A Sensorless Grid Voltage Estimation Scheme for a Single-phase Voltage Source Inverter

Synchronisation is an essential operational requirement for grid-connected voltage source inverters (VSIs). Several schemes have been proposed to maintain synchronisation without using voltage sensors. However, establishing the initial synchronisation without voltage sensors remains challenging because of the absence of the grid voltage magnitude and phase information. This paper presents a grid voltage estimation scheme for single-phase VSIs that uses a startup pulse width modulation (PWM) control approach, which constrains the modulation depth such that the inverter current is mainly driven by the grid voltage. This allows the accurate detection of the grid voltage magnitude and phase from the switched inverter current measurement. A mathematical model with key analytical design equations is presented. The scheme’s voltage estimation accuracy and its application for grid synchronisation are validated using switched simulations in Altair PSIM.