An unbalanced regulation method based on the Optimized Modulation Strategy of Three-level Four-arm Inverter

At present, three-phase unbalanced problem exists in the low-voltage distribution network, which seriously affects the quality of power supply. To solve this problem, the research separates the unbalanced component from three-phase unbalanced current on load side, and uses the 3-Dimensional Space Vector Pulse Width Modulation (3D-SVPWM) Strategy of Three-level Four-arm Neutral-point-clamped Inverter to track and control it. To simplify the calculation process, the research proposes a 3D-SVPWM Optimized Modulation Strategy by allocating the modulation area reasonably based on the Decomposition Idea. Firstly, the spatial distribution of voltage vector of Three-level Four-arm Inverter is decomposed in an abc coordinate system which is reasonably divided into several two-level structures for further analysis. And then, the reference voltage vector is modulated by the Two-level Modulation Strategy. The result of Matlab/Simulink experiment has verified the correctness of the proposed strategy.