Research On Control System Of Shunt Active Power Filter

With the various power electronics being widely used, the current pollution problems such as harmonics and reactive current are growing. How to restrain the harmful current to improve the power quality becomes a major issue. AS a new power electronic devices to restrain the harmonics and suppress the reactive power, Active Power Filter(APF) especially parallel active power filter has a wide application in the industrial field, so doing research on parallel active power filter has important practical value.There are two important parts for the APF, the first part is the current detection circuit, it requires to detect the harmonic and reactive current real time and exactly; the other one is current track circuit, it generates logic signal to control electronic devices according to the relationship between the current command signal and actual compensation current. Both the two parts affect the performance of APF directly. So the paper does deep research on the current detection and current track algorithm.In the current detection aspect, first the paper studies on the conventional instantaneous reactive power(ip-iq)detection method, in view of the detection error is large when the three-phase voltage is asymmetry and the order and cut-off frequency of the low-pass filter make a large effect on the detection performance, the paper proposes a prove ip-iq detection method. In view that the conventional ip-iq detection method can only detect the total harmonic and complicated in the one-phase circuit,So the paper uses a harmonic detection method based on the Hopfield neural network,it can detect the amplitude and phase of fundamental and each harmonic timely and exactly, and the network does not require pre-training.In the current track aspect, first the paper studies on the common hysteresis comparison method, considering the hysteresis width make a large effect on the performance of the current track, the paper uses one cycle control which has a fast development in recent years, in order to further enhance the compensation performance of the APF, the paper then uses a kind of current track method based on inverse system.In the end, the paper establishes the models of the APF, the results shows the compensation system can make the current similar to the sine wave and have the same phase with the voltage, that is it can restrain harmonic and compensate the reactive power effectively.