JPH03212162A - Control circuit for pulse width modulation control rectifier - Google Patents

Abstract

PURPOSE:To obtain a sinusoidal input current containing no higher harmonic, even if AC input voltage to a PWM rectifier is distorted, by employing a PLL circuit when controlling the waveform of the AC input current to the rectifier according to a current command. CONSTITUTION:AC input voltage to a PWM rectifier 6 is detected at the joint of reactors 3, 5 and an R phase detection voltage is inputted to a PLL circuit 40, which then provides an output to a multiplier 12 in order to produce an R phase current command. A T phase current command is produced similarly by multiplying the output from a PLL circuit 50, which receives an AC input voltage from the PWM rectifier 6, and the output from a voltage regulator 20 at a multiplier 32. By such arrangement, AC input current to the PWM rectifier 6 can be made sinusoidal regardless of the distortion of voltage waveform.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pulse width modulation controlled rectifier that does not cause waveform distortion in input alternating current when converting alternating current to direct current through pulse width modulation control.

[Conventional technology]

FIG. 3 is a circuit diagram showing a conventional example of control of a pulse width modulation controlled rectifier.

In FIG. 3, three-phase AC power from an AC power source 2 passes through reactors 3 and 5 and a capacitor 4, and is input to a pulse width modulation control rectifier (hereinafter abbreviated as a PWM rectifier) 6. The DC power converted by 6 is supplied to a load 7.

This PWM rectifier 6 has a rectifying part formed by connecting six sets of anti-parallel transistors 6T and diodes 6D in a three-phase bridge, and a resistor and a constant voltage diode on the DC output side of the rectifying part. The configuration includes a voltage detection circuit 6v, which is controlled in the following manner.

That is, the sinusoidal waveform R-phase input voltage of the PWM rectifier 6 is transferred to the voltage detector 11 (generally, an instrument transformer is used to insulate the AC voltage and transform it to an appropriate voltage).
is detected. On the other hand, since the voltage regulator 20 outputs a signal for adjusting the DC output voltage of the PWM rectifier 6 detected by the voltage detection circuit 6v to a desired value, the output of the voltage regulator 20 and the voltage detector 11 By multiplying the R phase voltage detected by the multiplier 12, the R phase voltage of the sine waveform is
Phase current command value is obtained.

The adder 14 calculates the deviation between this R-phase current command value and the R-phase current detection value detected by the current transformer 13, and inputs this deviation to the t-flow adjustment unit 15, which is composed of a proportional-integral calculator. When you input , the corresponding phone 2i? The regulator 15 outputs an R-phase control signal that makes the input deviation zero.

The comparator 16 forms a pulse width modulated pulse train by comparing the magnitude relationship between the triangular waveform carrier output from the carrier wave oscillator and this R-phase control signal.

Regarding the T phase, similar to the R phase described above, the T phase of the sine waveform
A phase input voltage is detected by a voltage detector 31, and a T-phase current command value obtained by a multiplier 32 and a T-phase current command value obtained by a current transformer 33 are obtained.
An adder 34 calculates the deviation from the detected phase current value. A T-phase control signal that makes this deviation zero is obtained from the current regulator 35,
The comparator 36 obtains a pulse width modulation signal for the T phase.

The S-phase control signal can be easily obtained by inputting the R-phase control signal and the T-phase control signal to the adder 21.

Therefore, the comparator 26 obtains the S phase pulse width modulation signal from the S phase control signal outputted from the adder 21.

These R-phase, S-soma, and T-phase pulse width modulation signals are applied to each transistor 6'F constituting the PWM rectifier 6 through a pulse distribution circuit 23, and are sequentially turned on and off. , since alternating current is converted to direct current, this P
The input terminal to the WM rectifier 6 has a sine waveform, and control is performed so that the human power factor is 1.

[Problem to be solved by the invention]

In the conventional circuit shown in FIG. 3, the AC input voltage of the PWM rectifier 6 is detected and used as the current command value for controlling the PWM gfL device 6.

By the way, the AC input ii ′fL of this PWM rectifier 6
The waveform is controlled to faithfully reproduce the waveform of the current command value input to the adder 14 or 34, so if there is distortion in the waveform of the AC input voltage at the voltage detection point, that is, the PWM rectifier 6, this The waveform distortion is reflected in the waveform of the current command value, and as a result, the AC input current waveform of the PWM rectifier 6 is distorted from a sine wave, causing problems including harmonics corresponding to this distortion.

Therefore, an object of the present invention is to enable the input current waveform to be controlled to a sine waveform that does not include harmonics even if the AC input voltage waveform of the PWM rectifier is distorted.

[Means for Solving the Problem] In order to achieve the above object, the control circuit of the present invention has the following features:
Adjustment means for making an AC input current of a rectifier made of semiconductor switch elements match a current command value obtained from an AC voltage, and this ill! A pulse width modulation control rectifier comprising a pulse width modulation circuit which receives the output signal of the f+ means and a carrier wave as input, and converts an AC input into a DC input by applying an output signal of the pulse width modulation circuit to the rectifier. A phase-locked loop circuit is provided to manually input the AC side voltage of the rectifier, and the output of this phase-locked loop circuit is used for the current command value.

[Effect]

This invention uses a phase-locked loop circuit when creating a current command value from the AC input voltage of a pulse width modulation control rectifier and controlling the waveform of the AC input current of the rectifier according to this current command value. , Even if there is waveform distortion in the AC input voltage, as long as the frequency does not change, the rL current command value formed by this phase-locked loop circuit is synchronized with the input voltage and has no waveform distortion (that is, a sine waveform). becomes.

〔Example] FIG. 1 is a circuit diagram showing an embodiment of the present invention.

In this Figure 1, AC 1t'tA2, reactor 3
and 5, capacitor 4, PWM rectifier 6, transistor 6T and diode 6D that constitute this, voltage detection circuit 6V, load 7, multipliers 12 and 32, current transformers 13 and 33
, adders 14, 21, and 34, current regulators 15, 35, comparators 16, 26, and 36, voltage regulator 20, carrier wave oscillator 22, and pulse distribution circuit 23 are the same as the conventional circuit described in FIG. Since these are the same as in the case, their explanation will be omitted.

In the present invention, the AC input voltage of the PWM rectifier 6 is detected at the same point as the conventional circuit shown in FIG. The output of this PLL circuit 40 is given to the multiplier 12 to create an R-phase current command value.

Similarly, the T-phase current command value is created by multiplying the output of the PLL circuit 50, which receives the AC input voltage of the PWM rectifier 6, and the output of the voltage regulator 20 in the multiplier 32.

Figure 2 shows the PLL used in the example circuit shown in Figure 1.
FIG. 2 is a block diagram illustrating the configuration of a circuit.

In FIG. 1, the phase difference detector 41 detects the AC voltage detected from the AC input side of the PWM rectifier 6 and the
The AC voltage output from the circuit is inputted to detect the phase difference between the two human forces, and the phase adjuster 42 outputs a control signal to make this phase difference zero.

A voltage-frequency converter (hereinafter abbreviated as a V/F converter) 43 inputs this control signal and outputs a pulse signal with a frequency corresponding to this input, which is then stored in a memory 45 via a counter 44. Given.

This memory 45 stores the sine wave current command value as data, and since the data is read out according to the address specified by the counter 44, this data is transferred to the D/A converter 46.
By converting it into an analog quantity, a sinusoidal waveform current command value is output.

The multipliers 12 and 32 shown in FIG.
By multiplying the signals output by the voltage regulator 20, a sinusoidal current command value with a predetermined amplitude is output.

〔Effect of the invention〕

According to this invention, the AC input voltage of the PWM rectifier is changed to P
By passing through the LL circuit, even if the AC input voltage waveform is distorted, a sinusoidal waveform current command value without waveform distortion can be extracted from this PLL circuit. Therefore, the P
The effect of making the AC input current of the WM rectifier into a sine waveform regardless of the distortion of the voltage waveform can be obtained.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an embodiment of the present invention, Fig. 2 is a block diagram showing the configuration of a PLL circuit used in the embodiment circuit shown in Fig. 1, and Fig. 3 is a pulse width modulation control diagram. 1 is a circuit diagram showing a conventional example of control of a rectifier.

Claims (1)

[Claims] 1) Comprising an adjustment means for making the AC input current of a rectifier made of semiconductor switching elements match a current command value obtained from an AC voltage, and a pulse width modulation circuit that receives the output signal of this adjustment means and a carrier wave as input. , a pulse width modulation control rectifier that applies an output signal of the pulse width modulation circuit to the rectifier to convert an AC input to DC, comprising a phase locked loop circuit that inputs the AC side voltage of the rectifier, the phase locked loop A control circuit for a pulse width modulation control rectifier, characterized in that an output of the circuit is used as the current command value.