In this paper, the control strategy is studied for the neutral-point-clamped three-level (NPC-3L) dual three-phase permanent-magnet synchronous machine (PMSM) drives at low-switching-frequency operation. The finite-control-set (FCS) model predictive control (MPC) scheme is investigated as the basic MPC scheme, where the average switching frequency is established as the cost function. With the high sampling frequency operation, the discretization with both forward and backward Euler methods is utilized so that the two sets of three-phase windings are controlled separately. To further decrease the switching frequency while maintaining the current and voltage control performance, a collaborative mid-point voltage regulation is proposed. The collaborative regulation strategy fully employs the additional control degree of freedom in the dual three-phase drives by setting the two NPC-3L inverters to select small vectors with opposite polarities. Therefore, the situation is avoided where the upper or the lower capacitor in the DC link provides load currents for the two sets of windings simultaneously. Simulation results of a 2.45 MW dual three-phase drive and experimental results on a laboratory prototype have been presented to verify the validity of the proposed collaborative mid-point voltage regulation strategy.

中文翻译：

---

用于双三相 PMSM 驱动器的三电平 NPC 逆变器的低开关频率 MPC 中的协作中点电压调节


本文研究了中性点钳位三电平（NPC-3L）双三相永磁同步电机（PMSM）驱动器低开关频率运行时的控制策略。研究了有限控制集（FCS）模型预测控制（MPC）方案作为基本MPC方案，其中将平均开关频率建立为成本函数。在高采样频率下，利用前向和后向欧拉法进行离散化，从而分别控制两组三相绕组。为了进一步降低开关频率，同时保持电流和电压控制性能，提出了协作中点电压调节。协同调节策略通过设置两个NPC-3L逆变器选择极性相反的小矢量，充分利用了双三相驱动器中的额外控制自由度。因此，避免了直流环节中的上或下电容器同时为两组绕组提供负载电流的情况。 2.45 MW 双三相驱动器的仿真结果和实验室原型的实验结果验证了所提出的协作中点电压调节策略的有效性。