Research On The Control System Of Active Power Filter Based On LabVIEW

Nowadays, as power electronic devices are more widely used, harmonic pollution problems in modern power system is getting worse. Active power filter (APF) is a widely used device to reduce harmonic pollution, which can compensate harmonic dynamically with good effect. Therefore, study on the implementation of APF and improving the existing design method has important practical significance.APF is composed of main circuit, control system, capacitance and coupling transformer etc, and study in this paper is mainly on its control system. First, the widely used shunt-APF is selected to be the study object and the composition of APF control system is introduced, then methods of the two main parts——harmonic cur-rent detection and compensation current control are discussed. For harmonic current detection, this paper focuses on the p-q method based on the instantaneous reactive power theory. For compensation current control, hysteresis comparison method which is simple and easy to realize is chosen. In digital control system, there usually exists a delay of a sample period. To reduce the effect of this delay, the prediction algorithm based on LMS adaptive filter is applied, which achieves no difference tracking of compensation current.Normally APF control system are realized by DSP, which has the advantage of high precision, versatility and high cost-effective. The disadvantage is that it needs a long time to develop and debug, and the flexibility is poor. To solve this problem, this paper introduces virtual instrument technology which is advanced in measurement and control field into the design of APF. This technology can greatly shorten the de-velopment cycle, and its open idea makes the realization of the system more flexible. In addition, the system can realize in ordinary PCs, which don’t takes up additional hardware resources, and has friendly man-machine interface. In this paper, APF con-trol system is designed by using graphical virtual instrument software LabVIEW in ordinary PC. The system realizes harmonic detection and compensation current tracking control of APF, and generates high accuracy PWM control pulses.Due to the limit of conditions, the control system designed in this paper is not convenient to examine in actual power grid. Therefore this paper build the power sys-tem model and APF main circuit model in Simulink, and use the simulation interface toolkit of LabVIEW to realize data interconnection between LabVIEW program and Simulink model. On this basis,actual working process of APF is simulated. Simula-tion results show that the APF control system designed by LabVIEW in this paper can realize the control of main circuit and make it generate effective compensation current to power grid, and the compensation effect meets power system requirements...