Abstract：The traditional modular multilevel converter (MMC) has drawbacks such as many submodules, large volume and weight, and high cost. The lightweight MMC topologies have become a research hotspot. Half-Wave Shaping MMC (HWS-MMC) is a new lightweight hybrid multilevel converter that integrates the merits of the two-level topology and the MMC topology. The HWS-MMC can reduce the module numbers and voltage stress since the multilevel arm only needs to modulate part of the sinusoidal waveform. In existing studies, phase-shift modulation and third-order harmonic injection methods for energy balance issues of the wide-range operation of HWS-MMC are based on the inverter operation with supply ideal DC voltages supply, and no detailed multi-objective control design has been conducted. Therefore, this paper studies the dynamic model and multi-objective control strategy of HWS-MMC. Firstly, the topology and working principle of HWS-MMC are introduced, and the energy balance mechanism and phase-shift wide-range modulation method are clarified by deriving the arm energy accumulation expression. The mathematical models of internal and external variables are established for HWS-MMC, including grid current dynamics, submodule capacitor voltages, and DC bus capacitor voltage. Then, a fully averaged dynamic model without switching characteristics is obtained and linearized using the multi-scale switching period averaging technique. An overall control strategy is systematically established with the objectives of grid current control, two-stage DC voltage control, and energy balancing control between phases and within an arm. The design method of the multi-loop controllers and commutation control logic are also given. An HWS-MMC system is built on the RT-Lab platform. Experiments are conducted under the grid voltage disturbance, load disturbance, and reactive power regulations. The waveforms, including the AC voltage and current, the DC bus and submodule capacitor voltages, the modulation coefficient and phase-shift angle, and the active and reactive power, are given. The results show that the modulation coefficient and phase-shift angle are adjusted accordingly through the multi-loop control, ensuring the stability of the DC bus voltage and the submodule capacitor voltages. In addition, voltage balancing between and within phases is achieved. The half-sinusoidal multilevel waveform and six-pulsation DC bus current are consistent with the theoretical analysis. The following conclusions can be drawn. (1) The AC side characteristics of HWS-MMC are similar to traditional VSC, the characteristics of the internal module capacitors are similar to MMC, and the DC bus characteristics are similar to the six-pulsation rectifier. (2) The dynamics of the DC bus capacitor voltage and submodule capacitor voltage are independent. (3) The multi-control objectives are achieved with additional phase-shifting control and the submodule modulating wave correction.
孙玉巍, 陶聪, 付超, 张泽霖, 王琛, 王毅. 半波整形模块化多电平换流器动态建模及多目标控制策略[J]. 电工技术学报, 2025, 40(6): 1864-1877.
Sun Yuwei, Tao Cong, Fu Chao, Zhang Zelin, Wang Chen, Wang Yi. Dynamic Model and Multi-Objective Control Strategy of Half-Wave Shaping Based Modular Multilevel Converter. Transactions of China Electrotechnical Society, 2025, 40(6): 1864-1877.
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