三相电压型PWM整流器建模和仿真研究_英文_

1、统 仿 真 学 报© Vol. 20 No. 192008年10月 Journal of System Simulation Oct., 2008第20卷第19期 系Modeling and Simulation Researchfor Three-Phase Voltage Source PWM RectifierWANG Xu1, HUANG Kai-zheng1, WANG Wan-wei2(1. College of Information Science and Engineering, Northeastern University, Shenyang 110004, C

2、hina; 2. Power Electronic Engineering, South China University of Technology, Guangzhou 510640, China)Abstract: Pulse-Width Modulated three-phase Voltage Source Rectifier (VSR) is the building blocks of the most of AC/DC/AC systems as the front-end rectifier. The major difficulty in control is caused

3、 by the nonlinearities in the rectifier model. The linear mathematical model of VSR in d-q coordinates was deduced with analysis based on the power balance equation. A new control strategy using inner current loop with state feedback decoupling and outer voltage square loop was proposed. Nonlinear i

4、nput transformation was used to derive a linear model from the original nonlinear model. The advantages of the proposed scheme include accuracy controller design, fast dynamic response and high quality of the current and voltage waveforms. A simplified algorithm was proposed for space vector PWM (SV

5、PWM)rectifier. The whole system was modeled and simulated by using the toolbox of MATLAB/SIMULINK. Simulation results show that the PWM model proposed can satisfy steady-state characteristics and fast transient response. This design scheme has some value for practical operation due to its simple imp

6、lement.Key words: VSR; power balance equation; state feedback decoupling; SVPWM; simulation三相电压型PWM整流器建模和仿真研究王 旭1，黄凯征1，汪万伟2(1.东北大学信息科学与工程学院，沈阳 110004；2.华南理工大学电力学院，广州 510640)摘 要：三相电压型PWM整流器(VSR)广泛用于AC/DC/AC系统前端整流。考虑到VSR本身非线性特点，建立适合于控制器设计上的数学模型比较困难，提出了一种状态反馈解耦控制电流内环和直流电压平方外环的电压型PWM整流器新型控制策略，基于功率平衡理论，采

7、用解耦状态反馈控制方法，分析并建立了三相电压型PWM整流器d-q坐标系下的线性化数学模型。由于采用直流电压平方外环，使典型的非线性模型线性化，控制器设计直观精确，提高了直流电压和网侧电流的跟踪能力，改善了波形。提出了一种空间矢量的简化算法，简化了运算过程。在MATLAB/ SIMULINK环境中建立了仿真模型。仿真结果表明：所设计整流器具有优良的稳态性能和快速的动态响应，实现简单，具有一定的实用价值。关键词：电压型PWM整流器；功率平衡；解耦状态反馈；空间矢量脉宽调制；仿真中图分类号：TP391.9 文献标识码：A 文章编号：1004-731X (2008) 19-5204-04Introdu

8、ctionDiode and phase-controlled converters constitute the largest segment of power electronics that interface to the electric utility system today. These converter circuits are simple, but the disadvantages are large distortion in line current and poor displacement power factor (DPF) (in the latter

9、case), which make the power factor poor. To combat these problems, the PWM rectifier various power factor correction (PFC) techniques based on active wave shaping of the line current have been proposed.The PWM rectifier offers several advantages such as: control of DC bus voltage, bi-directional pow

10、er flow, unityReceived: 2008-07-22 Revised: 2008-08-26Foundation item: Supported by the National 863 plan project（2006AA04Z183）Biographies: Wang Xu (1956-), male, Liaoning, the Han nationality, PH.D. doctor tutor, research on control of power electronics converters and ac speed regulation. Huang Kai

11、-zheng (1978-), female, Henan, the Han nationality, PH.D. research on power electronics converters.power factor, and sinusoidal line current 1-2.Many control techniques have been adopted for these rectification devices to improve the input power factor and shape the input current of the rectifier in

12、to sinusoidal waveform. In actual implementations, the direct current control scheme is widely adopted 3.The conventional rectifier model is a multi-input multi-output nonlinear system. The difficulty in controlling the rectifiers is mainly due to the nonlinearity.As reported in the excellent survey

13、 4, traditional control strategies in the direct current control scheme establish two loops: a line current inner loop for power factor compensation and an output voltage outer loop for voltage regulation. The most uses system parameters dependent Proportional Integral (PI) regulator: for the output

14、 voltage control loop, which can generate the modulation index or the amplitude of the reference current for the inner PWM input current control loops. The main task of the current inner loop is to force the currents in a three-phase ac load to follow the reference signals.This paper focuses on the

15、modeling and control of the·5204·第20卷第19期 Vol. 20 No. 19 2008年10月 WANG Xu, et al：Modeling and Simulation Research for Three-Phase Voltage Source PWM Rectifier Oct., 2008VSR. A new equation based on power balance is introduced to replace the original nonlinear equation. Then, nonlinear inpu

16、t transformation is applied to make the improved model linear. A simplified algorithm is proposed for space vector PWM rectifier. This algorithm avoids the look-up tables of sine or arc-tangent and complex calculations needed in the conventional methods by directly calculating the duty cycles of spa

17、ce voltage vectors which track the reference voltage vectors in each sector in the space vector.shows that there is no dynamics between urd and Sd, or urq and Sq.Therefore, a nonlinear input transformation can be used to modify the old input variables Sd and Sq to the new input variables urd and urq

18、. Moreover, the model shows that d-q current is related with both coupling voltages Liq and Lid, and main voltages ud and uq, besides the influence of urd and urq. urd and urq in the equations (1) and (2) can be regulated to ensure the correctness of equations (4) and (5).urd=u'rd+Liq+ud (4)1 Mo

19、deling and Control of VSR1.1 The mathematical model of VSR in d-q coordinatesurq=u'rq+Lid+uq (5)The main circuit diagram of the three-phase voltage source rectifier structure is shown in Fig. 1. Each power semiconductor switch consists of an IGBT connected in parallel with a diode. Where ua, ub

20、and uc are the phase voltages of three phase balanced voltage source, and ia, ib and ic are phase currents, vdc is the DC output voltage, R and L mean resistance and inductance of filter reactor, respectively, C is smoothing capacitor across the dc bus, RL is the DC side load, and iL is load current

21、.The following equations describe the dynamical behaviour1.3 Design of outer voltage square loop of the boost type rectifier in Park coordinated or in d-q:diEquation (3) describes the dynamics of vdc.Power Ld=udidR+Liqurd (1) dtbalance equation can be used to derive an alternate equation for diqvdcd

22、ynamics. The active power absorbed from the ac source L=uqiqRLidurq (2)dt(Pac) and the active power delivered to the converter dc-side dvdcvdc3(Pdc) are expressed by: C=+(Sdid+Sqiq) (3)dtRL233P=ui+uqiq (8) acddWhere,urd=Sdvdc,urq=Sqvdc, urd, urq and Sd, Sq 22are input voltage of rectifier, switch fu

23、nction in synchronous d12Pdc=vdcidc=Cvdcvdc+vdc (9) rotating d-q coordinate, respectively. ud, uqandid, iq are dtRLvoltage source, current in synchronous rotating d-q coordinate,The relationship between Pac and Pdc is:respectively. is angular frequency.Pac=Pdc+Ploss (10)Putting equation (4) and (5)

24、into equation (1) and (2), the nonlinear expression is such that the final relation between the controlled variables and the new inputs is linear and decoupled. Thus, the expected relations in the VSR are,diLd=idR+u'rd (6) dtdiqL=iqR+u'rq (7) dtWe can see from equation that the two axis curr

25、ent are totally decoupled. u'rd and u'rq are only related with idand iq respectively. The simple proportional-integral (PI) controllers are adopted in the current and voltage regulation.Fig. 1 Circuit schematic of three-phase two-level boost-type rectifier1.2 Decoupled state-feedback control

26、 method ofcurrent loopIn the above nonlinear model, equation (1) and equation (2) show that both input variables Sd and Sq are coupled with the state variable vdc.The fact that urd=Sdvdc and urq=SqvdcWhere Ploss includes the power loss in the resistor R as well as the switching and conduction losses

27、 in the VSR.The resistance R is always very small and thus, it is practically reasonable to neglect its power loss.The rectifier losses are larger than the power loss in R,but still they count for a small portion of the total power. Therefore, the rectifier losses can also be neglected without notic

28、eable loss of accuracy. If better accuracy is desired, the the rectifier losses can be represented by a small resistor in series with RL. The total equivalent dc-side resistance is still represented by RL. From Pac=Pdc, the following dynamic results:d1233Cvdcvdc+vdc=udid+uqiq (11)dtRL22which can be

29、rearranged in the following form:3uq223uddv2vdc+id+iq (12) vdc）=dtRLCCC2Due to uni-directional nature of vdc, Taking vdcas the variable, (12) will become linear.·5205·第20卷第19期 系 统 仿 真 学 报 Vol. 20 No. 19 2008年10月 Journal of System Simulation Oct., 2008UcPutting equation (8) into equation (1

30、2),d2222vdc+Pac (13) vdc）=dtRLCC2This is a first-order dynamic equation with vdcas the state variable as well as the output, and Pac as the input. A simple PI controller can be designed to regulate the DC voltage with no steady state error. Since ud is measurable, the actual input variable id can be

31、 derived from Pac. The result is actually the reference value of idfor the current inner control loop.Fig.2 displays inner current loop with state feedback decoupling and outer voltage square loop control system for VSR.UaUb Fig. 4 Six intervals of input three phase voltage(16)N=sign(B0)+2sign(B1)+4

32、sign(B2)As shown in Fig. 5, the signals are divided into six 60° intervals, it satisfies that the signs of the amplitudes of two signals are the same and opposite to the sign of another signal. And no sign change occurs during each interval. The value of N in every sector is unique. In interval

33、 1, for example, B0 is positive, B1 and B2 are negative.B1B2B0Fig. 2 Block diagram of double closed-loop control for three-phase VSR62154 6 22 Voltage Space-vector SynthesizationWhen the urdandurq acquired, the SVPWM method is realized through d-q to - transformation to trace the AC current command

34、exactly and regulate the DC bus voltage.Depending on the switching state on the circuit Fig. 1, the bridge rectifier leg voltages can assume 8 possible distinct states, represented as voltage vectors (V0 toV7 ). V1 toV6 are six fixed nonzero vectors, V0 and V7are two zero vectors, as shown in the Fi

35、g. 3. The input three phase voltage are divided into six 60°input intervals, as shown in Fig. 4.Defining:B0=VsB1=Vss B2=VssFig. 5 Six intervals of B0 B1 and B2The sector in which is depends on the expression (6). Compared with Fig.4, it is obvious that the corresponding relations between value

36、N and sector are seen in Table 1.Table 1 Determination of sector of based on N N sector3I1 5 4 6 2 II III IV V VI(14)x01，sgn（x）=0, x<0(15)V4Three-phase voltage can be treated as a voltage vector Vs.There are many different methods of modulation to synthesize Vs according to the different combinat

37、ions eight vectors. Among these methods, the two-phase modulation can make switching loss minimize, in which one switch should be always set ON or OFF in one working cycle. The desired reference vector is sampled in every sub-cycle Ts and realized by time averaging the three nearest space vectors in

38、 the space vector plane 5-7. For example, the reference vector shown in Fig. 3 with magnitude Vs and angle in sector, is realized by applying the active vector 1, the active vector 2 and the zero vectors. The durationsT1,T2 and TZ of the three space vectors, respectively is calculated as:T1Ts3 Vs=T2

39、 (17) Vsvdc2Fig.3 - space vector representation of the PWM bridge rectifier leg voltageThe vector synthetic method of other sector is similar. Theexpressions which is developed on the universal variableX,Y,Z are shown as following:·5206·第20卷第19期 Vol. 20 No. 19 2008年10月 WANG Xu, et al：Model

40、ing and Simulation Research for Three-Phase Voltage Source PWM Rectifier Oct., 2008XY=TsvdcZmotions, simpler calculation, easier realization withmicrocomputer, higher utilization of DC voltage.VsV (18) 200s150100ua/Via/A0.020.04 0.06 0.08 0.1t/s500-50VI-100-150-200For any reference vector, the durat

41、ion time of two space vectors are assigned as Table 2.Table 2 Assignation table of T1 and T2sector I IIIII IV VT1 -Z Z X -X -Y Y T2 X Y -Y Z -Z -X3 Simulation ResultsBased on the former analysis, the MATLAB/SIMULINK simulation model for the VSR of Fig.1with the test load was implemented using IGBT m

42、odules and following values: uRMS220V,L3mH,R0.1,C4700FRL16,vdc=700V.The following two figures summarize the results of the simulation. Fig. 6 shows the transient response of the output voltage. The second figure shows transient response of input current. In this simulation, at start time the dc bus

43、voltage rests at the diode rectifier level with a resistive load of RL=16. Then, the control action is applied keeping the load resistance and the output voltage increases to the desired dc value. Fig. 7 shows the voltage and current on line side. We can see the current of sinusoidal wave is the sam

44、e phase with the voltage.800700600vdc/V50040030020010000 0.02 0.04 0.06 0.08 0.1t/sFig. 6 Simulation result for DC-Link voltage dynamics-100Fig. 7 Simulation result for voltage and current waveform of phase AReferences:1Ricardo Luiz Alves, Ivo Barbi. A New Hybrid High Power Factor Three-Phase Unidir

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