CN105322818A - Control method of three-phase PWM (pulse width modulation) rectification based on novel model prediction control - Google Patents

Abstract

The invention discloses a control method of a three-phase PWM (pulse width modulation) rectification based on novel model prediction control. The control method mainly consists of an outer voltage loop and a model prediction control step, wherein the outer voltage loop is a PI link, and the model prediction control is an inner current loop control. According to key points of the control method of the three-phase PWM rectifier, the algorithm is simplified on the basis of traditional finite set model prediction control, the switch actuation times is reduced, the switch frequency is reduced, the switch actions at two adjacent sampling moments are mutually associated to each other, a feedback characteristic is realized, and the switch action is not random and irregular. According to the control method of the three-phase PWM rectifier, the advantages of the finite model prediction control are maintained, the advantages such as rapidness in control algorithm and low switch loss can be achieved.

Description

A kind of control method of the three-phase PWM rectification based on New model PREDICTIVE CONTROL

Technical field

The present invention relates to three-phase voltage type PWM commutation technique, particularly relate to a kind of control method of the three-phase PWM rectification based on New model PREDICTIVE CONTROL, belong to electric electronic current change technology field.

Background technology

Along with expanding economy, the demand of high-power DC power supply rises year by year, and traditional not controlling with phased large power supply Harmonics of Input is large, and power factor is low comparatively large to electric network influencing, and current response cannot meet productive life demand slowly; And Three-phase PWM Voltage Rectifier can eliminate Harmonics of Input from root, and there is unity power factor, so be subject to paying close attention to of current power electronic applications.

Control strategy common at present has: hysteresis comparison control, Model Predictive Control, predictive current control, feed forward decoupling control, but these controls still have weak point at present: simple hysteresis comparison control input current ripple is still larger; And feed forward decoupling control, predictive current control need to increase SVPWM or SPWM link, algorithm is complicated; Although conventional finite collection Model Predictive Control dynamic response contrast is fast, algorithm on-line calculation causes greatly delay control effects, and need higher switching frequency just can have good control effects in addition, switching loss is large.

Summary of the invention

For the deficiency of existing control strategy, the object of the invention is the control method providing a kind of three-phase PWM rectification based on New model PREDICTIVE CONTROL.Algorithm is simplified on the basis of conventional finite collection Model Predictive Control, reduce switch motion number of times, thus reduce switching frequency, reduce switching loss, the switch motion track of each sampling instant is interrelated has feedback characteristics, makes switch motion be no longer that Stochastic sum is irregular.

Object of the present invention can be achieved through the following technical solutions: a kind of control method of the three-phase PWM rectification based on New model PREDICTIVE CONTROL, and key step is as follows:

(S1) phase lock circuitry is utilized to obtain the zero crossing of electrical network A phase voltage ea, DSP calculates grid cycle in real time according to the zero crossing of electrical network A phase voltage ea, and change control cycle with this, calculate the magnitude of voltage (ea, eb, ec) of electrical network three-phase input according to the zero crossing of electrical network A phase voltage ea, and dress is changed to digital signal simultaneously;

(S2) input current value (ia, ib, ic) of current Hall transducer difference sampling three-phase reactor is utilized, adopt the output dc voltage value at point platen press sampling three-phase voltage type PWM rectifier DC bus capacitor two ends, and be converted to digital signal;

(S3) after completing steps (S1) and (S2), using the input of the difference of instruction DC voltage value and output dc voltage value as outer voltage, outer voltage adopts PI to control, the output that PI controls obtains the amplitude I* of reference current, and reference current amplitude I* is multiplied with electric network voltage phase information and obtains reference current i* α and i* β;

(S4) the Mathematical Modeling of Three-phase PWM Voltage Rectifier from three-phase abc rest frame (transforming to two-phase α β rest frame, and the reference current controlling to obtain according to outer voltage, three-phase alternating current side electric current, three-phase alternating current side voltage, on off state S (the k-1)=Sa (k-1) of a upper sampling instant, Sb (k-1), Sc (k-1) carry out finite aggregate Model Predictive Control, the definition k moment is current sample time, k-1 is a upper sampling instant, and the k+1 moment is next sampling instant;

(S5) threephase switch signal S (k)=Sa (k), Sb (k), Sc (k) act on switching tube is directly exported according to finite aggregate Model Predictive Control.

In described step (S1), utilize phase lock circuitry to obtain the zero crossing time of electrical network A phase voltage ea, calculate the cycle of electrical network with DSP in real time, calculate the value of electrical network input three-phase voltage simultaneously.

In described step (S2), utilize the input current value (ia, ib, ic) of current Hall transducer difference sampling three-phase reactor, adopt the output dc voltage value Vdc at electric resistance partial pressure method sampling three-phase voltage type PWM rectifier DC bus capacitor C two ends.

In described step (S3), instruction DC voltage value (Vdc_ref) and the difference of output dc voltage value (Vdc) are carried out PI control, PI controls to export the amplitude (I*) obtaining reference current, reference current amplitude (I*) is multiplied with cos (wt) and obtains reference current i* α, and reference current amplitude (I*) is multiplied with sin (wt) and obtains reference current i* β.

In described step (S4), data according to (S1), (S2), (S3) step carry out finite aggregate Model Predictive Control (FiniteControlSetModelPredictiveControl under two-phase α β rest frame, FCS-MPC), according to the principle of switch motion least number of times, according on off state S (k-1)=Sa (k-1), Sb (k-1), the Sc (k-1) in a upper sampling instant k-1 moment, found out on off state S set (k) that k sampling instant is expected to occur ^j(j=1,2,3,4), by S (k) ^jdownconvert to two-phase α β rest frame from three-phase abc rest frame and obtain S _α(k) ^j, S _β(k) ^j(j=1,2,3,4) are by this on off state S set _α(k) ^j, S _β(k) ^jas domination set.

In described step (S5), finite aggregate Model Predictive Control directly exports threephase switch signal Sa (k), Sb (k), Sc (k) act on switching tube without the need to modulator.

Compared with prior art, the invention has the beneficial effects as follows:

1, finite aggregate Model Predictive Control Algorithm operand significantly declines,

2, without the need to SVPWM or SPWM modulating unit;

3, Three-phase PWM Voltage Rectifier AC input current ripple is low, and system can realize unity power factor and run;

4, Three-phase PWM Voltage Rectifier DC side output voltage is controlled, and ripple is little;

5, switch motion number of times reduces to minimum, and switching frequency significantly reduces, and switching loss reduces.

Accompanying drawing explanation

Fig. 1 is the control method control block diagram of a kind of three-phase PWM rectification based on New model PREDICTIVE CONTROL of the present invention;

Fig. 2 is the control method algorithm flow chart of a kind of three-phase PWM rectification based on New model PREDICTIVE CONTROL of the present invention;

Fig. 3 is the design sketch of the matlab emulation DC side output voltage applying Three-phase PWM Voltage Rectifier of the present invention.

Fig. 4 is the design sketch of the matlab emulation A cross streams side input voltage and input current applying Three-phase PWM Voltage Rectifier of the present invention.

Embodiment

Below in conjunction with embodiment and accompanying drawing, the present invention is described in further detail illustrates, but embodiments of the present invention are not limited thereto.If have process or the parameter of not special detailed description it is noted that following, be all that those skilled in the art can refer to existing techniques in realizing.

As shown in Fig. 1 ~ Fig. 2, the control method control block diagram of a kind of three-phase PWM rectification based on New model PREDICTIVE CONTROL of the present invention and algorithm flow chart, key step is as follows:

(S1) phase lock circuitry is utilized to obtain the zero crossing of electrical network A phase voltage ea, DSP calculates grid cycle in real time according to the zero crossing of electrical network A phase voltage ea, and change control cycle with this, calculate the magnitude of voltage (ea, eb, ec) of electrical network three-phase input according to the zero crossing of electrical network A phase voltage ea, and dress is changed to digital signal simultaneously;

(S2) input current value (ia, ib, ic) of current Hall transducer difference sampling three-phase reactor is utilized, adopt the output dc voltage value Vdc at point platen press sampling three-phase voltage type PWM rectifier DC bus capacitor C two ends, and be converted to digital signal;

(S3) after completing steps (S1) and (S2), using the input of the difference of instruction DC voltage value Vdc_ref and output dc voltage value Vdc as outer voltage, outer voltage adopts PI to control, the output that PI controls obtains the amplitude I* of reference current, and reference current amplitude I* is multiplied with electric network voltage phase information and obtains reference current i* α and i* β;

(S4) the Mathematical Modeling of Three-phase PWM Voltage Rectifier from three-phase abc rest frame (transforming to two-phase α β rest frame, and the reference current controlling to obtain according to outer voltage, three-phase alternating current side electric current, three-phase alternating current side voltage, on off state S (the k-1)=Sa (k-1) of a upper sampling instant, Sb (k-1), Sc (k-1) carry out finite aggregate Model Predictive Control, the definition k moment is current sample time, k-1 is a upper sampling instant, the k+1 moment is next sampling instant, described in specific as follows:

A) suppose that AC reactance is L, the lower resistance such as circuit and reactance is R, and ABC triphase parameter is all equal, and system sampling frequency is Ts.Under three-phase static coordinate system (abc coordinate system), switch function S is defined as S=SaSbSc, Si (i=a, b, c)=1, Si (i=a, b, c)=0 during lower brachium pontis conducting during upper brachium pontis conducting; We can obtain switch function S and have 8 kinds, S=[000; 001; 011; 010; 110; 100; 101; 111].

First switch function S (the k-1)=SaSbSc of k-1 sampling instant is read, in order to make switch action frequency minimum, we wish that k sampling instant only has at most a brachium pontis action, the switching function value in the k moment expected according to the switch function in k-1 moment have four kinds may, as shown in table 1:

The k moment switch function that the table 1k-1 moment is expected

We can learn according to table 1: can determine according to the switching function value S (k-1) in a upper sampling instant k-1 moment four switching function values S (k) that the current sample time k moment is expected to occur ^j(j=1,2,3,4).By S (k) ^j(j=1,2,3,4) downconvert to two-phase α β rest frame from three-phase abc rest frame and obtain S _α(k) ^j, S _β(k) ^j(j=1,2,3,4), by S _α(k) ^j, S _β(k) ^jas domination set.

B) system is transformed to two-phase α β rest frame from three-phase abc rest frame, obtains ac-side current relation such as formula (1) according to Kirchhoff's second law:

$\left\{\begin{array}{c}L\frac{{\mathrm{di}}_{\mathrm{\α}}}{dt}=-{\mathrm{Ri}}_{\mathrm{\α}}-S_{\mathrm{\α}}{V}_{dc}+e_{\mathrm{\α}}\\ L\frac{{\mathrm{di}}_{\mathrm{\β}}}{dt}=-{\mathrm{Ri}}_{\mathrm{\β}}-S_{\mathrm{\β}}{V}_{dc}+e_{\mathrm{\β}}\end{array}\right.---\left(1\right)$

Wherein i _αand i _βinput current value (ia, ib, ic) for three-phase reactor transforms to the value of two-phase α β rest frame; e _αand e _βmagnitude of voltage (ea, eb, ec) for the input of electrical network three-phase transforms to the value of two-phase α β rest frame; Vdc is the DC voltage value at Three-phase PWM Voltage Rectifier DC bus capacitor C two ends; S _αand S _βfor switch function S-transformation under three-phase abc rest frame is to the value of two-phase α β rest frame; Other parameters as previously mentioned.

Formula (1) discretization is obtained the current expression (2) of k+1 sampling instant:

$\left\{\begin{array}{c}{i}_{\mathrm{\α}}(k+1)=(1-\frac{{\mathrm{RT}}_s}{L})i_{\mathrm{\α}}\left(k\right)+\frac{T_s}{L}(e_{\mathrm{\α}}-S_{\mathrm{\α}}{V}_{dc})\\ i_{\mathrm{\β}}(k+1)=(1-\frac{{\mathrm{RT}}_s}{L})i_{\mathrm{\β}}\left(k\right)+\frac{T_s}{L}(e_{\mathrm{\β}}-S_{\mathrm{\β}}{V}_{dc})\end{array}\right.---\left(2\right)$

Wherein i _α(k) and i _βk () is the input current measured value of three-phase reactor under k sampling instant two-phase α β rest frame; i _αand i (k+1) _β(k+1) be the predicted current value of three-phase reactor under k+1 sampling instant two-phase α β rest frame.

B) for making k+1 moment predicted current good track reference current i * α and i* β, objective definition function is as (3):

J＝[i _α(k+1)-i _α ^*] ²+[i _β(k+1)-i _β ^*] ²(3)

C) utilize the switch function S (k-1) of k-1 sampling instant, according to the principle of switch motion least number of times, wish that k sampling instant only has at most a brachium pontis action, two other brachium pontis is constant, obtains table 1.If the switch function S of k-1 sampling instant _i(k-1) (i=1,2 ..., 8), then corresponding S _i(k) ¹, S _i(k) ², S _i(k) ³, S _i(k) ⁴(transform under two-phase rest frame is S _α(k) ^j, S _β(k) ^j(j=1,2,3,4)) be used to the electric current predicting the k+1 moment respectively, 4 electric currents of prediction are brought target function J into and are compared, and make the minimum switch function of target function J be applied to switching tube in the k moment.

(S5) switch function S (k) is obtained according to finite aggregate Model Predictive Control, direct output switching signal S (k)=Sa (k), Sb (k), Sc (k) action switch pipe.

In step (S2), described output dc voltage Vdc samples and adopts electric resistance partial pressure, and utilizes HCPL-7840 to isolate, then makes sampled voltage adapt to the voltage range of DSP sample port through amplifier conditioning.

As preferably, the dsp processor of Texas Instruments 2000 series can be selected to carry out algorithm calculating.

In step (S3), the difference of instruction DC voltage value Vdc_ref and output dc voltage value Vdc is carried out PI control, PI controls to export the amplitude I* obtaining reference current, reference current amplitude I* is multiplied with coswt and obtains reference current i* α, and reference current amplitude I* is multiplied with sin (wt) and obtains reference current i* β.

As shown in Fig. 3 ~ Fig. 4, it is soon corresponding that the matlab applying Three-phase PWM Voltage Rectifier of the present invention emulates the VD Vdc obtained, and ripple is little, and alternating current net side voltage ea alternating current ia same-phase, input power factor is high, is approximately 1.

Those skilled in the art can make various amendment to this specific embodiment or supplement or adopt similar mode to substitute under the prerequisite without prejudice to principle of the present invention and essence, but these changes all fall into protection scope of the present invention.Therefore the technology of the present invention scope is not limited to above-described embodiment.

Claims (5)

1., based on a control method for the three-phase PWM rectification of New model PREDICTIVE CONTROL, key step comprises:

(S1) phase lock circuitry is utilized to obtain the zero crossing of electrical network A phase voltage (ea), DSP calculates grid cycle in real time according to the zero crossing of electrical network A phase voltage (ea), and change control cycle with this, calculate the magnitude of voltage (ea, eb, ec) of electrical network three-phase input according to the zero crossing of electrical network A phase voltage (ea), and dress is changed to digital signal simultaneously;

(S2) input current value (ia, ib, ic) of current Hall transducer difference sampling three-phase reactor is utilized, adopt the output dc voltage value (Vdc) at point platen press sampling three-phase voltage type PWM rectifier DC bus capacitor (C) two ends, and be converted to digital signal;

(S3) after completing steps (S1) and (S2), using the input of the difference of instruction DC voltage value (Vdc_ref) and output dc voltage value (Vdc) as outer voltage, outer voltage adopts PI to control, the output that PI controls obtains the amplitude (I*) of reference current, and reference current amplitude (I*) is multiplied with electric network voltage phase information and obtains reference current i* α and i* β;

(S4) the Mathematical Modeling of Three-phase PWM Voltage Rectifier from three-phase abc rest frame (transforming to two-phase α β rest frame, and the reference current controlling to obtain according to outer voltage, three-phase alternating current side electric current, three-phase alternating current side voltage, on off state S (the k-1)=Sa (k-1) of a upper sampling instant, Sb (k-1), Sc (k-1) carry out finite aggregate Model Predictive Control, the definition k moment is current sample time, k-1 is a upper sampling instant, and the k+1 moment is next sampling instant;

(S5) threephase switch signal S (k)=Sa (k), Sb (k), Sc (k) act on switching tube is directly exported according to finite aggregate Model Predictive Control.

2. the control method of the three-phase PWM rectification based on improved model PREDICTIVE CONTROL according to claim 1, it is characterized in that: in step (S1), phase lock circuitry is utilized to obtain the zero crossing time of electrical network A phase voltage (ea), the cycle of electrical network is calculated in real time with DSP, calculate the value of electrical network input three-phase voltage simultaneously, input current value (the ia of current Hall transducer difference sampling three-phase reactor is utilized in step (S2), ib, ic), adopt the output dc voltage value (Vdc) at electric resistance partial pressure method sampling three-phase voltage type PWM rectifier DC bus capacitor (C) two ends.

3. the control method of the three-phase PWM rectification based on improved model PREDICTIVE CONTROL according to claim 1, it is characterized in that: in step (S3), instruction DC voltage value (Vdc_ref) and the difference of output dc voltage value (Vdc) are carried out PI control, PI controls to export the amplitude (I*) obtaining reference current, reference current amplitude (I*) and cos(wt) being multiplied obtains reference current i* α, reference current amplitude (I*) and sin(wt) being multiplied obtains reference current i* β.

4. the control method of a kind of three-phase PWM rectification based on New model PREDICTIVE CONTROL according to claim 1, it is characterized in that: in step (S4), data according to (S1), (S2), (S3) step carry out finite aggregate Model Predictive Control under two-phase α β rest frame, according to the principle of switch motion least number of times, according on off state S (k-1)=Sa (k-1), Sb (k-1), the Sc (k-1) in a upper sampling instant k-1 moment, determined that on off state S set (k) occurred was expected in k sampling instant ^j, by this on off state S set (k) ^jas domination set, wherein j=1,2,3,4.

5. the control method of a kind of three-phase PWM rectification based on New model PREDICTIVE CONTROL according to claim 1, it is characterized in that: in step (S5), finite aggregate Model Predictive Control directly exports threephase switch signal S (k)=Sa (k), Sb (k), Sc (k) act on switching tube without the need to modulator.