In a single-phase grid-tied inverter, the direct current (DC) offset error included in the measured grid side phase current has various causes, such as a non-ideal current sensor, unbalanced power supply of an operational amplifier, and nonlinear features of analog components in interface circuits, etc. If the DC offset error is included in the measured current, it causes the secondary harmonic of fundamental frequency and the DC component in grid phase current which result in degradation of inverter performance. In this paper, a theoretical detection method of the secondary harmonic of the fundamental frequency and a DC component in grid phase current for a proportional-resonant (PR) current control system is introduced. Based on the detection method, an algorithm for compensating DC offset error is also presented for single-phase grid-tied inverters. Simulation results and experimental verification of the DC offset error compensation algorithm are shown in this paper.
Two-sample PLL with improved frequency response applied to single-phase current sensorless bridgeless PFCs
