JPS62147966A - Voltage control circuit of inverter - Google Patents

Abstract

PURPOSE:To suppress the transient voltage fluctuation to the minimum by providing a proportional-plus-integral control means to the loop to which a proportional control means is already provided so as to compare the voltage outputted by the inverter unit as it is in the sinusoidal wave with the reference sinusoidal wave and to control it. CONSTITUTION:The AC voltage outputted by an inverter unit composed of a transistor inverter 3 and a filter 4 is detected by a voltage transformer 11, rectified and smoothed by a rectifier 12 and a smoothing circuit 13 and the deviation from the voltage set out by a voltage setting device 14 is outputted to a proportional integral adjuster 15. A reference sinusoidal wave generation circuit 21 outputs a sinusoidal wave voltage of the same frequency as in the output of the inverter unit with the amplitude proportional to the output of the proportional integral adjustor 15. This output is compared with the sinusoidal wave voltage from the inverter unit and is outputted to a proportional adjuster 22. A transistor 3 is controlled by the output of said proportional adjuster 22 through a pulse duration modulation circuit 18 and a control circuit 19.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention relates to a circuit that controls a voltage output by an inverter that converts direct current to alternating current.

[Prior art and its problems]

In an inverter that outputs constant voltage, constant frequency AC power, such as a so-called CVCF inverter, the inverter's output voltage is fed back and the output voltage of the inverter is controlled so that the deviation from the predetermined voltage is zero. ing.

FIG. 2 is a block diagram showing a conventional example of an inverter that outputs constant voltage AC power. In this figure 2, DC′! ! The DC power from the source 2 is input to the transistor inverter 3, which is composed of switching transistors and feedback diodes, and by sequentially turning on and off each switching transistor, the input DC power is converted to AC power. It is converted into electric power and output, but since this output contains harmonic components, a filter 4 consisting of a reactor and a capacitor is used.
This harmonic component is absorbed and removed, and the load 5 is supplied with sinusoidal AC power.

The output voltage of the inverter device composed of a transistor inverter 3 and a filter 4 is isolated and detected by a voltage transformer 11, and is detected by a rectifier 12 and a smoothing circuit 1.
3, a direct current voltage actual value signal proportional to the alternating current voltage output by the inverter device is obtained. On the one hand, since the voltage setter 14 sets the voltage target value signals that this inverter device should output, the deviation between these voltage target value signals and the voltage actual value signal is determined by the proportional-integral regulator 15.
is input, and the proportional-integral regulator 15 outputs a control signal that makes the input deviation zero.

Since the sine wave generation circuit 16 outputs a sine wave signal with an amplitude corresponding to the output of the proportional-integral regulator 15, the carrier wave output from the carrier wave generation circuit 17 and the aforementioned sine wave signal are input to the pulse width modulation circuit 18. to pulse width modulate the sine wave. The output from this pulse width modulation circuit 18 is controlled by a control circuit 19.
The control circuit 19 sends a signal to the pace of each transistor constituting the inverter 3, and by controlling these transistors on and off appropriately, the output voltage of the inverter is set by the voltage setting device. 14 is controlled to maintain the voltage target value set.

By the way, the conventional circuit shown in FIG. 2 is the smoothing circuit 1.
3 and the proportional-integral regulator 15, which have large time constants, the response time becomes long. Therefore, it is not possible to quickly follow voltage fluctuations caused by sudden changes in the load 5, for example, and has the disadvantage of causing large output voltage fluctuations.

Therefore, the circuits described in JP-A-59-153467 and JP-A-59-153468 separately generate a reference sine wave, and combine this with the sine wave voltage output by the inverter. A control circuit has been put into practical use that instantaneously compares and amplifies the deviation so that the output voltage of the inverter device matches the reference sine wave.

The circuits described in each of the above-mentioned publications compare the sine wave that is the voltage target value and the sine wave that is the actual voltage value at every instant, and calculate the deviation between the two using a regulator with no operating time delay, such as a proportional regulator. Since the inverter is controlled by pulse width modulation using this proportional regulator output signal and the carrier wave, it quickly responds to the output voltage fluctuations of the inverter device, and has the effect of suppressing transient voltage fluctuations to a small level. Demonstrate.

However, while the coordination can be improved by using a proportional regulator, a steady deviation occurs between the voltage target value and the actual voltage value in control, which causes a voltage error. Therefore, if the gain of the proportional regulator is increased to counteract this deviation, the operation becomes unstable.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an inverter voltage control circuit that quickly responds to changes in the output voltage of an inverter device, suppresses transient voltage fluctuations to a minimum, and does not cause steady voltage deviations. .

[Key points of the invention]

The present invention provides a loop of proportional-integral adjustment means for comparing and controlling an actual voltage value obtained by smoothing a sinusoidal voltage output from an inverter and a voltage target value obtained by a voltage setting device, and A loop of proportional adjustment means is provided to compare and control the output sinusoidal voltage with a reference sine wave obtained from the reference sine wave generation means, and the amplitude of the reference sine wave is adjusted in accordance with the output of the proportional integral adjustment means. A circuit is configured to give a signal to the reference sine wave generating means so as to change the signal, pulse width modulation is performed on the output signal of the proportional adjustment means with a carrier wave, and the inverter is controlled by the pulse train obtained in this way. The purpose is to quickly respond to fluctuations in the device output voltage to suppress transient voltage fluctuations, and also to eliminate steady noise pressure deviations.

[Implementation sequence of the invention]

FIG. 1 is a block diagram showing an embodiment of the present invention, and the content of the present invention will be explained in detail below based on this FIG.

In FIG. 1, a transistor inverter 3 is formed by bridge-connecting an arm configured by connecting a feedback diode in antiparallel to a transistor used as a switching element, and direct current power from a direct current power source 2 is transferred to this transistor inverter. AC power is output from the transistor inverter 3 when the transistors as switching elements are sequentially turned on and off. Which transistor inverter 3
Since the AC power output from the AC power includes harmonic components, the filter 4, which is composed of a reactor and a capacitor, absorbs and removes these harmonic components to form a sine wave, and then supplies the power to the load 5. .

The AC voltage output by the inverter device composed of the transistor inverter 3 and filter 4 is set to a constant value K i! as follows. IJ #is done. That is, the AC voltage detected by the instrument transformer 11 is rectified by the rectifier 12, and further smoothed by the smoothing circuit 13 to become an actual voltage value signal. Therefore, there is a delay in operation time. In addition, since the voltage setter 14 sets a predetermined voltage target value signal, when the deviation between this voltage target value signal and the above-mentioned voltage actual value signal is inputted to the proportional-integral regulator 15GC, the proportional-integral regulator 15 outputs a , a control signal corresponding to the input voltage deviation is output. By the way, this proportional integral regulator 1
5 also has a delay in operation time.

On the other hand, the reference sine wave generation circuit 21 receives the frequency of the inverter output voltage detected by the instrument transformer 11 and outputs a reference sine wave signal of the same frequency. The amplitude changes in accordance with the output from the proportional-integral regulator 15 mentioned above. Therefore, the reference sine wave signal thus obtained is compared with the sine wave voltage from the inverter device detected by the instrument transformer 11, and the deviation between the two is inputted to the proportional controller 22. This proportional regulator 22 outputs a sinusoidal signal corresponding to the input deviation without any time delay.

The pulse width modulation circuit 18 inputs the carrier wave output from the carrier wave generation circuit 17 and the sinusoidal signal output from the above-described proportional adjuster 22, and outputs a pulse train having a sinusoidally modulated pulse width. The control circuit 19 uses the signal from the pulse width modulation circuit 18 to generate a pace signal that turns each transistor on and off at appropriate timing, so that the AC voltage output from the transistor inverter 3 is controlled by the voltage setting device 14. It is controlled to match the voltage target value signal set in .

By configuring the circuit as described above, for example, the load 5
Even if the AC voltage detected by the instrument transformer 11 decreases due to a sudden increase in the voltage, the amplitude of the reference sine wave output from the reference sine wave generation circuit 21 has not changed at that point, so proportional adjustment is performed. The input deviation of the device 22 increases. Since the proportional regulator 22 immediately responds to this change in input deviation, the pulse width modulation circuit 18 increases the modulation rate λ to quickly increase the voltage output from the transistor inverter 3, minimizing transient voltage fluctuations. can do. On the other hand, the AC voltage detected by the instrument transformer 11 is converted into a smooth DC voltage signal by the rectifier 12 and the smoothing circuit 13 and compared with the setting value of the voltage setting device 14, so that the proportional Since the integral regulator 15 changes the width of the reference sine wave signal so as to make the input voltage deviation, that is, the deviation between the actual voltage value and the positive target value, zero, the difference due to steady voltage fluctuations is zero. becomes.

〔Effect of the invention〕

According to this invention, the i/parta ke! In a loop equipped with a proportional adjustment means that compares and controls the voltage output by the inverter with a reference sine wave while keeping it in the form of a sine wave, the voltage actual value, which is the average value of the voltage output by the inverter device, and the separately set voltage target value are connected to the loop. By adding a loop equipped with a proportional-integral adjustment means for comparing and controlling the ratio, the amplitude of the reference sine wave is changed in response to the output of the proportional-integral adjustment means. With such a circuit configuration, the loop equipped with the proportional adjustment means immediately responds to negative or variable output voltage of the inverter and operates so as to minimize transient fluctuations in the output voltage of the inverter. Since the loop equipped with the proportional-integral adjustment means including the response time delay element reduces the steady-state deviation to zero, the inverter device has the effect of suppressing transient voltage fluctuations in response to disturbances and also reducing the steady-state deviation to zero. Demonstrate.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG.
The figure is a block diagram showing a conventional example of an inverter that outputs constant voltage AC power. 2...DC power supply, 3...Transistor inverter,
4... Filter, 5... Load, 11... Instrument transformer, 12... Rectifier, 13... Smoothing circuit, 14...
...Voltage setting device, 15...Proportional-integral regulator, 16...
・Sine wave generation circuit, 17...Electronic wave generation circuit, 18.
...Pulse width modulation circuit, 19...Control circuit, 21...
-Reference sine wave generation circuit, 22...proportional adjuster.
, -1,・″・ . ；→Koshiko 2 people t+ J= x Xb L-7
;')",・Pa 1,・-',!(7,,＞'Teacher's circuit Figure 1

Claims (1)

[Claims] 1) In an inverter device configured with an inverter that converts direct current to alternating current by pulse width modulation control, and a filter that absorbs harmonic components contained in the output of this inverter and converts it into a sine wave, from the inverter device means for smoothing the output AC voltage to obtain a voltage actual value signal;
a voltage setting device for setting a voltage target value signal; a proportional-integral adjusting means for inputting a deviation between the voltage target value signal and the voltage actual value signal; a reference sine wave generation means for outputting a reference sine wave signal with an amplitude corresponding to the output of the proportional integral adjustment means; and a proportional adjustment means for inputting the deviation between the AC voltage signal detected from the inverter device and the reference sine wave signal. and pulse width modulation means for outputting and controlling a pulse width modulated signal to the inverter from the proportional adjustment means output signal and a separately output carrier wave. control circuit.