JP4705563B2 - Distribution system state estimation device, state estimation method and program thereof - Google Patents

Description

  The present invention is a distribution system state estimation device that simultaneously estimates the power flow state of the distribution system, such as voltage and current, and measurement errors of each voltage, current, and the like, based on the facility information and the measurement values of a plurality of time sections, The present invention relates to a state estimation method and a program thereof.

  The need for voltage and current management that grasps the actual situation of the power distribution system is increasing in response to demands for maintaining the voltage at the time of introducing the distributed power supply to the power distribution system and labor saving of new installation and maintenance of the power company. The power system state estimation technology has been developed mainly in the case where the measurement values of each substation (node) can be obtained sufficiently (redundantly) in a high-voltage transmission system. For example, Patent Document 1 discloses a method in which a measured value of a tidal current measured at a plurality of points in an electric power system is weighted and the state of the system is estimated by a weighted least square method.

In the method described in Patent Document 1, it is difficult to estimate a tidal current state when measurement values are not sufficiently obtained, and the information is used when voltage information at each point in the distribution system is obtained. Thus, there is a problem that it is difficult to improve the estimation accuracy.
Thus, as a power flow state estimation method for a distribution system for which sufficient measurement information cannot be obtained, Patent Document 2 discloses a technique for estimating a current in each section in a feeder from a delivery current of a distribution substation. This is a method of measuring the delivery current of the distribution system, allocating it as each section current based on the load characteristic database of each section, and estimating the load current and power in each section.

However, the method described in Patent Document 2 has a problem that it is difficult to improve estimation accuracy using voltage information even when voltage information at each point in the distribution system is obtained. there were.
Therefore, the applicant of the present application disclosed in Patent Document 3 a technique for accurately estimating the power flow state of the distribution system from the voltage / current measurement values limited to the distribution system.
Japanese Patent Publication No. 7-16289 (Claim 1) JP 2003-79071 A (Claim 1) JP 2006-87177 A (paragraph 0015, FIG. 4)

  However, in the method disclosed in Patent Document 3, when voltage and current information at each point in the distribution system is obtained, an inherent measurement error included in the voltage / current measurement device that measures the voltage / current information is corrected. There is a problem that it is difficult to improve the estimation accuracy. Therefore, an object of the present invention is to solve this problem and provide means for estimating the power flow state of the distribution system and the error of each measuring device from the voltage / current measurement values of the distribution system.

State estimating device for a power distribution system according to the present invention has been made to solve the above problems is to store the measured values of the power distribution system conditions including load and the power generation amount of the distribution system at a plurality time section, the node voltage and line flow a measurement database Ru Tei, line constant indicating the impedance of the line of the distribution system, the initial value of the load-power generation, and power flow database that not store contains system configuration data indicating the connection status of the lines and nodes, power flow Load the line constants, initial values of load and power generation, and system configuration data from the database, and calculate the estimated power distribution system state by power flow calculation, and the distribution system state measurement values stored in the measurement database Table the relationship between the true value and the measured value of the deviation between the estimated value of the calculated distribution system state by power flow calculation is calculated and the measuring device the calculated deviation The objective function is formulated expressed in a formula of the sensor error data, by solving the optimization calculation, the estimation of the estimated value and the distribution system state of the sensor error data representing the relationship between the true value and the measured value at each measurement device A distribution system state estimation unit that calculates a correction amount of the value and corrects an estimated value of the distribution system state using the correction amount is provided.

  According to the present invention, from the measurement values of the cross section of the voltage and current from the measurement device installed in the distribution system, the load and power generation amount of the distribution system, the line power flow, the power flow state such as the bus voltage, The measurement error of each measuring device can be estimated with high accuracy.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

(Device configuration)
FIG. 1 is a diagram illustrating a configuration example of a power distribution system and a state estimation device according to the present embodiment. As shown in FIG. 1, the present embodiment is configured by connecting a power distribution system 100 and a state estimation device 10 via a communication network 200.
The distribution system 100 according to the present embodiment, which is a target for estimating the tidal current state, includes a distribution substation 110, a node (bus) 130, a distribution line 140 connected to them, a load 150 connected to the node 130, and power generation. Machine 160 and sensor 170 installed in the power distribution system. Distribution substation 110 also includes distribution substation bus 120 and sensor 170.
The sensor 170 measures the line current at the installation point, the current power factor, the active power P, the reactive power Q, and the voltage V, and sends them to the state estimation device 10 via the communication line 210 and the communication network 200. Send information including measurement values.

  Next, the configuration of the state estimation device 10 will be described. The state estimation device 10 according to the present embodiment includes a display device 11 embodied as a display device, an input unit 12 such as a keyboard and a mouse, a CPU (Central Processing Unit) 13 that executes various programs, and a communication network 200. Communication means 14 for transmitting and receiving information, a RAM (Random Access Memory) 15, and a storage device (power flow calculation database 21, measurement database 22, equipment database 23, state estimation result database 24, sensor error, etc. embodied by a hard disk drive or the like. Each database of the estimation result database 25 and the program data 26) are connected to the bus line 30 and configured.

The CPU 13 executes each program stored in the program data 26, creates image data, displays the image data on the display device 11, searches for data in the storage device, and the like.
The RAM 15 expands each program stored in the program data 26, and displays image data to be displayed on the display device 11 in accordance with instructions from the CPU 13, tidal current calculation results, optimization calculation results, and states output by each program described later. It is a memory for temporarily storing calculation result data such as an estimation result.

The storage device in the state estimation device 10 is provided with five data areas.
In the tidal current calculation database 21, the line constant Z (= R + jX) indicating the impedance of the line, which is a parameter in tidal current calculation, the load / power generation amount (active power P, reactive power Q), and the connection status with the system lines and nodes are displayed. The system configuration data to be represented is stored.

In the measurement database 22, the current I, current power factor, active power P and reactive power Q, and active power P and reactive power Q of the load and the amount of power generation are measured for each time section measured by the sensor 170 in the distribution system 100. , Information including the node voltage V is stored. These data are transmitted from the communication line 210 and the communication network 200 via the communication means 14 of the state estimation device 10 and stored.
In the equipment database 23, the upper and lower limits of the active power P and reactive power Q of the load and power generation amount in the distribution system 100, the daily change pattern thereof, the error formula model of each measuring device (sensor 170) in the distribution system 100 (formula, Data such as coefficients and constants).

In the state estimation result database 24, the active power P, reactive power Q, current I, current power factor, etc. of the line, which are the results of the state estimation calculation, active power P and reactive power Q of load and power generation amount, node voltage V The calculation results such as the line constant Z are stored.
The sensor error estimation result database 25 stores error information estimation results of each measuring device that are obtained simultaneously with the state estimation calculation results.

The program data 26 includes a tidal current calculation program that is a known algorithm for executing tidal current calculation, an optimization calculation program that is a known algorithm for solving quadratic programming (an algorithm for performing optimization calculation), a tidal current calculation program, A state estimation calculation program that appropriately calls an optimization calculation program to calculate a state estimation value of a distribution system, and a display creation program that creates a display screen that displays a state estimation result are stored.
Note that the state estimation calculation program executed by the CPU 13 of the state estimation device 10 calls the power flow calculation program and the optimization calculation program as necessary, so that the “distribution system state estimation unit”, “power flow” A “calculator” and a “sensitivity coefficient calculator” are implemented.
Further, the “display creation unit” is realized by the CPU 13 of the state estimation device 10 executing the display creation program.

(Overview of state estimation method)
Next, the error of the sensor 170 will be described with reference to FIG. For example, FIG. 2 is a graph showing the relationship between the measured value (voltage measured value) of the voltage sensor and the true value (voltage true value). In the graph of FIG. 2, the broken line 220 represents the relationship between the true value and the measured value when there is no measurement error, and the solid line 230 represents the case where the measurement error is included. In general, a measured value of a sensor indicates a value including an error from a true value. Here, consider an example in which the relationship between the true value and the measured value is represented by a linear expression (solid line 230). The relationship between the true value and the measured value of sensor i is shown in the following formula (1).

From this equation, if the coefficient u _i and the constant b _i of the sensor i can be specified, the true value can be obtained from the measured value of the sensor i. The problem of obtaining the sensor error in this way can be considered as a problem of obtaining a coefficient or a constant of an expression representing the relationship between the true value and the measured value of the sensor i. Here, it is assumed that the relationship between the true value and the measured value of sensor i is expressed by a linear expression. In general, however, the linearity error is an error of the absolute value near the rated measured value for both the voltage sensor and the current sensor. It is thought that it is small enough. Therefore, the error reduction effect can be sufficiently expected by approximation of the linear expression, but if the sensor characteristics are known, the approximation expression may be changed, such as approximation by the quadratic expression or omission of the constant b. Moreover, although the example of the voltage sensor was shown here, regarding the current sensor, it may be considered that the relationship between the true value and the measured value is expressed by an approximate expression.

Next, the basic idea of the state estimation method in the present embodiment will be described with reference to FIG. 3 which is an explanatory diagram showing measured values of a time section in a simple distribution system. Here, the error of the sensor 170 (measurement of voltage V, current I, phase θ, etc.) has a characteristic characteristic of each measurement value, and can be approximated by a predetermined mathematical model regardless of the measurement time t. Assume.
Then, from the sensor measurement values of a plurality of time sections (t = 1, 2,... N), the active power P, reactive power Q, measurement error coefficient u, and measurement error constant b of the load in the distribution system 100 are calculated. It has the feature that can be obtained at the same time. By using such an estimation method, it is possible to correct the error of each sensor, so that it can be expected to improve accuracy over the result of state estimation using a single section, and each sensor can be accumulated by accumulating the error coefficient calculation results. It is possible to clarify long-term measurement error correction.

(Operation of state estimation device)
Next, the calculation processing contents of the state estimation calculation program executed by the state estimation apparatus 10 shown in FIG. 1 will be described (see FIG. 1 as appropriate).
Here, FIG. 4 is an example of a flowchart for explaining the execution procedure of the state estimation calculation program. Here, the active power P and reactive power Q (hereinafter referred to as the load / power generation amount P, Q) of the load / power generation amount are estimated at a certain time, and the tidal current calculation is performed using the data. Calculate the voltage, current, and active / inactive power flow.

  First, in step S1, system conditions are set. Here, the line constant Z (= R + jX) necessary for the tidal current calculation, the initial values of the load / power generation amount P, Q are acquired from the tidal current calculation database 21, the equipment database 23, the user input of the input means 12, and the like. This is set by reading to the RAM 15.

Next, in step S <b> 2, the upper and lower limit values of the load / power generation amounts P and Q are acquired from the equipment database 23 and read into the RAM 15, thereby setting the upper and lower limit constraints of the load / power generation amounts P and Q.
In step S3, a tidal current calculation program, which is a known algorithm, is called using the data set in step S1 and step S2, and the tidal current calculation is executed. The voltage of each node, the line tidal current (active / reactive power tidal current, Current and current power factor are calculated), and the calculation result is temporarily stored in the RAM 15.

Next, in step S <b> 4, the measurement value for each time section stored in the measurement database 22 is read into the RAM 15. In addition, it is good also as a structure which reads the measured value of the multiple time cross section measured with the sensor 170 via the communication means 14 and the communication network 200 directly to RAM15, without using the measured value stored in the measurement database 22. FIG.
Here, the measurement database 22 determines whether the measured value is data used for state estimation calculation, whether the sensor is an error-considering sensor, and which time section is used for state estimation. Or can be designated by the user via the input means 12.

Next, in step S5, sensitivity coefficients α and β are calculated based on the power flow calculation result calculated in step S3. This sensitivity coefficient is a coefficient that represents changes in node voltage, line power flow, etc. with respect to changes in loads / power generation amounts P and Q, and details of the calculation method will be described later.
In step S6, the deviation between the tidal current calculation result calculated in step S3 and temporarily stored in the RAM 15 and the measured value read from the measurement database 22 in step S4 is calculated. For example, for a voltage at a certain node m, a deviation ΔVm between the measured value Vm ′ and the power flow calculation result Vm is obtained using −ΔVm = Vm′−Vm. For current, active / reactive power, etc., if there are measured values used for state estimation calculation, the deviation is calculated in the same manner.

  Next, in step S7, the correction amount of the power flow calculation result including the load / power generation amounts P and Q, the error coefficient and the error constant of each sensor 170 are simultaneously calculated. Here, each correction amount, the error coefficient of the sensor, and the error constant are formulated as a quadratic programming problem using the sensitivity coefficient calculated in step S5 and the deviation obtained in step S6, and this expression is optimized. It can be calculated by calling and solving a calculation program. The formulation using the deviation and sensitivity coefficient will be described later. As an optimization calculation program, a solution can be uniquely obtained by using an algorithm for solving a known quadratic programming method.

  Next, in step S8, the load / power generation amounts P, Q of the power flow calculation input data are corrected based on the correction amounts of the load / power generation amounts P, Q calculated in step S7. For this purpose, the state estimation calculation program calls the tidal current calculation program, re-executes tidal current calculation using the corrected system conditions (load / power generation amount P, Q), and the voltage and line power (effective) of each node. Reactive power flow, line current, current power factor, etc.) are calculated, and the calculation results are stored in the state estimation result database 24. Then, the state estimation calculation program calculates a deviation between the tidal current calculation result calculated again and the measured value read out in step S4.

  Next, in step S9, it is determined whether or not the deviation calculated in step S8 is within a predetermined reference value. If this deviation is equal to or greater than a predetermined reference value (Y in step S9), the process returns to step S5, and the correction amounts of the load / power generation amounts P and Q are obtained again. On the other hand, if the deviation is less than the predetermined reference value (N in step S9), the state estimation calculation program is terminated assuming that the system state estimation result has been obtained.

Next, details of the formulation for optimization calculation in step S7 of the flowchart shown in FIG. 4 will be described.
As described above, the correction amount calculation problem of the load / power generation amounts P and Q is formulated as a quadratic programming method. First, the objective function will be described. The objective function is defined as the following equation (2), which is the sum of the measured values of power flow, load / power generation, etc., and the difference between the estimated value and the weighting factor. Equation (2) corresponds to the “formulated objective function” of the present invention.

  Here, y is an intermediate variable that defines the deviation between the measured value and the calculated value of the current I, voltage V, active power P, and reactive power Q, and is expressed by the following equation (3).

These equations are treated as equality constraints in the quadratic programming problem. Here, ΔLp _j represents the correction amount of the active power P of the load / power generation amount connected to the node j, and ΔLq _j similarly represents the correction amount of the reactive power Q. ΔLp _j , ΔLq _j, and y are variables for the optimization problem.

  Next, formulation of the voltage error is shown. The voltage measurement value is assumed to be close to a proportional relationship with respect to the true value, and an error coefficient included in the voltage measurement value is formulated as a variable u. The error coefficient is also treated as a variable in the state estimation calculation, and is similarly estimated. These conditions are formulated with equality constraints as shown in equations (4a) to (4d).

  Next, as the inequality constraints, the measured value of the load / power generation amounts P and Q and the correction amount upper limit constraint of the estimated value are formulated. This is a restriction that sets an upper limit on the correction amount of each load / power generation amount P, Q. Here, for example, it is possible to limit the load for error wrinkling by setting the measured value to be about the measurement error and the load without the measured value to be a large value. Since the upper and lower limits of the load and power generation amounts P and Q can be easily calculated from the upper and lower limit constraints of the load and power generation amounts P and Q, the problem can be solved by using the above formula (4a) as the upper and lower limit constraints. -It can be defined like Formula (4d).

Next, the sensitivity coefficients α and β used in Expression (3) will be described. This sensitivity coefficient is calculated in step S5 of the flowchart shown in FIG. 4. As shown in FIG. 5, for example, when ΔL _j of the load 150 of the node j130 is changed, the voltage change amount of the node i130 is changed. It is an index indicating ΔV _ij , the amount of change in current ΔI _kj flowing through the line k140, the amount of change in active power ΔP _kj , and the amount of change in reactive energy ΔQ _kj . These indicators should be grasped by calculating the power flow by changing the active power P and reactive power Q of the load (power generation amount) slightly from the initial system conditions and calculating the deviation from the power flow calculation results under the initial conditions. Can do. Formulas for calculating the sensitivity coefficient α for the active power change of the load / power generation amount and the sensitivity coefficient β for the reactive power change are expressed by the following formulas (5a) to (5d).

  By solving the quadratic programming problem formulated as described above, correction amounts ΔLp and ΔLq of the load / power generation amounts P and Q can be obtained. Moreover, the algorithm for solving such a quadratic programming problem using a computer can use the well-known thing described in patent document 3, for example.

(Calculation result display example)
Next, an example of the display of the state estimation calculation result will be described with reference to FIG. FIG. 6 is a diagram illustrating an example in which the display creation program is executed in the state estimation device 10 and the state estimation calculation result of the distribution system is displayed on the display device 11. Here, the display on the display device 11 is shown.
On the display device 11, a system diagram 100 a that is a target of state estimation is displayed based on the information indicating the system configuration stored in the tidal current calculation database 21. Are displayed so that the load 150 and the generator 160 can be identified by the node codes, and the measured values of the sensors can be identified by the sensor codes.
In the display shown in FIG. 6, for the convenience of display, the distribution substation bus 120 of the distribution substation 110 is also denoted by the symbol N <b> 1 as in the node 130.

  Further, based on the measurement values, calculation values, and error coefficients of each sensor 170 stored in the measurement database 22, the state estimation result database 24, and the sensor error estimation result database 25, the measurement results, state estimation calculation results, The error coefficient and the error constant of the sensor 170 are displayed in comparison with the list. Here, Table 91 shows the power flow at each measurement point, the error coefficient and error constant of each sensor (here, only the voltage is displayed), Table 92 shows the load at each node, and Table 93 shows the generator connected to each node. The amount of power generation 160 is shown as a comparison between the measured value (or initial value) and the estimated value that is the result of the state estimation calculation. By displaying in this way, the state estimation calculation result can be easily communicated to the user. Here, an example of output to the screen is shown, but the data may be provided to the user as data in a format that can be printed on a document or the like.

As described above, the state estimation device 10 according to the present embodiment described above is based on the measured values such as the voltage and current from the sensors installed in the distribution system, and the tidal current state such as the load / power generation amount of the distribution system, the line power flow, and the bus voltage. And a coefficient representing the measurement error characteristic of each sensor can be estimated. Further, according to the state estimation device 10 of the present embodiment, it is possible to grasp the error characteristics peculiar to each sensor, so that in addition to being able to estimate the sensor true value, it is possible to determine sensor failure and abnormal data. it can.
In addition, data for power flow calculation at each time can be prepared, and the amount of system voltage / current change with respect to system condition changes occurring at future times can be grasped in advance by power flow calculation. It can also be used as a function of a degree evaluation system or a distribution automation system.

It is drawing which showed the example of a structure of a power distribution system and a state estimation apparatus. It is explanatory drawing which shows the relationship between the error of a sensor, and a true value. It is explanatory drawing which shows the concept of the method of correct | amending a sensor error from a multi-time cross section. It is a flowchart which shows a state estimation process algorithm. It is explanatory drawing supplementing how to obtain | require a sensitivity coefficient. It is drawing which shows the example of a display of the state estimation calculation result of a power distribution system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 State estimation apparatus 12 Input means 13 CPU
15 RAM
21 Tidal current calculation database 22 Measurement database 26 Program data 170 Sensor

Claims (8)

A distribution system state estimation device that calculates the power flow state of the distribution system and the error of each measuring device,
Load and the power generation amount of the power distribution system at a plurality time section, a measurement database that has stored the measured value of the power distribution system state including the node voltage and line flow,
And load flow database the line constant indicating the impedance of the power distribution system of the line, the initial value of the load and power generation amount, you are stored include system configuration data indicating the connection status of the line and node,
From the load flow database, and the line constants, reads the initial value and the system configuration data of the load-power generation, power flow calculation unit for calculating an estimate of the distribution system state by power flow calculation,
The read measurement values of the power distribution system state stored in the measurement database, the measured value of the read the distribution system state, the deviation between the estimated value of the power distribution system state calculated by the power flow calculation is calculated, the objective function is formulated expressed in a formula of the sensor error data representing the relationship between the true value and the measured value of each measuring device the calculated deviations, by solving the optimization calculation, before xenon capacitors error data A distribution system state estimation unit for calculating an estimated value of the distribution system state and an estimated value of the distribution system state, and correcting the estimated value of the distribution system state using the modified amount;
A state estimation device for a distribution system, comprising: Further comprising a facility database that stores the upper limit value of the load and power generation amount before the SL distribution system,
The tidal current calculation unit executes the tidal current calculation using the upper and lower limit values of the load / power generation amount of the distribution system as a constraint condition,
The state estimation device for a distribution system according to claim 1. The power distribution system state estimation unit
Using the estimated value of the distribution system state calculated in the power flow calculation unit, a sensitivity coefficient representing the amount of change in the distribution system state with respect to a change in load / power generation amount is calculated, and formulated using the deviation and the sensitivity coefficient by solving the objective function by optimization calculation, calculating the correction amount of the estimated value and the estimated value of the power distribution system state calculated by the flow calculation of the sensor error data,
The state estimation apparatus for a power distribution system according to claim 1 or 2 , characterized in that: Said sensor error data, the true value y in the measuring device, a mathematical model which represents the measured value x by a linear equation y = ux + b to variables,
The distribution system state estimation unit calculates a coefficient u and a constant b of the mathematical formula as an estimated value of the sensor error data.
Claims 1, characterized in to state estimating device for a power distribution system according to any one of claims 3. Among previous SL each measuring device, further comprising an input unit which consider measuring device errors to input information for specifying which one,
The distribution system state estimation unit, according to the information inputted from the input unit, to calculate an estimate of the sensor error data consider measuring device the error,
The state estimation device for a power distribution system according to any one of claims 1 to 4 , wherein: Reading the corrected estimated value of the distribution system state and the estimated value of the sensor error data, and the system configuration data stored in the power flow calculation database, and measuring points, nodes, lines, and loads included in the distribution system Or further comprising a display creation unit for creating a display screen to be displayed in correspondence with the power generation facility,
The state estimation device for a power distribution system according to any one of claims 1 to 5 , wherein: A state estimation method for a distribution system in a state estimation device for estimating a power flow state of the distribution system and an error of each measurement device,
The state estimation device is
Stored in said power flow calculation database state estimating device reads line constant indicating the impedance of the line of the distribution system, the initial value of the load-power generation amount, and the system configuration data indicating the connection status of the line and node , A procedure to calculate the estimated value of the distribution system state including load / power generation, node voltage and line power flow by power flow calculation,
Reads the measured value of the power distribution system states at a plurality time section stored in the measurement database of the state estimation device, the measured value of the read power distribution system state, the estimated value of the power distribution system state calculated by the flow calculation To calculate the deviation from
The objective function is formulated expressed in a formula of the sensor error data representing the relationship between the true value and the measured value of each measuring device the calculated deviations, by solving the optimization calculation, the estimation of the sensor error data Calculating a correction amount of the value and the estimated value of the distribution system state, and correcting the estimated value of the distribution system state using the correction amount;
A method for estimating the state of a distribution system, comprising: The program for making the said state estimation apparatus which is a computer perform the state estimation method of Claim 7 .

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