JPS61157290A - Controlling method for power converter - Google Patents

Abstract

PURPOSE:To compensate the phase delay of an armature current command value generated when processed by a microprocessor by calculating and outputting armature current command values of phases at an angle added with a rotary position detected by the delay phase angle. CONSTITUTION:The rotating position theta of a synchronous motor 1 output from a counter 7 is applied to a differentiator 10 and an adder 12. The differentiator 10 differentiates the rotary position theta, i.e., the operating frequency (f) and outputs it. The frequency (f) is multiplied by a multiplifer 11 by constant 2pi.TL. In other words, the delay phase angle thetaL is output from the multiplier 11. This delay phase angle thetaL is added by an adder 12 by the rotary position theta. This added angles theta+thetaL is used to output unit sinusoidal wave of 120 deg. phase difference from ROMs 8U, 8V, 8W, multiplied by the amplitude command I* by D/A converters 9U, 9V, 9W to produce current command values iu*, iv*, iw*.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention digitally calculates the output current command value of a power conversion device such as an inverter that drives a synchronous motor using a microprocessor, and converts it into an analog value through a digital/analog converter. The present invention relates to a method of controlling a power conversion device that outputs a signal.

[Technical Load Lifting of the Invention and Its Problems 1 In recent years, control circuits are being digitized due to their good reproducibility and reliability. Control circuits for power conversion devices are no exception, and a circuit in which part of the control for driving the three-phase synchronous motor shown in FIG. 3 by the power conversion device is digitized is shown as an example.

In Figure 3, 1 is a three-phase synchronous motor, 2 is a synchronous motor 1
11 is a power conversion device that supplies armature currents +, iv, and iw; 3 is a pulse oscillator that is directly connected to the rotor of the synchronous motor 111 and outputs a pulse every time it rotates by a predetermined angle; 4 is a pulse oscillator Frequency/voltage (F/V) that outputs a voltage proportional to the frequency of output pulse P in step 3
) converter, 5 is the speed command ω0 and the output ω of the F/V converter 4
A comparator 6 is a speed control circuit that outputs the amplitude of the armature current to be supplied to the synchronous motor 1 according to the comparison result of the comparator 5. 7 is a counter 8U that counts the output pulses P of the pulse oscillator 3;

8V and 8W are read-only memories (RO
M), 9U, 9V, 9W are
ROM8U.

This is a digital/analog (D/A) converter that has a function of multiplying a unit sine wave digital signal outputted from 8V, 8W and a current amplitude command 1' outputted from the speed control circuit 6. The outputs iu', iv', and iw' of the converters 9U, 9V, and 9W are given to the power conversion bag-2 as armature current command values for each phase of the synchronous motor 1.

The power conversion device 2 has three-phase current command values iu'' and iv'.

The armature current of each phase following iw, iu, tv, i
It supplies W to the synchronous motor 1, and is composed of, for example, a transistor inverter and its instantaneous current control circuit, but since it is well known, a detailed explanation thereof will be omitted.

In FIG. 3, the pulse oscillator 3 and the F/V converter 4 detect the speed ω of the synchronous motor 1, and the pulse oscillator 3 and the counter 7 detect the rotational position θ. The detected speed ω is compared with the command value ω0 by the comparator 5, and according to the comparison result, the speed control circuit 6 outputs a general width command (==) for the necessary armature current.On the other hand, the counter 7 3 ROM8 according to the rotor position θ of the synchronous motor 1
u.

A medium sine wave with a phase difference of 120° is output from 8V and 8W, and is multiplied by the amplitude command ■0 in the D/A converter 9U, 9V, and 9W to obtain the analog current command value +',
iv' and iw' are obtained. That is, ROM8U
, 8V, 8W are the same Ill motor 10 rotor 11 pole position (
θ), the synchronous motor 1 outputs a sine wave signal that is always synchronized with the current amplitude command ■
Outputs torque proportional to the shaft.

When the control circuit is configured with individual digital circuit components as described above, even if the operating frequency becomes high, the phase of the current command value with respect to the rotational position θ will not be delayed. However, recently, the functions of the ROMs 8U, 8V, and 8W in FIG. 3 are often replaced with microprocessors. With the table reference function of the microprocessor, sine waves for three phases can be obtained from one sine wave table, and the circuit can be miniaturized. Further, a major advantage of using a microprocessor is that it becomes possible to provide highly flexible sequence processing and device diagnostic functions.

However, processing by a microprocessor
Since the process is performed step by step, a certain amount of time is required to execute the series of processes.

For example, when the functions of ROMs 8U, 8V, and 8W shown in FIG. 3 are processed by a microprocessor, the processing is performed in the following order.

(1) Read the rotational position θ from the counter 7.

(2) Obtain U-phase sine wave data corresponding to the rotational position θ from the sine wave table in the microprocessor memory.

(3) Output the U-phase sine wave to the D/A converter 9U.

(4) Obtain the ■ phase sine wave data from the sine wave table with the phase subtracted by 1206 from the rotational position θ.

(5) Output the ■phase sine wave to the D/A converter 9V.

(6) Obtain W-phase sine wave data from the sine wave table with a phase subtracted by 240° from the rotational position θ.

(7) Output the W-phase sine wave to the D/A converter 9W.

Since the processing is executed step by step in this way, there is a time delay between reading the rotational position θ and the counter 7 and outputting the sine waves of each phase to the D/A converters 9U, 9V, and 9W. arise.

Furthermore, since these processes are executed alternately with other processes such as sequence processing, they are repeatedly executed at predetermined intervals depending on the amount of processing. For this processing cycle, the rotational position θ
This causes a delay in the sine wave phase of each phase.

FIG. 4 is a time chart for explaining these sine wave phase delays, and shows the sine waveform for the negative phase. (a) shows the processing timing of the microprocessor, (b) shows the sine waveform when the frequency is low, and (C) shows the sine waveform when the frequency is high. The output waveform is
The dotted line is the output waveform of a circuit constructed from individual circuit components without delay, shown for comparison.

In FIG. 4, the rotational position θ is read at time t1, and a sine wave corresponding to θ is output at time t2 after a microprocessor processing time Td. Thereafter, a new rotational position is read at time t3, and a new sine wave is output at time t4. After that, Zhou Ff! It is repeated every Tp. (b
) and (C), the phase delay of the sine wave output by the microprocessor is divided into two time delays. One is the processing time Td from reading the rotational position θ to outputting the sine wave, and the other is the delay due to the processing time Tp. Once peaked, the sine wave passes through a period Tp and is held by the D/converter until the next sine wave is output. The delay for this is half the output period (To/2). Therefore, the total delay time TL of the output by the microprocessor is given by the following equation.

TL-=rd+Tp/2...Equation (1) Even if this delay time TL exists, there is almost no phase delay when the operating frequency is low as shown in Figure 4(b), so there is no problem. It doesn't happen. However, the higher the frequency of operation, the more the sine wave for rotational position θ becomes
, 9W output current command value iu', i
The phases of v' and iw' are delayed. For this reason, it is no longer possible to supply the synchronous motor 1 with an armature current having a phase corresponding to the rotor magnetic pole position θ, and the output torque decreases. As a result, the required output of the synchronous motor 1 is
1 cannot be obtained, and there is a limit to high frequency operation.

Recently, there has been a trend to increase the rotation speed of electric motors in order to obtain high output, and the upper limit of the required operating frequency is becoming higher. Therefore, it is required that the armature current phase with respect to the rotor position is not delayed even in a high operating frequency range.

[Object of the invention] The present invention has been made in view of the above background,
It is an object of the present invention to provide a control method for a power conversion device that prevents the phase of armature current from being delayed with respect to the rotor magnetic pole position even in a high frequency operation region.

[Summary of the Invention] In order to achieve the above object, the present invention calculates a delayed phase angle from a delay time, and calculates an armature current command value for each phase using the angle obtained by adding the delayed phase angle to the detected rotational position. This output compensates for the phase delay in the armature current command value that occurs when it is processed by the microprocessor.

The delay time here is the time TL shown in equation (1), which is the processing time Td from the input of the rotational position θ to the microprocessor to the output of the current command value, and the half of the current output cycle of each phase o /2.

This delay time T is a value determined by the processing program of the microprocessor, and is a time that can be known in advance. The delay phase angle θ1 is calculated from the operating frequency and the delay time TL.

Now, if the operating frequency is + (Hz), the delay phase angle θ,
is calculated using the following formula.

θL=2π・j−TL (rad)・(21
By determining the phase of each phase current command value by the angle obtained by adding the delayed phase angle θ in the above formula to the detected rotational position θ,
Even if the operating frequency becomes high, it is possible to supply the synchronous motor with an armature current that does not lag behind the rotor magnetic pole position.

[Embodiments of the Invention] The present invention will be described in more detail below with reference to the drawings.

FIG. 1 is a configuration block diagram showing an embodiment of the present invention, and parts having the same reference numerals as those in FIG. 3 have the same functions, so a description thereof will be omitted.

Similar to FIG. 3, FIG. 1 shows a control device composed of individual parts, and the number of circuit elements numbered 10 to 12 is increased compared to the configuration of FIG. 3.

10 is a differentiator, 11 is a multiplier, and 12 is an adder. However, sine wave ROM8U, 8V, 8W.

Although the differentiator 10, multiplier 11, and adder 12 are realized by program software of a microprocessor, they will be described here as being composed of individual circuit components to make the processing contents clearer.

The rotational position θ of the synchronous motor 1 output from the counter 7 is given to a differentiator 10 and an adder 12. Differentiator 10
Then, the operating frequency f is calculated and output by differentiating the rotational position θ, that is, by using the difference between certain periods. The operating frequency f is multiplied by a constant 2π·TL in a multiplier 11. That is, the multiplier 11 outputs the delayed phase angle θ shown in equation (2). This delayed phase angle θ1 is determined by the adder 12 as the rotational position θ.
is added. Using this added angle θ+θ,
As in the case of Figure 3, 1 from ROM8U, 8V, 8W
A unit sine wave with a 20° phase difference is output, and the D/A converter 9
U, 9V, 9W are multiplied by the amplitude command I' to obtain the current command value of each phase +', 1v14. iw' is reduced by 1q.

In this way, since the sine wave of each phase is obtained at an angle that compensates for the delayed phase angle θ1-, even if the operating frequency becomes high, the phase of the NtR current supplied to the synchronous motor 1 with respect to the rotor magnetic pole position is There is no delay, and the output torque does not decrease.

Although FIG. 1 shows a case in which compensation is performed using the same delay phase angle θ for all three phases, the delay time of each phase may be different. The present invention can be easily applied even when the delay times of each phase are different, and FIG. 2 shows a block diagram of the configuration of one embodiment.

In FIG. 2, multipliers 11U, 11V, and 11W and adders 12U, 12V, and 12W are separated for each phase, and their numbers are the same as in the configuration of FIG. 1.

In other words, even if the delay time TL differs for each phase, the second
As shown in the figure, the delay time T for each phase, 11°TL■, TL
W and the operating frequency f are multipliers 11U, 11V,
Multiply by 11W and delay phase angle θL u+ θL for each phase
v, θLW are calculated, and the rotational position θ is added to the adder 12U.
, 12V, and 12W, the delay time can be compensated for each phase.

The calculation of the delayed phase angle explained above with reference to FIGS. 1 and 2 does not need to be performed in short cycles, but may be performed in accordance with the speed at which the operating frequency changes. Therefore, the processing load on the microprocessor required to implement the present invention is very small.

[Effects of the Invention] As explained above, according to the present invention, it is possible to remove the phase delay of the current command value caused by the processing of the microprocessor, and the microprocessor can be applied even to devices that operate at high frequencies. It becomes possible. Moreover, since the processing load on the microprocessor is small, the microprocessor can be made to perform many other processes, and the miniaturization of the circuit and the high functionality of the control device can be easily realized.

[Brief explanation of drawings]

FIG. 1 is a circuit block diagram showing one embodiment of the present invention, and FIG.
The figure is a circuit block diagram showing an embodiment of the present invention, FIG. 3 is a circuit block diagram showing an example of the configuration of a conventional control device, and FIG.
The figure is a time chart diagram for explaining delays caused by microprocessor processing. 1... Synchronous motor, 2... Power converter, 3...
Pulse oscillator, 4... F/V converter, 5... Comparator, 6... Speed control circuit, 7... Counter, 8U, 8
V, 8W...Read only memory (ROM), 9U
, 9V. 9W...Digital/analog (r)/A) converter, 1
0...Differentiator, 11, 11U, 11V, 11W...
Multiplier, 12, 12U, 12V, 12W...Adder.

Claims (1)

[Claims] The rotational position of a synchronous motor to which current is supplied from a power conversion device is detected, a current command value of a phase synchronized with the rotational position is calculated by a microprocessor, and the current command value is calculated by a microprocessor and then transmitted via a digital/analog converter. In what is output to the power conversion device, the average processing time (Td) from the input of the rotational position to the microprocessor to the output of the current command value, and the average output cycle of the corresponding current command value from the microprocessor. (
(Td+Tp/2)
) has means for calculating a signal proportional to a value obtained by multiplying the operating frequency of the power converter, and a signal obtained by superimposing the signal obtained by the calculating means on the rotational position is used as a phase angle of the current command value. A method for controlling a power conversion device, characterized in that the phase delay of a current command value caused by arithmetic processing of a microprocessor and a hold period of a digital/analog converter is removed by using the method as a control method for a power conversion device.