JPS6077632A - 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 provides that a local system interconnecting a power plant and a load,
When the system is separated from the main system due to a route cut accident, etc., the system stabilizes by adding up the amount of load that will fall due to the voltage drop caused by the accident or insufficient power generation, making it possible to control the supply and demand balance with high precision. This relates to a conversion device.

Conventionally, a typical device of this type was the frequency drop relay UFRIJ''.This detects the frequency drop caused by the imbalance of supply and demand in the local grid, and calculates the drop value and group duration time. When a certain differential value is satisfied, a load cutoff command is output to balance supply and demand within the separated system.However, system stabilization devices using such relay devices , there were some problems.

1) The local lineage is separated from the main lineage1. In systems with a large load of foot impedance, the frequency does not necessarily decrease.1. Therefore, the frequency reduction relay UFR does not operate, and the low voltage F time due to the imbalance between supply and demand is prolonged, and there is a risk that the amount of detached loads, etc., will increase.

Since the frequency reduction relay TJ i''R is installed separately in the '1!J load 46 11b, the accuracy of control is not high when looking at the supply and demand balance of the entire local system.

In order to solve the above-mentioned drawbacks of the frequency reduction relay UFH, there is also a separate system stabilizing device using a microprocessor.

FIG. 1 is a block diagram of such a conventional system stabilizing device. In the figure, 1 is a substation for main system side pressure, 2 is a substation that is the center of a separated local system, and 3 is a power station that also belongs to the local system, and is interconnected by transmission lines 4 and 5. ing. 30a is a non-controlled load group, and 30b is a controlled load group. The system stabilization device 6 is installed in the substation 2, and is composed of input conversion circuits 61a and 61b, a route disconnection detection circuit 62, an FC processing device 63 using a microprocessor, a stopper 64, an output circuit 65, etc. ing.

Next, this operation will be explained. Current transformer9. The current and voltage data detected by the sensors 23 and 24 made up of the voltage transformer RT and the voltage transformer are constantly input to the system stabilization device 6 via the control cable 25, 27Y.
ing. Current such as this.

Input conversion circuits 61a and 61b, which are comprised of a filter circuit that removes harmonic components based on voltage data, an active power converter that calculates active power, an analog/digital conversion circuit that converts analog quantities into digital quantities, etc. calculates the active power flow Ps supplied from the main system and the active power of the load to be cut off 30b, converts this f'L into a digital quantity, and outputs it to the arithmetic processing unit 63. If line losses are ignored -tf, then the shortfall in power generation in the local system when main system separation occurs is equal to the effective power flow P8 that was supplied from the main system before separation.tc
.

Therefore, the arithmetic processing unit 63 selects the load to be actually cut off from among the loads to be cut off 30b so as to be approximately equal to this active power flow P8, and stores it as a control image. This control image is cultivated in a certain time period. Then, if the route disconnection detection circuit 62 detects the occurrence of route disconnection from the main system, the opening/closing information of the circuit breaker 11 and the circuit breaker 12 is sent by blowing the control cable 26 and the communication route 12. A control image is output, and a trip command is given to each of the circuit breakers 22 of the load 30b to be cut off to execute a predetermined load cutoff. At this time, the trip signal is transmitted from the output circuit 65 to the corresponding breaker 22 via the trip route 66. Further, normally, this trip signal is outputted only when the output signal of the output signal of the route break detection circuit 62 and the output signal of the stopper 64 is ANDed by the output circuit 65 and becomes '11.

If such a system stabilizing device using a microprocessor is used, the disadvantage II'i of the frequency reduction relay UFR system described above can be solved, but the conventional microprocessor system has the following major problems.

That is, in the system shown in FIG. 1, it is assumed that a short circuit accident occurred in the power transmission line 4, which triggered the disconnection of the route from the main system. At this time, the load voltage indicated by the effective value ■L
As shown in Fig. 2, the voltage value vL0 (expressed in unit system, 1p, 1p,
u) to t. Due to the occurrence of a short circuit accident at the time, Vl, 1
'! load shedding is carried out even after the fault is cleared and the transmission line is tripped at time t1.
After the 2nd point, the voltage continues to drop due to insufficient power generation. The voltage drop VL2 due to the insufficient amount of M is normally 05
~06p, u, which becomes extremely low under heavy loads.

When the load voltage decreases in this way, the induction machine or meter u1-
General VC is not familiar with the fact that the load on the machine etc. has fallen off.
ing. Conventional system stabilization devices do not take into account the amount of load shedding due to this voltage drop, and when this occurs, over-control occurs.Especially when the amount of shedding is If there is a large amount, there will be an oversupply of generators/I[]
There was a fear that this would lead to a trip and the entire local system would be destroyed.

Does the present invention address the above-mentioned problems with conventional products? In order to solve this problem, we applied the weighted least squares method to develop an online data analysis method that limited load removal due to voltage drop, and applied this to the control algorithm. The purpose of this invention is to provide a system stabilizing device that can control the supply and demand balance with high precision.

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

In the following explanation, it is assumed that voltage, power, etc. are all expressed in units.

First, a method for estimating the load drop amount, which is the basic principle of the present invention, will be explained. The estimation method provided here is to reduce the voltage to a normal range (IP-u
) The voltage characteristics of the load are identified by applying the weighted least squares method to the sampling data of the generator output and load voltage after the generator output and load voltage have been restored to around This is to estimate the sum of the amount of shedding due to the control and the amount of shedding due to the control. FIG. 3 shows a simple overview diagram of this estimation method. 1fc
, This method: 1) Load drop does not occur after the voltage has recovered to around its normal value.

11) The loss of line 4n in the local system is as small as possible, and the generator output is determined by the load.

This idea assumes a sword. I will explain the specific old development procedure to the arrow. It is assumed here that the frequency characteristics of the load can be focused.

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

PL=PLP+PI, ■"L+PLZ-vL=-(
tl Here, VL represents the load voltage, PLPra represents the load force component, PLI represents the constant current component of the load, and PL and Z represent the constant impedance component of the load. When separation from the main system occurs, within the local system, P L = PG ... (21) is established at each instant. Here, PG is the total output of the generators belonging to the local system. Therefore, Assuming that n sampling data are obtained for each n of load voltage and generator output t', the following equation holds true.

TPG"' VL TP L -+3, TPG=[PG1PG2...p Gn:] t'PL
=[:PLP PLI PLZ:]. here,
tij transpose. This indicates that data having the same subscript ``f'' is sampled at the same time t''L.

When the weighted least squares method is applied to equation (3), the optimal estimation 111 calendar I of TPL is given by the following equation.

...(4) As each sampling data of the load tEE constituting yL, rpG, and the generator output, time t is used in the system shown in FIG. If we use the sampling data after the voltage has recovered to around its normal value after several load failures or drops at t and 1, we can obtain (PL; +PL from formula 41)
;-+PL;), the optimal estimate II of the remaining load in the local system is . For the number of cases, (optimal estimation of residual load 1@) = PL'
+PLI ten PL; (“VLo=IP-1 Therefore,
The estimated value Pdrop of the total amount of load drop is Pdrop = (Total load no before the break (pL; +p
L amount 10 PL2]... (5) It is possible. Using this, the load interruption Pc, ter as the control variable of the final stage is calculated as follows. , ter-(friend active power Ps supplied from the main system before separation)-Pdr
o'yp...(6) is the answer.

Note that the weighting matrix IR is given by the covariance matrix of the iron law noise, but if rL is unknown, it may be decided to use a different method.

The composition ratios of the load's leg power, constant current, and leg impedance in the pre-caulking local system are known, and the estimation results of each component PLP'1. The old one is selected so that PLI and PLZ can be obtained with values close to this ratio.

FIG. 4 is a configuration diagram showing the configuration of a system stabilizing device according to an embodiment of the present invention incorporating this load drop amount estimation method together with a system. This embodiment will be explained using the same system as in FIG. 1. Note that in FIG. 4, the same reference numerals as those in FIG. 1 indicate the same or corresponding parts, so detailed explanation will be omitted.

Here, unlike the case of FIG. 1, an input conversion circuit 61c for generator output and an input conversion circuit 67 for load voltage are added to the system stabilizing device 6. The operation of this embodiment will be explained below.

The current and voltage data f' detected by the sensors 23, 24 and 32, which are composed of the current flow devices C and T and the instrument pressure generators P and T, are sent to the control cape/I/25.27 and the communication route 33. The signal is constantly input to the system stabilizing device 6 via. Based on these data, it is composed of a filter circuit that removes harmonic components and transient vibration components, an active power converter that derives active power, and an analog/digital conversion circuit that converts analog quantities into digital quantities. input conversion circuit 6'
la, 61b, and 61c calculate the active power flow Ps supplied from the main system, the active power component of the load to be cut off, and the generator output (effective component), and after converting these into digital quantities, the arithmetic processing unit 63 Output to.

17? ：Instrument transformer PT construction configuration
The load voltage VL detected in step 28 is also converted into a digital value by an input conversion circuit 67 consisting of a filter circuit, an analog to digital conversion circuit, etc., and then output to the arithmetic processing unit 63. Ru. -Sword, control cable 2
6 and the breaker 1 sent via the communication route 12
1 and the opening/closing information of the circuit breaker 12 is also transmitted to the route disconnection detection circuit 6.
2 and converted into digital information f'Lyc, which is then output to the arithmetic processing unit 63. Using these takes, when it is detected that a route disconnection occurs in which the main system is separated and the local system becomes isolated, the processing unit 63
executes stabilization control according to the flowchart shown in FIG.

In FIG. 5, 70 is a start block that starts stabilization control after detecting the occurrence of a route break between the main system and local system, and T1 is a start block that detects whether the load voltage VL is greater than the reference value vref. Judgment block 72 is a processing block that selects the first stage load when VL<ref with respect to the load voltage, 73Fi is the i-th stage load cutoff PC
(i) In the processing block to execute ft, this p c (i
) is set to an amount that will not result in overcontrol even if load drop occurs due to voltage drop. T4 also depends on the load voltage VL〉■ref ”Processing block to judge again, T
5 is a processing block for selecting the i-th and eleventh load; 76
is +41, +51 type Eri total load drop amount “d
The processing block T7 that calculates the final stage load cutoff "c, ter" is defined as Pc, ter= in equation (6).
Processing block that calculates from "a" drop, 78 is load cutoff Pc, 8rvc load cutoff? Y is a processing plotter to be executed, and T9 is a control end block. Note that decision block 71. Reference value ■r at T4
ef is a value such that load drop will not occur if the load voltage vL recovers to above this value, and if it is selected to a value of about 0.8 to 0.9 p, u, which is close to a steady state, good.

Since all the load shedding is executed in the order of the controllers J, the supply and demand balance (recovery and maintenance of lances) with high precision can be performed.
can do.

The above example is a case where one machine, one tank is applied to a station system, but even in a multi-machine, multi-station system, PG is the total output of the generator, and VL is the average voltage of the substation or the large capacity. A similar effect can be obtained by using the load voltage of a representative FF power station. 1. In addition to the weighted least squares method, possible methods for estimating the amount of load shedding include the general least squares method, the exponential smoothing method, and the method using simultaneous equations.

As described above, the present invention can be applied to the limited data area of generator output and load voltage to determine the negative stress reduction f4 ignition W, so a relatively single system configuration can be used to separate highly conflicting systems. In addition to being able to control the RA supply balance, there is also the effect that there is no risk of the entire local system being collapsed after separation due to oversupply of generators when there is a large amount of special pressure load dropout.

[Brief explanation of drawings]

Figure 1 is a configuration diagram of a conventional system stabilization device, Figure 2 is a waveform diagram of the load voltage of the local system after separation from the main system, and Figure 3 is a diagram of the load voltage waveform of the local system after separation from the main system.
The figure is a conceptual explanatory diagram of the load drop amount estimation method based on the basic principle of the present invention, Figure 4 is a block diagram of a system stabilizing device according to an embodiment of the present invention, and Figure 5 is a calculation processing unit 6 in the same embodiment.
3 is a processing flow diagram. 1.2... Substation, 3... Power plant, 4, 5... Power transmission line, 6... System stabilizer, 11.21.22...
- Breaker, i2.33...Communication cape, 23.2
4, 28° 32...sensor, 25, 26, 29.・
...Control cable, 30a...Load to be cut off, 30 b--Load to be cut off, 61
a+6 lb+ 61c+67...Input conversion circuit, 62...Route disconnection detection circuit, 63...Arithmetic processing unit, 64...Stopper, 65...Output circuit. In addition, in the figures, the same reference numerals indicate the same or corresponding parts. Agent Masuo Hitoiwa Figure 1 Figure 2 Figure 3 Figure 1 Figure 4 Figure 5 Procedural Amendment 59412 Showa Year Month Day ↑ 1 Palace of the Director General 2 Invention Name System Stabilizer 3, Representative of the person making the amendment To Hitoshi Katayama, Part 5, Detailed explanation of the invention in the specification subject to amendment 6 Contents of the amendment Page 12, lines 19 to 20: ``A break in the route that separates the principal authority has occurred. ," has been amended [due to a route cut accident occurring on the interconnection line with the main grid]. that's all

Claims (1)

[Claims] When the local system that connects the power plant and the load is separated from the main system, the system stabilization device that controls the supply and demand balance of the local system has a load cutoff system that prevents overcontrol even if load drop occurs due to voltage drop. After that, the optimal estimated value of the remaining load is calculated by applying the weighted least squares method to the sampling detected fL generator output data and load voltage data online, and the above remaining load is calculated from the total load amount before separation. A system characterized in that the load interruption of the final stage is calculated from the total load shedding amount estimate obtained by subtracting the optimal estimated value of and is reflected in the local system to control the supply and demand balance of the local system. Stabilizer.