JPS6260475A - Constant-voltage constant-frequency power unit - Google Patents

Abstract

PURPOSE:To suppress waveform distortion on a load change by variable-value controlling the currents of a capacitor connected to an output from a voltage type PWM inverter with regard to a sine-wave reference. CONSTITUTION:A constant-voltage constant-frequency power unit is constituted of a PWM control inverter 2, a reactor 3 for smoothing, a capacitor 4 for absorbing higher harmonics, an output-voltage amplitude reference 8, a sine-wave oscillator 10, a current controller 14 and a PWM signal generator 15, and supplies load 5 with sine-wave voltage. In this case, a current detecting transformer 13 is connected to the capacitor 4, and a sine-wave signal from the sine-wave oscillator 10 is used as the instantaneous-value current reference of the capacitor 4. The current signal of the capacitor and an output from the oscillator 10 are compared by the current controller 14, and the AC currents of the capacitor 4 are variable-value controlled. Accordingly, waveform distortion is suppressed even to non-linear load and a load change, thus resulting in control so as to maintain an excellent sine-wave output.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a constant voltage constant frequency insufflation 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. In Fig. 4, l is a DC power supply, 2 is a PWM control inverter connected to the DC power supply l, 3 is a smoothing reactor connected to the output of inverter 2, and 4 absorbs harmonic current of the output of inverter 2. Capacitor, 5 is load, 6 is output voltage detection transformer,
7 is a rectifier, 8 is an output voltage amplitude reference, 9 is a magnetic pressure controller, and 16 is a PWM (34
This is a pattern PWM signal generator that generates a signal.

The operation shown in FIG. 4 will be briefly explained. The inverter 2 turns the DC voltage of the DC power supply 1 ON10FF.
Generates a sinusoidally pulse modulated output voltage. Since this output voltage contains many harmonics, the waveform is improved by a smoothing reactor 3 and a harmonic absorbing condenser f4 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 isolated by the transformer 6, and the rectifier 7
! The width is detected and compared and controlled by a voltage controller 9 together with a voltage reference 8. In accordance with the output of this voltage controller 9, a pattern PWM (PWM in which the i generator 16 is modulated by a sine wave)
Generates a signal and controls the inverter 2 to ON10FF.

The above-mentioned conventional method has been improved by improving the AC voltage waveform as described in, for example, Chapter 4, Section 7.4 of "Power Electronics" published by Denkishoin on November 5, 1981.

However, the above method does not control the instantaneous value of the output voltage, but rather controls the inverter's 0N10FF signal using the rectified value of the output voltage as a feed pack, so basically it can only control the fluctuation of the output voltage, resulting in waveform distortion. Unable to control 1. 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 has an adverse effect on a load such as an electronic computer connected to the output.

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

FIG. 5 shows an example of its basic structure.

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 whose input is the corner reference, 13 is a current detection transformer, 14 is a current controller, and 15 generates 0N10FF i of inverter 2 according to input No. 46. It is a PWM bond generator.

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

The output voltage of the inverter device is detected by the transformer 6,
The voltage controller 9 compares and controls the output voltage up to t of the AC signal with the sine wave reference generated by the sine wave reference lO. The output of the 1-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. Depending on the output of the current controller 14, the PWM signal generator 15 controls the ON10FF operation of the inverter 2.

Here, unlike in Fig. 5, there is a method in which the voltage is controlled at the DC level by a constant signal of the output voltage, a sine wave signal is obtained with the output as the @width reference, and the output current of the inverter 2 is thereby controlled. However, with this method, the output current is a sine wave, but the output voltage is load dependent and is not a sine wave, especially in the case of nonlinear 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 a frequency higher than the resonance frequency due to the output side reactor 3 and condenser f4 (2), the control becomes unstable because the phase rotates by 18σ. Since it was not possible to increase the response of the control system, there was a problem that the output voltage was distorted with respect to the sine wave standard.Increasing the resonant frequency means making the filter smaller = suppressing the m-wave. It becomes difficult to do.

[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 type 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 objective is achieved by i! The output voltage waveform is controlled by controlling the current of a capacitor connected to the output of a constant voltage constant frequency power supply device configured with a pressure type PWM inverter based on a sine wave reference, and the amplitude of the capacitor current reference is changed. This allows coupling by controlling the magnitude of the output voltage.

[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. The current control unit 4 receives a capacitor current signal detected by the current converter 13 connected to the conductor f4,
The outputs of the sine wave oscillator 10 are compared, and the alternating current of the conductor f4 is subjected to additional value control. 'P at the output of the 4-flow controller 14? /
M (ON10 F of inverter 2 by I generator 15
Perform F action.

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. There is a sine wave signal that controls the current of the capacitor f4 from the second point.In Figure 1, if the current flowing through the capacitor C1 of the capacitor f4 is IC, the output voltage is 0, and the output frequency is !, then .

Since l0=2/Cv0 (1), the capacitor current! . If you control the follow-up value to a sine wave,
The output voltage v0 also becomes a sine wave. Also, by varying the voltage reference 8, the amplitude of the capacitor current reference changes, resulting in a change in the output voltage! @ can be changed.

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.

Further, it is not contrary to the spirit of the present invention even if a transformer is used to step up, step down, or insulate the output voltage instead of the smoothing reactor 30, and the leakage impedance of the transformer is used as the smoothing reactor. it is obvious.

As explained above, in a constant voltage constant frequency power supply device composed of a voltage type PWM inverter, the output voltage is changed to a sine wave waveform by controlling the current of a capacitor connected to the output by additional value based on a sine wave standard. (2) It is 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 smooth sine wave output.

Another embodiment of the invention is shown in FIG.

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

The difference between FIG. 2 and FIG. 1 is that a frequency reference 11 and a current coupling capacitor +12 are 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 based on the frequency reference 11. Therefore, according to the above flj equation, in order to keep the output voltage v0 constant against a change in frequency 1, the capacitor current must be changed. It is necessary to make it proportional to I. The AC coupling capacitor 12 cuts the DC signal.

In a desired frequency range, the amplitude of the condenser f1jt flow reference IC can be made proportional to the frequency I at t6.

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. Don't go against it.

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 the output voltage detection transformer 6. The difference is that 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 the transformer 6, and converted into DC (DC) by the rectifier 7, which becomes the feedback of the output voltage waveform.This voltage feedback and the voltage reference 8 are compared and controlled by the voltage controller 9, and are used as the capacitor current reference. As a result, it is possible to perform constant voltage control of the output even when the capacitance of the capacitor 4 changes.In this embodiment, the output voltage is detected and feedback control is performed, but the capacitor current is based on a sine wave. The point that tracking price control is performed is the same, and does not contradict the gist of the present invention.

〔Effect of the invention〕

As explained above, according to the present invention, a constant voltage constant frequency power supply device (2) configured with a voltage source PWM inverter,
It is characterized by the fact that the current of the capacitor connected to the output is additionally controlled with respect to a sine wave reference, and has the advantage that the "output" magnetic pressure can be controlled to have a sine wave waveform. The amplitude of the output voltage can be controlled by varying the capacitor current reference ffX5. 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 magnetic pressure has no harmonics of frequencies below the switching frequency of the inverter 2, and harmonics of frequencies above the relatively high switching frequency can be easily removed with a small filter. It is possible to prevent an adverse effect on the load of electronic computers, etc.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram showing two embodiments of the present invention, Figures 2 and 3 are diagrams showing two embodiments of the present invention.
The figures 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 1
1... Frequency reference 12... Father coupling capacitor 13... Current transformer 14... Current controller 15.
...PWM signal generator 16...Pattern PWM signal generator agent Patent attorney Noriyuki Hirofumi Mitsumata Figure 1 Figure 3 Figure 4

Claims (3)

[Claims] (1) In a constant voltage constant frequency power supply device consisting of a voltage type PWM inverter, a reactor connected to its output, and a capacitor, a circuit that generates a sine wave reference signal whose amplitude is the output voltage reference, and the capacitor A constant voltage, constant frequency power supply device comprising a circuit that detects a current and performs follow-up control using the sine wave reference signal. (2) In a constant voltage constant frequency power supply device comprising a voltage type PWM inverter and a reactor and a capacitor connected to its output, a means for detecting the output voltage thereof and a circuit that performs constant voltage control using the detected 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 constant voltage 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 type PWM inverter and a reactor and a capacitor connected to its output, a sine wave reference signal whose amplitude is the output voltage reference and whose frequency is the output frequency reference , a circuit that makes the amplitude of this 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. Characteristic constant voltage constant frequency power supply device.