The Voltage Balance Control Strategy of Static Var Generators DC-Side Capacitors Based on Fuzzy-PI Adaptive Cascaded H-bridge

A voltage balance control strategy based on the fuzzy adaptive PI (Proportional Integral control) is proposed to address the problem of unbalanced capacitor voltage on the DC side of cascaded H-bridge static var generators (SVG). In the control strategy, fuzzy control is introduced based on PI control. A duty ratio correction is added to all levels’ public active power duty ratios, thereby realizing the balance of DC-side voltages at all levels. A test was conducted by building a single-phase three-H-bridge unit cascaded SVG simulation platform. The results show that the DC-side voltage balance can be controlled by the voltage balance control strategy at all levels effectively. It has the advantages of a simple control structure, double closed-loop control with decoupling of the system’s current DQ, no coupling effect, a fast response speed, and high precision. The voltage balance control strategy can exert a good control effect when the system experiences a sudden voltage imbalance.