Research On The Model And Characters Of The High Frequency Chopped Wave Cascade Speed Control System For The Asynchronous Motor

As a kind of new energy saving technology, the chopped wave cascade speed control driver system is given more and more attentions to, and used in various industrial sites gradually, because of higher energy converstion efficient, lower controlling power, simple structure and safty, reliablility and so on merits, which unfolds the good application prospect, particularly in the high-voltage and large content asynchronous motor velocity regulation aspect.At present, the design about structure and control parameters of the chopped wave cascade speed control system resorts experience, lacking a deep thorough theoretics analysis basis. In view of existing situation, the deep systemical analysis and summary about the chopped wave cascade speed control system is finished in this paper such as the main circuit steady and dynamic properties, mechanical characters, control parameter design, system power factor calculation, reactive power compensation, harmonic current analysis and new type electronics and electric devices application to the inverter, and so on.The relationship between the input and output of the main electrical quantities in steady state is analysed thoroughly. By means of the the mean value in one cut period and ripple wave features of the main electrical quantities, the engineering calculation methods and selection principles are given. The two practical ways to compute and draw the mechanical characteristic curve are put forward according to the theory of the traditional cascade speed control system adopting shift-phase triggle mode. The reasons of the chopped wave mode mechanical characters superior to the shift-phase mode mechanical characters is illustrated.The methmatical model under the mean in one cut period of the chopped wave cascade speed control system is built up. The impact on the pulsation of the bus direct current and the capacitor voltage from the inductance and the capacitor and the slip ratio is analysed. The double closed-loops controlling design method is given about the chopped wave cascade speed control system, meanwhile, which is verified by the simulation model.Using the Graham-Schonholzer and Dobinson methods to calculate and study the harmonic features of the stator, the rator and the inverter sides. The relevant features and changing trend about the above harmonic currents is summarized. The various order harmonic current estimate formula is given and the reasons about the current vibration entering into the electric net is explained.The reasons about the lower power factor of the chopped wave cascade speed control system are explained. The system vector graph under two types of load is drawn. In view ofΓequivalent circuit, another method about computering the power factor is put up forward, and according to which, the engineering design to compensate system reactive power by capacitor is finished. At last, the compensatation design is verified by simulation model, and which proves its practicability.The principle of three-phases VSR is illustrated. The mathmetics models in three dimension static coordinate and d-q rotation coordinate of VSR are discussed. On base of that, the voltage and current double closed-loops designing way is deduced and summarized. The key parameters design way of VSR is offered under four quadrantal work conditions, and which is proved by simulation.Three phases VSR is applied in the chopped wave cascade speed control system to make capacitive reactive power to compensate the system reactive power in order to promote the power factor. Meanwhile, because the output current from the VSR is similar to the sine wave, the harmonic is repressed effectively, and the gain of improving the system features is attained, which is significant to the future development of the chopped wave cascade speed control system.