Direct Torque Control Strategy of DC-Biased Hybrid Excitation Vernier Machine With Adjustable Zero-Sequence Current

This paper proposes a direct torque control strategy for a DC-Biased hybrid excitation vernier machine with adjustable zero-sequence current. The machine structure and drive system are first introduced, and the machine model is built under the stator flux linkage field orientation. Then, the mathematical equations are derived, and the regulation principle of torque and stator flux linkage is clarified. According to model's characteristics, the maximum torque per ampere operation principle for the machine is analyzed. Afterward, a direct torque control strategy based on stator flux linkage adaptive regulation is proposed, where the stator flux linkage can be adaptively regulated under the zero-sequence current reasonable distribution so as to realize maximum torque per ampere operation. In addition, a combined flux linkage observer is designed for accurate estimation of stator flux linkage. Furthermore, since conventional direct torque control strategy has issues with torque and flux ripples, the space vector modulation is utilized. Overall, the experimental results verify the effectiveness of the proposed control strategy.