JPS60134800A - Frequency control circuit - Google Patents

Abstract

PURPOSE:To suppress the variation in the frequency of a power system without increasing the power source capacity by controlling a governor by previously predicting the variation in the frequency due to the alteration in the power of a load. CONSTITUTION:A speed actual value signal outputted from a speed detector 7 coupled with a vapor turbine 3, and a speed target value signal set by a speed setter 6 are inputted to a governor 8, and if the both signals have a deviation, a control signal for setting the deviation to zero is outputted from the governor 8. AC power outputted from an AC generator 11 is applied through a breaker 12 to a bus 13. A transformer 21 for an instrument is connected with the bus 13, and a current transformer 22 is provided in a circuit to an arc furnace 17. A power detector 23 detects a power signal corresponding to the power flowed to an arc furnace 17 by the detected voltage and current, and this power signal is applied to the governor 8 through a calculator 24.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a frequency control circuit that maintains the system frequency constant even when a load with severe power fluctuations is connected to a power system with a small power supply capacity.

[Prior art and its problems]

Electric furnaces such as arc furnaces experience large power fluctuations that occur abruptly and irregularly. Therefore, it is desirable that the power system to which such a load is connected be equipped with a power supply capacity that is ten times or more the rated capacity of the arc furnace. However, recently, loads that cause sudden and large power fluctuations are often installed in power systems whose power supply capacity is not sufficiently large compared to the load companies.

FIG. 1 is a circuit diagram showing a conventional example of a power system to which an arc furnace is connected. In FIG. 1, steam generated by a boiler 1 flows through a steam line indicated by a broken line, passes through a control valve 2 serving as energy amount control means, flows into a steam turbine 3, and rotates this turbine. The steam that has completed its work is cooled by the condenser 4 and returned to water, which is then pressure-fed by the water supply pump 5 and turned into steam again in the boiler 1. The two-dot chain line between the condenser 4 → feed pump 5 → boiler 1 means that it is in a water state.

A speed target value signal set by a speed setting device 6 and a signal indicating an actual speed value of the steam turbine 3 outputted by a speed detector 7 coupled to the steam turbine 3 are input to the speed governor 8, A control signal that makes the deviation of the input signal zero is output, and the valve opening degree of the control valve 2 is adjusted. The control valve 2 adjusts the amount of steam flowing into the steam turbine 3, and even if load fluctuations occur, the vortex turbine 3 attempts to maintain the speed according to the speed target value signal. 9 is a bypass valve.

An alternating current generator 11 is coupled to the above-mentioned steam turbine 3, and alternating current power output from the alternating current generator 11 is applied to a bus bar 13 via a circuit breaker 12. This mother ItI! 1
A general load 15 is connected to 113 via a circuit breaker 14, and an arc furnace 1 as a variable load with large power fluctuations.
7 is connected via a circuit breaker 16, and receives power from the above-mentioned alternator 11. Now, let Ml be the inertia constant of the steam turbine 3 and the AC generator 11, let ω be the rotational angular velocity thereof, let Tm be the mechanical output (that is, the output of the steam turbine), and To be the electrical output (that is, the load power).
The relationship between the frequency of the power system and the load power shown in FIG. 1 is roughly expressed by equation (1).

That is, as the load power Te increases, the angular velocity, that is, the frequency, decreases in accordance with the value of the inertia constant M.

This decrease in angular velocity is detected by the speed detector 7 and the speed governor 8
Since the output of the speed governor 8 is input to the control valve 2,
By increasing the valve opening degree to increase the steam flow rate to the steam turbine 3, the mechanical output Tm is increased, and the frequency is returned to the value before the load power increased. This type of operation is based on the premise that the frequency changes due to an increase in load power, and the frequency fluctuation is recovered by detecting the frequency fluctuation and controlling the valve opening. It was not possible to prevent frequency fluctuation itself.

The general load 15 therefore has the disadvantage of being directly affected by this frequency variation. In addition, in order to suppress frequency fluctuations in the power system, the equipment on the power supply side, namely the boiler 1, steam turbine 3, alternating current generator 11
Since the capacity of the power source must be sufficiently large, the equipment cost increases and the operating rate of the power supply equipment decreases.

[Purpose of the Invention] The present invention is designed to compensate for frequency fluctuations in a power system in which a load that irregularly generates large and rapid power fluctuations is connected to a power source with a smaller capacity than the load capacity. It is an object of the present invention to provide a frequency control circuit that can suppress the frequency without increasing the frequency.

[Key points of the invention]

This invention attempts to suppress frequency fluctuations by configuring a circuit to detect power fluctuations in a load, predict frequency fluctuations due to the power fluctuations in advance, and control a speed governor.

[Embodiments of the invention]

FIG. 2 is a circuit diagram showing an embodiment of the present invention, and the content of the present invention will be explained below with reference to FIG.

In FIG. 2, the broken line is the line through which steam flows, and the two-dot chain line is the line through which condensate flows.

In FIG. 2, steam generated by a boiler 1 has its steam amount adjusted by a control valve 2, flows into a steam turbine 3, rotates this turbine 3, and then is discharged and cooled by a condenser 4. and return to the water.

This water is pumped by the water supply pump 5, flows into the boiler 1, is heated, and becomes steam again. The speed actual value signal output from the speed detector 7 coupled to the steam turbine 3 and the speed target value signal set by the speed setter 6 are the speed governor 8.
If there is a deviation between these two signals, a control signal to zero the deviation is issued from the speed governor 8 to the energy amount control means and the prefectural control valve 2, and the control valve 2 operates based on this signal. Since the valve opening degree is changed by changing the valve opening degree, the flow rate of steam flowing into the steam turbine 3, that is, the amount of energy changes, and even if the load on the steam turbine 3 changes, the speed is kept constant.

An alternator 11 is coupled to the steam turbine 3,
The alternating current power output by this alternating current generator 11 is given to the bus bar 13 via the circuit breaker 12, and this bus bar 13K circuit breaker 1
The electric current is supplied to a general load 15 connected to the bus 13 via a circuit breaker 16, and to an arc furnace 17 as a variable load, which is also connected to the bus 13 via a circuit breaker 16. Here, it is assumed that the capacity of the general load 15 is smaller than the capacity of the arc furnace 17, and that the capacity of the alternator 11 also has a larger margin than the rated capacity of the arc furnace 17. Note that a separate power source having a small capacity compared to the capacity of the alternating current generator 11 may be connected to the bus bar 13, but this separate power source will be omitted for ease of explanation.

In the power system shown in Fig. 2, the arc furnace 17 occupies most of its load capacity, so if the electric power flowing into the arc furnace suddenly fluctuates, it can be explained using equation (1) above. As mentioned above, the frequency of the power system 5 fluctuates, which adversely affects the general load 15.

In the present invention, an instrument transformer 21 is connected to the bus bar 13, a current transformer 22 is installed in the circuit to the arc furnace 17, and the power detector 23 detects the voltage and current flowing into the arc furnace 17. Create a power signal corresponding to the power that is generated. This power signal is applied to the speed governor 8 via the arithmetic circuit 24,
The mechanical output Tm shown in the above-mentioned equation (1) is quickly changed. The arithmetic circuit 24 performs (a) level matching between the magnitude of electric power and the valve opening of the control valve 2, (b) comparison between the rate of change in load and the rate of change in the valve opening, and (c) alternating current generator. It performs calculations such as energy distribution when there are multiple AC generators, but if there is only one AC generator, the functions shown in item (a) above are basically sufficient.

FIG. 3 is a circuit diagram showing the simplest example of the arithmetic circuit 24 and speed governor 8. In FIG. 3, the arithmetic circuit 240
A power signal from the power detector 23 is applied to the input terminal 24A, and after the level is adjusted by the level conversion resistor 25, it is applied to the input terminal 8C of the speed governor 8 via the output terminal 24D. The signal is then input to an operational amplifier 85. On the other hand, the speed target value signal from the speed setter 6 is input from the input terminal 8A via the input resistor 81, and the actual speed value signal fed back from the speed detector 7 is input from the input terminal 8B via the input resistor 82 to the operational amplifier 85. be done. This operational amplifier 85 is configured as a proportional amplifier having a feedback resistor 84, and performs a speed regulating operation using a speed target value signal inputted from the input terminal 8A and a speed actual value signal inputted from the input terminal 8B. Since a speed regulation rate is created by the offset of this proportional amplifier, this alternator 11 can be operated in parallel with another alternating current power source.

In the present invention, since the output signal of the arithmetic circuit 24 is input from the input terminal 8C, when the electric power of the arc furnace 17 fluctuates, even if the actual speed value signal from the speed detector 7 does not change yet, the load Since a signal corresponding to the power fluctuation is given to the control valve 2 via the speed governor 8, changes in the frequency are suppressed in advance by changing the valve opening of the control valve 2.

Although the governor 8 shown in FIG. 3 is an example of an electric governor, it can also be applied to a hydraulic governor by adding an electric/hydraulic converter. Furthermore, in the circuit shown in FIG. 2, for example, if the steam pressure of the boiler 1 decreases, the steam turbine 3 may not be able to obtain the required amount of steam. Therefore, the boiler 1 normally generates steam in an amount equivalent to the output of the steam turbine 3, and this excess steam is bypassed directly to the condenser 4 via the bypass valve 9. When the amount of steam required for the turbine 3 is insufficient due to a change in electric power, the output signal of the arithmetic circuit 24 (not shown) may cause the bypass valve 9 to be suddenly closed (or may be suddenly opened in some cases), or the boiler 1 may be suddenly closed. This can be dealt with by controlling the pressure.

In the embodiment shown in FIG. 2, the prime mover that drives the alternator 11 is a steam turbine, but if this is a gas turbine or diesel engine, the governor 8 controls the amount of fuel supplied to the prime mover. It is a fuel valve that adjusts/decreases the amount of fuel, and there is no need to control a boiler such as a steam turbine, making it easier to apply the present invention. Furthermore, by having a microcomputer perform the calculations performed by the calculation circuit 24, more sophisticated valve opening calculations, energy distribution calculations, etc. can be realized.

〔Effect of the invention〕

According to the present invention, the power of a variable load that is connected to a small-capacity power supply and that experiences large and sudden power fluctuations irregularly is detected.1. This power signal is configured to be input to the speed governor via an arithmetic circuit. By configuring like this,
In the past, when the frequency fluctuated due to power fluctuations in the load, this frequency fluctuation was detected and the governor of the generator prime mover was controlled to return the frequency to the original value. Since the power governor of the prime mover is controlled by detecting power fluctuations in the load, the
This frequency fluctuation can be suppressed. Therefore, the generator capacity has a little margin for the variable load capacity.

Even if there is, frequency fluctuation can be suppressed as much as possible, so
Since the capacity of the power supply equipment can be reduced, a large cost reduction effect can be obtained, and there is also an effect that there is no need to adversely affect other loads such as frequency fluctuations.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a conventional example of a power system to which a load with large power fluctuations is connected, FIG. 2 is a circuit diagram showing an embodiment of the present invention, and FIG. It is a circuit diagram showing an example of a speed machine. DESCRIPTION OF SYMBOLS 1... Boiler, 2... Control valve as energy amount control means, 3... Steam turbine, 4... Condenser, 5...
... Water supply pump, 6 ... Speed setting device, 7 ... Speed detector, 8 ... Speed governor, 9 ... Bypass valve, 11 ...
・AC generator, 12, 14.16...breaker, 15・
... General load, 17... Arc furnace as variable load,
21... Instrument transformer, 22... Current transformer, 23...
- Power detector, 24... Arithmetic circuit, 25... Level conversion resistor, 85... Operational amplifier. Figure 1 Figure 2

Claims (1)

[Claims] A speed governor that generates a control signal to zero the deviation between the speed target value signal set by the speed setting device and the speed actual value signal obtained from the speed detection means provided in the prime mover; a prime mover equipped with an energy amount control means for controlling the amount of driving energy of the engine; an alternator that is driven by the prime mover and outputs electric power at a constant frequency; , in a power system consisting of an AC load whose capacity is smaller than the capacity of the current transformer generator, a power detection means for detecting power flowing into the AC load; and a power signal outputted by the power detection means. A frequency control circuit comprising: the speed governor; and an arithmetic unit that inputs data to the speed governor in accordance with the characteristics of the energy amount control means.