R&D On Matrix Converter And Its Application In Electric Driving System

Various converters have been applied successfully in almost all the industrial fields and have a large market capacity owing to the excellent properties and low cost of AC driving system. But there are some problems such as low input power factor and high THD (total harmonics distortion) in input current for the general AC-DC-AC drives which use three-phase bridge rectifier to carry out AC/DC converting. Furthermore their structures are not very compact due to the large electrolytic capacitors and they can not run in four quadrants, i.e, the energy generating by the motors can not be fed back to AC input source. Therefore, research and development of converter which has high input power factor, low THD in input current, compact volume and the possibility of four quadrants running is the developing trend of drives. Matrix converter (MC) satisfies all the above merits and complies with the development of drives. MC has become hot research fields of converters although there are some problems in the MC at present. Research on MC based on space-vector modulation (SVM) and its problems of the application in driving system is presented in this dissertation, which is mainly divided into two parts. The first part is concerned with the basic theory , modulation process and characteristics of MC. The second part carries out the analysis and research on the problems faced by MC when it is used in the driving system and some solution ways are proposed.In the preface, the background, purpose, meaning and achievements of the MC research work in this dissertation are presented and the situation of research and development of MC in recent years is introduced.In the first part, all the conclusions of theory analysis on SVM and modulation mechanism of AC/DC, DC/AC and AC/AC converting are verified by the simulation based on the Saber software according to theprinciple of SVM and the equivalent AC-DC-AC structure. The SVM process of DC/AC and DC/AC converting is firstly analyzed and then they combine into the AC/AC converter on which the research of composing process of SVM is carried out. It is proposed that the input phase displacement is in the scope of ?0?and average value and direction of the DC voltage will also change with it under the inductive load. And furthermore it is pointed out that the optimum phase displacement is in, ?0? otherwise the electrical energy will exchange several times during half-period between the load arid supply. This will lead to negative effect on the switching-state shifting of main circuit of MC. Under the above work, a new modulation method of all the AC/DCJDC/AC and AC/AC converting based on SVM, which called optimized modulation, is proposed to decrease the switching times in the modulation processes. The transfer process of dual switches of MC main circuit is analyzed in detail, from which two rules are derived to attain to the minimum switching times. It is very helpful to simplify the modulation of converting and decrease the switching loss. It solves one of the difficulties of MC realization. In addition, the logical relation of driving signals of the switches of main circuit is pointed out for DC/AC converting. Two methods of building simulation model of SVM algorithm is presented and their thought is helpful to reduce the calculating time of control system and simplify the modulation. Both the simulation and experiment prove that the optimized modulation is practical and possible.In the second part, firstly, it is proposed that the difference between MC and general converter is that the input phase displacement of MC is controllable. Secondly, problems of starting of motor, feeding back of energy, regulating of speed and input power factor are studied when MC is applied to the driving system of three-phase asynchronous motor. It is demonstrated that MC has the commonness with general converters in thestarting ways. The running of four quadrants is analyzed and energy feeding back is shown clearly by the simulation. A method of modulating-coefficient compensation is prop...