Analysis of an offset error on a single-phase grid-connected inverter based on a proportional-resonant controller

In single-phase grid-connected inverters, an offset error in measured phase current on grid side is occurred by a current sensor and unbalanced voltage and nonlinearity characteristics of analog components in a measurement device. When current containing offset error is used for current control, it results in DC offset and the second harmonic component of fundament frequency in phase current of a grid side. The DC offset and the second harmonic component yield reduction of inverter efficiency. This paper presents an offset error compensation algorithm for grid-connected single phase inverters using a proportional resonant (PR) controller. The proposed algorithm is verified in simulation and experiment.