Development of high efficiency power electronics converter for medium voltage drive

• Main Author: Sapkota Rajesh
• Other Authors: Wang Peng
• Format: Theses and Dissertations
• Language: English
• Published: 2016
• Subjects: DRNTU::Engineering::Electrical and electronic engineering
• Online Access: https://hdl.handle.net/10356/65913
• Institution: Nanyang Technological University

Use of Medium Voltage (MV) converters for high power motor drives application has gained a huge attention at present. Excellent speed control of the motor and the reduction of the energy loss in the system are the main attraction of these drives. These MV converters are widely used in industries for driving pumps, fans and propulsion system on ships. The advent of the higher voltage and high power application has made the study of multilevel converters for medium voltage drives application much more attractive. Multilevel Converters have far less harmonics than the 2 level converters for a given switching frequency and has very less distortions in the input current. In addition to this, the use of IGBTs in Multilevel converters helps in reducing the system loss thereby increasing the efficiency. Also the use of IGBT helps in increase system power density. In this study MV converters from 3.3kV to 6.6kV have been considered. These converters would be feeding a 1MW squirrel cage induction motor. The performance comparison has been done by computing and comparing the losses of different topologies with different current and voltage ratings of the IGBTs. In addition to the evaluation of losses, the impact on the power quality has also been analyzed for the multilevel converters and compared with the standard limits. The purpose of this thesis is to compute the thermal losses of different topologies of MV multilevel converters and compare their efficiencies and to select the most efficient topologies for MV application. For this study, advanced topologies for MV drive application viz. Neutral Point Clamping and Cascaded H-Bridge Multilevel Converters topologies were reviewed and power loss model of each topology was established for different voltage levels. The converters are then simulated at different switching frequencies and are compared on the basis of the power losses and power quality. The model of these topologies was built in Piece-wise Linear Electrical Circuit Simulation (PLECS) 3.6.3 software. Keywords: Voltage Source Converters, Multilevel Converter, Thermal Losses, Efficiency.