Flux-Weakening Control for Variable Flux Reluctance Machine Considering the Second Order Harmonic in Phase Voltage

Due to the second order harmonic in the phase voltage, the voltage peak value is much higher than the amplitude of its fundamental component in the 6/4 variable flux reluctance machines (VFRMs). Conventionally, the amplitude of the fundamental component in the phase voltage is used to calculate the voltage constraint in flux-weakening control, which results in a large voltage margin and reduces the DC link voltage utilization. To deal with this problem in the VFRMs, the flux-weakening control considering the second order harmonic of the phase voltage is proposed in this paper. In this method, the voltage peak value is used to calculate the current operating points, by using which the maximum voltage utilization in flux-weakening region can be achieved. It shows by using the proposed method a wider the constant torque region owing to the lower voltage margin in the VFRMs, which exhibits higher power output in flux-weakening region. Finally, the method is verified by the test results in the VFRM.