JPH01126169A - Inverter controlling device - Google Patents

Abstract

PURPOSE:To make the rate of content of harmonic component constant and to reduce by comparing an inverted triangle wave with a sine wave and making ignition signals of switching elements of a pair of inverter circuit. CONSTITUTION:An inverter controlling device is constituted of a velocity command means 1, a voltage/frequency command implementation circuit 2 implementing a voltage command and a frequency command from the command means 1, a PWM signal implementation circuit 3, a voltage controlling circuit 4, base amplifier circuits 5a-5b, a gate amplifier circuit 6, a thyristor full-wave rectifier circuit 8 of three phase AC power supply 7, a DC reactor 9, a smoothing electrolytic capacitor 10, inverter circuits 11a-11b by an transistor and a coupling reactor 12. A sine wave is compared with a inverted triangle wave, ignition signals of inverter circuits 11a-11b are implemented, and two or more even numbered inverter circuits 11a-11b are ignited at different points by these ignition signals. In addition, the multiple coupling of the output is made by a coupling reactor 12, and the harmonic wave is offset to suppress it.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a control device for an inverter that generates variable voltage and variable frequency.

[Conventional technology]

FIG. 4 is a block diagram showing a conventional inverter control device. In the figure, 1 is a speed command means, and 22 is a voltage/frequency command creation circuit that creates a voltage command and a frequency command from the command from the speed command means 1. , 23 is a PWM signal (pulse width variation 1
1 signal) PWM signal generation circuit 5a, 5b
is a base amplifier circuit that amplifies the output signal from the PWM signal generation circuit 23, 7 is an AC three-phase power supply, 2B is a diode three-phase full-wave rectifier circuit that rectifies the three-phase AC voltage from the AC three-phase power supply 7, and 9 is a A DC reactor provided in the DC output circuit of the diode three-phase full-wave rectifier circuit 28, 10 is an electrolytic capacitor 11a that smooths the DC voltage together with the DC reactor 9.
, 11b are a pair of inverter circuits that convert direct current to alternating current, and are transistor inverter circuits that use transistors as switching elements. 12 is a coupling reactor of a pair of inverter circuits 11a and 11b, and 13 is an electric motor as a load.

FIG. 5 shows a specific circuit diagram of the PWM signal generation circuit 23, in which 23a is a voltage command 22a and a frequency command 22.
23b is a sine wave generator which inputs the frequency command 22b and generates a variable amplitude sine wave according to the voltage command; 23b is a triangular wave generator which generates a triangular wave by inputting the frequency command 22b; 23C is the sine wave generator 23
This is a comparator that compares the sine wave generated from the triangular wave generator 23b with the triangular wave generated from the triangular wave generator 23b, and generates an output signal when, for example, the sine wave is larger than the triangular wave.

Next, the operation will be explained. A three-phase AC voltage from a three-phase AC power supply 7 is rectified by a diode three-phase full-wave rectifier circuit 28, and this rectified DC voltage is smoothed by a DC reactor 9 and an electrolytic capacitor 10 to form a pair of inverter circuits 1.
Supply voltage is applied to 1a and 11b.

On the other hand, a voltage command 22a and a frequency command 22b corresponding to the speed set by the speed command means 1 are created by the voltage/frequency command creation circuit 22), and the voltage command 22a and frequency command 22b are sent to the PWM signal creation circuit 23. input.

The sine wave generator 23a of this PWM signal generation circuit 23 is
Based on the voltage command 22a and frequency command 22b, the sixth
A sine wave 23d shown in FIGS. 6(a) and 6(b) is generated, and a triangular wave generator 23b generates a triangular wave 23e shown in FIGS. 6(a) and 6(b) based on the frequency command 22b. Then, the comparator 23C outputs the sine wave 23d and the triangular wave 2.
3e and generates an output signal when, for example, the sine wave is larger than the triangular wave.

Next, the output signal of the PWM signal generation circuit 23 is amplified by the base amplifier circuits 5a and 5b, and the amplified output is used to switch the pair of inverter circuits 11a and 11b, thereby converting the DC voltage applied to the inverter circuit into an alternating current. Convert this AC voltage into a voltage and connect this AC voltage to the coupling reactor 1.
2 to the electric motor 13 to drive the electric motor.

[Problem that the invention seeks to solve]

Conventional inverter control devices are configured as described above, so both voltage and frequency must be changed by a pair of inverter circuits, and the content of harmonic components changes depending on the output voltage value, causing harmonics to change. In addition, in order to suppress the harmonics, the carrier frequency (the multiplication frequency of the frequency of the sine wave 23d and the frequency of the triangular wave 23e) must be increased.

This invention was made to solve the above-mentioned problems, and it is possible to keep the content of harmonic components constant even when the output voltage value is changed, reduce the first harmonic acid content, and increase the carrier frequency. An object of the present invention is to obtain an inverter control device that can reduce the power consumption.

[Means for solving problems]

An inverter control device according to the present invention includes an even number of inverter circuits of two or more that are configured with switching elements that convert full-wave rectified output from a full-wave rectifier circuit that is configured with switching elements into AC voltage, and a speed command. A voltage/frequency command creation circuit that creates a voltage command and a frequency command, and a sine wave and a triangular wave are generated separately and independently according to the frequency command, and the sine wave and the triangular wave that are inverted each other are compared and the number of the two or more even numbers is determined. a pulse width modulation signal generation circuit that generates a firing signal for the switching element of the inverter circuit; a pulse amplitude modulation signal generation circuit that generates a firing signal for the switching element of the full-wave rectifier circuit based on the voltage command; The inverter is equipped with a coupling reactor that couples the outputs of an even number of inverter circuits and supplies the combined output to a load.

[For production]

The inverter control device according to the present invention compares a sine wave and a triangular wave that is inverted with each other to create a firing signal for the switching elements of two or more even numbered inverter circuits, and uses this firing signal to switch the switching elements of two or more even numbered inverter circuits. By firing the inverter circuits at different times and multiple-coupling the outputs of the inverter circuits in a coupling reactor, the harmonics are canceled and suppressed. In addition, by controlling the switching elements of the full-wave rectifier circuit with the ignition signal from the pulse amplitude modulation signal generation circuit, the output voltage, frequency, and metal can be controlled independently. Eliminate changing rates.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. 1st
In the figure, 1 is speed command means, 2 is speed command means 10
3 is a voltage/frequency command creation circuit that creates a voltage command and a frequency command as a command; 3 is a PWM signal creation circuit that creates a fiPWM signal from a frequency command from the voltage/frequency command creation circuit 2; 4 is a voltage/frequency command creation circuit 2 A voltage control circuit that creates a thyristor firing signal based on a voltage command from
5"t5b is a pace amplifier circuit that amplifies the output signal of the PWM signal generation circuit 3, 6 is a gate amplifier circuit that amplifies the output signal of the voltage control circuit 4, 7 is a three-phase AC power supply, and 8 is from the three-phase AC power supply 7. a thyristor full-wave rectifier circuit that rectifies the three-phase AC voltage; 9 is a DC reactor; 10 is an electrolytic capacitor that smooths the DC voltage together with the DC reactor 9;
A and llb are a pair of inverter circuits, which are transistor inverter circuits using transistors as switching elements. 12 is a coupling reactor, and 13 is an electric motor.

FIG. 2 shows a specific circuit diagram of the PWM signal generation circuit 3, in which 3a is a sine wave generator that inputs the frequency command 2b and generates a sine wave with a constant amplitude, and 3b is a sine wave generator that inputs the frequency command 2b and generates a triangular wave. 3C is an inverter that inverts the triangular wave from the triangular wave generator 3b, and 3d is an inverter that compares the sine wave generated from the sine wave generator 3a with the triangular wave generated from the triangular wave generator 3b. A comparator 3e generates an output signal when the sine wave is larger than the triangular wave, and a comparator 3e compares the sine wave with the inverted triangular wave output from the inverter 3c, and generates an output signal when the sine wave is larger than the inverted triangular wave, for example. It is a comparator that

Next, the operation will be explained. The voltage/frequency command generation circuit 2 creates a voltage command 2a and a frequency command 2b corresponding to the speed set by the speed command means 1, inputs the voltage command 2a to the voltage control circuit 4, and outputs the frequency command 2b to the PW.
It is input to the M signal generation circuit 3.

The voltage control circuit 4 outputs a firing signal for the switching elements constituting the full-wave rectifier circuit 8 to the gate amplifier circuit 6 according to the voltage command 2a. This gate amplifier circuit 6 amplifies the ignition signal and transmits it to the switching element 8 of the full-wave rectifier circuit 8.
A is ignited, the three-phase AC voltage from the three-phase AC power supply 7 is rectified, the DC voltage is smoothed by the DC reactor 9 and the electrolytic capacitor 10, and is supplied to the pair of inverter circuits 11a and 11b.

Further, the sine wave generator 3a of the PWM signal generating circuit 3 operates as shown in FIG. 3(a) based on the frequency command 2b.

A sine wave 3f shown in FIG. 3(b) is generated, and a triangular wave generator 3b generates a triangular wave 3g shown in FIG. 3(a) based on the frequency command 2b. In addition, the inverter 3C has the above-mentioned triangular wave 3g.
is inverted to output an inverted triangular wave 3g shown in FIG. 3(b). Then, the comparator 3d outputs the sine wave 3f and the triangular wave 3.
The comparator 3e compares the sine wave 3f and the inverted triangular wave 3g and generates an output signal when the sine wave is larger than the triangular wave, for example, when the sine wave is larger than the triangular wave. Each output signal is input to pace amplifier circuits 5a and 5b.

Pace amplifier circuits 5a and 5b are PWM signal generation circuits 3
The output signals from the comparison circuits 3d and 3e are amplified, and the switching elements of the pair of inverter circuits 11a and 11b are turned on to convert the DC voltage applied to the inverter circuits into an AC voltage. is supplied to the electric motor 13 via the coupling reactor 12 to drive the electric motor.

In the above embodiment, a thyristor full-wave rectifier circuit 8 is provided, but a switching element such as a transistor, a GTO thyristor, or an FET may be used instead of the thyristor. Although the three-phase AC power supply 7 is shown, it may be a single phase or a polyphase of three or more phases.

Although the pair of inverter circuits 11a and 11b are shown as having transistors as switching elements, GTO thyristors are used instead of transistors.

A switching element such as an FET may also be used. Further, although the illustrated example shows a pair of inverter circuits, the number is not particularly limited as long as it is an even number of two or more.

〔Effect of the invention〕

As described above, according to the present invention, a sine wave and a mutually inverted triangular wave are compared to create a firing signal for the switching elements of a pair of inverter circuits, and the firing signal is used to operate the pair of inverter circuits. Since the output of the inverter circuit is configured to be multiple-coupled, the content of harmonic components is kept constant and reduced, the carrier frequency is lowered, and the number of firings of the switching element is reduced, thereby reducing damage to the switching element. can.

Further, the output voltage and frequency can be controlled separately and there is an effect that the content rate of high frequency components does not change due to output voltage control.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an inverter control device according to an embodiment of the present invention, and FIG. 2 is a block diagram showing the components of the device.
A block diagram showing the configuration of the WM signal generation circuit, FIG. 3 is a signal waveform diagram explaining the operation of the PWM signal generation circuit, FIG. 4 is a block diagram of a conventional inverter control device, and FIG. 5 is the configuration of the device. FIG. 6 is a block diagram of a PWM signal generation circuit which is an element, and a signal waveform diagram illustrating the operation of the PWM signal generation circuit. 1 is a speed command means, 2 is a voltage/frequency command generation circuit, 3
1 is a PWM signal generation circuit, 4 is a voltage control circuit, 7 is a three-phase AC power supply, 8 is a full-wave rectifier circuit, 11a and 11b are single-lead inverter circuits, 12 is a coupling reactor, and 13 is a load. In addition, in the figures, the same reference numerals indicate the same or equivalent parts. Patent applicant: Mitsubishi Electric Corporation 1-1 (2 others) 1st

Claims (1)

[Claims] a full-wave rectifier circuit composed of switching elements; an even number of two or more inverter circuits composed of switching elements that convert the full-wave rectified output from the full-wave rectifier circuit into alternating current voltage; and a speed command means. A voltage and frequency command creation circuit that creates a voltage command and a frequency command according to the command, and a sine wave and a triangular wave that are generated separately and independently according to the frequency command, and compare the sine wave and the triangular wave that are inverted with each other to generate the two or more. a pulse width modulation signal generation circuit that generates a firing signal for the switching elements of the even-numbered inverter circuit; a pulse amplitude modulation signal generation circuit that generates a firing signal for the switching element of the full-wave rectifier circuit based on the voltage command; An inverter control device equipped with a coupling reactor that couples the outputs of two or more even number of inverter circuits and supplies the combined output to a load.