An Adaptive Observer-Based Voltage Parameter Estimation Method for Single-Phase Grid with DC Offset

In this paper, a novel adaptive observer is proposed to estimate the parameters of single-phase voltage signals that contain a DC offset. A state-space model of the voltage signal with DC offset is first derived and shown to be observable. To eliminate steady-state estimation errors caused by DC offsets, an observer is designed to estimate the AC in-phase component, its quadrature component, and the DC offset in real time. Although the observer design initially assumes a known grid frequency, an auxiliary frequency estimator is subsequently coupled with the observer to update the frequency estimate online. Voltage amplitude and phase are obtained from the estimated in-phase and quadrature components. Lyapunov-based analysis is used to establish the stability and convergence of the proposed scheme. Experimental results demonstrate the method’s accuracy and robustness in the presence of DC offsets.