Voltage Sensorless Three-Phase PWM Rectifier Control Based on Linear Extended State Observer

Regarding significant harmonics from the grid voltage side, a control strategy for a 3-phase pulse width modulation (PWM) rectifier without alternating current (AC) voltage sensor based on Linear Extended State Observer (LESO) is studied. This strategy features a simple structure, accurate and rapid voltage estimation, and independence from control architecture, enabling precise and swift grid voltage estimation even under unbalanced grid conditions. However, traditional LESO inherently suffers from estimation errors. To address this, a Reduced-Order Linear Extended State Observer (RO-LESO) is proposed for grid voltage estimation. The stability and feasibility of RO-LESO are theoretically analyzed. As to the issue of excessive startup inrush currents, a virtual resistor startup strategy is proposed. This strategy does not require an additional resistors and switches. The feasibility and effectiveness of LESO are verified through experiments.