Multi loop deadbeat+repetitive and adaptive control for power converters with LCL filters

This paper proposes a current control technique for Pulse-Width Modulation (PWM) converters connected to the trough LCL filters. The system is modeled so that it results on two cascaded systems. One has nearly known parameters whilst the other is associated with the grid side, inductance and voltage, responding for the uncertainty and the disturbance, respectively. The model allows the implementation of a multi loop controller. An inner loop controls the capacitor voltage whilst the outer one is used to control the grid side current. This loop is implemented with a Model Reference Adaptive Control (MRAC) with Adaptive Feedforward Cancelation to compensate for the parametric variation and to reject the effect of the grid voltage at the point of common coupling. The outer control loop signal is the reference for the capacitor voltage, e.g., the reference for the inner loop. This control loop is implemented with a Deadbeat and a plug in Repetitive (RP) Control to compensate for the coupling effect of the grid side current and provide a fast response in steady state. This loop can be relatively well designed, since it is associated with the converter side inductor and the filter capacitor.