Current Control Method for Asymmetric Dual Three-Phase Permanent Magnet Synchronous Motor in Vehicle

Based on the vector space decomposition (VSD) transformation, the phase currents of the asymmetric dual three phase permanent magnet synchronous motor (ADT-PMSM) can be mapped into three orthogonal subspaces, i.e., α-β subspace, x-y subspace and O₁-O₂ subspace. The mechanical energy conversion takes place in the α-β subspace, while in the x-y and O₁-O₂ subspaces only losses are produced. With neutral points being isolated, O₁-O₂ subspace can be omitted. So the vector control algorithm can control the α-β and x-y subspaces separately to realize the four dimensional current control. In the α-β subspace, deviation decoupling control method is employed to realize the mechanical energy conversion, which is robust to the motor parameters. In order to reduce the 5th and 7th harmonic currents caused by the inverter nonlinearity and some other factors, a resonant controller is adopted based on a new synchronous rotating coordinate transformation matrix to implement the current closed loop control strategy in the x-y subspace. The resonant controller can track sinusoidal references of arbitrary frequencies of both positive and negative sequences with zero steady-state error. It saves computational burden and reduces the complexity due to the lack of multiple Park transformations compared to the Proportional-Integral (PI) regulator implemented in both positive and negative synchronous reference frames. Besides, the proposed method doesn’t rely on the polarity of phase currents. Since the six-phase voltage source inverter can be viewed as two independent voltage source inverters with 30 degrees phase shift, three-phase decomposition SVPWM is employed to synthesize the voltage vectors in two subspaces simultaneously. The experimental results verify the effectiveness of the proposed method.