The Research On The Sensorless Vector Control Of Cascaded Converter

The cascaded inverter are widely used in many applications such as high-power fan,the start of pumps and frequency control due to its advantage regarding reliability,harmonics,power factor,etc.In order to meet the high performance,the technology of vector control combined with the cascaded inverter is becoming a widespread concern hotspot.The high performance which used on vector control systerm requires speed feedback,but the speed sensor is hard to install or fix,and the cost increased obviously.The research on sensorless vector control for the cascaded inverter becomes a hot topic in the high voltage frequency conversion field.This paper which takes a cascaded inverter as the foundation,gives out a SVPWM modulation method and put forward sensorless vector control technology in cascaded converter system.The paper includes the following contents in detail.(1)Describes the topology and the modulation methods of the cascaded inverter, including the phase shift SPWM and the space vector pulse width modulation. Then the basic principle of phase shift space vector pulse width modulation and its implemented method have been introduced,and the output performance have been pretented according to the matlab(2)Based on the dynamic mathematical model of the induction motor,the sensorless vector control of rotor flux oriented have been described in detail,including the foundation function of vector control,flux observer model and the speed identification with MRAS.Then a vector control system solution with sensorless which used in the cascaded inverter system have been put out,and the control scheme have been proved feasibility according to the simulation.(3)Combined with the cascaded converter project I participated in,the control circuit and main circuit have been introduced,including the hardware and software designing scheme.Finally,according to experiment the cascaded converter with sensorless vector control which used on SVPWM modulation methods have been verified feasible,and the experiment results have been given out.