Integrating a Single Z-Source Network with a Modular Multilevel Converter for Voltage Boosting

Abstract

This paper proposes the integration of a Z-source network with the modular multilevel converter (MMC) to add voltage boosting capability to a voltage step down converter. To limit the increase in complexity, the proposed Z-source modular multilevel converter uses a single Z-source network that is interconnected between the corresponding terminals of the DC- input source and the DC-link terminals of the MMC. The authors previously presented a modulation technique for quasi Z-source MMC (qZS-MMC) referred to as the reduced inserted cells (RICs) PWM but a large size inductor for the two quasi Z- source networks were needed. This paper shows that utilising the RICs scheme with the-source MMC is more advantageous compared with the qZS-MMC. The operation principle of the Z- source MMC using RICs scheme and the derivation of key design parameters is presented in this paper by analysing the relevant current and voltage waveforms. The simulation results verify the operation and showcase the excellent waveform performance of the proposed topology.