Improved hysteresis current control for active power filter

This paper presents an improved hysteresis current control to enhance the performance of current tracking control for active power filter while reduce the number of switching. This control technique utilizes the advantages of the fast dynamic response of the conventional hysteresis current control and the reduced switching number of the SVM scheme. While the current errors go beyond the outer hysteresis band, a suitable space voltage vector is selected to obtain fast current response, which corresponding the vector of the current error differential is of the largest partial vector in reverse direction of current error vector. Otherwise, the low harmonic current control of SVM is selected to track the reference current and limit the current error within the specified hysteresis band. A set of space vectors including the zero vectors to reduce the number of switching is determined from the information of the middle current error. Then a proper space vector selected according to the inner current error for better current. Lastly, the validity and rapidity of the proposed method are confirmed by experimental tests.