Abstract

In this paper, a new medium-voltage power conversion system consisting of a four-level boost converter and four-level diode-clamped inverter is proposed for permanent magnet synchronous generator-based megawatt-level wind turbines. To achieve a simple and optimal control performance, a simplified two-step model predictive strategy is proposed. The high-power wind turbine requirements, which include maximum energy harvesting, balancing of dc-link capacitor voltages, net dc-bus voltage control, regulation of grid-reactive power, and the minimization of both switching frequency and common-mode voltage are expressed as cost functions. The best switching states are chosen and applied to the power converters during each sampling interval based on the minimization of cost functions. The feasibility of the proposed configuration and control scheme are verified through MATLAB/Simulink tests on a high power (5 MVA/4160 V/694 A) system and dSPACE experiments on a low power (3.6 kVA/208 V/10 A) prototype.