CN102111064A - APFC control circuit and control method thereof based on low frequency model - Google Patents

Abstract

The invention discloses an active power factor correction (APFC) control circuit based on low frequency model. The control circuit is characterized by comprising an input voltage detection module and an input current detection module, wherein the output ends of the input voltage detection module and the input current detection module are respectively connected with the input end of a calculation part; the output end of the calculation part is connected with the input end of a pulse width modulation (PWM) generator; the output end of the PWM generator is connected with the base of a power tube; the cathode of the diode is also connected with the input end of an output voltage detection module; and the output end of the output voltage detection module is connected with another input end of the calculation part. The control circuit has no multiplier, less peripheral detection devices, low precision requirement, a simple control circuit, low cost, is suitable for the APFC of non-mutant loads such as fans, pumps, compressors and the like, and is particularly suitable for the APFC in the field of convertible frequency air-conditioners and convertible frequency refrigerators.

Description

Control circuit and control method thereof based on the APFC under the low frequency model

Technical field

The invention belongs to the technical field of frequency-changing control system, be specifically related to the control circuit and the control method thereof of passive power factor corrective under a kind of low frequency model (APFC), particularly the Active Power Factor Correction of convertible frequency air-conditioner and frequency conversion refrigerator.

Background technology

The harmonic wave that the APFC circuit can not only automatic tracking and compensating changing can also suppress flickering, compensating reactive power.The APFC circuit can improve the quality of power supply, satisfies the demanding occasion of the quality of power supply, satisfies the harmonic current limit value that National Standard low-voltage electrical and electronic equipment send " (GB17625.1 equals IEC61000-3-2).

Existing Active Power Factor Correction (APFC) technology is generally the APFC technology based on multiplier.Multiplication type APFC: adopt current regulator and voltage control loop simultaneously, wherein current regulator makes the more approaching sine wave of input current, and voltage control loop makes the voltage of output more stable.This method reference current is made up of the product of input rectifying voltage and output voltage error amplifying signal, be the voltage waveform homophase that makes after reference current and the rectification wherein from the purpose of input rectifying voltage sampling, this control method needs multiplier, peripheral detector number of packages is many, control circuit complexity and cost height, and the calculating of sampled result need being multiplied each other has increased the computational burden of controller.

Summary of the invention

One object of the present invention is to provide the control circuit of passive power factor corrective under a kind of low frequency model, and peripheral detector number of packages is few, and required precision is not high, and control circuit is simple, and cost is low.

To achieve these goals, the technical solution adopted in the present invention is: the control circuit of passive power factor corrective under a kind of low frequency model, the passive power factor corrective circuit comprises AC power, the rectification circuit that is connected with AC power, the positive output end of rectification circuit is connected with an end of inductance, the other end of inductance is connected with the collector electrode of power tube and the anode of diode respectively, the negative electrode of diode is connected with an end of resistance, the other end of resistance is connected with the negative output terminal of rectification circuit, the emitter of power tube also is connected with the negative output terminal of rectification circuit, also be provided with an electric capacity between the negative electrode of diode and the negative output terminal of rectification circuit, it is characterized in that control circuit comprises input voltage detection module and the input current detection module that is connected with AC power, the output of input voltage detection module and input current detection module is connected with the input of calculation portion respectively, the output of calculation portion is connected with the input of PWM generator, the output of PWM generator is connected with the base stage of power tube, the negative electrode of diode also is connected with the input of output voltage detection module, and the output of output voltage detection module is connected with another input of calculation portion.

Another object of the present invention is to provide the control method of passive power factor corrective under a kind of low frequency model, can simplify control method.

In order to realize this purpose, the technical solution adopted in the present invention is: the control method of passive power factor corrective under a kind of low frequency model is characterized in that this method may further comprise the steps:

A. measure input voltage zero crossing, input voltage U _In, input current I _InWith VD E _d

B. detected U _n, I _In, E _d, according to power-balance U _In* I _In=E _d* I _oCalculate output current I _o

C. pass through formula:

Calculate triggering signal duty ratio D control

The output of system PWM;

The output power controlling pipe T break-make of D.PWM, the control harmonic compensation.

The invention has the beneficial effects as follows: the present invention is with detected input voltage U _In, input current I _InWith output voltage E _dCalculate the triggering signal duty ratio by the distinctive control algolithm of the present invention, reach the control harmonic compensation thereby the control pwm signal triggers the break-make of power tube T.The present invention does not carry musical instruments used in a Buddhist or Taoist mass, and peripheral detector number of packages is few, and required precision is not high, and control circuit is simple, and low cost is applicable to the Active Power Factor Correction of not mutated loads such as blower fan, pump class, compressor.Especially be applicable to convertible frequency air-conditioner and frequency conversion refrigerator field Active Power Factor Correction.

Description of drawings:

Fig. 1 is the control circuit of passive power factor corrective circuit.

Fig. 2 is at the equivalent electric circuit of APFC circuit working when switch is opened.

Fig. 3 is at the equivalent electric circuit of APFC circuit working when switch turn-offs.

Fig. 4 is a main program block diagram of the present invention.

Embodiment

With reference to the accompanying drawings enforcement of the present invention is described in detail.

As shown in Figure 1, the passive power factor corrective circuit comprises AC power 1, the rectification circuit 2 that is connected with AC power 1, the positive output end of rectification circuit 2 is connected with an end of inductance L, the other end of inductance L is connected with the collector electrode of power tube T and the anode of diode D1 respectively, the negative electrode of diode D1 is connected with an end of resistance R, the other end of resistance R is connected with the negative output terminal of rectification circuit 2, the emitter of power tube T also is connected with the negative output terminal of rectification circuit 2, also be provided with a capacitor C between the negative output terminal of the negative electrode of diode D1 and rectification circuit 2, it is characterized in that control circuit comprises input voltage detection module 3 and the input current detection module 4 that is connected with AC power 1, the output of input voltage detection module 3 and input current detection module 4 is connected with the input of calculation portion 5 respectively, the output of calculation portion 5 is connected with the input of PWM generator 6, the output of PWM generator 6 is connected with the base stage of power tube T, the negative electrode of diode D1 also is connected with the input of output voltage detection module 7, and the output of output voltage detection module 7 is connected with another input of calculation portion 5.

Step of the present invention is:

1, at first measures input voltage zero crossing, input voltage effective value U by input voltage detection module 3 _InInput current detection module 4 is measured input current effective value I _InOutput voltage detection module 7 is measured output voltage values E _d

2, then by the input voltage effective value U of calculation portion according to the output of input voltage detection module _In, the input current effective value I of input current detection module output _InDetect the output voltage values E that exports with output voltage _d, according to power-balance U _In* I _In=E _d* I _oCalculate output current I _o

3, calculation portion is according to the U that calculates that detects _In, I _In, E _dWith the I that calculates _o, by control algolithm of the present invention

Calculate relative trigger signal dutyfactor D.Wherein L and C are inductance value and the capacitance in the passive power factor corrective circuit.

4, the output of triggering signal duty ratio D control PWM generator.

5, the output of PWM generator is connected to power tube T, the break-make of power controlling pipe T.Break-make control harmonic compensation by power controlling pipe T.

Control algolithm principle of the present invention and derivation are summarized as follows:

Input current I _InContinuously, circuit working is in CCM pattern, line voltage , input current

Along with turning on and off of switching element T, circuit has two kinds of mode of operations.

The positive and negative semiaxis symmetry of uncontrollable rectification is described at positive half period with input voltage, electric current below.Rectification output this moment transient voltage (2k π≤ω t≤2k π+π), the target of harmonic wave control is to realize input current

(2k π≤ω t≤2k π+π).Inductive current is identical with input current

According to the two states that turns on and off of Fig. 1 switch transistor T, harmonic current control divides two kinds of mode of operations:

(1) mode of operation a:T is in opening state, and switching tube is equivalent to short circuit, direct voltage U after the rectification _dAlong input inductance L short circuit, give induction charging, capacitor C discharge, powering load.Circuit can equivalence be shown in Figure 2.Because whole mode of operation transformation period

(cycle of input sinusoidal voltage), T _cVery little with respect to an electrical network cycle, at a T _cCan think U in time _dConstant, at this T _cU in time _dEqual the commutating voltage instantaneous value

, the voltage e at switch transistor T two ends _Dx, then the voltage at switch transistor T two ends has according to loop equation:

$e_{\mathrm{dx}}=\sqrt{2}{U}_{\mathrm{in}}\sin \mathrm{\ωt}-\frac{e\sqrt{2}{I}_{\mathrm{in}}\sin \mathrm{\ωt}}{\mathrm{dt}}\×L=0---\left(1\right)$

(2) mode of operation b:T is in off state, direct voltage U after the rectification _dTo capacitor C charging powering load simultaneously, the inductance L discharge for the capacitor C charging, is electric along input inductance L, can equivalence for as shown in Figure 3.At this T _cU in time _dEqual the commutating voltage instantaneous value , the voltage e at switch transistor T two ends _Dx, then the voltage at switch transistor T two ends has according to loop equation:

$e_{\mathrm{dx}}=\sqrt{2}{U}_{\mathrm{in}}\sin \mathrm{\ωt}-\frac{e\sqrt{2}{I}_{\mathrm{in}}\sin \mathrm{\ωt}}{\mathrm{dt}}\×L$

And the powering load output voltage fluctuates, and is made up of the ripple voltage of a DC quantity and one 2 frequency multiplication.DC quantity is defined as E _d, the AC portion of 2 frequencys multiplication is directly proportional with output DC stream, is inversely proportional to electric capacity of voltage regulation, for

, then output voltage can be expressed as:

$e_d=E_d-\frac{I_0}{2\mathrm{\ωC}}\sin 2\mathrm{\ωt}---\left(2\right)$

Voltage e _DxExpress with an equation group:

$\left\{\begin{array}{c}{e}_{\mathrm{dx}}=\mathrm{0,0}~{\mathrm{DT}}_c\\ e_{\mathrm{dx}}=e_d,\mathrm{DT}~T\end{array}\right.---\left(3\right)$

Can draw according to power-balance:

e _d(1-D)＝e _dx (4)

With formula (1), (2), (3) substitution formula (4):

$(E_d-\frac{I_0}{2\mathrm{\ωC}}\sin 2\mathrm{\ωt})(1-D)=\sqrt{2}{U}_{\mathrm{in}}\sin \mathrm{\ωt}-\frac{d\sqrt{2}{I}_{\mathrm{in}}\sin \mathrm{\ωt}}{\mathrm{dt}}\×L---\left(5\right)$

The abbreviation equation can get:

$D=1-\frac{\sqrt{2}\sqrt{{U_{\mathrm{in}}}^2+{\left(\mathrm{\ω}{\mathrm{LI}}_{\mathrm{in}}\right)}^2}}{E_d-\frac{I_0}{2\mathrm{\ωC}}\sin 2\mathrm{\ωt}}\sin (\mathrm{\ωt}-\mathrm{arctg}\frac{{\mathrm{\ωLi}}_{\mathrm{in}}}{U_{\mathrm{in}}})---\left(6\right)$

This algorithm speed is fast, and algorithm is simple, detection means few, and required precision is low, only needs in the one-period to detect once.Do not need multiplier, reduced the computational burden of controller, main is that cost is low.Be applicable to the Active Power Factor Correction of the equipment that blower fan, pump class, the sudden change of compressor even load are little, especially be adapted to the convertible frequency air-conditioner field.

According to one embodiment of present invention, input voltage detection module 3 adopts divider resistance to detect; Input current detection module 4 adopts Hall element; Output voltage detection module 7 adopts divider resistance; Calculation portion 5 adopts DSP TITMS320LF2401 chip to finish; The PWM generator that 6 of PWM generator adopt DSP TI TMS320LF2401 to carry.The hardware circuit connection of input voltage detection module 3, input current detection module 4, output voltage detection module 7, calculation portion 5 and PWM generator 6 is prior art, does not repeat them here.

Fig. 4 is a main program block diagram of the present invention.At first carrying out input voltage and input current detects, judge whether to be necessary power factor correction then, as unnecessary then rectification circuit self-commutation, and then carry out input voltage and input current and detect, then detect input voltage, input voltage zero crossing if necessary, calculate output current, computed duty cycle, control PWM output, and then carry out input voltage and input current and detect.

Claims (2)

1. the control circuit of passive power factor corrective under the low frequency model, the passive power factor corrective circuit comprises AC power, the rectification circuit that is connected with AC power, the positive output end of rectification circuit is connected with an end of inductance, the other end of inductance is connected with the collector electrode of power tube and the anode of diode respectively, the negative electrode of diode is connected with an end of resistance, the other end of resistance is connected with the negative output terminal of rectification circuit, the emitter of power tube also is connected with the negative output terminal of rectification circuit, also be provided with an electric capacity between the negative electrode of diode and the negative output terminal of rectification circuit, it is characterized in that control circuit comprises input voltage detection module and the input current detection module that is connected with AC power, the output of input voltage detection module and input current detection module is connected with the input of calculation portion respectively, the output of calculation portion is connected with the input of PWM generator, the output of PWM generator is connected with the base stage of power tube, the negative electrode of diode also is connected with the input of output voltage detection module, and the output of output voltage detection module is connected with another input of calculation portion.

2. the control method of passive power factor corrective under the low frequency model is characterized in that this method may further comprise the steps:

A. measure input voltage zero crossing, input voltage U _In, input current I _InWith VD E _d

B. detected U _n, I _In, E _d, according to power-balance U _In* I _In=E _d* I _oCalculate output current I _o

C. pass through formula: $D=1-\frac{\sqrt{2}\sqrt{{U_{\mathrm{in}}}^2+{\left({\mathrm{\ωLI}}_{\mathrm{in}}\right)}^2}}{E_d-\frac{I_0}{2\mathrm{\ωC}}\sin 2\mathrm{\ωt}}\sin (\mathrm{\ωt}-\mathrm{arctg}\frac{\mathrm{\ω}{\mathrm{LI}}_{\mathrm{in}}}{U_{\mathrm{in}}})$ Calculate the output of triggering signal duty ratio D control PWM generator;

The output power controlling pipe T break-make of D.PWM generator, the control harmonic compensation.

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