JP2013074696A - Electric power system voltage control system and electric power system voltage control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control voltages at control object points more than a plurality of voltage control devices arranged in an electric power system by using the plurality of voltage control devices.SOLUTION: An electric power system voltage control system includes: blackboard means (301) where voltage values of the control object points are written and read; calculation means (206, 306) of calculating an index (s) associated with respective voltage control devices (10) on the basis of the voltage values of the control object points that the blackboard means holds, and selecting a voltage control device whose controlled variable should be changed based upon the calculated index (s); and a plurality of individual control devices (20) instructing the selected voltage control device to change the controlled variable so that a value of an object function including the voltage value of the control object point as an argument decreases. The index (s) is calculated based upon the change amount of the object function for the voltage variation amount of the control object point, the voltage change amount of the control object point for the control amount of the voltage control device, and the degree of influence that the voltage control device gives to the object function in single operation.

Description

  The present invention relates to a system and method for controlling the voltage at any point in a power system.

  An allowable voltage value is determined for the electric power sent to each consumer. For example, in Japan, it is 101 ± 6 (95 to 107) V on the low voltage side. Therefore, the electric power company needs to control the voltage of the electric power system so that the voltage supplied to the power receiving equipment of each consumer is within this range.

  In general, the voltage of the power system decreases from the sending substation (distribution substation) toward the end, that is, from upstream to downstream. Conventionally, the transmission voltage from the substation is appropriately controlled by LRT (Load Ratio control Transformer: Transformer with load tap changer), and the tap is changed by pole transformer (high voltage / low pressure). When the voltage drop is significant, control is performed to raise the voltage in an SVR (Step Voltage Regulator). The SVR is a tap-switching type transformer inserted in series in the distribution line (feeder), and controls the voltage by changing the winding ratio (transformation ratio) between the primary side and the secondary side. Usually, SVR is installed in the middle of a distribution line, and maintains a distribution line voltage within a regulation value by adjusting a transformation ratio by automatic tap switching.

  In conventional power system voltage control, voltage control devices such as LRT and SVR operate individually at each point. Therefore, if a plurality of voltage control devices are installed in series, control interferes with each other and wasteful tap operation ( Hunting) and reverse operation may occur. In response to this problem, the voltage of the power system is controlled by centralized control or distributed control of each voltage control device based on a certain index calculated from the deviation of the voltage controlled by each voltage control device from the target voltage. A method for minimizing violations and minimizing the number of tap operations has been proposed (see Non-Patent Document 1, for example).

N.Yorino, M.Nishimoto, T.Shudo, H.Sasaki, H.Sugihara, Y.Nakanishi, "An Optimal Control Problem for TCUL Transformers And Its Suboptimal Control Law for Autonomous Distributed Systems", The Papers of Technical Meeting on Power Engineering, IEE Japan, PE-10-164, PSE-10-163 (1998)

  In recent years, against the backdrop of global environmental problems, large-scale introduction of distributed power sources such as solar power generation and wind power generation using natural energy, cogeneration that supplies both electricity and heat, and fuel cells using hydrogen energy are expected. Yes. These distributed power sources are interconnected downstream of the power system network, but various problems have been pointed out in the conventional system because they do not assume the introduction of a large amount of distributed power sources. For example, there are problems with protection methods that support power supply from lower buses, problems with installation and control of equipment, especially voltage control of the power system when many distributed power sources such as photovoltaic power generation that have significant output changes are installed. It has become. As described above, when a large number of distributed power sources are introduced into the power system, the number of points where the voltage should be controlled can be greatly increased. It is necessary to consider an optimal control problem (hereinafter referred to as a multipoint voltage control problem) for controlling.

  In Non-Patent Document 1, the control problem of the voltage control device is formulated as a control problem of the dynamic system. In order to guarantee the controllability of the system, there is one control target voltage for one voltage control device. It is assumed that. Therefore, it is difficult to directly apply the control method disclosed in Non-Patent Document 1 to the multipoint voltage control problem.

  In view of the above problems, an object of the present invention is to provide a system and method for controlling a voltage at more control target points using a plurality of voltage control devices arranged in a power system.

  According to one aspect of the present invention, a system for controlling the voltage of an electric power system in which a plurality of voltage control devices are arranged is a blackboard means for reading and writing voltage values at control points that are larger than the number of the plurality of voltage control devices. And an index s related to each of the plurality of voltage control devices based on the voltage value of the control target point held by the blackboard means, and based on the calculated index s, the plurality of voltage control devices A calculation means for selecting a voltage control device whose control amount is to be changed, and a voltage value of the control target point provided for each of the plurality of voltage control devices, with respect to the selected voltage control device. And a plurality of individual control devices for instructing to change the control amount so that the value of the objective function having as an argument decreases. Here, the index s is the change amount of the objective function with respect to the voltage change amount of the control target point, the voltage change amount of the control target point with respect to the control amount of the voltage control device, and the voltage control device once. Is calculated based on the degree of influence on the objective function.

  The calculation means may select any one voltage control device having an absolute value of the index s that is greater than and equal to the maximum value among the plurality of voltage control devices. Alternatively, the calculation means is a plurality of calculation units provided in a distributed manner in each of the plurality of individual control devices, and the calculation unit calculates an index s related to the corresponding voltage control device. The individual control device may instruct the voltage control device to change the control amount when the absolute value of the index s related to the corresponding voltage control device is larger than a threshold value.

  The calculation unit repeats the calculation of the index s related to the corresponding voltage control device for a predetermined period, and when any of them is larger than the threshold value, instructs the voltage control device to change the control amount. Also good. Further, the index s may be a moving average value.

  Further, the blackboard means includes a flag indicating the credibility of each voltage value at the control target point, and the calculation means is credible by the flag among the voltage values of the control target point held by the blackboard means. The voltage value shown may be used for calculation of the index s related to each of the plurality of voltage control devices.

  According to the present invention, it is possible to control more voltages at control target points using a plurality of voltage control devices arranged in the power system.

1 is a schematic diagram of a power system voltage control system according to an embodiment of the present invention. Outline diagram of power system voltage control system according to modification Schematic diagram of the power system according to the description of the simplified calculation of the matrix A Schematic diagram of electric power system related to calculation of matrix A by impedance proportional distribution method Operation flow chart of power system voltage control system according to one embodiment of the present invention Schematic diagram showing an example of information held on the blackboard means

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In addition, this invention is not limited to the following embodiment.

1 System Overview FIG. 1 shows an overview of a power system voltage control system according to an embodiment of the present invention. For convenience of explanation, the power system is a 6-bus (ν _{1 to} ν ₆ ) 3-tap system, and the three tap devices are LRT or OLTC (On-Load Tap-Changing Transformer) Transformer) (voltage control device 10 ₁ ) and two SVRs (voltage control devices 10 ₂ , 10 ₃ ) arranged in the middle of the distribution line. Although not shown, any number of distributed power sources such as solar power generation and wind power generation, power storage devices such as storage batteries, and phase adjusting equipment may be connected to any bus.

The system according to the present embodiment controls the voltages ν _{1 to} ν ₆ at _six control target points using the _three voltage control devices 10 ₁ to 10 ₃ . This system includes individual control devices 20 _{1 to} 20 ₃ that control the voltage control devices 10 ₁ to 10 _3, and a central control device 30 that centrally controls the individual control devices 20 _{1 to} 20 ₃ . In the following, the voltage control devices 10 ₁ to 10 ₃ and the individual control devices 20 _{1 to} 20 ₃ may be referred to by omitting the reference numerals unless there is a need to particularly indicate individual devices.

  As a control method of this system, the central control device 30 directly instructs each voltage control device 10 to operate, and each individual control device 20 relays the instruction, and each individual control device 20 has each voltage. There is an autonomous distributed control method in which an operation instruction is given to the control device 10 and the central control device 30 functions as an information sharing device of each individual control device 20.

  In particular, in the autonomous distributed control method, each individual control device 20 functions as an agent that is an autonomous subject that can perceive the state of its own environment and take action by its own decision making to influence the environment. . This system operating in the autonomous distributed control system can be viewed as a multi-agent system in which a plurality of individual control devices 20 as agents are assembled.

2 Detailed Configuration of System Next, a detailed configuration of the system will be described. Each individual control device 20 includes a communication unit 202, a knowledge unit 204, and a calculation unit 206. The centralized control device 30 includes a blackboard unit 301, a communication unit 302, a knowledge unit 304, and a calculation unit 306.

  The communication unit 202 of each individual control device 20 can communicate with the corresponding voltage control device 10. Each individual control device 20 acquires the voltage values and transformation ratios of the primary and secondary buses of the corresponding voltage control device 10 via the communication unit 202 and controls the corresponding voltage control device 10. Or give instructions to change the amount.

  Further, the communication unit 202 of each individual control device 20 can communicate with the communication unit 302 of the central control device 30. Each individual control device 20 exchanges various information with the central control device 30 via these communication units. For example, each individual control device 20 writes the voltage value, the transformation ratio, etc. acquired from the corresponding voltage control device 10 to the blackboard means 301 via these communication units, and other individual control devices 20 can write as necessary. The written voltage value and the like are read from the blackboard means 301.

The communication unit 302 of the centralized control device 30 can communicate with the voltage measuring device 15 that measures the voltage ν ₆ of the bus that is not directly connected to the voltage control device 10 and can acquire the voltage value. In the present embodiment, only one voltage measurement device 15 is arranged, but more voltage control devices 15 may be arranged in the power system in order to measure the voltage at the control target point of this system. Further, when a distributed power source or the like is interconnected, the voltage value may be acquired by communicating with the distributed power source instead of the voltage measuring device 15.

  Note that communication between the communication unit 202 and the voltage control device 10, communication between the communication unit 302 and the voltage measuring device 15, and communication between the communication unit 202 and the communication unit 302 are metal line communication, optical Any of line communication, PLC (Power Line Communication), wireless communication, and the like may be used. The communication protocol is not particularly limited and is arbitrary.

  The knowledge unit 204 of each individual control device 20 stores various information acquired by the communication unit 202, the calculation result of the calculation unit 206, and the like. The knowledge unit 204 can be realized by various memory devices, hard disk devices, and the like.

  The calculation unit 206 of each individual control device 20 calculates the index s related to the corresponding voltage control device 10 using the various information acquired by the communication unit 202 and the various information held in the knowledge unit 204. The calculation unit 206 can be realized by a microcomputer or the like. Details of the index s will be described later.

  In the case of the autonomous distributed control method, each individual control device 20 instructs the corresponding voltage control device 10 to change the control amount via the communication unit 202 based on the index s calculated by the calculation unit 206. . Specifically, each individual control device 20 compares the index s with a positive threshold value α, and if s> α, instructs the voltage control device 10 to lower the tap value, and if s <−α. For example, it instructs the voltage control device 10 to increase the tap value.

  In order to optimally control the voltage of the power system, at most one voltage control device 10 is required to operate at one time. However, in the autonomous distributed control method, when the index s satisfies a predetermined condition, a plurality of voltage control devices 10 are simultaneously transmitted. May work. In order to suppress such a useless operation, a time limit may be provided for an operation instruction to the voltage control device 10. Specifically, each individual control device 20 starts a timer without immediately issuing an operation instruction to the corresponding voltage control device 10 even if the index s calculated by the calculation unit 206 satisfies the condition. The calculation of the index s is repeated for a predetermined period. If the index s still satisfies the condition even if the timer value exceeds the threshold value, an operation instruction is finally issued to the corresponding voltage control device 10 at that time. Note that the timer is reset if the index s does not satisfy the condition while the timer is counting.

  In this way, wasteful operations of the voltage control device 10 are reduced by providing a time limit for the operation instruction to the voltage control device 10. In particular, this is effective when a distributed power source or the like having a large output fluctuation is connected to the power system. For example, even if the output of the distributed power supply fluctuates instantaneously and the voltage at the control target point deviates from the allowable value, if the output of the distributed power supply immediately returns to the original value, the voltage control device 10 is operated wastefully. No need.

  The blackboard means 301 of the centralized control device 30 is a shared memory in which information such as voltage values is read and written from each individual control device 20 as described above, and corresponds to a blackboard model in a multi-agent system. Reading and writing of information may be performed at an arbitrary timing by each individual control device 20 (asynchronous type), or may be performed at a timing at which each individual control device 20 is synchronized (synchronous type). The blackboard means 301 can be realized by various memory devices, hard disk devices, and the like.

  The knowledge unit 304 of the centralized control device 30 stores various information acquired by the communication unit 302, the calculation result of the calculation unit 306, and the like. The knowledge unit 304 can be realized by various memory devices, hard disk devices, and the like.

  The knowledge unit 304 holds information related to the entire system configuration. The centralized control device 30 monitors the entire system configuration based on information from the individual control device 20 and a section switch not shown. For example, a distributed power source is added to or removed from the power system, or When any system configuration change due to switching of the line is detected, the system configuration information held in the knowledge unit 304 is updated. The updated system configuration information is read via the blackboard means 301 or from the knowledge unit 304 and transmitted to each individual control device 20.

  The calculation unit 306 of the centralized control device 30 calculates an index s related to each voltage control device 10 using various information held in the blackboard means 301 and various information held in the knowledge unit 304. The calculation unit 306 can be realized by a microcomputer or the like.

  In the case of the centralized control method, the centralized control device 30 controls one of the voltage control devices 10 via the communication unit 302 and the communication unit 202 of the individual control device 20 based on the index s calculated by the calculation unit 306. To change the control amount. Specifically, the centralized control device 30 instructs the voltage control device 10 whose absolute value of the index s is larger than the threshold and maximum to decrease the tap value if the index s is a positive value, and the index s If is a negative value, an instruction to increase the tap value is given.

  On the other hand, in the case of the autonomous decentralized control method, the calculation result of the calculation unit 306 is not used for the control of the voltage control device 10, but the calculation check of the index s calculated in each individual control device 20 and the backup when the communication function is lost. Therefore, it is only stored in the knowledge unit 304 for analysis / evaluation of operations to be performed later.

  In either the centralized control method or the autonomous distributed control method, the moving average value may be used instead of using the index s as it is. By taking a moving average while appropriately weighting the index s calculated by the calculation unit 206 and the calculation unit 306, it is possible to grasp a tendency while avoiding a sensitive reaction to a sudden voltage fluctuation at a control target point. As a result, useless operation of the voltage control device 10 can be suppressed.

  Further, a flag (credibility flag) indicating the credibility of each voltage value at the control target point may be introduced into the blackboard means 301. The calculation of the index s requires the latest and accurate voltage value at each control target point. However, when the communication between the individual control device 20 and the centralized control device 30 is interrupted, some of the blackboard means 301 is used. There is a possibility that the voltage value is not updated and the index s cannot be calculated correctly. This is particularly a problem when each individual control device 20 autonomously calculates the index s by reading and writing information to the blackboard means 301 asynchronously. Therefore, whether or not the various types of information held in the blackboard means 301 accurately reflect the latest system state is represented by a credibility flag.

  For example, if the credibility flag is “1”, the information has been updated (latest), and if the credibility flag is “0”, this means that it is not, and the default is “0”. Each individual control device 20 sets the credibility flag to “1” to indicate that the voltage value is the latest when writing the acquired voltage value to the blackboard means 301. When the other individual control device 20 and the central control device 30 read the voltage value, if the credibility flag is “1”, the voltage value reflects the current state of the latest system and is reliable. The calculation unit 206 and the calculation unit 306 calculate the index s using the voltage value. On the other hand, if the credibility flag is “0”, the voltage value may not be the latest. In this case, the calculation unit 206 and the calculation unit 306 1) do not calculate the index s, 2) calculate the index s by estimating the voltage value, and 3) calculate the index s by reducing the weight of the voltage value. , Etc. can take various actions.

  Note that the credibility flag is “all” when the system connection state is changed (for example, after system switching) or when the system connection itself is changed (for example, after a certain voltage control device 10 is operated). Reset to 0 ". The credibility flag is updated to “1” every time the latest voltage value is written in the blackboard means 301.

3 Modifications The knowledge unit 204 and the calculation unit 206 of each individual control device 20 may be omitted, and the functions may be integrated into the knowledge unit 304 and the calculation unit 306 of the centralized control device 30. FIG. 2 shows an outline of a power system voltage control system according to a modification. In the modified example, each individual control device 20 includes a communication unit 202, and only relays communication between the central control device 30 and each voltage control device 10. In particular, this modification is advantageous when specializing in a centralized control method.

4. About Index s 4.1 Formulation of Multipoint Voltage Control Problem Next, the index s used in this system will be described. The index s is derived by formulating the multipoint voltage control problem as an optimization problem.

  First, the objective function and constraints of this system are as follows. The symbol R in the constraint condition represents a real number field.

Objective function Voltage deviation: min _n V (ν) (1)

Constraint condition Distribution power characteristic equation determined by tidal equation: ν = h (L, n) (2)
However,
V: R ^X → R ¹ : Scalar objective function (arbitrary setting)
ν = [ν ₁ ,..., ν _X ] ^T ∈R ^X : Voltage value vector (X dimension) of the control target point
n = [n ₁ ,..., n _N ] ^T ∈R ^N : Tap value vector (N dimension)
L = [L ₁ ,..., L _Y ] ^T ∈R ^Y : Fluctuation parameter vector such as load (Y dimension)
h: R ^{Y * N} → R ^X : Transmission / distribution voltage characteristic function

Here, assuming that k = 1,..., N, _nk is a tap value of the k-th voltage control device 10 and is assumed to be sequentially controlled in the form of the following equation. That is, as the voltage control device 10, the following model simulating discrete characteristics is used.

n _k (τ + 1) = n _k (τ) + Δn _k (τ)
Δn _k (τ) = r _k · f _k (τ): tap value change at time τ f _k (τ) = 1 (tap one step up operation) or 0 (non-operation) or −1 (tap one step down operation) (3)

  The above is expressed as a vector as the following equation.

n (τ + 1) = n (τ) + Δn (τ) (4)
However,
Δn (τ) = R · f (τ)
R = diag [r ₁ , ..., r _N ]
f (τ) = [f ₁ (τ),..., f _N (τ)] ^T : Tap control at time τ

  The matrix R is a matrix that represents the degree of influence that the voltage control device 10 has on the objective function in one operation, and specifically, is a matrix that represents the change width of one tap stage.

Now, it is assumed that the tap is operated according to the equations (3) and (4), and as a result of this operation, the optimum solution n ^{* of the} equations (1) and (2) is reached.

  Assuming that the load parameter L is a constant, the value of the objective function changes as follows.

V (ν (τ + 1)) = V (ν (τ)) + ΔV (τ)
ΔV (τ) = ∂V / ∂ν ・ ∂h / ∂n ・ Δn (τ) (5)

  Here, ΔV (τ) is a reduction amount of the objective function due to the tap operation. Therefore, considering the case where only one voltage control device 10 is operated at one time, the method of selecting and controlling the voltage control device 10 that greatly reduces the objective function is the most effective. This can be achieved by examining each voltage control device 10 for the ΔV (τ) value of equation (5). That is, equation (5) can be written as:

ΔV (τ) = w (τ) ・ A (τ) ・ R ・ f (τ)
= S (τ) · f (τ)
= [S ₁ (τ) ... s _N (τ)] [f ₁ (τ) ... f _N (τ)] ^{T
_{= Σ i = 1 N s i}} (τ) f i (τ)
However,
s (τ) = w (τ) ・ A (τ) ・ R
w = [∂V / ∂ν]
A = [∂h / ∂n] = [∂ν / ∂n]

  The matrix w is a matrix representing the change amount of the objective function with respect to the voltage change amount at the control target point. The matrix A is a matrix that represents the voltage change amount at the control target point with respect to the control amount of the voltage control device 10, and is specifically a voltage / tap sensitivity matrix.

  From the above, the index s related to the i-th voltage control device 10 is expressed by the following equation.

s _i = [∂V / ∂ν ₁ … ∂V / ∂ν _X ] [∂ν ₁ / ∂n _i … ∂ν _X / ∂n _i ] ^T r _i (6)

That is, the index s _i represents a change in the objective function when the i-th voltage control device 10 is operated with respect to the objective function V (ν) that is arbitrarily set.

When it is assumed that tap switching of the voltage control device 10 is performed one step at a time, r _i represents a change width per one tap, but two or more taps may be switched at a time. It may be. In such a case, r _i may be appropriately changed.

(Example of objective function 1)
The objective function V (ν) can be defined as, for example, the following equation.

V (ν) = 1/2 ・ (ν−ν _R ) ^T・ M ・ (ν−ν _R )
= 1/2 ・ Σ _{i = 1} ^N m _i (ν _i −ν _{R, i} ) ²
However,
ν _R = [ν _{R, 1} ,..., ν _{R, X} ] ^T ∈R ^X : Target voltage value vector (X dimension) at the point to be controlled
M = diag [m ₁ ,..., M _x ]: Weight matrix of voltage at control target point

  In this case, the index s at time τ is expressed as the following equation.

s (τ) = w (τ) ・ A (τ) ・ R
= (Ν−ν _R ) ^T・ M ・ A (τ) ・ R

  This index s corresponds to the index s disclosed in Non-Patent Document 1 when the voltage to be controlled is one place for one voltage control device, that is, when X = N. That is, the control method proposed by the present invention can include the conventional control method as it is depending on the setting of the objective function.

(Example 2 of objective function)
Next, another example of the objective function V (ν) will be described. Now, let us consider a case where the voltage control device 10 _k controls two point voltages, and let the sending voltage be ν _{1, k} and the terminal voltage of the assigned area be ν _{2, k} . For example, if the voltage control device 10 _1, the voltage [nu _{1, 1} feed voltage [nu _1, the voltage [nu ₂ is the terminal voltage [nu _2,1. Further, the upper and lower voltage ranges for the two point voltages are the same. Optimum control of these two different voltages ν _{1, k} , ν _{2, k} is equivalent to controlling the voltage upper and lower limit values closer to the median value when the voltage upper and lower limit ranges are the same. It is. Here, when the voltage upper limit value is ν _UL and the voltage lower limit value is ν _LL , the voltage median value ν _C is expressed by the following equation.

ν _C = (ν _UL + ν _LL ) / 2

  And when performing the control which makes a several point voltage approach a median value, the value nearer to a voltage upper / lower limit value should be emphasized. Therefore, when a plurality of voltage values are reflected in the control, weighting is performed according to the voltage value at each point. Specifically, voltage values closer to the upper and lower limits of the voltage are increased to increase the reflection sensitivity to control, while voltage values far from the upper and lower voltage limits are decreased to reduce the reflection sensitivity to control. do it.

When _{ν 1, k> ν 2,} k, and calculates a weight beta _{2, k} of the weighting beta _{1, k} and the voltage value [nu _{2, k} of the voltage value [nu _{1, k,} the control target voltage [nu _gamma, a _k less Calculate as follows. When ν _{1, k} <ν _{2, k} , the opposite operation is performed.

β _{1, k} = Δν _{2, k} / (Δν _{1, k} + Δν _{2, k} )
β _{2, k} = 1−β _{1, k} = Δν _{1, k} / (Δν _{1, k} + Δν _{2, k} )
ν _{γ, k} = β _{1, k}・ ν _{1, k} + β _{2, k}・ ν _{2, k} (7)
However,
Δν _{1, k} = ν _UL −ν _{1, k}
Δν _{2, k} = ν _{2, k} −ν _LL

The objective function V (ν) is defined as follows, with the weighted average voltage νγ _{, k} calculated by equation (7) as the control target voltage of the k-th voltage control device 10.

V (ν) = 1/2 ・ (ν _γ −ν _C ) ^T・ M ・ (ν _γ −ν _C )

  In this case, the index s at time τ is expressed as the following equation.

s (τ) = w (τ) ・ A (τ) ・ R
= (Ν _γ −ν _C ) ^T・ M ・ A (τ) ・ R

4.2 Calculation of Matrix A Assuming that the weight matrix M and the change width r _i of one tap stage are known, the information necessary for calculating the index s is the voltage value ν of the control target point and the matrix A. The matrix A corresponds to the system configuration information described above. Information about the voltage value ν can be obtained through the blackboard means 301, but the calculation of the matrix A requires a lot of system information and complicated calculations. Therefore, the calculation of the matrix A may be simplified as follows. This calculation method uses the property that when a certain voltage control device 10 operates, the influence is transmitted from the upper part of the system to the lower part, but it is rarely transmitted to other feeders in parallel or from the lower part of the series to the upper part. is there. Specifically, the centralized control device 30 designates one uppermost bus in the system, and recognizes the connection of each bus from the bus in a radial manner. Then, a matrix A is calculated based on the bus hierarchy information.

For example, in the power system as shown in FIG. 3, the primary bus voltage and the secondary bus voltage of the k-th voltage control device 10 are ν _{p, k} and ν _{q, k} , the upper set of the system is U _k , and the system Let L _{k be the} lower set. In this case, the elements of the matrix A are determined as follows.

∂ν _i / ∂n _k ≈∂ν _{p, k} / ∂n _k = 0 (when i belongs to U _k )
∂ν _i / ∂n _k ≈∂ν _{q, k} / ∂n _k = 1 (when i belongs to L _k )
∂ν _i / ∂n _k = 0 (when i does not belong to either U _k or L _k )

When a distributed power source or the like having the function of an automatic voltage control device (AVR) is interconnected in the system, the distributed power source tries to keep the voltage value constant. Therefore, the elements related to the system lower set L _k may be modified by the following impedance proportional distribution method. For example, assuming that a distributed power source (DG) having an AVR function is connected to the power system as shown in FIG. 4, the concept of the following equation may be given to the system lower set L _k . Z _i is the impedance between the buses.

∂ν _n / ∂n _n = Σ _{i = 1} ^k Z _i / Σ _{i = 1} ^N Z _i × Σ _{i = 1} ⁿ Z _i / Σ _{i = 1} ^k Z _i
= Σ _{i = 1} ⁿ Z _i / Σ _{i = 1} ^N Z _i
However, when the direction of the tap is reversed, the following equation is used.
∂ν _n / ∂n _n = −Σ _{i = 1} ^k Z _i / Σ _{i = 1} ^N Z _i × Σ _{i = 1} ⁿ Z _i / Σ _{i = 1} ^k Z _i
= −Σ _{i = 1} ⁿ Z _i / Σ _{i = 1} ^N Z _i

4.3 Amount of change in local objective function Now, let us assume a case where the objective function of equation (1) is represented by the total value of local objective functions in various places as in Example 1 and Example 2 above. Usually, the structure of such an objective function is realistic. That is,

V (ν) = Σ _{z = 1} ^Z V ^z (ν)

Here, Z represents the total number of local objective functions, and V ^z (ν) represents the zth local objective function. At this time, ΔV (ν) of the objective function can be written as follows with respect to the control amount change of the voltage control device 10.

ΔV (ν) = Σ _{z = 1} ^Z ΔV ^z (ν) (8)

  Further, the change in the local objective function can be calculated as follows.

ΔV ^z (τ) = w ^z (τ) ・ A (τ) ・ Δn (τ)
= Σ _{i = 1} ^N s ^z _i (τ) f _i (τ)
However,
s ^z (τ) = w ^z (ν) · A (τ) · R
w ^z = [w ^z ₁ ... w ^z _X ] = [∂V ^z / ∂ν]

s ^z _k (τ) represents a change in the objective function when the k-th voltage control device 10 is operated with respect to an arbitrarily set local objective function V ^z (ν). Note that s ^z (τ) is a component of the index s as shown in the following equation.

s (τ) = Σ _{z = 1} ^Z s ^z (τ)

4.4 Another Example of Index s The above description assumes that the voltage control device 10 is a tap-switching transformer such as SVR or LRT, but the present invention is not limited to this. The voltage control device 10 is a tap-switchable parallel reactive power supply device such as ShC (Shunt Capacitor) or ShR (Shunt Reactor), or an SVC (Static Var Compensator). FACTS (Flexible AC Tansmission System) equipment such as In particular, the FACTS device can perform high-speed control within one second, and the control amount is continuous, unlike the above-described tap device.

  When the voltage control device 10 is a reactive power supply device such as ShC, ShR, or SVC, the following equation is used for the formulation instead of the equation (5). Q is the reactive power injection amount.

ΔV (τ) = ∂V / ∂ν ・ ∂h / ∂Q ・ ΔQ (τ)
= W (τ) ・ A (τ) ・ R ・ f (τ)
= S (τ) · f (τ)
= [S ₁ (τ) ... s _N (τ)] [f ₁ (τ) ... f _N (τ)] ^{T
_{= Σ i = 1 N s i}} (τ) f i (τ)
However,
s (τ) = w (τ) ・ A (τ) ・ R
w = [∂V / ∂ν]
A = [∂h / ∂Q] = [∂ν / ∂Q]

  The matrix w is a matrix representing the change amount of the objective function with respect to the voltage change amount at the control target point. The matrix A is a matrix that represents the voltage change amount at the control target point with respect to the control amount of the voltage control device 10.

  As described above, the example A can be changed according to the control variable of the voltage control apparatus 10. When the control variable is the reactive power injection amount Q, the index s related to the i-th voltage control device 10 is expressed by the following equation.

s _i = [∂V / ∂ν ₁ ... ∂V / ∂ν _X ] [∂ν ₁ / ∂Q _i ... ∂ν _X / ∂Q _i ] ^T r _i

4.5 Advantages and features of this formulation The advantages and features of this formulation are summarized as follows.

  1) Since the conventional method formulated the control problem of the tap device as a problem of the control of the dynamic system, it was necessary to always keep the stability of the system in mind. This is because the function as an automatic control system was emphasized. However, this formulation focuses only on the improvement of the objective function and ignores the viewpoint of dynamic system control by formulating it as a constrained nonlinear programming method. For this reason, behavior other than the objective function calculated from each voltage value at the control target point is not taken into account, and when the voltage at a specific point becomes a problem when performing control, it is added to the objective function. Need to be handled separately. However, this is a problem of optimal arrangement of voltage control devices and control target points, and is a common consideration that is necessary in any case in the design of a control system.

  2) Since there is no discussion as a dynamic system, there is no need to discuss the controllability of the system. In this formulation, even if there are uncontrollable observation points and local objective functions, they are only ignored. This property is a big problem when it is constructed as a completely independent automatic control system, but it is not a problem when the control is performed while monitoring the whole information by the blackboard method.

  3) In the conventional method, discussion of the equilibrium state was indispensable in order to construct an independent automatic control system. The equilibrium state induces harmful vibration phenomena such as hunting unless properly secured so that no contradiction occurs when setting the objective function. On the other hand, only the objective function needs to be set in this formulation.

  4) In the conventional method, the objective function according to Example 1 is set. This is because the objective function to be set has a restriction to use as a Lyapunov function because it has the characteristic of a Lyapunov function that guarantees the stability of the dynamic system. On the other hand, the present formulation is advantageous in that the objective function can be arbitrarily set because there are no such restrictions.

  5) Since it is formulated as a problem to seek optimization of the nonlinear programming problem, there is a great degree of freedom with respect to the number of control target points and the number of voltage control devices.

  6) Since there is a degree of freedom in setting the objective function, a detailed change of the objective function with respect to the control amount of the voltage control device 10 can be predicted in the form of the equation (8) for any setting. This is a great advantage in improving control performance when combined with a blackboard-type control method.

5 Operation Example of Individual Control Device 20 Next, an operation example of the individual control device 20 when the present system operates in the autonomous distributed control method will be described with reference to the flowchart of FIG. FIG. 6 schematically shows an example of various information held by the blackboard means 301 as a table. Each column in the table is information written by each individual control device 20, and V ₁ and V ₂ represent the primary bus voltage value [pu] and the secondary bus voltage value [pu] of each voltage control device 10. .

  Step 1: The primary bus voltage value and the secondary bus voltage value of the corresponding voltage control device 10 are measured. Note that the measurement value may be appropriately filtered.

  Step 2: The measured voltage value and tap ratio are written in the blackboard means 301. At this time, the reliability flag of the corresponding voltage control device 10 is updated to “1”.

  Step 3: Read the information of the other voltage control device 10 whose credibility flag is “1” from the blackboard means 301 and store it in the knowledge unit 204. It should be noted that the information of the other voltage control device 10 whose credibility flag is “0” is treated as 1) not read, 2) estimated, and 3) reduced weighting.

Step 4: Calculate the index s. For example, in the case of the above objective function example 2, the weighted average voltage ν _γ is calculated.

Step 5: The moving average value s_ave of the index s is calculated and written in the blackboard means 301. For example, the moving average value related to the kth voltage control device 10 is expressed by the following equation. However, a is the sample number of the index s, m _i is the weight for each sample.

s_ave _k = Σ _{b = 0} ^a-1 m _b (s _{k, tb} / a)

Step 6: The absolute value | s_ave _k | of the moving average value is compared with the threshold value α. If | s_ave _k | <α, the timer is reset, timer reset information is written in the blackboard means 301, and the process ends.

Step 7: If | s_ave _k |> α, if the timer is stopped, start the timer and write the timer start information to the blackboard means 301. If the timer has already started, continue the timer.

  Step 8: Referring to the blackboard means 301, it is confirmed whether or not its own moving average value is the maximum, that is, whether or not it is larger than the moving average value of any other voltage control device 10 whose timer has started.

Step 9: If | s_ave _k | is maximum, it is determined whether or not a special control criterion is satisfied. For example, when the moving average value or the integrated value of the voltage violation is considerably large, an operation instruction is given to the corresponding voltage control device 10 even if the timer does not reach the upper limit. Note that this step is optional and may be omitted.

  Step 10: Determine whether the timer has reached the upper limit. If the timer has not yet reached the upper limit, it ends.

  Step 11: It is determined whether or not there is another moving average value having the same value as the moving average value of itself. If it does not exist, the process proceeds to the determination of whether or not the corresponding voltage control device 10 is operable.

Step 12: If there is another moving average value that is the same as its own moving average value, it is determined whether or not the voltage deviation | ν _k −ν _R | is larger than the dead zone ε. If it is larger, the process proceeds to a determination of whether or not the corresponding voltage control device 10 is operable, and if smaller, the process is terminated.

  Step 13: It is determined whether or not the corresponding voltage control device 10 is operable. If the tap value of the voltage control device 10 has reached the upper limit value or the lower limit value, it is impossible to further increase or decrease the tap value.

  Step 14: If the corresponding voltage control device 10 is operable, an operation instruction is issued to the voltage control device 10. Then, the blackboard means 301 resets various flags relating to itself (for example, an operable flag), and the process ends.

  Step 15: If the corresponding voltage control device 10 is not operable, the blackboard means 301 resets various flags relating to itself and ends. If the sub-timer is started and an inoperable state continues for a certain period or longer, an operation instruction may be issued to another voltage control device 10.

  Since the power system voltage control system and method according to the present invention can control more voltages at a point to be controlled using a plurality of voltage control devices arranged in the power system, the power distribution system and the ship system This is useful for voltage control.

DESCRIPTION OF SYMBOLS 10 Voltage control apparatus 20 Individual control apparatus 206 Calculation part (calculation means)
306 Calculation unit (calculation means)
301 Blackboard means

Claims (11)

A system for controlling the voltage of a power system in which a plurality of voltage control devices are arranged,
Blackboard means for reading and writing voltage values of control target points greater than the number of the plurality of voltage control devices;
An index s associated with each of the plurality of voltage control devices is calculated based on the voltage value of the control target point held by the blackboard means, and control is performed among the plurality of voltage control devices based on the calculated index s. A calculation means for selecting a voltage control device whose amount is to be changed;
The control amount is provided corresponding to each of the plurality of voltage control devices, and the control amount is changed with respect to the selected voltage control device so that the value of the objective function using the voltage value at the control target point as an argument decreases. A plurality of individual control devices for instructing
The index s is the change amount of the objective function with respect to the voltage change amount at the control target point, the voltage change amount at the control target point with respect to the control amount of the voltage control device, and the voltage control device in one operation. The power system voltage control system is calculated based on the degree of influence on the objective function. The power system voltage control system according to claim 1,
The i-th voltage control device is a tap-switching transformer;
An index s related to the i-th voltage control device is:
s _i = [∂V / ∂ν ₁ ... ∂V / ∂ν _X ] [∂ν ₁ / ∂n _i ... ∂ν _X / ∂n _i ] ^T r _i
(Where V is the objective function, ν ₁ ,..., Ν _X are each voltage value at the control target point at a certain time, n _i is the tap value of the voltage control device at the time, and r _i is the voltage control device. 1), the power system voltage control system. In the electric power system voltage control system as described in any one of Claim 1 and 2,
The electric power system voltage control system, wherein the calculation means selects any one of the plurality of voltage control devices whose absolute value of the index s is larger than the threshold value and maximum. In the electric power system voltage control system as described in any one of Claim 1 and 2,
The calculation means is a plurality of calculation units provided in a distributed manner in each of the plurality of individual control devices,
The calculation unit calculates an index s related to the corresponding voltage control device,
The individual control device instructs the voltage control device to change a control amount when the absolute value of the index s related to the corresponding voltage control device is larger than a threshold value. system. The power system voltage control system according to claim 4,
The calculation unit repeats the calculation of the index s related to the corresponding voltage control device for a predetermined period, and when all of them are larger than the threshold value, instructs the voltage control device to change the control amount. Power system voltage control system characterized by. In the electric power system voltage control system as described in any one of Claim 1 to 5,
The power system voltage control system, wherein the index s is a moving average value. In the electric power system voltage control system as described in any one of Claim 1 to 6,
The blackboard means includes a flag indicating the credibility of each voltage value at the control target point,
The calculation means uses a voltage value whose reliability is indicated by the flag among the voltage values of the control target point held by the blackboard means for calculating the index s associated with each of the plurality of voltage control devices. A power system voltage control system characterized by that. A method for controlling the voltage of a power system in which a plurality of voltage control devices are arranged,
A first step of calculating an index s associated with each of the plurality of voltage control devices;
A second step of selecting a voltage control device whose control amount should be changed among the plurality of voltage control devices based on the calculated index s;
A third step of changing a control amount of the selected voltage control device so that a value of an objective function having an argument of a voltage value of a control target point larger than the number of voltage control devices is decreased,
The index s is the change amount of the objective function with respect to the voltage change amount at the control target point, the voltage change amount at the control target point with respect to the control amount of the voltage control device, and the voltage control device in one operation. A power system voltage control method characterized in that the power system voltage control method is calculated based on the degree of influence on the objective function. The power system voltage control method according to claim 8,
The i-th voltage control device is a tap-switching transformer;
An index s related to the i-th voltage control device is:
s _i = [∂V / ∂ν ₁ ... ∂V / ∂ν _X ] [∂ν ₁ / ∂n _i ... ∂ν _X / ∂n _i ] ^T r _i
(Where V is the objective function, ν ₁ ,..., Ν _X are each voltage value at the control target point at a certain time, n _i is the tap value of the voltage control device at the time, and r _i is the voltage control device. 1), the power system voltage control method. The power system voltage control method according to any one of claims 8 and 9,
In the second step, one of the plurality of voltage control devices is selected as one of the voltage control devices whose absolute value of the index s is larger than the threshold value and the maximum value. . The power system voltage control method according to any one of claims 8 and 9,
In the second step, one or more voltage control devices whose absolute value of the index s is larger than a threshold value are selected from the plurality of voltage control devices.

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