Power system stability analysis device, stabilization apparatus, and method
There is provided a power system stability analysis device that analyzes stability of a power system by obtaining measurement data from a highaccuracy measurement device and existing measuring instruments installed in the power system, the apparatus including: a system state estimation unit that estimates a system state of the power system by using measurement data from the existing measuring instruments at a plurality of points in the power system; a synchronous stability analysis unit that analyzes synchronous stability in an assumed failure by using an estimation result of the system state; and a synchronous stability analysis correction unit that corrects the synchronous stability according to a difference between the estimation result of the system state and the measurement data of the highaccuracy measurement device to improve accuracy of synchronous stability analysis of the power system.
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The present invention relates to a power system stability analysis device, a stabilization apparatus, and a method.
BACKGROUND ARTAs a background art in this technical field, there is disclosed in U.S. Pat. No. 8,190,379 (PTL 1). It is important to correctly understand the power flow state (active power P, reactive power Q, voltage V, voltage phase δ) of a power system for power system stability analysis. By reproducing a state close to a current power system with an analysis model, it is possible to predict the state of the power system in the event of a failure and to perform a stabilization measure in preparation for a power system failure in advance. In general, the state of the power system is grasped by a system state estimation calculation using measurement values (active power P, reactive power Q, voltage magnitude V, voltage phase δ, current I, and the like) of the amount of electricity measured by a measurement sensor installed in the power system.
In order to grasp the state of the power system, it is important to prepare a sufficient number of measurement values to solve the power equation of the power system and make the values observable, but depending on the configuration of the power system and the power flow conditions (if there is a section where the resistance component of a line is large, if there is a section where the reactive power flow is large, if, for example, the voltage values of adjacent measurement values are significantly different, or the like), the system state estimation calculation does not converge in some cases. When the system state estimation calculation does not converge, there is a problem that a large error occurs between a current system state and the calculated value in a previous calculation, and the reliability of the obtained estimation result decreases. In particular, this problem is likely to occur in areas where the monitoring function and measurement accuracy of the power system are insufficient.
When the reliability of the estimation result decreases, the reliability of the synchronous stability analysis of the power system also decreases. In a power system stabilization apparatus, for example, if an incorrect synchronous stability analysis result is input and a powercontrolled generator is determined, appropriate power control for preventing a power failure cannot be taken, and there is a risk of power failure. The power system stabilization apparatus is an apparatus that disconnects (electrically controls) the accelerated generator from the power system in order to prevent the occurrence of the phenomenon that the internal phase difference angle of the accelerated generator with respect to a reference generator becomes larger than that of other generators due to a power system failure, and synchronization between generators cannot be maintained.
At present, the spread of a technique employing a highaccuracy measurement device such as a phase measurement device phasor measurement unit (PMU) and the like is expected. For example, PTL 1 discloses a power flow monitoring device for a power system that verifies the accuracy of system state estimation by using a phase measurement device PMU. PTL 1 discloses that the validity of system state estimation is verified by comparing a system state estimation result with data of a phase measurement device PMU.
CITATION LIST Patent LiteraturePTL 1: U.S. Pat. No. 8,190,379
SUMMARY OF INVENTION Technical ProblemHowever, in the power flow monitoring device for a power system described in PTL 1, it is not known how much a state estimation error affects the synchronous stability of the power system. Therefore, appropriate measures such as power control cannot be taken, which may lead to an increase in cost due to measures such as excessive power control and a power failure due to measures such as insufficient power control.
From the above, an object of the present invention is to provide a power system stability analysis device, a stabilization apparatus, and a method capable of preventing excessive and insufficient power supply restrictions of the power system stabilization apparatus by using a measurement value of a highaccuracy measurement device to improve the accuracy of a synchronous stability result, in a case where the calculation of state estimation does not converge or the accuracy is low.
Solution to ProblemIn order to solve the abovementioned problems, the present invention is directed to “a power system stability analysis device that analyzes stability of a power system by obtaining measurement data from a highaccuracy measurement device and existing measuring instruments installed in the power system, the device including: a system state estimation unit that estimates a system state of the power system by using the measurement data from the existing measuring instruments at a plurality of points in the power system; a synchronous stability analysis unit that analyzes synchronous stability in an assumed failure by using an estimation result of the system state; and a synchronous stability analysis correction unit that corrects the synchronous stability according to a difference between the estimation result of the system state and the measurement data of the highaccuracy measurement device to improve accuracy of synchronous stability analysis of the power system”.
The present invention is directed to “a power system stabilization analysis method for analyzing stability of a power system by obtaining measurement data from a highaccuracy measurement device and existing measuring instruments installed in the power system, the method including: estimating a system state of the power system by using the measurement data from the existing measuring instruments at a plurality of points in the power system; analyzing synchronous stability in an assumed failure by using an estimation result of the system state; and correcting the synchronous stability according to a difference between the estimation result of the system state and the measurement data from the highaccuracy measurement device to improve accuracy of synchronous stability analysis of the power system”.
The present invention is directed to “the power system stabilization method including: determining and storing an appropriate powercontrolled generator for preventing a power failure in the event of an assumed failure in the power system by using the synchronous stability after correction; and controlling the determined powercontrolled generator in the event of the assumed failure”.
The present invention is directed to “the power system stabilization method including: determining and storing an appropriate powercontrolled generator for preventing a power failure in the event of an assumed failure in the power system by using the synchronous stability after correction; selecting one of the synchronization stability when not performing correction and when performing correction; and selecting the synchronous stability after correction when a difference between the synchronous stability before correction and after correction is equal to or greater than a threshold”.
Advantageous Effects of InventionAccording to the present invention, in a case where the calculation of the state estimation does not converge or the accuracy is low, it is possible to prevent excessive and insufficient power supply restrictions of the power system stabilization apparatus by using the measurement value of the highaccuracy measurement device to improve the accuracy of the synchronous stability result.
Hereinafter, preferred examples of the present invention will be described with reference to drawings. The following is merely examples, and the invention itself is not intended to be limited to the following specific contents.
Example 1Example 1 of the present invention will be described below.
First, an example of a typical power system to which an example of the present invention can be applied and an example of a hardware configuration of a power system stability analysis device according to the example of the present invention will be described with reference to
In the upper part of
In
In the illustrated example, for example, phase measurement device phasor measurement units (PMU) are installed as a highaccuracy measurement device at the nodes 110 having the node numbers N2 and N6, and at the other nodes 110 having the node numbers N1, N3, N4, and N5, for example, a current transformer CT, a voltage transformer PT, and the like are installed as a measurement device of related art.
In the ordinary power system illustrated in
Therefore, in the present invention, the accuracy of the entire power system is to be improved by reflecting the measurement result of the node where the highaccuracy measurement device PMU is installed in the measurement result of the node where the highaccuracy measurement device PMU is not installed.
The power system stability analysis device 10 illustrated in the lower part of
The databases DB include a system state estimation result database DB1, a synchronous stability analysis result database DB2, a highaccuracy measurement device measurement value database DB3, a correction model DB4, and a synchronous stability analysis correcting result DB5. The signals taken into the power system stability analysis device 10 via the communication network 300 are appropriately stored and kept in the databases DB as described above, either directly as primary information or indirectly in the form of secondary information obtained by processing the primary information. However, the signal measured by the highaccuracy measurement device PMU is stored and kept in the highaccuracy measurement device measurement value database DB3.
In
The input unit 22 can include, for example, at least one of a keyboard switch, a pointing device such as a mouse and the like, a touch panel, a voice instruction device, and the like.
The communication unit 23 includes a circuit and a communication protocol for connecting to the communication network 300.
The CPU 24 executes a calculation program, instructs image data to be displayed, and searches for data in various databases. The CPU 24 may be configured as one or a plurality of semiconductor chips, or may be configured as a computer device such as a calculation server.
The memory 25 is configured as, for example, a random access memory (RAM), and stores a computer program, and stores calculation result data and image data necessary for each processing. The screen data loaded in the memory 25 is sent to the display unit 21 and displayed.
The functional analysis of the power system stability analysis device 10 includes a state estimation calculation unit 11, a synchronous stability analysis unit 12, a correction model creation unit 13, and a synchronous stability analysis correction unit 14 as arithmetic processing functions, and can be represented as a device including the system state estimation result database DB1, the synchronous stability analysis result database DB2, the highaccuracy measurement device measurement value database DB3, the correction model DB4, and the synchronous stability analysis correcting result DB5 as storage functions.
In the processing in the power system stability analysis device 10, first, the state estimation calculation unit 11 estimates the power flow state of the power system from measurement data at a plurality of points in the power system. The estimated power flow state of the power system is used in the next synchronous stability analysis unit 12 and is loaded and stored as a system state estimation result in the system state estimation result database DB1.
Next, the synchronous stability analysis unit 12 analyzes the synchronous stability at the assumed failure from the system state estimation result obtained by the state estimation calculation unit 11. The analyzed synchronous stability is used in the next synchronous stability analysis correction unit 14 and is loaded and stored as a synchronous stability analysis result in the synchronous stability analysis result database DB2.
The processing in the state estimation calculation unit 11 and the synchronous stability analysis unit 12 described above is performed by using information measured by, for example, a current transformer CT, a voltage transformer PT, or the like as a measurement device of related art, which are installed at the nodes 110 having the node numbers N1, N3, N4, and N5 in the power system illustrated in
For this reason, in the present invention, the next synchronous stability analysis correction unit 14 performs the correction processing of the synchronous stability analysis processing. Two pieces of information are used for correction. One is information from the highaccuracy measurement device measurement value database DB3 storing and keeping the signal measured by the highaccuracy measurement device PMU installed at the nodes 110 having the node numbers N2 and N6, in the power system illustrated in
The correction model database DB4 is formed by the processing in the correction model creation unit 13. The correction model creation unit 13 creates a sensitivity distribution of the power system from the system state estimation result stored in the system state estimation result database DB1, the highaccuracy measurement value stored in the highaccuracy measurement device measurement value database DB, and the past data of the synchronous stability analysis result stored in the synchronous stability analysis result database DB2. Thus, the sensitivity distribution at each node of the power system is stored in the correction model database DB4. This information is generator internal phase angle correction information that is a sensitivity distribution.
The synchronous stability analysis correction result obtained by the synchronous stability analysis correction unit 14 is loaded and stored in the synchronous stability analysis correction result database DB5.
In the processing step S100 in
Here, Z is an observed value (P, Q, V), X is a system state (V, θ, and the like), and F(X) is a circuit equation determined from, for example, the connection state and impedance of a circuit as state values.
[Equation 1]
Z=F(X)+e (1)
[Equation 2]
{Z−F(X)}^{2}→min (2)
In the processing step S102, a residual ε is calculated, and error data is removed such that a measurement value having a large residual is removed or replaced with a substitute pseudo measurement value (past measurement data is used instead).
In processing step S103, the calculated residual ε is compared with a specified value. If the residual ε is equal to or smaller than the specified value, the processing flow of the state estimation calculation ends, and if the residual ε is equal to or larger than the specified value, the process returns to the processing step S101. Such a power system state estimation calculation is an established calculation method, and can be calculated by using a general algorithm.
Returning to
If a failure occurs in the power system, the generator may not be able to maintain the state of operating at the same frequency as the system, and the mechanism can be illustrated by a fluctuation equation and a power phase difference angle curve (Pδ curve).
In the power system, the fluctuation equation of the generator is expressed by a fluctuation equation of Equation (3) by using a mechanical input P_{m}, a generator inertia constant M, an electrical output P_{e}, and a generator phase difference angle δ.
From this equation, it can be seen that if the mechanical input P_{m }and the electrical output P_{e }are balanced, a synchronous generator will be operated at a constant speed. However, if the mechanical input and the electrical output are not balanced, the synchronous generator will accelerate or decelerate.
In the processing step S103, the synchronous stability analysis is corrected. At the time of correction, for example, a difference between a measurement value of a highaccuracy measurement device and a system state estimation result is used as an input value for correcting the synchronous generator. The generator internal phase angle is analyzed in advance by a computer, and the generator internal phase angle is corrected from the sensitivity distribution created by preliminary analysis. The processing step S103 corresponds to the function of the correction model creation unit 13 and the synchronous stability analysis correction unit 13 in
The generator internal phase angle correction model, which is a sensitivity distribution, is created by performing synchronous stability analysis on past state estimation results and a number of assumed system states and performing regression analysis. The relationship between the generator internal phase angles before and after the correction and the difference between the measurement values of the measurement device of related art and the highaccuracy measurement device is calculated in advance.
At the time of actual operation of the correction model created as illustrated in
For the information of the value to be compared, that is, the state quantity estimation result and the highaccuracy measurement device measurement value, any of the active power P, the reactive power Q, the voltage V, the voltage phase δ, or the like, or a plurality of parameters may be used as the power flow of the power system. The parameters to be used among the active power P, the reactive power Q, the voltage V, the voltage phase δ, and the like may be values of only one time section, or average values of a plurality of time sections. The state estimation result of the generatorinstalled node and the measurement value of the highaccuracy measurement device may be used, or the state estimation results of all the nodes at which the highaccuracy measurement device is installed and the measurement value of the highaccuracy measurement device may be used.
According to Example 1, in a case where the calculation of the state estimation does not converge or in a case where the accuracy is low, by correcting the generator internal phase angle, it is possible to improve the accuracy of the synchronous stability result by using the measurement value of the highprecision measurement device.
Example 2Example 2 of the present invention will be described below. Example 2 is an example of a power system stabilization apparatus 30 in which the processing result of the stability analysis device of Example 1 is applied to power supply restriction. A description overlapping with the content described in Example 1 will be omitted.
The power system stabilization apparatus 30 of Example 2 illustrated in
Here, the power supply restriction determination unit 15 determines an appropriate powercontrolled generator for preventing a power failure from the synchronous stability result. The determined powercontrolled generator is loaded and stored in the power supply restriction tableuse database correspondence database DB6 as a power supply restriction tableuse database.
By providing the power supply restriction tableuse database DB6 with a plurality of types of power supply restriction tables reflecting the stability analysis results after correction, for example, when an assumed failure occurs and power supply restriction becomes indispensable, it is possible to target a powercontrolled generator determined based on accurate estimation of the system state.
On the other hand, with the synchronous stability analysis correction, the generator internal phase angle converged and became stable. Here, a power supply restriction list was created with generator internal phase angle correction, and it was determined that power supply was to be restricted in the event of failure. As a result, the generator internal phase angle becomes stable when a failure occurred during actual operation.
According to Example 2, in a case where the calculation of the state estimation does not converge or the accuracy is low, it is possible to prevent excessive and insufficient power supply restrictions of the power system stabilization apparatus by using the measurement value of the highaccuracy measurement device to improve the accuracy of the synchronous stability result.
Example 3Example 3 of the present invention will be described below.
The power system stabilization apparatus 30 of Example 3 illustrated in
In the power system stabilization apparatus 30 of
According to Example 3, in a case where the calculation of the state estimation does not converge or the accuracy is low, it is possible to prevent excessive and insufficient power supply restrictions of the power system stabilization apparatus by using the measurement value of the highaccuracy measurement device to improve the accuracy of the synchronous stability result.
In the synchronous stability analysis correction unit of the present invention illustrated in

 10: power system stability analysis device
 11: system state estimation calculation unit
 12: synchronous stability analysis unit
 13: correction model generation unit
 14: synchronous stability analysis correction unit
 15: power supply restriction determination unit
 16: synchronous stability analysis result selection unit
 21: display unit
 22: input unit
 23: communication unit
 24: CPU
 25: memory
 26: bus line
 20: power system
 30: power system stabilization apparatus
 110: node
 120: transformer
 130: generator
 140: transmission line
 150: load
 300: communication network
 DB1: system state estimation result database
 DB2: synchronous stability analysis result database
 DB3: highaccuracy measurement device measurement value database
 DB4: correction model database
 DB5: synchronous stability analysis correcting result database
 DB6: power supply restriction tableuse database correspondence database
Claims
1. A power system stability analysis device that analyzes stability of a power system by obtaining measurement data from a highaccuracy measurement device and existing measuring instruments installed in the power system, the device comprising:
 a system state estimation unit that estimates a system state of the power system by using the measurement data from the existing measuring instruments at a plurality of points in the power system;
 a synchronous stability analysis unit that analyzes synchronous stability in an assumed failure by using an estimation result of the system state; and
 a synchronous stability analysis correction unit that corrects the synchronous stability according to a difference between the estimation result of the system state and the measurement data of the highaccuracy measurement device to improve accuracy of synchronous stability analysis of the power system.
2. The power system stability analysis device according to claim 1, wherein the synchronous stability analysis correction unit includes a correction model creation unit that creates a sensitivity distribution from the estimation result of the system state, the measurement data of the highaccuracy measurement device, and past data of analysis results of the synchronous stability.
3. The power system stability analysis device according to claim 1, wherein
 the synchronous stability analysis correction unit shows a relationship between a voltage phase difference between the measurement data from the existing measuring instruments and the highaccuracy measurement device, a generator internal phase angle before correction which is the estimation result of the system state, and a generator internal phase angle after correction, and
 obtains a generator internal phase angle after correction from the generator internal phase angle before correction, which is the estimation result of the system state, and the voltage phase difference between the measurement data from the existing measuring instruments and the highaccuracy measurement device.
4. The power system stability analysis device according to claim 1, further comprising:
 a system state estimation result database that stores the estimation result of the system state;
 a synchronous stability analysis result database that stores an analysis result of the synchronous stability;
 a highaccuracy measurement device measurement value database that stores measurement data of a measurement value from a highaccuracy measurement device; and
 a synchronous stability analysis correction database that stores a correction result of the synchronous stability analysis.
5. A power system stabilization apparatus comprising:
 the power system stability analysis device according to claim 1 including a power restriction determination unit that determines an appropriate powercontrolled generator for preventing a power failure in the event of an assumed failure in the power system by using synchronous stability obtained by the synchronous stability analysis correction unit, and a database that stores the determined powercontrolled generator, wherein
 the power system stabilization apparatus controls the determined powercontrolled generator in the event of the assumed failure.
6. A power system stabilization apparatus comprising:
 the power system stability analysis device according to claim 1 including a power restriction determination unit that determines an appropriate powercontrolled generator for preventing a power failure in the event of an assumed failure in the power system by using synchronous stability obtained by the synchronous stability analysis correction unit, a database that stores the determined powercontrolled generator, and a synchronous stability analysis result selection unit that selects one of the synchronous stability when not performing correction and when performing correction in the synchronous stability analysis correction unit, wherein
 when a difference between the synchronous stability before correction and after correction is equal to or greater than a threshold, the power system stabilization apparatus selects the synchronous stability after correction.
7. A power system stabilization analysis method for analyzing stability of a power system by obtaining measurement data from a highaccuracy measurement device and existing measuring instruments installed in the power system, the method comprising:
 estimating a system state of the power system by using the measurement data from the existing measuring instruments at a plurality of points in the power system;
 analyzing synchronous stability in an assumed failure by using an estimation result of the system state; and
 correcting the synchronous stability according to a difference between the estimation result of the system state and the measurement data from the highaccuracy measurement device to improve accuracy of synchronous stability analysis of the power system.
8. The power system stabilization analysis method according to claim 7, wherein
 the estimation result of the system state, the measurement data of the highaccuracy measurement device, and a correction model for a sensitivity distribution created from past data of analysis results of the synchronization stability are used in the correction of the synchronous stability.
9. The power system stabilization analysis method according to claim 7, wherein
 regarding a relationship between a voltage phase difference between the measurement data from the existing measuring instruments and the highaccuracy measurement device, a generator internal phase angle before correction, which is the estimation result of the system state, and a generator internal phase angle after correction,
 the generator internal phase angle after correction is obtained from the generator internal phase angle before correction, which is the estimation result of the system state, and the voltage phase difference between the measurement data from the existing measuring instruments and the highaccuracy measurement device, in the correction of the synchronous stability.
10. The power system stabilization method comprising:
 the power system stabilization analysis method according to claim 7;
 determining and storing an appropriate powercontrolled generator for preventing a power failure in the event of an assumed failure in the power system by using the synchronous stability after correction; and
 controlling the determined powercontrolled generator in the event of the assumed failure.
11. The power system stabilization method comprising:
 the power system stabilization analysis method according to claim 7;
 determining and storing an appropriate powercontrolled generator for preventing a power failure in the event of an assumed failure in the power system by using the synchronous stability after correction;
 selecting one of the synchronization stability when not performing correction and when performing correction; and
 selecting the synchronous stability after correction when a difference between the synchronous stability before correction and after correction is equal to or greater than a threshold.
8190379  May 29, 2012  Rehtanz 
9077200  July 7, 2015  Majumder 
9178386  November 3, 2015  Duan 
9513648  December 6, 2016  Forbes, Jr. 
20030203717  October 30, 2003  Chuprun 
20120283967  November 8, 2012  Duan 
20180054058  February 22, 2018  Kumagai 
20180120818  May 3, 2018  Omi 
20180375329  December 27, 2018  Kuroda 
20190237997  August 1, 2019  Tsujii 
20190305590  October 3, 2019  Ito 
2013506389  February 2013  JP 
2016025715  February 2016  JP 
 International Search Report of PCT/JP2017/039308 dated Dec. 19, 2017.
Type: Grant
Filed: Oct 31, 2017
Date of Patent: Sep 14, 2021
Patent Publication Number: 20200251902
Assignee: HITACHI, LTD. (Tokyo)
Inventors: Yuki Tsujii (Tokyo), Masatoshi Kumagai (Tokyo), Kenedward Kawakita (Tokyo), Masahiro Watanabe (Tokyo)
Primary Examiner: Ramesh B Patel
Application Number: 16/652,091
International Classification: H02J 3/24 (20060101); H02J 13/00 (20060101); G05B 15/02 (20060101);