JPS6154877A - Controlling method of inverter - Google Patents

Abstract

PURPOSE:To improve the reliability by storing in advance a pulse train firing signal corresponding to a control input in a ROM, and reading out it to control a switching element, thereby simplifying a controller. CONSTITUTION:A PWM type inverter has a DC power 1, an inverter 2, a load 3 such as a 3-phase induction motor, and a controller 4, and the controller 4 supplies pulse trains Cu-Cw as firing signals to the switching element of the phase corresponding to the inverter 2 to control the inverter 2. In this case, a ROM (Read only memory) 8 is provided in the controller 4, the pulse trains Cu-Cw are converted into data and stored therein. This is read as data corresponding to the input value of the control input D to generate the pulse train firing signal of the inverters 2.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to an inverter control method.

[Prior art]

FIG. 1 is a basic block diagram of a conventional PWM type inverter device. In the figure, 1 is a DC power supply, 2 is an inverter, 3 is an inverter load such as a three-phase induction motor,
Reference numeral 4 denotes a control device, which includes a modulated wave generation circuit 5, a one-prong transmission wave generation circuit 6, and a comparison circuit 7. As shown in FIG. 2, the comparison circuit 7 compares the modulated wave A and the carrier wave B, and determines that the former is output during a longer period than the latter, and the pulse train Cu shown with diagonal lines is
is supplied to the switching element of the corresponding phase of the inverter 2 as an ignition signal. The pulse train CV is the above pulse train Cu.
A pulse train of another phase with a phase shift of 120 degrees from the waveform Euv
represents the line voltage output by the inverter, and this waveform Eu
The waveform obtained by Fourier expansion of v is indicated by F. The peak value of this modulated wave A is controlled in response to the control input. For example, when the peak value becomes small, the output voltage gu of the inverter supplied to the inverter load 3 increases as shown in FIG.
v decreases.

The control operation of the inverter is performed in this way, but the conventional control shown in Figure 1 requires a modulation wave generation circuit, a carrier wave generation circuit, a comparator circuit, etc. Especially when the inverter becomes a multi-phase inverter, This method has the disadvantage that only one modulated wave generation circuit is required, which increases the cost of the control device.

[Summary of the invention]

This invention was made to eliminate the above-mentioned conventional drawbacks, and includes a ROM in which the above-described modulated wave pulse train is converted into data and stored in advance, and data corresponding to this is read out by a control input to drive a switching element. This paper proposes an inverter control method that simplifies the control device and significantly reduces manufacturing costs compared to conventional methods, and also improves reliability. .

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

In Figure 4, 8 is a read-on memory (ROM
), the pulse train Cu .

Pulse train Cu stored as data in ROM8
-, CV, and Cw are a plurality of pulse trains including a pulse train that gives the highest output of the inverter and a pulse train that gives the lowest output (one of them is shown in FIG. 5).
, are associated in advance with the input values of the control inputs.

In this way, the present embodiment replaces the modulated wave generation circuit, carrier wave generation circuit, and comparison circuit in the conventional control device with an RO
Since the M8 is used to generate a pulse train firing signal without performing a comparison operation between a modulated wave and a carrier wave, the control device is simplified.

Although the above embodiments have been described with respect to sine wave PWM, the present invention can be applied to equally spaced PWM to obtain similar effects.

〔Effect of the invention〕

As explained above, this invention does not create a pulse train firing signal while performing a modulation operation in response to the control input, but instead stores the pulse train firing signal in the ROM in advance and generates the pulse train firing signal in response to the control input. Since the inverter is read out, the control device is simpler than the conventional one, and reliability is improved accordingly, and the cost of the device can be reduced, and this effect becomes more pronounced as the number of inverter output phases increases.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a conventional inverter device, Figs. 2 and 3 are waveform diagrams for explaining the operation of the above conventional example, Fig. 4 is a block diagram showing an embodiment of the present invention, and Fig. 5 FIG. 2 is a waveform diagram for explaining the operation of the above embodiment. In the figure, 4--control device, 8-ROM. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] When performing PWM control on an inverter, a pulse train firing signal given to a switching element in response to a control input is stored in a ROM as data in advance, and the corresponding data is read out by the control input to turn on the switching element. - An inverter control method characterized by controlling off.