The Control Strategy And Application Of Three-Phase Current PWM Rectifier

With the rapid development of green energy, the technology of PWM rectifier plays increasingly important role in the field of power electronics. As a kind of necessary converter connecting electrical equipment to the power grid, the PWM rectifier can reach the target of reducing harmonic pollution and adjusting power factor. With regard to topological structures, there are two types of PWM rectifiers-Voltage Source PWM rectifier (VSR) and Current Source PWM rectifier (CSR). A massive research has been conducted in the former ones, while some control stategies on VSR is unagreeable to CSR equally, because LC filtering part is added to the AC link and large inductor is used to store energy which makes it difficult to control the system because of strong coupling and nonlinearity. However, the study of control stategies and application fields on CSR is desirable and valuable, not only to its irreplaceable merits like restricted harmonic current, protective short circuit and reducible voltage, but also to significant application in some industrial scenes like induction heating, high-power metal industry and electrochemical industry.This paper is focused on three-phase CSR, including mathematical modeling, modulation technology, control methods and application areas. The specific contents are as follows.Initially, the similarity and difference of topological structures about VSR and CSR is discussed and working principle is introduced. In order to lay a theoretical foundation for the subsequent chapters, mathematical models are built respectively under three-phase or two-phase stationary coordinate system, and two-phase rotating coordinate system, which demonstrates that CSR is a multivariable, nonlinear, strong coupling control system.Addtionally, modulation technology is introduced. Take SPWM as an example, the process of PWM signal generation is illustrated in details, followed by the relevant pinciple of SVPWM. The Matlab/Simulink simulation results verify the theoretical analysis and provide with super advantages such as reduce harmonic pollution, achieve unit power, accelerate dynamic response and so on.What is more, this paper has a research on several control strategies including indirect and direct current control, power control and discrete state feedback control. The basic theory of every control methods is presented at first, and then simulation models are built. By comparing merits and demerits, it is vital to provide new control strategies of CSR.At last, in order to regulate widespread application for CSR, PV grid system and superconducting magnetic energy storage are mentioned. As for the former one, the MPPT technology is provided based on disturbance observer method and direct current control strategy. It turns out that the functions of CSR are different under different loads and grid-connected congdition. As for the latter one, the mathematical model has been built and the working principle of discrete state feedback control has been explained simultaneously.The highligts are as follows.On the one hand, relatively comprehensive comparations of different control strategies under the same external conditions are discussed. On the other hand, discrete parts are added to traditional state feedback control, with the advantage of controling active and reactive power indepently.