Novel Cascaded Switched-diode Multilevel Inverter for Renewable Energy Integration

Abstract

In this paper, a new topology of two-stage cascaded switched-diode (CSD) multilevel inverter is proposed for medium voltage renewable energy integration. Firstly, it aims to reduce the number of switches along with its gate drivers. Thus, the installation space and cost of a multilevel inverter are reduced. The spike removal switch added in the first stage of the inverter provides a flowing path for the reverse load current, and as a result, high voltage spikes occurring at the base of the stepped output voltage based upon conventional cascaded switched-diode multilevel inverter topologies are removed. Moreover, to resolve the problems related to DC source fluctuations of multilevel inverter used for renewable energy integration, the clock phase shifting (CPS) one-cycle control (OCC) is developed to control the two-stage CSD multilevel inverter. By shifting the clock pulse phase of every cascaded unit, the staircase-like output voltage waveforms are obtained and a strong suppression ability against fluctuations in DC sources is achieved.

Existing System

Generalized Current Flow Model.

Proposed System

A new topology of two-stage CSD multilevel inverter has been proposed in this paper. n cascaded basic units and one spike removal switch form the first stage. Then by adding a full-bridge inverter as the second-stage converter, both of the positive and negative output voltage levels are generated. Since the one full-bridge converter in the output side leads to the restriction on high-voltage applications, the proposed topology is suitable for medium-voltage renewable energy integration. The comparisons with the CHB and cascaded half bridge topologies show that the CSD topology requires less switches and related gate drivers for realizing the output voltage. As a result, the installation space and cost of the multilevel inverter are reduced. Meanwhile, the spike removal switch added in the first stage provides a flowing path for the reverse load current under R-L loads, thus, the high voltage spikes, due to the collapsing magnetic field in a very short time interval, are removed.

Architecture

The structure of the proposed two-stage CSD topology