JPS60200770A - Sinusoidal wave inverter - Google Patents

Abstract

PURPOSE:To obtain a waveform near a sinusoidal wave by a less controller by complementarily controlling ON or OFF one arm of a main switch during positive or negative period of a reference sinusoidal wave, and complementarily controlling ON or OFF the other arm by the comparison of the voltage with the reference sinusoidal wave. CONSTITUTION:Main switches Tu, Ty contained in one series arm is complementarily controlled ON or OFF during positive or negative period of a reference sinusoidal wave generated from a reference sinusoidal wave generator 6 by an inverter main circuit 1 in which the main switches Tu-Ty are connected in a bridge. The main switches Tu, Tx contained in one series arms are complementarily controlled ON or OFF in response to the compared output by comparing the detected voltage of output voltage detecting means (4, 5) provided at the intermediate of the main switch circuit 1 and an AC filter 2 with the voltage value of the reference sinusoidal wave by a comparator 8. Thus, an AC filter can be reduced in size.

Description

[Detailed description of the invention] (Technical field) The present invention relates to a sine wave inverter.

(Prior art and problems) A sine wave inverter that obtains sine wave AC power from a DC power source is composed of an inverter body for general KDO-AC conversion and an AC filter for converting the square wave voltage into a sine wave. . Furthermore, in order to downsize the AC filter, the main body of the inverter is multiplexed or a PWM (pulse width modulation) inverter is used. For this reason, the control system becomes complicated, the main circuit configuration becomes complicated, and reliability often deteriorates.

(Object of the Invention) The object of the present invention is to shorten the control device by 1 m and create an AC filter? A sine wave inverter that can be made smaller? It is on offer.

(Summary of the Invention) The present invention detects an inverter output voltage signal as a sine wave approximation waveform by fully filtering it, and compares this sine wave with a basic sine wave converter to detect one pair of arms of the inverter main switch. On/off ui! I f11411.
, the on-period of the other pair of arms paired with this arm is controlled between the positive and negative waves of the reference sine wave.

('il!1mi example) Figure 41 shows an embodiment of the present invention, and shows a case where it is applied to a single-phase inverter. The transistors TU, TV, TX, and TY are bridge-connected as the inverter main circuit JU main switch, and the output is passed through the A and C filters 2 consisting of the reactor L and the capacitor C5 to supply all the sine wave power to the load 3. An RC filter 4 having a resistor R and a capacitor c2 connected in series is provided between the output terminals of the inverter main circuit 1. This RC filter 4 approximates the inverter output voltage shaping gold sine, and the R02 time constant isolation transformer 5 as a detection element is the voltage (sine wave) of the capacitor c2 of the filter 4? To detect. The sine wave generation circuit 6 is the inverter operating frequency ω. and voltage V. Generates a standard sine wave. The square wave converter 7 is constituted by a zero cross comparator, for example, and obtains a turn-off signal corresponding to the positive period and negative period of the reference sine wave signal of the sine wave generating circuit 6. The comparator 8 compares the signal of the reference sine wave 1 of the sine wave generating circuit 6 with the detection signal from the isolation transformer 5 and the t level.

The gate circuit 9U r 9V * 9X + 97 includes each transistor TU, Ty, TX, Ty F-
On-off city 11 (a, the control signal is the output vs of the square wave converter 7 is input to the gate circuit +1y, and the inverse output ``S'' of the output VB is input to the gate through 10 iB physical inverters. The output VC of the comparator 8 is used as the human power of the gate circuit 9U, and the inverted signal VC of the output VC is passed through the logic inverter 11 to the gate circuit 9Y.
It is assumed that the amount of human power is x.

In this configuration, the transistor TV that becomes the V-phase arm and the transistor TY that becomes the Y-phase arm are lii! ,
The current is connected in series between the high pressure side P and the low pressure side N, and as shown in FIG.
The transistor TV is turned on during the negative period, and the transistor TY is turned on during the negative period. -10,000, U J'fl The transistor TU which becomes the arm and the transistor TX which becomes the X-phase arm are switched on and off in a complementary manner according to the output VCK of the comparator 8.

The on/off switching of these transistors TX and TU is performed using a reference sine wave BINω. This is the comparison result between t and the feedback signal VCR from the inverter output.

Now, the period during which the transistor TV is on is T pV [
Sine e 1g @ S engineering No>. t, J: When the detection signal VCR is at a low V pel in 9, the output of the comparator 8 is set to the polarity to turn on all transistors Tx and turn off TU'i, and when the transistor TX is turned on, the inverter output voltage rises, and this rise On the other hand, the detection signal VCR also rises with the slope of its time constant CR. And this detection signal VC
R is a sine wave signal SINω. When the voltage becomes higher than t, the output of the comparator 8 is inverted, turning off the transistor TX and controlling the voltage on the TU, and the output voltage of the inverter decreases when the transistor TX is turned off. With this fall, when the detection signal VCR becomes the sine wave signal SINω0↑, below Kl, the transistor TX is turned on again by the controller.

As a result of such repetitive control, the inverter output is gated tltll# so as to follow the level change of the IE sinusoidal signal SINωot, and the period TN during which the transistor TY is in the on state is also subjected to similar follow-up control. During this period TN, when the detection signal VCR becomes equal to or lower than the sine wave signal srNωot, the transistor TU is controlled to be turned on, and BINωotk
When the voltage is exceeded, the transistor TX is turned off.

Therefore, the output of the inverter is the reference sine wave signal SINω
The frequency becomes Ot, and the sine wave output becomes equal dynamic conduction with the reference sine wave regardless of fluctuations in direct current pressure. The harmonic component included in this inverter output is determined approximately by the time constant of the RC filter 4 and the resolution of the comparator 8, but it is determined by the response of the main switch transistor and the AC
It is set in consideration of the cutoff frequency of filter 2.
Ru.

Although the embodiment shows a single-phase inverter, it is of course applicable to a three-phase inverter.

(Effects of the Invention) As described above, according to the present invention, AC
filter? It is detected by a filter with a constant time constant as a voltage signal before the west side, and by comparing the level of this detection signal with a reference sine wave signal, one pair of direct control arms 11 is complementarily controlled on/off, and the other one is Paired series arms? Complementarily turn on and off tli1. during the positive and negative periods of the reference sine wave signal. to control
A little bit of control circuit gold 1 and a waveform close to a sine wave for the inverter output? The AC filter in the subsequent stage can be made completely small and the entire power of the sine wave waveform can be supplied to the load. Accordingly, the present invention has the effect of making it possible to downsize the AC filter while eliminating the need for the conventional multiplex configuration and complicated control of PWM control. Furthermore, it is not necessary to provide control or correction means for nuclear disturbances such as pressure fluctuations in the inverter DC 1.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing one embodiment of the present invention; Fig. 2; I'
j FIG. 1 is a waveform diagram of each part in FIG. 1. 1... Inverter main circuit, 2... AC filter, 3
...Load, 4...RC filter, 5...Isolation transformer, 6...Reference sine wave generation circuit, 7...Square wave converter, 8...Comparator, 9y, 9y, 9U
, 9X...gate circuit.

Claims (1)

[Claims] An inverter main circuit in which the main switch is configured as a bridge, and A that removes harmonic components from the output of this inverter main circuit.
C filter, a voltage detection means for detecting the output voltage of the inverter main circuit with a fixed time constant, a sine wave generating circuit that generates a reference voltage at the inverter operating frequency and voltage, and a sine wave generating circuit for generating the reference sine wave. a first gate means for complementary on/off control of one pair of series arms of the main switch according to the positive and negative periods; and a comparator for comparing the levels of the reference sine wave and the detection signal of the voltage detection means. and second gate means for complementary on/off control of the other pair of series arms of the main switch in accordance with the output of the comparator.