KR101988670B1 - Device for state estimation of power distribution system - Google Patents

Abstract

The present invention relates to a state estimation apparatus of a power distribution system capable of clearly estimating an interval load by reducing a system and eliminating error data.
For example, a distribution system state estimating apparatus for estimating a state of a distribution system by acquiring a measurement value of a phase difference between a voltage and a current of a node adjacent to the switch, a phase difference between the voltage and the current from the switch, And a state estimation unit for estimating an interval load of the power distribution system.

Description

[0001] The present invention relates to a device for estimating the state of a power distribution system,

The present invention relates to an apparatus for estimating a state of a distribution system.

It is very important to estimate the state of the distribution system by calculating the state variables, voltage and phase, and finally estimating the section load of the distribution system precisely.

Algae calculations in the distribution grid are a basic solution for identifying vulnerable locations. It is very important to accurately estimate the load of the section. Therefore, accurate state estimation is important to estimate the accurate section load. Since the distribution system reconstruction, which is a typical distribution system planning solution, is based on the load of each D / L (distribution line), the load is equalized and the loss is calculated based on the algebraic calculation. It is a very important factor. Also, it is very important to grasp the voltage violation and line overload as constraints. In addition, when a fault occurs in the power distribution system, the failure is prevented by the protection device, the fault section is isolated by the automatic switch, and the restoration of the power failure section is performed sequentially. In order to recover the blackout period, it is necessary to know the load of the blackout period and the load of the neighboring lines that can be switched, thereby determining whether or not the blackout period is recovered. A new line and automation switchgear is considered for cases where restoration is not possible, and thus an incorrect estimate of the section load results in an economic loss.

Korean Unexamined Patent Application Publication No. 10-2006-0038527 (May 4, 2006)

The present invention provides a state estimation apparatus of a power distribution system capable of clearly estimating an interval load by abating a system and eliminating error data.

A distribution system state estimating apparatus for estimating a state of a distribution system by acquiring, from the switch, a measurement of a magnitude of a voltage and a current of a node adjacent to the switch according to the present invention and a phase difference between the voltage and the current, And a state estimation unit for estimating an interval load of the power distribution system.

In addition, the state estimating unit may not shorten a node to which a generator, a switched virtual connection (SVC), a transformer, and a shunt facility are connected.

In addition, the state estimating unit may reduce the manual switch and the automatic switch.

In addition, the state estimating unit may reduce the quality of the measured value in the automatic switch and the result of the current consistency check to be " Bad ".

In addition, the state estimating unit may not abbreviate a branch point node between adjacent automation switches.

In addition, the state estimation unit may not shorten the line ends of the power distribution system.

The state estimating unit may further include an interval load calculating unit for calculating the interval load pseudo measurement value by checking the current consistency of the measured value.

The section load calculation unit searches for an automatic switch and a line connected to a distributed power source and determines whether or not the line is pressurized by using information on the open and closed states of the node and the automation switch. A group can be formed using only the breaker formed at the lead-out end of the power distribution line and the automatic switch connected to the distributed power source.

The section load calculation unit searches for an automatic switch and a line connected to the distributed power source, and determines whether the line is pressurized by using information on the open / close states of the node and the automation switch. If the current state of the state estimation unit is not the initial state Automated switches with the same quality of measurement can be grouped together.

Also, the interval load calculation unit may calculate the load of the individual interval by calculating the total amount of load in the interval after performing the current consistency test for each group.

Also, the interval load calculation unit may perform a current consistency check for each group, and if one automatic switch may violate the current consistency check, the group can be reconfigured.

The state estimating unit may further include an error processing unit for detecting error data of the measured value using the weighted residual.

Also, the error processing unit may calculate the weighted residual by calculating the measurement error by calculating the covariance matrix of each measurement value through the state estimation calculation.

In addition, the error processing unit may calculate a maximum weighted residual from the weighted residuals, classify the weighted residuals as error data, and delete the measured values if the maximum weighted residual is greater than a set value.

Also, the error processing unit may calculate the standard deviation of the weighted residuals, classify the standard deviation as error data, and delete the measured value if the standard deviation is equal to or greater than the set value.

The state estimator may calculate the section load from the measured values, shorten the system topology, generate connection information between the newly generated short bus and each facility, generate information of the system topology, and then use the system topology and topology information The state estimator constructs a Jacobian matrix by calculating an objective function that is a sum of squares of deviations between a measured value and an estimated value for the inviscid response analysis and constructs a Jacobian matrix. And calculates the weighted residual if the amount of change is smaller than the convergence limit. If the error data is not detected, the state variable updating and outputting can be performed.

The apparatus for estimating the state of the power distribution system according to an embodiment of the present invention can improve the error data detection capability and time by increasing the spectral efficiency by reducing the system based on the measurement data and varying the error data processing reference by the iterative operation .

1 is a block diagram showing a state estimation apparatus of a power distribution system according to an embodiment of the present invention.
2 is a block diagram showing a state estimation unit of the state estimation apparatus of the power distribution system.
3 is a flowchart illustrating a method of estimating a state of a power distribution system state estimating apparatus according to an embodiment of the present invention.
4 is a flowchart showing a processing method of the section load calculation unit.
5A to 5D are schematic diagrams of a power distribution system for explaining a reduction method of the power reduction unit.
6 is a flowchart showing a method of detecting error data in the error processing unit.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings, so that those skilled in the art can easily carry out the present invention.

1 is a block diagram showing a state estimation apparatus of a power distribution system according to an embodiment of the present invention. 2 is a block diagram showing a state estimation unit of the state estimation apparatus of the power distribution system.

Referring to FIG. 1, an apparatus 100 for estimating a state of a distribution system according to an embodiment of the present invention includes a site data acquisition device 110, a site data processing device 120, and a host 130.

The state estimation apparatus 100 of the power distribution system performs measurement by a field data acquisition apparatus 110, for example, a feeder remote terminal unit (FRTU), and collects system data, 120 to the host 130, and the transmitted data is processed by the state estimator 140 and stored in the database 150. The field data acquisition device 110 is provided in a transformer SVR or an automation switch formed in a power distribution system and is provided with data such as the magnitude of voltage and current and the phase difference between voltage and current of the node to which the field data acquisition device 110 is connected . The state estimator 140 processes the bad data by reducing the power distribution system and calculating the state of the power distribution system. 2, the state estimator 140 includes a section load calculator 141, a system summarizer 142, a system topology information generator 143, a state variable calculator 144, and an error processor 145 ).

3 is a flowchart illustrating a method of estimating a state of a power distribution system state estimating apparatus according to an embodiment of the present invention.

Referring to FIG. 3, a method of estimating a state of a power distribution system state estimating apparatus according to an embodiment of the present invention will be described below.

First, the section load calculation section 141 checks the consistency of the data of the current automatic switch (hereinafter, referred to as a measurement value) acquired by the site data acquisition apparatus 110 to calculate a section load pseudo measurment (S1). The processing method of the section load calculation unit 141 will be described in detail below.

In addition, the system descrambler 142 cancels the system topology based on a measurement value required for state estimation (S2). Here, the system reduction unit 142 reduces the system topology by applying the consistency check result inspected by the interval load calculation unit 141.

Next, the system topology information generating unit 143 generates connection information between the newly created short bus and each facility based on the reduced information generated by the system reducing unit 142 (S3). For example, the system topology information generator 143 may generate connection information between the abbreviated bus and the line, node, generator, or load.

In addition, the system topology information generator 143 generates the information of the transformer tap, the line current, the injection power load, and the power generation amount according to the reduction system (S4). The systematic topology information generator 143 generates the weighting matrix S5 using the standard deviation of the measured values, and sums and compares the measured values and the systematic information (S6). From hereafter, each independent system is performed.

Next, the state variable calculator 144 forms a Ybus matrix, which is an admittance characteristic matrix, using the system impedance and the topology information (S7), and checks whether or not the state estimation solution of the system can be obtained using the measured values Is performed (S8).

First, in order to perform the spectral lateral analysis, the state variable calculator 144 calculates an objective function that is a sum of squares of deviations between measured values and estimated values (S9). The objective function J (x) is calculated by the following equation (1).

[Equation 1]

Here, z is a measurement value, h (x) is an estimated value by the state estimation measurement function, and W is a weight value for each measurement value. The state estimation is to find the value of the state variable x that minimizes the value of this objective function. The state estimation measurement function is a mathematical expression expressing measurement values in terms of voltage and phase, and the state estimation measurement function h (x) for each measurement value is solved.

&Quot; (2) "

Equation 2 represents the state estimation measurement function for the valid / invalid injection power on bus i. Here, G _ij is the effective component of the admittance matrix, B _ij is the ineffective component of the admittance matrix, and N is the number of buses connected to the bus i.

The state estimation measurement function for the line bird power on the bus i, j is given by the following equation (3).

&Quot; (3) "

Where g _ij is the effective line admittance between buses i and j, b _ij is the ineffective line admittance between buses i and j, g _si is the effective parallel admittance of the line and b _si is the ineffective line parallel admittance. Also, g _si and b _si are negligible in the case of distribution lines.

The state estimation measurement function for line currents on buses i and j is: < EMI ID = 3.0 >

&Quot; (4) "

If the line parallel admittance is neglected in Equation (4), the state estimation measurement function for the line current is expressed by Equation (5).

&Quot; (5) "

Next, the state variable calculator 144 constructs a Jacobian matrix (S10). The Jacobian matrix may be generated using the state estimation measurement function. The calculation formula of the Jacobian matrix for each state estimation measurement function is shown in Equation (6).

&Quot; (6) "

In addition, the calculation formula of the Jacobian matrix with respect to the invalid injection power is expressed by Equation (7).

&Quot; (7) "

In addition, the calculation formula of the Jacobian matrix with respect to the effective bird power is expressed by the following equation (8).

&Quot; (8) "

Also, the calculation formula of the Jacobian matrix with respect to the invalid bird power is expressed by the following equation (9).

&Quot; (9) "

Further, the calculation formula of the Jacobian matrix with respect to the voltage is expressed by the following equation (10).

&Quot; (10) "

Further, the calculation formula of the Jacobian matrix with respect to the current is expressed by the following equation (11).

&Quot; (11) "

Next, the state variable calculator 144 constructs a gain matrix using the Jacobian matrix (S11). Then, the state variable calculation unit 144 calculates a state variable change amount and checks whether the change amount has reached the convergence limit (S12 to S13). If the state variable change amount is smaller than the convergence limit, the state variable calculation unit 144 calculates the weighted residual (S14), detects the error data (S15), and updates and outputs the state variable when there is no error data (S16) If there is error data, the error data is removed (S17) and the objective function is recalculated (S9).

4 is a flowchart showing a processing method of the section load calculation unit.

Referring to FIG. 4, a processing method of the section load calculation unit will be described below.

If the distributed power source exists, the section load calculation unit 141 searches for an automated switch and a line connected to the distributed power source (S101). Then, the section load calculation unit 141 determines whether the line is pressurized using the open / close state information of the node and the automated switch (S102). This is to avoid calculating the section load of unpressed lines. Here, whether or not the line is pressurized is to determine whether or not electricity is conducted to the line.

Next, the section load calculation unit 141 determines the current execution state of the state estimation unit 140 (S103). That is, the section load calculating section 141 determines whether the state estimating section 140 is in the initial state estimation (initial state). For example, when the current state of the state estimator 140 is in an initial state, the section load calculator 141 calculates the section load calculator 141 based on a circuit breaker (CB) formed at a lead-out terminal of a high-voltage distribution line (DL) An automated switch is formed by using an automated switch connected to the distributed power supply (S104). The section load calculation unit 141 calculates the total amount of load of the automatic switch group using a breaker formed at the lead-out end of the high voltage distribution line and an automatic switch connected to the distributed power supply (S105). Here, the method of calculating the total amount of load of the automation switch group uses the deviation of the inflow amount and the outflow amount. In the case of the voltage measurement value, as mentioned above, it is assumed that bad data exists in almost all measured values, . Then, the section load calculation section 141 finally distributes the individual section load amounts of the power distribution system (S106).

For example, if the current state of the state estimator 140 is not the initial state, the section load calculator 141 calculates the interval load by using the measurement quality (QC) of the current automation switch, (S107). Here, the measurement quality refers to the measurement quality of voltage, current, and phase, and the automatic switches participating in the grouping of the automatic switch group are only applicable when the measurement quality is all "Good", "Manual", or "MGood". Next, an automated switch group is constructed using the selected automatic switch (S 108). For example, the interval load calculation unit 141 may configure an automated switch group by selecting only the automated switches whose measurement quality of the automatic switches is " Good ". Next, the section load calculation unit 141 performs a current consistency check for each of the automated switch groups (S109). Here, the current consistency check changes the current measurement quality of all the automation switches of the corresponding automatic switch group to "Bad" when there is more leakage than the influx through the comparison of the inflow and outflow of each automatic switch group. If any one of the automatic switches is detected to be in violation of the current consistency check (S110), the switches to be included in the automatic switch group configuration are selected (S107) to form the switch groups (S108) (S109). If no violation is detected on the current consistency check, the section load calculation unit finally calculates the total amount of load in the section (S105) and distributes the individual section load (S106).

The calculation method of the total amount of load in the section is expressed by Equation (12).

&Quot; (12) "

Here, SWGP _i and SWGQ _i are the effective and reactive power of the i-th automation switch section, respectively, and α _j is the inflow and outflow power direction of the j-th automation switch of the i-th section. Here, the inflow is + and the outflow is -. I _j and θ _j are the current (I _j ) of the jth automation switch and the phase difference (θ _j ) between voltage and current.

The method of distributing the load to the individual section load is expressed by the following equation (13).

&Quot; (13) "

Here, LDP _ij and LDQ _ij denote the effective and reactive power of the individual load in the i-th automated switchgear section, respectively, and Ni denotes the number of individual loads in the section.

5A to 5D are schematic diagrams of a power distribution system for explaining a reduction method of the power reduction unit.

Referring to FIG. 5A, S1 to S13 represent switches, and LD1 to LD32 represent the load of each section. In addition, the presence or absence of the measurement of the data according to the type of the switch is shown in Table 1 below.

[Table 1]

When the state estimation is applied to all the nodes of the power distribution system shown in FIG. 5, the result of the state estimation can not be converged due to insufficient measurement values. In FIG. 5A, it is assumed that all the switches are closed, and the form of the electric bus line is as shown in FIG. 5B.

The rules applied to reduce the system in the system reducer 142 are as follows. First, the nodes of the main facilities of the distribution system are not abbreviated. Here, the main facilities are generators, SVCs, transformers, shunt facilities. Also, the automated switches in which the measurements are present are not abbreviated. However, when the measured value is the measurement quality sent from the field data acquisition device 110 of Fig. 1 as " Bad " and the automatic switch detected as the result of the consistency check " Bad " . Also, the branching node between the automation switch and the automation switch is not abbreviated. In addition, even at the end of a line, it is not included in the abbreviation. In addition, the load is applied to the sum of all the loads between the nodes that are not shortened in the section load.

When the above-mentioned rule is applied and the power distribution system is reduced, it is as shown in FIG. The load of the section reduced by the system reducer 142 is shown in the following Table 2, and the diagram of the load is shown in FIG. 5D.

[Table 2]

As shown in FIGS. 5B and 5D, the system shrinking section 142 reduces the number of buses by approximately 35% by reducing the bus lines of the entire power distribution system from 26 to 17 bus lines. Therefore, the system reduction unit 142 can reduce the number of state variables and improve the calculation speed in the state estimation convergence of the power distribution system and the error data detection.

6 is a flowchart showing a method of detecting error data in the error processing unit.

Referring to FIG. 6, a method for the error processing unit 145 to detect error data using a normalized residual will be described.

The error processing unit 145 calculates a covariance matrix of each measurement value through a state estimation calculation (S141) (S142). The covariance matrix? _Ii is calculated by the following equation (14).

&Quot; (14) "

Where R _i = 1 / σ 2, h _i is the measurement function, G is the gain matrix, and H is the Jacobian matrix. The error processor 145 calculates a measurement error r _i for the measured value and the estimated value according to the following equation (15) (S143).

&Quot; (15) "

는 측정치에 대한 측정 함수,

는 추정된 상태변수, m은 측정치의 수이다. Here, z _i is a measurement value,

Is a measurement function for the measurement,

Is the estimated state variable, and m is the number of measurements.

)를 계산한다(S144).Further, the error processing unit 145 calculates the weighted residual (

Is calculated (S144).

&Quot; (16) "

이 계산되면 이 값 중에서 가장 큰 값을 찾아서 가중잔차에 대한 표준편차를 계산한다(S145). 이는 베드 데이터의 분포가 많은 계통 상황에 대해서는 가중잔차의 표준편차 중 일정이상(보통은 2.5 내지 3.0 σ 이상인 것)의 표준편차를 가지는 모든 측정치를 오류 데이터로 처리하려는 것이며, 이에 대한 선택은 사용자의 선택 옵션에 의해 정해진다. Where r _i is the measurement error and Ω _ii is the covariance matrix. About measurement

And the standard deviation of the weighted residual is calculated by finding the largest value among these values (S145). This is because, for systematic situations in which the distribution of bed data is large, all of the measurement values having standard deviations of a certain number of standard deviations of the weighted residuals (usually, 2.5 to 3.0 σ or more) are processed as error data. It is determined by the selection option.

For example, if the user option is set to remove only the measured value having the maximum weighted residual (S146), the maximum weighted residual is calculated (S147) and it is checked whether it is larger than the set value (S148) (S149). Here, the set value is a reference value for classifying into the error data. If the maximum weighted residual is smaller than the set value, the measured value is not removed. Thereafter, the error processing unit 145 returns to the state estimation operation S141 and repeats the above steps.

For example, if the user option is set to eliminate all of the standard deviation of weighted residuals by more than the set value, it is checked whether the standard deviation of the weighted residuals is larger than the set value (S150), and a measurement having a standard deviation larger than the set value is removed (S151 ). Thereafter, the error processing unit 145 returns to the state estimation computation and repeats the above steps. In this way, the state estimator 140 can shorten the time of the error data detection process according to the characteristics of the target system.

As described above, the apparatus for estimating the state of the power distribution system according to the present invention can relatively accurately calculate a location where a voltage problem occurs in the power distribution system. Further, the present invention greatly improves the error data detection capability and time by reducing the system around the measurement value and increasing the spectral response and varying the error data processing reference by the iterative operation.

In addition, while the existing error data processing method is an operation of removing and repeating the maximum error data, the present invention is based on the consideration of the current status of the distribution system in which a large number of bed data are mixed and the weighted residual that is the error data detection criterion is variable And the error data processing time was shortened. Therefore, the present invention can estimate more realistic section load data using the state estimation result of the power distribution system and the error data processing result.

As described above, the present invention is not limited to the above-described embodiments, and can be applied to a system for estimating the state of a power distribution system according to the present invention It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention.

100: Power distribution system state estimation device 110: Field data acquisition device
120: Field data processing device 130: Main device
140: state estimating unit 141: interval load calculating unit
142: System Reduction Unit 143: System Topology Information Generation Unit
144: state variable calculation unit 145: error processing unit
150: Database

Claims (16)

A distribution system state estimating apparatus for estimating a state of a distribution system by acquiring, from a switch, a measurement of a magnitude of a voltage and a current of a node adjacent to the switch, a phase difference between the voltage and the current,
And a state estimating unit for estimating an interval load of the power distribution system by shortening the power distribution system,
Wherein the state estimating unit includes an error processing unit for detecting error data of the measured value using the weighted residual,
Wherein the error processing unit calculates a covariance matrix of each measurement value through a state estimation calculation, calculates a measurement error, calculates a weighted residual,
The state estimating unit calculates the section load from the measured values and shortens the grid topology to generate connection information between the newly generated reduced bus and each of the facilities and generates information of the grid topology and then uses the system topology and the topology information to calculate admittance The Ybus matrix, which is a matrix, is constructed to perform inverse analysis,
The state estimator calculates an objective function, which is a sum of squares of deviations between a measured value and an estimated value, and constructs a Jacobian matrix. The state estimator constructs a gain matrix using the Jacobian matrix, calculates a state variable variation, Calculating a weighted residual if the value is smaller than the convergence limit, and detecting error data to perform a state variable upgrade and output if there is no error data. The method according to claim 1,
Wherein the state estimator does not abbreviate a node connected to a generator, a switched virtual connection (SVC), a transformer, and a shunt facility. The method according to claim 1,
Wherein the state estimator is configured such that the manual switch is abbreviated and the automatic switch is not abbreviated. The method of claim 3,
Wherein the state estimator reduces the quality of the measured value in the automatic switch and the result of the current consistency check to be " Bad ". The method according to claim 1,
Wherein the state estimating unit does not abbreviate a branch point node between adjacent automation switches. The method according to claim 1,
Wherein the state estimator does not abbreviate the line ends of the power distribution system. The method according to claim 1,
Wherein the state estimating unit further comprises an interval load calculating unit for calculating the interval load pseudo measurement value by checking the current consistency of the measured value. 8. The method of claim 7,
Wherein the section load calculation unit searches for an automatic switch and a line connected to a distributed power source and determines whether or not the line is pressurized by using information on the open and closed states of the node and the automation switch, And a group is formed by using only a circuit breaker formed at the lead-out end and an automatic switch connected to the distributed power source. 8. The method of claim 7,
The section load calculation unit searches for an automatic switch and a line connected to a distributed power source and determines whether or not the line is pressurized by using information on the opening and closing states of the node and the automation switch. If the current state of the state estimation unit is not the initial state, Wherein the automated switches are of the same quality. 10. The method of claim 9,
Wherein the section load calculation unit calculates a load amount of an individual section by calculating a total amount load amount in a section after performing a current consistency test for each group. 10. The method of claim 9,
Wherein the interval load calculator performs a current consistency check for each group and reconfigures the group if one automatic switch breaks the group. delete delete The method according to claim 1,
Wherein the error processing unit calculates a maximum weighted residual among the weighted residuals, classifies the weighted residuals as error data, and deletes the measured values if the maximum weighted residual is equal to or greater than a set value. The method according to claim 1,
Wherein the error processing unit calculates the standard deviation of the weighted residual and classifies the standard deviation into error data and deletes the measured value if the standard deviation is equal to or greater than a set value. delete

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