Direct Torque Control of DC-Biased Hybrid Excitation Machine with Adjustable Zero-Sequence Current

This article presents a direct torque control strategy for a DC-Biased hybrid excitation machine with zero-sequence current. The drive topology is first introduced and analyzed, and then the machine is mathematically modeled. Based on the characteristics of the model which has an additional current to adjust, a control strategy is raised. The strategy adjusts the duty cycle by varying the switching time, reserving the regulation time of the dc biased current for every switching cycle. Also, since conventional direct torque control suffers from unstable switching frequency and large torque and flux ripples, Space vector pulse width modulation method is introduced. In general, simulation results are consistent with the theoretical results, it indicates that by using the control strategy the machine can achieve accurate operating conditions and rapid dynamic torque response.