Abstract
In this paper, a two-stage three-port isolated bidirectional DC-DC converter (BDC) for hybrid energy storage system (HESS) applications in DC microgrids is proposed. It has an enlarged zero-voltage-switching (ZVS) region and reduced power circulation loss. A front-end three-phase interleaved BDC is introduced to the supercapacitor (SC) channel to compensate voltage variations of SC. Consequently, wide ZVS range and reduced circulation power loss for SC and DC bus ports are achieved under large-scale fluctuating SC voltage. Furthermore, a novel modified pulse-width-modulation (PWM) and phase-shift (PHS) hybrid control method with two phase-shift angles is proposed for BA port. And it contributes to an increasing number of switches operating in ZVS mode with varying battery (BA) voltage. Phase shift control with fixed driving frequency is applied to manage power flow. The ZVS range as well as the current stress of resonant tanks under varying port voltages is analyzed in detail. Finally, a 1 kW prototype with peak efficiency of 94.9% is built, and the theoretical analysis and control method are verified by experiments.
Highlights
The development and utilization of renewable energy have turned out to be new solutions for the worldwide energy depletion and environmental pollution problems [1]
To verify the validity of theoretical analyses, a 1 kW prototype was built in the laboratory
MOSFETs adopted in the system are C3M0065090D units from CREE (Durham, NC, USA)
Summary
The development and utilization of renewable energy have turned out to be new solutions for the worldwide energy depletion and environmental pollution problems [1]. In order to achieve efficient utilization of distributed energy generations, DC microgrid has become a research focus in recent years [2,3,4]. The output of several renewable energy sources is intermittent and time-varying, and the load demand is uncertain [5]. Storage units are usually used to balance the power supplies and loads in DC microgrids. Several studies use hybrid energy storage systems (HESSs), which are composed of SC and BA, to improve stability and reliability of DC microgrid [6,7,8]. Numerous literatures have researched on energy management and power sharing strategy of HESS in DC microgrid [9,10,11,12,13,14,15,16]. The design of interface converters between HESS and DC microgirds is still considered as an emerging area of research
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