Harmonic Detection And Restraint Based On Sliding-Window Iterative Algorithm Of DFT

In recent years, with the development of power electronics technology, there are more and more nonlinear loads and devices in the electricity system. The nonlinear loads and devices fill lots of inevitably generates non-sinusoidal shape and harmonic into the grid。Harmonic pollution has become a hazard problem to grid, it has great impact on power system safe, reliable and economic operation., while electrical equipment of users will also affect。Currently, an important trend to solve the problem of harmonic is to use APF (Active Power Filter). It needs to detect load harmonic current from the compensation object, then APF generates a harmonic current with the same size, but opposite current to inject network, so the grid contains only fundamental current.The dynamic compensation of APF demands that distortion current in grid should be accurately and real-time detected, then generate harmonic reference instruction current of Active Power Filter. For solving the problems of improved DFT (Discrete Fourier Transform) algorithm in the non-synchronized sampling,。This paper presents a sliding window iterative DFT algorithm based on adaptive sampling. The method can reduce errors caused by the non-synchronous sampling by adaptive sampling. The simulation results show that the algorithm can effectively detect the real-time harmonic reference instruction current and has good real-time, tracing and so on.Based on the above algorithm, a three-phase shunt active power filter is designed, and harmonic reference instruction current is generated by adaptive sampling sliding window DFT algorithm, then compensation current circuit is designed.