CN103346683A - Parallel connection PWM rectifier zero sequence circulation control method - Google Patents

Abstract

The invention discloses a parallel connection PWM rectifier zero sequence circulation control method. The method comprises the steps that a three-phase input current of I[la], I[lb] and I[lc] is collected, the percentage eta of a 111zero vector in the whole zero vector is worked out by a zero sequence current controller according to the three-phase input current of I[la], I[lb] and I[lc]; break-over time T[o]and two nonzero vector break-over time T[1]and T[2] in a section within a switch period are worked out by a DQ controller and an SVPWM adjustment unit according to a sampling value V[bus] and a set value V[ref] of direct-current output voltage, and the three-phase input current of I[la], I[lb] and I[lc]; break-over time T[o1] of the 111 zero vector and break-over time T[o2] of a 000 zero vector are worked out by a zero vector distributing unit according to an eta signal and a T[o] signal, and a T[o1] signal and a To2 signal are output to an SVPWM wave sending unit; a PWM signal required by a rectifier bridge is output by the SVPWM wave sending unit through the input signal T[o1], the T[o2], the T[1] and the T[2]. The method is easy to achieve, low in achieving cost and high in reliability.

Description

PWM rectifier zero sequence circular current control method in parallel

Technical field

The present invention relates to zero sequence circulation control technology, especially relating to a kind of three-phase does not have the PWM rectifier zero sequence circular current control method that center line input transless is isolated the direct parallel connection of input and output.

Background technology

The zero sequence circulation control that three-phase does not have the PWM rectifier parallel connection of center line input is difficult point.Zero sequence circulation can increase the power consumption of system, and magnetic element, filter capacitor even switching device all may be owing to overcurrent damages.

The structured flowchart of the unit controller of existing employing dq control and SVPWM modulation as shown in Figure 1, V _RefBe the set-point of rectifier output, V _BusBe the instantaneous value of output voltage (busbar voltage) sampling, I _La, I _Lb, I _LcBe respectively the inductive current value of three-phase input, T _oBe the zero vector ON time of modulation sector, output vector place, T ₁And T ₂Be effective vector ON time of modulation sector, output vector place, PWM1, PWM2, PWMx are the required pwm signals of rectifier bridge.Yet this dq controlling party rule can't suppress zero-sequence current.

At above-mentioned technical problem, common solution is to adopt transformer isolation at input side, though this method can suppress zero sequence circulation fully, can increase cost and the volume of system greatly, simultaneously also and be not suitable for modularized design.

Three-phase does not have the PWM rectifier parallel connection of center line input, does not adopt transformer isolation, and mutual zero sequence circulation can be very big, and industry proposed a lot of solutions, and the control strategy complexity that has is not easy to realize that stability is lower; The employing centralized control scheme that has, reliability is low and be not suitable for modularized design.

Summary of the invention

Technical problem to be solved by this invention is to propose a kind of three-phase not have the PWM rectifier zero sequence circular current control method that center line input transless is isolated the direct parallel connection of input and output, on the basis of common rectifier unit control, do not increase any transducer, it is simple, reliable that method realizes, and suitable modularized design.

The present invention adopts following technical scheme to realize: a kind of PWM rectifier zero sequence circular current control method in parallel, and it comprises step:

A, collection three-phase input current I _La, I _LbAnd I _Lc, by the zero-sequence current controller according to three-phase input current I _La, I _LbAnd I _LcCalculate " 111 " zero vector at the shared percentage η of whole zero vector;

B, by DQ controller and the SVPWM adjustment unit sampled value V according to VD _Bus, VD set-point V _Ref, three-phase input current I _La, I _LbAnd I _LcCalculate the ON time T of zero vector in the switch periods _o, two the non-zero vectors in sector, place ON time T ₁And T ₂

C, by the zero vector allocation units according to η signal and T _oCalculated signals goes out the ON time T of " 111 " zero vector _O1The ON time T of " 000 " zero vector _O2, with T _O1Signal and T _O2Signal exports SVPWM to and sends out the ripple unit;

D, SVPWM send out ripple unit by using input signal T _O1, T _O2, T ₁And T ₂, the required pwm signal of output rectifier bridge.

Wherein, steps A specifically comprises:

Collection three-phase input current I _La, I _LbAnd I _LcAnd calculate zero-sequence current I _o: I _o=-(I _La+ I _Lb+ I _Lc);

Calculate " 111 " zero vector at the shared percentage η of whole zero vector by the zero-sequence current controller according to zero-sequence current Io: η=(0-I _x) * K _p+ 0.5, K _pBe the proportionality coefficient of zero-sequence current controller, the feedforward value of the 0.5th, η.

Wherein, step B comprises:

Calculate the regulated quantity U under the d/q coordinate system _dAnd U _q, transform under α/β coordinate system and obtain U _αAnd U _β

Calculate sector number sec, utilize sector number sec just can calculate T according to following this formula ₁And T ₂, computing formula is:

$\left\{\begin{array}{c}{T}_1=\frac{{3T}_s}{\sqrt{3}{V}_{\mathrm{dc}}}(\sin \left(\frac{\mathrm{\π}}{3}\sec \right)U_{\mathrm{\α}}-\cos \left(\frac{\mathrm{\π}}{3}\sec \right)U_{\mathrm{\β}})\\ T_2=\frac{{3T}_s}{\sqrt{3}{V}_{\mathrm{dc}}}(-\sin \left(\frac{\mathrm{\π}}{3}(\sec -1)\right)U_{\mathrm{\α}}+\cos \left(\frac{\mathrm{\π}}{3}(\sec -1)\right)U_{\mathrm{\β}})\end{array}\right.$

V in the formula _DcBe the busbar voltage sampled value, T _sIt is switch periods.

Wherein, if T ₁+ T ₂T _s, need be to T ₁And T ₂Carry out normalized, obtain the ON time of zero vector simultaneously: $\left\{\begin{array}{c}{T}_1=T_1\frac{T_s}{(T_1+T_2)}\\ T_2=T_2\frac{T_s}{(T_1+T_2)}\\ T_0=T_s-T_1-T_2\end{array}\right..$

Wherein, step C utilizes η to calculate T _O1And T _O2: T _O1=η * T _o, T _O2=(1-η) * T _o

Wherein, utilize T _O1, T _O2, T ₁And T ₂Calculate the ON time T of three brachium pontis _O1+ T ₁+ T ₂, T _O1+ T ₂And T _O1, determine the ON time of A, B, C three-phase then respectively according to the ON time allocation table of each phase brachium pontis in different sectors.

Compared with prior art, the present invention has following beneficial effect:

The present invention is a kind of zero sequence circulation control strategy based on the SVPWM modulation, and the zero-sequence current controller that adopts band to feedover only need be controlled the zero-sequence current of unit and can realize.The present invention does not need to increase extra transducer, realizes simple and realizes with low costly, has the reliability height, is beneficial to the advantage of modularized design.

Description of drawings

Fig. 1 is the prior art constructions block diagram;

Fig. 2 is structural representation of the present invention;

Fig. 3 is the schematic flow sheet of one embodiment of the invention.

Embodiment

As shown in Figure 2, the present invention is by the zero-sequence current controller, " 111 " zero vector (wherein among the adjusting To, zero vector has two, be respectively " 111 " and " 000 ", here the 000, the 111st, three on off states of going up brachium pontis on the expression three-phase) shared percentage recently realizes, it comprises: the zero-sequence current controller of Lian Jieing, zero vector allocation units and SVPWM send out the ripple unit successively, and send out DQ controller and the SVPWM adjustment unit (being bus controller again) that the ripple unit links to each other with the zero vector allocation units with SVPWM.

Wherein, the sampled value I that is input as three-phase input A, B, C phase current values of zero-sequence current control _La, I _LbAnd I _Lc, its output be the η signal to the zero vector allocation units, the η signal is that " 111 " zero vector is at the shared percentage of whole zero vector; And the input signal of DQ controller and SVPWM adjustment unit is V _Ref, V _Bus, I _La, I _LbAnd I _Lc, V _RefBe the set-point of VD, V _BusBe the sampled value of VD, this DQ controller and SVPWM adjustment unit output T _o, T ₁And T ₂Signal, wherein, output T _oSignal is to zero vector allocation units, T _oSignal is the ON time of zero vector in the switch periods, output T ₁And T ₂Signal is sent out ripple unit, T to SVPWM ₁And T ₂Signal is respectively the ON time of two the non-zero vectors in sector, place; The input signal of zero vector allocation units is η signal and T _oSignal, output T _O1And T _O2Send out ripple unit, T to SVPWM _O1Signal is the ON time of " 111 " zero vector, T _O2Signal is the ON time of " 000 " zero vector; And SVPWM sends out ripple unit by using input signal T _O1, T _O2, T ₁And T ₂Signal, the required pwm signal of output rectifier bridge---PWM1, PWM2 and PWMx.

In conjunction with shown in Figure 3, in the one embodiment of the invention, comprise following performing step:

Step S1, collection three-phase input current I _La, I _LbAnd I _Lc, and calculate zero-sequence current I _o:

I _o=-(I _la+I _lb+I _lc)。

Step S2, calculate " 111 " zero vector at the shared percentage η of whole zero vector by the zero-sequence current controller according to zero-sequence current Io: η=(0-I _o) * K _p+ 0.5.

Wherein, K _pBe the proportionality coefficient of zero-sequence current controller, the feedforward value of the 0.5th, η.

Step S3, calculate regulated quantity U under the d/q coordinate system by DQ controller and SVPWM adjustment unit _dAnd U _q, transform under α/β coordinate system and obtain U _αAnd U _β, can calculate T according to following mathematical formulae ₁, T ₂And T _O1And T _O2

At first calculate sector number sec

$\left\{\begin{array}{c}A=U_{\mathrm{\β}}\\ B=\sqrt{3}{U}_{\mathrm{\α}}-U_{\mathrm{\β}}\\ C=-\sqrt{3}{U}_{\mathrm{\α}}-U_{\mathrm{\β}}\\ X=\mathrm{sign}\left(A\right)+2\mathrm{sign}\left(B\right)+4\mathrm{sign}\left(C\right)\end{array}\right.$

Here get sign (M) is-symbol function, satisfy $\mathrm{sign}\left(M\right)=\left\{\begin{array}{cc}1& M\&GreaterEqual;0\\ 0& M<0\end{array}\right..$ X and space voltage vector place sector number (sec) exist as following table 1(sector table) shown in corresponding relation:

X	3	1	5	4	6	2
							sec	Ⅰ	Ⅱ	Ⅲ	Ⅳ	Ⅴ	Ⅵ

Table 1

Utilize sector number sec just can calculate T according to following this formula then ₁And T ₂:

$\left\{\begin{array}{c}{T}_1=\frac{{3T}_s}{\sqrt{3}{V}_{\mathrm{dc}}}(\sin \left(\frac{\mathrm{\&pi;}}{3}\sec \right)U_{\mathrm{\&alpha;}}-\cos \left(\frac{\mathrm{\&pi;}}{3}\sec \right)U_{\mathrm{\&beta;}})\\ T_2=\frac{{3T}_s}{\sqrt{3}{V}_{\mathrm{dc}}}(-\sin \left(\frac{\mathrm{\&pi;}}{3}(\sec -1)\right)U_{\mathrm{\&alpha;}}+\cos \left(\frac{\mathrm{\&pi;}}{3}(\sec -1)\right)U_{\mathrm{\&beta;}})\end{array}\right.$

V in the formula _DcBe the busbar voltage sampled value, T _sIt is switch periods.

If T ₁+ T ₂T _s, then supersaturation.Just need be to T at this situation ₁And T ₂Carry out normalized, obtain the ON time of zero vector simultaneously:

$\left\{\begin{array}{c}{T}_1=T_1\frac{T_s}{(T_1+T_2)}\\ T_2=T_2\frac{T_s}{(T_1+T_2)}\\ T_0=T_s-T_1-T_2\end{array}\right.$

The η that utilizes step S2 to calculate then calculates T _O1And T _O2:

T _o1=η*T _o

T _o2=(1-η)*T _o

Step S4, utilize T _O1, T _O2, T ₁And T ₂Calculate the ON time T of three brachium pontis _O1+ T ₁+ T ₂, T _O1+ T ₂And T _O1Then according to the table ON time allocation table of each phase brachium pontis of 2(in different sectors) determine the ON time of A, B, C three-phase respectively.

Table 2

Step S5, calculate the ON time of every phase brachium pontis after, sent out by SVPWM that the required pwm signal of ripple unit output rectifier bridge---PWM1, PWM2 and PWMx(are in general, SVPWM sends out the ripple unit and is realized by DSP, MCU or other controllers, and the comparand register value setting that the PWM comparing unit only need be set in these controllers gets final product).

To sum up, the three-phase that the present invention proposes does not have center line input transless and isolates the directly PWM rectifier zero sequence circular current control method of parallel connection of input and output, be a kind of zero sequence circulation control strategy based on the SVPWM modulation, the zero-sequence current controller that adopts band to feedover only need be controlled the zero-sequence current of unit and can realize.The present invention does not need to increase extra transducer, realizes simple and realizes with low costly, has the reliability height, is beneficial to the advantage of modularized design.

The above only is preferred embodiment of the present invention, not in order to limiting the present invention, all any modifications of doing within the spirit and principles in the present invention, is equal to and replaces and improvement etc., all should be included within protection scope of the present invention.

Claims (6)

1. a PWM rectifier zero sequence circular current control method in parallel is characterized in that, comprises step:

A, collection three-phase input current I _La, I _LbAnd I _Lc, by the zero-sequence current controller according to three-phase input current I _La, I _LbAnd I _LcCalculate " 111 " zero vector at the shared percentage η of whole zero vector;

B, by DQ controller and the SVPWM adjustment unit sampled value V according to VD _Bus, VD set-point V _Ref, three-phase input current I _La, I _LbAnd I _LcCalculate the ON time T of zero vector in the switch periods _o, two the non-zero vectors in sector, place ON time T ₁And T ₂

C, by the zero vector allocation units according to η signal and T _oCalculated signals goes out the ON time T of " 111 " zero vector _O1The ON time T of " 000 " zero vector _O2, with T _O1Signal and T _O2Signal exports SVPWM to and sends out the ripple unit;

D, SVPWM send out ripple unit by using input signal T _O1, T _O2, T ₁And T ₂, the required pwm signal of output rectifier bridge.

2. according to the described PWM rectifier zero sequence circular current control method in parallel of claim 1, it is characterized in that steps A specifically comprises:

Collection three-phase input current I _La, I _LbAnd I _LcAnd calculate zero-sequence current I _o: I _o=-(I _La+ I _Lb+ I _Lc);

Calculate " 111 " zero vector at the shared percentage η of whole zero vector by the zero-sequence current controller according to zero-sequence current Io: η=(0-I _o) * K _p+ 0.5, K _pBe the proportionality coefficient of zero-sequence current controller, the feedforward value of the 0.5th, η.

3. according to the described PWM rectifier zero sequence circular current control method in parallel of claim 1, it is characterized in that step B comprises:

Calculate the regulated quantity U under the d/q coordinate system _dAnd U _q, transform under α/β coordinate system and obtain U _αAnd U _β

Calculate sector number sec, utilize sector number sec just can calculate T according to following this formula ₁And T ₂, computing formula is:

$\left\{\begin{array}{c}{T}_1=\frac{{3T}_s}{\sqrt{3}{V}_{\mathrm{dc}}}(\sin \left(\frac{\mathrm{\&pi;}}{3}\sec \right)U_{\mathrm{\&alpha;}}-\cos \left(\frac{\mathrm{\&pi;}}{3}\sec \right)U_{\mathrm{\&beta;}})\\ T_2=\frac{{3T}_s}{\sqrt{3}{V}_{\mathrm{dc}}}(-\sin \left(\frac{\mathrm{\&pi;}}{3}(\sec -1)\right)U_{\mathrm{\&alpha;}}+\cos \left(\frac{\mathrm{\&pi;}}{3}(\sec -1)\right)U_{\mathrm{\&beta;}})\end{array}\right.$

V in the formula _DcBe the busbar voltage sampled value, T _sIt is switch periods.

4. according to the described PWM rectifier zero sequence circular current control method in parallel of claim 3, it is characterized in that, if T ₁+ T ₂T _s, need be to T ₁And T ₂Carry out normalized, obtain the ON time of zero vector simultaneously:

$\left\{\begin{array}{c}{T}_1=T_1\frac{T_s}{(T_1+T_2)}\\ T_2=T_2\frac{T_s}{(T_1+T_2)}\\ T_0=T_s-T_1-T_2\end{array}\right..$

5. according to the described PWM rectifier zero sequence circular current control method in parallel of claim 4, it is characterized in that step C utilizes η to calculate T _O1And T _O2: T _O1=η * T _o, T _O2=(1-η) * T _o

6. according to the described PWM rectifier zero sequence circular current control method in parallel of claim 5, it is characterized in that, utilize T _O1, T _O2, T ₁And T ₂Calculate the ON time T of three brachium pontis _O1+ T ₁+ T ₂, T _O1+ T ₂And T _O1, determine the ON time of A, B, C three-phase then respectively according to the ON time allocation table of each phase brachium pontis in different sectors.

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