Current Tracking Control Of Three-level Active Power Filter Based On The Inverse System Method

With massive use of nonlinear loads in power system, the harmonic pollution in power grid generated by them become more and more serious. The APF(active power filter), as a dynamic harmonic suppression power electronic device, has become an effective means in suppressing harmonic and improving power quality, which drawing more and more use and research attention. The traditional two-level APF has been unable to meet the requirements of high voltage, large capacity and high compensation accuracy, multi-level technology is born at the right moment, especially, the three-level APF has been increasingly popular. Current tracking control is one of the key factors that determine the quality of APF compensation performance, enhancing the effect of current tracking control has very important significance to improve the performance of APF. Therefore, this thesis studies current tracking control based on the model of the three-level APF.Firstly, this thesis deduces the mathematical model of three-level APF in detail based on the equivalent model of main circuit, and this mathematical model provides the basic of subsequent current tracking control research. My work mainly discusses the basic principle and implementation method of the three-level SVPWM(Space Vector Pulse Width Modulation) modulation technology based on the diode clamping type converter, this modulation technology is an important part of the three-level APF’s current tracking control.Then this thesis introduces the fundamental principle of inverse system and the determination method of the system’s reversibility. On this basis, this thesis brings inverse system control method into three-level APF’s current tracking control, which realizes linearized and decoupling control of the d-axis and q-axis compensatory current, and the conventional PI controller is used to constitute a close-loop control system. The Matlab/Simulink is used to simulation research for the three-level APF’s linearized and decoupling control method based on inverse system.Finally, this thesis presents a non-singular terminal sliding mode control method for current tracking control based on the inverse system linearized and decoupling control method. To begin with, this thesis introduces the fundamental principle of sliding mode control and non-singular terminal sliding mode, then designs a non-singular terminal sliding mode controller for the d-axis and q-axis compensatory current respectively and proves the stability of the closed-loop system in theory, also provides current tracking control block diagram using non-singular terminal sliding mode control method based on inverse system, conducts the simulation research for the current tracking control strategy in Matlab/Simulink environment. Simulation results show that the proposed current tracking control strategy has a better steady-state performance, dynamic performance and robustness.