JPS61128784A - Controller for load rotating speed - Google Patents

Abstract

PURPOSE:To rapidly convert one to the other of power converters normally or reversely by obtaining an induced voltage indirectly by utilizing a firing angle, a current average value and a momentary current value at power converter switching time, thereby eliminating a detector. CONSTITUTION:Conversion preparing means 14 of a power converter stores in advance a relationship between a firing angle and the induced voltage of a load for a current average value over one period, obtains the induced voltage of a load from the actual firing angle value, the current average value and the momentary current value of a power converter during operation at that time when switching the power supplying direction of the converter, and forms the initial value 15 of the firing angle of the power converter after switching by utilizing the value. A current controller 4 starts the current control with the value as a firing command 5.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention drives a load such as a DC motor by supplying power from a power supply side through a first power converter to drive the load. If the rotational speed exceeds the set speed due to changes in the set speed or load fluctuations, the back electromotive force (induced voltage) of the load is greater than the power supply voltage applied via the first power converter. When the first power converter becomes high, the first power converter is switched to the second power converter connected in antiparallel to it, and power is regenerated from the load side to the power source side via this, thereby reducing the load. This relates to a load rotation speed control device that reduces the rotation speed so that it approaches a set speed, and more specifically, from the first power conversion device to the second power conversion device (or vice versa). The present invention relates to determining the initial value of the firing angle command value for the power conversion device after switching.

[Conventional technology]

In the above-mentioned load rotational speed control device, conventionally, when switching power converters to stop operation of one power converter and start operation of the other power converter, ignition of the internal power converter is used. After confirming that the current flowing between the power supply side and the load side is zero by setting the angle to the maximum, the power conversion device that is ignited is switched from one side to the other, and control of the ignition phase is started from the maximum phase. Ta.

However, this method has the disadvantage that the start-up of the control for bringing the rotational speed of the load closer to the set speed is delayed.

Therefore, the following methods have been attempted to solve this drawback. In other words, when switching the power converter from one side to the other and starting phase control of the power converter again, control is not started from the maximum phase position, but rather the voltage supplied from the power supply side to the load side via the power converter In this method, phase control is started from the firing angle of the power converter at which the voltage is exactly equal to the induced voltage of the load.

However, even with this method, if it is based on the conventional method, there are drawbacks as described below. This will be explained in detail below.

FIG. 3 is a block diagram showing a conventional example of an anti-parallel thyristor Leonard device as a load rotation speed control device as described above.

In the figure, 1a is a speed command value, ■b is a speed feedback value,
2 is a speed control circuit, 3a is a current command value, 3b is a current feedback value, 4 is a current control circuit, 5 is a firing angle command, 6 is a phase control circuit, 7a and 7b are each a firing command, 8 is a three-phase AC power supply, 9 is a current detection device, 10.11 is a power conversion bag connected in antiparallel to each other! (thyristor device), 12 is a load (for example, a DC motor), and 13 is a speed detection device.

FIG. 4 is a block diagram showing details of the current control circuit 4 in FIG. 3. In the figure, R1 to R5 are resistors, C1 is a capacitor, SWI to SW3 are contacts, and oP is an operational amplifier.

Please refer to FIGS. 3 and 4. Normally, contact SWI is closed, contacts SW2 and SW3 are open, and current control circuit 4 is
It operates as an I regulator.

That is, the speed control circuit 2 receives the speed command value 1a and the speed feedback value 1b (the value detected by the detection device 13 of the rotational speed of the load 12), and outputs the current command value 3a related to the deviation thereof. In the current control circuit 4, the current command value 3a
and the current feedback value (current value detected by the current detection device 9) 3b are input, and the output obtained by performing PI calculation on the deviation is created as the ignition command 5 and supplied to the phase control circuit 6. In the phase control circuit 6, according to the ignition command 5,
The power conversion device selected at that time (10 and 1)
1) in order to make the rotational speed of the load 12 match the speed command value 1a.

Next, if the polarity of the current command value 3a changes due to a change in the speed command value 1a or a load fluctuation, the current control circuit 4
At , contact SWI is open, and contacts SW2 and SW3 are closed. At this time, the current control circuit 4 outputs a speed feedback value of 16
It becomes a proportional circuit including a delay circuit which takes as an input signal, and makes the firing angle command 5 match a value proportional to the speed feedback value 16,
After switching from one of the power converters 10 and 11 to the other, phase control of the power converter is started again using the command value 5 as the initial value.

Such an operation makes it possible to control the phase control angle of the newly selected power conversion device after switching from the point where it becomes equal to the induced voltage of the load 12. However, the conventional method as described above has the following drawbacks.

(1) The induced voltage in the load is proportional to the product of magnetic flux and rotational speed, so if the magnetic flux is constant, it will be proportional to rotational speed, so there is no problem with the above method of using the speed feedback value. . However, when speed control is performed to increase the rotational speed by weakening the magnetic flux, the induced voltage and the rotational speed are no longer proportional. Although it is necessary to correct the induced voltage and the rotational speed (speed feedback value 1b) by the amount by which it has been weakened, it is difficult to take measures for this purpose.

(2) If the induced voltage of the load 12 is used as the direct input signal to the current detection circuit 4 instead of the speed feedback value 1b, the above (1) can be achieved.
However, it requires a separate circuit to detect the induced voltage, which is expensive.

(3) The above-mentioned example of an anti-parallel thyristleonard device is based on an analog circuit. Even if this is achieved using a digital circuit such as a microcomputer,
Problems +1) and +2) mentioned above exist, and even if these problems were to be solved, a separate analog-to-digital conversion circuit would be required, which would be expensive. For example, in the case of (1) above, the problem can be solved by detecting the field current to detect the magnetic flux, and in the case of (2) above, the problem can be solved by detecting the load voltage. At that time, analog
A digital conversion circuit will be required.

[Problem that the invention seeks to solve]

Therefore, the problem to be solved by the present invention is that in a load rotation speed control device such as an anti-parallel thyristor Leonard device, even when control is performed to weaken the magnetic flux and increase the rotation speed, a magnetic flux correction means is provided. or without preparing a separate induced voltage detection circuit (
In other words, if the load rotation speed control device is implemented using a digital circuit, additional analog
It is possible to control the phase control angle of a newly selected power converter after switching from the point where it becomes equal to the induced voltage of the load, without requiring a digital conversion circuit (that is, at a low cost). It can be said that this is true.

Therefore, an object of the present invention is to provide a load rotation speed control device that makes the above possible.

[Means and effects for solving the problem] This invention has the following features:
The induced voltage of a load connected to the power supply side via the power conversion device is determined by the firing angle of the power conversion device and the average value (average value over one cycle) of the current flowing between the load and the power source side. , and the relationship differs depending on whether the current is in a continuous state or in an intermittent state, and the relationship between the firing angle and the average current value over one cycle is memorized in advance. , when switching the power supply direction of the power converter (that is, when switching from one power converter to the other of two power converters connected in antiparallel), the actual value of the firing angle of the power converter currently in operation. The induced voltage of the load is determined from the average current value and the instantaneous current value, and this value is used to determine the initial value of the firing angle of the power converter after switching.

That is, the induced voltage Edc of the load, the firing angle α of the power converter, the average current value Id, and the instantaneous current value iI+ at the time of firing.
- The relationship between the instantaneous current value 12 after a period (60 degrees in electrical angle) is based on the commutation type phenomenon, since there is no practical problem even if the induced voltage Ed of the load is assumed to be almost constant during one period. If it can be ignored, in a continuous current state, it is generally given by the following equation (note that the firing angle α is

The relationship between the average current value Id and the instantaneous current value il at the time of ignition + the same instantaneous value 12 after one cycle is shown in FIG.

πRR (iz it) ・-・tanyπ・・・・・・(1) However, EΔ: Effective line voltage value of AC power supply R: Armature circuit resistance of load (e.g. DC motor) tanψ8 ω is AC power supply angle Frequency, L is the armature circuit inductance of the load. In the current intermittent state, if the current conduction angle is ωL0, then the firing angle α and the current intermittent limit value Idc (if the current value is greater than Idc, the current is in a continuous state) The relationship between the current value (which indicates the limit that an intermittent state will occur if it is below Edc) is, however, −sin (−1ψ+α)・ε−7%mnW )/(
1-ε-1/Lanψ), and if the current intermittent limit value for a certain firing angle α is Io, - represents the ratio of d to the average current value Id over one cycle, which is given by the following formula, where O -XI2 EΔ 3- sin
(--ψ+α) ・ε-No.'t! 1/(1-ε-fi' to No. 8) d Assuming that the current is not intermittent, - is the following I.

It is given by Eq.

......(4) Figure 6 is a characteristic diagram showing the relationship between rdc and α obtained from the above equation (2) for the case of cos p = 0.5, where the shaded area is the current cutoff Vt5I area, The other areas indicate the current-related Vt region.

Figure 7 shows cosp-0,5 from equations (3) and (4) above.
, the relationship I between □ and Δα obtained for the case where CX=d 90 degrees.

FIG. That is, Id/I.

When is between 0 and 1, the current is in an intermittent state, and this shows the magnitude of the firing angle correction amount Δα at that time.

If these relationships are memorized and the actual firing angle, average current value, and instantaneous current value 11+12 are given at the time of switching the power converter, the relationship shown in Figure 6 will determine whether the current is continuous or intermittent. If the continuous state is to be assumed, the correction amount Δα of the firing angle α at that time is calculated from the relationship shown in Equation 11 above, and even in the case of an intermittent state shown in Fig. 7, and the firing angle is determined as follows. By the formula α=α−Δα
......(5) Find the firing angle that can be equivalently considered as a continuous state after correction, find the induced voltage in the load from the relationship in equation (1) above, and use the firing angle that corresponds to this value. The control is started.

〔Example〕

FIG. 1 is a block diagram showing one embodiment of the present invention. In the figure, the same symbols (1 to 13) as in Figure 3
indicate the same thing. In addition, 14 indicates switching preparation means for the power converter, and 15 indicates an initial value of a firing angle command for the power converter after switching.

FIG. 2 is a block diagram showing details of the switching preparation means 14 in FIG. 1.

In the figure, 16 is an OR means, 17 is a gate means,
18 is a switching determination means, 19 is a one cycle detection means, and 20 is a
Current average value detection means, 21 is a holding means, 21a is a firing angle, 22 is a holding means, 22a is an instantaneous current value i+, 23 is a holding means, 23a is an instantaneous current value 1-124 is a holding means, 2
4a is a current average value 1d, 25 is an intermittent limit detection means, 25
a is an intermittent limit value io, 26 is a correction means, 26a is a correction angle Δα, 27 is a subtraction means, 27a is a firing angle, and 28 is a calculation means.

Please refer to FIGS. 1 and 2.

The gate means 17 normally passes the ignition pulse signals (ignition commands) 7a and 7b logically summed by the OR means 16, and the holding means 22 holds the instantaneous current value at the time of ignition based on the signal, and The one cycle detection means 19 starts its operation.

Now, when switching the power converter, that is, when a change in the polarity of the current command value 3a is detected, the current control circuit 4 sets the firing angle command 5 to the maximum phase angle.

Therefore, when the switching determination means 18 detects a change in the polarity of the current command value 3a, it causes the holding means 21 to hold the firing angle command 5 and stops the operation of the gate means 17 before the current control circuit 4 operates. make it stop.

1 cycle detection means] 9 is the electrical angle after 60 degrees, the holding means 2
3.24 is operated to hold the instantaneous value of the current and the data of the current average value detection means 20 that detects the average value of the current over one cycle. The intermittent limit value detection means 25 stores the intermittent current limit value obtained in advance from the above relational expression (2) in its own memory, and calculates the intermittent current limit value (Io) corresponding to the firing angle 21a. Find 25a.

The correction means 26 stores data of a correction angle (Δα) for the ratio (Id/Io) between the current intermittent limit value I0 and the current average value Id, which has been obtained in advance from the above relational expression (31, +41), in a stored memory. Memorize the current intermittent limit value (I
o) Obtain Id from memory from 25a and current average value 24a. At this time, if 2 is larger than 1, that is, if the current is continuous, the correction angle 26a
is set to zero. The subtraction means 27 subtracts the correction angle 26a from the firing angle 21a, and the calculation means 28 calculates the firing angle 27a, the average current value (Id) 24a, the instantaneous current value (i,) 22a,
(it) From 23a, the counter electromotive force (E dc) of the load is determined using the above relational expression (1), and an initial firing angle value 15 corresponding to this value is created.

The current control circuit 4 starts current control using this value as the firing angle command 5.

With the above operation, when changing the direction of current feeding between the load 12 and the power source 8, the switching operation of the power conversion device can be performed quickly.

〔Effect of the invention〕

According to the present invention, in a load rotation speed control device such as an anti-parallel thyristor Leonard device, ignition occurs when switching a power converter device (thyrisk device) without directly detecting the induced voltage of the load (for example, a DC motor). By indirectly determining the induced voltage using the angle, average current value, and instantaneous current value, a detection circuit can be eliminated, and the initial value of the firing angle after switching can be set to a value commensurate with this induced voltage. Thereby, even in a state where the magnetic flux is weakened, forward and reverse switching from one side of the power converter to the other can be quickly performed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a block diagram showing details of the switching preparation means 14 in FIG. 1, and FIG. 3 is a block diagram showing a conventional example of an anti-parallel thyristor Leonard device. , FIG. 4 is a block diagram showing details of the current control circuit 4 in FIG. 3, FIG. 5 is a waveform diagram showing the current waveform when the power converters 10 and 11 are switched in FIG. 3, and FIG. Figure 7 is a characteristic diagram showing the relationship between the current intermittent limit value Idc and the firing angle α in the power converter, and when the current is in an intermittent state in the power converter, it is equivalently regarded as being in a continuous state. A characteristic diagram showing the magnitude of the firing angle correction amount Δα used when determining the firing angle to be adjusted,
It is. Code explanation 1a...Speed command value, 1b...Speed feedback value, 2...
- Speed control circuit, 3a... Current command value, 3b... Current feedback value, 4... Current control circuit, 5... Firing angle command, 6... Phase control circuit, 7a, 7b.・・Ignition command,
8... Three-phase AC power supply, 9... Current detection device, 10.
II...Power converter, 12...Load, 13...
Speed detection device, 14... Switching preparation means, 15... Initial firing angle value after switching, 16... Logical sum means, 17...
- Gate means, 18...Switching determination means, 19...1
Period detection means, 2o... Current average value detection means, 21~
24... Holding means, 25... Intermittent limit detection means, 2
6...Correction means, 27...Subtraction means, 28 is calculation means agent Patent attorney Akio Namiki Agent Patent attorney Kiyoshi Matsuzaki 1b Uri 4 figure 16 al1 1g7 figure

Claims (1)

[Claims] 1) A first power converter that receives ignition phase control and supplies power from the power source to the load, and a second power conversion device that also receives ignition phase control and regenerates power from the load to the power source. a power conversion device;
Means for comparing a command value and an actual value of the rotational speed of the load and selecting either the first or second power converter according to the polarity of the deviation, and the selected power converter. means for controlling the ignition phase so as to eliminate the deviation; means for detecting an average value over one cycle of the current flowing between the load and the power supply; means for detecting the instantaneous value of the current, and voltage calculation means for calculating and outputting the induced voltage of the load at that time from the average value and instantaneous value of the current and the actual value of the firing angle in the power converter in operation; In response to a change in the polarity of the deviation, when performing selection switching from one power converter to the other power converter, a firing angle command value for the newly selected power converter is determined. A control device for a load rotation speed, characterized in that the initial value is determined by the load induced voltage at that point in time determined by the voltage calculation means.