The Realization Of Current Average Harmonic Detecting Approach Based On DSP And Its Application To Active Power Filter

A general description of the development of harmonic elimination technique around the world, principle and structure of Active Power Filter and theory of three-phase instantaneous reactive power is given in this thesis at first. The harmonic detecting ip-ig method based on theory of instantaneous reactive power and modified i -i method called current moving average detecting one are researched as emphases. At groundwork of analysis to the principle of current moving average the harmonic detecting scheme based this theory is presented and the diagrams of actualization is put forward.Then simulation mode of harmonic detecting method based on moving average principle is given in SIMULINK environment of MATLAB6.1 software. Simulation research to this harmonic detecting scheme is done and its results are contrasted with those got by ip- iq method using conventional filters. The result not only indicate that the simulation means and the simulation mode implemented are efficient but also prove that moving average method can produce a faster dynamic response than that done by conventional filter method.At the basis of simulation, a digital realization scheme of moving average method applied to LF2407A DSP chip as a CPU is brought forward. Furthermore, a device of three-phase shunt APF based DSP for testing is made. Software and hardware of this device are designed. Hardware circuits are constructed and system software are written using DSP compile language. All software are debugged under CC'C2000 software development system. Also a control strategy to realize synchronizing sampling is employed using software PLL.Finally the digital APF device is tested. The experiment result indicatesthat moving average method combined with software PLL control strategy can detect harmonic current true and effectively. The experimental device of digital APF adopting modified detecting method can eliminate harmonics effectively caused by nonlinear load.