Discrete-time AFC control of a single-phase full-bridge LCL PWM rectifier

Controllers for ac/dc power converters are subject to many constraints: first, they must be reliable when working conditions are not ideal, i.e., when the grid voltages present sags or swells, big impedances, changes in the frequency or harmonics. Second, they must be robust since the plant is not perfectly know (parametric uncertainty), it may change over time (load changes) and they must reduce to the minimum the currents´ harmonics. And third, they must operate using the minimum number or sensors to reduce the cost. On the other hand, the use of digital controllers is very common today since it makes easier the implementation and gives them flexibility. In this paper, a discrete-time control technique based on Adaptive Feed-forward Cancellation (AFC) is proposed for a full-bridge single-phase power rectifier. The controller has been entirely designed in discrete-time, avoiding approximations from continuous-time. The experimental results show that AFC controllers are not only robust, but also they present a very good performance.