JPH0667264B2 - Current control device for thyristor motor - Google Patents

Description

The present invention relates to a current control device for a thyristor motor.

[Conventional technology]

FIG. 3 is a block diagram showing a current control device of this kind proposed by the applicant (Japanese Patent Application No. 62-571: hereinafter also simply referred to as a proposed device), and FIG. 4 explains its operation. FIG. 5 is a waveform diagram of each part for explaining the function of the firing angle control circuit.

In FIG. 3, the electric power converter on the motor side and the motor are collectively shown as a DC load 2. The main circuit DC current Ic is detected by the DC current detector 3 and matched with the set value Ir by the adder 4a, and the difference Ir-Ic is input to the PI controller 5 via the switch 7a. Switch 7a is PI controller 5
The output of the integrator is held, and it is held by setting the signal a to "1" as shown in FIG.
The output of the PI controller 5 is supplied to the V / α circuit 6 via the switch 7b.
Is input to. The switches 7b, 7c, 7d are for connecting the input of the V / α circuit 6 to the PI controller 5 or the semi-fixed voltage sources V _S , V _P as occasion demands, and are shown in FIG. E),
The switch is turned on by setting the signals b, c, and d to "1" as in (f). It should be noted that V _S and V _P are for fixing the input of the V / α circuit at the time of current fall and rise.

The V / α circuit 6, as shown in FIG.
_The thyristor firing angle is controlled to the angle α corresponding to _PI . An example of the U-phase firing pulse is shown in FIG. Note that the relationship between V _PI and α may be linear (solid line in FIG. 5A) or non-linear (broken line in FIG. 5A). The output of the V / α circuit 6 is connected to the gate of the thyristor rectifier 1, and the OR gate circuit 10 outputs the gate ON signal.
The OR is taken and input to the sequence circuit 9 as the signal g.
When the signal g is "1" as shown in FIG. 4 (i), the gate signal is input to any thyristor. Supplementary setting value I
r'is for knowing that the current Ic is just before reaching the set value Ir, and is notified to the sequence circuit 9 as the signal f by the adder 4b and the comparator 8a. Signal f
Becomes "1" when Ic> Ir 'as shown in FIG. The comparator 8b notifies the sequence circuit 9 that the current Ic has become zero as a signal e. The signal e becomes "1" when Ic = 0 as shown in FIG. The sequence circuit 9 controls sequence control for performing intermittent current start of the thyristor motor.

Now, in such a configuration, it is assumed that the current interrupting operation is started at time t ₁ shown in FIG. That is, the input of the V / α circuit is connected to V _S , and at the same time, the signal a is set to "1" to drive the switch 7a and hold the integrator output of the PI controller. At this time, assuming that sufficient time has passed since Ic = Ir, the integrator output is the counter electromotive force E of the DC load 2.
Equivalent to. The thyristor rectifier 1 outputs a negative voltage corresponding to V _S and reduces the current Ic to zero (point t _{2 in} FIG. 4).
When Ic = 0 is known from the signal e, the current Ic is increased by connecting the input of the V / α circuit to Vp after a certain period of time and causing the thyristor rectifier 1 to output a positive voltage equivalent to V _P (see FIG. 4). of
t ₃ points). When it is known from the signal f that Ic is just before reaching Ir, the input of the V / α circuit is connected to the PI controller (point t _{4 in} FIG. ₄ ). The PI regulator is held at a value equivalent to the DC load back electromotive force E, and is fired once at a firing angle corresponding to this (t ₅ point in Fig. 4), then the switch 7a is driven and the hold is released. Then, normal PI control is performed.

In this way, by appropriately setting Ir 'and V _P , the current Ic can quickly reach the set value Ir, and the steady state can be immediately set without overshoot. This method is particularly effective when the DC load has a large inductance component.

[Problems to be solved by the invention]

However, such a method has the following problems. FIG. 6 shows an equivalent circuit of a DC load. The back electromotive force E constantly changes depending on the field current of the motor, the rotation speed, or the operating state of the motor side power converter. When nonlinear compensation (α = cos ⁻¹ (V _PI )) of the thyristor rectifier is performed by the V / α circuit, the equivalent circuit of the entire main circuit can be represented as shown in FIG. Here, considering the current rise period (between t ₃ and t 4 in FIG. ₄ ) during the intermittent operation of the current, the initial current value is Ic = 0, and V = V _{PI in} the equivalent circuit of FIG.
-E, but since V _PI = V _{P is} constant, it can be expressed as V = V _P -E. Here, if V _P »E, can be obtained always the same current waveform regarded as VV _P, if the size of the E can not be ignored come different from one that by connexion waveform of the value of E.
For example, FIG. 8 shows a current waveform when E changes in a control system adjusted to have an optimum waveform in the state of E = E ₀ . This means that when the magnitude of the back electromotive force E cannot be ignored, the current waveform changes due to the change in E as shown in FIGS. 8 (a) and 8 (c), so that the control system cannot be adjusted. Will have the problem.

Therefore, the present invention, in the current intermittent start operation of the thyristor motor, regardless of the change in the DC back electromotive force appearing in the DC terminal of the motor side power converter, it is possible to always obtain the same current rising waveform, The purpose is to enable good control.

[Means for solving problems]

First setting means for setting the input of the ignition angle adjuster to a first value represented by the sum of a preset value and a DC load back electromotive force equivalent value, an integrator output of the PI adjuster, and ignition. Second setting means for setting the input of the angle adjuster to a second value corresponding to the back electromotive force of the DC load, and that the converter output current exceeds a preset complementary current setting value (<current setting value) When the converter output current is increased from zero to its set value in order to start the current intermittent start of the thyristor motor, the ignition angle adjuster input is set to the first value. The current is increased, and when the current value exceeds the current supplementary setting value, the integrator output of the PI controller and the input of the firing angle controller are fixed to the second value, which corresponds to the second value. After performing the firing operation once at the firing angle to be set, shift the PI controller to the normal operation. .

[Action]

At the time of starting the current in the intermittent current starting operation of the thyristor motor, the counter electromotive force is output by outputting the voltage V _P + E represented by the sum of the preset voltage V _P and the counter electromotive force E to the power converter on the power source side. The influence of E is canceled and the same current waveform is always obtained to improve the control performance.

Example of Invention

FIG. 1 is a configuration diagram showing an embodiment of the present invention, and FIG. 2 is a waveform diagram for explaining its operation.

The difference from the proposed device shown in FIG. 3 is that an adder 4c is added. With this adder 4c, FIG.
When trying to increase the current from zero as shown in
The input of the / α circuit is set to a value obtained by adding V _P and the value E corresponding to the back electromotive force of the DC load, that is, V _PI = V _P + E. Therefore, in the equivalent circuit of FIG. 7, V = V _PI −E = V _P ,
The counter electromotive force E is canceled. In this way, by adjusting V _P and Ir ′ to be optimal under the condition of the back electromotive force E = 0, a constant current rising characteristic can be obtained under any back electromotive force.

〔The invention's effect〕

According to the present invention, the counter electromotive force E is canceled by setting the output voltage of the power supply side power converter at the time of current rise to the preset value of V _P and the DC load counter electromotive force E to cancel the counter electromotive force E. There is an advantage that a constant current rising characteristic can be obtained even under the counter electromotive force.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG.
FIG. 3 is a waveform diagram for explaining the operation of the figure, FIG. 3 is a configuration diagram showing a proposed device, FIG. 4 is a waveform diagram of each part for explaining the operation, and FIG. 5 is a function of a firing angle control circuit. Explanatory drawing for explaining, FIG. 6 is a circuit diagram showing an equivalent circuit of a DC load, FIG. 7 is a circuit diagram showing an equivalent circuit of the entire main circuit, and FIG.
The figure is a waveform diagram showing a change example of the current waveform when the DC load back electromotive force changes. Symbol description 1 …… Thyristor rectifier, 2 …… DC load, 3 …… DC current detector, 4a, 4b, 4c …… Adder, 5 …… PI regulator, 6
...... Ignition angle control circuit, 7a, 7b, 7c, 7d ...... Switch, 8a, 8b
…… Comparator, 9 …… Sequence circuit, 10 …… OR gate circuit, V _S , V _P …… Semi-fixed voltage source.

Claims (3)

[Claims] 1. A proportional-plus-integral controller (PI controller) for driving a thyristor motor through a power converter having a large reactor between a converter and an inverter so that the deviation between the converter output current and its current setting value can be adjusted. ), And inputting the output to the ignition angle controller to adjust the ignition angle of the converter to control the current, in the current control device of the thyristor motor, the input of the ignition angle controller is a preset value. And a DC load back electromotive force equivalent value, and a first setting means for setting a first value represented by the sum of the DC load back electromotive force and an input of the integrator output of the PI controller and the firing angle controller. A second setting means for setting a second value corresponding to the above, and a detection means for detecting that the converter output current exceeds a preset complementary current setting value (<current setting value), Thyristor motor power When increasing the converter output current from zero to its set value to initiate an intermittent start, the firing angle regulator input is set to the first value to increase the current, and the current value increases the current compensation. When the set value is exceeded, the integrator output of the PI controller and the input of the firing angle controller are fixed to the second value, and the firing operation is performed once at the firing angle corresponding to the second value. A current control device for a thyristor motor, characterized in that the PI controller is shifted to a normal operation after the operation. 2. The current control device for a thyristor motor according to claim 1, wherein the value immediately before the intermittent current operation is stored by means for storing the integrator output of the PI controller, and the value is stored. A current control device for a thyristor motor, which is used as the second value. 3. The current control device for a thyristor motor according to claim 1, wherein the value immediately before the current interrupting operation is stored by means for storing the output of the PI controller, and the value is stored as the second value. A current control device for a thyristor motor, which is used as a value of.