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This study proposes a novel robust predictive current control that is based on a discrete-time disturbance observer for an interior permanent magnet synchronous motor (IPMSM), does not require rotor flux information. To confirm the effects of the current control response on a parameter mismatch, the parameter sensitivity for the current prediction of a conventional deadbeat predictive current control (DPCC) is analysed. With the proposed method, disturbances owing to a parameter mismatch, rotor flux term, and unmodelled dynamics are estimated using a Luenberger observer in the discrete-time domain. The estimated disturbances are compensated with the predicted reference voltage model considering a digital delay. The stability of the proposed disturbance observer owing to a parameter mismatch of the stator resistance and d-q inductance is also analysed. The proposed method is robust against the stator resistance and an inductance variation, and an accurate predicted current control can be obtained without an offline or online estimation of the rotor flux. Compared with the conventional DPCC, the proposed method can eliminate a steady-state current and transient state error caused by disturbances of the system. Experimental results are presented to verify the proposed control scheme even with mismatched parameters of the IPMSM.

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In this study, a circulating current suppression strategy is proposed using high-frequency voltage compensation when asynchronous carriers exist between modules in modular and scalable inverter systems (MSISs). In MSIS, an inverter and a control unit constitute one module. Because each module is connected in parallel, the power capacity and efficiency can be increased. However, according to the switching state in the parallel module, a circulating current can be generated. This current causes stress on the switches. Furthermore, the circulating current not only deteriorates the current control performance but also increases the difficulty of load sharing. In this study, a novel method is proposed to suppress high-frequency circulating current caused by asynchronous carriers. This current can be reduced by generating the same switching pattern in two modules using high-frequency voltage compensation. Simulation and experimental results are presented to verify the proposed method.