Sequential Predictive Control with Dynamic Priority of Three-Level NPC Back-To-Back Power Converters in PMSG Wind Turbine Systems

Three-level neutral-point-clamped back-To-back power converter based direct-drive permanent magnet synchronous generator wind turbine is an attractive configuration of offshore wind power system. Due to the high performance of model predictive control (MPC), it is a promising control solution for such a system. However, conventional MPC includes multiple control targets within a single cost function, leading to complex design of weighting factors and high inter-coupling of targets. To solve this problem, this work proposes a dynamic cascade MPC solution, in which the multiple targets are realized without weighting factors. The realization priority is variable according to the error of the control targets. Besides, the number of the candidate voltage vectors for the next stage is adjusted, based on the control threshold of the targets. Hence, this solution achieves overall optimal control of multiple targets under different operation conditions. The simulation results confirm the effectiveness of the proposed solution.