Grid Voltage Estimation for Single-Phase Inverters Using Sensorless Observer Technique

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This paper proposes a sensorless phase synchronization method for single-phase grid-connected inverters that avoids the requirement for a voltage sensor. The method models the actual grid impedance as a virtual impedance and represents the grid voltage in the corresponding synchronous reference frame. To construct the synchronous voltage, a 90-degree phaseshifted virtual voltage is then generated, which is used to estimate the grid phase and frequency. The estimated voltage subsequently undergoes processing through a low-pass filter (LPF) and a disturbance observer to extract the final phase and frequency components. The proposed method features low computational complexity and is amenable to real-time implementation on low-cost microcontrollers. It also exhibits robustness against grid-impedance mismatch and harmonic distortion, maintaining stable phase and frequency estimation. The effectiveness of the proposed approach was demonstrated through both simulation and experimental results.