Development of an Analytical Methodology for the Loss calculation of the Modular Multilevel Cascaded Inverter with Third Harmonic Injected (THI) PWM

Abstract

Three main foundations such as hydro, wind and solar belong to renewable resources, nevertheless, solar energy is considered as the most reliable and continuous source of energy consumed by photovoltaic array. For the profusion, omnipresent and easy existence of solar energy, it becomes the strong competitor against fossil fuel. To generate continuous electric power using renewable energy resources, Multilevel power converters has been receiving attention in the past few years by gaining synthesized waveforms with lower THD for Medium or high power high voltage applications. Multilevel power converters are various types. Among them Modular Multilevel Cascaded (MMC) converter is being widely used in order to achieve more efficiency than obtained from the Conventional converter system.The losses that exist in the Multilevel converter are much more complicated to evaluate compared to the Conventional converters. Loss evaluation in this type of converter needs special attention because current always varies in different switches of the converter depending on PWM techniques, also a few percentage of loss in MW system represents kW range power loss which has a large effect in the system. Moreover, the losses are represented as switch loss and conduction loss in the Multilevel converters/Inverters. The overall losses depend on three different parameters, such as modulation technique, Inverter level and inherent manners of respective IGBTs. In this thesis work, Third harmonic injected (THI) Pulse width modulation with level shifted scheme is used as switching technique and Insulated Gate Bipolar Transistors (IGBTs) are used as switching devices in the converter/Inverter. The Proposed research is aimed for developing an Analytical Methodology for the loss calculation of the Modular Multilevel Cascaded (MMC) Inverter. In this book the above concept is presented through modeling and simulating the 15 level Modular Multilevel Cascaded (MMC) converter/Inverter by MATLAB. After simulation, it is found that, when comparing with the Reference paper with Proposed Loss Calculation Method using SPWM modulation technique, the switching losses come higher which is about 79% than conduction loss which is 21% . On the other hand, using Third Harmonic Injected (THI) PWM, switching loss is lower than conduction loss. All the results have been evaluated and compared for the MMC converter/Inverter.