CN103346683B - Parallel connection PWM rectifier zero sequence circulation control method - Google Patents

Abstract

The present invention discloses a kind of parallel connection PWM rectifier zero sequence circulation control method, and it includes step: gather three-phase input current I_la、I_lbAnd I_lc, by zero-sequence current controller according to three-phase input current I_la、I_lbAnd I_lcCalculate " 111 " zero vector at whole zero vector percentage η；By DQ controller and SVPWM adjustment unit according to sampled value V of VD_bus, the set-point V of VD_ref, three-phase input current I_la、I_lbAnd I_lcCalculate the ON time T of zero vector in switch periods_o, the ON time T of two non-zero in sector, place₁And T₂；By zero vector allocation unit according to η signal and T_oSignal calculates the ON time T of " 111 " zero vector_o1The ON time T of " 000 " zero vector_o2, by T_o1Signal and T_o2Signal output sends out ripple unit to SVPWM；SVPWM sends out ripple unit and utilizes input signal T_o1、T_o2、T₁And T₂, export the pwm signal needed for rectifier bridge.The present invention realizes simply, realizes low cost and reliability height.

Description

Parallel connection PWM rectifier zero sequence circulation control method

Technical field

The present invention relates to zero sequence ring flow control technology, especially relate to a kind of three-phase and input without transformation without center line The PWM rectifier zero sequence circulation control method that device isolation input and output are directly in parallel.

Background technology

Three-phase controls to be difficult point without the zero sequence circulation of the PWM rectifier parallel connection that center line inputs.Zero sequence circulation meeting The power consumption of increase system, magnetics, filter capacitor even switching device all may be due to overcurrent damage.

Existing employing dq controls and structured flowchart such as Fig. 1 institute of unit controller of SVPWM modulation Show, V_refIt is the set-point of commutator output, V_busIt is the instantaneous value sampled of output voltage (busbar voltage), I_la、I_lb、I_lcIt is the inductor current value of three-phase input respectively, T_oIt it is the null vector of modulation sector, output vector place Amount ON time, T₁And T₂It is effective vector ON time of modulation sector, output vector place, PWM1, PWM2, PWMx are the pwm signals needed for rectifier bridge.But, this dq controlling party rule cannot Suppression zero-sequence current.

For above-mentioned technical problem, common solution is to use transformer isolation at input side, this Although method can completely inhibit zero sequence circulation, but can be greatly increased cost and the volume of system, the most also It is not appropriate for modularized design.

The PWM rectifier that three-phase inputs without center line is in parallel, if not using transformer isolation, mutual Zero sequence circulation can be very big, and industry proposed a lot of solution, and some control strategy complexity are not easily accomplished, Stability is relatively low；Some employing centralized Control schemes, reliability is low and is not suitable for modularized design.

Summary of the invention

The technical problem to be solved is to propose a kind of three-phase to isolate defeated without center line input transless Enter the PWM rectifier zero sequence circulation control method that output is the most in parallel, control at common commutator unit On the basis of do not increase any sensor, method realizes simple, reliable, and applicable modularized design.

The present invention adopts the following technical scheme that realization: a kind of PWM rectifier zero sequence circulation controlling party in parallel Method, it includes step:

A, collection three-phase input current I_la、I_lbAnd I_lc, by zero-sequence current controller according to three-phase input current I_la、I_lbAnd I_lcCalculate " 111 " zero vector at whole zero vector percentage η；

B, by DQ controller and SVPWM adjustment unit according to sampled value V of VD_bus、 The set-point V of VD_ref, three-phase input current I_la、I_lbAnd I_lcCalculate in switch periods zero The ON time T of vector_o, the ON time T of two non-zero in sector, place₁And T₂；

C, by zero vector allocation unit according to η signal and T_oWhen signal calculates the conducting of " 111 " zero vector Between T_o1The ON time T of " 000 " zero vector_o2, by T_o1Signal and T_o2Signal exports to SVPWM Send out ripple unit；

D, SVPWM send out ripple unit and utilize input signal T_o1、T_o2、T₁And T₂, needed for exporting rectifier bridge Pwm signal.

Wherein, step A specifically includes:

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)；

" 111 " zero vector is calculated shared by whole zero vector according to zero-sequence current Io by zero-sequence current controller Percentage ratio η: η=(0-I_x)*K_p+ 0.5, K_pBeing the proportionality coefficient of zero-sequence current controller, 0.5 is η Feedforward value.

Wherein, step B includes:

Calculate regulated quantity U under d/q coordinate system_dAnd U_q, transform to and obtain U under α/β coordinate system_αAnd U_β；

Calculate sector number sec, utilize sector number sec just can calculate T according to this formula following₁And T₂, 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 formula_dcIt is busbar voltage sampled value, T_sIt it is switch periods.

Wherein, if T₁+T₂>T_s, need T₁And T₂It is normalized, obtains zero vector simultaneously ON time: $\left\{\begin{array}{c}{T}_1=T_1\frac{T_s}{(T_1+T_2)}\\ T_2=T_2\frac{T_s}{(T_1+T_2)}\\ T_0=T_s-T_1-T_2\end{array}\right..$

Wherein, step C is to utilize η to calculate T_o1And T_o2: T_o1=η*T_o, T_o2=(1-η)*T_o。

Wherein, T is utilized_o1、T_o2、T₁And T₂Calculate the ON time T of three brachium pontis_o1+T₁+T₂、T_o1+T₂ And T_o1, then according to each phase brachium pontis ON time allocation table in different sectors determine respectively A, B, The ON time of C three-phase.

Compared with prior art, there is advantages that

The present invention is a kind of zero sequence circulation control strategy based on SVPWM modulation, uses the zero of band feedforward Sequence current controller only need to control the zero-sequence current of unit and can realize.The present invention need not to increase extra Sensor, it is achieved simple and realize with low cost, has the advantage that reliability is high, be beneficial to modularized design.

Accompanying drawing explanation

Fig. 1 is the structured flowchart of prior art；

Fig. 2 is the structural representation of the present invention；

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

Detailed description of the invention

As in figure 2 it is shown, the present invention is by zero-sequence current controller, " 111 " zero vector (its in regulation To In, zero vector has two, is " 111 " and " 000 " respectively, and 000,111 here are to represent three-phase The on off state of upper three upper brachium pontis) percentage realizes, comprising: the zero sequence electricity being sequentially connected with Stream controller, zero vector allocation unit and SVPWM send out ripple unit, and with zero vector allocation unit and SVPWM sends out DQ controller and the SVPWM adjustment unit (being again bus controller) that ripple unit is connected.

Wherein, sampled value I that the input that zero-sequence current controls is three-phase input A, B, C phase current values_la、 I_lbAnd I_lc, its output be η signal to zero vector allocation unit, η signal is that " 111 " zero vector is whole zero Vector percentage；And the input signal of DQ controller and SVPWM adjustment unit is V_ref、V_bus、 I_la、I_lbAnd I_lc, V_refIt is the set-point of VD, V_busIt is the sampled value of VD, This DQ controller and SVPWM adjustment unit output T_o、T₁And T₂Signal, wherein, exports T_oLetter Number to zero vector allocation unit, T_oSignal is the ON time of zero vector in switch periods, exports T₁And T₂ Signal sends out ripple unit, T to SVPWM₁And T₂Signal is respectively the conducting of two non-zero in sector, place Time；The input signal of zero vector allocation unit is η signal and T_oSignal, exports T_o1And T_o2Extremely SVPWM sends out ripple unit, T_o1Signal is the ON time of " 111 " zero vector, T_o2Signal is " 000 " null vector The ON time of amount；And SVPWM sends out ripple unit and utilizes input signal T_o1、T_o2、T₁And T₂Signal, Pwm signal PWM1, PWM2 and PWMx needed for output rectifier bridge.

Shown in Fig. 3, in one embodiment of the invention, including step implemented as described below:

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, calculated " 111 " zero vector in whole null vector by zero-sequence current controller according to zero-sequence current Io Amount percentage η: η=(0-I_o)*K_p+0.5。

Wherein, K_pBeing the proportionality coefficient of zero-sequence current controller, 0.5 is the feedforward value of η.

Step S3, calculated regulated quantity U under d/q coordinate system by DQ controller and SVPWM adjustment unit_d And U_q, transform to and obtain U under α/β coordinate system_αAnd U_β, T can be calculated according to following mathematical formulae₁、 T₂And T_o1And T_o2。

First sector number sec is calculated

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

Here obtaining sign (M) is sign function, meets $\mathrm{sign}\left(M\right)=\left\{\begin{array}{cc}1& M\&GreaterEqual;0\\ 0& M<0\end{array}\right..$ X vows with space voltage Amount place sector number (sec) exist such 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

Then sector number sec is utilized just can to calculate T according to this formula following₁And T₂:

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

V in formula_dcIt is busbar voltage sampled value, T_sIt it is switch periods.

If T₁+T₂>T_s, then supersaturation.It is accomplished by T for this situation₁And T₂It is normalized place Reason, obtains the ON time of zero vector simultaneously:

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

Then the η utilizing step S2 to calculate calculates T_o1And T_o2:

T_o1=η*T_o

T_o2=(1-η)*T_o

Step S4, utilize T_o1、T_o2、T₁And T₂Calculate the ON time T of three brachium pontis_o1+T₁+T₂、T_o1+T₂ And T_o1.Then according to table 2(each phase brachium pontis ON time allocation table in different sectors) determine respectively The ON time of A, B, C three-phase.

Table 2

Step S5, calculate the ON time of every phase brachium pontis after, SVPWM send out ripple unit output rectifier bridge In general, SVPWM sends out ripple unit for required pwm signal PWM1, PWM2 and PWMx( Realized by DSP, MCU or other controllers, it is only necessary to PWM comparing unit is set in these controllers Comparand register value arrange).

To sum up, the three-phase that the present invention proposes is without center line input transless isolation input and output directly parallel connection PWM rectifier zero sequence circulation control method, is that a kind of zero sequence circulation based on SVPWM modulation controls plan Slightly, the zero-sequence current controller using band feedforward only need to control the zero-sequence current of unit and can realize.This Bright need not increases extra sensor, it is achieved simple and realize with low cost, has reliability high, sharp Advantage in modularized design.

The foregoing is only presently preferred embodiments of the present invention, not in order to limit the present invention, all at this Any amendment, equivalent and the improvement etc. made within the spirit of invention and principle, should be included in this Within the protection domain of invention.

Claims (6)

1. a parallel connection PWM rectifier zero sequence circulation control method, it is characterised in that include step:

A, collection three-phase input current I_la、I_lbAnd I_lc, by zero-sequence current controller according to three-phase input current I_la、I_lbAnd I_lcCalculate " 111 " zero vector at whole zero vector percentage η；

B, by DQ controller and SVPWM adjustment unit according to sampled value V of VD_bus, the set-point V of VD_ref, three-phase input current I_la、I_lbAnd I_lcCalculate the ON time T of zero vector in switch periods_o, the ON time T of two non-zero in sector, place₁And T₂；

C, by zero vector allocation unit according to η signal and T_oSignal calculates the ON time T of " 111 " zero vector_o1The ON time T of " 000 " zero vector_o2, by T_o1Signal and T_o2Signal output sends out ripple unit to SVPWM；

D, SVPWM send out ripple unit and utilize input signal T_o1、T_o2、T₁And T₂, export the pwm signal needed for rectifier bridge.

Parallel connection PWM rectifier zero sequence circulation control method the most according to claim 1, it is characterised in that step A specifically includes:

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)；

By zero-sequence current controller according to zero-sequence current I_oCalculate " 111 " zero vector at whole zero vector percentage η, η=(0-I_o)*K_p+ 0.5, K_pBeing the proportionality coefficient of zero-sequence current controller, 0.5 is the feedforward value of η.

Parallel connection PWM rectifier zero sequence circulation control method the most according to claim 1, it is characterised in that step B includes:

Calculate regulated quantity U under d/q coordinate system_dAnd U_q, transform to and obtain U under α/β coordinate system_αAnd U_β；

Calculate sector number sec, utilize sector number sec just can calculate T according to this formula following₁And T₂, computing formula is:

V in formula_dcIt is busbar voltage sampled value, T_sIt it is switch periods.

Parallel connection PWM rectifier zero sequence circulation control method the most according to claim 3, it is characterised in that if T₁+T₂＞ T_s, need T₁And T₂It is normalized, obtains the ON time of zero vector simultaneously:

Parallel connection PWM rectifier zero sequence circulation control method the most according to claim 4, it is characterised in that step C is to utilize η to calculate T_o1And T_o2, T_o1=η * T_o, T_o2=(1-η) * T_o。

Parallel connection PWM rectifier zero sequence circulation control method the most according to claim 5, it is characterised in that utilize T_o1、T_o2、T₁And T₂Calculate the ON time T of three brachium pontis_o1+T₁+T₂、T_o1+T₂And T_o1, the ON time of A, B, C three-phase is then determined respectively according to each phase brachium pontis ON time allocation table in different sectors.