Research On The Control Strategy Of Active Power Filter Based On Resonance Technology

Nowadays, the widely usage of power electronic devices brings serious harmonic pollution and reactive power losses into the public grid. Harmonic current and reactive current will harm other equipments which are worked in the public power grid. Moreover, it will also harm the operation of power grid. Active power filter(APF) is widely used in the harmonic suppression and reactive power compensation area. In order to make APF compensate the harmonic and reactive current well, an APF with PR control strategy is designed, it will improve the compensation precision and reduce the digital processor computational complexity.Firstly, the detection method of harmonic and reactive current is analyzed. Based on the theory of instantaneous reactive power, we chose the ip-iq method that can detect harmonic and reactive current. A double closed-loop active power filter is set up, it can compensate the reactive current component correctly, but its harmonic composation should be improved.Secondly, an APF with PR is choosen. The advantage of PR technology is that it can track the specific frequency ac input signals accurately. And the strategy of APF with PR can compensate the harmonic current component effectively. In the electric power grid voltage can fluctuate frequently in ±0.5 Hz, so it would cause ±0.5n Hz frequency wave of the harmonic. The adaptive frequency PR is used to improve the adaptation of frequency. Meanwhile, the difficult problems of PR are analyzed such as parameter setting, phase compensation and discretization, and achieve the high performance of harmonic compensation in the APF, so that the harmonic compensation of APF in engineering applications has a better performance.Thirdly, the resonant PLL is used to get the accurate fundamental frequency of the grid voltage. The accuracy of the frequent adaptive PR should be assured so that it can perform well. When the public power grid voltage is not the ideal sine wave, the fundamental component, negative sequence and harmonic component can be separated to extract the fundamental component and fundamental frequency accurately.At last, the experiment platform using DSP TMS320F28335 is built to control the active power filter. And the system and the hardware must be designed in detail. Meanwhile, the feasibility of APF with PR should be tested to the reactive compensation and harmonic current. And we also have test the correctness of PLL with co-vibrating type for fundamental wave frequency.