Research On The Key Techniques Of Shunt APF

The research of Active Power Filter (APF) has made a dramatic breakthrough in recent years. It would be main equipment for harmonic suppressing in the future, but for the instability and a little high cost, APF has not been inputted market yet. The paper conducted research on practical applicability of single parallel APF. The design, assembling and commissioning operations which have been finished with the help of factory are presented in this paper.This paper leads from the following engineering problems:firstly, IGBT module frequently burned and exploded during the tests of APF prototype, which cause great losses to the research and development of APF, and also hinder the progress of APF, also. Secondly, in the operation test, the current is not ideal after the compensation, and waveform distortion rate is still high. Meanwhile, we find DC-Link voltage is not stable enough and the voltage fluctuation is too large, which is one of the main factors that influence the compensation effect. In addition, during linked network operation, APF and the reactive power compensation capacitor of factory occurs parallel resonance, which leads to amplified higher harmonics. How to solve these problems which be mentioned earlier is the core of this paper.Based on many times of IGBT modules burning, the reason is analyzed and discussed. First, the structure of main circuit and snubber circuit is improved, which solves the problem of modules over-voltage damage. Then, a variety of devices are selected such as resistance, capacitance and so on. At last perfect protection circuit is designed. It includes over-voltage, over-current, thermal and auxiliary protection circuit such as under voltage protection circuit, which can make the equipment operate safely and stably. In this paper, compensation effect is studied in depth. It also makes particular discussion on the time delay and the stability of DC-link voltage that affect the compensation effect. Optimal control of DC-link voltage is the efficacious way to improve the compensation effect and reduce the compensated current THD. It is helpful for APF study in the theoretical and practical way.This paper successfully developed a new parallel APF sample with greater capacity (100kVA and 250kVA) and better performance. It has good stability, fast dynamic response and low current THD. SVC capacitor in series with reactor has been improved which solved the problem of parallel resonance between APF and the capacitor of SVC. It confirms that the proper location installed not only test current more accurately but also eliminates parallel resonance, which is valuable for engineering application.