Broadband Impedance Modeling and its Characteristic Analysis of Single-phase Grid-connected Inverter Considering Frequency Coupling

Abstract

In a single-phase grid-connected inverter, because the constructed orthogonal signals are not strictly orthogonal in broadband and the control of dq-axis is asymmetric, when the voltage disturbance with frequency of fp is injected in point of common coupling (PCC), not only the response current with frequency of fp will be generated, but also the response currents with frequencies of fp–2f1 and fp+2f1 will be coupled. In order to accurately establish the broadband impedance model of the single-phase grid-connected inverter, the frequency coupling mechanism is analyzed in this paper. Considering the influence of the constructed orthogonal signal, current loop, phase-locked loop (PLL) and frequency coupling, a broadband impedance model of the single-phase grid-connected inverter is established. Its broadband impedance characteristics are analyzed. The simulation results verify the accuracy of the established model.