JPH0477328B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a reactive power control device for a combined cycle power plant (hereinafter referred to as a combined cycle) formed by combining a plurality of gas turbines and steam turbines.

[Technical background of the invention and its problems] One method of improving the efficiency of the total power generation system is to generate steam from the gas turbine exhaust, drive the steam turbine with the steam, and drive the gas turbine and the steam turbine. Combined cycle systems, in which power is generated by combining driving forces and turning a generator, have recently come into use.

FIG. 1 shows an example of the configuration of the above-mentioned combined cycle.

The gas turbine 1, the steam turbine 2, and the generator 3 are connected on one shaft, and the output of the generator 3 is transferred to the main transformer 4.
After the voltage is boosted at , it is connected to a system 6 via a disconnector 5 . The output of the generator 3 used is one with a small to medium capacity of about 100 MW, and a plurality of the above systems (about 5 to 6) are connected in parallel to form one power generation plant.

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

FIG. 2 shows a schematic control block diagram of a reactive power control device as one of the above-mentioned control devices. A reactive power command value is generated by an integrator 9 via a change rate limiter 8 in response to a reactive power increase/decrease command 7 from a central power supply station or a manual switch by an operator. After being limited by the upper and lower limit controller 10 determined by the number of operating units, the power is input to the comparator 11 and compared with the value obtained by adding together the reactive power 12 of each axis by the adder 13. The comparator 11 compares the command value of the reactive power with the actual value, and only the difference is inputted to the distributor 14 to distribute the target value of the reactive power to each axis. The above reactive power target value is input to each axis control section 15, and the rate of change limiter 1
6. After being limited by the upper and lower limit limiter 17, the actual reactive power 1 of the axis being controlled by the comparator 18
9, the difference between the two is input to the excitation device 20 of the generator as a reactive power increase/decrease command, and the voltage setting device 22 of the automatic voltage regulator (hereinafter referred to as AVR) 21 is increased/decreased by the reactive power increase/decrease command. Let's do it.

AVR 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, increasing the excitation current will generate reactive power. increases,
Reducing the excitation current reduces reactive power. In other words, it is possible to control the increase and decrease of reactive power using AVR.

FIG. 3 shows an example of a configuration diagram of an excitation device. This example shows a typical example using the thyristor direct excitation method. What is thyristor direct excitation? In Fig. 3, the output voltage of the generator 23 is lowered to an appropriate voltage level by the excitation transformer 24, and then rectified by the thyristor bridge 25 to create a field and a disconnector 26. This is an excitation method in which the power is supplied to the field winding 27 via the generator 23, and since the output of the generator 23 is used as an excitation source, no other excitation source is required. As an excitation device, we have conventionally used AVR21 to adjust the output voltage of the generator to a certain set value,
It has two regulators, a constant excitation regulator (hereinafter referred to as MEC) 28, which performs control to adjust the field current to a certain set value when the AVR 21 malfunctions or to adjust the field current to a certain set value.

When controlled by AVR21,
The output voltage of the generator 23 is input to the AVR 21 via the voltage transformer 29, and the thyristor bridge 2 is adjusted to match the setting value of the voltage setting device 22 of the AVR 21.
A pulse signal is sent to the gate of each thyristor 5 to control the excitation current. For the output voltage and current of the generator, signals are sent to the AVR 21 from over-excitation, under-excitation, etc. limiters 31 via the instrument transformer 29 or instrument current transformer 30, and the amount of excitation is limited to reach the stable operation limit. controlled so as not to exceed.

If control is performed by MEC28,
Field voltage or field current is input to MEC28,
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 AVR 21 and the control by the MEC 28 is that the voltage setting values 22 and 32 are compared with the generator terminal voltage, or the field voltage is
The difference is whether it is compared with an electric current. When the generator is connected to the grid, if the grid voltage fluctuates, the generator voltage will also fluctuate. At this time, when AVR is used for control, the excitation current is controlled in a direction that suppresses voltage fluctuations, which improves the stability of the entire system. On the other hand, when controlling with MEC, the amount of excitation does not change even if the system fluctuates, so no improvement in system stability can be expected.

For this reason, conventionally the AVR performs control during normal operation, and only when the AVR malfunctions or starts up.
The operation is controlled by MEC. That is, during MEC control due to AVR failure, the operator monitors conditions such as intermediate supply commands or system status, and manually changes the MEC voltage setting device. However, in a combined cycle, multiple generators are controlled as if they were one, so a certain axis
If an AVR malfunctions, the operator must check the MEC for that axis.
It is difficult to always manually control the voltage setting device.

Therefore, conventional reactive power control devices for combined cycles perform control to trip the failed axis due to an AVR failure. However, according to this conventional method, since a combined cycle plant is made up of multiple axes, even if one shaft is tripped, the impact on the entire plant is smaller than in non-combined cycle plants. However, there was a problem in that tripping would cause considerable disturbance to the system.

[Objective of the Invention] The present invention aims to provide a reactive power control device for a combined cycle power generation plant that can continue operation by MEC without tripping the failed shaft of the AVR or placing a burden on the operator. purpose.

[Summary of the Invention] Therefore, the present invention performs MEC operation on the failed axis of the AVR with a preset value, subtracts the reactive power from the reactive power command value, and distributes the subtracted command value to each AVR. By doing so,
The feature is that fluctuations in reactive power are adjusted by a normal AVR.

[Embodiments of the Invention] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 4 shows a control block diagram of a reactive power control device showing one embodiment of the present invention, in which the same reference numerals as in FIG. 2 indicate the same or corresponding parts. The difference in the configuration of the diagram from that in Figure 2 is that after the reactive power increase/decrease command 7 is integrated by the integrator 33, it is input to the subtracter 34, and the reactive power 35 of the axis that is not in AVR automatic operation is input to the adder 36. The difference is that the total value is subtracted and the output thereof is input to the change rate limiter 8.
In other words, the idea is that the reactive power of the axes that are 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 10 is sent to the comparator 11.
Adder 1 adds the reactive power 37 of the axis during AVR automatic operation.
Compare with the value added in step 3. This is an AVR
This is because the reactive power of non-autonomous driving axes has already been subtracted, so we are considering reactive power feedback only for AVR autonomous driving axes. Next, the distributor 14 distributes the target value of reactive power to each axis during AVR automatic operation and sends a signal to each axis control section 15. Hereinafter, the same control as described above with reference to FIG. 2 is performed for the axes during AVR automatic operation.

On the other hand, the AVR malfunctions and the exciter 20 cannot operate.
The axis that has transitioned to control by the MEC 28 inputs the reactive power setter 38 at the time of AVR failure and the actual reactive power 19 of the axis being controlled to the comparator 39, and is closed when the control transitions to MEC control due to the AVR failure. The voltage setter 32 of the MEC 28 is controlled via the contact 40.

At this time, the setting value of the reactive power setting device 38 can be arbitrarily selected, but the load that the generator can stably bear is maximum when the reactive power is zero, that is, the power factor is "1". Therefore, the setting value may be set to zero.

In this way, if the AVR fails, AVR control will transition to MEC control, and the reactive power of the axis that transitioned to MEC control will be set to zero or an arbitrary value, and the reactive power of the axes other than this AVR automatic will be reduced. By subtracting from the command value in advance and controlling reactive power only with the AVR automatic axis, even if the AVR breaks down, it is possible to continue operation without the operator having to constantly monitor and control it. .

In the above embodiments, the excitation system was explained using a thyristor direct system, but it goes without saying that other systems can provide the same effects.

In addition, the reactive power setting device 38 in the above embodiment
It is also possible to use a reactive power relay instead of the comparator 39.

[Effects of the Invention] As described above, according to the present invention, even when the AVR malfunctions, it can be operated without burdening the operator.
Continuation of automatic operation using MEC becomes possible.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a general combined cycle, and FIG. 2 is a control block diagram of a conventional reactive power control device applied to the combined cycle.
FIG. 3 is a configuration diagram of a general excitation device using a thyristor direct excitation method, and FIG. 4 is a control block diagram of a reactive power control device according to an embodiment of the present invention applied to the combined cycle of FIG. 1. . 7... Increase/decrease command, 8... Change rate limiter, 9, 3
3...Integrator, 10...Upper/lower limit controller, 11,1
8, 39... Comparator, 13, 36... Adder, 1
4... Distributor, 15... Each axis control unit, 16... Rate of change limiter, 17... Upper and lower limit limiter, 19... Actual reactive power, 20... Excitation device, 21... AVR,
22, 32... Voltage setting device, 28... MEC, 3
4...Subtractor, 35, 37...Reactive power, 38...
...Reactive power setting device, 40...Contact.

Claims (1)

[Claims] 1. A power generation plant configured to drive a generator using a gas turbine and a steam turbine. The power generation plant has a plurality of axes, and the output voltage of the generator of each of these axes is compared with a set value, and the output voltage is determined according to the deviation. automatic voltage regulators that control the excitation current of the generator; and automatic voltage regulators that compare the excitation current of the generator of each axis with their respective set values and control the excitation current of the generator to a constant value according to the deviation. A combined power generation plant comprising a constant excitation regulator, in which the output voltage of the generator of each axis is always controlled by an automatic voltage regulator, and when the automatic voltage regulator fails, the control is switched to the constant excitation regulator. In this reactive power control device, means for subtracting the total value of reactive power of the axes whose excitation is controlled by the constant excitation regulator from a value obtained by integrating reactive power increase/decrease commands, and a value subtracted by the means. means for inputting the same into an integrator via a rate of change limiter to form a reactive power command value; and an axis whose excitation is controlled by the automatic voltage regulator from the reactive power command value formed by this means. means for subtracting the total value of reactive power, and means for distributing a value corresponding to the reactive power command deviation value subtracted by this means as the set value of the axis whose excitation is controlled by the automatic voltage regulator. A reactive power control device for a combined power generation plant, comprising: