JP2002010491A - Voltage stabilizer control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a voltage stabilizer control method which can assure low cost and high control precision. SOLUTION: The capacities, required to cutoff the load and power capacitor, are determined within the target range in advance, in preparation at interruption time of transmission lines. In step 21 to 25, a load bus voltage VL and load power PL are checked if they are within the target range. If they are not, the require capacities for cutting off the load and power capacitor are newly calculated, so that they are within the target range in step 26 to 34. In case the transmission lines are interrupted, the cut off operation is carried out, on the basis of the result thus calculated in advance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage stabilization control method for maintaining voltage stability when a transmission line is cut off in a power system.

[0002]

2. Description of the Related Art Conventionally, as measures to solve the voltage stability problem of a power system, 1) additional transmission lines 2) introduction of a static var compensator (SVC) and a static var generator (SVG). 3) Expansion of phase adjustment equipment 4) Introduction of overload relay. FIG. 7 is a model system diagram of a system in which an overload relay device is installed. In the figure, 1 is an overload relay device, 2 is an infinite bus, 4 is a load bus, 3 is an infinite bus 2 and a load bus. 4 is a transmission line to connect 4 and 5 is a load bus 4
, 6 is a power capacitor which is a phase adjusting device connected to the load bus, and 7 is a sensor for measuring voltage data and current data of the transmission line 3 and the load bus 4.

Next, the operation will be described. The overload relay device 1 constantly measures line voltage data and current data of the transmission line 3 and a circuit breaker signal of the load 5, and when the overload of the transmission line 3 is detected, the circuit breaker of the load 5 (see FIG. (Not shown).

Hereinafter, a description will be given of a process of calculating a power flow in a transmission line for detecting an overload of the transmission line 3. Pe (t) = {v (t) .i (t) + v (t-90}). I (t-90}) / 2 (1) where v (t), i (t) : Current sampling voltage, current instantaneous value v (t-90 °), i (t-90
゜): Instantaneous value of sampling voltage and current 90 ° before electrical angle The moving average processing is performed on the line power flow calculated by the equation (1) as in the following equation. P (t) = {Pe (t) + Pe (t−90 °) + Pe (t−180 °) + Pe (t−270 °)} / 4 (2)

When the moving average power flow P (t) of the transmission line calculated by the equation (2) exceeds a preset threshold value, a cutoff command is output to the circuit breaker of the load 5.

[0006]

Regarding the conventional measures against the voltage stability problem, 1) the equipment cost is high for the addition of transmission lines, the introduction of SVC (or SVG), and the addition of phase adjustment equipment. 2) An overload relay can be introduced at low cost, but in a system where a voltage problem actually occurs,
Since it is expected that a considerable amount of phase adjustment equipment (power capacitors) has already been installed, the overload relay method, which determines the amount of load shedding only by the magnitude of the transmission line power flow, requires a reverse Overvoltage may occur. There was such a problem.

The present invention has been made to solve the above-mentioned problems, and has a lower cost and a lower cost than conventional measures.
It is another object of the present invention to provide a voltage stabilization control method capable of ensuring equal or higher control accuracy.

[0008]

According to a first aspect of the present invention, there is provided a voltage stabilization control method, comprising: a load shedding amount and a power capacitor required to keep an operation point of a system within a target operation range when a transmission line of a power system is cut off. The interruption amount is calculated in advance, and when the transmission line is disconnected, the load stability and the power capacitor interruption are performed based on the result of the preliminary calculation, thereby maintaining the voltage stability.

In the voltage stabilization control method according to a second aspect, a load shedding amount required to keep an operation point of a system within a target operation range when a transmission line of a power system is cut off is calculated in advance,
When a transmission line disconnection occurs, voltage stability is maintained by performing load shedding based on a pre-calculation result.

According to a third aspect of the present invention, there is provided a voltage stabilization control method, comprising: a load interrupting amount, a power capacitor interrupting amount, and a shunt reactor required to keep an operating point of a power system within a target operating range when a power transmission line of a power system is disconnected. Calculate the input amount in advance,
When a transmission line disconnection occurs, the load stability, the power capacitor disconnection, and the shunt reactor injection are performed based on the pre-calculation result, thereby maintaining the voltage stability.

According to a fourth aspect of the present invention, there is provided a voltage stabilization control method according to any one of the first to third aspects.
The priority order of load shedding is set in the order of smaller control amount. According to a fifth aspect of the present invention, in the voltage stabilization control method according to any one of the first to third aspects, the priority order of load shedding is set in order of decreasing importance.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 The arrangement of the voltage stabilizing relay device for carrying out the voltage stabilizing control method according to the first embodiment is shown in FIG. 7 as in the case of the conventional overload relay. FIG. 7 is a model system diagram common to the prior art and this embodiment. The voltage stabilizing relay device 1 constantly measures line voltage data and current data of the transmission line 3, a circuit breaker signal of the load 5, and a circuit breaker signal of the power capacitor 6 which is a phase adjustment facility.

The operation of the voltage stabilization control when another transmission line (not shown) breaks the transmission line will be described below. FIG. 1 is a control flow diagram of a pre-computation part.
According to the flow shown in (1), the amount of load shedding and the amount of phase adjustment equipment (power capacitor) interruption required to keep the operating point of the system on the PV curve within the target operating range when the power transmission line is cut off are periodically changed. Calculate in advance.

First, in step 11, self-end information is collected by measurement of the voltage stabilizing relay device 1. Next, in the creation of the control table in step 12, all the cutoff patterns of the load to be controlled and the phase adjustment equipment (power capacitor) are calculated, and these are arranged in ascending order of control amount. The X _L calculated in step 13 to determine the line equivalent reactance X _L when the transmission line disconnection.

In the control amount calculation calculation in step 14, the load shedding amount and the phase adjustment equipment (electric power capacitor) required to keep the operating point of the system within the target operation range on the PV curve when the transmission line is cut off. Calculate the amount of interruption. FIG. 2 shows a PV curve and a target operation range assumed in this calculation. In the figure, the arrows attached to the black circles indicate the moving directions due to the respective interruptions. Here, P _L is the load amount (however, effective portion), V _L
Is the load bus voltage, _VLmax and _VLmin are the upper and lower limits of the allowable voltage, _PLmax is the maximum load, and K is a coefficient for margin.

Hereinafter, a method of calculating the cutoff amount will be described. In the model system shown in FIG. 3, the load bus voltage _VL is given by the following equation. ^{_{V L 2 = V O 2 +}} (V O 4 -4P L 2 X L 2 (1 + BX L) 2) 1/2) / (2 (1 + BX L) 2) ··· (3) However, V _O is infinite Large bus voltage, B = B _L -B _C , B _L and B
_C is the susceptance of the load 5 and the power capacitor 6. The reactive component power amount Q _L is the load in FIG. 3, j is an imaginary unit. If this voltage value is not given ((V
^{_{O 4 -4P L 2 X L 2}} (1 + BX L) 2) < 0), it can be said that the voltage unstable. On the other hand, the maximum load amount P _Lmax ( _PV
The tip of the curve) is given by the following equation. P _Lmax = V _O ² / (2 (1 + BX _L ) X _L ) (4)

Based on the above equation, the target operation range on the PV curve is set as follows. -Voltage stability can be maintained. -The load bus voltage _VL satisfies the condition of the following formula. _{V Lmin <V L <V Lmax} ··· (5) · Voltage load P _Lmax in stability limit (the tip of the P-V curve) with respect to the load amount P _L after blocking satisfies the conditions of the following equation. P _L × K ≦ P _Lmax (6)

FIG. 4 shows a flow relating to the above-described method for calculating the cutoff amount. Step 21 The load bus voltage _VL when the transmission line is disconnected is calculated based on the equation (3). Step 22 If a real number solution is obtained at the time of calculating _{VL in} step 21, the process proceeds to step 23. If not, it is determined that the voltage is unstable, and the process proceeds to step 26. Step 23 If _VL is equal to or higher than the allowable voltage lower limit _VLmin , step 24
If it is less than the lower limit value, it is determined that there is an undervoltage and step 2
Proceed to 6. Step 24 The maximum load amount P _Lmax when the transmission line is disconnected is calculated based on the equation (4). Step 25 If the value obtained by multiplying the load amount P _L by the coefficient K for the margin is equal to or less than P _Lmax , it is determined that the control is not necessary, and the processing ends _.
Is exceeded, it is determined that there is a possibility of voltage instability, and the routine proceeds to step 26. Step 26 Assuming combinations of all controllable load feeders, according to the control table created in step 12 of FIG. 1, the priority of interruption is set in ascending order of the control amount. According to step 27 the set control amount, first load P _L for the active component and reactive component after the control for the case of the controlled variable minimum, and calculates the Q _L. Steps 28 to 32 The same as steps 21 to 25. If there is a problem with the set control amount, the process returns to step 26, and a pattern with the next smaller control amount is set again. If there is no problem, go to step 33. Step 33 If the load bus voltage _VL after the control is performed is equal to or lower than the allowable voltage upper limit _VLmax , the load interruption target is determined as having no problem with the control pattern assumed at present, and the processing is ended. If it is larger than the upper limit, the process proceeds to step 34. Step 34 Returning to step 28, the operation is repeated, assuming that a part of the phase adjustment equipment (power capacitor) that has been turned on is cut off.

FIG. 5 is a control flow chart of the post-calculation part. When the transmission line disconnection actually occurs, the load disconnection and the phase adjustment equipment (power capacitor) disconnection are simultaneously performed based on the pre-computed result shown above according to the flow shown in FIG. 5 (step 41).

In the above description, in step 12 of FIG. 1, the priority of the interruption of the load to be controlled is set in ascending order of the control amount, but the importance is designated in advance for the load.
FIG. 4 shows that the priority order of the cutoff is determined in ascending order of importance.
In step 26, control (blocking) may be performed in ascending order of importance.

In order to confirm the validity of this control method, FIG.
A simulation study was conducted on the model system shown in Fig. 1. As a precondition for the simulation, the state before the transmission line was cut was as follows. P _L = 0.600 [pu], Q _L = 0.200 [pu] P _Lmax / K after transmission line disconnection was set to 0.4, and the allowable voltage range was set to 0.95 to 1.05 [pu]. The control amount calculation result is as follows, and the process until this result is obtained is shown in FIG.
Shown in In the figure, the values fell within the allowable range from the right through the intermediate results indicated by the points on the polygonal line. Load interruption amount: 0.200 [pu] Phase interruption amount: 0.060 [pu] This is in good agreement with the value separately obtained by the power flow calculation program. It was confirmed that suppression could be performed appropriately.

Embodiment 2 FIG. In the first embodiment, it is assumed that there is a phase adjustment facility (power capacitor) to be interrupted. However, depending on the target system, the phase adjustment facility (power capacitor) is sufficiently provided at the end of the load bus. It may not be installed.

Therefore, even in the case where there is no phase adjustment equipment (power capacitor) to be interrupted, that is, even when only the load interruption is performed, the part for determining the load interruption amount in the first embodiment should be selected and applied. Thereby, control accuracy equal to or higher than that of the conventional overload relay device can be secured. The configuration of the voltage stabilization relay device based on the voltage stabilization control method of the second embodiment is the same as that of the first embodiment.
Similarly, the voltage stabilizing relay device shown in FIG. 7 corresponds to 1 in the figure.

The voltage stabilizing relay device 1 constantly measures the line voltage data and the current data of the transmission line 2 and the circuit breaker signal of the load 5, and transmits the signal according to the flow shown in FIG. The amount of load shedding required to keep the operating point of the system on the PV curve within the target operating range when the electric wire is disconnected is calculated in advance at regular intervals. In the control table calculation and the control amount calculation calculation in FIG. 1, only the load is set as a control target, and the cutoff pattern is determined. Then, when a transmission line disconnection occurs, the load is interrupted based on the pre-computed result according to the flow shown in FIG.

Embodiment 3 In the first embodiment, it is assumed that a power capacitor is present as the phase control equipment to be interrupted. However, depending on the target system, in addition to the power capacitor to be interrupted, The target shunt reactor may be installed.

Therefore, when both a power capacitor and a shunt reactor are present as phase adjusting equipment, the input of a shunt reactor is added to the load cutoff and the power capacitor cutoff which are the control targets of the first embodiment. As a result, the assumed control target range can be made larger. The configuration of the voltage stabilization relay device based on the voltage stabilization control method of the third embodiment is shown in FIG. 7 similarly to the first embodiment, and the voltage stabilization relay device corresponds to 1 in the figure.

The voltage stabilizing relay device 1 constantly measures line voltage data and current data of the transmission line 2, a circuit breaker signal of the load 5, and a circuit breaker signal of the phase adjustment equipment (power capacitor and shunt reactor). As in the first embodiment, FIG.
According to the flow shown in (1), when the transmission line is disconnected, the load shedding amount and the phase adjustment equipment (power capacitor) interruption amount and the phase adjustment equipment (electric power capacitor) required for the operating point of the system to fall within the target operation range on the PV curve. The shunt reactor) input amount is calculated in advance at a constant cycle. In the control table calculation and the control amount calculation calculation in FIG. 1, the load, the power capacitor, and the shunt reactor are set as control targets, and the cutoff and closing patterns are determined. Then, when a transmission line disconnection occurs, according to the flow shown in FIG. 5, based on the result of the pre-calculation, the load is cut off, the phase adjustment equipment (power capacitor) is cut off, and the phase adjustment equipment (shunt reactor) is turned on.

[0028]

According to the voltage stabilization control method of the first aspect, the load interruption amount and the power capacitor interruption amount required to keep the operating point of the system within the target operation range are calculated in advance. Therefore, good control accuracy at the time of transmission line disconnection can be realized at low cost.

According to the voltage stabilization control method of the second aspect, since the load shedding amount is calculated in advance, even when the control target is only the load, good control accuracy at the time of transmission line disconnection can be achieved at low cost. realizable.

According to the voltage stabilization control method of the third aspect, since the shunt reactor is controlled in addition to the load and the power capacitor, it is possible to cope with a case where the voltage stability becomes more severe. .

According to the voltage stabilization control method according to the fourth aspect, the load is interrupted in the order of the smaller control amount, so that the load can be kept within the target operation range with as little load interruption as possible. According to the voltage stabilization control method according to the fifth aspect, since the load shedding is performed in the descending order of importance, the influence of the load shedding can be reduced.

[Brief description of the drawings]

FIG. 1 is a control flow chart of a pre-computation part according to Embodiments 1 to 3 of the present invention.

FIG. 2 is a diagram illustrating a relationship between a P-IV voltage and a target operation range assumed in the voltage stabilization control method according to the first embodiment of the present invention.

FIG. 3 is a model system diagram assumed in a voltage stabilization control method according to the first embodiment of the present invention.

FIG. 4 is a flowchart for calculating a cutoff amount in a pre-calculation part according to Embodiment 1 of the present invention;

FIG. 5 is a control flow diagram of a post-calculation part according to the first to third embodiments of the present invention.

FIG. 6 is an explanatory diagram showing a simulation result of the voltage stabilization control method according to the first embodiment of the present invention.

FIG. 7 is a model system diagram common to the related art and the first embodiment of the present invention.

[Explanation of symbols]

3 transmission line, 4 load bus, 5 load, 6 power capacitor, V _L load bus voltage, P _L load (active ingredient), Q _L load (reactive component), X _L line equivalent reactance.

Claims (5)

[Claims] When the transmission line of a power system is cut off, a load interruption amount and a power capacitor interruption amount required to keep an operation point of the system within a target operation range are calculated in advance, and a transmission line interruption occurs. A voltage stabilization control method characterized by maintaining a voltage stability by performing a load cutoff and a power capacitor cutoff based on a pre-calculation result. 2. An amount of load shedding required to keep an operating point of a system within a target operation range when a transmission line of a power system is cut off is calculated in advance. A voltage stabilization control method characterized by maintaining voltage stability by performing load shedding based on the load stabilization control. 3. A load interrupting amount, a power capacitor interrupting amount, and a shunt reactor input amount necessary to keep an operating point of the system within a target operating range when a power line of a power system is cut off are calculated in advance, A voltage stabilization control method comprising maintaining a voltage stability by performing a load cutoff, a power capacitor cutoff, and a shunt reactor supply based on a pre-calculation result when a transmission line disconnection occurs. 4. The voltage stabilization control method according to claim 1, wherein the priority order of the load shedding is set in an order of a smaller control amount. 5. The voltage stabilization control method according to claim 1, wherein the load shedding is prioritized in the order of decreasing importance.