KR20100039602A - Method for determining optimal location and optimal resistive value of superconducting fault current limiter by sensitivity index of power change - Google Patents

Abstract

PURPOSE: A method for determining optimum position and resistance values of a superconductive limiter is provided to reduce stabilization costs of a power system by optimally protecting a power device and a load from a fault current in a power system. CONSTITUTION: A power value which is transmitted practically is calculated after applying a fault case and the power value transmitted in a steady state(S100). A PCA(Power Change between areas) valve is calculated by accumulating difference between two power values for a preset period(S200). The total of PCA values about the assumption accident of all locations in which a superconductive limier is installed is calculated(S300). A sensitive index of the power change is calculated using the change rate of the total of the PCA values for resistance variation of the superconductive limiter(S400). The position of an initial sensitive index is determined to the optimum position of the superconductive limiter(S500).

Description

Method for determining optimal location and optimal resistive value of superconducting fault current limiter by sensitivity index of power change}

The present invention relates to a method for determining the optimum position and the optimum resistance value of the superconducting fault current limiter in the power system, and in particular, for the protection of power equipment and high loads in large and complex power systems, the amount of power is changed to reduce the cost. A method for determining the optimum position and the optimum resistance value of the superconducting fault current limiter by the sensitivity of.

In addition to the ever-increasing power capacity, the grid linkage of distributed power generation has become more active in recent years. For this purpose, if the equipment such as a circuit breaker is changed or the existing system stabilization method is used, enormous costs are required, and system instability and power quality are deteriorated. As a solution to these problems, the development and commercialization of transmission and distribution current limiters using superconducting materials have emerged as new issues.

Many superconducting fault current limiters have been developed so far, but there are still various problems in their application to real systems. In order to solve these various problems and effectively apply them to the real system, it is necessary to first consider the optimal position of the superconducting fault current limiter, the optimum resistance value of the superconducting fault current limiter against short circuit accidents, and the protection coordination with the existing protection equipment. However, it has not been suggested how to determine the optimum position and the optimal resistance value of the superconducting fault current limiter which can have the best effect on the whole system considering the above.

The present invention effectively determines the optimal position and the optimal resistance value of the superconducting fault current limiter to optimize the protection of power devices and high loads against high-level fault currents in a large and complex power system, and to reduce the stabilization cost of the power system. It is a subject to provide a method to do this.

According to an aspect of the present invention, a power value transmitted when the power station is in a steady state at an arbitrary line position with respect to an assumed accident of a power system, calculates an actual transmitted power value by applying the assumed accident, and differs between the two power values. Accumulating for a predetermined time to obtain a PCA (Power Change Between Area) value defined by Equation 1 below; Obtaining, for each location to which the superconducting fault current limiter can be applied, a sum of PCA values for assumed accidents of all locations; Calculating a change rate of the sum of the PCA values with respect to the resistance change of the superconducting current limiter and calculating a sensitivity index (SI) of power change according to Equation 2 below; And determining the optimum position of the superconducting fault current limiter at a position where the sensitivity index is minimized.

[Equation 1]

[Equation 2]

는 상기 임의의 선로 위치에서 정상상태일 때 전송되는 전력값이고,

는 상기 상정사고를 적용하여 상기 임의의 선로 위치에서 실제 전송되는 전력값이고, 수학식 2에서 R_SFCL은 초전도 한류기의 저항값임.In Equation 1,

Is a power value transmitted when the steady state at the line position,

Is a power value actually transmitted at the arbitrary line position by applying the assumed accident, and R _SFCL in Equation 2 is a resistance value of a superconducting fault current limiter.

In one embodiment of the present invention, the method for determining the optimum position of the superconducting fault current limiter and the optimum resistance value, PCA for the assumed accident of all positions according to the resistance value of the superconducting current limiter with respect to the determined optimal position of the superconducting current limiter Calculating a sum of the values; And determining a resistance value of which the sum of the PCA values is the minimum as an optimum resistance value of the superconducting current limiter.

및

는 상기 전력계통 내의 지역(area)과 지역을 잇는 선로 또는 전력 전송량이 상대적으로 많은 선로에서 전송되는 전력값일 수 있다.In the calculating of the PCA value, the power value

And

May be a power value transmitted from a line connecting the area and the area in the power system or a line having a relatively large amount of power transmission.

According to another aspect of the present invention, in the method for determining the optimum position and the optimum resistance value of the superconducting fault current limiter installed in the power system, the sensitivity index (SI) of the power change defined by Equations 1 and 2 is the minimum Determine the optimum position of the superconducting fault current limiter, and when the superconducting fault current limiter is installed at the determined optimum position, determining the resistance value at which the sum of the PCA values for the assumed accident of all positions is the minimum as the optimum resistance value. The present invention provides a method for determining an optimum position and an optimum resistance value of a superconducting fault current limiter.

According to an aspect of the present invention, by effectively determining the optimal position and the optimum resistance value of the superconducting fault current limiter in a large and complex actual system, it is possible to reduce the cost of manufacturing and installing the superconducting fault current limiter, The same effect can be achieved for the entire system at the same cost.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, the embodiments of the present invention may be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below. The shape and the size of the elements in the drawings may be exaggerated for clarity and the same elements are denoted by the same reference numerals in the drawings.

1 is a flowchart illustrating a method of determining an optimum position and an optimum resistance value of a superconducting fault current limiter using a power change between area (PCA) and a sensitivity index (SI) according to an embodiment of the present invention. 2 illustrates an example of a power system to which the method for determining an optimum position and an optimum resistance value according to FIG. 1 may be applied.

In order to analyze the effect of the superconducting fault current limiter on the entire power system, the power transmitted through an arbitrary line position is used. In the present invention, the sensitivity of the power change defined based on the PCA value and the PCA value calculated as the difference between the transmitted power value and the actual transmitted power value in a steady state through an arbitrary line for an assumed accident at various positions. The index (SI) is developed and the sensitivity index (SI) is used to find the optimal position and the optimum resistance of the superconducting fault current limiter.

)을 산출하고, 상정사고를 적용하여 그 선로에서 실제 전송되는 전력값(

)을 산출한다(S100). 다시말해서, 전력 조류(power flow)를 계산하여 전력 조류의 방향을 결정하고, 임의의 선택된 선로에서 정상상태일 때 전송되 는 전력값(

)을 결정하고, 각 위치에 상정사고를 적용하여 상기 임의의 선택된 선로에서 전송되는 실제 전력값(

)을 산출한다. First, it transmits when the system is in a steady state on an arbitrary line (for example, a line connecting a region or a region or a line with a large amount of power transmission) through a power flow analysis for a fault-case of a power system. Power value

) And apply the assumed accident to the actual power value (

) Is calculated (S100). In other words, the power flow is calculated to determine the direction of the power flow and the power value transmitted when steady state on any selected line.

) And apply an assumed accident at each location to determine the actual power value (

) Is calculated.

,

)의 차이를 일정시간 동안 누적하여 아래 수학식1에 의해 정의되는 PCA(Power Change between Area)값을 계산한다(S200). 여기서,

는 상기 일정시간의 시작시점이고,

는 상기 일정시간의 완료시점이다.Then, the two power values (

,

Cumulative difference for a predetermined time to calculate the PCA (Power Change between Area) value defined by Equation 1 (S200). here,

Is the starting point of the predetermined time,

Is the completion point of the predetermined time.

Then, for each position where the superconducting fault current limiter can be installed, when the superconducting fault current limiter is installed at the corresponding position, the sum of PCA values for the assumed accident at all positions is calculated (S300). In other words, the PCA value is repeatedly calculated for the resistance value of each superconducting fault current limiter, and the sum of PCA values obtained by applying the assumptions of all positions to each superconducting current limiter position is obtained. For example, when the superconducting fault current limiter is applied to a specific position L1, the superconductivity of the specific position L1 is added by adding PCA values for assumed accidents of all the positions L1, L2, L3 ..., L10. The sum of the PCA values for the current limiters can be obtained (see FIG. 2).

Then, as a change rate of the sum of the calculated PCA values with respect to the resistance change of the superconducting current limiter, a sensitivity index (SI) of power change defined as Equation 2 below is calculated (S400). At this time, the sensitivity index (SI) is calculated for each position of the superconducting fault current limiter, for example, the SI value at the superconducting fault current limiter position of L1 (that is, when the superconducting fault current limiter is installed at the L1 position), and the superconducting current limit of L2. It may be represented by the SI value or the like at the existing position (that is, when the superconducting fault current limiter is installed at the L2 position).

는 모든 위치의 상정사고에 대해 더한다는 것을 나타낸다. 따라서, 수학식 2에 의해 정의되는 SI값은 초전도 한류기 위치별로 계산된다. 예를 들어, L1의 초전도 한류기 위치에서의 SI값은, 초전도 한류기가 L1에 설치되어 있을 경우, 초전도 한류기의 저항에 따른 L1~L10의 상정사고를 적용한 PCA값들의 합의 변화율을 나타낸다. In Equation 2, R _SFCL denotes the resistance value of the superconducting fault current limiter, and the subscript LOCATION denotes the superconducting limiter position and indicates the sum.

Indicates that it adds to the assumption of all positions. Therefore, the SI value defined by Equation 2 is calculated for each superconducting fault current limiter position. For example, the SI value at the superconducting fault current limiter position of L1 represents the rate of change of the sum of PCA values applying the assumed accident of L1 to L10 according to the resistance of the superconducting fault current limiter when the superconducting fault current limiter is installed at L1.

가 초기의

로 신속히 안정화된다는 것을 의미한다. 따라서, SI가 더 작거나 더 음인(더욱 네가티브한) 값인 경우, 그에 대응하는 초전도 한류기 적용 위치는 전력계통의 안정화에 더욱 적합하게 된다. Then, the superconducting fault current limiter application position at which the sensitivity index (SI) is minimized (that is, the position having the smallest SI value or the highest negative value) is determined as the optimal position of the superconducting current limiter (S500). ). Small SI value after an assumed accident

Early

Means that it stabilizes quickly. Thus, if the SI is a smaller or more negative (more negative) value, the corresponding superconducting fault current limiter application position is more suitable for stabilization of the power system.

Next, a process of obtaining an optimum resistance value (total resistance value of the superconducting fault current limiter in the normal state) with respect to the superconducting current limit at the optimum position determined as described above will be described.

For the optimal position of the superconducting fault current limiter (that is, when the superconducting fault current limiter is installed at the optimum position), the sum of PCA values for all assumed phases according to the resistance value of the superconducting fault current limiter is calculated (S600). Then, the resistance value for minimizing the sum of the PCA values is determined as the optimum resistance value of the superconducting current limiter (S700).

FIG. 2 is an example of a power system to which the flowchart of FIG. 1 can be applied (IEEE benchmarked four-machine, two-area test system). Details of this system including system parameters are described in Praha Kundur, Power system Stability and Control. , EPRI Editors, McGraw-Hill, Inc., 1993, ISBN 0-07-035958-X.

As a result of calculating the power flow by system planning, the direction of the power flow is as indicated by the arrow of FIG. 2, and the active power supplied from the G1 generator and the G2 generator in the AREA 1 region is mostly LOAD. Consumed by one load, the remaining power (eg, 413 MW) is transferred from the AREA 1 region to the AREA 2 region. In the AREA 2 region, 413 MW of transmit power from the AREA 1 region and power from the G3 and G4 generators are consumed by the LOAD 2 load.

In the case of the superconducting fault current limiter, the effect of the superconducting fault current limiter (SFCL) on the entire system during an accident varies depending on the installation location depending on the amount of transmission power. For example, if an accident occurs at L3, SFCL behaves differently depending on whether it is located to the right or left of L3's base. The sensitivity index (SI) defined by Equation 2 is calculated to select the optimal position of SFCL in consideration of the amount of PCA in Equation 1.

가 초기의

로 빨리 안정화된다는 것을 의미한다. 그러므로, SI의 값이 더 작거나 음의 값을 갖게 되면, 그 해당위치가 더 최적위치가 된다. For sensitivity analysis depending on the application location of the SFCL, for example, a 100 ms three-phase short circuit fault can be applied. As the resistance value of SFCL changes, the small SI value in Equation 2 is actually changed after the accident.

Early

This means that it will stabilize quickly. Therefore, when the value of SI is smaller or has a negative value, the corresponding position becomes more optimal.

Tables 1 and 2 below show the sum of PCA values at each superconducting fault current limiter application location (sum of PCA values for all accidents) calculated as a result of applying the method of FIG. 1 to the power system of FIG. And SI. In this table, the PCA values are calculated based on the power transmitted at the L3 line location connecting AREA 1 and AREA 2.

TABLE 1

Sum of PCA values at each limiter application location

TABLE 2

SI at each current limiter application location

In Table 1, the sum of PCA values was calculated for R _SFCL = 0, 10 ohms and 20 ohms, respectively. The case of R _SFCL = 0 corresponds to the case where no superconducting fault current limiter is installed. In Table 2, SI calculated both the change rate of the sum of PCA when R _SFCL changed from 0 to 10 ohm and the change rate of PCA value when changed from 0 to 20 ohm.

As can be seen from Tables 1 and 2, for two different values of R _SFCL (10 ohm, 20 ohm), the reduction of the sum of the PCA values was greatest at the L3 position. Therefore, SI is the smallest at the L3 position, which means that the L3 position can be selected as the optimal position for the application of the superconducting current limiter (SFCL).

FIG. 3 is a graph of change in PCA sum (sum of PCA values for assumed accidents of all positions, that is, L1 to L10 positions) according to the resistance value of SFCL at the optimum position determined by the method of FIG. 1 for the system of FIG. . The optimal value of the R _SFCL that can be accepted at the optimal installation position was considered based on the PCA value of Equation 1, and when the SFCL was applied to the L3 position, the PCA sum was measured by changing the R _SFCL from 0 ohm to 40 ohm.

The minimum PCA sum is 1011 MW, and the corresponding R _SFCL is 20 ohms. If more than 20 ohms R _SFCL is used, the value of PCA sum and the corresponding SI obviously increases. This means that the optimum position L3 selected by sensitivity analysis is particularly effective when R _SFCL within 20 ohms is used.

4 is a graph showing the rotor speed response of four generators G1, G2, G3, and G4 when the superconducting fault current limiter SFCL is connected to the optimum position L3 in the power system of FIG. 4 (a) shows a case where an accident occurs in L3, and FIG. 4 (b) shows a case where an accident occurs in L1. SFCL, which draws different curves in each graph, has different values of resistance (20ohm, 10ohm).

When SFCL is applied to L3 in FIG. 2, the performance of SFCL to improve low-frequency oscillation damping is evaluated by applying a 100ms three-phase short circuit fault at two different locations L3 and L1. The rotor speed response results of all the generators are shown in FIGS. 4A and 4B. Here, SFCLs having two different values of R _SFCL (20 ohms and 10 ohms) are compared.

It can be seen from FIG. 4 (a) that the SFCL close to the accident location L3 provides more effective damping performance compared to when the same accident is applied to L1 220 km away from the SFCL. In addition, _SFCL at L3 with R _SFCL of 20 ohms shows better braking performance than without SFCL and SFCL with R _SFCL of 10 ohms. However, in FIG. 4 (b), two SFCLs (20 ohm and 10 ohm) show similar performance for an accident occurring at L1. SFCL is strongly influenced by a change in the appropriate R _SFCL for accidents occurring near the selected optimal position. On the other hand, if the far distance, resulting from the best position is selected accident, it is because the value of R _SFCL relatively less sensitive to power changes _SFCL R influence of change decreases with respect to the SFCL installed in the optimal position.

FIG. 5 is a graph illustrating rotor speed responses of four generators G1, G2, G3, and G4 when the superconducting fault current limiter SFCL is applied to the positions L1 and L3 in the power system of FIG. 2. FIG. 5 (a) illustrates a case where an accident occurs at L1 and FIG. 5 (b) illustrates a case where an accident occurs at L3. R _SFCL of _SFCL is 20 ohm. 5 is a graph obtained by connecting _SFCL with a fixed R _SFCL of 20 ohms to L3 and L1. A 100 ms three phase short circuit fault was applied to the L1 position (Figure 5 (a)) and the L3 position (Figure 5 (b)). The solid and dashed lines in FIG. 5 are responses of _SFCL with R _SFCL of 20 ohms connected to L3 and L1, respectively.

When an accident occurs at L1, the SFCL at L1 near the accident location is greater than the SFCL at L3. It provides slightly better damping for the velocity oscillations of G1 and G2 in AREA 1. However, SFCL at L3 improves damping performance much more effectively than SFCL at L1 for oscillation of G3 and G4 in AREA 2 even if an accident occurs at L1. In the event of an accident at L3, it can be seen from (b) that SFCL at L3 is superior to SFCL at L1 in terms of damping and transient performance for the speed response of all generators.

From the above results of FIGS. 4 and 5, the optimum position L3 was found to be effective for the application of SFCL. In particular, the damping performance of the power system is most effectively improved when an accident occurs near the optimum position, and the short circuit current level of the entire power system can be effectively reduced even if the accident is far from the optimal position.

The present invention is not limited by the above-described embodiment and the accompanying drawings. It is intended that the scope of the invention be defined by the appended claims, and that various forms of substitution, modification, and alteration can be made without departing from the spirit of the invention as set forth in the claims. Will be self-explanatory.

1 is a flowchart illustrating a method of determining an optimum position and an optimum resistance value of a superconducting fault current limiter using PCA and SI according to an embodiment of the present invention.

2 is a diagram illustrating an example of a power system to which the method of FIG. 1 is applied.

FIG. 3 is a graph illustrating changes in PCA sum according to resistance values of SFCL installed in the power system of FIG. 2.

4 is a graph illustrating rotor speed responses of four generators when SFCL installed in the power system of FIG. 2 is connected to L3.

FIG. 5 is a graph showing rotor speed responses of four generators when SFCL installed in the power system of FIG. 2 is applied to L1 and L3.

Claims (4)

Calculate the power value transmitted when the power system is in a steady state at an arbitrary line position and the power value actually transmitted by applying the assumed accident, and accumulate the difference between the two power values for a predetermined time. Obtaining a PCA value defined by Equation 1; Obtaining, for each location to which the superconducting fault current limiter can be applied, a sum of PCA values for assumed accidents of all locations; Calculating a sensitivity change index (SI) of power change according to Equation 2 below by obtaining a change rate of the sum of the PCA values with respect to the resistance change of the superconducting current limiter; And Determining an optimal position of the superconducting fault current limiter to determine a position at which the sensitivity index is minimum; [Equation 1]

[Equation 2]

In Equation 1,

Is a power value transmitted when the steady state at the line position,

Is a power value actually transmitted at the arbitrary line position by applying the assumed accident,

Is the starting point of the predetermined time,

Is the completion time of the predetermined time, and R _SFCL in Equation 2 is the resistance value of the superconducting fault current limiter. The method of claim 1, Calculating a sum of PCA values for assumed accidents of all positions according to resistance values of the superconducting current limiter with respect to the determined optimal position of the superconducting current limiter; And Determining an optimal resistance value of the superconducting current limiter as a resistance value of which the sum of the PCA values is minimum; . The method of claim 1, In the calculating of the PCA value, the power value

And

Is a power value transmitted from a line connecting a region and a region in the power system or a line having a relatively large amount of power transmission. In the method of determining the optimum position and the optimum resistance value of the superconducting fault current limiter installed in the power system, When the sensitivity index (SI) of the power change defined by Equations 1 and 2 below is determined as the optimal position of the superconducting fault current limiter, and the superconducting fault current limiter is installed at the determined optimal position, all positions are assumed. Method for determining the optimum position and the optimum resistance value of the superconducting fault current limiter, characterized in that for determining the resistance value that the sum of the PCA values according to the following equation for the accident is the minimum resistance value, [Equation 1]

[Equation 2]

In Equation 1,

Is a power value transmitted when the steady state at any line position in the power system,

Is a power value actually transmitted at the arbitrary line position by applying the assumed accident,

Is the starting point of the time for calculating the PCA,

Is the completion time of the predetermined time, and R _SFCL in Equation 2 is the resistance value of the superconducting fault current limiter.

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