Power factor improvement in WECS using cascade PI control of passive damping LCL-filter

This work proposes an algorithm for the elimination of switching ripples caused by the commutation of power semiconductors used in STATCOM. LCL-filter is a favorite solution to achieve this goal; however it reduces the stability of the system with the presence of resonance phenomena. Passive damping resistor can be inserted in series with capacity of LCL-filter to solve this problem. The LCL-filter is divided into three parts in order to reduce the interaction between filter components and the complexity of the control algorithm. Moreover, in order to improve the dynamic of the system, a cascade PI control is proposed. Different design steps are presented with damping resonance phenomena using a resistor connected in series with the capacitance. Our investigations show that the Total Harmonic Distortion (THD) of voltage and current injected into the grid tends to zero. That means, the passive damping LCL-filter attenuates the major part of current ripples compared with results obtained by using L-filter.