Performance Evaluation of D-Q Current Controller for Grid-Connected Full-Bridge Inverter Under Nonlinear Load Conditions

In this study, a digital d-q frame current controller has been designed for an on-grid full bridge inverter with a critically damped LC filter. The d-q frame state-space model of the inverter has been derived for the current control design process. In order to ensure the synchronization with AC grid, a second-order generalized integrator (SOGI) mechanism with phase-locked loop (PLL) and frequency-locked loop (FLL) capability has been designed. Mathematical framework was tested using simulation tools. The control performance and harmonic analyses have been performed for the situations where AC grid is under the odd harmonic effects. According to the simulation results,, the designed d-q frame current controller ensures an injecting current to the AC grid within the boundaries of international power quality standards like IEC61000-3-2 under polluted grid condition.