Recent developments in power electronics are making the multiphase machines a competitive alternative to conventional three-phase counterparts. Due to their fault-tolerant features, multiphase drives represent a robust technology in high power/high current, safety-critical applications. Besides, their introduction into transportation electrification is gaining on importance. Among the multiphase solutions, the multi-three-phase machines are receiving a lot of the attention by the industry since they use the well-consolidated three-phase technology, thus reducing the design time and also the cost. Therefore, this paper proposes a modular vector control scheme for multi-three-phase permanent magnet synchronous motors. The proposed solution uses a modular modeling approach for the independent and decoupled torque control of each three-phase unit, allowing the implementation of torque-sharing strategies among the three-phase sets of the machine. The developed modular control has been validated on a nine-phase permanent magnet machine.

When multiphase drives are used for specific applications, the modular solutions are preferred as they use consolidated power electronics technologies. The literature reports two modeling approaches for multiphase machines having a modular configuration of the stator winding. The first approach is the vector space decomposition (VSD) that models the energy conversion like an equivalent three-phase machine. The main alternative to the VSD is the multi-stator (MS) modeling that emphasizes machine modularity in terms of torque production. Both approaches have advantages and disadvantages for multiphase machines with a modular structure. Therefore, this paper aims to combine the VSD and MS approaches, defining a new matrix transformation and hence developing a new modeling approach for multiphase machines with a modular structure. The proposed transformation allows a decoupled and independent torque control of the sets composing the machine, preserving the torque regulation's modularity. Together with a new vector control scheme, it has been applied to a modular permanent magnet synchronous machine (PMSM) with a non-standard spatial shift between windings. Experimental results are presented for a nine-phase PMSM prototype with a triple-three-phase stator winding configuration.

A model predictive control scheme for multiphase induction machines, configured as multi three-phase structures, is proposed in this paper. The predictive algorithm uses a Direct Flux Vector Control scheme based on a multi three-phase approach, where each three-phase winding set is independently controlled. In this way, the fault tolerant behavior of the drive system is improved. The proposed solution has been tested with a multi-modular power converter feeding a six-phase asymmetrical induction machine (10kW, 6000 rpm). Complete details about the predictive control scheme and adopted flux observer are included. The experimental validation in both generation and motoring mode is reported, including open-winding post-fault operations. The experimental results demonstrate full drive controllability, including deep flux-weakening operation.

The open-end winding configuration allows feeding an electric motor from two sides. If one of them is connected to an inverter closed on a floating capacitor and operates as a power conditioning system, it is possible to obtain several benefits over the traditional configuration, such as an increase in the constant-power speed range. However, the additional converter causes switching losses that reduce the total efficiency of the drive. In this paper, it is shown how to improve the efficiency of an induction motor drive with open-end windings by controlling the DC-link voltage of the floating bridge depending on the operating conditions. The set-point of the secondary DC link is not calculated as an explicit function of the motor speed, which could depend on many machine parameters, but it is generated by a robust closed-control loop that uses the actual motor state. The variable DC link allows improving the overall efficiency of the drive mainly around the base speed at high values of the torque. Experimental results are shown to confirm the effectiveness of the developed configuration.

The recent advancements of power electronics are encouraging the development of the multiphase drives in both transport electrification and energy production applications. Among the multiphase solutions, the multi-three-phase drives are gaining impressive attention from the industry since they can be configured as multiple three-phase units operating in parallel. In this way, the three-phase technologies can be used, leading to a significant reduction in the costs and design time. Although the multi-three-phase drives possess natural modularity in terms of both machine winding and power converter, few control solutions able to implement a modular regulation of the torque are available in the literature. Therefore, this paper proposes a control scheme implementing an independent regulation of the stator flux amplitude and torque contribution belonging to each winding set of a multi-three-phase induction machine. The proposed control solution can manage the voltage and current constraints introduced by each inverter unit. Besides, torque-sharing strategies among the three-phase sets of the machine can be implemented. Experimental results are provided for a modular power converter feeding a twelve-phase induction machine with a quadruple-three-phase configuration, thus demonstrating the effectiveness of the proposed solution.