Research On Modulation Strategies For Open Winding PMSM Fed By Dual-inverter With Two Isolated DC Sources

The demands of the electric vehicles,wind energy conversions,high power drives etc.have motivated the developments of the open winding motors.For the open winding motors,the star-connected stator windings are open,and two inverters are employed to feed the motor from both the front ends and back ends of the stator windings.Thus,the voltage applied on the motor depends on the switching states of both inverters.With the merits of no zero sequence currents,high power factor and stable operating state,the open winding permanent magnet synchronous motor(OW-PMSM)fed by dual-inverter with isolated DC-link has been paid much attentions by researchers.Consequently,this dissertation mainly focuses on the drive system of OW-PMSM fed by dual-inverter with isolated DC-link,especially for the dual-inverter modulation algorithms.Since the traditional dual-inverter modulation algorithms are involved with high switching losses and high harmonic contents,the coordinated space vector pulse width modulation(CSVM)is proposed to improve the situation.With the CSVM,the reference voltage vector synthesis in single inverter system is simulated by the dual-inverter system,and the total switching times of the dual-inverter is reduce to 1/3 of the traditional modulation algorithms.Additionally,the voltage ratio of the two DC-links can be an arbitrary value.To simplify the proposed algorithms,the three-phase components of the reference voltage vector are introduced into the execution of the proposed modulation algorithms.By doing so,no sector identifications and trigonometric calculations are involved in the proposed CSVM.Experiment results are utilized to verify the effectiveness and superiority of the proposed CSVM.In consideration of the unequal dq inductances of the interior permanent magnet synchronous motor(IPMSM),the output evaluating methods based on the current ripples cannot be easily applied on the OW-IPMSM.Thus,a new evaluation criterion is defined in the dissertation,which is based on the error area enclosed by the reference voltage vector and the actual voltage vectors implemented.Simulations and experiments are used to compare the output performances among three different modulation algorithms.To suppress the common mode voltage(CMV)in the OW-PMSM with isolated DC-link,two different CMV suppression modulation algorithms are investigated:the SVM with zero instantaneous CMV outputs and the PWM with zero mean CMV outputs.To simplify these two algorithms,the three-phase components of the reference voltage vector are directly used in the executions of the algorithms.Thus,no sector identifications and trigonometric calculations appear in these modulation algorithms.Finally,simulation results are provided to compare the CMV outputs of different modulation algorithms.