JPH02197217A - System stabilization device - Google Patents

Abstract

PURPOSE:To obtain highly precise demand and supply balance control by calculating an estimated value of a residual load after the recovery of voltage from the detection data of load active power and load voltage before and immediately after the voltage drop and after the recovery of voltage, by finding an estimated amount of load dropout amount and by deciding the load interruption control amount at the final stage. CONSTITUTION:Current and voltage data detected by sensors 23 and 24 is inputted into a system stabilization device 6, from which active power load-flow Ps and load active power portion are calculated and the data is sent to an arithmetic processing device 63. The load voltage detected by a denser 28 and the information on the circuit breakers 21 and 11 sent through a control cable 26 and a communication channel 12 are also sent to the device 63, with which an estimated value of the residual load after the recovery of voltage is calculated and the total dropout amount of the load is calculated. The load interruption control amount at the final stage can thereby be decided, so that the demand and supply balance control with high precision can be obtained.

Description

[Detailed description of the invention] [Industrial application field]

The present invention estimates the amount of load that will be dropped due to a voltage drop caused by the accident or insufficient power generation when a local system that connects a power plant and loads is separated from the main system due to a route cut accident, etc. The present invention also relates to a system stabilizing device that enables highly accurate supply and demand balance control.

[Conventional technology]

Conventionally, as a typical example of this type of system stabilization device,
There was a frequency reduction relay UFR. This system detects the frequency drop caused by the imbalance of supply and demand in the isolated local grid, and when the drop value and duration satisfy a certain set value, it outputs a command to cut off the load and It is a device that balances supply and demand. A stabilizing device using this device had the following problems. i) When the local system is separated from the main system, the frequency does not necessarily decrease in systems with many constant impedance loads. Therefore, the frequency reduction relay U
If the FR does not operate, the voltage drop due to the imbalance between supply and demand will be prolonged, and there is a risk that the loss of the induction motor load will increase. ii) Since the frequency reduction relay UFR is installed for each load individually, the accuracy of the control is not very high from the point of view of adjusting the supply and demand balance of the entire local system. On the other hand, a separate system stabilizing device using a microprocessor has been developed to solve the above-mentioned drawbacks of the frequency reduction relay UFR. FIG. 4 shows a configuration diagram of this system stabilizing device. In the figure, 1 is a substation that belongs to the main system, 2 is a substation that is the center of the local system to be separated, and 3 is a substation that belongs to the local system to be separated, and the generator 3
1 power plant, each connected by 4.5 transmission lines. The system stabilizing device 6 is installed in the substation 2, and is composed of an input conversion circuit 612.61b, a route disconnection detection circuit 62, an arithmetic processing device 63 using a microprocessor, a stopper 64, an output circuit 65, etc. . Also, L.D.
, indicates a non-shutoff target load group, and LDI indicates a cutoff target load group. Next, the operation of such a conventional system stabilizing device will be explained. Current transformers C, T and potential transformer P. The current and voltage data detected by the sensors 23 and 24 composed of T are sent to the control cable 25.2.
7, it is constantly input to the system stabilizing device 6. Based on these detection data, an input conversion circuit 613 is composed of a filter circuit that removes harmonic components, an active power converter that calculates active power, an analog/digital conversion circuit that converts an analog quantity into a digital quantity, etc. .61b is
The active power flow P5 supplied from the main system and the active power of the load to be cut off LDl are calculated, converted into digital quantities, and then output to the arithmetic processing unit 63. If line loss is ignored, the shortfall in power generation in the local system at the time of system separation is equal to the active power flow Ps that was being supplied from the main system before separation, so the arithmetic processing unit 63 4. Select the load that should actually be cut off from among the loads to be cut off so that it is almost equal to the main system active power flow P3, and write it down as a control image. Save money. This control image is updated at a certain time period. And control cable 26 and communication route 1
breaker 21 and breaker 11 sent through 2
When the route disconnection detection circuit 62 detects the occurrence of a route disconnection based on the information, it outputs this control image, gives a trip command to the breaker 22 of the load to be shut off LI)+, and executes a predetermined load shedding. At this time, the trip signal is
It is transmitted by trip route 66. In addition, normally this trip signal is output from the route disconnection detection output and the stopper 6.
The logical product of the four outputs is taken in the output circuit 65, and the output signal is output only when this output signal becomes "1".

[Problem to be solved by the invention]

Since the conventional system stabilizing device is configured as described above, it can solve the drawbacks of the one-type frequency lowering relay described above, but it has the following major problems. That is, in the system shown in Fig. 4, if a short circuit accident occurs in the transmission line 4 and this triggers a route break, the effective value load voltage V and the load active power bone PL will be as shown in Fig. 5 a. , changes as shown in b. In other words, the effective value load voltage■. ■ is the voltage value at steady state due to a short circuit accident. (expressed in units, it drops from 1p, u) to Vt, t, and even after the accident is cleared and the transmission line is tripped,
The voltage drop due to insufficient power generation continues for m until load shedding is executed. Reduced voltage value V due to this insufficient amount of power generation
Lf is normally 0.5 to 0.6 p, u, and becomes very low under heavy loads. As shown in Figure 5, the active power of the load P
LO similarly decreases to PLf. It is generally well known that when the load voltage (1) decreases in this way, the load of the induction machine, computer, etc. will drop out. Conventional system stabilization devices do not take into account the amount of load drop due to this voltage drop, and when this occurs, over-control occurs. Particularly when a large amount of electricity falls off, there is a problem in that the generator accelerates due to oversupply, leading to a trip, and the entire local system collapses. The present invention was made in order to solve the above-mentioned problems, and its purpose is to obtain a system stabilization device that enables more accurate supply and demand balance control that takes into account the amount of load drop due to voltage drop. do. [Means for Solving Problem i1] The system stabilizing device according to the present invention includes a load characteristic identification means for identifying load characteristics based on load active power and load voltage before and immediately after voltage drop, and load characteristics identification means for identifying load characteristics by load active power and load voltage before voltage drop and immediately after voltage drop. and an estimating means for estimating the amount of load shedding from the load characteristics determined by the load characteristic identification means using active power and load voltage. This is an addition to the device that controls the supply and demand balance in the local system.

[For use]

The system stabilizing device of the present invention is capable of controlling load active power before voltage drop, load active power immediately after voltage drop, load active power after voltage recovery, load voltage before voltage drop, load voltage immediately after voltage drop, and voltage recovery. The remaining load voltage after voltage recovery is detected, and the predicted value of the remaining load after voltage recovery is calculated based on this detected data. Based on this predicted value of the remaining load, the amount of load drop due to voltage drop is estimated, and the final load is cut off. This determines the control amount.

【Example】

Hereinafter, the basic principle and one embodiment of the present invention will be explained step by step. It is assumed that all voltage, power, etc. are expressed using the unit system. First, a method for estimating the amount of load shedding, which is the basic principle of the present invention, will be explained based on FIG. 2. The method provided here identifies the voltage characteristics of the load using online data of the load's active power (PL) and effective load voltage (vL) before the voltage drop, immediately after the voltage drop, and after recovery, and uses this as a basis for load drop. It estimates the amount. Load active power before voltage drop is PLO1 Load active power immediately after voltage drop is PLf, Load active power after voltage recovery is PL
Set it as O. On the other hand, it is assumed that the load voltage before the drop is VLO, the load voltage immediately after the drop is Vl, f, and the main load voltage after recovery is . FIG. 5 is a waveform diagram showing the relationship between these changes. It is also assumed that load drop due to a voltage drop occurs gradually during the voltage drop, and does not occur after the voltage is restored, as shown by the dotted line in FIG. At this time, if the voltage after recovery is the same as the voltage before dropping, that is, ■Lo=VLp (1), then the load drop amount P drop is
= PLOP Lll (2). However, in general, the voltage after recovery VL1. is the voltage VLO before it drops
Therefore, it is necessary to separate and distinguish between the fluctuation in active power due to the voltage characteristics of the load and the amount of dropout. Therefore, (1) identify the load characteristics from the load active power and load voltage before and immediately after the voltage drop. During this time,
It is assumed that there is no load drop. (2) Load active power Ptp and load voltage after voltage recovery ■1
．． The load drop amount P drop is estimated from the load characteristics obtained in (1) above using By taking these two steps, we take a method of filtering the influence of the voltage characteristics of the load. Specifically, the voltage characteristics of the load are set as shown in FIG. Next, assuming that the value after voltage recovery (Vt+PI-p) satisfies this characteristic, the predicted value of load active power PL when the voltage becomes Vl and Q after recovery is...
(4) It is possible to obtain from From this, the estimated value of the load drop amount P"drop is P" drop = P LO? t.・・・・・・(
5). Therefore, the final stage supply and demand balance control amount (load breaker) Pcter is
ter- (active power supplied from the main system before separation) P"drop ...determined by (6).Next, regarding one embodiment of the present invention, such basic principle is Fig. 1 shows a system stabilizing device that incorporates the load drop amount estimation method.The embodiment shown in Fig. 1 will be explained using the same system as Fig. 4.In the figure, reference numerals 1.
2, 3, and 4.5 are the same or equivalent parts as in FIG. In the grid stabilization system M6 installed at TEPCO 2,
Reference numerals 61a, 61b, 62.63, and 64.65 are the same as in FIG. In this embodiment, in addition to this, an input conversion circuit 67 for load voltage is added within the system stabilizing device 6,
Furthermore, the configuration is such that a sensor 24 for measuring the active power of the load is also installed at each feeder of the load that is not to be shut off. Next, this operation will be explained. Current and voltage data detected by a sensor 23.24 composed of a current transformer C1T and potential transformers P and T are constantly input to the system stabilizing device 6 via a control cable 25.27. Based on these detection data,
The input conversion circuits 61a and 61b are mainly composed of a filter circuit that removes harmonic components and transient vibration components, an active power converter that calculates active power, an analog/digital conversion circuit that converts analog quantities into digital quantities, etc. The active power flow Ps supplied from the grid and the active power flow PL of the load are calculated, converted into digital quantities, and then output to the arithmetic processing unit 63. In addition, the load voltage ■ detected by the sensor 28 composed of the instrument transformers P and T is also converted into a digital quantity by the input conversion circuit 67 composed of a filter circuit, an analog/digital conversion circuit, etc. After that, it is output to the arithmetic processing unit 63. On the other hand, the information on the circuit breaker 21 and the circuit breaker 11 sent via the control cable 26 and the communication route 12 is also converted into digital information by the route disconnection detection circuit 62 and then output to the arithmetic processing unit 63. . Using these detection data, the arithmetic processing unit 63 executes stabilization control according to the flowchart shown in FIG. 3 when a route disconnection occurs and the local system is in isolated operation. In Fig. 3, 100 is a processing block that identifies the load voltage characteristics from the above equation (3), and 101 is a comparison block for comparing the load voltage VL with a reference value Vref. It is assumed that no load drop occurs, and the value is approximately 0.8 to 0.9 p, u, which is close to the steady value. 102 is an arithmetic processing block that calculates the total dropout amount P″drop of the load from the above-mentioned equations (4) and (5), and 103
104 is an arithmetic processing block that calculates the final stage load breaker Pcter from equation (6), and 104 is this breaker P.
This is a processing block that executes load shedding according to cter. In addition, the final stage load cutoff II Pcter is as follows:
Pcter=PsP"drop. On the other hand, 105 is a processing block that executes the first stage load cutoff Pc(i), and after executing this cutoff, the comparison block 106 again compares the load voltage ■1 and It is controlled so that a comparison is made with the reference value V ref.The first stage load cutoff Pc(i) is set to a modest value that does not result in overcontrol even if load drop occurs due to a voltage drop. It is preferable to set the load voltage VL to the average voltage of each substation or A similar effect can be obtained by using the voltage of a representative substation with large capacity.On the other hand, in addition to the method described here, there are other methods for estimating the amount of load drop.
Possible methods include multiplication, weighted least squares, exponential smoothing, and methods for solving simultaneous equations. Further, similar effects can be obtained by using generator output as online data in addition to load active power.

【Effect of the invention】

As described above, according to the system stabilization device of the present invention, it is possible to estimate the amount of load drop from the limited detection data of load active power and load voltage. This has the effect of controlling the supply and demand balance of the separated system.

[Brief explanation of the drawing]

Figure 1 is an overall configuration diagram of a system stabilizing device according to an embodiment of the present invention, Figure 2 is an explanatory diagram of load characteristics when using the method of estimating the amount of load drop, which is the basic principle of the present invention, and Figure 3 is Fig. 1 is a control flow diagram of the embodiment device, Fig. 4 is an overall configuration diagram of a conventional grid stabilizing device using a microprocessor, and Fig. 5 is a diagram showing the local system in the grid stabilizing device of Fig. 4. FIG. 6 is an effective value waveform diagram of load voltage and load active power when separated. 1 is the main system side substation, 2 is the local system substation, 3 is the local system power plant, 4.5 is the transmission line, 1121.23.
24 is a sensor, 12.25, 26° 27.66 is a control cable, 6 is a system stabilizer, 61a, 61b
62 is an input conversion circuit, 62 is a route disconnection detection circuit, 63 is an arithmetic processing unit, 64 is a stopper, 65 is an output circuit, 67 is an input conversion circuit, LD, ! Non-shutoff target load group, LD,
Load group to be cut off. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] In a system stabilization device that controls the supply and demand balance of the local system when the local system that interconnects the power plant and the load is separated from the main system, the load active power before the voltage drop and the load active power immediately after the voltage drop are used. and the load active power after voltage recovery, as well as the load voltage before the voltage drop, the load voltage immediately after the voltage drop, and the load voltage after voltage recovery, the active power portion of the load connected to the local grid, and the online load voltage. The predicted value of the remaining load after voltage recovery is calculated according to the detected data, and the estimated amount of load drop due to voltage drop is obtained based on the predicted value of the remaining load, thereby determining the load shedding control amount for the final stage. Characteristic system stabilization device.