System Level Optimization of 5 MW Wind Converter using 3L-NPC Topology in Medium Voltage with 1 . 7 kV IGBT

Abstract

Market competitiveness is the main driver in the massive adoption of wind energy, and the optimization of the power converter is crucial for this purpose. Because it has higher efficiency than the two level Voltage Source Converter (2L-VSC), the three level Neutral Point Clamped (3L-NPC) topology is considered for the converter optimization. Due to reduced voltage stress in 3L-NPC, the system voltage can be increased up to Medium Voltage while keeping the same 1.7 kV semiconductors used for 2L-VSC. Potential extra efficiency due to the increased voltage, cooling system and filter volume reduction are studied by simulation. Commercial cooling systems and capacitors are analyzed to calculate volumes, while analytical expressions are used for the inductors. A system level optimization is proposed achieving filter and combined volume reduction, as well as efficiency increment. The benefits of using three level converters to increase the application voltage, without increasing the semiconductors voltage range are shown at system level.