A multimode carrier-based PWM strategy for open-end winding permanent-magnet synchronous motor (OW-PMSM) with isolated dc sources is proposed in this article. For the proposed strategy, the independent reference voltages of both the two inverters are obtained by decomposing the reference voltage output from the controller. Then, multiple modulation modes are established by different combinations of continuous PWM, discontinuous PWM and duty-cycle modulation for dual-inverter. As a result, the switching times of dual-inverter in each carrier period can be varied from 6 to 2. For the proposed strategy, the reference voltage is always synthesized by the nearest switching states. Thus, the output waveform quality for dual-inverter of the proposed strategy is better than that of the traditional modulation strategies. The feasibility and effectiveness of the proposed multimode modulation strategy is experimentally validated using a 4.3-kW OW-PMSM prototype.

Numerous voltage vectors exist in a neutral-point-clamped (NPC) three-level inverter. Traditional three-level model predictive control incurs a heavy online computational burden. This paper proposes a model predictive torque control strategy for NPC three-level inverters with permanent magnet synchronous motor systems. First, the relationship among the stator flux linkage vector position, the torque–flux linkage increment, and the stator flux linkage variation is analyzed. Then, the candidate voltage vector sector is determined, and the candidate voltage vectors are selected from it. Meanwhile, the direction of the load current flowing to the neutral point and the voltage difference between the upper and lower capacitors are evaluated. As a result, redundant small vectors are effectively selected, reducing the number of candidate voltage vectors to six and avoiding the computation of all possible vectors. The experimental results from an NPC three-level inverter–permanent magnet synchronous motor system verify that this strategy significantly reduces the computational complexity and provides excellent dynamic and steady-state performance.

Neutral point voltage ripple is the main technical drawback of the three-level neutral-point-clamped (3L-NPC) inverters. Conventional hybrid PWM strategies, which combine zero sequence voltage injection PWM (ZVI-PWM) with double modulation wave PWM (DMW-PWM), can be used to suppress neutral point voltage ripple for all operation conditions. However, the switching frequency of the inverter will be significantly increased in the condition of high modulation index and low power factor. To solve the above issue, a hybrid carrier-based PWM strategy with optimal extension mode is proposed in this paper. Different from conventional hybrid PWM strategies, ZVI-PWM is extended to the neutral point voltage uncontrollable intervals. The optimal extension mode and the optimal width ratio of the extended intervals are obtained to minimize the amplitude of the neutral point voltage ripple. The coordinated control of the switching frequency and the neutral point voltage ripple is realized. The feasibility and effectiveness of the proposed modulation strategy are validated by experimental results

The open-winding dual inverter topology has the advantages of a multilevel output, high DC voltage utilization, large modulation freedom, and easy fault tolerance, and is widely used in photovoltaic grid-connected systems. The open-winding photovoltaic–energy-storage converter system studied in this paper adopts this topology. The system consists of photovoltaic and energy-storage units, and the two converters can independently deliver active power to the grid when the DC-bus voltages on both sides are balanced. To achieve active-power regulation and distribution between the photovoltaic side and the energy-storage side, this paper constructs a mathematical model of the open-winding dual-inverter photovoltaic–energy-storage system and proposes a power-allocation strategy for steady-state operation. Compared with the conventional SPWM, the proposed strategy introduces a reference-voltage allocation layer before the SPWM modules, enabling flexible power sharing while retaining the simple implementation of the conventional SPWM. The proposed strategy effectively guarantees the operational stability and grid-connected power quality of the photovoltaic–energy-storage converter. Finally, its feasibility and effectiveness are verified through simulation analysis and experimental testing.

Open-end-winding dual-inverter converters are attractive for high-voltage and high-power photovoltaic–energy storage systems because of their multilevel output capability and high DC-link voltage utilization. However, unequal power availability between the independent DC links may cause one inverter to exceed its linear modulation range, resulting in overmodulation and grid-current distortion. This paper proposes a power-sharing strategy based on reference-voltage-vector reconstruction for a dual-inverter system with a DC-link voltage ratio of 2:1. The equivalent four-level output characteristics are analyzed, and the feasible power-sharing range is derived according to the modulation index, DC-link voltages, and inverter voltage limits. Combined with 180° decoupled modulation, the proposed strategy enables flexible power transfer among the photovoltaic unit, energy storage system, and grid while keeping both inverters within the linear modulation region. OPAL-RT results demonstrate stable operation under different power-sharing modes, with the grid-side power maintained at approximately 23.2–24.1 kW. These results verify the effectiveness and feasibility of the proposed strategy.