Integral-Type Terminal Sliding-Mode Control for Grid-Side Converter in Wind Energy Conversion Systems

This paper investigates robust control strategies for wind energy conversion systems with variable-speed permanent magnet synchronous generators, which are integrated into the grid to provide reliable, secure, and efficient electrical power. A three-phase grid-side converter without a grid transformer is connected to the grid using an LCL filter with low resistive losses. In these working conditions, an instantaneous power proportional integral (PI) controller for the outer voltage-loop in the grid-side converter is used to regulate the DC-link voltage and generate the required currents for the inner current-loop in the grid-side converter. Two integral-type terminal sliding-mode controllers are proposed to control the active and reactive powers exchanged between the converter and the grid. The switching signals in the controllers are softened to attenuate chattering. The time-varying gains in the controllers are constructed to reduce control energy wastage and avoid overestimation of the boundaries of system uncertainties. Simulated and experimental results validate the proposed method.