JPH022398B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field to which the Invention Pertains] The present invention provides a method for controlling the firing pulse interval of a semiconductor element in a power converter whose load is an AC motor based on a command value given for controlling the speed of the motor. The present invention relates to an ignition pulse control method for controlling ignition pulses.

[Prior art and its problems]

Vector control methods tend to be widely adopted as control methods that enable high-speed response in speed control of induction motors and the like. By the way, when a current-source inverter device is used as a power converter, and in vector control of an induction motor supplied with power by the inverter device, the output frequency (inverter frequency) to be supplied from the inverter device to the motor and the magnetic flux of the motor are The originally desired phase angle β of the primary current vector from the vector (magnetic flux axis) is given as a command value for motor speed control from the vector control device, and the firing pulse of the thyristor in the inverter device is generated according to these command values. Interval (firing phase)
A control method is known that calculates and controls.

However, in such conventional control methods, a microcomputer (hereinafter referred to as
(also referred to as a microcomputer) needs to rapidly repeat and calculate the ignition phase according to the inverter frequency and current vector phase angle (hereinafter simply referred to as current phase angle) β given as command values. , a microcomputer with a high calculation processing speed is required, and there is less room for the microcomputer to be used for other calculation processing, resulting in a decrease in its utilization.

[Purpose of the invention]

The present invention has been made in order to eliminate the drawbacks of the prior art as described above, and therefore, an object of the present invention is to enable a microcomputer to perform fast repetitive calculations in accordance with command values given from a vector control device or the like. The object of the present invention is to provide an ignition pulse control method that can output an ignition pulse with a desired phase without requiring any additional steps.

[Key points of the invention]

The main point of the configuration of the present invention is that a computing device reads a command value given for speed control of the motor and calculates the firing pulse interval for on/off control of a semiconductor element in a power converter that supplies power to an AC motor. and a counter that counts clock pulses,
and a latch for reading the counted value of the counter into the arithmetic unit, and the arithmetic unit converts the firing pulse interval determined by the calculation into the required number of clock pulses, and sets the converted value as a set value. is set in the counter, and when the counter has counted the set value, the counter generates a first interrupt signal and inputs it to the arithmetic unit, and the arithmetic unit controls the output pattern of the ignition pulse accordingly. In addition, in the ignition pulse control method that reads the command value at that time and operates in the same manner thereafter, the first
inputting into the arithmetic unit a second interrupt signal that occurs at a constant cycle shorter than the generation cycle of the interrupt signal;
Each time the arithmetic unit receives the second interrupt signal, it reads the command value and also reads the count value of the counter at that time via the latch, and if the read command value is different from the previous command reading value. When the difference is detected, the read counter count value is corrected and reset to the counter according to the difference.

[Embodiments of the invention]

Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention. In the figure, 1 is a power converter (for example, a current source inverter device), 2 is an induction motor, 3 is a microcomputer, 4 is a pulse amplifier, 5 is a latch, and 6 is a counter. Moreover, β and f ₁ are the current phase as a command value output by a vector control device (not shown) for speed control given the actual values of the rotational speed and current of the electric motor 2, and the command value of the rotational speed. angle (β) and inverter frequency (f ₁ ).

FIG. 1A is an operational waveform diagram of each part in the circuit of FIG. 1.

FIG. 2 is a circuit diagram showing an inverter circuit of the inverter device as the power converter 1 in FIG. 1. In the same figure, Th _R , Th _S , Th _T , Th _X ,
Th _Y , Th _Z indicate thyristors, D _R ,
D _S , D _T , D _X , D _Y , and D _Z each represent a diode.

FIG. 2A is a time chart showing an example of the waveform of the gate firing pulse of each thyristor in FIG. 2; The main thyristors are Th _R , Th _Z , Th _S ,
_{Th _ _}

Next, the circuit operation will be explained with reference to FIGS. 1 to 2A.

First, the ignition pulse given from the microcomputer 3 to the power converter 1 via the pulse amplifier 4 is
As shown in the figure, there are six phases for one cycle of the inverter frequency _f1 . If the command value of the inverter frequency f ₁ given to the microcomputer 3 is constant,
If the command value of the current phase angle (β) with respect to the magnetic flux axis does not change, the ignition pulses are output with a phase difference of 60° in electrical angle.

Now, if the period of the clock pulse given to the counter 6 from a clock generation source (not shown) is t _c , then at a certain inverter frequency f ₁ , the electrical angle
The count setting value N _i of the counter 6 for determining the time point every 60° is given by the following equation (1).

N _i =1/6f ₁ t _c ...(1) In other words, the counter 6 converts the clock pulse to N _i
The time required to count up the number is equivalent to 60 degrees of electrical angle. If the command value β changes, and this change is defined as Δβ, the number of clock pulses to be counted corresponding to this Δβ is added to the count setting value determined by equation (1) above, and the new setting value is calculated. It's fine. The number of clock pulses to be counted corresponding to Δβ is given by the following equation (2).

Nβ=Δβ/K ₃₆₀ ·f ₁ ·t _c (2) where K ₃₆₀ is a constant representing the amount of command value β corresponding to 360° electrical angle.

Therefore, if each command value of inverter frequency f ₁ and current phase angle β is given at a certain point in time, the count setting value N that the counter 6 should count by the time of the next ignition pulse is given by the following equation (3). It will be done.

N=N _i +Nβ=1/6f ₁ t _c +Δβ/K ₃₆₀・f ₁
・t _c =(1/6+Δβ/K ₃₆₀ )1/f ₁ t _c (3) Therefore, the microcomputer 3 can obtain the count setting value N and set it in the counter 6. Assume now that at time _t0-1 in FIG. 1A, the counter 6 counts up the set value N, inputs the interrupt signal D to the microcomputer 3, and the microcomputer 3 outputs an ignition pulse. At the same time, the microcomputer 3 reads the inverter frequency _f1 and current phase angle β at that time. The microcomputer 3 calculates the change Δβ with respect to the current phase angle β at the time when the previous interrupt signal was generated, calculates the count setting value N according to equation (3), sets it in the counter 6, and starts counting.

_Next , when a periodic interrupt signal C is input at time to, the microcomputer 3 outputs a latch signal G, latches the current value _Mo of the counter 6 into the latch 5, and reads it.
Also, at that point, the inverter frequency _f1 and the command value β of the current phase angle are read, and the count setting value N is calculated similarly according to the above equation (3). Next, find the difference ΔN _o from the count setting value N that was set last time,
It adds it to the current value M _o of the counter 6, sets (M _o +ΔN _o ) as a new count setting value in the counter 6, and restarts counting.

The same procedure is performed at time t _o+1 .

At time t _o+2 , the counter 6 counts up, and the interrupt signal D enters the microcomputer 3.
determines the current firing pulse pattern with respect to the previous firing pulse pattern according to the polarity of the inverter frequency. That is, in the explanatory diagram of the firing pulse pattern shown in FIG. 3, it is assumed that the firing pulse is outputted in pattern 2 to each of the thyristors Th _R to Th _Y at time t _o-1 . If the polarity of the inverter frequency is positive when the count setting value is calculated at the time t _o+1 , the ignition pulse is output in pattern 3, which is advanced by one at the time t _o+2 . Conversely, when the polarity of the inverter frequency is negative, the firing pulse is output according to pattern 1. If the polarity is positive, pattern 5 is followed by pattern 0; if it is negative, pattern 0 is followed by pattern 5. However, in FIG. 3, 1 indicates on and 0 indicates off. FIG. 4 is a flowchart showing this procedure.

That is, FIG. 4a is a flowchart showing the flow of operations when activated by the periodic interrupt signal C. FIG. 4b is a flowchart when activated by the interrupt signal D due to the count-up of the counter 6. Regarding interrupts, an interrupt D caused by the count up of the counter 6 has priority over a fixed period interrupt C.

As a result, the microcomputer can perform the desired ignition pulse control without performing rapid repetitive calculations, and the microcomputer performs other calculation processing except when the procedure shown in Figure 4 is being executed. It is also possible to increase the utilization of the microcontroller.
Furthermore, if a vector control device as a motor control device is incorporated into a microcomputer and DDC (digital direct control) is performed, data can be easily exchanged between the two.

〔Effect of the invention〕

According to this invention, the hardware configuration for controlling the ignition pulse using a microcomputer is as follows.
This has the advantage of being simpler than the conventional technology.

In addition, the microcomputer calculates the time interval between firing pulses given to the inverter from the command values of the inverter frequency _f1 and current phase angle β, and the time is counted by a counter attached outside the microcomputer, and when the count up By determining and outputting the ignition pulse using the generated interrupt, the calculation time required for the microcomputer to control the ignition pulse can be reduced, and even a microcomputer with relatively slow calculation processing can perform control. The interval between processing by an interrupt and processing by the next interrupt can be used for arithmetic processing other than ignition pulse control, which has the effect of increasing the utilization of the microcomputer.

In addition, if a motor control device (vector control device) is incorporated into a microcontroller and realized with DDC, the connection between the two can be realized without going through a D/A converter, which is required when using a conventional ignition pulse control circuit using an analog circuit. You can easily send and receive data.

Furthermore, by using fixed period interrupts, the count setting value of the counter 6 can be corrected even in response to changes in the current phase angle command value between ignition pulses and changes in the inverter frequency command value. You can expect fast control response.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention;
1A is a waveform diagram of each part in the circuit of FIG. 1, FIG. 2 is a circuit diagram showing an inverter circuit of an inverter device as the power converter 1 in FIG. 1, and FIG. 2A is a diagram of each thyristor in FIG. 2. A time chart showing an example of the waveform of the gate control signal, Fig. 3 is an explanatory diagram of the firing pattern of each thyristor in Fig. 2, and Fig. 4 a shows the flow of operation when activated by a fixed period interrupt signal. FIG. 4B is a flowchart showing the flow of operations when activated by an interrupt signal due to count-up. Description of symbols, 1... Power converter (current source inverter device), 2... Induction motor, 3... Microcomputer,
4...Pulse amplifier, 5...Latch, 6...Counter.

Claims (1)

[Claims] 1. A computing unit that reads a command value given for speed control of the motor and calculates a firing pulse interval for on/off control of a semiconductor element in a power converter that supplies power to an AC motor; , a counter for counting clock pulses, and a latch for reading the counted value of the counter into the arithmetic unit, and the arithmetic unit converts the firing pulse interval determined by the calculation into the required number of clock pulses. Then, the converted value is set in the counter as a set value, and when the counter has counted the set value, it generates a first interrupt signal and inputs it to the arithmetic unit, which then turns on. In an ignition pulse control method that controls the output pattern of the arc pulse and reads the command value at that point in time and operates in the same manner thereafter, the arc pulse is generated at a constant cycle shorter than the generation cycle of the first interrupt signal. A second interrupt signal is input to the arithmetic unit, and each time the arithmetic unit receives the second interrupt signal, it reads the command value and reads the count value of the counter at that time via the latch. If the read command value is different from the previous command read value, then according to the difference,
A firing pulse control method for a semiconductor element in a power converter, characterized in that the read count value of the counter is corrected and reset to the counter.