Virtual Impedance based Second Order Ripple Control For Non-Inverting Buck-boost Converter

The second order ripples are reflected at the input terminals of the inverters during dc-ac conversion. This leads to oscillations in current and voltages at twice the ac supply frequency. The oscillations are more dominant in dc to single phase ac conversions. The second order ripple current propagates to the source and leads to failure of heating issues. A dual loop control with inverted notch inductor current feedback based impedance control methodology is proposed to increase the impedance in series with the inductor, virtually. This leads to significant reduction in ripple currents propagating through the buck-boost converter to the source. This however leads to the degradation of dynamics. An integral sliding mode control is proposed to improve the dynamic performance and also mitigate uncertainties. As a result the objective of achieving variable ac voltage without ripple propagation to the source, without adding any extra component is fulfilled. The proposed control is verified through simulations and experiments on a buck-boost feeding a single phase ac load.