Stability and Dynamics Enhancement Based on Proportional Derivative-Resonant Controller and Impedance Phase Shaping for LCL-Type Grid-Tied Inverters

Proportional-resonant (PR) controller are widely used in grid-tied inverters for improving current quality. Meanwhile, proportional voltage feed-forward (PVF) tends to become a default option for dynamics enhancement. However, both of them will induce phase lag in the output impedance of the inverter and thus lead to poor stability, while conventional phase lag compensation by phase correction of PR controller will seriously deteriorate system dynamics. Therefore, the control scheme based on the PR controller and PVF fails to balance stability and dynamics of grid-tied inverters. To address this issue, this paper proposes a proportional derivative-resonant (PDR) controller which utilizes derivative terms instead of phase correction to counteract the major part of phase lag without worsening dynamics, thus both stability and dynamics can be handled. Furthermore, a novel impedance phase shaping (IPS) method, which adopts the second order generalized integrator (SOGI) in the feedback path and the delay optimization in the feed-forward path, is proposed to compensate remaining phase lag for further enhancing the stability and dynamics. Finally, the parameter co-design procedure is given, with which the proposed strategies can synergistically ensure multiple performance metrics. Experimental tests validate the correctness of theoretical results.