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.

Unlike VSIs, the single-stage inverters (SSIs) from the family of Z-converters are capable of boosting input dc to a desired ac voltage. The Z-network of these converters consists of a symmetric X-shaped network or a combination of inductors and capacitors. The basic Z-source converter (ZSC), connected in X-shaped fashion is modeled as a fourth-order system. This can be further modeled as a second-order system to reduce the sensor count but this may lead to an unstable system if there is an asymmetry in network parameters. Also, the source current of SSIs contains second-order ripple current (SRC) component, which oscillates at twice the supply frequency and has detrimental effects on sources. To alleviate the above problems, a parametric uncertainty compensation and ripple mitigation (PUCRM) control methodology is proposed. PUCRM control can be used to maintain stability and achieve desired performance during parametric uncertainties in the dc–dc stage and to reduce SRC propagating to the sources while feeding ac loads. PUCRM consists of a nominal dual-loop PI controller, which regulates the SSIs to achieve desired performance and a nonlinear integral sliding mode component that mitigates the uncertainties and ripple component. The proposed method is verified using simulation and experimentation.