This paper proposes a novel seven-level power topology, that increases the number of output levels by using fewer power switches and capacitors compared to the traditional seven-level topology. Moreover, the working mechanism of the proposed topology and its implementation method are given. Furthermore, a two-stage capacitor-voltage equalization control strategy with overall control and independent control is proposed. Finally, the proposed topology is applied to the active power filter system, and simulations and experimental research of two types of working conditions are performed. The results verify the effectiveness and feasibility of the new topology and control strategy.Energies 2019, 12, 2997 2 of 16 and carrier rotation is proposed to realize multilevel output, and the power balancing distribution of each element is also realized. However, the power-balance control strategy is not given. In addition, methods based on step-wave modulation technology, multi-frequency power allocation, etc. have been proposed, but there are some limitations in terms of harmonic performance, implementation difficulty, and power balance distribution, etc. [29,30].This paper proposes a novel seven-level power topology. Compared to other traditional seven-level topologies, it can reduce the number of power switches and capacitors, increase the number of output levels, and reduce the harmonic content of the output voltage and the complexity of the system. This paper deeply analyzes the working mechanism of the novel power topology and gives the engineering realization of the proposed topology. At the same time, an equalization control strategy with overall control and independent control of two-stage capacitor voltage is proposed to solve the problem of the capacitor-voltage imbalance in applications. Finally, the novel topology is applied to the three-phase APF system, and the harmonic suppression control strategy and cell capacitor-voltage regulation are proposed. The simulation and experimental work are carried out under different working modes, and the results verify the correctness and feasibility of the proposed novel topology and control strategy.
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