JPH0584150B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a constant voltage constant frequency power supply device.

[Technical background of the invention and its problems]

FIG. 4 shows an example of a conventional constant voltage constant frequency power supply device configured with a voltage source PWM inverter. Fourth
In the figure, 1 is a DC power supply, 2 is a PWM control inverter connected to DC power supply 1, 3 is a smoothing reactor connected to the output of inverter 2, 4 is a capacitor that absorbs harmonic current of the output of inverter 2,
5 is a load, 6 is an output voltage detection transformer, 7 is a rectifier, 8 is an output voltage amplitude reference, 9 is a voltage controller, 1
6 is a pattern PWM signal generator that generates a PWM signal using a sinusoidally modulated pattern.

The operation shown in FIG. 4 will be briefly explained. Inverter 2
generates a sinusoidally pulse-width-modulated output voltage by turning on and off the DC voltage of the DC power supply 1. Since this output voltage contains many harmonics, the waveform is improved by a smoothing reactor 3 and a harmonic absorbing capacitor 4 connected to the output of the inverter, and a sine wave voltage is supplied to the load 5.

On the other hand, the output voltage is insulated by a transformer 6, its amplitude is detected by a rectifier 7, and compared and controlled with a voltage reference 8 by a voltage controller 9. In response to the output of the voltage controller 9, a pattern PWM signal generator 16 generates a sinusoidally modulated PWM signal to control the inverter 2 on/off.

The above conventional method is, for example, Denkishoin 1982.
Chapter 4 of “Power Electronics” published on November 25th
It is known due to the alternating current voltage waveform improvement described in Section 7.4.

However, the above method does not control the instantaneous value of the output voltage, but the inverter ON/OFF signal is controlled using the rectified value of the output voltage as feedback, so basically only the amplitude of the output voltage can be controlled.
Unable to control waveform distortion. Therefore, it is difficult to obtain a sine wave output voltage with little waveform distortion.
Another disadvantage is that the output waveform differs depending on the load, which becomes a problem especially when a nonlinear load such as a rectifier load is connected.

This waveform distortion of the output voltage adversely affects loads such as electronic computers connected to the output.

Therefore, it is possible to perform instantaneous value control of the output voltage.

FIG. 5 shows an example of its basic configuration.

In FIG. 5, the same elements as those in FIG. 4 are denoted by the same numbers, and the difference is that the detected output voltage is controlled by comparing it with a sine wave reference while alternating current.

In FIG. 5, 10 is a sine wave oscillator that receives an amplitude reference as input, 13 is a current detection transformer, 14 is a current controller, and 15 is a sine wave oscillator that receives an amplitude reference as an input.
This is a PWM signal generator that generates ON/OFF signals.

The operation shown in FIG. 5 will be briefly explained.

The output voltage of the inverter device is detected by a transformer 6, and is compared and controlled as an AC signal by a voltage controller 9 with a sine wave reference of the output voltage produced by a sine wave reference 10. The output of the voltage controller 9 serves as the output current reference of the inverter 2, and is compared and controlled by the current controller 14 with the output current detected by the current transformer 13. According to the output of the current controller 14, the PWM signal generator 1
5 controls the ON/OFF operation of inverter 2.

Here, unlike FIG. 5, there is also a method of controlling the voltage at the DC level using a rectified signal of the output voltage, obtaining a sine wave signal using the output as the amplitude reference, and controlling the output current of the inverter 2 thereby. but,
In this method, the output current is sinusoidal, but the output voltage is load dependent and is not sinusoidal, especially for non-linear loads such as rectifier loads. Therefore, in FIG. 5, it was necessary to compare and control the output voltage using an alternating current signal.

In FIG. 5, the instantaneous value of the output AC voltage is controlled, but at frequencies above the resonance frequency due to the reactor 3 and capacitor 4 on the output side, the phase rotates by 180 degrees, making the control unstable. Therefore, since the response of the control system cannot be increased, there is a problem in that the output voltage is distorted with respect to the sine wave reference. Increasing the resonance frequency requires making the filter smaller, making it difficult to suppress high frequencies.

[Purpose of the invention]

An object of the present invention is to stably control the output voltage with respect to a sine wave reference in order to minimize distortion of the output voltage waveform in a constant voltage constant frequency power supply device configured with a voltage source PWM inverter. The object of the present invention is to provide a constant voltage constant frequency power supply device that can perform the following functions.

[Summary of the invention]

According to the present invention, the above object is to control the output voltage waveform by controlling the current of the capacitor connected to the output of a constant voltage constant frequency power supply device configured with a voltage source PWM inverter based on a sine wave. death,
This can be achieved by controlling the magnitude of the output voltage by changing the amplitude of the capacitor current reference.

[Embodiments of the invention]

An embodiment of the present invention is shown in FIG. 1 and 5 are the same elements; the difference is that the current detection transformer 13 is connected to the capacitor 4 instead of the output of the inverter 2, and the voltage detection and voltage The point is that the controller is omitted.

The operation shown in FIG. 1 will be briefly explained. Using the voltage reference 8 as an amplitude reference, a sine wave oscillator 10 obtains a sine wave signal of a predetermined frequency. This sine wave signal becomes the instantaneous value current reference for the capacitor 4. Current controller 14
compares the capacitor current signal detected by the current transformer 13 connected to the capacitor 4 with the output of the sine wave oscillator 10, and controls the alternating current of the capacitor 4 by additional value. The output of the current controller 14 causes the PWM signal generator 15 to turn the inverter 2 ON/OFF.

The difference between Fig. 1 and Fig. 5 is that in Fig. 5, the output current of the inverter 2 is directly controlled by the output of the voltage controller 9, whereas in Fig. 1, the voltage reference 8 is used as the amplitude reference. The point is that the current in the capacitor 4 is controlled by a sine wave signal. In Figure 1, if the capacitance of the capacitor 4 is C, the flowing current is I _c , the output voltage is Vo and the output frequency is I _c = 2πCVo...(1), so the capacitor current I _c is transformed into a sine wave. If follow value control is performed, the output voltage Vo will also become a sine wave. Also,
By varying the voltage reference 8, the amplitude of the capacitor current reference changes, making it possible to vary the amplitude of the output voltage.

On the other hand, since Equation (1) does not include a term due to the load, it is clear that the output voltage can be controlled to maintain a good sine wave with little distortion even with the rectifier load and load fluctuations.

Furthermore, instead of the smoothing reactor 3, a transformer may be used to step up, step down, or insulate the output voltage, and the leakage impedance of the transformer may be used as the smoothing reactor without going against the spirit of the present invention. it is obvious.

As explained above, in a constant voltage constant frequency power supply device configured with a voltage source PWM inverter, the output voltage is controlled to have a sine wave waveform by controlling the current of the capacitor connected to the output with a sine wave reference. This makes it possible to obtain a good sine wave output voltage with little waveform distortion.

Furthermore, waveform distortion can be suppressed even under nonlinear loads and load fluctuations, and control can be performed to maintain a good sine wave output.

Another embodiment of the invention is shown in FIG.

FIG. 2 is a configuration diagram of a constant voltage constant frequency power supply device in which the frequency is varied within a certain range, for example, at 50/60 Hz.

The difference between Fig. 2 and Fig. 1 is that the frequency reference 11
This is the point in which the AC coupling capacitor 12 is added.

The operation of FIG. 2 will be explained regarding the differences from FIG. 1. In FIG. 2, the inverter output frequency is not fixed but is varied by a frequency reference 11. In FIG.
Therefore, in equation (1) above, in order to keep the output voltage Vo constant against changes in frequency, it is necessary to make the capacitor current I _c proportional to . The AC coupling capacitor 12 cuts the DC signal and makes it possible to make the amplitude of the capacitor current reference Ic proportional to the frequency in a desired frequency range.

This embodiment differs from the embodiment shown in FIG. 1 in that the frequency is variable, but it is the same in that the capacitor current of the inverter output is subjected to additional value control based on a sine wave standard, which is contrary to the gist of the present invention. do not.

Yet another embodiment of the invention is shown in FIG.

FIG. 3 shows an example in which output voltage is detected and feedback control is performed. The difference between FIG. 3 and FIG. 2 is that an output voltage detection transformer 6, a rectifier 7, and a voltage controller 9 are added.

The operation shown in FIG. 3 will be briefly explained. The output voltage is detected by a transformer 6 and converted to direct current by a rectifier 7, providing feedback of the output voltage amplitude. This voltage feedback and a voltage reference 8 are compared and controlled by a voltage controller 9, and are used as a capacitor current reference. As a result, constant voltage control of the output can be performed even when the capacitance of the capacitor 4 changes. In this example,
Although the output voltage is detected and feedback control is performed, the point that the capacitor current is additionally controlled based on a sine wave is the same, and this does not contradict the gist of the present invention.

〔Effect of the invention〕

As explained above, according to the present invention, the voltage type
A constant-voltage, constant-frequency power supply device configured with a PWM inverter is characterized by the fact that the current of the capacitor connected to the output is controlled by additional values with respect to a sine wave reference, and the output voltage can be controlled to a sine wave waveform. has advantages. The amplitude of the output voltage can be controlled by varying the amplitude of the capacitor current reference. Therefore, a good sine wave output voltage with little waveform distortion can be obtained. Furthermore, there is also the advantage that waveform distortion can be suppressed even under nonlinear loads and load fluctuations, and control can be performed to maintain a good sine wave output voltage. As a result, the output voltage has no harmonics of frequencies below the switching frequency of inverter 2, and harmonics of relatively high frequency components above the switching frequency can be easily removed with a small filter. It is possible to prevent an adverse effect on the load on computers, etc.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG.
3 and 3 are block diagrams showing other different embodiments of the present invention, and FIGS. 4 and 5 are block diagrams of different conventional devices. 1...DC power supply, 2...Inverter, 3...Reactor, 4...Capacitor, 5...Load, 6...
...Transformer, 7...Rectifier, 8...Voltage reference, 9...
...Voltage controller, 10...Sine wave oscillator, 11...
Frequency reference, 12... AC coupling capacitor, 13
...Current transformer, 14...Current controller, 15...
PWM signal generator, 16... Pattern PWM signal generator.

Claims (1)

[Scope of Claims] 1. A circuit that generates a sine wave reference signal whose amplitude is the output voltage reference in a constant voltage constant frequency power supply device consisting of a voltage source PWM inverter and a reactor and a capacitor connected to its output. and,
A constant voltage constant frequency power supply device, comprising a circuit that detects the capacitor current and performs follow-up control using the sine wave reference signal. 2. In a constant voltage constant frequency power supply device consisting of a voltage type PWM inverter, a reactor and a capacitor connected to its output, a means for detecting the output voltage, a circuit that performs constant voltage control using the detected voltage, and a constant voltage 1. A constant voltage constant frequency power supply device comprising: a circuit that generates a sine wave reference signal according to the output of a control circuit; and a circuit that detects the capacitor current and performs additional value control on the sine wave reference signal. 3 In a constant voltage constant frequency power supply device consisting of a voltage source PWM inverter and a reactor and capacitor connected to its output, a sine wave reference signal is generated whose amplitude is the output voltage reference and the frequency is the output frequency reference. a circuit that makes the amplitude of the reference signal proportional to the frequency reference; and a circuit that detects the capacitor current and performs additional value control with respect to a sine wave reference whose amplitude is proportional to the frequency. Constant voltage constant frequency power supply.