Control of five-level voltage source converters used with a type-4 wind turbine.

Abstract

Wind Energy Conversion Systems (WECSs) have attracted considerable attention and emerged as a highly promising and advancing renewable energy option. A typical WECS setup involves a Permanent Magnet Synchronous Generator (PMSG) connected to the power grid via power electronics converters. Nevertheless, the commonly used two-level Voltage Source Converter (2L VSC) configurations suffer from drawbacks such as increased switching losses, significant harmonic distortion at the output, and the need for additional Electromagnetic Interference (EMI) filters. Overcoming these challenges can be achieved through the adoption of multi-level converter topologies, which offer several advantages over conventional ones. These benefits include reduced switching losses, improved overall efficiency, and a decreased number of filtering elements required. By employing multi-level converters, the limitations of traditional 2L VSC topologies can be mitigated, making them a more efficient and suitable replacement. The main objective of this research was to optimize the control of the proposed WECS by utilizing the Five Level Neutral Point Clamped (5L NPC) Voltage Source Converter (VSC) topology. The ultimate goal was to enhance the stability and power quality of the WECS when integrated into the grid system. The research findings are based on simulations carried out using the Power Systems Computer-Aided Design (PSCAD) software, which incorporates built-in power electronics device models. The study focused on controlling both sides of the converter, namely the Machine Side Converter (MSC) controller and the Grid Side Converter (GSC) controller, with the aim of improving the overall system performance. To achieve this, the control scheme employs the Vector-Oriented Control (VOC) strategy, along with phase lead and lag compensators, to effectively regulate the power flow delivered to the grid and achieve a unity power factor. Ultimately, the simulation results convincingly demonstrated the enhanced efficiency of the overall system performance. Specifically, the study analyzed and compared Total Harmonic Distortion (THD) with a conventional converter topology under varying wind speeds. The THD values for the simulated voltage and current using the 2L VSC were found to be: 56.48% at 8m/s, 58.03% at 16m/s, and 2.35% at 8m/s, 8.95% at 16m/s, respectively. Nevertheless, by substituting the 2L NPC with the suggested 5L NPC topology, substantial improvements were achieved. The THD voltage saw a significant reduction of 26.63% at 8m/s, 30.5% at 16m/s while the current experienced a slight drop of 0.2% at 8m/s, 6.52% at 16m/s respectively.