JP7775639B2 - State estimation device, state estimation method, and state estimation program - Google Patents

Description

The present invention relates to a state estimation device, a state estimation method, and a state estimation program.

Technologies are known for estimating state values such as voltage and current at each node in a power distribution system. For example, Patent Document 1 describes a method in which a power distribution system is divided into an observable subsystem and an unobservable subsystem, and a unique state value is estimated for the observable subsystem, while a range of state values is estimated for the unobservable subsystem.

Patent No. 6109326

By the way, power distribution systems generally include an automatic voltage regulator that is connected in series with the distribution line and can change the transformation ratio between the primary and secondary sides via a tap.

However, the invention described in Patent Document 1 does not take into account the tap position as a state value to be estimated.

The present invention was made in consideration of these issues, and aims to provide a state estimation device that can estimate the tap position of an automatic voltage regulator included in a power distribution system.

One invention for achieving the above object is a state estimation device that estimates the state of a section in a power distribution system that includes a distribution line and an automatic voltage regulator connected in series to the distribution line and capable of changing the transformation ratio between the primary side and the secondary side via a tap. The state estimation device includes: a determination unit that determines the section as a first section if the section consists of a first sensor for measuring power flow measurements, a first line connected to the first sensor, one automatic voltage regulator connected to the first line, a second line connected to the automatic voltage regulator, and a second sensor for measuring power flow measurements connected to the second line; and determines the section as a second section if the section is not determined to be the first section; a first state estimation unit that estimates the load state and the tap position in the first section using a first method if the section is determined to be the first section; and a second state estimation unit that estimates the load state and the tap position in the second section using a second method if the section is determined to be the second section. Other features of the present invention will become clear from the description in this specification.

The present invention makes it possible to estimate the tap position of an automatic voltage regulator included in a power distribution system.

FIG. 1 is a diagram for explaining a power distribution system and a state estimation device. FIG. 10 is a diagram illustrating an example of a first section. FIG. 10 is a diagram illustrating an example of a second section. FIG. 10 is a diagram illustrating another example of the second section. FIG. 2 is a diagram illustrating a hardware configuration of the state estimation device. FIG. 2 is a diagram illustrating a configuration of a storage device. FIG. 2 is a diagram illustrating functional blocks of the state estimation device. FIG. 2 is a diagram illustrating a configuration of a state estimation unit. 10 is a flowchart illustrating a process flow up to determining the classification of a section. 10 is a flowchart illustrating a process flow up to estimating the state of a section classified as a first section. 10 is a flowchart illustrating a process flow up to estimating the state of a section classified as a second section. 10 is a flowchart illustrating a process flow up to estimating the state of a section classified as a second section.

==Embodiment==
<Power distribution system>
1 is a diagram illustrating an example of a power distribution system 1 in which a state estimation device 2 performs state estimation. The power distribution system 1 is, for example, a high-voltage system of a 6.6 kV system, and in this embodiment, includes a distribution substation 10, a distribution line 11, sensor-equipped switches SW (SWa and SWb), and automatic voltage regulators SVR (SVRa and SVRb). The distribution line 11 of the power distribution system 1 is provided with nodes N (Na to Ni) to which loads are connected.

[Distribution substation]
The distribution substation 10 transforms the voltage supplied from a transmission line (not shown) and outputs a voltage of 6.6 kV to the distribution line 11 .

[Power distribution lines]
The distribution line 11 has the distribution substation 10 as its origin (sending node) and is connected to the distribution substations 10 in a radial manner.

[node]
Nodes N (Na to Ni) are provided on the distribution line 11. The nodes N are aggregation units managed for each pole transformer or each designated consumer. The power output from the distribution substation 10 to the distribution line 11 is supplied to consumers (not shown) via the nodes N.

Each consumer acts as a load for electricity. Consumers include facilities (e.g., factories) that consume electricity supplied from distribution line 11. Therefore, distribution line 11 is connected to facilities that consume electricity from distribution line 11.

[Switch with sensor]
The sensor-equipped switch SW is a measuring device capable of measuring the voltage, active power flow, and reactive power flow at the point where it is installed. Hereinafter, the voltage, active power flow, and reactive power flow phase measured by the sensor-equipped switch SW will be collectively referred to as "power flow measurement values" or "power flow measurement values."

The sensor-equipped switch SW periodically measures the voltage, active power flow, and reactive power flow at the installed location. These measurements are stored in a database (for example, constructed in the storage device 203).

The sensor-equipped switches SW are installed midway along the distribution line 11 and divide the distribution system 1 into multiple sections. Details will be described later, but in this embodiment, the sections divided by the two sensor-equipped switches SWa and SWb are defined as sections Ka and Kb.

In addition, when a sensor-equipped switch SW is not installed at the end of the distribution system 1, as in section Kb, the section is defined as the section from the sensor-equipped switch SWa on the primary side (meaning the distribution substation 10 side of the distribution system 1) to the end. In other words, the end of the primary side of the section must be equipped with a sensor-equipped switch SW, and the end of the secondary side of the section (meaning the end side of the distribution system 1) either has a sensor-equipped switch SW installed or is the end of the distribution system 1.

In the power distribution system 1 of Figure 1, section Ka is a section separated by sensor-equipped switch SWa and sensor-equipped switch SW2b. Section Ka includes nodes Na to Ne and automatic voltage regulator SVRa. Automatic voltage regulator SVRa is installed between nodes Nc and Nd. Note that section Ka does not include the section that branches off from node Na and extends from node Na to node Ni.

Section Kb is defined by the sensor-equipped switch SWa and the terminal node (node Ni). Section Kb includes nodes Na, Nf to Ni, and an automatic voltage regulator SVRb. The automatic voltage regulator SVRb is installed between the sensor-equipped switch SWf and node Ng.

[Automatic Voltage Regulator SVR (Step Voltage Regulator)]
The automatic voltage regulators SVR (SVRa, SVRb) are devices that are connected in series to the distribution line 11 and compensate for voltage drops in the distribution line 11.

The automatic voltage regulator SVR can change the transformation ratio between the primary and secondary sides using a tap in response to fluctuations in the secondary side voltage, and adjusts the voltage at a specified point on the secondary side to a preset reference voltage. The automatic voltage regulator SVR of this embodiment uses the LDC (Line Drop Compensation) method as the tap position control method.

Note that the automatic voltage regulator SVR does not output the tap position at each time to the outside. Therefore, the tap position of the automatic voltage regulator SVR becomes one of the state values estimated by the state estimation device 2, which will be described later.

<Classification of sections>
As described above, the sensor-equipped switch SW is disposed at the end of one section of the power distribution system 1, dividing the power distribution system 1 into a plurality of sections. Each of the plurality of sections is classified as a first section or a second section depending on the configuration of the equipment in the section. Each section will be described below.

[Definition of the first section]
The first section is a section consisting of a sensor for measuring power flow measurements, a line, and one automatic voltage regulator SVR. The first section includes two sensors and two lines.

In the first section, one of the two lines (corresponding to the first line) is connected to one of the two sensors (corresponding to the first sensor). An automatic voltage regulator SVR is connected to one of the lines. The other of the two lines (corresponding to the second line) is connected to the automatic voltage regulator SVR. The other of the two sensors (corresponding to the second sensor) is connected to the other line.

Here, one line is connected downstream of one sensor. The automatic voltage regulator SVR is connected downstream of one line. The other line is connected downstream of the automatic voltage regulator SVR. The other sensor is connected downstream of the other line.

The definition of the first section can be rephrased as follows: The first section is a section that includes a sensor-equipped switch SW on both the line from the automatic voltage regulator SVR to the distribution substation 10 side and the line to the terminal side. The first section is also a section that does not include another automatic voltage regulator SVR on either the line from the automatic voltage regulator SVR to the sensor-equipped switch on the distribution substation 10 side or the line to the sensor-equipped switch on the terminal side.

The section that fits the above definition is defined as the "first section."

The "sensor that measures the tidal current measurement value" is, for example, a sensor-equipped switch SW, and in this embodiment, it will be described as a sensor-equipped switch SW.

Figure 2 shows section K1, an example of a section classified as the first section. Section K1 is a section separated by sensor-equipped switch SW1 and sensor-equipped switch SW2.

Section K1 includes sensor-equipped switch SW1, sensor-equipped switch SW2, automatic voltage regulator SVR1, line 111 from sensor-equipped switch SW1 to automatic voltage regulator SVR1, line 112 from automatic voltage regulator SVR1 to sensor-equipped switch SW2, and nodes N1 to N4. Automatic voltage regulator SVR1 is installed between node N2 and node N3.

In other words, section K1 consists of sensor-equipped switch SW1, line 111 connected downstream of sensor-equipped switch SW1, automatic voltage regulator SVR1 connected downstream of line 111, line 112 connected downstream of automatic voltage regulator SVR1, and sensor-equipped switch SW2 connected downstream of line 112. Therefore, section K1 is classified as the first section.

[Definition of the second section]
3 is a diagram showing a section K2, which is an example of a section classified as a second section. The second section is a section that is not classified as a first section.

Figure 3 shows section K2, an example of a section classified as the second section. Section K2 is a section bounded by sensor-equipped switch SW3 and the terminal node (node N7). Section K2 includes nodes N5 to N7 and automatic voltage regulator SVR2. Automatic voltage regulator SVR2 is installed between sensor-equipped switch SW3 and node N5.

In other words, section K2 is not classified as a first section because it has a sensor-equipped switch SW3 installed at only one end and does not have sensor-equipped switches SW installed at both ends. Therefore, section K2 is classified as a second section.

Figure 4 shows section K3, another example of a section classified as the second section. Section K3 is a section separated by sensor-equipped switch SW4 and sensor-equipped switch SW5.

Section K3 includes nodes N8 to N11 and two automatic voltage regulators SVR4 and SVR5. Automatic voltage regulator SVR4 is installed between sensor-equipped switch SW4 and node N8. Automatic voltage regulator SVR5 is installed between nodes N9 and N10.

In other words, because section K3 has two automatic voltage regulators SVR (SVR4, SVR5) installed, it is not classified as a first section. Therefore, section K3 is classified as a second section.

<State estimation method>
A state estimation device 2, which will be described later, performs state estimation on a section to be estimated among a plurality of sections in the power distribution system 1. The state estimation device 2 performs state estimation using a state estimation method that differs depending on the classification of the section.

When the section to be estimated is classified as the first section, the state estimation device 2 performs state estimation using Method 1 (corresponding to the first method), and when the section to be estimated is classified as the second section, it performs state estimation using Method 2 (corresponding to the second method). Below, before explaining the configuration of the state estimation device 2, Methods 1 and 2 will be explained.

[Method 1]
Method 1 is a method for estimating the state value of a section based on power flow measurements at both ends of the section classified as the first section and a state equation. In this embodiment, the "state value of the section" includes the load state of the section and the tap position of the automatic voltage regulator included in the section. The "load state of the section" includes the active power load and reactive power load of each node of the section.

Method 1 involves two steps, in that order: state estimation and power flow calculation. Below, a detailed explanation is provided based on section K1 shown in Figure 2, which is an example of the first section.

1-1. State Estimation In this stage, the following generalized state equation (Equation 1) is used:

Here, y in Equation 2 is the power flow measurement value of the sensor-equipped switch SW, which is the object of measurement. v1s and v2s are the measured voltage values of the sensor-equipped switches SW1 and SW2, respectively, p1s and p2s are the measured active power flows of the sensor-equipped switches SW1 and SW2, respectively, and q1s and q2s are the measured reactive power flows of the sensor-equipped switches SW1 and SW2, respectively.

In addition, x in Equation 3 is a state value of the section to be estimated. In Equation 3, _P1 to _P4 are active power loads of nodes _N1 to _N4 , respectively, _Q1 to _Q4 are reactive power loads of nodes _N1 to _N4 , respectively, and t is the tap position of automatic voltage regulator SVR1.

In Method 1, a solution for the state value x in section K1 can be uniquely obtained based on the state equation (Formula 1) and the measured value y (Formula 2). In this case, for example, by using the least squares method, the state value x in section K1 can be uniquely calculated by searching for the state value _x0 in section K1 that minimizes the evaluation function g in the following Formula 4.

1-2. Power flow calculation In this stage, the voltage distribution and power flow distribution of the section K1 are calculated based on the state value x of the section K1 obtained in 1-1. State estimation, based on the following equations 6 to 9.

Here, the subscripts i and j correspond to points in the section. In this example, "points in the section" correspond to the points in section K1 where sensor-equipped switches SW1 and SW2 are installed, or the points where nodes N1 to N4 are installed.

When the subscript i corresponds to the location of the sensor-equipped switch SW1 or SW2, the subscript i is set to 1s or 2s, respectively. When the subscript i corresponds to nodes N1 to N4, the subscript i is set to 1 to 4, respectively. The same applies to the subscript j.

In Equations 6 and 7, P _i and Q _i are the active and reactive power loads at point i, respectively. _{V i} and θ _i are the amplitude and phase of the voltage at point i, respectively. In Equations 8 and 9, p _ij and q _ij are the active and reactive power flows from point i to j, respectively.

G _ij in Equations 6 to 9 is the real part of the admittance matrix Y _ij in Equation 10 below, which is a conductance. B _ij is the imaginary part of the admittance matrix Y _ij in Equation 10 below, which is a susceptance.

Here, t _ij is the tap position of the automatic voltage regulator SVR when the automatic voltage regulator SVR is installed between points i and j. In other words, each element of the admittance matrix depends on the tap position. Note that when no automatic voltage regulator SVR is installed between points i and j, the element Y _ij of the admittance matrix does not depend on the tap position t _ij .

In Equations 6 to 9, the tap positions t _ij are omitted for the conductance G _ij and the susceptance B _ij .

Furthermore, based on the above explanation, the following correspondences hold between Equations 2, 8, and 9:

The above explains 1-1. State estimation and 1-2. Power flow calculation. Using the above steps, the state values, voltage distribution, and power flow distribution of the first section can be estimated.

[Method 2]
When a section is classified as a second section, the above-described method 1 cannot uniquely estimate the section state values. For example, in section K2 shown in FIG. 3, a sensor-equipped switch SW is not installed at the downstream end, so the required number of conditions cannot be acquired for the number of section state values to be estimated. Furthermore, in section K3 shown in FIG. 4, the tap positions of two automatic voltage regulators must be estimated, so the number of section state values to be estimated is excessive compared to the number of conditions that can be acquired. In such cases, the section state values cannot be uniquely estimated.

Therefore, in Method 2, the state value of the section is estimated based on power flow measurements at least at the upstream end of the second section, the state equation, and information regarding the control method for the tap position of the automatic voltage regulator SVR.

Method 2 involves three steps, in this order: load state estimation, power flow calculation, and tap position estimation. Below, a detailed explanation is provided based on section K2 shown in Figure 3, which is an example of the second section.

2-1. Estimation of Load State In this stage, the tap position is not set as the state value of the section K2 to be estimated, but the load state in section K2 is estimated with the tap position fixed at a predetermined value (initial value). In this stage, the following generalized state equation (Equation 15) is used:

At this stage, similarly to Method 1, a state value of x (Equation 17) excluding the fixed tap position t _ini can be uniquely obtained based on the state equation (Equation 15) and the measured value y (Equation 16). At this time, similarly to Method 1, by using, for example, the least squares method, a state value x ₀ that minimizes the evaluation function g similar to Equation 4 described above can be searched for, thereby uniquely calculating a state value of x excluding the fixed tap position t _ini .

2-2. Power flow calculation At this stage, power flow calculation is performed based on the state values of section K2 obtained in 2-1. Load state estimation, and the power flow distribution in section K2 is calculated. The power flow calculation here can be performed using the same procedure as in 1-2. Power flow calculation.

2-3. Voltage Calculation In this stage, the voltage at a predetermined target point (corresponding to the second point) on the secondary side of the automatic voltage regulator SVR2 is calculated based on the state values excluding the fixed tap position t _ini from the calculation results of the state value x in section K2.

Specifically, the voltage at the target point (corresponding to the second voltage) is calculated based on the voltage (corresponding to the first voltage) at a specified point (corresponding to the first point) on the secondary side of the automatic voltage regulator SVR2, which is one of the calculation results, and the amount of voltage drop from the specified point to the downstream target point, which is obtained from a specified formula in the information related to the control method.

Here, the specified point on the secondary side of the automatic voltage regulator SVR2 can be, for example, node N3, which is adjacent to the secondary side of the automatic voltage regulator SVR. Furthermore, the target point can be a point downstream from the automatic voltage regulator SVR, a preset distance away.

As mentioned above, the automatic voltage regulator SVR2 of this embodiment uses the LDC method as the tap position control method. In this case, the "predetermined formula for information related to the control method" is Equation 18 below.

Equation 18 is an equation for calculating the voltage _vS2 at the target point on the secondary side of the automatic voltage regulator SVR2. In this equation, _vSVR2 is the voltage at a predetermined point on the secondary side of the automatic voltage regulator SVR2. _R2 and _X2 are the resistance and reactance, respectively, from the predetermined point to the target point. _PSVR2 and _QSVR2 are the active power flow and reactive power flow, respectively, on the secondary side of the automatic voltage regulator SVR2.

In Equation 18, the sum of the second and third terms on the right-hand side is the amount of voltage drop from a specified point on the distribution line 11 to the target point.

2-4. Estimation of Tap Position In this stage, the tap position of the automatic voltage regulator _SVR2 is estimated by simulating the LCD method based on the difference between the voltage V _S2 calculated in 2-3. Voltage Calculation and the reference voltage included in the information related to the control method, so that the voltage V S2 becomes the reference voltage.

The tap position estimated by the above procedure is defined as the updated tap position t _new (corresponding to the second position). The updated tap position t _new is the tap position that the automatic voltage regulator SVR2 would have actually changed if the actual load state of section K2 were the state obtained by the above-mentioned 2-1. Load State Estimation. In other words, the updated tap position t _new can be expected to be closer to the actual tap position than the initial value t _ini .

Above, we have explained 2-1. Load state estimation, 2-2. Power flow calculation, 2-3. Voltage calculation, and 2-4. Tap position estimation. These steps constitute one cycle, and by repeating this cycle, we can obtain a tap position that is even closer to the actual tap position. This process is called "convergence calculation" and will be explained in detail below.

2-5. Convergence calculation The tap position t _new of the automatic voltage regulator SVR2 obtained in 2-4. Tap position estimation is set as t _ini again, and 2-1. Load state estimation to 2-4. Tap position estimation are performed again to obtain the updated tap position t _new again. This process is then repeated.

This repetition may be continued until a predetermined number of times is reached, or until the updated tap position t _new no longer changes from the initial value t _ini in one cycle, thereby enabling more accurate estimation of the tap position in the section K2 classified as the second section.

As described above, by classifying the sections of the power distribution system 1 into first sections or second sections and estimating the state using a method appropriate for each classification, it is possible to estimate the tap position of the automatic voltage regulator SVR.

<State Estimation Device>
The state estimation device 2 is a device that estimates the state of a section in the power distribution system 1. The hardware configuration and functional blocks of the state estimation device will be described below.

5 is a diagram showing the hardware configuration of a state estimation device 2 according to one embodiment of the present invention. The state estimation device 2 is a computer having a CPU (Central Processing Unit) 200, a memory 201, a communication device 202, a storage device 203, an input device 204, an output device 205, and a recording medium reading device 206.

The CPU 200 executes the state estimation program 3 stored in the memory 201 or storage device 203 to realize the various functions of the state estimation device 2.

Memory 201 is, for example, RAM (Random-Access Memory) and is used as a temporary storage area for various programs, data, etc.

The storage device 203 is a non-transitory (e.g., non-volatile) storage device that stores various data executed or processed by the CPU 200.

Figure 6 shows how the state estimation program 3 and system information table 4 are stored in the storage device 203.

Various data such as the state estimation program 3 and system information table 4 stored in the storage device 203 are read into the memory 201 and executed or processed by the CPU 200, thereby realizing various functions of the state estimation device 2.

The state estimation program 3 is a general term for programs that realize the functions of the state estimation device 2 according to this embodiment, and includes, for example, application programs, an OS (Operating System), various libraries, etc. that run on the state estimation device 2.

System information table 4 is a table that records the configuration of distribution system 1 and the electrical characteristics of the equipment that makes up distribution system 1.

The system information table 4 stores, for example, data required to simulate the power distribution system 1 using equations such as state equations and power flow equations.

The input device 204 is a device that accepts commands and data input by the user, and includes input interfaces such as a keyboard and a touch sensor that detects the touch position on a touch panel display.

The output device 205 is, for example, a device such as a display or printer.

The communication device 202 exchanges various programs and data with other computers via the network 5.

The recording medium reader 206 reads various data such as the state estimation program 3 and system information table 4 recorded on a recording medium 6 such as an SD card, DVD, or CD-ROM, and stores them in the storage device 203.

6 is a diagram showing functional blocks of the state estimation device 2. The state estimation device 2 includes an acquisition unit 210, a determination unit 211, a state estimation unit 212 (corresponding to a first state estimation unit), a state estimation unit 213 (corresponding to a second state estimation unit), and an output unit 214.

Each of these functions is realized by the hardware of the state estimation device 2 executing the state estimation program 3 according to this embodiment.

[Acquisition unit 210]
The acquisition unit 210 refers to the system information table 4 to acquire the configuration of the section to be estimated and the electrical characteristics of the section. The "section configuration" refers to, for example, the number and arrangement of sensor-equipped switches, nodes, and automatic voltage regulators SVRs in the section. The "section electrical characteristics" refers to the admittance matrix (Equation 10), resistance, reactance (Equation 18), etc. of the section.

[Determination unit 211]
The determining unit 211 determines whether the section to be estimated is the first section or the second section based on the configuration of the section acquired by the acquiring unit 210 .

Specifically, if the section to be estimated meets the definition of a first section described above, the determination unit 211 determines the section to be a first section. On the other hand, if the determination unit 211 does not determine the section to be a first section, it determines the section to be a second section.

In the following explanation, the "sensor that measures the tidal current measurement value" will be assumed to be a sensor-equipped switch SW.

[State estimation unit 212]
The state estimation unit 212 estimates the state values (load state and tap position) of the first section when the determination unit 211 determines that the section to be estimated is the first section. At this time, the state estimation unit 212 estimates the state values of the section by the above-described method 1.

The state estimation unit 212 includes an acquisition unit 212a and an estimation unit 212b. Each is explained below.

- Acquisition unit 212a
The acquisition unit 212a acquires the power flow measurement values from the sensor-equipped switches SW installed at both ends of the first section (Equation 2).

- Estimation unit 212b
The estimation unit 212b estimates the state of the section by the above-described method 1 (1-1. State estimation). That is, the estimation unit 212b estimates the state of the first section (load state and tap position of the automatic voltage regulator SVR) by solving the above-described formulas 1 to 3.

The estimation unit 212b may further calculate the voltage distribution and power flow distribution for the first section based on the obtained load state for the first section, the tap position of the automatic voltage regulator SVR, and Equations 6 to 9 (1-2. Power flow calculation).

[State estimation unit 213]
The state estimation unit 213 estimates the state values (load state and tap position) of the second section when the determination unit 211 determines that the section to be estimated is the second section. At this time, the state estimation unit 213 estimates the state values of the section by the above-described method 2.

Figure 8 shows the configuration of the state estimation unit. The state estimation unit 213 includes an acquisition unit 213a, an estimation unit 213b (corresponding to the first estimation unit), a power flow calculation unit 213c, an estimation unit 213d (corresponding to the second estimation unit), a determination unit 213e (corresponding to the first determination unit), a determination unit 213f (corresponding to the second determination unit), a voltage calculation unit 213g, and a position estimation unit 213h. Each of these units is described below.

- Acquisition unit 213a
The acquisition unit 213a acquires the power flow measurement value from the sensor-equipped switch SW in the second section (Equation 16). The acquisition unit 213a acquires the power flow measurement value at the end of section K of the power distribution system 1. As described above, in this embodiment, the acquisition unit 213a acquires the power flow measurement value from the sensor-equipped switch SW at regular intervals.

- Estimation unit 213b
The estimation unit 213b estimates the load state of the second section using the current measurement value acquired by the acquisition unit 213a and a predetermined initial position t _ini (corresponding to the first position) indicating the tap position (2-1. Estimation of the load state).

Specifically, the estimation unit 213b estimates the load state in the second section by solving the above-mentioned equations 15 to 17 with the tap position fixed at the initial position t _ini .

When performing the above-mentioned convergence calculation (2-5. Convergence calculation), the estimation unit 213b estimates the load state of the second section by setting the updated position t _new (the tap position estimated by the estimation unit 213d described later) as the initial position t _ini .

At this time, if the initial position t _ini and the updated position t _new are not the same, the estimation unit 213b estimates the load state in the second section by setting the updated tap position t _new as the initial position t _ini .

- Tidal flow calculation section 213c
The power flow calculation unit 213c performs power flow calculation for the second section based on the estimation result of the estimation unit 213b (2-2. Power flow calculation). That is, the power flow calculation unit calculates the power flow distribution for the second section using the estimation result of the estimation unit 213b and equations obtained by applying the above-mentioned equations 4 to 7 to the second section.

- Estimation unit 213d
The estimation unit 213d estimates the tap position based on the calculation result of the power flow calculation unit 213c and information on the control method for the tap position of the automatic voltage regulator SVR (2-4. Estimation of Tap Position). The estimated tap position here is the updated position t _new described above.

- Determination unit 213e
When performing convergence calculation (2-5. Convergence Calculation), the determination unit 213e determines whether the initial tap position t _ini and the updated tap position t _new are the same. If the determination unit 213e determines that they are the same, it ends the iteration of the convergence calculation and sets the updated tap position t _new as the tap position. If the determination unit 213e determines that they are not the same, it continues the iteration of the convergence calculation.

- Determination unit 213f
When performing convergence calculation (2-5. Convergence Calculation), the determination unit 213f determines whether the number of times the initial tap position t _ini and the updated tap position t _new are not the same has reached a predetermined number. If the determination unit 213f determines that the number of times has reached the predetermined number, it ends the iteration of the convergence calculation and sets the updated tap position t _new as the tap position. If the determination unit 213f determines that the number of times has not reached the predetermined number, it continues the iteration of the convergence calculation.

Voltage calculation unit 213g
The voltage calculation unit 213g calculates the voltage at a predetermined target point on the secondary side of the automatic voltage regulator SVR based on the state values excluding the fixed tap position t _ini from the calculation results of the state value x of the section (2-3. Voltage Calculation).

Specifically, the voltage calculation unit 213g calculates the voltage v S2 (corresponding to the second voltage) at the target point based on the voltage v _SVR2 (corresponding to the first voltage) at a specified point (corresponding to the first point) on the secondary side of the automatic voltage regulator _SVR , which is one of the calculation results, and the amount of voltage drop from the specified point to the downstream target point (corresponding to the second point), which is obtained from a specified formula (formula 18) in the information related to the control method.

・Position estimation unit 213h
The position estimation unit 213h estimates the tap position based on the difference between the voltage v _S2 at the target point and the reference voltage included in the information about the control method so that the voltage v ₂ at the target point becomes the reference voltage (2-4. Estimation of Tap Position). The estimated tap position is set as the updated position t _new .

[Output unit 214]
The output unit 214 outputs the state value of the section estimated by the state estimation unit 212 or the state estimation unit 213 .

With the above configuration, the sections of the power distribution system 1 can be classified as first sections or second sections, and the tap position can be estimated by estimating the state using a method appropriate for each classification.

<Processing up to determining section classification>
9 is a flowchart illustrating the flow of processing up to when the state estimation device 2 determines the classification of a section. This processing includes steps S101 to S103. Here, this processing will be explained using the power distribution system 1 shown in FIG. 1 as an example.

First, in step S101, the acquisition unit 210 references the system information table 4 and acquires the configuration of the section to be estimated.

In this example, if the section to be estimated is section Ka, the acquisition unit 210 acquires data indicating the relative positions of the sensor-equipped switch SW (SWa, SWb), automatic voltage regulator SVRa, and nodes Na to Ne. On the other hand, if the section to be estimated is section Kb, the acquisition unit 210 acquires data indicating the relative positions of the sensor-equipped switch SW (SWa), automatic voltage regulator SVRb, and nodes Na, Nf to Ne.

Next, in step S102, the determination unit 211 determines whether or not the section is the first section based on the section configuration acquired by the acquisition unit 210 in step S101 and the definition of the first section described above.

In this example, if the section to be estimated is section Ka, section Ka consists of a sensor-equipped switch SWa, a line 11a connected to the sensor-equipped switch SWa, one automatic voltage regulator SVRa connected to line 11a, a line 11b connected to the automatic voltage regulator SVRa, and a sensor-equipped switch SWb connected to line 11b, and therefore the determination unit 211 determines that section Ka is the first section.

If the determination unit 211 determines in step S102 that the section to be estimated is not the first section (S102: N), the process proceeds to step S103. In step S103, the determination unit 211 determines that the section to be estimated is the second section and terminates the process.

If the determination unit 211 determines in step S102 that the section is the first section (S102: Y), the section to be estimated is determined to be the first section, and processing ends.

<Processing up to estimating the state of the section classified as the first section>
10 is a flowchart illustrating the process flow up to estimating the state of a section classified as the first section. This process includes steps S201 to S203. Here, this process will be explained using section Kb of the power distribution system 1 shown in FIG. 1 as an example. As described above, section Ka is a section classified as the first section.

First, in step S201, the acquisition unit 212a acquires power flow measurement values from each of the sensor-equipped switches SW installed at both ends of the section classified as the first section.

In this example, the acquisition unit 212a acquires power flow measurement values from each of the sensor-equipped switches SW (SWa, SWb) installed at both ends of section Ka.

Next, in step S202, the estimation unit 212b estimates the load state of the section and the tap position of the automatic voltage regulator SVR.

In this example, the estimation unit 212b estimates the active and reactive power loads at each of nodes Na to Ne in section Ka, as well as the tap position of the automatic voltage regulator SVRa, using method 1 described above (1-1. State estimation).

Next, in step S203, the output unit 214 outputs the state of the section estimated by the estimation unit 212b in step S202, and the processing ends.

In this example, the output unit 214 outputs the state of section Ka (the active and reactive power loads at each of nodes Na to Ne and the tap position of the automatic voltage regulator SVRa) and ends the process.

<Processing up to estimating the state of the section classified as the second section>
11 is a flowchart illustrating the flow of processing up to estimating the state of a section classified as the second section. This processing includes steps S301 to S307. Here, this processing will be explained using section Kb of the power distribution system 1 shown in FIG. 1 as an example. As described above, section Kb is a section classified as the second section.

First, in step S301, the acquisition unit 213a acquires the power flow measurement value of the sensor-equipped switch SW upstream of the section classified as the second section.

In this example, the acquisition unit 213a acquires power flow measurement values from the sensor-equipped switch SWa installed at the upstream end of section Kb.

Next, in step S302, the estimation unit 213b sets a predetermined initial position t _ini for the tap position.

In this example, the tap position of the automatic voltage regulator SVRb is set. The tap position to be set at this time may be any position, and for example, the tap position that results in an intermediate transformation ratio within the range from the minimum to the maximum transformation ratio is set as the initial position t _ini .

Next, in step S303, the estimation unit 213b estimates the load state of the section with the tap position fixed at the initial position t _ini .

In this example, the estimator 213b estimates the active power load and reactive power load at each of the nodes Na and Nf to Ni with the tap position fixed at the initial position t _ini (2-1. Load Estimation above).

Next, in step S304, the power flow calculation unit 213c performs power flow calculations for the section to be estimated based on the estimation results of the estimation unit 213b in step S303.

In this example, the power flow calculation unit 213c performs power flow calculations for section Kb based on the active power loads and reactive power loads at nodes Na, Nf to Ni estimated in step S303 (see 2-2. Power flow calculations above).

Next, in step S305, the voltage calculation unit 213g calculates the voltage at a specified target point on the secondary side of the automatic voltage regulator SVR based on the calculation results of the power flow calculation unit 213c in step S304.

In this example, the voltage calculation unit 213g calculates the voltage at a specified target point on the secondary side of the automatic voltage regulator SVRb based on the calculation results of the power flow calculation unit 213c in step S304.

Next, in step S306, the position estimation unit 213h estimates the tap position so that the voltage _vS2 at the target point becomes the reference voltage based on the difference between the voltage _v2 at the target point and the reference voltage included in the information about the control method. The estimated tap position is set as the updated position _tnew .

In this example, the position estimation unit 213h estimates the tap position of the automatic voltage regulator SVRb.

Next, in step S307, the output unit 214 outputs the section state (load state and tap position) estimated by the estimation unit 213d and the position estimation unit 213h, and ends the processing.

In this example, the output unit 214 outputs the state of section Kb (the active and reactive power loads at nodes Na, Nf to Ni, and the tap position of the automatic voltage regulator SVRb) and ends the process.

<Processing until the state of the section classified as the second section is estimated (convergence calculation)>
12 is a flowchart illustrating the process flow up to estimating the state of a section classified as the second section, and is a flowchart for performing convergence calculations. This process includes steps S401 to S409. Here, this process will be explained using section Kb of the power distribution system 1 shown in FIG. 1 as an example.

Here, steps S401 to S406 are the same processes as steps S301 to S306 described above, so their explanation will be omitted.

In step S407, the determination unit 213e determines whether the initial tap position t _ini and the updated tap position t _new are the same.

In this example, the determining unit 213e determines whether the initial tap position t _ini and the updated tap position t _new are the same for the automatic voltage regulator SVRb.

If the determination unit 213e determines in step S407 that they are not the same (S407: N), proceed to step S408. If the determination unit 213e determines in step S407 that they are the same (S407: Y), proceed to step S409.

In step S408, the determination unit 213f determines whether the number of times that the initial tap position t _ini and the updated tap position t _new are not the same has reached a predetermined number.

In step S408, if the determining unit 213f determines that the number of times the taps are not the same is less than the predetermined number of times (S408: Y), the process returns to step S403. At this time, the initial tap position t _ini is set to the updated tap position t _new .

In step S408, if the determination unit 213f determines that the number of times the values are not the same has reached the predetermined number (S408: N), the process proceeds to step S409.

In step S409, the output unit 214 outputs the section state (load state and tap position) estimated by the estimation unit 213d and the position estimation unit 213h, and ends the processing.

In this example, the output unit 214 outputs the state of section Kb (the active and reactive power loads at nodes Na, Nf to Ni, and the tap position of the automatic voltage regulator SVRb) and ends the process.

The above processing makes it possible to estimate the tap position of the automatic voltage regulator SVRb included in the power distribution system 1.

In the above embodiment, section Kb shown in Figure 1 was used as an example. Even in section K3, which is classified as the second section shown in Figure 4, the state of section K3 (i.e., the load state and the tap positions of automatic voltage regulators SVR3 and SVR4) can be uniquely estimated by the state estimation device 2 that executes processing based on the above method 2.

Specifically, when the processing shown in FIG. 11 is applied to section K3, in step S301, the acquisition unit 213a acquires power flow measurement values from the sensor-equipped switches SW (SW4, SW5) installed at the upstream end of section K3.

Next, in step S302, the initial tap positions of the automatic voltage regulators SVR (SVR4, SVR5) are set. The tap positions t _ini4 and t _ini5 set at this time may be arbitrary, as in the case of section Kb.

Next, in step S303, the estimation unit 213b estimates the active power load and reactive power load at each of the nodes N8 to N11 while fixing the initial positions of the taps of each of the automatic voltage regulators SVR (SVR4, SVR5) to t _ini4 and t _ini5 (see 2-1. Load estimation above).

Next, in step S304, the power flow calculation unit 213c performs power flow calculations for section K3 based on the active power loads and reactive power loads at each of nodes N8 to N11 estimated in step S303 (see 2-2. Power flow calculations above).

Next, in step S305, the voltage calculation unit 213g calculates the voltage at a predetermined target point on the secondary side of each of the automatic voltage regulators SVR4 and SVR5 based on the calculation results of the power flow calculation unit 213c in step S304 (2-3. Voltage calculation above).

Next, in step S306, the position estimator 213h estimates the tap positions for each of the automatic voltage regulators SVR4 and SVR5 based on the difference between the voltage at the target point and the reference voltage included in the information about the control method, so that the voltage at the target point becomes the reference voltage. The tap positions at this time are designated as updated tap positions t _new4 and t _new5 for the automatic voltage regulators SVR4 and SVR5, respectively.

Furthermore, when the convergence calculation process shown in Figure 12 is applied to section K3, in step 407, it is determined whether the initial tap position and the updated tap position are the same for each of the automatic voltage regulators SVR4 and SVR5.

At this time, if the initial tap positions and updated tap positions for both automatic voltage regulators SVR4 and SVR5 are the same (S408: Y), proceed to step S409; otherwise, proceed to step S408.

==Summary==
As described above, the state estimation device 2 of the embodiment is a state estimation device 2 that estimates a state of a section in a power distribution system 1 that includes a distribution line 11 and an automatic voltage regulator SVR that is connected in series to the distribution line 11 and is capable of changing the transformation ratio between the primary side and the secondary side by a tap, and includes: a determination unit 211 that determines the section to be the first section if the section meets the definition of a first section, and determines the section to be the second section if the section is not determined to be the first section; a state estimation unit 212 that estimates the load state and tap position in the first section by a first method if the section is determined to be the first section; and a state estimation unit 213 that estimates the load state and tap position in the second section by a second method if the section is determined to be the second section.

With this configuration, the sections of the power distribution system 1 can be classified as first sections or second sections, and the tap position can be estimated by estimating the state using a method appropriate for each classification.

In the state estimation device 2, the state estimation unit 213 includes an acquisition unit 213a that acquires power flow measurement values from a sensor upstream of the second section; an estimation unit 213b that estimates the load state of the second section using the power flow measurement values acquired by the acquisition unit 213a and a first position indicating the tap position; a power flow calculation unit that performs power flow calculations for the second section based on the estimation results of the estimation unit 213b; and an estimation unit 213d that estimates the second tap position based on the calculation results of the power flow calculation unit and information regarding the tap position control method of the automatic voltage regulator SVR. This configuration makes it possible to uniquely estimate the tap position not only in the first section but also in the second section.

In the state estimation device 2, the state estimation unit 213 further includes a determination unit 213e that determines whether the first position and the second position are the same. If the first position and the second position are not the same, the estimation unit 213b estimates the load state for the second section, using the tap position estimated by the estimation unit 213d as the first position. With this configuration, the tap position can be estimated with high accuracy when estimating the state value for the second section.

In the state estimation device 2, the state estimation unit 213 further includes a determination unit 213f that determines whether the number of times the first position and the second position are not the same has reached a predetermined number, and if the number is less than the predetermined number, the estimation unit 213b estimates the load state for the second section by using the tap position estimated by the estimation unit 213d as the first position. With this configuration, the tap position can be estimated with even greater accuracy in estimating the second section.

In the state estimation device 2, the estimation unit 213d includes a voltage calculation unit 213g that calculates a second voltage at a predetermined point based on the first voltage at a first point on the secondary side of the automatic voltage regulator SVR among the calculation results and the amount of voltage drop from the first point to a second point downstream, obtained from a predetermined formula in the information related to the control method; and a position estimation unit 213h that estimates a second position based on the difference between the second voltage and a reference voltage included in the information related to the control method so that the second voltage becomes the reference voltage. This configuration makes it easy to estimate the tap position when estimating the second section.

The state estimation method of the embodiment is a state estimation method for estimating the state of a section in a power distribution system (1) that includes a distribution line (11) and an automatic voltage regulator (SVR) that is connected in series to the distribution line (11) and whose transformation ratio between the primary side and the secondary side can be changed by a tap. The state estimation method includes the steps of: determining the section as a first section if the section meets the definition of a first section; determining the section as a second section if the section is not determined to be the first section; estimating the load state and tap position in the first section using the first method if the section is determined to be the first section; and estimating the load state and tap position in the second section using the second method if the section is determined to be the second section.

This method allows the tap position to be estimated by classifying the sections of the power distribution system 1 into first sections or second sections and estimating the state using a method appropriate for each classification.

The state estimation program of the embodiment is a state estimation program that estimates the state of a section in a power distribution system 1 that includes a distribution line 11 and an automatic voltage regulator SVR that is connected in series to the distribution line 11 and whose transformation ratio between the primary side and secondary side can be changed by a tap. The program has a computer that implements: a determination unit 211 that determines the section as a first section if the section meets the definition of a first section, and determines the section as a second section if the section is not determined to be the first section; a state estimation unit 212 that estimates the load state and tap position in the first section using a first method if the section is determined to be the first section; and a state estimation unit 213 that estimates the load state and tap position in the second section using a second method if the section is determined to be the second section.

This program allows the tap position to be estimated by classifying the sections of the power distribution system 1 into first sections or second sections and estimating the state using a method appropriate for each classification.

1: Power distribution system 10: Power distribution substation 11: Power distribution line 2: State estimation device 200: CPU
201: Memory 202: Communication device 203: Storage device 204: Input device 205: Output device 206: Recording medium reading device 210: Acquisition unit 211: Determination unit 212: State estimation unit 212a: Acquisition unit 212b: Estimation unit 213: State estimation unit 213a: Acquisition unit 213b: Estimation unit 213c: Power flow calculation unit 213d: Estimation unit 213e: Determination unit 213f: Determination unit 213g: Voltage calculation unit 213h: Position estimation unit 214: Output unit 3: State estimation program 4: System information table 5: Network 6: Recording medium

Claims (7)

A state estimation device that estimates a state of a section in a power distribution system including a distribution line and an automatic voltage regulator that is connected in series to the distribution line and is capable of changing a transformation ratio between a primary side and a secondary side by a tap, comprising:
a determination unit that determines the section as a first section when the section comprises a first sensor for measuring power flow measurement values, a first line connected to the first sensor, one automatic voltage regulator connected to the first line, a second line connected to the automatic voltage regulator, and a second sensor for measuring power flow measurement values connected to the second line, and that determines the section as a second section when the section is not determined to be the first section;
a first state estimation unit that, when the section is determined to be the first section, estimates a load state and a tap position in the first section by a first method;
a second state estimation unit that, when the section is determined to be the second section, estimates a load state and a tap position in the second section by a second method;
A state estimation device comprising: 2. The state estimation device according to claim 1,
The second state estimation unit
an acquisition unit that acquires tidal current measurement values from a sensor on the upstream side of the second section;
a first estimation unit that estimates a load state in the second section using the power flow measurement value acquired by the acquisition unit and a first position that indicates a position of the tap;
a power flow calculation unit that performs a power flow calculation for the second section based on the estimation result of the first estimation unit; and
a second estimation unit that estimates a second position of the tap based on a calculation result of the power flow calculation unit and information related to a control method for the tap position of the automatic voltage regulator;
A state estimation device comprising: 3. The state estimation device according to claim 2,
The second state estimation unit
a first determination unit that determines whether the first position and the second position are the same;
The first estimation unit
If the first position and the second position are not the same, the position of the tap estimated by the second estimation unit is set as the first position, and the load state of the second section is estimated.
State estimator. 4. The state estimation device according to claim 3,
The second state estimation unit
a second determination unit that determines whether the number of times the first position and the second position are not the same has reached a predetermined number,
The first estimation unit
If the number of times is less than the predetermined number of times, the position of the tap estimated by the second estimation unit is set as the first position, and the load state of the second section is estimated.
State estimator. The state estimation device according to any one of claims 2 to 4,
The second estimation unit
a voltage calculation unit that calculates a second voltage at the second point based on a first voltage at a first point on the secondary side of the automatic voltage regulator among the calculation results and a voltage drop amount from the first point to a second point downstream, the voltage drop amount being obtained from a predetermined equation of information related to the control method;
a position estimation unit that estimates the second position based on a difference between the second voltage and a reference voltage included in the information related to the control method so that the second voltage becomes the reference voltage;
A state estimation device comprising: A state estimation method for estimating a state of a section in a power distribution system including a distribution line and an automatic voltage regulator connected in series to the distribution line and capable of changing a transformation ratio between a primary side and a secondary side by a tap, comprising:
The computer
a step of determining the section as a first section when the section comprises a first sensor for measuring a power flow measurement value, a first line connected to the first sensor, one automatic voltage regulator connected to the first line, a second line connected to the automatic voltage regulator, and a second sensor for measuring a power flow measurement value connected to the second line, and determining the section as a second section when the section is not determined to be the first section;
When the section is determined to be the first section, estimating a load state and a position of the tap in the first section by a first method;
If the section is determined to be the second section, estimating the load state and the position of the tap in the second section by a second method;
A state estimation method including: A state estimation program for estimating a state of a section in a power distribution system including a distribution line and an automatic voltage regulator connected in series to the distribution line and capable of changing a transformation ratio between a primary side and a secondary side by a tap, the program comprising:
On the computer,
a determination unit that determines the section as a first section when the section comprises a first sensor for measuring power flow measurement values, a first line connected to the first sensor, one automatic voltage regulator connected to the first line, a second line connected to the automatic voltage regulator, and a second sensor for measuring power flow measurement values connected to the second line, and that determines the section as a second section when the section is not determined to be the first section;
a first state estimation unit that, when the section is determined to be the first section, estimates a load state and a tap position in the first section by a first method;
a second state estimation unit that, when the section is determined to be the second section, estimates a load state and a tap position in the second section by a second method;
A state estimation program that realizes this.