Performance enhancement of Modular multilevel converter with Various control techniques Including bio inspired optimization Algorithms

Abstract

The Modular Multilevel Converter (MMC) is an emerging newlineprominent voltage source converter topology that is rapidly gaining popularity newlinein high voltage/power applications such as high voltage DC transmission newlinesystems. The MMC applications can be extended to medium voltage/power newlineapplications, since it has several advantages over other classical multilevel newlineconverter topologies, including modularity and scalability to meet the voltage newlinelevel requirements, the absence of isolated DC sources, high efficiency, and newlinesuperior harmonic performance. The primary issues of MMC are balancing newlinethe capacitor voltage and regulating the circulating current. In the MMC, the newlinetotal energy of the DC-link is not stored in a single large capacitor as in the newlinecase of conventional voltage source converters, whereas it is equally newlinedistributed among all submodule capacitors. This happens because the newlinefloating capacitors in the submodules act as an interface between the DC newlineinput voltage and the AC output voltage in MMC. Hence, the capacitor newlinevoltages should be balanced. The circulating current originates due to newlinedifferences in the submodule capacitor voltages in the phase leg. This newlinecirculating current flow increases the capacitor voltage ripples and the output newlineRMS current. The circulating current and the capacitor voltage ripples are the newlineessential factors affecting the performance of MMC. Subsequently, newlinecontrolling the circulating current and balancing the submodule capacitor newlinevoltage on MMC are essential. newlineThe first phase of research involves performance analysis of MMC newlinewith level-shift carrier-based PWM and implement the capacitor voltage newlinebalancing algorithm for producing quality output voltage. The classifications newlineof level-shift PWM based on the carrier s position are phase disposition, newlinephase opposition disposition and alternate phase opposition disposition newline