JPH0530660A - Voltage stability monitor/controller - Google Patents

Abstract

PURPOSE:To improve a voltage stability by load transfer or the adjustment of a generator output by a method wherein a means which calculates a voltage stability index, a means which calculates a sensitivity factor and a means which obtains a load switching rate or a load switching rate and a generation adjustment rate by a linear programming method are provided. CONSTITUTION:A state variable initiallization means 21 receives measured values of the states of a power system 1, such as the measured values of active powers of loads and generators, reactive powers and generator voltages, which are inputted from transmitters 2 and 3 and calculates power flow and determines the state variable values in an initial state. Then a voltage stability index initiallization means 22 calculates a voltage stability index from the state variable values determined by the state variable initiallization means 21. A voltage sensitivity factor calculating means 23 obtains a Jacobian matrix by using the state variable values determined by the state variable initiallization means 21 or a stability index calculating means 27 to calculate a voltage sensitivity factor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage stability monitoring control device for monitoring or controlling the voltage stability of a power system.

[0002]

2. Description of the Related Art In the prior art, voltage stability of a power system is enhanced by controlling voltage and reactive power flow by a voltage reactive power regulator (hereinafter referred to as a phase regulator).

However, if there is an unexpected and sudden increase in demand that exceeds the voltage / reactive power adjustment capability of the phase modulating device, there is a risk that the voltage stability will decrease even if the capacity of the phase modulating device is completely used up. is there.

[0004]

SUMMARY OF THE INVENTION The present invention is intended to enhance voltage stability of a power system without using a phase modifying device, and to adjust load transfer or generator output (power generation adjustment) in a substation of a lower system. It is an object of the present invention to provide voltage stability monitoring designed to enhance voltage stability.

[0005]

In order to achieve the above object, the present invention provides a means for calculating a voltage stability index, a means for calculating a sensitivity coefficient for the voltage stability index, and a linear programming method for determining the voltage stability. It is configured by means for obtaining the load switching amount or the load switching amount and the power generation adjustment amount so that the load switching amount becomes maximum under the constraint condition.

In general, the power system is operated with the lower system having a radial (or tree-like) configuration. The magnitude of the load of the upper system substation is determined by the system configuration of the lower system, and between some upper system substations, a certain substation is created by changing the system configuration of the lower system, that is, by changing the radial shape. Load transfer to another substation (hereinafter also referred to as load switching).

The load switching will be described with reference to FIG.
In FIG. 4, assuming that the circuit breakers 1, 2, 3, 5, and 6 are closed and the circuit breaker 4 is open, the C substation and the D substation are connected to the A substation. The load of Substation A is 1000MW + 500MW = 1500MW, and only Substation E is connected to Substation B,
The load of Substation B is 750 MW.

If the circuit breaker 3 is opened and the circuit breaker 4 is closed, the D substation is switched from the A substation system to the B substation system, and the D substation load is changed to the A substation. Moved to B substation. That is, the load at Substation A is 1.
000MW, B substation load is 750MW + 50
It becomes 0 MW = 1250 MW.

Therefore, when the voltage stability of the entire system is deteriorated due to the heavy load at a specific substation, the system configuration of the lower system is changed and the voltage stability is relatively changed from the heavy load substation. By shifting the load to a high substation (that is, switching the load), the voltage stability of the power system can be improved.

It is also known that the greater the electrical distance between the power plant and the load, the worse the voltage stability. Therefore, the voltage stability is improved by generating more power at a power plant as close as possible to an area with low voltage stability. That is, the voltage stability can be improved also by adjusting the generator output (transition to power generation).

[0011]

The operation of the case of improving the voltage stability by switching the load will be described below. First, the voltage stability index calculating means calculates the stability index. Next, if the load value changes by means of calculating the sensitivity coefficient,
A voltage stability coefficient indicating how much the voltage stability index changes is calculated. The load switching amount calculation means calculates the load switching amount for increasing the voltage stability by the linear programming method, using the sensitivity coefficient and various constraints on the operation of the power system. The voltage stability index when the load switching is performed is calculated and compared with the previously calculated index value. As a result, if the amount of improvement in the voltage stability index is small, it cannot be improved any more, and the process is terminated. If not, the above process is repeated again.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of an embodiment of a voltage stability monitoring control device according to the present invention. In FIG. 1, 1 is a power system, 2 and 3 are transmission devices (remote monitoring and control devices), 4 is an electronic computer, and 5 is a man-machine interface device.

FIG. 2 shows a flow chart of the processing means according to the present invention. In FIG. 2, 21 is a state variable initialization means, 22 is a voltage stability index initialization means, 23 is a voltage sensitivity calculation means,
Reference numeral 24 is state variable correction means, 25 is voltage stability sensitivity coefficient calculation means, 26 is load switching amount calculation means, 27 is voltage stability index calculation means, 28 is convergence determination means, and 29 is load switching operation means.

In FIG. 1, measurement data of the state of the power system 1 is input to the electronic computer 4 via the transmission devices 2 and 3. The electronic computer 4 uses these measurement data to obtain the load switching amount, the power generation adjustment amount, and the phase adjustment device adjustment amount for improving the voltage stability of the power system, and based on these amounts. , The voltage stability of the power system is controlled by remotely controlling the equipment of the power system via the transmission devices 2 and 3. Further, the man-machine interface device 5 displays the above-mentioned various quantities, the voltage stability coefficient, and the like.

Next, processing means in the electronic computer 4 will be described with reference to FIGS. 2 and 3. First, the physical principle of the method for improving the voltage stability of the power system will be described. The voltage stability index S used here is the slope of the total demand P-voltage V curve, that is, the voltage sensitivity dV _i / d with respect to changes in the total demand.
The sum of P, S = ΣdV _i / dP (1)

[0016] An example of a P-1 / S curve and P-V _i curves in FIG. In addition, when the relationship between the voltage stability index S and the total demand P is illustrated, the value of S becomes infinite at the static voltage stability limit point. Therefore, in FIG. S). As shown in FIG. 3, the value of the reciprocal 1 / S of the voltage stability index changes in the direction of the arrow as the total demand P increases from the current point A as a starting point. In other words, the value monotonically increases as the total demand P increases, and becomes zero at the tip of the curve which is the static voltage stability limit point. Therefore, the value of the voltage stability index S is the total demand P
It decreases monotonically with an increase in the voltage and becomes negative infinity at the static voltage stability limit point, that is, at the tip of the curve. That is, the value of the index S is larger as the voltage stability is higher (negative value has a smaller absolute value), and is smaller as the stability is lower (negative value has a larger absolute value).

In this way, the static voltage stability of the entire power system can be evaluated by the index S. The voltage sensitivity dV / dP with respect to the total demand can be calculated from the Jacobian matrix in the power flow calculation. Further, the sensitivity coefficient of the load L _{j to} the index S, that is, the voltage stability sensitivity coefficient A _j = dS /
dL _j is calculated from the index S in the current state and the index S ′ in the state in which the negative j is changed by D _j . As required.

From the above consideration, it is understood that the static voltage stability of the power system can be improved by performing the load switching so that the index S is maximized under the predetermined constraint condition regarding the system operation. That is, the following non-linear optimization problem may be solved.

Maximization: S = f (L ₁ , L ₂ , ..., L _j , ...) (3) Constraints: _{Lmin j ≦ L j ≦ Lmax j} ... (5) Vmin k ≦ V k ≦ Vmax k ... (6) where, TL = demand L = Load: control variable V = Roh - mode voltage Lmin = load lower limit Vmin = Lower limit value of voltage Lmax = upper limit value of load Vmax = upper limit value of voltage j: load transfer target node k: upper and lower limit voltage target node of voltage.

Equation (4) represents the condition of supply and demand balance. Expression (5) represents the limit of the load switching amount. (6)
The equation represents the voltage limit. In general, it is difficult to directly solve a non-linear optimization problem while remaining non-linear, so the following linearization is performed. That is, when the equations (2) to (6) are linearized with respect to a minute change from the current state L _{o, j} , V _{o, k} ,

[0021] Lmin _j −Lo _{, j} ≦ ΔL _j ≦ Lmax _j −Lo _{, j} (9) Vmin _k −V _{o, k} ≦ ΔV _k ≦ Vmax _k −V _{o, k} … (10) Where B _{k, j} = sensitivity coefficient of change in voltage V _k with respect to change in load L _j .

It becomes Further, since a linearization error occurs when the value of ΔL _j is large, a constraint condition −ΔLmax ≦ ΔL _j ≦ ΔLmax (12) that limits the load switching amount in one calculation is added. By applying the linear programming method to the expressions (7) to (12), the load switching amount ΔL _j for increasing the static voltage stability can be obtained. For the node load L _{t, j} = L _{t-1, j} + ΔL _{t, j of the t-th} calculation, the power flow calculation and the linear programming calculation are performed again. This is repeated until the index S does not increase. According to the above-mentioned physical principle for improving the voltage stability, the load switching amount for improving the voltage stability is obtained by the processing means and processing procedure shown in FIG.
The details of the processing means shown in FIG. 2 will be described below.

First, the state variable initialization means 21 inputs the measured values of the state of the power system input from the transmission devices 2 and 3, that is, the measured values of the active power and reactive power of the load and the generator, and the generator voltage. The power flow is calculated as, and the state variables in the initial state (that is, the magnitude V of the node voltage and the phase angle δ)
Determine the value of. Since the method of calculating the power flow is a known technique, it will be omitted. Further, the value of the number of times t of calculation is repeated is set to 1. The state estimation calculation may be used instead of the power flow calculation.

Next, the voltage stability index initialization means 22
The voltage stability index S is calculated from the value of the state variable determined by the state variable initialization means 21. That is, dV _i / dP is obtained by the method shown in the following known document, and the index S
Calculate _o = ΣdV _i / dP. Publicly known literature: "Direct Solution of Voltage Stability Limit of Power System", The Institute of Electrical Engineers of Japan, Volume 110, No. 11, P.895 ~ P.902, (Heisei 2-
(November issue)

The voltage sensitivity coefficient calculation means 23 is a state variable initialization means 21 or a stability calculation index calculation means 27 described later.
The Jacobian matrix [H] is obtained by using the value of the state variable determined by the above, and the voltage sensitivity coefficient B _{k, j} is calculated. That is, B _{k, j} = ΔV _k / F _j (13) [..., ΔV _k , ..., Δδ _k , ...] ^T = [H] ^-1 [O, ..., F _j , O, ..., O] ^T
… (1
4) Here, T represents the transpose of the matrix (or vector). The method for obtaining the Jacobian matrix is the same as the method used in the power flow calculation and is a known technique, so description thereof will be omitted.

The state variable correcting means 24 obtains the value of the state variable when the load of the j node is changed by D _j by power flow calculation, and constructs a Jacobian matrix from the obtained value of the state variable.

The voltage stability sensitivity coefficient calculation means 25 uses the result of the state variable correction means 24, that is, the Jacobian matrix, in the same manner as the stability index initialization means 22, when the load is changed by D _j. Voltage stability index S ′ of the To calculate.

The means 23, 24 and 25 are repeated for the number of target nodes.

The load switching amount calculation means 26 includes (7) to (1
Apply the linear programming method to the equation (2) to obtain the optimum load switching amount ΔL _{t, j} at the t-th time.

The stability index calculating means 27 is a load L after the load switching calculated by the load switching amount calculating means 26 is carried out.
_{The power} flow is calculated for _{t, j} = L _{t-1, j} + ΔL _{t, j} to calculate the index S _t .

The convergence determination means 28 makes a convergence determination. That is, a small convergence judgment value ε that is appropriately determined in advance
And the maximum iteration count limit value t _max | S _t −S
_{If t−1} | ≦ ε or t ≧ t _max, it means that the convergence or the calculation has been terminated, so that the process proceeds to the load switching operation means 29. If not, S _t → S _t-1 , L _t → L _t-1 , t + 1 → t,
Returning to the means 23, the calculation is repeated.

The load switching operation means 29 creates a system operation procedure for performing the load switching determined as described above, and operates the system. Since the method of creating the operation procedure and the method of executing the operation procedure are known techniques, the description thereof is omitted.

As described above, according to the embodiment, the voltage stability can be improved by switching the load without using a device such as a phase adjusting device, and a power failure caused by the voltage instability can be achieved. The fear of can be avoided in advance.

(Other Embodiment 1) In the embodiment described above, the stability of the voltage is improved by switching the load. Generally, the difference between the electrical characteristics of the load and the output of the generator is its sign. Therefore, in order to improve the voltage stability by adjusting the generator output, the formulas (7) to (12) in the above process may be changed to the following formulas (15) to (20), which is the same as the above embodiment. The amount of power generation adjustment can be determined by the processing. That is, (15) ~
Equation (20) is

[0035] Gmin _m −G _{o, m} ≦ ΔG _m ≦ Gmax _m −G _{o, m} (17) −ΔG max ≦ ΔG _m ≦ ΔG max… (18) Vmin _k −V _{o, k} ≦ ΔV _k ≦ Vmax _k −V _{o, k} … (19) Here, G = generator output: control variable Gmin = lower limit value of generator output Gmax = upper limit value of generator output m: generator output adjustment target node.

It becomes The determined generator adjustment amount ΔG is
It is controlled by load frequency control (AFC or LFC). From the above, it is understood that the same effect as the load switching can be obtained by the power generation adjustment.

(Other Embodiment 2) It is apparent that the effect of improving the voltage stability is further enhanced by simultaneously performing the load switching and the generator output adjustment. In this case, (21) ~
It suffices to perform the optimization process on the equation (29).

[0038] Lmin _j −Lo _{, j} ≦ ΔL _j ≦ Lmax _j −Lo _{, j} (24) −ΔL max ≦ ΔL _j ≦ ΔL max (25) Gmin _m −G _{o, m} ≦ ΔG _m ≦ Gmax _m −G _{o, m ... (26) -ΔGmax ≦ ΔG} m ≦ ΔGmax ... (27) Vmin k -V o, k ≦ ΔV k ≦ Vmax k -V o, k ... (28)

(Other Embodiment 3) If the phase adjusting device (for example, shunt reactor or condenser) is also adjusted at the same time, the effect becomes more remarkable. In this case, the following processing may be performed. Since the number of conditional expressions that need to be considered only increases, the voltage stability can be improved by applying the same processing to the following examples (30) to (40), and the effect is It gets even bigger.

[0040] Lmin _j −L _{o, j} ≦ ΔL _j ≦ L max _j −L _{o, j} … (33) −ΔL max ≦ ΔL _j ≦ ΔL max… (34) Gmin _m −G _{o, m} ≦ ΔG _m ≦ Gmax _m −G _{o, m} … (35) −ΔG max ≦ ΔG _m ≦ ΔG max… (36) Qmin _n −Q _{o, n} ≦ ΔQ _n ≦ Qmax _n −Q _{o, n} … (37) −ΔQ max ≦ ΔQ _n ≦ ΔQ max… (38) Vmin _k −V _{o, k} ≦ ΔV _k ≦ V max _k −V _{o, k} (39) Here, Q = phase modifying equipment capacity: control variable Qmin = lower limit value of phase modifying equipment capacity Qmax = upper limit value of phase modifying equipment capacity n: node where the phase modifying equipment is installed.

(Other Embodiment 4) The obtained load switching amount and power generation adjustment amount are presented to the operator via the man-machine interface device without performing load switching or power generation adjustment. Then, the operator can use this as a reference and issue an adjustment command to improve the voltage stability of the power system.

(Other Embodiment 5) Various sensitivity coefficients for the voltage stability index S, that is, the voltage stability sensitivity coefficient A
_j = dS / dL _j , A _m = dS / dG _m , A _n = dS /
dQ _n can also be used as an index of voltage stability. This index shows not the stability of the entire power system but the extent to which the voltage stability of the entire power system changes due to the adjustment of the adjusting device. A node with poor voltage stability has a large absolute value and a good node has a small absolute value. Therefore, by presenting this value to the operator, the operator can know the region where the voltage stability is poor, and can perform appropriate system operation in consideration of the regionality of the voltage stability.

(Other Embodiment 6) In all of the above embodiments, the determinant of the Jacobian matrix or other values may be used as the voltage stability index instead of the sum S of the slopes of the PV curve. Similarly, the voltage stability of the power system can be improved.

[0044]

As described above, according to the present invention, it is possible to improve the voltage stability by controlling load switching, power generation adjustment, and system operation. Furthermore, the voltage stability can be improved by controlling the load switching, the power generation adjustment, and the grid operation while making full use of the performance of the phase adjusting device. In particular, when economic activity is booming and demand increases more rapidly than expected and delays in the installation of power transmission and transformation equipment, the present invention improves voltage stability by controlling load switching, power generation adjustment, and grid operation. Since it can be improved, the effect of the present invention becomes remarkable.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration example of an apparatus according to the present invention.

FIG. 2 is a flow chart showing a processing means according to the present invention.

FIG. 3 is a diagram showing a demand P-voltage V curve and a reciprocal 1 / S curve of the demand P-sensitivity coefficient.

FIG. 4 is a diagram for explaining an example of load switching (load transfer) according to the present invention.

[Explanation of symbols]

4 ... Computer 5 ... Man-machine interface device 21 ... State variable initialization 22 ... Stability index initial value 23 ... Stability sensitivity coefficient calculation 24 ... State variable correction 25 ... Voltage stability sensitivity coefficient calculation 26 ... Load switching amount calculation 27 … Calculation of stability index

Claims (5)

[Claims] 1. A voltage stability monitoring control device for monitoring or monitoring control of voltage stability of a power system, wherein at least one of a load switching amount and a generator output adjustment amount for improving a voltage stability index is obtained. A voltage stability monitoring control device characterized by the above. 2. The voltage stability monitoring control device according to claim 1, further comprising a phasing device connected to the power system. 3. The voltage stability monitoring control device according to claim 1 or 2, wherein any one of load switching, generator output adjustment, and phase adjusting device adjustment is performed. 4. The load change amount, the power generation adjustment amount, and the adjustment amount of the phase adjusting device are man-machined without performing adjustment, control, or system operation.
3. The voltage stability monitoring control device according to claim 1, wherein the voltage stability monitoring control device outputs the voltage stability to the interface device. 5. The voltage stability monitoring control device according to claim 1, wherein a sensitivity coefficient for the voltage stability index is presented to the operator.