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1、IEEE TRANSACTIONS ON POWER ELECTRONICS, VOL. 30, NO. 6, JUNE 20153309Predictive Torque Control Scheme for Three-Phase Four-Switch Inverter-Fed Induction Motor Drives With DC-Link Voltages Offset SuppressionDehong Zhou, Jin Zhao, Member, IEEE, and Yang Liu, Member, IEEEAbstractThe four-switch three-p
2、hase (B4) inverter, having alower number of switches, was first presented for the possibility of reducingtheinvertercost,anditbecameveryattractiveasitcanbe utilizedinfault-tolerantcontroltosolvetheopen/short-circuitfault of the six-switch three-phase (B6) inverter. However, the balanceamong the phas
3、e currents collapses due to the fluctuation of the two dc-link capacitor voltages; therefore, its application is limited. This paper proposes a predictive torque control (PTC) scheme for the B4 inverter-fed induction motor (IM) with the dc-link voltage offset suppression. The voltage vectors of the
4、B4 inverter underthe fluctuation of the two dc-link capacitor voltages are derivedfor precise prediction and control of the torque and stator flux. The three-phase currents are forced to stay balance by directlycontrolling the stator flux. The voltage offset of the two dc-link capacitors is modeled
5、and controlled in the predictive point of view. A lot of simulation and experimental results are presented to validate the proposed control scheme.Index TermsCost function, current unbalance, four-switch inverter, induction motor (IM) drives, model predictive control (MPC).I. INTRODUCTION OVER the y
6、ears, the conventional three-phase voltage- source inverter with six switches (B6) has been found widespread industrial applications in various forms, such asmotor drives and active filters. However, in certain applications,a further cost reduction for inverter configuration is considered byusers.To
7、 achieve thisgoal,thethree-phase inverter withonly four switches was proposed by Van der Broeck and Van Wyk 1 for the purpose of minimizing the components cost, and it is named four-switch three-phase (B4) inverter in compari- son with the B6 one, as shown in Fig. 1. Although this kind of cost reduc
8、tion is at the expense of output performance, the B4 inverter can be utilized in fault-tolerant control to solve the open/short-circuit fault of the B6 inverter. The idea of the B4 inverterappliedtofault-tolerantcontrolisveryvaluableinsome critical occasions such as rail traction, and it has consequ
9、ently attracted the interest of many researchers 211.Manuscript received April 7, 2014; revised June 1, 2014 and July 1, 2014; accepted July 6, 2014. Date of publication July 14, 2014; date of current version January 16, 2015. This work was supported by the National Natural Science Foundation of Chi
10、na under Grant 61273174 and Grant 61034006. Recom- mended for publication by Associate Editor R. Kennel. The authors are with the Key Laboratory of Image Information Processing and Intelligent Control, Ministry of Education, and the School of Automation, HuazhongUniversityofScienceandTechnology,Hube
11、i430074,China(e-mail: ; ; Y).Color versions of one or more of the figures in this paper are available online at http:/ieeexplore.ieee.org.Digital Object Identifier 10.1109/TPEL.2014.2338395Fig. 1.Circuit diagrams of a B4 inverter-fed induction motor drive.The four-switch inverters are known to have
12、several disad- vantages compared to normal six-switch inverters: the voltage utilization factor is halved compared to the six-switch inverter.On the other hand, the capacitor center tap voltage is fluctuat- ing, and it destroys the balance among the motor phase currents12. The capacitor center tap v
13、oltage fluctuation increases as theloadtorquebecomeshigherorthefrequencyofaB4inverter becomes lower, and the unbalanced motor current leads to an inverter failure and torque pulsation 13. In order to mitigate the effects of the capacitor center tapvoltage fluctuation, several papers were published.
14、An adap- tive space vector modulation (SVM) approach was proposed to compensate the dc-link voltage ripple in a B4 inverter 12. Kim et al. 13 investigated motor current unbalance from the per- spective of source impedance and the voltage variation causedbythecurrentflowingthroughthecapacitor,andprop
15、osedacur- rent distortion compensation scheme. Lee et al. 14 proposed a compensation method by adjusting switching times consideringthe capacitor center tap voltage fluctuation. Wang et al. 15 in- vestigatedthecauseandeffectofthecapacitorcentertapvoltagefluctuation in analytical point of view, and t
16、he capacitor voltage offset was suppressed by employing certain switching states. However, the capacitor voltage offset suppression was achieved at the expense of the B4 inverters output performance. The works mentioned earlier were dedicated to obtain the balancedthree-phase currents of the B4 inverter, but the flux and torque control was not considered.Regarding the flux and torque control of a B4 inverter-fed IM
