Optimized sensor charge controller for bus voltage stabilization in hybrid battery-supercapacitor fed islanded microgrid system

This paper proposes a novel Energy Storage Device (ESD) charge controller for integrating multiple hybrid ESD (battery-supercapacitor) stacks within the DC microgrids. A low-cum-medium power islanded DC microgrid system, consisting of Distributed Energy Resources (DERs), loads and isolated/non-isolated multiple hybrid ESDs is configured for this purpose. The hybrid ESDs tackle the source-load and DC bus voltage fluctuations smoothly, while multiple ESDs foster system redundancy. As opposed to conventional ESD controllers where sensory requirements increase proportionally with the number of ESDs converters connected, the proposed algorithm uses just one voltage sensor placed at the DC link bus. The Power Management Strategy (PMS) is designed accordingly, considering the system power flow status and State of Charge (SOC) of each ESD. The minimum use of sensors leads to simplified control circuitry, better system stability (less control error tuners required), ease of hardware implementation and makes system economical for market outreach. The viability of the proposed ESD controller for multiple hybrid isolated/non-isolated ESDs converter has been tested through the simulation platform during the transient conditions. The power exchange between different ESDs in factors of 1:1 and 1:2 is verified. The DC link voltage is stabilized with the ripple factor of <1.0 %. For experimental verification, scaleddown laboratory prototype of DC microgrid (approximate to 0.25 to 0.5 kW) is made and tested in ESD charging-discharging modes. A fast transient response slope of up to 2.0 kW/s. is tested using the proposed controller on the experimental platform. Since the proposed controller is less computation intensive, a low-cost microcontroller serves the purpose.