JPH0438124A - Overload eliminating method and device for power system and low voltage eliminating method for power system - Google Patents

Abstract

PURPOSE:To reduce power interruption section as small as possible and to enhance reliability in power supply by estimating power flow at each point in a system, upon removal of fault, based on data relevant to power generation amount and load amount at each point in the system immediately before occurrence of fault. CONSTITUTION:A computer is actuated by a fault detection signal such as function of a protective relay. Configuration of the system after removal of fault is recognized and power flow at each point is estimated based on collected data PGN, PLM and then overload points in the system are determined based on thus estimated power flow. If there is no overload, the process is completed. If there is any overload, power generation limit of each generator for eliminating the overload is determined through phase regulation of the generator, and one or a plurality of loads PLM corresponding to the overload are selected, as required. Power generation limit, and a generator to be limited or a load interrupting amount and a load to be interrupted are determined based on these results and a control command such as an interruption command is outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an overload elimination method and device for eliminating overload or low voltage in various parts of a power system that occurs after an accident has been eliminated, or a low voltage elimination method.

[Prior Art] Conventionally, as a method for resolving overload after a power grid accident, the method described in [Electrical Science Handbook, Volume 20 Power System, Page 1060, Overload Control System for Power Transmission Lines] has been known. There is. According to this, the current of the power transmission line to be protected is monitored, and when the current exceeds a certain value, the power transmission line is cut off, thereby preventing the power transmission line from fusing due to overload.

[Problem to be solved by the invention]

However, the above-mentioned conventional technology only considers the prevention of power line blowouts, and does not take into account the prevention of a decline in the power supply reliability of the entire system when solving overloads such as preventing blowouts. There's a problem.

That is, the range of system loads to be cut off is too wide, and more loads than are necessary to eliminate the overload may be cut off, resulting in a problem that the power outage section extends over a wide range and the reliability of supply decreases. Additionally, depending on the system configuration after the fault has been removed, the power transmission route may become longer and lower voltage areas may occur or expand.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method and apparatus for eliminating overload in a power system, which improves supply reliability by reducing power outage sections as much as possible.

Another object of the present invention is to provide a method for eliminating a voltage drop in an electric power system that effectively prevents a voltage drop after a fault has been removed and improves supply reliability.

[Means to solve the problem]

In order to achieve the above-mentioned object, the overload elimination method and device according to the present invention recognizes a new system configuration after an accident is removed based on accident information of the target power system, and determines the new system configuration after the accident is removed. The power flow in each part of the system is estimated using the power generation amount and load amount data before the accident, and based on the estimation results, it is determined whether each part of the system is overloaded, and the overload of the system part determined to be overloaded is determined. The power generation limit amount of a plurality of generators necessary to solve the problem is calculated, and the power generation amount of the generator with the smallest power generation limit amount as a result of the trial calculation is limited.

Moreover, instead of or in addition to limiting the amount of power generation, one or more load systems with a load commensurate with the overload amount are selected, and the selected load systems are shut off.

In addition, the low voltage elimination method according to the present invention recognizes the system configuration after the fault has been removed based on the fault information of the target power system, and calculates the power flow of each part of the system in the system configuration after the fault has been removed before the accident occurred. While estimating the power generation amount and load amount data in the system, it also detects the presence or absence of low voltage in each part of the system, and contributes to eliminating the low voltage in the detected system part. A trial calculation is performed to change the configuration by opening and closing the circuit breaker of the power transmission system, and the circuit breaker of the power transmission system is opened and closed based on the result of the trial calculation.

[Effect]

With this configuration, according to the present invention, the above object is achieved through the following actions.

First, the power flow in each part of the system after the fault has been removed is estimated using data on the amount of power generation and load in each part of the system immediately before the accident, so overload or undervoltage in each part of the system can be estimated quickly and with high accuracy. can.

Then, by calculating the power generation amount limit, it is possible to eliminate overload and load on each part with the minimum power generation amount limit, and unnecessary load shedding can be avoided, thereby improving supply reliability.

In addition, by selecting and cutting off one or more system loads commensurate with the amount of overload, unnecessary load shedding can be avoided, thereby minimizing power outage sections and improving supply reliability. do.

Furthermore, by combining the power generation amount limitation with selective load shedding, it becomes possible to cope with overloads that cannot be resolved by power generation amount limitation alone, and the - layer supply reliability is improved.

On the other hand, according to the method for eliminating low voltage according to the present invention, a circuit breaker in the power transmission system is opened and closed by calculation to try to change the system configuration, thereby finding a system configuration that can eliminate low voltage,
The necessary circuit breakers are opened and closed accordingly. Therefore, it is possible to promptly eliminate the low voltage and prevent unnecessary load shedding due to the low voltage.

〔Example〕

Hereinafter, the present invention will be explained based on examples.

FIG. 1 shows a flowchart of a processing procedure related to an overload elimination method according to an embodiment of the present invention.

The computer constituting the overload elimination device is shown in Figure 1 (A
), the power generation amount PGN and load amount PLO detected by the power detection means provided in each part of the target power system are taken in at a fixed sampling period and stored in a storage device for collection. It has become. Here, the subscript GN represents the number of the generator, and N=1.2. ...N,
..., where the subscript LM represents the number of the system load that can be appropriately separated by the circuit breaker, and M=
It shall consist of 1.2°...9M,...

Next, the computer is activated by an accident detection signal such as a protection relay operation, as shown in FIG. Calculate the power flow of each part by estimation calculation using LM (steps 103 and 104),
Based on this, it is determined whether there is an overloaded system part (step 1o5).

If there are no overloaded locations, the process ends. If there is an overloaded point, find the power generation limit amount of each generator that can eliminate the overload by limiting the power generation amount by adjusting the generator phase, and if necessary, calculate one or more power generation limits corresponding to the overload amount. A load PLM is selected (step 106). Based on these results, a power generation amount limit, a limited generator, a load cutoff amount, and a cutoff load are determined, and a control command such as a cutoff command is output (step 107).

Here, details of the processing in each of the above steps will be explained.

Recognizing the system configuration requires information related to the overall system configuration, and recognizing the system configuration after the accident has been removed requires accident information such as operating breakers related to the accident removal. . Information regarding the former system configuration is stored in advance in the storage device as system configuration data, and includes, for example, generator GN, transmission line QK, load LM, their capacities, attribute data such as allowable capacity, impedance, and position of circuit breakers. and attribute data such as connection information. The latter accident information is input from a separate accident detection device or the like. Therefore, step 10 of system configuration recognition
In step 2, it is activated when an accident detection signal is input, reads system configuration data as necessary, and grasps and sets the system configuration after the accident has been removed in accordance with the accident information.

Next, in step 103, data such as the amount of power generation before the accident collected in step 101 P ON , P
Data PG that imports LM and uses it for power flow estimation calculation
Set N, PLM.

The power flow estimation calculation step 104 calculates the power flow in each part of the system using the power generation amount PGN and the load amount PLM before the accident, which are set for the set post-accident system configuration.

In step 105, the presence or absence of an overloaded portion is determined based on whether or not the power flow of each part determined above exceeds the allowable capacity of each part. The allowable capacity of each part is read from the storage device as necessary. As a result of this determination, if an overloaded location exists, in the next step 106, trial calculations are performed to limit the amount of power generation and to cut off the load in order to eliminate the overload at each location.

This trial calculation is to find a solution method that provides the smallest amount of power generation restriction or cut-off load for the amount of overload to be eliminated. Specifically, as explained below, the effect coefficient for each solution method is calculated. calculate. Then, as a result, the power generation amount is limited by the method with the smallest coefficient.

For example, assume that the system configuration after the fault has been removed is as shown in FIG. 2, and that an overload has occurred on the line Q. in this case,
By adjusting the phase of generator G and changing the phase difference θ of generator G2, which is an equivalent infinite bus, generator G
The overload on the line Q1 can be eliminated by reducing the power supplied to the load from the line Q1. Here, by limiting the output of the generator G from Pa to Pc, the line Q
When the electric power changes from PQ to PQ', the effect coefficient C is defined by the following equation.

P (11-PQ) And to eliminate the overload at the target location Ω, limit the power generation amount of the generator with the smallest effect coefficient C to eliminate the overload. Cut off the load and eliminate the overload. The same way of thinking can be used in this case.

In addition, the effect coefficient C is the overload cancellation amount for the power generation amount limitation or load shedding when power generation amount limitation or load shedding is performed under system conditions that are targeted in advance, for example, when one or two lines of the line are open. It is possible to calculate the limit amount, etc. by calculating the ratio (the above-mentioned effect coefficient) and multiplying the actual overload amount by the effect coefficient. That is, line Q
When reducing the power of □ from P3 to Pl to eliminate the overload, the power generation limit amount ΔPa may be calculated using the following equation.

Δp Gz == c x (P 3 P) The degree of overload cancellation differs depending on the point where power generation amount is restricted, etc., so calculate each case of restriction, and select and limit the most effective point. There is a need. Furthermore, since the effects differ depending on the system configuration, it is necessary to obtain the aforementioned effect coefficients for each system configuration.

In addition, priority is given to eliminating overloads by limiting the amount of power generated by generators.
If this alone cannot resolve the overload, a combination may be used to perform load shedding.

Next, a specific example will be explained. In the system shown in Figure 3, G and G2 are generators, L and L2 are loads, and CB1
~CB represents a circuit breaker, Q1 to Q3 represent a power transmission line, and B to B4 represent a busbar, respectively.

Point F of transmission line Q3 in the system shown in FIG.

If an accident occurs, circuit breaker CB3. This will remove the effects of the accident by cutting off the CB. At that time, the power transmission line Q2 becomes overloaded and may be cut off, so in the conventional system, the load L1. Since L2 was being cut off, the reliability of supply was decreasing.

Therefore, as shown in the same figure, current transformers CT□ and CT2
The normal power flows P and P2 are detected through the communication means C4 and C05, and the detected data is sent to the overload elimination device 10 through the communication means C4 and 05.
0, and if the circuit breakers CB and CB4 are shut off due to accident elimination, processing is performed according to the procedure shown in FIG. 1(B). In other words, the allowable capacity PQ of the power transmission line Q2
2 and power flow P i lP2, overload amount △PL2=P
Find Q2- (P□+p2), and in order to bring this value closer to zero, limit the amount of power generated by generator G or G2, which has a small effect coefficient, or cut off the load L or L2 that is closest to that value.

Therefore, according to this embodiment, it is possible to minimize the amount of generator restriction or the amount of load cutoff for overload cancellation, and the reliability of power supply can be improved.

Note that the power flow calculation in step 104 in FIG. 1 is performed using the so-called direct current method, so that the power flow can be calculated in a speedy manner that eliminates accidents. In other words, the assumptions are that the bus voltage is maintained at approximately the nominal voltage value, that the phase difference between the bus voltages of adjacent electrical stations is relatively small, that the line resistance is small compared to the actance, and that the capacitance is If you ignore the minute,
Power flow calculation requires the distribution of active power and the phase angle distribution of each bus voltage.

In general, the power P between two electrical components is E2.・・・・・・(1)
It is expressed as p = -s x nθ. Here, E 2 is the internal voltage,
is the actance between two points, and θ is the phase difference between the two points.

Inserting the above assumption into this equation, θ P″ knee...
...(2) becomes. Here, θ is the voltage V, and X is the resistance r
By setting it at , the electric power P can be applied as a current i.

Therefore, the system expressed based on the idea of equation (2) is treated as a DC circuit, the current of each line is determined, the presence or absence of overload is determined, and if there is an overloaded area, the power generation amount is limited or The effect coefficient on overload elimination when load limiting is calculated is calculated, and the location where the effect is greatest is limited.

FIG. 4 shows a specific embodiment for eliminating low voltage. In the same figure, when an accident occurs at point F2, circuit breaker CB shuts off CB2 to eliminate the effects of the accident, but at this time, the output of generator G1 changes to transmission line Q0. Load L0. through Q2. There is a part supplied to L2, which supplies power to the load through a large impedance, so bus B
2 voltage decreases. Therefore, the low voltage elimination device 200 uses data on the power generation amount and load amount of the system, including the voltage of the bus B2, which was collected periodically through the voltage transformer PT and the communication means C2 during normal times before the accident. , and communication means C
Based on the accident information including the opening operation information of the circuit breaker CB provided through □, the system configuration after the accident has been removed is recognized, and based on this, the presence or absence of low voltage in each part of the system is determined. If there is a low voltage point below a certain voltage with respect to a predetermined voltage, a trial calculation of system change by operating a circuit breaker is performed, and a change in the power transmission route that can eliminate the low voltage is considered. As a result of this study, by opening circuit breaker CB5 and supplying power to load L2 via power transmission line Q3,
When it is determined that the low voltage on the bus B2 has been resolved, a disconnection command is issued to the circuit breaker CB via the communication means C3 to disconnect the buses B3 and B4. As a result, bus B2 and transmission line Q
The load on B2 is reduced by L0, and a voltage drop on bus B2 can be prevented.

〔Effect of the invention〕

As explained above, according to the present invention, power flow calculations for each part of the system are performed for the system configuration after the accident is removed using data on the amount of power generation and load before the accident, and based on this, the presence or absence of overloaded points is determined. The system then calculates the amount of power generation restriction or load shedding that contributes to eliminating overloads, and selects the most effective restriction, thereby minimizing power outage sections and thereby reducing power consumption. Supply reliability can be improved.

In addition, in the same way, we will determine the presence or absence of low voltage points after the fault has been removed, and estimate the system configuration changes that will contribute to eliminating the low voltage.
Since the circuit breaker is opened and closed based on the results, it is possible to effectively prevent voltage drop after the fault has been cleared.
The reliability of power supply can be improved.

[Brief explanation of the drawing]

Figures 1 (A) and (B) are flowcharts showing the processing procedure of an embodiment of the present invention, Figure 2 is a diagram illustrating how to eliminate overload by limiting the amount of power generated, and Figure 3 is how to eliminate overload according to the present invention. A power system configuration diagram obtained by applying an example for explaining the method,
FIG. 4 is a power system configuration diagram to which an embodiment is applied for explaining the low voltage solution method of the present invention. 100... Overload elimination device, 200... Low voltage elimination device. Figure 2 Figure 3

Claims (1)

[Claims] 1. Recognize the system configuration after the accident is removed based on the accident information of the target power system, and calculate the power flow of each part of the system in the system configuration after the accident is removed from the power generation amount before the accident occurred. Estimation is made using load amount data, the presence or absence of overload in each part of the system is determined based on the estimation result, and power generation restriction of multiple generators is necessary to eliminate the overload in the part of the system determined to be overloaded. 1. A method for eliminating overload in an electric power system, the method comprising: calculating a trial calculation amount, and limiting the power generation amount of a generator having the smallest power generation limit amount as a result of the trial calculation. 2. Recognize the system configuration after the accident is removed based on the accident information of the target power system, and calculate the power flow of each part of the system for the system configuration after the accident is removed using the power generation and load data before the accident. Based on the estimation results, the presence or absence of overload in each part of the system is determined, and when eliminating the overload of the system part determined to be overloaded, one or more loads with a load amount corresponding to the overload amount are determined. A method for overloading an electric power system, comprising selecting a system and cutting off the selected load system. 3. Recognize the system configuration after the accident is removed based on the accident information of the target power system, and calculate the power flow of each part of the system for the system configuration after the accident is removed using the power generation and load data before the accident. Based on the estimation results, the presence or absence of overload in each part of the system is determined, and when eliminating the overload in the system part determined to be overloaded, the number of generators required to eliminate the overload is determined. The power generation limit amount shall be estimated, and the power generation amount of the generator with the lowest power generation limit amount as a result of the trial calculation shall be limited, and if the above-mentioned overload cannot be eliminated even by the power generation amount limit, the amount that cannot be eliminated shall be compensated for. A method for overloading an electric power system, the method comprising selecting one or more load systems with a load amount and cutting off the selected load systems. 4. A system configuration data storage means that stores data regarding the system configuration of the target power system, and a system data collection means that periodically detects and stores data on the power generation amount and load amount of the power system; When an accident detection signal is input, the system configuration after the accident is removed is set based on the accident information related to the accident and the data regarding the system configuration, and the power flow of each part of the set system is collected by the system data collecting means. A power flow estimating means that estimates using the power generation amount and load amount data immediately before the accident stored in an overload determination means for determining the amount of overload, and a trial calculation of the limited power generation amount of multiple generators necessary to eliminate the overload of the system portion determined to be overloaded by the means, and A power system comprising: a limiting generator selection means for selecting a generator with a minimum power generation limit based on the result; and a power generation amount control means for outputting a control command to limit the amount of power generation of the selected generator. Overload release device. 5. Assuming an accident in the target power system, assuming the overloaded parts of the system configuration after the assumed accident is removed, and determining the limited amount of power generation of each generator necessary to eliminate the assumed overload. Based on this, the ratio of the power generation limit amount of each generator to the amount of overload relief at each overload site is determined in advance as an effect coefficient. Recognize the system configuration after the accident has been removed, estimate the power flow in each part of the system for the system configuration after the accident has been removed using the power generation and load data before the accident, and based on the estimation results, calculate the overload of each part of the system. determining the presence or absence of the overload, selecting a generator with the minimum effectiveness coefficient necessary to eliminate the overload of the system portion determined to be overloaded, and limiting the power generation amount of the selected generator. A method for resolving overloads in power systems. 6. A system configuration data storage means that stores data regarding the system configuration of the target power system, and a system data collection means that periodically detects and stores data on the power generation amount and load amount of the power system; Assuming in advance various types of accidents in the power system and overloaded parts in the system configuration after the accident is removed, the ratio of the amount of power generation restriction of the generator necessary to eliminate the overload to the amount of overload is used as an effect coefficient. When the set and stored effect coefficient storage means and the accident detection signal are input, the system configuration after the accident is removed is set based on the accident information related to the accident and the data regarding the system configuration, and the set system power flow estimating means for estimating the power flow in each part of the system using the power generation amount and load amount data immediately before the accident stored in the system data collection means; and the estimated power flow and the predetermined power capacity of each part of the system. Among the overload determination means that determines the presence or absence of overload in each part based on the above and calculates the amount of overload, and the generator that contributes to eliminating the overload of the system part determined to be overloaded by the means, limiting generator selection means for selecting a generator with a minimum effect coefficient from the effect coefficient storage means; and power generation amount control means for outputting a control command to limit the amount of power generation of the selected generator. Power system overload elimination device. 7. Recognize the system configuration after the accident is removed based on the accident information of the target power system, and calculate the power flow of each part of the system for the system configuration after the accident is removed using the power generation amount and load amount data before the accident. At the same time, it detects the presence or absence of low voltage in each part of the system, performs trial calculations on configuration changes by opening and closing circuit breakers in the power transmission system that contribute to eliminating the low voltage in the detected system parts, and calculates power transmission based on the results of the trial calculations. A method of resolving low voltage in an electric power system that includes opening and closing circuit breakers.