Research On Active Power Filter Control And Modulation Strategy

With the progress of society and the development of industrial production capacity,a large number of emerging power electronic equipment has been put into use,resulting in increasingly serious harmonic problems in the power grid.Active power filter(APF)is an effective device to control harmonic pollution,this paper uses three-phase three-wire parallel APF as the research object,the current tracking control,DC-side voltage control and pulse width modulation strategy are studied.Aiming at the accuracy of APF current tracking control,a non-singular terminal passive sliding mode current tracking control strategy based on Euler-Lagrange(E-L)model is studied.Analyze the passiveness of APF,establish an E-L model and design a conventional passive controller based on the model.Combining non-singular terminal sliding mode control with conventional passive control,the saturation function is used to improve the chattering problem in conventional sliding mode control.Comparison of simulation verification shows that the passive sliding mode control strategy studied has better speed and accuracy.Aiming at the stability problem of APF DC side voltage control,a DC side voltage control strategy based on auto disturbance rejection control technology is proposed.The principle of power exchange on both sides of APF AC and DC is analyzed,and a DC side voltage control model based on power exchange is established,The design parameter adaptive PI controller is used as arrange transition process,realize the DC side voltage soft start.According to the APF disturbance signal model,a second-order extended state observer is designed and the error feedback link is linearized.Compared with the control effects of several common DC side voltage control strategies,the proposed control strategy has better performance in terms of starting speed,overshoot and dynamic recovery performance,and can achieve APF DC-side voltage stability control.Aiming at the problem of APF switching loss,that is,operating efficiency,a high efficiency modulation strategy based on discontinuous pulse width modulation(DPWM)strategy is proposed.Introduce the working principle of SVPWM and DPWM,calculate the zero-sequence component required by the modulated wave,and analyze the classification and characteristics of DPWM through the waveform of the zero-sequence component.A DPWM strategy combining DPWMMAX and DPWMMIN is designed to solve the problem that the use of the two alone will cause uneven switching of the upper and lower arms of the PWM converter and affect the service life of the power device.The selection of DPWMMAX and DPWMMIN is realized by the current and voltage of the power device,and the modulation method is used to realize its function.Through the power device loss model,the DPWM switching loss model is established,and the effect of various modulation strategies on the APF operating efficiency is analyzed.Simulation comparison shows that compared with SVPWM,the proposed modulation strategy can effectively improve the operating efficiency of APF on the premise of satisfying the harmonic control effect.A three-phase three-wire APF experimental platform was built,and the effectiveness of the control and modulation strategies studied in this paper was verified through experiments,and the experimental errors were analyzed.The paper has 59 pictures,9 tables,and 97 references.