Research On Key Techniques Of Active Power Filter

With the power electronic equipment’s extensive using, non-linear loads in electric power system largely increased, the grid system has being polluted, and power quality has become worse and worse. Using the APF to suppress the harmonic and compensate the reactive power is an effective way. By comparison to conventional passive LC-filter, APF has the advantage of quick response, good output wave shape and dynamic performance.Therefore it is important to study it.The paper briefly presents the current situation and trends of active power filter,introduces the basic structure and principle of APF, it makes comparison among some conventional harmonies detection and current control methods, the influence of time delay inherent in the digital control system on the compensation effect of APF is analyzed in detail. To solve the drawbacks of time delay inherent in the digital control system on the compensation effete of APF, harmonic prediction a1 gorithms based on adaptive predictive filter was researched in the paper. In prediction algorithms based on adaptive finite impulse response(FIR) predictive filter, the least mean square algorithm is used to predict the signals to be detected, this algorithm is simple and easy to come true with digital controller.Finally, to validate the validity of the algorithm, it gives current waveform and harmonic ratios’ datum before and after the compensation by means of math model and computer simulation. The results obtained that, proposed predictive control methods have preferable dynamic responses and controlling precision, and the validity to alleviate the detrimental influence of time delay inherent in the digital control system on the compensation effete of APF. Built active power filter prototype, using DSP+FPGA software to achieve detection and control algorithms, make steady-state and dynamic verification. The results show that the algorithm in practical applications can also be achieved good compensation performance, has a good dynamic response under load mutation.