Design and control of a buck-boost charger-discharger for DC-bus regulation in microgrids

Abstract

In DC and hybrid microgrids (MG), the DC-bus regulation using Energy Storage Devices (ESD) is important for the stable operation of both the generators and loads. There are multiple commercial voltage levels for both ESD and DC-bus; therefore, the ESD voltage may be higher, equal or lower than the DC-bus voltage depending on the application. Moreover, most of the ESD converter controllers are linear-based, hence they ensure stability in a limited operation range. This paper proposes a system to regulate the DC-bus voltage of an MG accounting for any voltage relation between the ESD and the DC-bus voltage. The proposed system is formed by an ESD connected to a DC-bus through a bidirectional Buck-Boost converter, which is regulated by a Sliding-Mode Controller (SMC) to ensure the system stability in the entire operation range. The SMC drives the Buck-Boost charger-discharger to regulate the DC-bus voltage, at the desired reference value, by charging or discharging the ESD. This paper also provides detailed procedures to design the parameters of both the SMC and the charger-dischager. Finally, simulation and experimental results validate the proposed solution and illustrate its performance.