An improved current-limiting strategy for shunt active power filter (SAPF) using particle swarm optimization (PSO)

The current-limiting strategy for shunt active power filter (SAPF) will be activated automatically, when the compensation-capacity need exceeds the rated capacity. However, the traditional current-limiting strategy cannot realize the comprehensive protection with optimum objectives. The paper firstly reveals the essential of the current-limiting demands for the comprehensive protection of SAPF, namely the limiting control objects: 1) the root mean square (RMS) of the compensation current (mainly for the overheat protection of the IGBT and inductor); 2) the instantaneous wave of compensation current (mainly for the accurate current control and IGBT Icnom specification) and 3) the instantaneous wave of PWM-VSC modulation voltage (for the need of liner close-loop control). Secondly, the paper proposes an improved current-limiting scheme based on particle swarm optimization (PSO) to achieve the two optimization targets: 1) the minimization THD for the grid-side current; 2) the maximization utilization ratio for the capacity of the SAPF. The main advantage lies on the optimum limiting ratios of each harmonic order are calculated in real time respectively to achieve the flexible and liner limiting control. Finally, simulation and experiment verify the effectiveness of the proposed strategy.