Study On Active Power Filter Of Improved Unit Power Factor Method

With the progress of technology, more and more advanced devices are put into use in power system. Most of these devices are non-linear loads and lead to the harmonic current, so it is necessary to take effective measures to control power system harmonics. Active power filter is the most effective device for harmonic suppression and has been widely used in practice. This paper focus on the unit power factor harmonic current detection and put forward improvement method.The shunt APF was chosen as the research object according to the study status quo. For the harmonic current detection methods, advantages and disadvantages of them are compared. According to the comparison results, unit power factor method was selected to detect the harmonic current. However, grid voltage distortion can affect this method seriously, so an improvement method was proposed by using adaptive filter to eliminate harmonic voltage. The algorithm of adaptive filter was least mean square, a new variable step length algorithm was also put forward, which is use relative signal error to calculate step length factor. The simulation model of the new algorithm was built by using Matlab, steady-state error of two methods were compared, simulation results showed that new method can eliminate harmonic voltage more effectively. The simulation model of APF was also built, simulation results verified that the new method can achieve grid current compensation under the condition of grid voltage distortion.On the basis of simulation, hardware experiment device was built by using digital signal processor, and software and hardware design were completed. Hardware design mainly involves the design of main circuit, drive circuit, and sampling circuit, the calculation of the component parameters. Software design mainly involves the whole program process and harmonic detection program process.