sensitivity calculation results database DB28: Transient Voltage Drop Countermeasures Database Pr1: Analysis cross section creation program Pr2: Transient stability calculation program Pr3: Program for determining candidates for power control Pr4: Transient stability measures planning program Pr5: Transient voltage drop detection program Pr6: Transient voltage drop bus identification program Pr7: Voltage sensitivity calculation program Pr8: Transient voltage drop countermeasure planning program 30a, 30b: Measuring device 100: Power system 110a to 110c: Synchronous generator or renewable energy power source 120a~120c, 121a~121c: Node (bus line) 130a~130c: Transformers 140a~140c: Branch (railway) 200: Communication Network

Claims

1. A power system stabilization device that determines a power control target for performing stabilization control when a fault occurs in a power system according to stability at the time of an assumed fault in a power system including a synchronous generator and a renewable energy power source, a power control candidate determination unit that determines power control candidates of synchronous generators and renewable energy power sources based on a transient stability calculation result at the time of a contingency fault in the power system; a transient voltage dip determination unit that determines a transient voltage dip based on a transient stability calculation result; a transient voltage sag bus identifying unit that identifies a transient voltage sag bus based on a transient stability calculation result; a sensitivity calculation unit that calculates sensitivity based on an improvement in transient voltage sag at the transient voltage sag bus in response to the shedding of the shedding candidate and an active power output deviation of the shedding candidate; A power system stabilization device comprising: a transient voltage drop countermeasure planning unit that selects the candidate power control targets as power control targets in accordance with the sensitivity.

2. 2. The power system stabilization device according to claim 1, The power system stabilization device is characterized in that the power control candidate determination unit receives threshold data, the transient stability calculation result, and the power control constraint data as inputs, determines a power control candidate based on the active power output deviation or voltage deviation of the synchronous generator and the renewable energy power source immediately before and after a contingency fault occurs in the power system, and outputs the result as a power control candidate determination result.

3. 2. The power system stabilization device according to claim 1, The power system stabilization device is characterized in that the transient stability calculation result is created by a transient stability calculation unit that calculates transient stability at the time of a contingent fault in the power system using contingent fault data and analytical cross-section data as inputs.

4. 4. The power system stabilization device according to claim 3, The power system stabilization device is characterized in that the analysis cross section data is output by an analysis cross section creation unit that creates an analysis cross section of the power system using system configuration data, system measurement data, and system model data as inputs.

5. 2. The power system stabilization device according to claim 1, the transient voltage drop determination unit receives threshold data and transient stability measure data as inputs, and outputs transient voltage drop determination result data indicating whether or not a transient voltage drop occurs in the power system at the time of a contingent fault after the transient stability measure has been taken.

6. 2. The power system stabilization device according to claim 1, The power system stabilization device is characterized in that the transient voltage dip bus identification unit receives threshold data and transient voltage dip determination result data as inputs, identifies one or more buses where a transient voltage dip is occurring, and outputs the identified buses as transient voltage dip bus data.

7. 2. The power system stabilization device according to claim 1, the sensitivity calculation unit receives sensitivity calculation setting data, transient voltage sag bus data, and shedding candidate determination result data as inputs, calculates sensitivity represented by dividing an average value of transient voltage sag improvement amounts of the transient voltage sag buses due to shedding of the shedding candidate by the active power output deviation of the shedding candidate, and outputs the sensitivity calculation result data.

8. 8. The power system stabilization device according to claim 7, the average value of the transient voltage sag improvement amount is calculated using one or more of an arithmetic mean, a weighted mean, a geometric mean, and a harmonic mean of the transient voltage sag improvement amounts of one or more transient voltage sag buses.

9. 2. The power system stabilization device according to claim 1, The power system stabilization device is characterized in that the transient voltage sag countermeasure planning unit receives threshold data, sensitivity calculation setting data, and sensitivity calculation result data as inputs, selects a target for power control from among power control candidates in accordance with the sensitivity until the transient voltage sag is resolved, and outputs the result as transient voltage sag countermeasure data.

10. 2. The power system stabilization device according to claim 1, The power system stabilization device is characterized in that, if there are no power control candidates whose sensitivity is greater than a preset value, the transient voltage drop countermeasure planning unit outputs a message to that effect and terminates processing without selecting a power control candidate for transient voltage drop countermeasures.

11. 2. The power system stabilization device according to claim 1, comprising an output unit, The power system stabilization device is characterized in that the output unit outputs at least one of system configuration data, system measurement data, system model data, contingency data, threshold data, shearing control constraint data, sensitivity calculation setting data, analysis cross-section data, transient stability calculation result data, shearing control candidate determination result data, transient stability countermeasure data, transient voltage sag determination result data, transient voltage sag bus data, sensitivity calculation result data, and transient voltage sag countermeasure data.

12. A power system stabilization method for determining a power control target for performing stabilization control when a fault occurs in a power system, according to stability at the time of a contingency fault in a power system including a synchronous generator and a renewable energy power source, using a computer, a transient voltage drop determination step for determining whether a synchronous generator or a renewable energy power source is a candidate for power control based on the transient stability calculation result at the time of a contingency fault in the power system; a transient voltage drop determination step for determining whether a transient voltage drop has occurred based on the transient stability calculation result; a transient voltage drop bus identification step for identifying a transient voltage drop bus based on the transient stability calculation result; a sensitivity calculation step for calculating sensitivity based on the transient voltage drop improvement amount of the transient voltage drop bus relative to the power control of the power control candidate and the active power output deviation of the power control candidate; and a transient voltage drop countermeasure planning step for selecting the power control candidate as a target for power control based on the sensitivity.

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