Deadbeat voltage control for a grid-forming power converter with LCL filter

Grid-forming power converters are controlled as voltage sources to regulate the grid voltage and frequency. These converters can increase power system strength if they impose a voltage waveform resilient to grid transients. For this reason, in this paper, we propose a deadbeat control strategy of the capacitor voltage for high power converters with LCL filter. To damp the LCL resonant poles, an active damping strategy is developed, based on a modification of the deadbeat control law. With this purpose, a notch filter is applied to the electrical variables allowing to emulate different damping resistances for the fundamental component and the harmonics. As a result, the active damping does not introduce tracking errors of the fundamental frequency component, while it provides damping to the filter resonance. The proposed strategy does not require knowledge of the grid impedance, an interesting feature in grid-connected power converters because the grid impedance is generally unknown. Experimental results validate the proposed strategy.