Research On Control Technologies Of Six Phase Permenent Magnet Synchronous Generator

With the rapid development of micro-electronics and power electronicstechniques, the machine control systems have shaken off the traditional three phaseshackles. The multiphase generator combined with multiphase converter can meetthe requirements of high power and high reliability application. Six phase permanentmagnet synchronous generator (Six Phase PMSG) with dual Y connected and30degree phase shift has several advantages such as low voltage high power output,good performance in fault tolerant, flexible control techniques etc. It is quitesuitable for clean energy such as wind power and tidal energy generation, electricalship propulsion, more electric aircraft, electrical vehicle. At present, there havemany problems in multiphase machine control, such as pulse width modulation(PWM) digital implementation and DC bus series, the third harmonic interference infault tolerant control, poor performance in traditional PI control. This dissertationmainly focuses on the fundamental theory of six phase PMSG, multi-dimensionPWM control method, predictive control, third harmonic effects surpression in faulttolerrant control etc. The conclusions and summarized methods have directivesignificance and practical value in multiphase machine application.Based on the winding function，the machnism of magnetic-motive force (MMF)was analyzed which caused by winding space harmonics interaction with currentstime harmonics. The distribution law of six phase PMSG MMF was analyzed, andthis is the theoretical basis of following chapters. The two mass mechanical dynamicmodel was established which consists with six phase PMSG and prime mover. Byapplying orthogonal frame transformation, the phase variable models of six phasePMSG were transformed into space decoupling model, and they are the basis offollowing control strategies. The harmonics of air-gap flux density and back EMFwere analyzed by finite element analysis (FEA), at mean time, the inductances of sixphase PMSG were figured out by FEA also. By above calculation, the fixedharmonic can be eliminated by changing the winding coefficient was figured out.The design of six phase PMSG should be considered of mutual inductances ofinductance matrix.The incomplete and complete decoupling vector control methods were researcheddeeply. Firstly, the incomplete decoupling method was adopted to the two setwingdings with isolated neutral point topology, an improved control strategy withfeedforward control was proposed to eliminate the cross coupling effects. By theanalysis of each sector, the fixed coefficient variation law was deduced which the active time of the maximum four vectors (MFV) and stationary frame referencevoltage. It is difficult to implement the MFV because the pulse waves of MFV werenot center symmetrical. A improved continuous and a discrete MFV pulse widthmodulation (PWM) methods were proposed with centralized pulse waves, aftercentralized, the newly emerged basic vectors changed the law of active time andstationary frame reference voltage, and harmonic mechanism of MFV modulationwere analyzed, simulation and experiments validates the effectiveness of proposedstrategy. The two set windings with independent rectifier of Six Phase PMSG canseries the DC terminals together which increased the DC-bus voltage dramatically.However, the mid-voltage of the series two DC terminals drift frequently, a novelcontrol strategy was proposed to suppress the drift of DC-bus mid-voltage byinjecting the current in harmonic subspace.For the traditional PI control strategies of six phase PMSG were affected bymachine parameters frequently, the robust predictive current control (PCC) andmodel predictive control (MPC) were deeply researched. An improved deadbeatPCC control strategy was proposed, the discrete model of six phase PMSG wasestablished, and the process of realizing the deadbeat PCC in two steps was deducedclearly. By separating the high frequency components from currents and revising thefeedback part, an improved deadbeat PCC strategy was proposed to eliminate thesteady state error of reference and feedback currents in traditional method. A MPCstrategy for six phase PMSG was proposed based on state space variables. Thestandard form of MPC for six phase PMSG was established, and the cost functionand the parameters of contol law were studied in depth. The experiments validatethe two predictive algorithm merits, such as fast response and good robustness inparameter changing.Lastly, the fault tolerant control strategy in one phase opening mode wasresearched deeply which considering the third harmonic inductance and flux, thespace decoupling model of six phase PMSG were established, for the couplingrelationship of d-q voltage after synchronous frame transformation, to eliminate thethis coupling relationship, a second rotational transformation for d-q voltage wasproposed. According to MMF balance principle, and under the constraint of statorcopper loss minimum (SCLM) and stator current magnitude minimum (SCMM), theoptimized currents solutions for both constrains were figured out. To surppress thethird harmonic effects of flux and inductance in one phase open mode, acompensation control strategy was proposed which considering the third harmonicinductance and flux, it can be calculated offline, and simply implemented inengineering application, The compensation quantity for the closed loop control was deduced.