JPH072018B2 - Control circuit of AC / DC converter - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to a control circuit for an AC / DC converter that produces a DC voltage source from an AC power supply while reducing low-order harmonic components of an AC input current by using switching means, and is particularly inexpensive and requires no adjustment. AC / DC that can be configured
The present invention relates to a control circuit of a converter. In the drawings below, the same reference numerals indicate the same or corresponding parts.

[Prior art]

The circuit configuration shown in FIG. 3 is well known as this type of AC / DC converter, and the circuit configuration shown in FIG. 4 is well known as its control circuit. This FIG. 3 shows the entire circuit configuration of the converter, in which the AC input is connected to the input section of the rectifier 03 via the AC filters 01 and ACCT02, and the output section of the rectifier 03 is connected to the boost chopper via the DC reactor 04. 05 is connected. The smoothing capacitor 06 and the load 07 are connected to the output section of the boost chopper 05, respectively. In addition, the control circuit 08 has an AC input voltage Vi, a rectifier input current Ii,
The DC output voltage Ed is input, and the on / off drive signal 8a is supplied to the step-up chopper 05. In such a configuration, the principle of producing a DC voltage source while reducing the lower harmonic components of the AC input current is as follows. Using the AC input voltage Vi as the reference sine wave, create a sine wave signal whose phase is equal to this reference sine wave and whose amplitude is adjusted so that the DC output voltage Ed becomes the specified value, and use this as the command value for the rectifier input current. The boost chopper 05 is turned on and off at a high frequency so that the actual value Ii becomes equal to the command value.
As a result, the rectifier input current becomes a sinusoidal current containing ripple components. This ripple component is smoothed by the AC filter 01, and the AC input current becomes a sinusoidal current with little distortion. FIG. 4 shows a conventional control circuit for realizing the above operation.
A configuration example of 08 will be shown. AC input voltage Vi as a reference sine wave
Is full-wave rectified through the rectifier 1 and the reference sine wave rectified signal A
Is one of the input signals of the multiplier 6. Further, the DC output voltage Ed as a positive input signal to the adder 3,
Similarly, the voltage command value 4a from the voltage setting unit 4 is given as a negative input signal, and the sum (comparison output) of the positive and negative input signals is input from the adder 3 to the output voltage regulator 5. Therefore, the output voltage adjuster 5 outputs the output voltage adjustment signal Vc as a DC signal such that the above sum becomes zero (that is, the DC output voltage Ed matches the voltage command value 4a), and this signal is output. Vc becomes the other input signal of the multiplier 6. In this way, the multiplier 6 has a similar waveform with the same phase as the reference sine wave rectified signal A, and the amplitude is the output voltage adjustment signal.
The current command value B as a signal proportional to the value of Vc is output. This current command value B becomes a negative input signal of the next adder 7, and a signal obtained by full-wave rectifying the rectifier input current (also referred to as AC input current) Ii via the rectifier 2 becomes the positive input signal of this adder 7. Become. Then, the sum (comparison output) of the positive and negative input signals is input from the adder 7 to the input current regulator 8.
Therefore, the input current regulator 8 has a waveform substantially similar to the current command value B such that the above sum is set to zero (that is, the full-wave rectified value of the AC input current Ii is matched with the current command value B). The input current adjustment signal C as an inversion signal of is output. This adjustment signal C becomes one input signal to the modulator 10,
Further, a high frequency carrier signal D of a triangular wave from the carrier signal generator is applied to the modulator 10 as the other input signal. Therefore, the modulator 10 compares the two input signals C and D, and switches between ON and OFF when the two signals C and D coincide with each other, in other words, for each cycle of the carrier signal D. The drive signal 8a is generated as a pulse train having a pulse width (that is, pulse width modulation) having a pulse width substantially proportional to the average value (of the amplitude) of the input current adjustment signal C within the cycle. Then, the drive signal 8a becomes an ON / OFF drive signal for the boost chopper 05. FIG. 5 shows operation waveforms of each part in such a configuration.
The reference sine wave signal Vi is rectified by the rectifier 1, and the reference sine wave rectified signal A as this rectified output signal and the output voltage regulator 5
The product of the output voltage adjustment signal Vc and the output voltage adjustment signal Vc becomes the waveform of the current command value B, and this becomes the command value of the AC input current Ii. The input current regulator 8 determines whether this command value B is equal to the actual AC input current.
An input current adjustment signal C is output as an output signal such that the deviation of Ii becomes zero, and the carrier signal D, which is an output signal of the carrier signal generator 9, is pulse-width modulated by this signal C to generate an ON / OFF signal for a pulse train. Which is the drive signal 8a for the boost chopper.

[Problems to be Solved by the Invention]

However, in the case of such a configuration, a multiplier is required to generate the command value B of the AC input current, and this multiplier has the following problems. (1) An offset adjustment circuit is required. (2) Temperature drift is large. (3) It is expensive. Therefore, an object of the present invention is to generate an AC voltage source from an AC current while reducing low-order harmonic components of the AC input current.
In the rectifier circuit of the / DC converter, the multiplier is replaced with a new modulator and an averaging circuit, so that the control circuit is low in cost and requires no adjusting element.

[Means for Solving the Problems]

In order to solve the above-mentioned problems, in the control circuit of the present invention, “voltage of AC power supply of sine wave (AC input voltage Vi, etc.)
To DC voltage via rectifying means (rectifier 03 etc.), and this DC voltage is switching means (step-up chopper 05 etc.)
An AC / DC converter that obtains a DC output voltage (Ed, etc.) different from the DC voltage by repeatedly connecting and disconnecting the DC output voltage by comparing the DC output voltage with a predetermined voltage command value (4a, etc.). A voltage control means (output voltage controller 5 or the like) for outputting a DC signal (Vc or the like, hereinafter referred to as output voltage control signal) that matches the latter, a swing proportional to the output voltage control signal, and the AC power supply. A current command value output means for outputting a sine wave signal (hereinafter, referred to as a current command value, such as B) having a frequency (hereinafter referred to as a power supply frequency) of the input current (AC input current supplied from the AC power supply to the rectification means Ii)) and the current command value, and outputs a signal (C, etc., hereinafter referred to as an input current adjustment signal) having a swing that matches the former to the latter and the power supply frequency. (Input current regulator 8 etc.), carrier signal generating means (carrier signal generator 9 etc.) for generating a triangular wave carrier signal (D etc.) having a predetermined amplitude, and pulse width based on a comparison between the input current adjustment signal and the carrier signal. In an AC / DC converter including a switching drive means (such as a modulator 10) that generates a modulated pulse train (such as a drive signal 8a) and gives the pulse train to the switching means to perform the intermittent operation, The current command value output means is a pulse width modulator based on a comparison between a sine wave signal having a predetermined amplitude and phase and the power supply frequency, and the carrier signal or a triangular wave carrier signal having a predetermined amplitude which replaces the carrier signal. Modulating means (modulator 11 etc.) for generating the generated pulse train (AC voltage modulation signal Aw etc.), a pulse width proportional to each pulse width of the pulse train and the output voltage adjusting signal. Averaging means (averaging circuit 12, etc.) for generating a new pulse train having a peak value proportional to, and smoothing the pulse train to obtain the signal of the power supply frequency as the current command value. To

[Action]

The present invention provides a method for producing an AC input current command value B in a control circuit of an AC / DC converter that produces a DC voltage source from an AC power source while reducing low-order harmonic components of an AC input current. Instead of using the multiplier to obtain the product of the output amount of the output voltage regulator, the reference sine wave is converted into a pulse train signal using the existing modulation signal, and the output amount of the DC output voltage regulator is averaged by this pulse train signal. It is the one obtained by converting.

EXAMPLE An example of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 1 is a block diagram showing a configuration of a control circuit as an embodiment of the present invention and corresponds to FIG.
FIG. 2 is an operation waveform diagram of each part of FIG. In FIG. 1, the difference from FIG. 4 is that a new modulator (hereinafter referred to as “first modulator”, whereas modulator 10 is referred to as “second modulator”) 11 is averaged instead of the multiplier 6. This is the point where the circuit 12 is used. That is, in this circuit, the AC input voltage Vi as the reference sine wave is
Is one input signal A of the first modulator 11 via the rectifier 1.
Next to. Further, the output signal D of the carrier signal generator 9 is supplied to the second modulator 10 as in the conventional case, and the first modulator is newly added.
It is also given to 11 as the other input signal. The DC voltage modulation signal Aw as the output signal of the first modulator 11 becomes one input signal of the averaging circuit 12, and the output voltage adjustment signal Vc from the output voltage regulator 5 is sent to the averaging circuit 12. It becomes the other input signal of. The output signal of the averaging circuit 12 becomes the input current command value B and is given to the adder 7 as a negative input signal. Next, FIG. 2 will be described. The reference sine wave signal Vi is rectified by the rectifier 1, and the rectified output signal (reference sine wave rectified signal) A is pulse-width modulated by the first modulator 11 (FIG. 2 (1)). As a result, the modulator 11 causes the carrier signal D
For each cycle of, the AC voltage modulation signal Aw is output as a pulse train signal having a pulse width substantially proportional to the average value of the amplitude of the reference sine wave rectified signal A in the cycle (FIG. 2 (2)). ). Next, in the averaging circuit 12, a pulse train signal in which the peak value of the AC voltage modulation signal Aw is proportional to the output signal (output voltage adjustment signal) Vc of the output voltage adjuster 5 as shown in FIG. After this is obtained, this signal is averaged to obtain the signal B having the power supply frequency as indicated by the broken line, and this signal B is used as the input current command value. Since the amplitude of the current command value B changes in proportion to the output amount Vc of the output voltage regulator 5, as a result, two signals A and
The product with Vc is obtained. The operations of the input current regulator 8 and the second modulator 10 are the same as in the conventional example.

【The invention's effect】

According to the present invention, in order to produce the product of the reference sine wave and the output amount of the DC output voltage regulator, the first modulator and the averaging circuit are used, and the input current control is used as the carrier signal to this modulator. Since the carrier signal for the second modulator that produces the on / off drive signal for the AC / DC converter is used from the output amount of the current regulator for use, the following effects can be obtained. (1) The cost is low because an expensive multiplier is not used. (2) Offset adjustment becomes unnecessary. (3) Temperature drift is reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of a control circuit according to an embodiment of the present invention, FIG. 2 is an operation waveform diagram of each part of FIG. 1, and FIG.
FIG. 4 is a block diagram showing the configuration of the AC / DC converter, FIG. 4 is a conventional block diagram corresponding to FIG. 1, and FIG. 5 is an operation waveform diagram of each part of FIG. 01 …… AC filter, 02 …… ACCT, 03 …… Rectifier, 04 ……
DC reactor, 05 …… boost chopper, 06 …… smoothing capacitor, 07 …… load, 08 …… control circuit, 1, 2 …… rectifier,
3, 7 ... Adder, 4 ... Voltage setting device, 5 ... Output voltage controller, 8 ... Input current controller, 9 ... Carrier signal generator,
10 ... second modulator, 11 ... first modulator, 12 ... averaging circuit.

Claims (1)

[Claims] 1. A sine-wave AC power source voltage is converted to a DC voltage through a rectifying means, and this DC voltage is repeatedly interrupted through a switching means to obtain a DC output voltage different from the DC voltage and a DC output voltage different from the DC voltage. An AC / DC converter, which compares the DC output voltage with a predetermined voltage command value, and outputs a DC signal (hereinafter referred to as an output voltage adjustment signal) that matches the former with the latter, Current command value output means for outputting a sine wave signal (hereinafter referred to as current command value) having a swing proportional to an output voltage adjustment signal and a frequency of the AC power supply (hereinafter referred to as power supply frequency); The input current supplied to the means is compared with the current command value, and a signal having the amplitude for matching the former to the latter and the power supply frequency (hereinafter referred to as the input current adjustment signal) is output. Current adjusting means, carrier signal generating means for generating a triangular carrier signal having a predetermined amplitude, pulse width modulated pulse train based on a comparison between the input current adjusting signal and the carrier signal, and the pulse train In an AC / DC converter provided with a switching drive means for applying the switching means to the switching means, the current command value output means, a sine wave signal having a predetermined amplitude and phase and the power supply frequency, Modulating means for generating a pulse train whose pulse width is modulated based on comparison with the carrier signal or a carrier signal of a triangular wave having a predetermined amplitude instead of this signal, pulse width proportional to each pulse width of the pulse train, and A new pulse train having a peak value proportional to the output voltage adjustment signal is generated, and the signal of the power supply frequency obtained by smoothing the pulse train is generated. The control circuit of the AC / DC converter characterized by comprising averaging means for a serial current command value.