Research on Neutral Point Potential Balance of Three-level Inverter Based on Fuzzy Logic Control Strategy

The neutral point potential is an important problem when designing three-level inverter AC driving system. The imbalance of neutral point potential not only increases voltage stresses of power device, but also results in harmonic distortion of output waveform, this paper, firstly, set up neutral point potential model and detail reasons of imbalance are analyzed, then a method based on fuzzy logic controller was proposed, this method is based on the measurement of two capacitor´s voltage, then the error and error change of voltage are as input for the fuzzy logic controller, by change fuzzy rule according to the degree of imbalance, the duration of voltage vector can be caculated. This control method balanced the neutral point potential well. Last, the simulation and experiment results verified the feasibility of the proposed method.