"Sensorless" control of 4-quadrant-rectifiers for voltage source inverters (VSI)

This paper presents a novel "sensorless" control strategy for three phase pulsewidth modulated (PWM) power supply rectifiers. The proposed method is based on the voltage oriented control but it does not use any AC-line voltage sensors and does not need accurate parameters of the controlled system. Because of the lack of voltage sensors, the grid voltage has to be estimated. Two voltage estimation methods are used: voltage estimation by instantaneous active and reactive power estimation and a novel voltage estimation by phase tracking. These methods are compared with each other and the experimental results are presented. The control concept was realized on a prototyping system for power electronics control. The influence of the system parameter variations (e.g. line inductance) on the control behavior is investigated. Using the proposed sensorless method it is possible to reduce the sampling frequency of the AC-line currents, because there is no need for synchronization with the PWM-pulse pattern and there is no need for additional test signals. As there is also no need for line side voltage sensors the cost reduction for the PWM rectifier control system is significant.