JPH03124271A - Inverter device restraining harmonics - Google Patents

Abstract

PURPOSE:To restrain harmonics components of current effectively by a method wherein a power rectifying unit is constituted of a self arcextinguishing element while the switching element of the power rectifying unit is controlled through PWM control. CONSTITUTION:A power rectifying unit 6 converts an AC power from an AC power source 1 into a DC power. The DC power of the power rectifying unit 6 is converted into the AC power of a predetermined frequency by a power inverting unit 10 and, thereafter, is supplied to an induction motor 19a. A control circuit unit 17 inputs a synchronous signal S1, a load current detecting signal S2, an inverter current detecting signal S3, a DC voltage detecting signal S4 and a DC current detecting signal S5 and outputs PWM signals based on these signals to control the transistor 7 of the power rectifying unit 6. According to this method, harmonics can be restrained effectively.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to an inverter device, and more particularly to a harmonic suppressing inverter device having a harmonic suppressing function.

B2 Summary of the Invention The present invention provides an inverter device including a forward conversion section and an inverse conversion section, in which the forward conversion section is constituted by a self-extinguishing switching element, and the switching element of the forward conversion section is configured using PWM.
By providing a control circuit section for controlling, a harmonic suppression inverter device capable of effectively suppressing harmonic components of current is obtained.

C1 Prior Art In recent years, with the advent of semiconductor power conversion devices, harmonic problems in power systems are becoming more apparent. To deal with this problem, various devices with harmonic suppression functions have been proposed.

A device having a rectifier circuit, such as an inverter, is a typical example of a harmonic generation source. Therefore, in order to suppress the harmonics from flowing into the reverse arrangement system, customers who install these electric power devices had to newly install a harmonic suppression device.

For the inverter itself, there is a method of converting the input terminal into a sine wave by using a self-extinguishing element in the input circuit of the inverter and performing PWM control to convert the grid power supply into a sine wave, but in the case of a large number of equipment. became expensive.

The present invention has been made in view of the above-mentioned problems, and its purpose is to configure the forward conversion section with a self-extinguishing switching element, detect the current in the system including harmonics, and command a compensation current. It is an object of the present invention to provide an inexpensive and high-performance harmonic suppression inverter device by calculating the value and controlling the forward conversion section based on the compensation current command and the current command value necessary for driving the motor.

E1 Means for Solving the Problems In order to achieve the above object, the present invention includes a forward converter that converts AC power into DC power, and a reverse converter that converts the DC power into AC power of a predetermined frequency by the forward converter. It consists of a conversion section and a control circuit section that controls the surface order conversion section, and the order conversion section is constituted by a self-extinguishing switching element,
The control circuit section is subjected to arithmetic processing based on the input voltage detection signal of the Moeki forward conversion section, the load current detection signal of the power supply, the input current detection signal of the forward conversion section, and the DC output voltage detection signal of the forward conversion section. It is constituted by arithmetic means that controls the switching elements of the forward conversion section.

21 PWM using a self-extinguishing switching element in the action order conversion section
Take control. The current flowing into this forward conversion section is used to compensate for harmonic currents generated from other devices connected to the same system. The total current supplied from the oscillator is controlled to be a sine wave.

G. Embodiment Embodiments of the present invention will be described below with reference to FIGS. 1 to 3.

Is Figure 1 an embodiment of the present invention? This harmonic suppression inverter device is shown in which I is an AC power source, 2 is a reactor, and 3 is a capacitor. These reactor 2 and capacitor 3 form a carrier wave removal filter 4. 5 is an AC reactor, and 6 is a forward converter, which is connected to the AC power source I via the carrier removal filter 4 and the AC reactor 5. The forward conversion unit 6 is formed by bridge-connecting a transistor 7, which is a self-extinguishing switching element, and a diode 8 is connected in antiparallel to the transistor 7. 9 is a capacitor,
Reference numeral 10 denotes an inverse conversion section, which is constructed by bridge-connecting transistors 11 to which diodes 12 are connected in antiparallel.

A transformer 13 is a voltage detector, and a current transformer 14 is a current detector, which detects the load current I +.

15 is a current transformer which is a current detector and detects the inverter current. 16 is a current detector that detects direct current. Reference numeral 17 denotes a control circuit unit for controlling the forward conversion unit 6, which receives a synchronizing signal Sl from the lance 13 and a load current detection signal S2 of the current transformer I4.
．． Inverter current detection signal S3 of current transformer 15. The gate signal S6 is output with the DC voltage detection signal S4 and the DC current detection signal S5 as input signals. Thus, the forward conversion unit 6.
An active inverter I8 is constituted by the inverse conversion section (1)0 and the control circuit section I7. Induction motors 19a to +9c are loads, and inverters 20a and 20b.

In the harmonic suppression inverter device shown in FIG. 1, the forward converter 6 converts AC power from the AC power source (2) into DC power.

The DC power of the forward converter 6 is converted into AC power of a predetermined frequency by the inverse converter 10, and then supplied to the induction motor 19a. The control circuit section 17 receives the synchronization signal S1. Load current detection signal S2. Inverter current detection signal S3. It receives the DC voltage detection signal S4 and the DC current detection signal S5 as input, outputs a PWM signal based on these signals, and controls the transistor 7 of the forward conversion section 6. That is, the main circuit section consisting of the forward converter 6 and the inverse converter IO is the same as a conventional voltage source regeneration inverter, and the AC reactor 5 is connected to the input side, and the forward converter 6 is connected to the AC reactor 5. A self-extinguishing switching element is used. In order to provide the conventional inverter with the function of suppressing the harmonic current of the system, the control circuit section I7 controls the load current r1. A new function has been added to detect the harmonic compensation current command value for the target load current It. Therefore, even when the induction motor 19a is not operating, the system load current can be reduced by controlling the switching element of the forward converter 6.
1, which compensates for the harmonics of 1.

According to the harmonic suppression inverter device shown in FIG. 1, the following various advantages can be obtained.

(1) Not only does it function as a variable speed device, but it also has the function of compensating for harmonic currents in the same power system, so a separate active filter is not required.

(2) Even when installing multiple general-purpose inverters,
By installing a small number of inverters with a harmonic suppression function according to the harmonic compensation capacity, harmonic suppression can be performed more economically.

(3) Self-extinguishing switching elements are used in the main circuit elements of the converter section of this inverter device, making it easy to regenerate power.

(4) The main circuit configuration is almost the same as that of a conventional inverter, and it also serves as a harmonic suppressor without increasing costs, making it highly economical and significantly improving cost performance.

FIG. 2 shows another embodiment of the present invention. In this embodiment, the control circuit section is composed of a compensation current command value calculation circuit 21 and a PWM calculation circuit 22, and the other load is a rectifier load. 23a23b is used.

According to the harmonic suppression inverter device shown in FIG. 2, the gate signal of the forward conversion unit 6 is the synchronization signal S
Compensation current command value calculation circuit 2I based on l and load current It
A compensation current command value is calculated by the PWM calculation circuit 22 based on the compensation current command value, the inverter current detection signal S3, and the DC voltage detection signal S4, and this PWM signal is sent to the forward conversion unit 6 as a gate signal. Supply as.

FIG. 3 shows the current waveforms of various parts of the harmonic suppression inverter device of FIG. 2, where a curve 121 is the waveform of the power supply current Ig, and a curve ρ is the waveform of the load current Is.

is the waveform of the fundamental wave component current IF of the load current ■, curve a4 is the waveform of the harmonic component current (IF IL) of the load current 1+, and curve ρ5 is the waveform of the inverter input terminal ■. waveform, curve ρ
6 is the waveform of the current necessary to drive the motor.

As is clear from FIG. 3, the inverter input current I. flows as a harmonic compensation current of the current required to drive the motor and the load current ■. So invar driving motor
- It is possible to make the grid current I5 into a sine wave even in the evening, and it also has the same effect as the one in FIG.

H. Effects of the Invention The present invention is as described above, and consists of a forward converter having a self-extinguishing switching element and an inverse converter that converts the DC output power of the forward converter into AC power of a predetermined frequency. ,
Since the system current including harmonics is detected and a compensating current command value is calculated, and the switching element is PWM controlled using this compensating current command value and the current command necessary for driving the load, effective harmonics can be A suppression inverter is obtained 1 2 .

[Brief explanation of drawings]

FIG. 1 is a block diagram of a harmonic suppressing inverter device according to an embodiment of the present invention, FIG. 2 is a block diagram of a harmonic suppressing inverter device according to another embodiment of the present invention, and FIG. 3 is a block diagram of a harmonic suppressing inverter device according to another embodiment of the present invention. It is a current waveform diagram of each part.

Claims (1)

[Claims] (1) Consisting of a forward conversion section that converts AC power into DC power, an inverse conversion section that converts the DC power by this forward conversion section into AC power of a predetermined frequency, and a control circuit section that controls the forward conversion section, The forward conversion section is configured with a self-extinguishing switching element, and the control circuit section is configured to receive an input voltage detection signal of the forward conversion section, a load current detection signal of the power supply, an input current detection signal of the forward conversion section, and the forward conversion section. 1. A harmonic suppression inverter device, characterized in that it is constituted by an arithmetic means that performs arithmetic processing based on a DC output voltage detection signal of a converter to control switching elements of the forward converter.