Self-Synchronized Startup for Voltage Sensorless Grid-Tied Inverters

Sensorless voltage control methodologies for grid-connected systems are increasingly favored over traditional voltage-based controls due to their resilience against sensor malfunctions, their reduced sensitivity to grid voltage harmonics, and their ability to mitigate instabilities arising from interactions between voltage sensors, phase-locked loop (PLL) dynamics, and current control loops. Traditional controls, which rely on voltage sensors at points of common coupling (PCC), often encounter difficulties, especially during startup phases where synchronization is challenging due to the absence of external voltage signals for reference. Addressing these issues, this paper proposes a novel synchronization approach for grid-connected converters that operates without the need for voltage sensors and is adaptable across various filter types. This method utilizes a resonant controller paired with a variable virtual resistor to emulate the operational characteristics of synchronous generators while incorporating adaptive inertia. This innovative combination not only facilitates a quicker system response but also significantly lowers inrush currents, enhancing overall system stability and efficiency. Comprehensive simulation results under a range of filter types and grid strengths, along with corroborative experimental data, substantiate the effectiveness of the proposed synchronization technique.