"TEC-A Novel Dual Feedback Collaborative Flux-Weakening Control for Multiphase Non-Sinusoidal Permanent Magnet Synchronous Motor"

"A flux-weakening control strategy for a seven-phase non-sinusoidal permanent magnet (PM) machine is proposed. Here, the magnitudes of the first (E1) and third (E3) harmonic back electromotive force are comparable, increasing the machine additional control degrees of freedom. The third harmonic current plays a double role in flux-weakening (FW) operational region: it not only produces the electromagnetic torque but also weakens the peak value of stator voltage, thereby achieving wider speed range. However, the existence of the third harmonic component can bring time-consuming computation process for confirming the voltage boundary. Thus, a real-time voltage calculation method is proposed and presented. Subsequently, based on the conventional 3-phase negative d-axis current FW method and the analysis of the extended dual d-axis currents injection FW strategy with fixed ratio in multiphase PMSM, a novel dual feedback collaborative FW control strategy is proposed, which allows considering simultaneously the phase difference of the voltage components and the distribution ratio of d-axis currents (id1 & id3). Not only the stability of drive system can be improved, but also the efficiency of the system can be increased through the proposed method. Moreover, it can also be well adapted to other non-sinusoidal multiphase PMSMs. Ultimately, simulation and experimental results with a 7-phase non-sinusoidal PM machine validate the effectiveness of the proposed strategy."