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A Novel Single-Phase Seven-Level Inverter with Its Modulation Strategy

In this paper, a novel single-phase seven-level inverter topology is not only proposed but also illustrates the modulation strategy of it. The topology consists of two parts, full-bridge circuit and switched-capacitor circuit which using unipolar pulse-width modulation (PWM) strategy. The strategy allows the full-bridge circuit to operate in seven voltage-level modes, meanwhile, the operation principle and switching actions of the topology are also explicitly analyzed in the text. By controlling the modulation amplitude range, it is possible to implement the 7, 5 and 3 inverter operating modes. The inverters mentioned in this paper can balance the capacitor voltage without auxiliary circuits or complicated control strategies. Finally, a simplified inverter control algorithm is proposed, which realizes proportional resonance (PR). The simulation results show that the proposed inverter can output currents of low THD, which is superior to traditional full-bridge inverter.