Research On Active Power Filter Harmonic Detection And Suppression Technology

The wide application of various non-linear loads in ships makes power control more efficient and convenient,but it also brings serious harmonic pollution to the power grid.Active power filter has become one of the main measures to control harmonics due to its advantages of real-time compensation and flexible control.The thesis takes the three-phase three-wire power filter as the research object,and conducts research from the aspects of harmonic current detection,phase-locked loop technology,compensation current tracking control and DC side voltage control.Firstly,from the perspective of the generation and harm of harmonics in the ship’s power grid,the current harmonic control methods and governance standards are summarized.Then the basic working principle of the power filter is analyzed.According to the relationship between voltage and current and around the switching function,a mathematical model of the power filter is built.The main parameter determination methods such as DC side capacitance,voltage,and AC side inductance,are analyzed,which provides a theoretical basis for follow-up research.Secondly,based on instanteous reactive power theory,the thesis analyzes the applicability of the pq detection method and the ip-iq detection method from a theoretical perspective.The detection method of specific harmonic based on synchronous harmonic rotating coordinate system is mainly studied,which could relalize the detection and separartion of each harmonic component.The thesis comparatively analyzes several common phase-locked loops,and introduces the cascaded harmonic elimination module to improve the performance of dual second-order generalized integrator phase-locked loop.Then,the common current tracking control methods are briefly introduced,and the advantages and disadvantages of thehysteresis comparison method,the SVPWM modulation method and the SVPWM-based hysteresis current control method are analyzed.An improved SVPWM-based hysteresis current control method for judging the sector of the reference voltage u* by judging the polarity of the three-phase error line current is introduced.Through the discussion on the necessity of DC side voltage control,it is determined that the thesis uses PI adjustment to control the DC side voltage.Finally,a simulation model of the active power filter system was built using the Simulation software platform to simulate the performance of the phase-locked loop,the specified sub-harmonic detection,the current control method and the DC side voltage soft start,and the results were analyzed.