Ripple Power Steering of HFL-TPC Connected VSI for PV-BESS/EV Applications

Abstract

This paper presents low frequency ripple power steering control strategies for a power conversion topology that comprises of a high frequency linked three port converter (HFL-TPC) and a voltage source inverter (VSI) for PV-BESS/EV applications. The proposed topology has three interfaces which can be connected with a photovoltaic (PV) port, battery energy storage systems (BESS) and/or electric vehicles (EVs) port, and a four-quadrant ac port. The proposed topology inherently exhibits double line frequency (DLF) power fluctuation that needs to be decoupled and steered away from the PV port. In this paper, we have developed and demonstrated two control strategies to deal with the DLF ripple. The first control strategy utilizes loop gain of the closed loop control system to decouple the DLF power, however a residual DLF power still exists at the ac port. To completely decouple the DLF fluctuations, an improved sequence based control strategy is proposed where the DLF voltage components are converted into positive and negative sequence components and controlled separately on their respective synchronous reference frames. To verify the practical feasibility of the proposed low frequency ripple power steering control strategies, a 40 V, 400 W HFL-TPC is built and tested. Experimental results show that the proposed ripple power steering control strategies can decouple the DLF power fluctuation and selectively steer it to the BESS/EV port as DLF power fluctuation is undesirable at the PV port. A comparative results reveal that sequence based control strategy show higher degree of DLF ripple suppression.