JPS63305800A - Excitation controller for synchronous machine - Google Patents

Abstract

PURPOSE:To balance an output from a thyristor converter while smoothly conducting positive and negative changeover control by adding a compensatory signal interlocked with the change of the load circuit constitution of the thyristor converter to the control signal of the thyristor converter having positive and negative bidirectional characteristics. CONSTITUTION:An output from an exciter 2 supplies the excitation currents of the exciter 2 required at the time of normal operation by a field regulating resistor FR. A control signal Vc corresponding to a deviation between output voltage Vg from a synchronous machine 1 and reference voltage VREF is transmitted to a positive-side thyristor converter 4P or a negative-side thyristor converter 4N through an adder 33 and a pulse generator 34. On the other hand, a bias signal circuit 37 adds signal to the control signal Vc according to the operation of an interlocking relay 38 interlocked with a switch 5 switching outputs from the thyristor converters 4P, 4N.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an excitation control device for a synchronous machine, and in particular, includes a thyristor converter having positive/negative bidirectional output characteristics, and the output of the thyristor converter is The present invention relates to a control device suitable for balancing or smoothly switching between positive and negative.

[Conventional technology]

The conventional device calculates a correction signal based on the firing angle signal of the thyristor converter and the magnitude of the converter alternating current for the nonlinear characteristics of the thyristor converter when the current is interrupted, as described in Patent Publication No. 60-27270. was.

However, no consideration was given to the case where the load characteristics change from a resistive load to an inductive load.

[Problem that the invention seeks to solve]

The above conventional technology does not take into consideration the case where the load characteristics of the thyristor converter change.

In addition, by using a positive/negative bidirectional thyristor converter with non-circulating current switching in which two sets of thyristor converters are connected in antiparallel, the output current can be continuously output in the constant region of almost zero or in the intermittent region of a small positive or negative current. The device used has a problem in that the gain characteristics between the command signal and the thyristor output voltage change between the intermittent current region and the continuous current region.

The purpose of the present invention is to add a compensation signal to each thyristor converter having positive and negative bidirectional characteristics, and to switch the amount of compensation signal in conjunction with changes in the load circuit configuration of the thyristor converter, regardless of load changes. When the control signal to the thyristor converter is zero, the output voltage of the thyristor converter becomes zero.

The purpose of this invention is to prevent gain deterioration of a thyristor converter by adding a nonlinear compensation signal to a control signal in a region where the load current is intermittent.

[Means for solving problems]

Among the above purposes, in order to make the output voltage of the positive/negative bidirectional thyristor converter zero when the control input signal is zero, it is necessary to set the control angle at which the output voltage becomes zero, which is determined by the power supply and load characteristics of the thyristor converter. This is achieved by adding compensation signals corresponding to the positive and negative gate control circuits. In addition, in order to prevent the gain of the thyristor converter from deteriorating in the region where the load current is intermittent, the control signal is input to the front stage of the gate control circuit, and the control signal is amplified in the region where the load current is intermittent. This is achieved by adding a nonlinear compensation circuit. This will be explained in detail below.

Figure 2 shows an example of a three-phase full-wave thyristor converter, where the input voltage,
U due to the relationship between output current, output voltage, and thyristor firing control angle.
This shows a case where the P-phase thyristor and the V-phase N-side thyristor are fired. When the thyristor fires at the firing angle α, the output current knee becomes a value determined by the load characteristics, and in the case of an inductive load, the current continues to flow even if the power supply voltage Euv becomes negative, and the current becomes zero at the extinction angle θ. . The output voltage has the waveform of the power supply voltage Euv only during the period when the load current knee continues to flow. When the load current knee becomes zero, the thyristor is extinguished, so it usually becomes zero.

The following explanation will be made regarding the case where the output voltage when the thyristor is turned off is zero.

The output current I4 is expressed by (1) below, and is determined by the characteristics of the load, that is, the reactor or resistance R, and the thyristor firing angle α.

The output voltage average value Voc in this case can be expressed by equation (2).

...(2) However, if the firing angle α is less than 1, the next W-phase N-side thyristor fires before the power supply Euv becomes zero, so Euv
There is no need to consider the negative period of . In this case, as is well known, it can be expressed by equation (3).

vDC=-cosa-(3)π Also, when the current is intermittent, if the firing angle α is 1π or more, E
Since there is no period in which uv is positive, the current voltage 4 is always zero and the output voltage Voc is also zero.

Taking these things into consideration, the relationship between the thyristor firing angle α and the output voltage Voc is illustrated in FIG. 3.

That is, when the current is intermittent, the characteristics are nonlinear compared to when the current is continuous only during the period when the firing angle α is from 60' to 120@.

As is well known, in the control of a thyristor converter without circulating current that generates positive and negative bidirectional output currents for the same load by antiparallel connection, for example, in the case of switching from positive to negative, the control signal changes from positive to negative. After confirming that the conditions have changed and that the load current has become intermittent (generally, the current intermittent/intermittent ratio is 1 or more), turn off the positive side gate pulse and switch the negative side thyristor that had been extinguished. Give a gate pulse.

For example, if the load characteristics correspond to θ=0 in Figure 3 (
In the case of a resistor load), in order to make the output voltage of the bidirectional thyristor converter at zero when the control signal is zero, add a bias corresponding to θR to the positive side gate control circuit,
- It is sufficient to apply a bias corresponding to OL to the gate control circuit on the negative side.

[Effect]

In the case of automatic voltage regulator "exclusion", the switch 5 in Fig. 1 is opened, and the load of the thyristor converter is the ignition acceleration resistance Ro of the thyristor and the resistance R of the surge absorption circuit.
In addition to oe and capacitor Coc, only the capacitor between thyristor A- (not shown) serves as a load for the thyristor converter. in this case.

The ignition promoting resistance Ro is from several hundred ohms to several thousand ohms,
The control angle at which the output voltage of the thyristor converter becomes zero when the capacitors are connected in parallel is (XR>120"
, ab>120'.

Therefore, in order to make the output voltage of the thyristor converter zero when the control signal Vc=O, it is necessary to apply a larger bias to each θR9θ.

On the other hand, when the automatic voltage regulator is "used", the switch 5 is closed, and the loads of the thyristor converter are the reactor Lly resistor RsAtR3B shown in FIG. etc. are connected.

Therefore, the condition under which the output voltage of the thyristor converter becomes zero when the current is interrupted is 30>θ>0. Therefore, when the automatic voltage regulator is in the "used" and "excluded" states,
In order to make the output voltage of the thyristor converter zero when the control signal is zero, the compensation signal (bias) applied to the gate control circuit may be switched in conjunction with the switch 5.

Next, in order to prevent the gain of the thyristor converter from decreasing when the load current is intermittent, in the α-Voc characteristic shown in Figure 3, it is necessary to
Nonlinear characteristics may be added to the positive side and negative side thyristor gate control circuits between Δα/ΔVc so that the characteristics of ΔVDC/Δα at 120°) become the characteristics when the load current is continuous.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. The excitation of the synchronous machine 1 is given by the output of the exciter 2.
The output of is supplied with the excitation current of the exciter 2 required during normal operation by the field adjustment resistor FR. When the voltage of the synchronous machine 1 changes due to load fluctuations, etc., to automatically keep the value of the reference voltage V REF constant, close the switch 5 and change the excitation current of the exciter 2 by the thyristor converter 4P or 4N. This is done by adjusting the In other words, synchronous machine 1
The output voltage of is the reference value vRf! If it falls below F.

The deviation detector 31 detects the signal, and the amplifier 32 amplifies the signal to output a control signal Vc for the thyristor control circuit. Control signal Vc is applied to pulse generator 34 via adder 33. The pulse generator 34 generates an ignition pulse corresponding to the applied control signal α' to the thyristor converter 4.
P, the excitation of the exciter 2 is increased, the output voltage of the synchronous machine 1 is increased, and control is performed so that it reaches the reference value VREF. Conversely, when the output voltage of the synchronous machine 1 increases, the output of the thyristor converter 4N increases, the excitation of the exciter 2 is decreased, and the output voltage of the synchronous machine 1 is controlled to be lowered to the reference value VREF. do. The output voltage of synchronous machine 1 is the reference value V REF
When it matches the value of 4, thyristor converter 4P, 4
Both N outputs are set to zero. Further, the outputs of the thyristor converters 4P and 4N are given to the automatic tracking circuit 6,
When there is a voltage of 10 or - between the outputs P and N of the thyristor converter, the FR is controlled to increase or decrease so that the output voltage becomes almost zero. Since the outputs of the thyristor converters 4P and 4N are opened and closed by the switch 5, when the switch 5 is closed, the load is on the accelerator L1, but when the switch 5 is open, the ignition is not performed. Loads include the accelerating resistor Ro, the surge absorbing resistor Roe, and the capacitor Coc. Considering the case where the circuit breaker 5 is closed, the reference value V R1! is set so that the outputs of the thyristor converters 4P and 4N become zero in order to eliminate the shock when the circuit is closed. Adjust P.

However, without a bias signal circuit, the output of the thyristor converter will be θ = 0 or more as shown in Figure 3, even at a firing angle of 90', where the output voltage is almost zero, if the load current is continuous. Therefore, the reference value V R1 is correctly set.
! The switch 5 cannot be closed without adjusting F and causing disturbance.

A bias signal circuit 37 is required because a problem like this example occurs. The output signal voltage of the bias signal circuit 37 is added to the control signal Vc by an adder 33 before the gate pulse generator 34. The magnitude of the bias signal is switched by an interlock relay 38 linked to the switch 5, and when the switch 5 is open, the load resistance Ro of the thyristor converter is large, and there is also the influence of the capacitor connected in parallel to Ro, so that control is not possible. In order to make the output voltage of the thyristor converter zero when the signal Vc=O, the bias amount needs to be equal to or more than θR.

When the switch 5 is closed, circuits Id1 to Id3 shown in FIG. 1 exist as loads for the thyristor converter. rJR
In order to eliminate the shock when the closed circuit In5 opens, the reference value V must be set so that the outputs of the thyristor converters 4P and 4N become zero.
Adjust REF. In this case, the extinction angle θ determined by the load accelerator and the resistor exists between 30>θ>0. Therefore, it is sufficient to use a bias signal having a smaller amount of phase compensation than the bias signal added while the switch 5 is open.

Next, consider the operation of the thyristor converter when the reference value V REF is changed to change the control signal Vc while the switch 5 is closed. The input-output characteristics of the gate pulse generator 34 are as shown in FIG.
When the input-output characteristics of the thyristor converter are assumed to change from ~0'', when the current is continuous in an inductive load, the control signal Vc is as shown by LR (or LL) in Figure 6.
In order to set Voc=O at =0, the bias signal must be 4.5
Requires V. However, in order to make the output voltage zero and the output current zero even with an inductive load, E
,,<O, that is, α>-π or more. Therefore, if a bias is applied that takes into account the extinction angle determined by the load current and the R characteristic, for example, if the characteristic of RR in Fig. 6 is changed to RR' by applying a bias, LR The gain of the RR' characteristic is lower than the gain of the characteristic. Therefore, in order to compensate for this decrease in gain, a compensation circuit having nonlinear characteristics between input and output may be added as shown in the nonlinear compensation circuit 39 in FIG.

That is, when the output voltage characteristic of the thyristor converter in the region where the load current is intermittent becomes the RR characteristic in FIG.
By adding a bias VBR that makes the R characteristic the RR' characteristic to the control signal, and adding a compensation signal that inputs the control signal and makes the output nonlinear to Vc, the L
It can be adjusted to R characteristics.

〔Effect of the invention〕

According to the present invention, it is possible to easily obtain balanced characteristics of the output voltage when opening and closing the output switch of an automatic voltage regulator using a thyristor converter having positive and negative bidirectional output characteristics in the output stage, and This has the effect of preventing gain deterioration in the load current intermittent state when the positive/negative output of the converter changes and smoothly performing positive/negative switching control.

[Brief explanation of drawings]

FIG. 1 is an excitation control configuration diagram showing one embodiment of the present invention, and FIG.
The figure is a waveform diagram of the power supply voltage and output voltage in a three-phase full-wave rectifier circuit, Figure 3 is a diagram of the output characteristics of the thyristor converter with respect to the firing angle, and Figure 4 is a configuration diagram of the firing angle compensation signal circuit of the present invention.
Figure 5 is an input-output characteristic diagram of the gate pulse generator, Figure 6
The figure is an input-output characteristic diagram of a thyristor converter. 1...Synchronous machine, 2...Exciter, 3...Automatic voltage regulator, 4P...Thyristor converter, 4N...Thyristor converter, 5...Switch, 6... automatic tracking circuit,
31... Deviation detector, 32... Amplifier, 33...
Adder, 34... Gate pulse generator, 35... Switching logic circuit, 36... Polarity switching circuit, 37...
Bias signal circuit. 38...Interlock relay, 39...Nonlinear compensation Figure 2'54112]

Claims (1)

[Claims] 1. Of the excitation current required for the operation of a synchronous machine, positive or negative can be generated by an antiparallel combination of a circuit that supplies current during steady state and two sets of thyristor converters that convert alternating current to direct current. In an excitation control device equipped with a circuit that supplies a current for fluctuations, when the command signal to the circuit for controlling fluctuations is zero, the output voltages of the positive and negative thyristor converters are approximately equal to each other. An excitation control device for a synchronous machine, characterized in that a compensation signal corresponding to a predetermined gate firing angle that becomes zero is added to a gate pulse generator of each thyristor converter. 2. Claim 1 states that the device is provided with a circuit that switches the gate pulse firing angle compensation signal to an amount suitable for each circuit in conjunction with turning on and off of the circuit that supplies the variable current. Features: Excitation control device for synchronous machines. 3. Claim 1 is characterized in that a circuit having nonlinear characteristics that can be set for the firing angle region where the output current of the thyristor converter is intermittent is added to the front stage of the gate pulse generator. Excitation control device for synchronous machine.