An optimal predictive control method for three-level inverter with low switching losses under target current THD

Abstract

To balance the relationship between current THD and switching loss, an optimal predictive control method using single and double vector hybrid modulation of NPC-3L inverter is proposed. Firstly, the relationship of the THD of output current and the Aoc&rc (the Area enclosed by output current and reference current) is built. Secondly, the current threshold is defined to control the switching time of single/double vectors, which is used to balance the current THD and switching loss and determined by the target current THD value. Thirdly, the output of single vector or double vector is determined by comparing the output real-time current value with the set current threshold. That is, when the output current is greater than the current threshold, a single vector is used to reduce the switching loss. When the output current is less than the current threshold, the THD of the output current is raised by using output double vectors. At the same time, by using this control method, the disadvantages of single/dual vector independent operation are mutually offset. Finally, a simulation model is built to verify the proposed control method. Compared with traditional methods, the simulation results show that the proposed method is correct and effective.