JPS6253179A - Constant-voltage and constant-frequency power unit - Google Patents

Abstract

PURPOSE:To compensate the strain of output voltage by a simple constitution by generating a PWM signal in response to the quantity of a deviation between output voltage and reference voltage and a higher harmonic component in output voltage. CONSTITUTION:An output from a DC voltage source 1 is fed to a load 4 through a semiconductor switching device 2 and an AC filter 3. Output voltage is detected through a transformer 5, rectified by a rectifying circuit 6, applied to a comparator 8 and compared with output voltage from a reference DC voltage source 7. An output from the comparator 8 is transmitted over a multiplier 10 through an amplifier 9 for controlling voltage, multiplied by a reference sine wave signal from a sine wave generating circuit 11, added to a phase- inverted signal in a higher harmonic component in output voltage by an adder 22, and given to a PWM signal generating circuit 13. Switching elements S1-S4 for the semiconductor switching device 2 are ON-OFF controlled by an output from the PWM generating circuit 13.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a constant voltage, constant frequency power supply device (so-called CVC) that obtains an AC output of a constant voltage and frequency from a DC voltage source.
F), and particularly relates to means for compensating for distortion caused by harmonic currents when a nonlinear load is connected.

(Prior Art) A conventional constant voltage, constant frequency power supply device converts DC voltage into AC voltage by controlling on and off using a semiconductor switching device, and uses an AC filter to remove unnecessary frequency components associated with switching from the converted output. On the other hand, the conversion output (output side voltage of the AC filter) is detected and converted to DC, the deviation signal obtained by comparing it with a reference voltage is amplified by a voltage control amplifier, and the output is multiplied by a reference sine wave signal, and this multiplication is performed by comparing the level of the combined output and the carrier wave to form a 5 PWM signal, and this PWM signal turns on the semiconductor switching device.
It is equipped with an automatic control system for off-control.

(Problem to be Solved by the Invention) In the above-mentioned constant voltage, constant frequency power supply device, when a nonlinear load is connected as a load, distortion in the output voltage v0 occurs due to harmonic current flowing through this nonlinear load. To increase. Conventional constant-voltage, constant-frequency power supplies do not have a function to compensate for the increase in distortion described above, and in order to reduce distortion, it is necessary to use a high-performance AC filter. Therefore, it was necessary to make changes to the main circuit, and an increase in cost was unavoidable.

This invention eliminates the above-mentioned drawbacks of the conventional constant voltage, constant frequency power supply, and provides compensation means in the control system without making any changes to the main circuit. It is an object of the present invention to provide a means for compensating for distortion caused by generated harmonic currents.

(Means for Solving the Problems) In order to achieve the above object, the constant voltage, constant frequency power supply device of the present invention is a semiconductor switching device that converts DC voltage into AC voltage and supplies the converted output to a load. a means for comparing the output voltage of the constant voltage, constant frequency power supply with a reference voltage and generating a control signal according to the amount of deviation; a means for generating a PWM signal according to the control signal;
means for controlling the semiconductor switching device on and off by a signal, further comprising means for detecting a harmonic component in the output voltage of the constant voltage, constant frequency power supply device, and a phase of the detected harmonic component. addition means for adding an inverted signal to the control signal, and the PWM signal is generated in response to the output of the addition means.

(Function) Based on the above configuration, the constant voltage, constant frequency power supply device of the present invention detects a control signal corresponding to the amount of deviation between the output voltage and the reference voltage and harmonic components in the output voltage. A signal obtained by inverting the phase of the harmonic component is added, a PWM signal is generated according to this added signal, and the PWM signal is
Since the semiconductor switching device is controlled on and off by the signal, it is possible to compensate for distortion in the output voltage even when a nonlinear load is connected.

(Example) Hereinafter, with reference to the drawings, an example of the constant voltage, constant frequency power supply device of the present invention will be described in detail in the order of its configuration and operation.

(Configuration of embodiment of constant voltage, constant frequency power supply device of this invention)
(FIG. 1) FIG. 1 shows an embodiment of the constant voltage, constant frequency power supply device of the present invention, and the portion surrounded by the broken line A in the figure is the portion embodying the main features of the present invention. In FIG. 1, 1 is a DC voltage source, and 2 is a semiconductor switching device, which is constructed by, for example, fringe-connecting thyristor elements SI to S4. 3 is an AC filter that removes unnecessary frequency components in the AC output converted to AC (by on/off control of the semiconductor switching device 2); 4 is a load;

This is particularly suitable when a nonlinear load is connected as the load 4.

5 to 13 show specific examples of a control system that generates an open signal according to the amount of deviation between the output voltage of the device and the reference voltage, and 5 of these is a voltage detection transformer that detects the output voltage of this device. , 6 is a rectifier circuit that rectifies this detected voltage, 7 is a reference DC voltage source, 8 is a comparator that detects the amount of deviation between the output voltage of the rectifier circuit 6 and the reference DC voltage of voltage source 7, and 9 is this deviation amount. a voltage control amplifier that amplifies and outputs a control signal; 10 is a multiplier that multiplies the reference sine wave signal generated by the sine wave generation circuit 11 and the output control signal of the voltage control amplifier 9;
Reference numeral 13 denotes a PWM signal generation circuit that generates a PWM signal by comparing the level of the output sine wave of the multiplier lθ and the carrier wave generated by the carrier wave generation circuit 12. This PWM signal causes the switching element 81 of the semiconductor switching device 2 to
- Controls on/off of S4.

The above configuration is already known, but as mentioned above, this configuration does not have the function of compensating for distortion based on harmonic current caused by a nonlinear load. However, it is necessary to make changes to the circuit components of the main circuit.

Therefore, in the apparatus shown in FIG. 1 which is an embodiment of the present invention, the above-mentioned distortion is compensated for without making any changes to the main circuit by providing the following compensation means in the control system. That is, 20 is a band rejection filter as a means for detecting harmonic components in the output voltage of this constant voltage, constant frequency power supply device, which blocks the fundamental wave components in the output of the voltage detection transformer 5 and eliminates harmonic components. It allows wave components to pass through.

21 is an amplifier capable of inverting the phase of the harmonic component that is the output of the band-rejection filter 20 and adjusting its gain;
is an adder that adds the sine wave signal that is the output of the multiplier 10 and the output signal of the amplifier 2 with opposite polarities,
By comparing the level of the output signal of the adder 22 and the output carrier wave of the carrier wave generation circuit 12, the PWM signal generation circuit 13 generates a PW signal.
An M signal is generated, which controls the semiconductor switching device 2 on and off.

(Operation of the embodiment of the constant voltage, constant frequency power supply device of the present invention)
(Figures 1 and 2) In the above configuration, when distortion occurs in the output voltage v0 due to reasons such as a nonlinear load being connected, as shown in Figure 2 (a), the output voltage The harmonic component included in v0 and extracted by the bandpass filter 2o is indicated by V.h in the figure (bl), and the signal whose phase is inverted by this harmonic component V.h in the amplifier 2 is shown in the figure (c). ) is indicated by Vh. This signal Vh is added to the output sine wave V1 of the multiplier IO in an adder 22 with a polarity that cancels out its harmonic components, and the level of the added output V2 and the carrier wave generated by the carrier wave generation circuit 12 is compared. PWM signals are obtained. By controlling the semiconductor switching device 2 on and off using this PWM signal, the output voltage V is controlled. It is possible to reduce harmonic components contained in

In this case, the more the harmonic components are reduced, the more the commutation current to the semiconductor switching device 2 increases. However, the amplifier 21 is configured to have an adjustable gain, so that the gain of the detected harmonic components can be adjusted appropriately. By setting this value, unnecessary increases in commutation current can be prevented.

Also, the output voltage V. does not contain harmonic components, the output vh of the amplifier 21 becomes zero, and the output Vh of the adder 22
2 is only the fundamental wave component, and P controls the switching device 2 on and off by comparing the level of this and the carrier wave.
A WM signal is obtained.

Note that the device shown in FIG. 1 operates in the same manner as described above even when non-theoretical harmonics are generated, and no special measures are required to suppress the generation of harmonics.

(Effects of the Invention) As described above, according to the constant voltage, constant frequency power supply device of the present invention, a control signal corresponding to the amount of deviation between the output voltage of the device and the reference voltage and a harmonic component in the output voltage are generated. A PWM signal is generated according to the added signal, and the semiconductor switching device is controlled on and off by this PWM signal, so that non-linear loads can be avoided. The increase in distortion of the output voltage due to harmonic current flowing through the load can be suppressed by a simple configuration without using means that involve changing the main circuit such as using a high-performance AC filter. can be compensated.

Furthermore, by appropriately setting the gain of the detected harmonic component, the increase in commutation current caused by the compensation means for the increase in distortion can be automatically limited to within a certain range, thereby preventing overload of the semiconductor switching device. It can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the constant voltage, constant frequency power supply device of the present invention, and FIGS. 2(a), (b), and (c) are waveform diagrams illustrating the operation of the device in FIG. be. Explanation of symbols 1: DC voltage source, 2: Semiconductor switching device, 3:
AC filter, 4: Load, 5: Voltage detection transformer, 6:
rectifier circuit, 7: reference DC voltage source, 8: comparator, 9: pressure control amplifier, 10: multiplier, 11: sine wave generation circuit,
12: Carrier wave generation circuit, 20: Band removal filter, 21
: Amplifier, 22: Adder. Figure 1 Figure 2

Claims (2)

[Claims] (1) A semiconductor switching device that converts DC voltage to AC voltage and supplies the converted output to a load, and means that compares the output voltage of this power supply device with a reference voltage and generates a control signal according to the amount of deviation. a means for detecting a harmonic component in the output voltage of the power supply; an adding means for adding a signal obtained by inverting the phase of the detected harmonic component to the control signal; and an output signal of the adding means. A constant voltage, constant frequency power supply device comprising: means for generating a PWM signal in response to the PWM signal; and means for controlling the semiconductor switching device on and off using the PWM signal. (2) The constant voltage, constant frequency power supply device according to claim (1), wherein the gain of the detected harmonic component is adjustable.