JPS6070929A - Reactive power controller of composite generator plant - 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 Technical Field of the Invention The present invention relates to a reactive power control device for a combined power generation plant that combines a plurality of gas turbines and steam turbines.

[Technical background of the invention and its problems]

A combined power generation plant is one of the things that improves the efficiency of the power generation system as a whole.

In this system, steam is generated by the exhaust gas that drives the gas turbine, and the steam is used to drive the steam turbine. That is, it is a combined power generation plant in which the driving forces of a gas turbine and a steam turbine are combined to turn a generator to generate electricity, and is generally called a combined cycle system.

FIG. 1 shows an example of the configuration of a combined cycle. Gas turbine 1. A steam turbine 21 and a generator 3 are coupled on one shaft, and the output of the generator 3 is boosted by a main transformer 4 and then connected to a system 6 via a breaker 5 . The output of the generator 3 is of a medium or small capacity of about 100 MW, and a plurality of the above systems (about 5 to 10 units) are connected in parallel to form one power generation system.

When a system is configured with multiple generators in this way, there is an advantage that even if one shaft fails, it does not have a large effect on the power generation amount of the entire system. Since it is not possible to increase the number of units, a control device is required to control multiple units together as one system.

One of the control devices is a reactive power control device, and a schematic control block diagram thereof is shown in FIG.

A reactive power command value is generated by an integrator 9 via a change rate limiter 8 from a reactive power increase/decrease command 7 from a central power supply station or a manual switch by an operator. After a limit is applied by the upper and lower limit controller 10 determined by the number of operating units, it is input to the comparator 11 and compared with the value obtained by adding together the reactive power 12 of each axis in the adder 13. Then, the comparator 11 compares the command value and the actual value of reactive power, and only the difference is sent to the distributor 1.
4 to distribute the target value of reactive power to each axis.

The reactive power target value is input to each axis control unit 15, and after being limited by the rate of change limiter 16 and upper and lower limit limiter 17, the comparator 18 compares it with the actual reactive power 19 of the axis being controlled. compare. Then, the difference between the two is inputted to the excitation device 20 of the generator as a reactive power increase/decrease command, and the voltage setter 22 of the automatic voltage regulator 21 (hereinafter referred to as AVR) is increased/decreased based on the reactive power increase/decrease command. A'VR21 is a device that controls the excitation current of the generator and adjusts the terminal voltage of the generator. However, when the generator is connected to the power grid and the grid voltage remains constant +C, the excitation current cannot be adjusted. Increasing it will increase the reactive power, and decreasing the excitation current will decrease the reactive power. That is, A
This means that the VFL 21 can control the increase or decrease of reactive power.

FIG. 3 shows an example of a configuration diagram of an excitation device. This is based on the thyristor direct excitation method. Thyristor direct excitation means, as shown in FIG. 3, that the output voltage of the generator 23 is reduced to an appropriate voltage level by the excitation transformer 24, then rectified by the thyristor bridge 25, and then the field breaker 2
This is an excitation method in which the power is supplied to the field winding 27 through the generator 23, and since the output of the generator 23 is used as an excitation source, no other excitation source is required.

Fi as an excitation device, AVFLzt for adjusting the output voltage of the generator to a certain set value, and this AVR.
A constant excitation regulator (hereinafter referred to as MBC) 28 is used to control the field voltage or field current to a certain set value, and is used in the event of a 2t failure or when starting up a generator. have. When control is performed by the AVR 21, the output voltage of the generator 23 is input to the AVR, 21 via the voltage transformer 29,
The excitation current is controlled by sending a pulse signal to the gate of each thyristor of the thyristor bridge 25 so as to match the setting value of the voltage setting device 22 of FIG.

The output voltage and current of the generator are controlled by each controller 3 for over-excitation, under-excitation, etc. via an instrument transformer 29 or an instrument current transformer 30.
When the excitation amount approaches the stable operation limit of the generator, the limiter 31 sends a signal to AVl (21) to limit the excitation amount and perform control so as not to exceed the stable operation limit. If control is performed by MF3C28, input the field voltage or field current to ME028,
A pulse signal is sent to the gate of each thyristor of the thyristor bridge 25 to control the excitation current so that this value matches the setting value of the voltage setting device 32.

The difference between the control by the AVFL 21 and the control by the MEC 28 is whether the value of the voltage setter 22.32 is compared with the generator terminal voltage or the field voltage and current. When the generator is connected to the grid, if the grid voltage fluctuates, the generator voltage will also fluctuate. At this time AV
When the control is performed using R, the excitation current is controlled in a direction that suppresses voltage fluctuations, thereby improving the stability of the entire system.

On the other hand, if ME028 is used for control, even if the system fluctuates, its own excitation amount will not change, so no improvement in system stability can be expected.

For this reason, normal operation is controlled by FiAVR.

ME02 only when the AVR malfunctions or starts.
An operation is being carried out in which control is performed at 8. In other words, during control by the MEC 28 due to a failure of the AVR 21, the operator monitors conditions such as intermediate supply commands or system status, and manually changes the voltage setting device of the MBC 2B. Since the generators are controlled as if they were one unit, if the AVR of a certain axis fails, it is difficult for the operator to always manually control the voltage setter of the MBC 2B of that axis.

For this reason, conventional reactive power control devices for combined cycles perform control to trip the shaft that has failed due to an AVR failure. Combined cycle is 1 with multiple axes
Since the plant consists of two plants, even if one shaft is tripped, the effect on the whole is smaller than in plants other than combined cycle plants, but if even one shaft is tripped, it will cause considerable disturbance to the system.

[Purpose of the invention]

An object of the present invention is to obtain a reactive power control device for a combined power generation plant that allows an automatic voltage regulator to disconnect a failed shaft without causing disturbance to the power system.
be.

[Summary of the invention]

In order to achieve this objective, in the present invention, the general control unit that distributes the reactive power command value to each axis receives the total value of the reactive power of the axes that are not subjected to excitation control by the automatic voltage regulator from the central power supply point. Alternatively, a function is provided to first subtract from the reactive power command value operated by the operator, and the voltage of the automatic voltage regulator or constant excitation regulator of each axis is set based on the reactive power command value distributed to each axis by the general control unit. Each axis control unit, which controls reactive power by increasing or decreasing the voltage regulator, is equipped with a reactive power setting device specifically designed for when the automatic voltage setting device fails. Switch from the voltage regulator to the constant excitation regulator, control the voltage setter of the constant excitation regulator to match the setting value of the reactive power setter of each axis, and also adjust the load of the axis where the automatic voltage regulator has failed. is characterized in that it is reduced at a constant rate.

[Embodiments of the invention]

The control block diagram of the reactive power control device according to the present invention is shown in FIG.
As shown in the figure. The difference from the one shown in FIG.
4 and the reactive power of the axis that is not in AVR automatic operation is 35
is subtracted from the total value in the adder 36, and the output thereof is input to the change rate limiter 8. That is, the idea is that the reactive power of the axis that is not in AVR automatic operation is subtracted in advance and then used as the reactive power command value.

Next, the output of the upper and lower limit limiter 11 is compared with the value obtained by adding together the reactive power 37 of the shaft during AVR automatic operation in the comparator 11 in the adder 13. This is an AVR.

This is because the reactive power of the axes that are not in automatic operation has already been subtracted, so feedback of reactive power is considered only for the AVR and automatic operation axes. Then, in the distributor 14, the AV
R A target value of reactive power is distributed to each axis during automatic operation and a signal is sent to each axis control unit 15.

Hereinafter, the control for the axes during AVR and automatic operation is the same as that shown in FIG. 2.

AVft21 has failed and the excitation device 20 has stopped operating as ME028.
When the operation shifts to ME028 control due to AVR 21 failure, input the reactive power setter 39 for AVR failure and the actual reactive force 19 of the axis being controlled to the comparator 40, and close when the AVR 21 failure causes ME028 control to occur. The voltage setter 32 of the Mvc 28 is controlled through the contact 41. At the same time, a load reduction command is issued to the load control device to reduce the load on the failed AV LL axis at a rate that does not significantly affect the system. The setting value of the reactive power setting device 39 can be set arbitrarily, but
In accordance with the load drop due to the failure in No. 21, the reactive power should be reduced while maintaining the power factor before the failure, or
Alternatively, reduce the reactive power so that the reactive power becomes zero, that is, the power factor becomes 11. Alternatively, reduce the reactive power while driving it to an arbitrary Var. When the load drops to zero minus α, open the generator breaker, and then open the field breaker. A flow diagram of the above control is shown in FIG.

(Effect of the invention) As described above, when the AVR fails, the excitation control is switched to MBC control at the same time as a load reduction command is issued to the load control device, and the reactive power is also reduced.
It is possible to safely disconnect the shaft in which a failure has occurred from operation, and it is possible to prevent disturbances to the system due to trips.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a combined cycle, Fig. 2 is a control block diagram of a reactive power control device for a combined cycle, Fig. 3 is a block diagram of an excitation device using a thyristor direct excitation method, and Fig. 4 is a block diagram of a reactive power control device for a combined cycle. FIG. 5, a control block diagram of the power control device, is a control flow diagram at the time of AV'R failure. l...Gas turbine 2°" steam turbine 3...
Generator 4... Main transformer 5... Generator breaker 6... System 7... Reactive power increase/decrease command 8°°° Rate of change limiter 9... Integrator
10°° Upper/lower limit limiter 11... Comparator 12°° Reactive power of each axis 13... Adder 14°"° Distributor 15... Each axis control section 16°°" Change rate limiter Vessel 17・
... Upper and lower limit limiter 19 ... Axis reactive power 20 ...
Excitation control device 21”' A V R22...AVH
Voltage setting device 23°°° Generator 24...Excitation transformer 25°°°Thyristor bridge 26...Field breaker 27'' Field winding 28°-MBC29°°° Instrument transformer Instrument 3o...Instrument current transformer 31°°°Excitation limiter 32...■C voltage setting device 33°°°Integrator 3
4...Subtractor 35...Reactive power of each axis other than AVa automatic operation 36.
...Adder 37...AVR, reactive power of each axis during automatic operation 39.
...Reactive power setting device 40...Comparator (7317) Agent Patent attorney Noriyuki Chika (and 1 other person) Figure 1 B

Claims (1)

[Claims] An automatic voltage regulator that controls the amount of excitation so that the generator voltage and the value of the voltage setter are equal, and a constant excitation regulator that controls the amount of excitation so that the field voltage and the value of the voltage setter are equal. - A reactive power control device that collectively controls multiple shafts of a combined power plant, the shaft of which is configured to combine the driving forces of a gas turbine and a steam turbine to drive a generator; The overall control unit that distributes the command value is provided with means for subtracting the total value of reactive power of the axes that are not subjected to excitation control by the automatic voltage regulator from the reactive power command value, and the overall control unit distributes the excitation control for each axis. Each axis control section controls reactive power by increasing or decreasing the voltage setting device of the automatic voltage regulator or constant excitation regulator of each axis based on the reactive power command value distributed to the system. A power setting device is provided, and when the automatic voltage regulator fails, the excitation control of the failed axis is switched from the automatic voltage regulator to the constant excitation regulator and set to match the setting value of the reactive power setting device for each axis. By controlling the voltage setting device of the excitation regulator and reducing the load of the failed shaft at a certain rate, the automatic voltage regulator can resolve the failed shaft without causing disturbance to the grid. A reactive power control device for a combined power generation plant characterized by a series of parallel power generation plants.