Abstract：Currently, the main topologies for high-voltage, high-capacity AC-AC converters, such as the back-to-back modular multilevel converter (BTB-MMC) and the modular multilevel matrix converter (M3C), still face challenges, including a large number of submodules, high capacitor requirements, low power density, and complex decoupling control. This paper proposes an isolated half-wave shaping-based multilevel AC-AC converter (IHWS-MAC) that leverages half-wave shaping and half-wave frequency conversion. The proposed topology employs half-wave commutation units and dual active half-bridges to improve power density. By introducing half-wave commutation units, the topology converts the multilevel half-waves into sinusoidal full-wave outputs, significantly reducing the number of submodules required in multilevel units. The nested integration of dual active half-bridge (DAHB) high-frequency isolation units with the multilevel submodules enables the isolation units to store and release energy from the submodule capacitors on both sides through power regulation, thereby ensuring energy balance within the multilevel units. Moreover, this nested configuration helps reduce the number of capacitors and power devices. Then, a multi-objective overall control strategy is proposed for the IHWS-MAC, encompassing its input, isolation, and output stages. The strategy achieves coordinated control of power, voltage, and current on both the low-frequency and line-frequency sides, ensuring voltage stabilization and balance of the internal submodule capacitors. An IHWS-MAC system was built on the RT-Lab platform. Experiments were conducted under conditions of power disturbances and low-frequency side-grid voltage dips. The waveforms, including submodule capacitor voltages, grid-side AC voltages and currents, active and reactive power, and multilevel sinusoidal half-wave and full-wave voltages on both sides, were recorded. The results show that, under power or voltage disturbances, the IHWS-MAC maintains stable capacitor voltages while achieving inter-phase and intra-phase voltage balancing. The changes in AC currents on both sides are consistent with the power regulation processes at the input and output stages. Moreover, under the control of the commutation switches, the multilevel sinusoidal half-waves generated by the multilevel units on both sides at their respective system frequencies are synthesized into complete sinusoidal waveforms at the AC ports. The following conclusions can be drawn: the IHWS-MAC topology reduces the number of submodules, capacitors, and power devices, thereby improving power density. It also eliminates circulating currents and addresses issues with arm-capacitor energy balancing. Furthermore, featuring two DC links, it naturally decouples the AC-DC power conversion on both sides, while the integrated DAHB provides additional control degrees of freedom for flexible voltage and power regulation. In summary, the IHWS-MAC offers advantages in power density and control flexibility, providing a new solution for multilevel AC-AC conversion systems.
孙玉巍, 常泽宇, 付超, 陈琪, 辛耀光. 隔离型半波整形多电平AC-AC换流器拓扑及控制策略[J]. 电工技术学报, 2026, 41(18): 6214-6226.
Sun Yuwei, Chang Zeyu, Fu Chao, Chen Qi, Xin Yaoguang. Topology and Control Strategy of Isolated Half-Wave Shaping Based Multilevel AC-AC Converter. Transactions of China Electrotechnical Society, 2026, 41(18): 6214-6226.
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2026, Vol. 41 
