Sensorløs kontrol af aktiv ensretter / Sensorless Control of three-phase active rectifier

Control of an active rectifier is very similar to vector control of an induction motor. The speed control loop of a vector drive is replaced by DC-link voltage control and the reference angle between stator current and stator or rotor flux is replaced by a reference angle of supply voltage. PWM rectifiers can provide precise regulation of output DC voltage, low harmonic distortion of line current, near sinusoidal current waveforms, regulation of input power factor to unity and bi-directional power flow. Essentially, the PWM rectifier is the same as the PWM inverter except for the direction of power flow. Normally, the PWM rectifier needs three kinds of sensors: * dc-voltage sensor * ac-line current sensors * ac-line voltage sensors. The dc-voltage and the ac-line current sensors are an important part of the over-voltage and over-current protection, while the ac-line voltage sensors may be omitted. The task in the project is to reduce the number of sensors in order to reduce cost and increase reliability. The project is sponsored by Socrates Erasmus Programme. (Frede Blaabjerg; Mariusz Malinowski, Marian Kazmierkowski, University of Warsaw; Marco Liserre, Politechnica de Bari, Italia)