Research On Speed Sensorless Vector Control Of High Voltage Converter

High voltage AC drive systems have bright prospect in high power pumps and fans, rolling mill and so on, where using adjustable speed scheme can not only save energy greatly but also improve the dynamic performance of the motor. With the development of high-voltage and large-current device, multilevel inverter becomes the most popular topology in high-voltage adjustable speed scheme. This paper is base on high voltage converter designed by ZhuZhou Electric Locomotive Research Institute, which adopts the cascaded H-bridge multilevel topology. The main contents are shown as follow.1. First of all, conventional topology and modulation method are respectively generalized.Consequently; topology of three-level H-bridge cascaded type multi-level inverter with clamped-diode is specified. Furthermore, both operating principle and mathematical model are presented.2. A speed sensorless vector control method for high voltage converter is researched in this paper. And this paper develops a simplified maths model of induction motor based on static axis.A new advanced rotor flux estimated method which combines the advantages of traditional voltage method and current method is adopted, and direct speed estimation is employed.All control system is verified by simulation software.3. The cascaded H-bridge multi-level inverter with vector control has a large number of voltage vectors, which makes selection and optimization of its voltage space vectors difficult. A novel SVPWM control strategy is presented for cascaded multilevel inverters.The closest space voltage vector to the reference vector would be chosen as the optimal one to be transmitted to the load. When modulation is enough, the error can be neglected for the distribution density of cascaded multi-level converter's space voltage vectors. Simulation waves and experimental results have verified the algorithm.