Back-to-back five-level converters for wind energy conversion system with DC-bus imbalance minimization

This paper presents a new method of regulating the DC voltage of a back-to-back NPC five-level converter applied in a wind energy conversion system based on doubly fed induction generator. The proposed control algorithms consist of two loops: the outer closed loop controls the average value of the DC voltage, whereas the inner loop controls the difference between the two voltages in each half-arm using a clamping bridge circuit. To verify the validity of the method and to prove the performance of the proposed control algorithms, simulation was carried out in a MATLAB Simulink environment. The results obtained show the effectiveness of the proposed algorithms.