JPS63206200A - Exciting control device of synchronous generator - Google Patents

Abstract

PURPOSE:To perform the excitation smoothly during a speed increase from the finish of synchronization at a half speed to a rated speed, by controlling a field voltage set point by the output from a field current control circuit after the finish of synchronization in the neighbourhood of a half speed of the first and second synchronous generators. CONSTITUTION:In a biaxial synchronization of a primary machine 1P and a secondary machine 1S, a field circuit breaker 41 and an electromagnetic contactor 31 are closed to give initial excitation to generators. On this occasion, thyristors 2P and 2S are gate-blocked. When the biaxial synchronization is finished, the gate block is cancelled. Thus, the deviation between the field current obtained through an instrument current transformer 12 and a field current setter 6 is inputted into an interrupter 8, with the output of which a voltage setter 4 is operated. By the deviation between the set point set by the voltage setter 4 and the filed voltage obtained through an insulating converter 3, the gate of a thyristor 2 is controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an excitation control device for a cross compound synchronous generator that performs half-speed synchronization.

(Prior Art) An example of a conventional excitation control device for a cross compound synchronous generator is shown in FIG. 2, where the subscript P represents a primary machine and S represents a secondary machine.

In FIG. 2, the outputs of the primary generator IP and the secondary generator IS are electrically connected from the beginning, and by applying excitation to each of them, both become in a synchronous state, that is, two-axis synchronization.

From the viewpoint of establishing the excitation power supply and shortening the restart time,
For two-axis synchronization, a rated speed of about 172, that is, a half-speed synchronization method is adopted.

After the two-axis synchronization is completed, the speed is increased from half speed to the rated speed, but in order to prevent low frequency overexcitation of the generator during this time, the V/F ratio (voltage to frequency ratio) must be kept below a certain value. Therefore, the excitation control device generally controls the field voltage or field current of each generator to be constant.

That is, when the speed of each generator reaches the two-axis synchronization scheduled speed, both field circuit breakers 41 are closed, and subsequently, the electromagnetic contactor 31 is closed to give initial excitation to each generator. As the initial excitation power source, a DC power source obtained by rectifying an in-house battery power source or an in-house AC power source is used.

When the two-axis synchronization is completed, the gates of each thyristor 2 are activated, and the generator output is supplied to the field winding 10 via the excitation transformer 11. The magnetic field voltage obtained through the insulation converter 3 and the setting value set by the voltage setting device 4 are DC-
The voltages are compared and amplified by an AVR (field voltage adjustment circuit) 5, and the field voltages of each generator being sped up are controlled via a phase control circuit 9.

(Problem to be Solved by the Invention) However, in constant field voltage control, the field current changes due to temperature changes in the field winding 10, and the V/F ratio of the generator changes, so the V/F ratio is calculated. A circuit 13 and a reactive power detector 14 are provided to automatically adjust the voltage setting device 4 according to the V/F ratio and the cross current state. In addition, the V/F ratio calculation circuit 13
It is necessary to accurately detect frequencies over a wide range from around half speed to rated speed, which makes the circuit complex.

On the other hand, in the case of constant field current control, there is no change in the V/F ratio or change in reactive cross current due to changes in the field winding temperature, and control is simple, but there is no change in the input torque to both engines during speed-up. When equilibrium occurs, a difference occurs between the internally generated voltages and phases, and although synchronization is maintained, the field power source changes transiently due to armature reaction.

If constant field current control is performed at this time, the change in the field current that varies by the generator itself is suppressed in order to maintain synchronization, resulting in the problem of weakening the synchronization force.

In addition, the field voltage-window control circuit or field current-window control circuit used during speed-up continues to generate power even after the generator is connected to the power system via the main transformer 17 and breaker 18. It is sometimes used by switching with the machine voltage-window control circuit (AVR), and in such a case, if a system fault occurs, the constant field a current control will have a very unfavorable effect on the system.

That is, when the system voltage suddenly drops due to a system fault, the generator current increases rapidly, and the field current also increases transiently due to armature reaction.

In such cases, it is necessary to further strengthen the excitation in order for the generator to remain synchronized with the grid.

In AVR, excitation is strengthened in response to a drop in generator voltage caused by a drop in system voltage, whereas in constant field voltage control, excitation is neither weakened nor strengthened, but in constant field current control, excitation increases transiently. There is a problem in that the excitation is suppressed to a constant field current.

Therefore, the present invention provides an excitation control device for a cross compound synchronous generator that smoothly performs excitation during speed increase from completion of synchronization at half speed to rated speed, and prevents malfunctions due to temperature changes in the field winding. is intended to provide.

(Structure of the Invention) (Means for Solving the Problems) The excitation control device for a synchronous generator of the present invention includes a field current-window control circuit and a field voltage-window control circuit, A field current/window control circuit that performs excitation control after synchronization of the second synchronous generator at around half speed is completed outputs a deviation signal in order to set the field current of each of these synchronous generators to a set value. The field voltage-window control circuit supplies the field voltage to the field winding according to the deviation in order to set the field voltage of these synchronous generators to a set value corresponding to the deviation signal from the field current-window control circuit. Control the current.

(Function) After the synchronization of the first and second synchronous generators is completed at around half speed, field voltage-window control is performed according to the set value corresponding to the deviation signal from the set value from the field current-window control circuit. A circuit controls the field current supplied to the field winding.

(Example) An embodiment of the present invention will be described with reference to the drawings.

The present invention is an excitation control device for a cross-compound synchronous generator that synchronizes a primary generator and a secondary generator at around half speed, and increases the speed with constant field voltage control after synchronization is completed, by detecting field current. A field current-window control circuit with a slow response time is provided to control the field voltage to a set value, and its output operates the voltage setting device of the field voltage-window control circuit to control the temperature change of the field winding. The generator's V/F is controlled by keeping the field current constant regardless of changes in resistance due to
This maintains the ratio within an allowable value and prevents problems caused by constant field current control in transient states when speeding up and when connecting to a power system.

An embodiment of the present invention is shown in FIG. 1, where the suffix P stands for primary horizontal use and S stands for secondary machine use.

In FIG. 1, when performing two-axis synchronization, the field breaker 41 is closed, and the electromagnetic contactor 31 subsequently applies initial excitation to the generator 1.

At this time, thyristor 2 is gate blocked, and the gate is blocked when the two-axis synchronization is completed (including conditions where the generator voltage is above the specified value and the cross current is almost zero because each generator is operating in synchronization). Release.

The deviation between the thyristor anode current equivalent to the field current obtained via the instrument current transformer 12 and the field current modifier 6 is input to the interrupter 8 via the amplifier 7, and the output signal is input to the voltage setting device 4. operate.

The set value set by the voltage setter 4 and the field voltage obtained via the insulation converter 3 are input to the DC-AVR 5, and the phase control circuit 9 controls the gate of the thyristor 2 based on the output signal thereof.

As a result, both the constant field voltage control and the constant field current control are performed at the same time, since the voltage setting device 4 is operated by the interrupter 8.

It does not respond to rapid field current changes during transient periods, and the disadvantages of constant field current control do not occur.

On the other hand, field current change due to temperature change in the field winding 10 is much slower than field current change due to armature reaction, so field current constant control is effective.

There is no problem with constant field voltage control.

Although this embodiment describes the case of a thyristor excitation method so that the gist of the invention can be understood, it goes without saying that the present invention is also applicable to an excitation method using a shaft-coupled exciter. No, however, in the case of a system using an exciter, the exciter output current is detected as a generator field current, and what the thyristor 2 output is connected to is the exciter field.

〔Effect of the invention〕

As explained above, according to the present invention, in addition to the field voltage constant control loop, a field current constant control loop with a slow response speed is provided in the excitation control device of the cross compound synchronous generator, and the output is set to the field voltage constant control loop. Since the field current is controlled slowly and constant as a correction signal for constant control, the field current remains constant regardless of temperature changes in the field winding during steady state, and the V/F ratio is controlled within the allowable value. At the same time, in a transient state such as during speed increase, field voltage constant control is performed to provide an appropriate response to armature reaction, thereby enabling smooth control of the cross compound synchronous generator.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an excitation control device for a cross compound synchronous generator showing an embodiment of the present invention, and FIG. 2 is a block diagram of a conventional excitation control device for a cross compound synchronous generator. 1...Synchronous generator 2...Thyristor 3...
・Isolation converter 4...Voltage setting device 5...DC
-AVR6...Field current setting device 7...Amplifier
8... Interrupter 9... Phase control circuit
1o...Field winding 11...Excitation transformer 1
2...Instrument current transformer agent Patent attorney Nori Chika Ken Yudo Hirofumi Mitsumata Busen Shuro

Claims (1)

[Claims] After the synchronization of the first and second synchronous generators at around half speed is completed, a field current constant control circuit outputs a deviation signal to set the field current of these synchronous generators to their respective set values, and a constant field voltage control circuit that controls the field current supplied to the field winding according to the deviation in order to set the field voltage of the generator to a set value corresponding to the deviation signal from the constant field current control circuit; An excitation control device for a synchronous generator, comprising: