A Novel Topology for DC Electric Spring With Parallel Structure

Abstract

Direct current electric spring (DCES), as a new solution for the power quality issue caused by the unstable output of photovoltaic (PV) and wind power integrated into the DC microgrid, has the advantages of flexible configuration, smart and small size. This paper proposes an improved topology based on the recent proposed DCES with parallel structure, defined as DCES-3, for residential rooftop PV power generation, and proposes a control strategy based on the small-signal modeling. The proposed topology consists of a triple active bridge (TAB) and a Buck-Boost converter (BBC), and adopts the overall control scheme of three-dimensional decoupling based on single phase-shifting (SPS) control, and uses the BBC to connect the non-critical load (NCL) in parallel to form an equivalent variable load. The DCES passes the power fluctuations to this variable load by changing the duty cycle of the BBC, while ensuring the power on the CL stable. Compared with DCES-3, it has the advantages of clearer concept of ‘spring’, easier analysis of transmission power and zero-voltage switching condition, controllable power quality of the NCL, lower scene transformation and production costs. Finally, the correctness and effectiveness of the proposed DCES topology and its control have been validated by both simulation and experimental results.