Diode-Clamped Multilevel Converter Voltage Balancing Using Single Modified Quasi-Z-Source Network

Abstract

In this paper, an improved hybrid method using an auxiliary circuit to create voltage balancing of dc link capacitors of Diode-Clamped Converter (DCC) and add voltage boost capability is proposed. Dc-link capacitors voltage deviation is the main problem of DCCs that increases the voltage stress on switches and produces lowest order harmonics at the output. Also, these types of converters inherently reduce the output voltage. In the proposed method, a modified quasi-Z-source (MqZS) network is used as an auxiliary circuit for a five-level three-phase DCC to solve the voltage deviation on capacitors and add voltage boost capability to it. A modulation method is also proposed to control the shoot-through state to boost output voltage of converter. The performance of MqZS network to balancing voltage of dc-link capacitors, output voltage boost capability and efficiency of the modulation method are proved by the simulation results.