JPS60255019A - System stabilizer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is based on the present invention, when a local system that is connected to a power plant is separated from the main system due to a route break, etc. The present invention relates to a large-system stabilization device that adds up the amount of load that is dropped, thereby making it possible to control the supply and demand balance with an even higher yn4i.

Conventionally, a one-frequency drop relay TJFR has been a typical example of this type of device. This detects the frequency drop caused by the unbalance of supply and demand in the separated yen-cal system, and outputs a load cutoff command when the drop value and duration satisfy a certain set value. 1 minute # This is a device that balances supply and demand within the grid. A stabilizing device using this device had the following problems.

1) When the local system is separated from the main system.

In systems with many constant impedance loads, the frequency does not necessarily decrease. Therefore, there is a risk that the frequency will drop, the Ray UFR will not operate, the voltage drop time due to supply and demand imbalance will be prolonged, and the amount of induction motor loads etc. that will fall off will increase.

11) Since the frequency reduction relay IJFR is installed for each load individually, the accuracy of the control finish is only 1, which is not high considering point 1 of adjusting the supply and demand balance of the entire local/l' system.

There was also a separate system stabilization device that applied a microprocessor to solve the drawbacks of the frequency reduction relay UFH such as the Itto 1 or higher. The conventional system stabilizer is shown in Figure 1. In fig.

1 is a substation that belongs to the main system side, 2 is a substation that is the center of the local system to be separated, and 3 is a power station that also belongs to the local system, and 5 is connected by transmission lines 4 and 5, respectively. The system stabilizing device 6 is installed in the substation 2 and includes one manual conversion circuit 61a, 61b, a route disconnection detection circuit 62. Arithmetic processing device 63 using a microprocessor. Stopper 6
4. It is composed of an output circuit 65 and the like.

Next, this operation will be explained. The current and voltage data detected by the sensors 23 and 24, which are composed of current transformers C and T and voltage compensators P and T, are always sent to the grid stabilization device 6 at 9 o'clock via control cables 25 and 27. is input. Based on this data, a filter circuit that removes harmonics, an active power converter that calculates active power,
Input conversion circuits 61a, 61 configured with analog/digital conversion circuits etc. that convert analog quantities into digital quantities.
b calculates the active power flow P5 supplied from the main system and the active power of the load to be cut off, converts this into a digital quantity, and then outputs it to the arithmetic processing unit 63. If we look at line losses, the shortfall in power generation within the local system when system separation occurs is due to the active power flow P8. that was supplied from the main system one day before separation. Therefore, the arithmetic processing unit 63 selects the load to be actually cut off from among the loads to be cut off so that it becomes approximately equal to PH1, and stores it as a control image. This control image is updated at a certain time period. If the route disconnection detection circuit 62 detects the occurrence of route disconnection from the information on the circuit breaker 11 and the circuit breaker 12 sent via the control cape/I/26 and the communication route 12, this control image is Output.

Give a trip command to the breaker 22 of the load to be cut off,
Perform load shedding as required. At this time, the trip signal is transmitted along the trip route 66. '! 7'
(1 Normally, this trip signal is detected by the /I/- disconnection detector 62
The output circuit 65 calculates the AND of the blade output signal of the stopper 64 and the blade output signal of the stopper 64, and the output signal is output only when the output signal becomes 111.

If such a system using a microprocessor is used, will it be possible to solve the drawbacks of the one-type frequency reduction relay described above?Are there any major problems with the conventional microprocessor system due to the first-order process?

In the system shown in Figure 1, a short circuit accident occurred on transmission line 4.
Let's assume that this is the trigger that causes the route to break. At this time, the load voltage ■L (assumed to be an effective value) changes as shown in FIG. In other words, the steady state voltage value VI, o
If expressed in the C10 system.

is tt'ip, u) to vLt'!
The IC terminal fault was cleared (transmission line tripped).
Even after the load cutoff is executed, the voltage drop caused by one power generation cycle continues. The voltage drop VL2 due to this insufficient amount of power generation is normally 0.5 to 0.6 p, u, and becomes very low under single load. It is generally known that when the load voltage decreases in this way, the load of the induction machine, computer, etc. may drop.

Conventional grid stabilization devices do not take into account the amount of load drop due to this voltage drop, and when this occurs, (
This resulted in fractional control. In particular, if there was a large amount of falling power, one generator would accelerate due to oversupply, leading to a trip, and there was a risk that the entire local system would collapse.

The present invention was made in order to solve the problems of the conventional method as described above.We developed a method for estimating the amount of load drop due to voltage drop using limited online data, and applied this to the control algorithm. By doing so, the purpose is to enable highly accurate supply and demand balance control and to provide a 7c system stabilizing device.

The basic principle and embodiments of the present invention will be explained below.

It is assumed that all voltage, power, etc. are expressed using the unit system.

First, a method for estimating the amount of load drop will be explained. The method used here is to eliminate load drop due to voltage drop.

Based on the sampling data of the generator output and the load voltage after the voltage has been brought around the steady value (1p, u), we have designed the load shutoff so quietly that it will not result in overcontrol even if this occurs. By solving simple simultaneous equations, the voltage characteristics of the load are added together, and based on this, the total amount of load shedding, that is, the sum of the amount of shedding due to the voltage drop IC and the control voltage V:, the amount of voltage drop due to the voltage drop is estimated. It is something to do. FIG. 3 shows a conceptual diagram of this load dropout amount estimation method. Also, this method.

1) Load drop does not occur after the voltage returns to around its normal value.

i+) The line loss in the local system is so small that it can be seen, and the output of one generator is determined by the load.

The basic idea is that. I will briefly explain the specific method of developing power. Note that it is assumed here that the frequency characteristics of the load can be ignored.

Generally, when the total load is PL, its voltage characteristics can be expressed by the following equation.

pL=pLP+pLI”vL+pLZ”vL” ・・−
ftl Here, VL represents the load voltage, FLY represents the constant power component of the load, PLI represents the constant current component of the load, and PLZ represents the leg impedance component of the load. Separation occurs within the local system at every instant.

p b=p G (2) holds true. Here, pG is the total power output of the generator in the local system KR'''f.
If sampling data of the load voltage VI, (!-generator output PG) at t+h and t+2h is obtained and the hole is
The following equation is obtained. (H represents sampling, and the subscript S represents sampling data. Expression (3) is PL
If it is regarded as a simultaneous equation regarding P, PL, and PLz, the seven MPLP, PI, and Z can be obtained by formulating the following equation.

As sampling data of the large load voltage vL1 generator output PG, use the data after the voltage has recovered to around its normal value as shown in Figure 2. The amount is (PLF+PLI+PLZ).

It means the amount of load remaining in the local grid. Because (residual load amount) = P:c,” (V:co)=”
L'+PLI"vI+O+PLZ"・■Lo2Pdro
p=(total load before separation) −(Pr,, p−1−
It can be estimated from PI, engineering + PIIZ)..., (7). Using this, the final stage control amount (load interception) POTIR is PCTER-7 (
The active power supplied from the main system before separation) is determined by -Pdrop (8). Briefly, a system stabilizing device incorporating the load drop amount estimation method according to an embodiment of the present invention is shown in FIG. 4, and will be explained in the same manner as in FIG. 1.

In FIG. 4, the numbers 1, 2, 3, 4, and 5 are the same as in FIG.

Since 62.63 and 64.65 are the same as in FIG. 1, detailed explanation will be omitted. In this embodiment, in addition to this, an input transfer circuit 61C1 for i-generator output and an input conversion circuit 67 for load voltage are added in the system stabilizing device 6. This operation will be explained below.

The current and voltage data detected by the sensors 23, 24 and 32, which are composed of current transformers C, T, voltage booster P, and T, are transmitted via control cables 25, 27 and communication route 33. It is constantly input to the system stabilizing device 6.

Based on this data, it consists of a filter circuit that removes harmonics and transient vibration components, an active power converter that calculates active power, and an analog/digital conversion circuit that converts analog quantities into digital quantities. Input conversion corridor 61a, 6
1b and 61c calculate the active power side mP8, L supplied from the main system, the active power component of the load to be cut off, and the generator output (effective component), convert this into a digital quantity, and then perform calculations. It is output to the processing device 63.

The load voltage VL detected by the sensor °28 consisting of 'f7'e, instrument transformers P and T is also input converted by a filter circuit, analog/digital/I'i conversion circuit, etc. After being converted into a digital quantity by the circuit 67, it is output to the arithmetic processing unit 63. - Information on the breaker 11 and the breaker':'j〒 sent via the sword, control cable 26, and communication route 12 is also converted into digital information by the route disconnection detection circuit 62, and then sent to the arithmetic processing unit. 63. Using these data, the arithmetic processing unit 63 executes stabilization control according to the flowchart shown in FIG. 5 when a route break occurs and the local system becomes isolated.

In FIG. 5, 100 is an arithmetic processing block that sets the load voltage VL as a reference, and 102 is the load blocking block P at the final stage (
8) The arithmetic processing block ter which determines the equation, 103 is a processing block which executes the load interruption of this load interruption P. Furthermore, 104 is a processing block that executes the first stage load cutoff Pc(i), and 105 is a block that compares the load voltage VL and the reference value (2). In this case, the reference value ref is a value of about 0.8 to 0.9 p, u, which is close to a steady value, assuming that load drop will not occur if the voltage increases above this reference value. The first stage load cutoff P c (i) is set to a modest amount that will not cause overcontrol even if load drop occurs due to voltage drop. Furthermore, the final stage load cut-off Pcter of the processing block 102 is given by p ``''Pg-Pdr, p ter .

Although the above embodiment is applied to a one-machine, one-substation system, it can also be applied to a multi-machine, multi-substation system.

Total output of the generator, load voltage vL as generator output PG
A similar effect can be obtained by using the average voltage of each substation or the voltage of a representative substation with a large capacity as . In addition to the method of solving simultaneous equations, possible methods for estimating the amount of load shedding include the least squares method, the weighted least squares method, and the exponential smoothing method.

As described above, according to the grid safety electrification system of the present invention, it is possible to estimate the amount of load shedding using the limited data of generator output pG and load voltage L, so with a relatively simple system configuration, A system stabilizing device that can control the supply and demand balance of a separated system with high precision can be obtained.

[Brief explanation of the drawing]

Figure 1 is a system configuration diagram of a conventional system stabilization device using a microprocessor, and Figure 2 is an effective value voltage waveform diagram of a local system in the system shown in Figure 1. 3 is a conceptual explanatory diagram of the load drop amount estimation method which is the basic principle of the present invention, FIG. Figure 3 shows a control flow diagram of the embodiment. 1... Main system substation, 2... Local system substation. 3... Local grid power plant, 4, 5... Power transmission line, 6
...System stabilizer, 61 a p 6 l b +
61 c... Input conversion circuit, 62... Route disconnection detection circuit, 63... Arithmetic processing unit, 64... Stopper, 65... Blade circuit, 67... Input conversion circuit. In Figure 1, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] In a system stabilization device that performs load cutoff to prevent overcontrol even if load drop occurs due to voltage drop in the local system when a 7C four-cal system connected to a power plant and a load is separated from the main system area. , the load voltage of the local system is increased to around the steady value, and then the remaining load amount is calculated based on the generator blade data and load voltage data sampled online, and the entire load is dropped based on the above remaining load amount. A system stabilizing device characterized in that it obtains an estimated amount of load, adds a load to a final stage, and adds an amount of interruption.