Active Power Decoupling of Single-Phase Photovoltaic Inverter Using DC Active Filter and Improved Hybrid Controller

Single-phase power consists of two constant (DC) and fluctuating components in which fluctuating component will make the double frequency voltage ripple at DC side. This ripple causes several problems such as reduced efficiency, panel lifetime and increase of harmonic component at AC side. Different methods were proposed but these methods face different problems like dependency to the main converter, increased number of passive elements and unproper control system. The proposed structure acts as a DC parallel active filter. This structure acts as an independent current source controlled by voltage and its main task is to remove PV current ripple. Resonance-proportional controllers have the ability to minimize the steady state error at the resonance frequency but, on the other hand, this controller does not have the ability to provide a fast and appropriate dynamic response. Dead Beat (DB) control method is a model-based digital control method with a fully digital nature that is capable of providing very fast dynamic response by placing the system poles at the center of the unit circle. The DB control method with a very simple structure is proposed to be used in parallel with the proportional-resonance controller as a hybrid control method. The combination of these two methods, while providing a very simple structure, has the ability to meet the control specifications appropriate to the proposed compensator. Several simulations show the effectiveness of the proposed structure and control method in which the current ripple is reduced from 10A to 0.5A.