KR102226677B1 - Apparatus for measuring harmonic impedance of electric power system and method for the same - Google Patents

Abstract

The present application relates to an apparatus and a method for measuring harmonic impedance of a power system, and the method for measuring harmonic impedance of a power system according to an embodiment of the present invention is based on a target point, abbreviated the power system connected to the target point. A reduction system setting step of setting the reduction system by doing so; A measurement result collection step of collecting measurement results by measuring currents and voltages of buses included in the reduction system; And an operation step of calculating an admittance or impedance of the reduced system by using the collected measurement result.

Description

{Apparatus for measuring harmonic impedance of electric power system and method for the same}

The present application relates to a power system harmonic impedance measuring device and method, and more particularly, a harmonic impedance measuring device and a measuring method of a power system capable of measuring the harmonic impedance of the power system at a point where electrical equipment is connected. It is about.

An electric power system is a system in which a power plant, a substation, a transmission and distribution line, and a load are integrated to generate and use electric power.

When an electric device such as a power plant or a load is added to the power system, there is a risk of system disturbance or malfunction of the device due to harmonics. To prevent this, a filter or the like designed based on the harmonic impedance of the power system can be applied. That is, the filter can be used to attenuate the transient characteristics that may occur when an electric device is connected.

However, in order to design a filter or the like, it is necessary to accurately measure the characteristics of the power system, in particular, the harmonic impedance of the power system.

Conventionally, a method of estimating the harmonic impedance of the power system was used by inserting a harmonic current source at a target point where an electric device is installed, and using a voltage measured in response to the input current. The method of inputting a harmonic current source can be relatively accurate when the power system consists of only passive elements, but a variety of active methods such as generators, FACTs (Flexible AC Transmission system), and HVDC (High-Voltage Direct Current) systems are available. Active) In the commercial power system (1) including the facility, there was a problem that accurate measurement was not possible.

The present application is to provide an apparatus and method for measuring harmonic impedance of a power system capable of measuring the harmonic impedance of a power system at a point where electrical equipment is connected.

The present application is intended to provide an apparatus and method for measuring harmonic impedance of a power system that can utilize a condensed system in which the power system is abbreviated.

The present application is to provide an apparatus and a measurement method for measuring harmonic impedance of a power system capable of removing a measurement error using a Kalman filter.

A method for measuring harmonic impedance of a power system according to an embodiment of the present invention includes a reduction system setting step of setting a reduction system by abbreviating the power system connected to the target point based on a target point; A measurement result collection step of collecting measurement results by measuring currents and voltages of buses included in the reduction system; And an operation step of calculating an admittance or impedance of the reduced system by using the collected measurement result.

Here, the reduction system may be set by abbreviating the topology of the power system. In this case, the topology of the reduced system may be similar to the topology of the power system by more than a preset similarity.

Here, the reducing system setting step includes: setting a preliminary reduction system by contracting the power system; Comparing the topology of the preliminary reduction system and the power system, and extracting a preliminary reduction system having a similarity greater than or equal to a preset similarity; And setting, among the extracted preliminary reduction systems, a preliminary reduction system with the smallest number of buses included in the extracted preliminary reduction system as the reduction system.

Here, the reduction system setting step may include setting a preliminary reduction system by setting the number of buses included therein according to an input control signal; Comparing the topology of the preliminary reduction system with the topology of the power system, and setting the preliminary reduction system as the reduction system if the similarity is greater than or equal to a preset similarity; And if it is less than the preset similarity, transmitting the control signal to increase the number of buses included in the preliminary reduction system.

In the calculation step, a Kalman filter may be applied to remove noise included in the measurement result, and the admittance may be calculated.

In this case, the calculating step may include a state equation setting process of setting a state equation of the reduced system using the admittance as a state variable in order to apply to the Kalman filter; A time update process of calculating a predicted value of the state variable for the nth measurement result from the state variable value for the n-1th measurement result using the state equation; A measurement update process of correcting the predicted value with Kalman gain and updating the corrected predicted value to a state variable value for an n-th measurement result; And an admittance calculation process of extracting an admittance corresponding to the measurement result by repeating the time update process and the measurement update process.

Here, the process of setting the state equation

May be set as the state equation. In this case, x(n) is the admittance of the reduced system, Φ is a modeling function for the change characteristic of the admittance, y(n) is the current value of the actual bus, z(n) is the measured current value of the bus, ν (n) may be a measurement error, and c may be a voltage vector at each bus.

Here, the time update process,

을 계산할 수 있다. 이때, P(n)은 상기 상태변수의 오차 공분산이고, P^-(n)는 상기 오차 공분산의 예측값일 수 있다. The predicted value of the state variable using

Can be calculated. At this time, P (n) is the error covariance of the state variables, P ^- (n) may be a predictive value of the error covariance.

Here, the measurement update step

및 P^-(n)을 이용하여,

및 p(n)을 업데이트할 수 있다. Calculate the Kalman gain k(n) using, and the Kalman gain k(n) and the predicted value

And P ^- using a (n),

And p(n) can be updated.

According to an embodiment of the present invention, there may be a computer-readable recording medium in which a program for executing the above-described method is recorded.

An apparatus for measuring harmonic impedance of a power system according to an embodiment of the present invention includes: a reduction system setting unit configured to set a reduction system by abbreviating the power system connected to the target point based on a target point; A measurement result collection unit that collects measurement results of current and voltage of buses included in the reduction system; And an operation unit that calculates an admittance or impedance of the reduced system by using the collected measurement result.

Here, the reduction system setting unit may set the topology of the reduction system to be similar to the topology of the power system by a predetermined degree of similarity or more.

Here, the reduction system setting unit may select a reduction system with the smallest number of buses included in the reduction system when there are a plurality of reduction systems having a degree of similarity equal to or higher than the preset similarity.

Here, the calculator may apply a Kalman filter to remove noise included in the measurement result and calculate the admittance.

Here, the operation unit may include a state equation setting module for setting a state equation of the reduced system using the admittance as a state variable in order to apply to the Kalman filter; A time update module for performing a time update for calculating a predicted value of the state variable for the nth measurement result from the state variable value for the n-1th measurement result using the state equation; A measurement update module for performing a measurement update for correcting the predicted value with Kalman gain and updating the corrected predicted value to a state variable value for an n-th measurement result; And an admittance calculation module for extracting an admittance corresponding to the measurement result by controlling the time update and the measurement update to be repeated.

Here, the state equation setting module

Can be set as the state equation. In this case, x(n) is the admittance of the reduced system, Φ is a modeling function for the change characteristic of the admittance, y(n) is the current value of the actual bus, z(n) is the measured current value of the bus, ν (n) may be a measurement error, and c may be a voltage vector at each bus.

Here, the time update module

을 계산할 수 있다. 이때, P(n)은 상기 상태변수의 오차 공분산이고, P^-(n)는 상기 오차 공분산의 예측값일 수 있다. The predicted value of the state variable using

Can be calculated. At this time, P (n) is the error covariance of the state variables, P ^- (n) may be a predictive value of the error covariance.

Here, the measurement update module

및 P^-(n)을 이용하여,

및 p(n)을 업데이트할 수 있다. Calculate the Kalman gain k(n) using, and the Kalman gain k(n) and the predicted value

And P ^- using a (n),

And p(n) can be updated.

In addition, the solution to the above-described problem does not list all the features of the present invention. Various features of the present invention, as well as advantages and effects thereof, may be understood in more detail with reference to the following specific embodiments.

According to the apparatus and method for measuring a harmonic impedance of a power system according to an embodiment of the present invention, it is possible to measure the harmonic impedance at a target point to which an electrical facility or the like is connected.

According to the apparatus and method for measuring harmonic impedance of a power system according to an embodiment of the present invention, it is possible to efficiently measure the harmonic impedance by using a reduced system in which the power system is abbreviated. In addition, since the calculation is performed by applying the Kalman filter, it is possible to measure the harmonic impedance more accurately.

1 is a schematic diagram showing a system for measuring harmonic impedance of a power system according to an embodiment of the present invention.
2 is a block diagram showing an apparatus for measuring harmonic impedance of a power system according to an embodiment of the present invention.
3 to 5 are schematic diagrams for explaining the setting of a reduced system according to an embodiment of the present invention.
6 is a graph showing a result of measuring a harmonic impedance of a power system according to an embodiment of the present invention.
7 to 8 are flowcharts illustrating a method of measuring harmonic impedance of a power system according to an embodiment of the present invention.

Hereinafter, preferred embodiments will be described in detail with reference to the accompanying drawings so that those of ordinary skill in the art may easily implement the present invention. However, in describing a preferred embodiment of the present invention in detail, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted. In addition, the same reference numerals are used throughout the drawings for parts having similar functions and functions.

In addition, throughout the specification, when a part is said to be'connected' with another part, it is not only'directly connected', but also'indirectly connected' with another element in the middle. Includes. In addition, "including" a certain component means that other components may be further included rather than excluding other components unless otherwise stated. In addition, terms such as "~ unit" and "module" described in the specification mean a unit that processes at least one function or operation, which may be implemented as hardware or software, or as a combination of hardware and software.

1 is a schematic diagram showing a system for measuring harmonic impedance of a power system according to an embodiment of the present invention.

Referring to FIG. 1, a system for measuring a harmonic impedance of a power system according to an embodiment of the present invention may include a power system 1, a measuring device 10, and a harmonic impedance measuring device 100.

Hereinafter, a system for measuring harmonic impedance of a power system according to an embodiment of the present invention will be described with reference to FIG. 1.

The electric power system (1) is a system in which a power plant, a substation, a transmission and distribution line, and a load are integrated to generate and use electric power. The power system 1 may have a topology as shown in FIG. 1, and the topology may include each bus-bar, a line connecting the bus, a power plant, a substation, and a load. have.

When an electric device such as a power plant or a load is added to the power system 1, there is a risk of system disturbance or malfunction of the device due to harmonics occurring in a transient state. To prevent this, a filter or the like designed based on the harmonic impedance of the power system 1 may be applied. That is, the filter can be used to attenuate the transient characteristics that may occur when an electric device is connected. However, in order to design a filter or the like, it is necessary to accurately measure the characteristics of the power system 1 to which the electric device is connected, in particular, the harmonic impedance of the power system 1.

Conventionally, a method of estimating the harmonic impedance of the power system 1 was used by inputting a harmonic current source to a target point (A) where an electric device is installed, and using a voltage measured in response to the applied current. The method of inputting a harmonic current source enables relatively accurate measurements when the power system consists of only passive elements. However, there is a problem that accurate measurement is impossible in the commercial power system 1 including various active facilities such as generators, FACTs (Flexible AC Transmission system), and HVDC (High-Voltage Direct Current) systems.

On the other hand, it is also possible to analyze the influence of harmonics that may occur in the power system 1 when the electrical equipment is connected by modeling the entire power system 1 and then simulating it. In this case, since the characteristics of the entire power system 1 can be reflected by modeling, the influence of harmonics that may occur when an electric device or the like is connected to the target point A can be accurately confirmed. However, modeling in consideration of the overall characteristics of the power system 1 is a very difficult problem to be applied in practice when considering issues such as the amount of data required for modeling, time required, cost, and security.

The harmonic impedance measuring apparatus 100 may reduce the power system 1 for efficient measurement, and estimate the harmonic impedance of the entire power system 1 by analyzing the reduced system.

Specifically, as shown in FIG. 3, the harmonic impedance measuring apparatus 100 can be set from the power system 1 to a reduced system of various ranges. That is, as shown in Fig. 3(a), the entire power system 1 can be reduced to one bus, and as shown in Figs. 3(b) to 3(g), one bus bar connected to the corresponding bus bar is You can set up a reduction system in a way that increments the steps of. Here, finally, it can be expanded to the entire power system 1 as shown in Fig. 3(g).

4 and 5 are graphs showing the amplitude and phase of the harmonic impedance corresponding to each of the abbreviated abbreviated systems. That is, the magnitude of the harmonic impedance corresponding to the reduced system of Fig. 3(a) is shown in Fig. 4(a), the phase is shown in Fig. 5(a), and the magnitude of the harmonic impedance corresponding to the reduced system of Fig. 3(b) The and phases are shown in Figs. 4(b) and 5(b), respectively. The magnitude and phase of the harmonic impedance are displayed in the same way for the rest of the reduced systems.

Referring to FIGS. 3 to 5, it can be seen that the reduced system of FIGS. 3(e) and 3(f) exhibits almost the same results as the case of calculating the harmonic impedance for the entire power system 1. In other words, the more the reduction is made, the more the harmonic impedance of the reduction system may be different from the harmonic impedance of the actual power system (1). On the other hand, as the topology of the buses included in the reduction system is similar to the entire power system (1), the harmonic It can be seen that the impedance becomes similar. Therefore, it is possible to obtain the harmonic impedance by using a reduced system instead of the entire power system (1).

In addition, the harmonic impedance measurement apparatus 100 may receive a measurement result of current and voltage of each bus line included in the reduction system from the measurement equipment 10 in order to perform an analysis on the reduction system. The harmonic impedance measuring apparatus 100 may use this to extract the harmonic impedance in the reduction system.

Here, the measurement device 10 may perform measurement at each measurement point set in the power system 1, and may provide the measurement result to the harmonic impedance measurement apparatus 100 through wired and wireless communication. However, since the current and voltage measured by the measurement equipment 1 may include measurement errors, it is necessary to correct the errors. Accordingly, the harmonic impedance measuring apparatus 100 may correct an error included in the measurement result by applying a Kalman filter and obtain an accurate harmonic impedance.

That is, the harmonic impedance measuring apparatus 100 according to an embodiment of the present invention can accurately and efficiently measure the harmonic impedance of the power system 1 as compared with conventional methods.

Hereinafter, a specific operation of the harmonic impedance measuring apparatus 100 according to an embodiment of the present invention will be described.

2 is a block diagram showing an apparatus for measuring harmonic impedance of a power system according to an embodiment of the present invention.

Referring to FIG. 2, an apparatus for measuring harmonic impedance of a power system according to an embodiment of the present invention may include a reduced system setting unit 110, a measurement result collection unit 120, and an operation unit 130.

The reduced system setting unit 110 may reduce the power system 1 connected to the target point A based on the target point A and set it as a reduced system. Here, the target point A may be a point where the electric device is connected to the power system.

The reduction system is set by abbreviating the entire power system (1). When setting the reduction system, it is important to what extent the power system (1) is reduced.

Harmonic impedance may have less influence on a bus that is far from the target point (A) due to its characteristics, and may be greatly affected by a bus that is close to the target point (A). Therefore, within a certain range from the target point (A), if the topology of the entire power system 1 and the reduced system are the same, the harmonic impedance measured in each case becomes very similar.

That is, since the harmonic impedance is affected by the topology, the reduction system setting unit 110 may select a reduction system that is similar to the topology of the entire power system at least with a predetermined similarity or higher. For example, among a plurality of reduction systems shown in FIG. 3, a reduction system similar to the topology of the entire power system and a predetermined similarity or higher may be selected and utilized to measure the harmonic impedance. In this case, the abbreviated system of FIGS. 3(a) to 3(d) may be excluded because it is different from the topology of the actual power system 1, and FIGS. 3(e) and 3(f) show a preset similarity. It can be determined that the above is similar.

On the other hand, when there are a plurality of reduction systems having a predetermined similarity or higher, the reduction system setting unit 110 may select a reduction system with the smallest number of buses included in the reduction system. As the number of busbars increases, the number of factors to be measured and calculated increases. In order to minimize this, a reduction system with the smallest busbars can be selected. Here, there may be various methods of calculating the degree of similarity of the topology, and the present invention is not limited by the method of calculating the degree of similarity. Since the similarity calculation method is known, a detailed description of the calculation method is omitted here.

Specifically, the reduced system setting unit 110 may set a plurality of preliminary reduction systems by abbreviating the power system, and may compare the topology of the plurality of preliminary reduction systems with the topology of the power system 1. Thereafter, a preliminary reduction system having a similarity greater than or equal to a preset similarity to the topology of the power system (1) can be extracted, and among the extracted preliminary reduction systems, the preliminary reduction system with the smallest number of buses included inside is set as the reduction system. I can.

In addition, depending on the embodiment, it is possible to set a preliminary reduction system while increasing the number of buses included in the reduction system. That is, a preliminary reduction system having the number of buses set according to the control signal is set, and compared with the topology of the power system, it is possible to check whether or not the similarity is more than the preset similarity. Here, when the similarity is similar to the preset similarity or more, the reduced system may be set. However, when the similarity is less than the preset similarity, a control signal is transmitted to increase the number of buses included in the reduction system to generate a preliminary reduction system again.

In addition, depending on the embodiment, on the basis of the bus bar including the target point (A), the busbars directly connected to the first stage, the busbars directly connected to the stage 1 busbars, and the busbars directly connected to the second stage and the second stage busbars It can be set in three stages, etc. In this case, it is also possible to set the reduction system in a manner of selecting a reduction system to which buses of at least n steps or more are connected.

The measurement result collection unit 120 may collect measurement results of currents and voltages of buses included in the reduced system. As shown in FIG. 1, the harmonic impedance measurement apparatus 100 may receive a measurement result from the measurement equipment 10, and the measurement equipment 10 may measure the current and voltage for each bus. Here, the measurement results may be transmitted between the measurement equipment 10 and the measurement result collection unit 120 through wired or wireless communication.

The calculation unit 130 may calculate the admittance or impedance of the reduced system by using the collected measurement results. Since the current and voltage measured by the measurement equipment 10 may include measurement errors, the calculation unit 130 may remove noise included in the measurement result by applying a Kalman filter. Thereafter, the admittance of the reduced system corresponding to the harmonic impedance can be calculated.

Specifically, the calculation unit 130 may include a state equation setting module 131, a time update module 132, a measurement update module 133, an admittance calculation module 134, and the like.

The state equation setting module 131 may set a state equation of a reduced system using admittance as a state variable in order to apply to the Kalman filter. Specifically, the state equation can be set as follows.

Here, x(n) is a state variable and is the admittance of the reduced system, Φ is a modeling function for the change characteristics of admittance, Г is the process noise coefficient, and w(n) is the process noise. It is a process noise vector. y(n) is the true value, z(n) is the measured value, ν(n) is the measurement error, c is the bais function, and n is the measurement equipment ( It means the nth sample of the measurement result transmitted in 10).

Φ can be replaced with a unit matrix in simple estimation, and in the case of a generator with strong nonlinearity, an equation corresponding to the generator can be reflected. The state variable x(n) may be an admittance of the reduced system, and in this case, the basis function c may be the voltage of the buses measured by the measurement equipment 10. In this case, y(n) may be a true value for the current of the buses. Depending on the embodiment, it is also possible to set the basis function c as a function c(t) with respect to time. That is, when the connected electric device is a nonlinear device such as a generator, since the basis function c is updated every moment, it can be calculated by setting c(t).

On the other hand, the process noise vector w(n) is an error occurring in the prediction process to the next state, and is very small compared to the measurement error and can be ignored. In this case, the state equation can be summarized as follows.

The time update module 132 may perform a time update for calculating a predicted value of a state variable for an n-th measurement result using a state equation. In the time update in the Kalman filter, a predicted value of the state variable for the nth measurement result can be calculated from the state variable for the n-1th measurement result. In other words,

을 계산할 수 있다. 또한, 상태변수의 오차 공분산(error covariance)인 P(n)에 대하여도 예측값 P^-(n)을 계산할 수 있다. 여기서 윗첨자 T는 전치행렬(Transposed matrix)을 의미할 수 있다. 한편, Q는 공정 노이즈의 공분산 행렬(process noise covariance matrix)이나, 여기서 공정오차와 측정오차는 상호 독립적이므로 0으로 둘 수 있다. The predicted value of the state variable using

Can be calculated. Further, FIG predicted value P with respect to the P (n) error covariance (error covariance) of the state ^variables it is possible to calculate the (n). Here, the superscript T may mean a transposed matrix. Meanwhile, Q is a process noise covariance matrix, but since the process error and the measurement error are independent of each other, it can be set to zero.

Accordingly, the time update module 132 may calculate the state variable and the predicted value of the error covariance using the following equation.

The measurement update module 133 may perform a measurement update in which the predicted value is corrected with Kalman gain, and the corrected predicted value is updated as a state variable value for the n-th measurement result. In other words,

및 P^-(n)을 이용하여,

및 p(n)을 업데이트할 수 있다. 여기서, r은 측정오차 ν(n)의 공분산에 해당한다. 즉, 측정 업데이트 모듈(133)은 예측값

에 칼만 게인 k(n)과 측정오차를 적용하는 방식으로,

으로 업데이트할 수 있으며, 이를 통하여, 정확하게

을 계산할 수 있다. 여기서,

을 이용하면

으로 나타낼 수 있다.Kalman gain k(n) can be calculated using Kalman gain k(n) and predicted value

And P ^- using a (n),

And p(n) can be updated. Here, r corresponds to the covariance of the measurement error ν(n). That is, the measurement update module 133 is a predicted value

By applying Kalman gain k(n) and measurement error to

Can be updated to, and through this, accurately

Can be calculated. here,

If you use

It can be represented by

는 축약시스템의 어드미턴스에 대응하므로, 이를 활용하여 전기기기가 연계되는 대상지점의 축약 계통을 구성할 수 있다. 이때, 축약시스템의 어드미턴스 매트릭스는, 전기기기가 대상지점(A)에서 바라보는 전체 전력계통의 하모닉 임피던스를 반영하게 된다. 따라서, 이를 통하여 전력계통의 하모닉 임피던스를 계산하는 것이 가능하다. The admittance calculation module 134 may control to repeat the time update and the measurement update, through which the admittance corresponding to the measurement result may be extracted. That is, the state variable

Since is corresponding to the admittance of the reduced system, the reduced system of the target point to which the electric device is connected can be constructed by using this. At this time, the admittance matrix of the reduced system reflects the harmonic impedance of the entire power system viewed by the electric device from the target point (A). Therefore, it is possible to calculate the harmonic impedance of the power system through this.

On the other hand, since the admittance extracted by the admittance calculation module 134 is presented in a matrix form, it can be applied to the power current calculation to check its accuracy. That is, referring to Fig. 6, Fig. 6(a) is an actual admittance matrix of the reduced system, Fig. 6(b) is an admittance matrix calculated by the admittance calculation module 134, and Fig. 6(c) shows the measurement error. It is a graph showing. Referring to FIG. 6, it can be seen that the admittance matrix calculated by the admittance calculation module 134 has almost no error with the actual admittance matrix.

7 and 8 are flowcharts illustrating a method of estimating harmonic impedance of a power system according to an embodiment of the present invention.

7 and 8, the method for estimating the harmonic impedance of the power system according to an embodiment of the present invention includes a reduction system setting step (S10), a measurement result collection step (S20), and an operation step (S30). I can.

Hereinafter, a method of estimating a harmonic impedance using a harmonic impedance estimating apparatus according to an embodiment of the present invention will be described with reference to FIGS. 7 and 8.

In the reduction system setting step (S10), the reduction system may be set by abbreviating the power system connected to the target point based on the target point. Here, the target point may be a point at which the electric device is connected to the power system.

The contraction system is set by abbreviating the entire power system. When setting the contraction system, it is important to what extent the power system is contracted.

Since the harmonic impedance is affected by the topology, in order to obtain an accurate result, it is possible to select a reduced system that is similar to the topology of the entire power system at least with a predetermined similarity.

On the other hand, when there are a plurality of reduction systems having a predetermined similarity or higher, the reduction system with the smallest number of buses included in the reduction system may be selected. That is, as the number of buses increases, the number of factors to be measured and calculated later increases. In order to minimize this, a reduction system having the smallest busbars can be selected.

The reduction system setting step (S10) may include a step of setting a plurality of preliminary reduction systems by abbreviating the power system, and a preliminary reduction system having a similarity greater than or equal to a preset similarity by comparing the topology of the preliminary reduction system and the power system. The step of extracting can be performed. Thereafter, among the extracted preliminary reduction systems, the reduction system may be set through the step of setting a preliminary reduction system with the smallest number of buses included therein as the reduction system.

In addition, depending on the embodiment, it may include the step of generating a preliminary reduction system by setting the number of buses included in the reduction system according to the input control signal. Thereafter, the topology of the preliminary reduction system and the topology of the power system are compared, and if the similarity is greater than or equal to a preset similarity, the step of setting the preliminary reduction system as a reduction system may be performed. However, if the degree of similarity is less than a preset similarity, the step of generating a preliminary reduction system again to check the similarity may be performed by increasing the number of buses included in the reduction system by transmitting a control signal.

In addition, depending on the embodiment, on the basis of the bus bar including the target point, the busbar directly connected to the first stage, the busbar directly connected to the stage 1 busbar in the second stage, the busbar directly connected to the second stage busbar in the third stage, etc. It is also possible to set the reduced system in a manner of selecting a reduced system having a topology that is connected to at least n steps or more.

In the measurement result collection step S20, a measurement result obtained by measuring the current and voltage of buses included in the reduction system may be collected. The harmonic impedance measuring device can receive the measurement result from the measuring equipment, and the measuring equipment can measure the current and voltage for each bus. At this time, the measurement equipment may transmit the measurement result through wired or wireless communication.

In the calculation step S30, the admittance or impedance of the reduced system may be calculated using the collected measurement result. In the calculation step S30, noise included in the measurement result may be removed by applying a Kalman filter, and then the admittance of the reduced system corresponding to the harmonic impedance may be calculated.

Specifically, the calculation step (S30) may include a state equation setting process (S31), a time update process (S32), a measurement update process (S33), and an admittance calculation process (S34), as shown in FIG. have.

In the state equation setting process (S31), in order to apply the Kalman filter, the state equation of the reduced system using admittance as a state variable may be set. Specifically, the state equation can be set as follows.

Here, x(n) is a state variable, admittance of the reduced system, Φ is a modeling function for the change characteristics of admittance, y(n) is a true value, and z(n) is a measured value ( measured value), ν(n) is the measurement error, c is the bais function, and n is the nth sample of the measurement result transmitted from the measurement device.

Φ can be replaced with a unit matrix in simple estimation, and in the case of a generator with strong nonlinearity, an equation corresponding to the generator can be reflected. The state variable x(n) may be the admittance of the reduced system, and in this case, the basis function c may be the voltage of the measured busbars. In this case, y(n) may be the true value of the current of the bus. Depending on the embodiment, it is also possible to set the basis function c as a function c(t) with respect to time. That is, when the connected electric device is a nonlinear device such as a generator, since the basis function c is updated every moment, it can be calculated by setting c(t).

In the time update process S32, a time update for calculating a predicted value of a state variable for the n-th measurement result may be performed using a state equation. In the time update in the Kalman filter, the predicted value of the state variable for the nth measurement result can be calculated from the value of the state variable for the n-1th measurement result. In other words,

을 계산할 수 있다. 또한, 상태변수의 오차 공분산(error covariance)인 P(n)에 대하여도 예측값 P^-(n)을 계산할 수 있다. The predicted value of the state variable using

Can be calculated. Further, FIG predicted value P with respect to the P (n) error covariance (error covariance) of the state ^variables it is possible to calculate the (n).

In the measurement update process S33, a measurement update may be performed in which the predicted value is corrected with Kalman gain, and the corrected predicted value is updated as a state variable value for the n-th measurement result. In other words,

및 P^-(n)을 이용하여,

및 p(n)을 업데이트할 수 있다. 여기서, r은 측정오차 ν(n)의 공분산에 해당한다. 측정 업데이트 과정(S33)에서는 예측값

에 칼만 게인 k(n)과 측정오차를 적용하는 방식으로

으로 업데이트할 수 있으며, 이를 통하여

을 정확하게 계산할 수 있다.Kalman gain k(n) can be calculated using Kalman gain k(n) and predicted value

And P ^- using a (n),

And p(n) can be updated. Here, r corresponds to the covariance of the measurement error ν(n). In the measurement update process (S33), the predicted value

By applying Kalman gain k(n) and measurement error to

Can be updated with

Can be accurately calculated.

는 축약시스템의 어드미턴스에 대응하므로, 이를 활용하여 전기기기가 연계되는 대상지점의 축약 계통을 구성할 수 있다. 이때, 축약시스템의 어드미턴스 매트릭스는, 전기기기가 대상지점(A)에서 바라보는 전체 전력계통의 하모닉 임피던스를 반영하게 된다. 따라서, 이를 통하여 전력계통의 하모닉 임피던스를 계산하는 것이 가능하다. In the admittance calculation process S34, the time update process S32 and the measurement update process S33 may be repeated to extract an admittance corresponding to the measurement result. That is, the state variable

Since is corresponding to the admittance of the reduced system, the reduced system of the target point to which the electric device is connected can be constructed by using this. At this time, the admittance matrix of the reduced system reflects the harmonic impedance of the entire power system viewed by the electric device from the target point (A). Therefore, it is possible to calculate the harmonic impedance of the power system through this.

The present invention described above can be implemented as a computer-readable code on a medium on which a program is recorded. The computer-readable medium may be one that continuously stores a program executable by a computer, or temporarily stores a program for execution or download. In addition, the medium may be a variety of recording means or storage means in a form in which a single piece of hardware or several pieces of hardware are combined, but is not limited to a medium directly connected to a computer system, but may be distributed on a network. Examples of media include magnetic media such as hard disks, floppy disks and magnetic tapes, optical recording media such as CD-ROMs and DVDs, magneto-optical media such as floptical disks, And ROM, RAM, flash memory, and the like may be configured to store program instructions. In addition, examples of other media include an app store that distributes applications, a site that supplies or distributes various software, and a recording medium or a storage medium managed by a server. Therefore, the detailed description above should not be construed as restrictive in all respects and should be considered as illustrative. The scope of the present invention should be determined by reasonable interpretation of the appended claims, and all changes within the equivalent scope of the present invention are included in the scope of the present invention.

The present invention is not limited by the above-described embodiments and the accompanying drawings. It will be apparent to those of ordinary skill in the art to which the present invention pertains, that components according to the present invention can be substituted, modified, and changed within the scope of the technical spirit of the present invention.

1: power system 10: measuring equipment
100: harmonic impedance measuring device 110: reduced system setting unit
120: measurement result collection unit 130: operation unit
131: state equation setting module 132: time update module
133: measurement update module 134: admittance calculation module
S10: Reduction system setting step S20: Measurement result collection step
S30: operation step S31: state equation setting process
S32: Type update process S33: Measurement update process
S34: Admittance calculation process

Claims (18)

A reduction system setting step of setting a reduction system by abbreviating the power system connected to the target point based on the target point;
A measurement result collection step of collecting measurement results by measuring currents and voltages of buses included in the reduction system; And
A method for measuring harmonic impedance of a power system comprising an operation step of calculating an admittance or impedance of the reduced system by using the collected measurement result.
The method of claim 1, wherein the reduction system
A method for measuring a harmonic impedance of a power system, wherein the topology of the power system is abbreviated and set, wherein the topology of the reduced system is similar to the topology of the power system by a predetermined degree of similarity or more.
The method of claim 1, wherein the reduction system setting step
Setting a preliminary contraction system by contracting the power system;
Comparing the topology of the preliminary reduction system and the power system, and extracting a preliminary reduction system having a similarity greater than or equal to a preset similarity; And
And setting, among the extracted preliminary reduction systems, a preliminary reduction system with the smallest number of buses included therein as the reduction system.
The method of claim 1, wherein the reduction system setting step
Setting a preliminary reduction system by setting the number of buses included therein according to an input control signal;
Comparing the topology of the preliminary reduction system with the topology of the power system, and setting the preliminary reduction system as the reduction system if the similarity is greater than or equal to a preset similarity; And
And if it is less than the preset similarity, transmitting the control signal to increase the number of buses included in the preliminary reduction system.
The method of claim 1, wherein the calculating step
A method for measuring harmonic impedance of a power system, comprising applying a Kalman filter to remove noise included in the measurement result and calculating the admittance.
The method of claim 5, wherein the calculating step
A state equation setting step of setting a state equation of the reduced system using the admittance as a state variable to apply to the Kalman filter;
A time update process of calculating a predicted value of the state variable for the nth measurement result from the state variable value for the n-1th measurement result using the state equation;
A measurement update process of correcting the predicted value with Kalman gain and updating the corrected predicted value to a state variable value for an n-th measurement result; And
And an admittance calculation process of extracting an admittance corresponding to the measurement result by repeating the time update process and the measurement update process.
The method of claim 6, wherein the step of setting the state equation

Is set as the state equation, where x(n) is the admittance of the reduced system, Φ is a modeling function for the change characteristic of the admittance, y(n) is the current value of the actual bus, and z(n) is measured. A method for measuring harmonic impedance of a power system, characterized in that the current value of the bus bar, ν(n) is a measurement error, and c is a voltage vector at each bus bar.
The method of claim 6, wherein the time update process

The predicted value of the state variable using

The calculation and, P (n) is the error covariance of the state variables, P ^- (n) is the harmonic impedance measurement method of a power system predicted value of the error covariance.
The method of claim 6, wherein the measurement update process

Calculate the Kalman gain k(n) using, and the Kalman gain k(n) and the predicted value

And P ^- using a (n),

And a method for measuring harmonic impedance of a power system to update p(n).
A computer-readable recording medium on which a program for executing the method of any one of claims 1 to 9 is recorded.
A reduction system setting unit for setting a reduction system by abbreviating the power system connected to the target point based on the target point;
A measurement result collection unit that collects measurement results of current and voltage of buses included in the reduction system; And
Harmonic impedance measuring apparatus of a power system including an operation unit for calculating an admittance or impedance of the reduced system by using the collected measurement result.
The method of claim 11, wherein the reduction system setting unit
The harmonic impedance measuring apparatus of a power system, characterized in that the topology of the reduced system is set to be similar to the topology of the power system by a predetermined degree of similarity or more.
The method of claim 11, wherein the reduction system setting unit
When there are a plurality of reduction systems having a predetermined similarity or higher, the harmonic impedance measuring apparatus of a power system, characterized in that, selects a reduction system with the smallest number of buses included in the reduction system.
The method of claim 11, wherein the operation unit
Applying a Kalman filter to remove noise included in the measurement result, and calculating the admittance.
The method of claim 14, wherein the operation unit
A state equation setting module for setting a state equation of the reduced system using the admittance as a state variable to apply to the Kalman filter;
A time update module for performing a time update for calculating a predicted value of the state variable for the nth measurement result from the state variable value for the n-1th measurement result using the state equation;
A measurement update module for performing a measurement update for correcting the predicted value with Kalman gain and updating the corrected predicted value to a state variable value for an n-th measurement result; And
And an admittance calculation module for extracting an admittance corresponding to the measurement result by controlling the time update and the measurement update to be repeated.
The method of claim 15, wherein the state equation setting module

Is set as the state equation, where x(n) is the admittance of the reduced system, Φ is a modeling function for the change characteristic of the admittance, y(n) is the current value of the actual bus, and z(n) is measured. Harmonic impedance measurement device of the power system, characterized in that the current value of the bus bar, ν(n) is the measurement error, and c is the voltage vector at each bus bar.
The method of claim 15, wherein the time update module

The predicted value of the state variable using

The calculation and, P (n) is the error covariance, and, P of the state variable ^- (n) is the harmonic impedance measuring device of the electric power system predicted value of the error covariance.
The method of claim 15, wherein the measurement update module

Calculate the Kalman gain k(n) using, and the Kalman gain k(n) and the predicted value

And P ^- using a (n),

And an apparatus for measuring harmonic impedance of the power system to update p(n).

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