JPS62144576A - Pwm pulse motor - Google Patents

Abstract

PURPOSE:To obtain the pulse of high precision from a simple organization, by a method wherein trapezoidal wave signal obtained from the sliced signal of triangle wave signal and sine wave signal combined with each other are kept in memory, and wherein the signal is read, and wherein it is compared with that of a specified level to obtain PWM pulse. CONSTITUTION:Triangle wave signal and sine wave signal are combined with each other, and trapezoidal wave signal obtained from the combined signal sliced on a specified level is stored at a ROM5. Signal stored at the ROM5 is read by a frequency generator 2 and a counter 3 at a speed corresponding with the frequency of an inverter, and by comparing the signal with the value of a level corresponding with a modulation factor from the resistor 6 of the modulation, with a comparator 7, PWM pulse is obtained.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a PWM method in a PWM type inverter device.
The present invention relates to a pulse generator, and particularly to a PWM pulse generator suitable for a VVVF type inverter device for a vehicle.

[Background of the invention]

In trains and other vehicles that use an AC motor such as an induction type AH machine as a propulsion motor, VVV is used to drive the motor.
An F-type inverter device may be used.

Incidentally, such an inverter device requires a PWM pulse generator, and a conventional example of such a PWM pulse generator is, for example, Japanese Patent Laid-Open No. 55-564.
02, the basic idea of this conventional example is that, as shown in FIG. 3(a), a triangular wave signal A synchronized with a frequency that is an integral multiple of the inverter frequency,
A PWM pulse signal as shown in FIG. 3(b) was generated by comparing it with a sine wave signal B synchronized with the fundamental wave of the inverter frequency (the frequency desired to be generated).

However, in this conventional method, this Fig. 3(a)
It has been widely used in recent years because it is necessary to generate a triangular wave signal synchronized with a frequency that is an integer multiple of the inverter frequency, as shown in A in the figure, and a sine wave signal whose amplitude and frequency are variable, as shown in B in the same figure. When applied to a computer-controlled system, there are problems with the interface with the computer and compatibility with digital processing, and there are drawbacks such as a complicated circuit configuration.

[Purpose of the invention]

An object of the present invention is to provide a PWM pulse generator for a VVVF type inverter if, which is easy to interface with a computerized system, has a simple configuration, and can easily generate high-precision pulses. .

[Summary of the invention]

In order to achieve this object, the present invention combines a triangular wave signal and a sine wave signal, then stores a trapezoidal wave signal obtained by slicing this combined signal at a predetermined level, and converts this signal into an inverter. It is characterized in that the PWM pulse is obtained by periodically reading out at a speed corresponding to the frequency and comparing it with a level value corresponding to the degree of modulation.

[Embodiments of the invention]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The PWM pulse generator according to the present invention will be described in detail below with reference to illustrated embodiments.

FIG. 1 shows an embodiment of the present invention. In the figure, 1 indicates the inverter frequency finν required to control the inverter.
, modulation degree VC%, pulse mode Pm, etc., is a system control unit composed of a microcomputer. 2 is a frequency generator which inputs data finv supplied from the system control unit 1 and outputs this data. A device that functions to generate a clock with a frequency fcp proportional to the frequency, 3 a counter that counts the clock of this frequency fCp, and 4 a ROM 5 which will be described later after receiving data Pm.
5 is a ROM (read only memory) for storing a trapezoidal wave signal, which will be described later. 6 receives data Vc given from the system control unit 1 and outputs it. modulation depth register,
And 7 is a comparator.

Next, the operation of this embodiment will be explained.

First, a waveform C as shown in FIG. 2(a) is assumed. This waveform C is a triangular wave in which the peak value is large near the phase 0 degree and 180 degree on the horizontal axis, and the peak value is small near the phase 90 degree. It is a composite of triangular waves.

If this waveform C is compared and extracted at a level Vc representing a predetermined degree of modulation, a PWM pulse is obtained as shown in FIG. 2(c). This is due to Haggi's reasons. That is, in the conventional example shown in Fig. 3, the triangular wave: Vc -3in (2
πfinv-t) to obtain a PWM pulse, but in the present invention,
Convert the above equation to triangular wave/Sin (27Cfinv-t): Vc
Therefore, Figure 2 (
The waveform C in a) is the triangular wave/Sin (2
πf inv −t). However, in reality, of the triangular wave train of waveform C, a value higher than the wave height of the one with the minimum wave height value is not required, so a waveform as shown in the same figure (C) is created and this is What is necessary is to compare it with the modulation depth level V.

Therefore, in this embodiment, the trapezoidal wave train represented by this waveform is stored in advance in the ROM 5 as a level value sequentially along the address direction, and is swept in the address order by the count output of the counter 3. The comparator 7 compares the read data with the modulation degree level Vc given from the modulation degree register 6, thereby obtaining a PWM pulse.

By the way, in such a vehicle inverter device,
The variable range of the inverter output frequency is quite wide, for example, from several hertz to several tens of hertz. On the other hand, there is a limit to the switching frequency of the main switching elements used in inverter devices, and for this reason, in the region where the inverter frequency is high, it is not possible to increase the number of switchings during the half cycle.
The upper limit of the number of PWM pulses per unit time shown in FIG. 2(c) has a certain limit depending on the main switching element used. Therefore, the number of pulses within a half cycle (180 degrees) is determined by the inverter frequency. As the value increases and the half-cycle period becomes shorter, it is necessary to leave more time.

Therefore, in this embodiment, a plurality of types of trapezoidal wave trains having different numbers of pulses within a half cycle period (that is, different modes) are stored in advance in the ROM 5, and the trapezoidal wave trains are transmitted from the system control unit 1. set in pulse mode register 4,
The selection is made according to mode data P given from this register 4.

Therefore, when the system control unit 1 outputs the inverter frequency f inv to the frequency generator 2, it operates so as to set one of the predetermined pulse modes Pm corresponding to the frequency. As a result, the optimum number of PWM pulses can always be obtained.

Therefore, according to this embodiment, PWM pulses can be generated using an entirely digital circuit configuration, and the configuration can be simplified. In the above embodiment, the system control section 1 is configured with a microcomputer, and as a result, the frequency generator 2, pulse mode register 4, modulation degree register 6, etc. are simply connected to the system control section 1 as they are. This can further simplify the configuration.

〔Effect of the invention〕

As explained above, according to the present invention, except for the drawbacks of the prior art, there is no need for an analog circuit configuration, and it is possible to easily configure everything with digital circuits.

Also, according to the invention of 1.:, since the firmware of the PWM pulse to be output is stored in the width of the ROM,
The number of pulses can be easily changed, and a PWM pulse generator of a VVVF type inverter device suitable for use in vehicles can be easily provided.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a PWM pulse generator according to the present invention, FIG. 2 is a time chart for explaining its operation, and FIG. 3 is a time chart for explaining the operation of a conventional example. 1...System control unit, 2...Frequency generator, 3...Counter, 4...Pulse mode register, 5...ROM , 6...
...Modulation degree register, 7...Comparator. Itcho--' ・ Agent Patent Attorney Takeshi Kenjibe (1 other person)'', -
11, -' Figure 1 Figure 2 L/-1817 Figure 3

Claims (1)

[Claims] 1. In a PWM pulse generator of a PWM type variable voltage variable frequency inverter device, a trapezoidal wave obtained by slicing a composite waveform of a sine waveform and a triangular wave at a predetermined level is generated along the address direction. A storage means for storing level values; a sweep means for sequentially and periodically accessing the address of this storage means at a designated inverter frequency; A setting means for generating a level value signal is provided, and the PWM pulse is obtained by comparing the signal read out from the storage means with the level value signal given from the setting means. PWM pulse generator. 2. The PWM pulse generator according to claim 1, wherein the sweeping means is a counter that is counted up by pulses equal to the inverter frequency. 3. In claim 1, the trapezoidal wave to be stored in the storage means is a plurality of types of trapezoidal waves having different modes, and the access by the sweeping means A PWM pulse generator characterized in that it is configured to select one of them.