Sliding mode based droop control strategies for parallel-connected inverters in railway vehicles

This paper deals with the design of sliding mode based droop control strategies for parallel-connected inverters in railway vehicles. Indeed, the presence of auxiliary devices, which can be connected and disconnected at any time instant, makes the introduction of parallel modules an efficient solution. Among the possible techniques, droop control represents an efficient and easy-to-implement approach. However, each inverter is affected by load variations, nonlinearities and unavoidable modelling uncertainties, thus making the use of sliding mode controllers perfectly adequate for this kind of application. More specifically, relying on a sliding surface designed on the basis of a voltage-current droop characteristic, two second order sliding mode (SOSM) control algorithms, belonging to the class of Super-Twisting and Suboptimal SOSM control, are proposed.