Dual Reference Frame Based Current Harmonic Minimization for Dual Three-Phase PMSM Considering Inverter Voltage Limit

This article proposes an optimized current harmonic minimization (CHM) approach for dual three-phase permanent magnet synchronous machines (PMSMs) with consideration of inverter voltage limit. The current harmonic model is derived to analyze the dominant current harmonic components in dual three-phase PMSM drives. Dual reference frame (DRF) model is proposed to convert the current harmonics into dc components in the new DRFs, and PI controllers are employed to control voltages to minimize the dc components. This article will prove that current harmonics can be minimized by using the DRF model. Since CHM requires additional voltages, inverter voltage limit must be considered especially at high speeds. Hence, inverter voltage limit is considered to derive the theoretical control strategy, in which minimal copper loss is selected as the design objective to reduce current harmonic with limited voltage. The proposed approach is supported by theoretical analysis and proof, and it does not require inverter voltage and machine parameters. Moreover, the proposed approach is compared with an existing method to show the performance improvement and evaluated with extensive tests on a laboratory prototype under both steady-state and transient conditions.