A Robust Nonlinear Multi-Variable Controller for a 5-Switch Bi-Directional DC-DC Converter for DC-Microgrids Applications

The employment of DC-Microgrids based on renewable power generation has shown to be a really good option for the decentralization of the conventional power grid and its modernization. However, the intermittent nature of renewable energy sources and the large variations of power demand caused by variable loads still represent a challenge from the control point of view, where the usual approach for the control strategy of DC-Microgrids still relies on linear PI-controllers and their simplicity. Recent literature has shown that the employment of such controllers, usually employing a linearized model designed for a specific operating point, represent a major factor on the underperformance and inefficiency of DC-Microgrids. To deal with these limitations, nonlinear controllers capable of providing a much broader operating region have been used to assure robust and stable operation for DC-Microgrids. The drawback of such controllers, and the main reason to still prevent their use on a larger scale, is that they usually present more complex models and a heavy mathematical approach is necessary in order to determine the control law, This paper will present in detail the analysis, modelling, and control design of a multi-variable nonlinear controller based on input-output feedback linearization for a 5-switch bidirectional DC-DC converter. The performance of the nonlinear controller is verified by means of simulation results for a case study concerning the connection of a Supercapacitor (SC) to a controlled DC-Microgrid.