Robust Integral Sliding Mode Control for Transient Voltage Support From Bidirectional Converter-Based Active Filters in Microgrids

The dc–ac conversion in microgrids leads to second-order oscillations in the dc side voltages and source currents. These oscillations are mitigated using either active or passive filters. Active filters are preferred, as they mitigate oscillations with lesser component size than passive filters. The active filters are regulated to absorb the harmonic ripples at the ripple frequency, and do not provide any voltage support during dc bus voltage fluctuations due to load changes. In this article, a robust integral sliding mode control (RISMC) is proposed to regulate bidirectional converter (BDC)-based dc active filters to facilitate voltage conditioning along with reduction of second-order harmonics which are caused due to dc–ac conversions. The proposed RISMC enhances capability of the BDC active filters to provide dc bus voltage conditioning in case of transience during load variations and uncertain voltage fluctuations. The proposed control consists of a nominal dual-loop PI control which regulates the voltage of the storage capacitor of BDC and a nonlinear integral sliding mode control which regulates dc bus voltage. The proposed control mitigates voltage and current ripples hence preventing them to propagate toward the sources while providing additional voltage support functionality. The proposed control is verified through simulations and experimentation.