Selective Harmonic Current Control Strategy in Active Power Filters

In this paper,one conventional proportional integral(PI) control and one new current control,for shunt active power filters design,were compared.Because of the system stability constrained,the system loop gain of the PI control is restricted.Hence,in order to improve the system compensation performance,a new current control scheme for selective harmonics compensation was proposed for shunt active power filters.Based on the conventional PI control,the new method extracts the main harmonics(the 5th and 7th harmonics mainly) respectively,which are controlled by different PI controllers independently.Simultaneously,another PI controller is employed to deal with the other harmonics all together.The design method is provided,which increases the system loop gain to follow the main harmonics,improves the compensation capability of APFs,and achieves the control system an perfect frequency response.Conclusions are supported by both simulations and experimental results on a 30-kVA laboratory APF,indicating a reduction in line current THD factor from 23.21% to 3.75%.