Mixed H2 / H∞ optimal control for three-phase Grid Connected Converter

Three-phase Grid Connected Converter (GCC), which acts as an important component for integrating the renewable energy into the smart grid, are attracting a great deal of attention. Traditionally, GCC are controlled with proportional plus integrator (PI) or Proportional plus resonant (PR) controllers in the rotating synchronous frame or stationary frame, respectively. However, those mechanisms show slowly response times for tracking the changing reference commands without considering the uncertainty and volatility in the grid. This paper investigates how to mitigate such restrictions using a mixed H₂ / H_∞ controller to control a grid-connected converter. The proposed controller ensures: a) the resulting closed-loop system is asymptotically stable for all admissible parameter uncertainties b) the given transient performance index can be guaranteed under uncertainties and disturbance. Simulation results show good transient and steady performance than the traditional PI control methods.