An Ellipse-Optimized Composite Backstepping Control Strategy for a Point-of-Load Inverter Under Load Disturbance in the Shipboard Power System

The shipboard power system (SPS) is expected to be configured as a hybrid microgrid (MG) to realize redundant bus design and high penetration of renewables (REs). Point-of-load (POL) inverters in SPSs play a critical role to feed for sensitive ac load. To realize voltage-oriented control objective under load disturbance due to load uncertainty or nonlinearity, this paper proposes an ellipse-optimized composite back-stepping control strategy for a POL inverter. Firstly, the backstepping algorithm is harnessed to derive the pseudo-inductor-current-loop reference and decoupled switching functions in d-q frame, which can rigorously guarantee the global large-signal stability of the system. A Kalman filter is designed to estimate the load current and feedforward it to the backstepping controller for load disturbance rejection, saving three current sensors. The controller gains are quantitatively selected to achieve the optimal system damping and maximized dynamic response, which can be intuitively interpreted via an ellipse-based strategy from a geometrical point of view. Rigorous stability proof and robustness analysis of the system is also provided. Finally, simulation and experimental results verify the effectiveness of the proposed control scheme.