Enhanced Voltage Sensorless Control for a PWM Converter with DSOGI-FLL Under Grid Disturbances

This paper presents Enhanced Voltage Sensorless Control for PWM converter with DSOGI-FLL under grid disturbances. Even without grid voltage sensors, the proposed method accurately estimates the grid angle and voltage, which are necessary for power transfer between the DC link of the PWM converter and the grid. The estimated grid voltage obtained through observer design is separated into positive and negative sequence components, and the grid frequency is estimated using the Dual Second-Order Generalized Integrator Quadrature Signal Generator (DSOGI-QSG) and Dual Second-Order Generalized Integrator Frequency-Locked Loop (DSOGI-FLL). The estimated positive and negative sequence voltages were effectively controlled using a dual current controller. The method operates effectively under normal, balanced AC source conditions and in various grid fault scenarios, including unbalanced voltage, harmonic distortion, voltage sag, and frequency step changes. The validity of the proposed method was evaluated through experimental results by using a grid simulator to implement the fault condition.