Research On Direct Power Control Of Three-phase Votage Source PWM Rectifier

As a result of continuous development in power electronic technology, applications of power electronic systems directly connected to the grid have been increasing significantly. Especially in the field of adjustable speed drives and other high-power electric energy conversion, demands for three-phase voltage source converter are extremely remarkable. Three-phase voltage source PWM rectifier is one of the important power electronic device, which performs AC- DC transformation with the abilities of adjustable dc-link voltage and unity power factor. In recent years, research on control strategies of three-phase PWM rectifier has become a hotspot.In this paper, first of all, from the perspective of the traditional direct power control strategy, the mathematical model of three-phase PWM rectifier is deduced. This paper introduces the theory of instantaneous power and basic concepts and principles of voltage oriented and virtual flux oriented direct power control. Also the operating principle of the switch table is derived and discussed, and the improvement aiming at the shortcomings of the traditional switch table is put forward. Secondly, this paper introduces the control strategy under dq coordinate system with fixed frequency direct power control based on SVM. Using dq coordinate transform can eliminate the coupling effects of power grid voltage e? and e? for reference voltage v? and v?. Finally, the above control strategies are simulated and compared in the steady-state performance and dynamic performance, etc.In terms of the new control strategy, this paper embarks from the predictive control and carried out a series of control strategies. Firstly, the single-vector predictive control based on cost function are studied and analyzed the performances of different cost functions. Secondly, the two-vector predictive control based on dead beat concept research is discussed and different PWM synthesis ways are introduced and compared. Finally this paper puts attention in the three-vector predictive control which can be basedon vector-chosen method or SVM concept. The former contrasts the different ways of vector selection and compares their control performances. While the latter, compared with traditional voltage oriented fixed frequency direct power control based on SVM, omits inner power PI loops, which can simplify the control strategy, and still keep good control performance. Finally, this paper introduces the three-phase voltage source PWM rectifier prototype design and experiment, including hardware design, software design and the analysis of the experimental results, etc. The control strategy of double closed-loop fixed frequency direct power control based on SVM is carried out and has performed good verification of control theory.