Abstract In this Thesis, a method is presented for compensating the inverter output voltage, which does not depend to inverter switches specifications. In this method, the required pulse wide for compensating output voltage is obtained by use of sixth harmonic feedback of stator current in synchronous reference frame. In this way, the produced distortion in output voltage which is created as a result of the dead time effect and the zero current clamping, at low frequency and in light load, is compensated. This method is applied in indirect vector control induction motor. To include dead time between one leg related switches, a method is presented to prevent short circuit in DC link, which doesn’t lead to difference creation between reference voltage and inverter output voltage. Combination of this method with inverter output compensation by use of sixth harmonic feedback is used for inverter output voltage compensation in induction motor sensor less vector control. In sensor less vector control for rotor speed estimation, at first, reference frame on the base of rotor flow estimation has been used. The model which has used as a reference is such that rotor resistance variation and DC offset trace is compensated in it. With this combination speed control at low frequency has made possible. Simulation results show that speed estimation method is sensitive to noise. To solve this problem, reference model on the base of stator current estimation is used. A method is presented to estimate stator current which does not depend to stator resistance and current estimation does not require derivative. Thus, the presented method is stable to stator resistance variation, DC offset and noise effect and at low speed is applicable. |
