Research On Control Technology Of T-Type Three-Level Active Power Filter Based On HHT Harmonic Detection

With the advancement of science and technology and the popularity of power electronic devices,it is imperative to improve the power quality of the power grid.The power quality mainly involves voltage sag,abnormal frequency,harmonic and so on.As the main factor threatened the reliable o peration of the power grid,the higher the harmonic content is,the stronger the heating performance of user equipment is,which directly shortens the lifetime of equipment.Recently,much attention has paid on the harmonic suppression of APF,and the study focuses on the three-phase systems,while there are few literatures on the single-phase systems.The main circuit topology of APF is mostly in two-level topology.Due to the factors such as unsatisfactory voltage utilization,h igh energy loss and poor economy,the application in high-voltage and high-power is limited,and it is mainly used in medium and low voltage applications.Based on this background,multilevel converters are increasing popular.Taking single-phase T-type three-level topology as the main circuit,the research involves the analysis of working principle and the establishment of mathematical model on the single-phase APF,and the mathematical model is used for real-time control.In the control strategy,harmonic detection and compensation control as a core technology has a significant influence on the filtering effect.In this paper,harmonic detection mainly adopts HHT,which has the characteristics of adaptive ability,greater advantages in processing nonlinear signals and higher precision in compensating dynamic harmonics.The compensation control adopts the double closed loop control structure.The current loop is an inner loop,which uses PID strategy.The outer loo p is a DCside voltage control,which uses a linear auto disturbance rejection control technique.The single-phase T-type three-level modulation adopts the strategy of SVPWM,which has the advantages of fewer vectors,easier distinguishing and easier implementation than three-phase systems.Firstly,the theory proposed above is simulated by the Matlab/Simulink to analyze the feasibility.Then,using TMS320F28335 as the core controller and taking F3L100R12W2H3_B11 as the main circuit topology,the experiment al prototype of a rated power of 2.2kVA is designed and the corresponding control algorithm programs is written in Code Composer Studio.Finally,the communication with the experimental prototype is established by the interface of Labview to realize the instruction transmitting and system monitoring,which verifies the validity of experiment.Simulations and experiments are carried out and the results verify that the harmonic detection algorithm based on the HHT has a superior harmonic extraction capability,and the Linear auto disturbance rejection has stronger anti-disturbance performance and rapid performance on the voltage loop.The application of two strategies on APF can effectively reduce the proportion of harmonics and satisfies the requirement on power quality of the power grid.