JP2008199739A - Method, device and program for analyzing voltage - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To analyze voltage fluctuations of a power system, to which a load fluctuation source is linked, in a short time. <P>SOLUTION: System sensitivity of busbar voltage with respect to changes in a reactive power load of the load fluctuation source is calculated, by using system impedance of the power system. A power fluctuation coefficient is calculated, based on a reactive power fluctuation amount calculated by using instantaneous reactive power of the load fluctuation source. The flicker value of a busbar is calculated by using system sensitivity and the power fluctuation coefficient. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a voltage analysis method, apparatus, and program. More specifically, the present invention relates to a voltage analysis method, apparatus, and program suitable for use in examining the influence of load fluctuations on an electric power system, such as an arc furnace, and in the specifications of a load fluctuation countermeasure apparatus.

  When power consumption equipment (load fluctuation source) with large load fluctuation such as an arc furnace is connected to the power grid, not only the voltage at various points of the power grid fluctuates due to load fluctuation, but also due to this fluctuation. This causes the problem of flickering lighting (such voltage fluctuation is also called voltage flicker). For this reason, power quality measures are taken by installing a countermeasure device such as a separately-excited SVC (Static Var Compensator) or a self-excited SVC which is a reactive power compensation device in the vicinity of these load fluctuation sources.

  Examination of the influence of the load fluctuation source on the power system when taking the above measures has been conventionally performed by time simulation such as analysis of power system transients (hereinafter referred to as EMTP) using a computer. (Patent Document 1).

JP 2002-238157 A

  However, since the pattern of load fluctuation is enormous, the conventional method based on time simulation such as EMTP analysis requires enormous time to calculate the voltage fluctuation of the power system. Further, when considering the application of separately-excited SVC or self-excited SVC as a countermeasure against voltage flicker, the time width of time simulation needs to be set to around 10 μs in order to operate these SVCs at high speed, and voltage flicker An analysis time of, for example, 60 seconds or more per temporary point is required to obtain the ΔV10 value that is an index of evaluation. Therefore, in a conventional method using time simulation such as EMTP analysis, a reactive power compensator used as a countermeasure device An enormous amount of time is required to calculate the capacity of the converter. For this reason, the conventional method based on time simulation such as EMTP analysis cannot be said to be a method suitable for quick examination, and is a method suitable for examining many alternatives for voltage flicker countermeasures in the power system. It's hard to say.

  Therefore, an object of the present invention is to provide a voltage analysis method, apparatus, and program capable of analyzing in a short time voltage fluctuations in a power system connected to a load fluctuation source.

  Note that the ΔV10 value is an index used for evaluating voltage flicker caused by load fluctuations in a steel arc furnace or the like, and is an index indicating the flickering condition of electric lighting (for example, Power System Utilization Council: Power System (See Use Council Rules, 8th June 13, 2006, p. 44). Hereinafter, the ΔV10 value is referred to as a flicker value.

  In order to achieve this object, the voltage analysis method according to claim 1 calculates the system sensitivity, which is the sensitivity of the bus voltage to the change of the reactive power load of the load fluctuation source, using the system impedance of the power system, and The power fluctuation coefficient is calculated based on the reactive power fluctuation amount calculated using the instantaneous reactive power of the source, and the bus flicker value is calculated using the system sensitivity and the power fluctuation coefficient.

  According to a second aspect of the present invention, there is provided a voltage analyzing apparatus comprising: means for calculating a system sensitivity that is a sensitivity of a bus voltage to a change in a reactive power load of a load fluctuation source using a system impedance of the power system; Means for calculating reactive power fluctuation using power, means for calculating power fluctuation coefficient based on reactive power fluctuation, and means for calculating flicker value of bus using system sensitivity and power fluctuation coefficient To have.

  Further, the voltage analysis program according to claim 3 is a computer that can access a database in which system impedance data of an electric power system is recorded. The sensitivity of the bus voltage to the change of the reactive power load of the load fluctuation source using the system impedance data. Processing for calculating system sensitivity, processing for calculating reactive power fluctuation amount using instantaneous reactive power of load fluctuation source, processing for calculating power fluctuation coefficient based on reactive power fluctuation amount, system sensitivity and power The processing for calculating the flicker value of the bus using the variation coefficient is performed.

  Therefore, according to the voltage analysis method, apparatus, and program, the system sensitivity, which is an index calculated using the system impedance of the power system and is the sensitivity of the bus voltage to the change of the reactive power load of the load source, and the load fluctuation Since the bus flicker value is calculated using the power fluctuation coefficient based on the reactive power fluctuation amount calculated using the instantaneous reactive power of the source, the voltage analysis of the power system using the sensitivity analysis is performed. .

  According to the voltage analysis method, apparatus, and program of the present invention, it is possible to perform voltage analysis of the power system by sensitivity analysis using the system sensitivity of load fluctuation and the power fluctuation coefficient reflecting the characteristics of the power system. Compared with the conventional method based on time simulation, the voltage fluctuation of the power system can be analyzed in a short time. As a result, it is possible to detect problems in the power system from the viewpoint of voltage fluctuations, and it is possible to evaluate many alternatives when considering countermeasures to improve the speed of voltage fluctuation compensation work in the power system. Improvement and accuracy improvement can be aimed at.

  Hereinafter, the configuration of the present invention will be described in detail based on the best mode shown in the drawings. In the present embodiment, the case where the present invention is applied to the power system 1 shown in FIG. 3 will be described. In FIG. 3, the code | symbol 2 points out the high-order system of the electric power grid | system 1 made into an analysis object by a present Example. In the power system 1, the bus Bn is connected to the bus B0 via the power transmission line 3 and the transformer 4, and the load fluctuation source Fn is connected to the bus Bn. In this specification, n = 1, 2, 3,.

  1 to 4 show an example of embodiments of the voltage analysis method, apparatus, and program of the present invention. This voltage analysis method calculates the system sensitivity, which is the sensitivity of the bus voltage to changes in the reactive power load of the load fluctuation source, using the system impedance of the power system, and the reactive power calculated using the instantaneous reactive power of the load fluctuation source. The power fluctuation coefficient is calculated based on the power fluctuation amount, and the bus flicker value is calculated using the system sensitivity and the power fluctuation coefficient.

  As shown in FIG. 1, the voltage analysis method includes power system tidal conditions such as system impedance data of an analysis target power system, values of active power / reactive power flowing through a transmission line, and voltage values of a substation. (S1) for reading (hereinafter referred to as system impedance, etc.), and the system sensitivity, which is the sensitivity of the bus voltage to the change in the reactive power load of the load fluctuation source using the system impedance read in the processing of S1 A step of calculating (S2), a step of calculating a reactive power fluctuation amount using the instantaneous reactive power of the load fluctuation source (S3), and a power fluctuation coefficient based on the reactive power fluctuation amount calculated in the process of S3 A step of calculating (S4), and a step of calculating the flicker value of the bus using the system sensitivity calculated in the process of S2 and the power fluctuation coefficient calculated in the process of S4 It is realized by the processing arrangement consisting of a S5).

  The voltage analysis method can be realized as the voltage analysis apparatus of the present invention. The voltage analysis apparatus of the present invention is a system sensitivity that is a sensitivity of a bus voltage to a change in a reactive power load of a load fluctuation source using means for reading data relating to an analysis of voltage fluctuation of the power system and a system impedance of the power system. Means for calculating the reactive power fluctuation amount using the instantaneous reactive power of the load fluctuation source, means for calculating the power fluctuation coefficient based on the reactive power fluctuation amount, and the system sensitivity and the power fluctuation coefficient. And a means for calculating the flicker value of the bus.

  The voltage analysis method and voltage analysis apparatus described above can also be realized by executing the voltage analysis program of the present invention on a computer. In the present embodiment, a case where the voltage analysis program is executed on a computer will be described as an example.

  FIG. 2 shows an overall configuration of the voltage analysis apparatus 10 of the present embodiment for executing the voltage analysis program 17. The voltage analysis apparatus 10 includes a control unit 11, a storage unit 12, an input unit 13, a display unit 14, and a memory 15, and is connected to each other by a signal line such as a bus. A data server 16 is connected to the voltage analysis apparatus 10 via a communication line or the like, and signals such as data and control commands are transmitted / received (input / output) to / from each other via the communication line.

  The control unit 11 performs calculations related to control of the entire voltage analysis apparatus 10 and analysis of voltage fluctuations of the power system by the voltage analysis program 17 stored in the storage unit 12, and is, for example, a CPU. The storage unit 12 is a device that can store at least data and programs, and is, for example, a hard disk. The input unit 13 is an interface for giving at least an operator's command to the control unit 11, and is, for example, a keyboard. The display unit 14 displays characters, graphics, and the like under the control of the control unit 11 and is, for example, a display. The memory 15 becomes a memory space that is a work area when the control unit 11 executes various controls and calculations. The data server 16 is a server capable of storing at least data.

The control unit 11 of the voltage analysis device 10 executes a voltage analysis program 17 to read data related to the analysis of voltage fluctuations in the power system,
A system sensitivity calculation unit 11b that calculates the system sensitivity, which is the sensitivity of the bus voltage to changes in the reactive power load of the load fluctuation source using the system impedance and the like, and the reactive power fluctuation amount using the instantaneous reactive power of the load fluctuation source Reactive power fluctuation calculation unit 11c that performs calculation, power fluctuation coefficient calculation unit 11d that calculates a power fluctuation coefficient based on the reactive power fluctuation amount, and flicker value calculation of the bus using the system sensitivity and the power fluctuation coefficient Flicker value calculation unit 11e is configured.

  In executing the voltage analysis method of the present invention, first, the data reading unit 11a of the control unit 11 reads the system impedance and the like of the power system 1 to be analyzed used for calculating the system sensitivity, which is the process of S2 (S1). ).

  The system impedance data is the impedance value of the system calculated from the data of the generator load and the transmission line in the power system, and the customer load that is not the load fluctuation source, and the arrangement of them is also called the system impedance map. Since the creation of the system impedance map itself is a well-known technique, details are omitted here (for example, Yoshiyasu Okawa: Understanding short-circuit protection coordination Practical short-circuit calculation of high-voltage demand equipment, Ohm, ISBN 4-274-50017-9, Or, see the Institute of Electrical Engineers, Power System Model Standardization Investigation Special Committee: Standard Model of Power System, IEEJ Technical Report No. 754).

  The system impedance and the like are stored in advance in the data server 16 as the system impedance database 18. Then, the data reading unit 11 a reads values such as the system impedance of the power system 1 to be analyzed from the system impedance database 18 and stores them in the memory 15. When data in a range not limited to the power system 1 to be analyzed is accumulated in the system impedance database 18, the data reading unit 11a reads only data related to the power system 1 to be analyzed. And stored in the memory 15.

  Next, the system sensitivity calculation unit 11b of the control unit 11 calculates the system sensitivity Z using the system impedance read in the process of S1 (S2).

  The system sensitivity Z represents the sensitivity of the voltage of each bus Bn to the load fluctuation of each load fluctuation source Fn. That is, the magnitude of the system sensitivity Z represents the degree of influence of each load fluctuation source Fn on each bus Bn. Specifically, the system sensitivity Z is calculated by Equation 1 from the change amount ΔI_fn of the load current and the voltage change amount ΔVbn_fn of each bus Bn when the reactive power load of the load change source Fn changes 0.1 [pu]. Is done. The system sensitivity Z is uniquely determined by the system configuration.

(Expression 1) Zbn_fn = ΔVbn_fn / ΔI_fn
Here, Zbn_fn: sensitivity of voltage of bus Bn to load fluctuation of load fluctuation source Fn, ΔVbn_fn: fluctuation amount of voltage of bus Bn to load fluctuation of load fluctuation source Fn, ΔI_fn: reactive power load of load fluctuation source Fn is 0 .1 [pu] Change in load current when changed. However, n = 1, 2, 3,.

  When a plurality of load fluctuation sources are linked to one bus Bn, the sum of the load fluctuations of the load fluctuation sources may be used as the value of the load fluctuation source Fn of the bus Bn. Specifically, for example, when two load fluctuation sources Fn-1 and Fn-2 are connected to the bus Bn and the change amounts of the load currents are ΔI_fn1 and ΔI_fn2, the change amount of the load current ΔI_fn. As a value, ΔI_fn = ΔI_fn1 + ΔI_fn2 may be used.

  The system sensitivity calculation unit 11b reads the system impedance and the like of the power system 1 from the memory 15 and calculates the system sensitivity Zbn_fn with respect to the load fluctuation of each load fluctuation source Fn for each bus Bn using Equation 1. Then, the system sensitivity calculation unit 11b stores the calculated system sensitivity Zbn_fn in the memory 15.

  Next, the reactive power fluctuation amount calculating unit 11c of the control unit 11 calculates the reactive power fluctuation amount ΔQ (S3).

  The reactive power fluctuation amount ΔQ is calculated by FFT analysis. Since FFT analysis itself is a well-known technique, details are omitted here (for example, Toichi Machida and Norio Kojima: FORTRAN Applied Numerical Calculations, pp. 94-119, Tokai University Press, ISBN 4-486-01050-7). Or, Shinichi Koike: Science and Technology Calculation by C, pp. 257-263, CQ Publisher, ISBN 4-7898-3029-2).

  In the present invention, the reactive power fluctuation amount ΔQ_bn between the bus B0 and the bus Bn is calculated by FFT analysis using the three-phase instantaneous reactive power Q_fn of the load fluctuation source Fn. At this time, when the reactive power compensator 5 is connected to the bus Bn, the instantaneous reactive power after compensation by the reactive power compensator 5 is calculated by FFT analysis, and the reactive power compensation device 5 is invalid based on the instantaneous reactive power after compensation. A power fluctuation amount ΔQ_bn is obtained. Hereinafter, the reactive power fluctuation amount ΔQ_bn between the bus B0 and the bus Bn is referred to as a reactive power fluctuation amount related to the bus Bn. The present invention can be applied to both cases where the reactive power compensator 5 is a separately excited SVC and a self-excited SVC.

  Data used for FFT analysis such as instantaneous reactive power of the load fluctuation source Fn is stored in advance in the data server 16 as the FFT analysis database 19. When the reactive power compensator 5 is linked to the bus Bn, data related to the specifications of the reactive power compensator 5 such as the capacity of the converter is also stored in the FFT analysis database 19.

  The data reading unit 11 a reads values such as instantaneous reactive power of the load fluctuation source Fn and data related to the specification of the reactive power compensator 5 from the FFT analysis database 19 and stores them in the memory 15. Then, the reactive power fluctuation amount calculation unit 11 c stores the calculated value of the reactive power fluctuation amount ΔQ_bn related to the bus Bn in the memory 15.

  Next, the power fluctuation coefficient calculation unit 11d of the control unit 11 calculates the power fluctuation coefficient ΔQ10 using the value of the reactive power fluctuation amount ΔQ calculated in the process of S3 (S4).

  The power fluctuation coefficient ΔQ10 is a variable that allows the sensitivity analysis to be applied to the voltage analysis of the power system by using it in combination with the system sensitivity Z, and the flicker value ΔV10 reflecting the system sensitivity Z can be calculated. It is a variable to make it possible. Hereinafter, the power variation coefficient ΔQ10 between the bus B0 and the bus Bn is referred to as a power variation coefficient related to the bus Bn and is expressed as ΔQ10_bn.

  The power fluctuation coefficient ΔQ10_bn related to the bus Bn is obtained from the reactive power fluctuation amount ΔQ_bn related to the bus Bn using Equation 2 in the same manner as the flicker value ΔV10. The calculation of the flicker value ΔV10 and the calculation of the power fluctuation coefficient ΔQ10 are different in that the input of the flicker value ΔV10 calculation is a line voltage, whereas the input of the power fluctuation coefficient ΔQ10 calculation is an instantaneous reactive power. Further, the flicker value ΔV10 is calculated for each line voltage, whereas the power variation coefficient ΔQ10 is calculated using three-phase instantaneous reactive power.

ここに、ΔＱ10：電力変動係数，ΔＱ：無効電力変動量［ｐｕ］，α：ちらつき視感度係数。また、bn：母線Ｂｎに係る変数であることを表す，ｋ：変動周波数ｆの識別子（ｋ＝１，２，３，…）。

Here, ΔQ10: power fluctuation coefficient, ΔQ: reactive power fluctuation amount [pu], α: flicker visibility coefficient. Further, bn: a variable relating to the bus Bn, k: an identifier of the fluctuation frequency f (k = 1, 2, 3,...).

  FIG. 4 shows the flicker sensitivity coefficient for each variation frequency used in Equation 2. Specifically, a combination of a fluctuation frequency fk to which a black circle is given in the drawing and a corresponding visibility coefficient αk is used. Note that the value of the fluctuation frequency fk and the corresponding visibility coefficient αk are defined in advance in the voltage analysis program 17.

  The power fluctuation coefficient calculation unit 11d reads the value of the reactive power fluctuation amount ΔQ_bn from the memory 15, and calculates the power fluctuation coefficient ΔQ10_bn for each bus Bn using Expression 2. Then, the power fluctuation coefficient calculation unit 11d stores the calculated value of the power fluctuation coefficient ΔQ10_bn for each bus Bn in the memory 15.

  Next, the flicker value calculation unit 11e of the control unit 11 calculates the flicker value ΔV10 using the system sensitivity Z calculated in the process of S2 and the power fluctuation coefficient ΔQ10 calculated in the process of S4 (S5).

  Here, the relationship between the voltage fluctuation amount ΔV and the reactive power fluctuation amount ΔQ is expressed by Equation 3 where the reactance is X.

    (Equation 3) ΔV = X · ΔQ

  Assuming that the resistance of the bus can be ignored, Equation 4 is established for the system sensitivity Z.

    (Expression 4) Z = X = ΔV / ΔQ

  When the relationship of Equation 4 is used, the relationship of Equation 5 is approximately derived between the power variation coefficient ΔQ10 and the flicker value ΔV10. Note that Formula 5 is approximately derived as a scalar that is a variable having only magnitude information, and is not a vector that is a variable having two information of magnitude and phase. Absent.

    (Equation 5) ΔV10 = (ΔV / ΔQ) · ΔQ10 = Z · ΔQ10

  Here, when there are N load fluctuation sources Fn in the system to be analyzed as in the power system 1 of the present embodiment, severe conditions regarding the flicker value ΔV10, that is, a plurality of arc furnace currents are substantially in phase. And ΔV10_bn of the bus Bn is calculated by Equation 6 using the superposition theory. Since the reason for overlapping is a well-known technique, details are omitted here (for example, Izumi Arima and Harumitsu Iwasaki: Basic Electric Circuit 1, Morikita Publishing Co., Ltd., pp. 73-75, ISBN 4-627-73180-9) reference).

(Expression 6) ΔV10_bn = (Zbn_f1 · ΔQ10_b1 + Zbn_f2 · ΔQ10_b2 ++...
+ Zbn_fi ・ ΔQ10_bi)
The variable i corresponds to the identifier n of the load fluctuation source F, and the maximum value of the variable i is n.

  The flicker value calculation unit 11e reads the values of the system sensitivity Zbn_fn and the power fluctuation coefficient ΔQ10_bn from the memory 15, and calculates the flicker value ΔV10_bn for each bus Bn using Equation 6. The flicker value calculation unit 11e stores the calculated flicker value ΔV10_bn for each bus Bn in the memory 15.

  Based on the magnitude of the flicker value ΔV10_bn for each bus Bn calculated as described above, the operator can determine whether there is a problem in the power system 1 from the viewpoint of voltage fluctuation.

  Further, when it is considered that the flicker value ΔV10_bn is large and needs to be improved, for example, when the capacity of the converter of the reactive power compensator 5 is changed or the reactive power compensator 5 is newly connected. It is also possible to evaluate the effect of suppressing the voltage fluctuation in the case of the case. In that case, it is possible to compare the case where the separately excited SVC is used as the reactive power compensator and the case where the self-excited SVC is used, or the case where the installation point of the newly installed SVC is changed. is there. Since the present invention can analyze the voltage fluctuation of the power system in a short time, it can compare and evaluate a large number of improvement alternatives compared with the case of analyzing using the conventional time simulation. Therefore, it is possible to evaluate a large number of improvement alternatives when considering problem improvement measures, and to improve the speed and accuracy of voltage fluctuation compensation work for the power system.

  In addition, although the above-mentioned form is an example of the suitable form of this invention, it is not limited to this, A various deformation | transformation implementation is possible in the range which does not deviate from the summary of this invention.

It is a flowchart explaining an example of embodiment of the voltage analysis method of this invention. It is a functional block diagram of the voltage analysis apparatus in the case of implementing the voltage analysis method of this embodiment using a program. It is a figure which shows the structure of the electric power system of the analysis object of this embodiment. It is a figure which shows the visibility curve according to fluctuation frequency.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electric power system 5 Reactive power compensator B0, B1, B2, B3, ..., Bn Bus line F1, F2, F3, ..., Fn Load fluctuation source

Claims (3)

  Based on the reactive power fluctuation amount calculated using the instantaneous reactive power of the load fluctuation source and calculating the system sensitivity that is the sensitivity of the bus voltage to the reactive power load change of the load fluctuation source using the grid impedance of the power grid A voltage analysis method characterized by calculating a power fluctuation coefficient and calculating a flicker value of a bus using the system sensitivity and the power fluctuation coefficient.   Reactive power fluctuation amount is calculated using means for calculating the system sensitivity, which is the sensitivity of the bus voltage to the change of the reactive power load of the load fluctuation source using the system impedance of the power grid, and the instantaneous reactive power of the load fluctuation source. Voltage analysis means comprising: means; a means for calculating a power fluctuation coefficient based on the reactive power fluctuation amount; and a means for calculating a bus flicker value using the system sensitivity and the power fluctuation coefficient. apparatus.   A computer that can access a database in which system impedance data of a power system is recorded, a process of calculating a system sensitivity that is a sensitivity of a bus voltage to a change in a reactive power load of a load fluctuation source using the system impedance data, and A process of calculating a reactive power fluctuation amount using instantaneous reactive power of a load fluctuation source, a process of calculating a power fluctuation coefficient based on the reactive power fluctuation quantity, and a bus using the system sensitivity and the power fluctuation coefficient A voltage analysis program for performing a process of calculating a flicker value of.

Images