Switching-Table-Based Direct Torque Control of Dual Three-Phase PMSMs with Closed-Loop Current Harmonics Compensation

In this article, the new closed-loop current harmonics compensation strategy is introduced in the switching-table-based direct torque control (ST-DTC) of dual three-phase permanent magnet synchronous machines. The harmonic current distortion is the major problem of ST-DTC of multiphase machines and is typically caused by the lack of control in the auxiliary x–y subspace under the vector space decomposition model. The synthetic vectors to obtain average zero voltage in the x–y subspace can be a solution. However, this cannot compensate for current harmonics; for example, due to dead-time and back-electromotive force distortion, which is also mapped into the x–y subspace. Therefore, in this article, the x–y voltage references are obtained by the closed control loop that controls x–y currents to zero. To modulate the nonzero x–y voltage reference, the new modulation approach employing voltage vector groups in the x–y subspace together with the new switching table is developed and incorporated into ST-DTC. Meanwhile, the analysis of the two available sets of 12 voltage vector groups illustrates a tradeoff between linear range in the x–y subspace and the dc-link voltage utilization rate. Finally, the effectiveness of the proposed ST-DTC strategy is verified through experiments and simulation.