Analysis and suppression of zero sequence circulating current in open winding PMSM drives with common DC bus

In this paper, the zero sequence circulating current in open winding (OW) permanent magnet synchronous machine (OW-PMSM) drives with common DC bus is systematically analysed for the first time. It is revealed that the zero sequence circulating current is affected by zero sequence back electromotive force (EMF), cross coupling voltages in zero sequence, from the machine side, pulse width modulation (PWM) induced zero sequence voltage and inverter nonlinearity, from the inverter side. Particularly, the influences from the cross coupling voltages in zero sequence and parasitic effect of inverter nonlinearity are investigated for the first time in this paper. Then the synthetic model of the equivalent zero sequence circuit is proposed as well. Each cause is studied independently via analytical modelling, finite element analysis and experiments. Meanwhile, to tackle this issue, the relevant suppression strategy using frequency adaptive proportional resonant controller is presented and tested on the 3kW OW-PMSM platform.