The Study On Key Application Techniques Of Shunt Active Power Filter

The active power filter,with the main function of harmonic suppression and reactive compensation,after 40 years development has become mature,moving toward large-scale industrial applications.However,in the complex industrial field, some potential problems has been met with the application of active power filter.Based on Shunt Active Power Filter(SAPF) industrial applications,this thesis will research these issues.With simple manufacture,installation and low cost,a large number of reactive compensation capacitors and passive filters were applied in the industrial field. However,it maybe causes the system resonance and the corresponding damage to the equipment when SAPF was put into operation.With a detailed analysis of active filters in various control methods and the harmonic amplification mechanism,a novel control method in which the grid voltage,grid current and load current are detected to control the output current of SAPF is proposed.The proposed control method improves system performance of harmonic current compensation and inhibits other harmonic interference effectively,avoiding system resonance.The power grid not only contains the current-type harmonic sources,but also includes a large number of voltage-type harmonic sources.SAPF,which only has better inhibition to current-type harmonic source,is not only less inhibitory to the voltage-type harmonic source,but also lead to harmonic amplification and load over current.This thesis analyzes the harmonic characteristics of diode rectifier with a large smoothing dc capacitor(the representative of voltage-type harmonic),interprets why Shunt Active Power Filter(SAPF) is not suitable for compensation voltage-type harmonic,and reveals the reason why the load peak current is enlarged at the same condition by using the subsection resonance mechanism.Furthermore,two-type methods are proposed to deal with the problems by this paper,i.e.to modify the topology/parameters so as to change the resonant frequency of the system;while the other is to improve and change SAPF's compensation bandwidth to be a selective or limited one.Both of them can suppress the harmonic current effectively and guarantee the load-side current without significant enlargement.The industrial field not only includes diode rectifier with inductive filter, thyristor rectifier,diode rectifier with capacitor filter load as well as other fans, pumps and other motor-type loads,etc,but also contains reactive compensation capacitors and passive filters.This thesis analyzes the system behavior before and after SAPF put into operation in various loads,and gives the corresponding countermeasures for the possible risks.Simulation results show the effectiveness of the proposed method.