Research On Harmonic Current Detecting Method And Control System Of Active Power Filter

Along with the development of power electronics technology, as well as improved requirement of power quality, harmonic suppression and reactive power compensation has got more attention. As a dynamic compensation equipment, active power filter has much larger advantages than other compensation methods, such as rapid-reflect,better compensation and the ability in dynamic compensation..The background, development and future prospect of APF, the classifications and topology structure of APF are described in detail and this paper mainly deals with the harmonic wave detection and the control strategy of the inverter in APF. An intelligent harmonic wave detection arithmetic is adopted.These strategies are proven to be effective and beneficial.First of all, LMS and LMF algorithm are discussed. Based on the analysis of universal expression given for the available harmonic current detecting methods, an improved harmonic current detecting method using LMS/LMF algorithm was proposed. The parameters of iteration step were determined to ensure that the selection of parameters had no adverse effect on the algorithm convergence. A variable step size LMS/LMF algorithm was applied to update weights, and the step size was adjusted by means of the normalized autocorrelation estimation of two error signal. Also the simulation results have verified the effectiveness and practicability of the new algorithm in the situations of the 3-phase symmetrical current and the 3-phase dissymmetrical current system.Secondly, the shunt voltage APF system is simulated. Two methods of tracking command harmonic current are introduced—hysteresis current control method and a linear feedback approach based on inverse system method. Aiming at the nonlinear identity of the mathematic model of the active power filter in d - q synchronous reference frame, a pseudo-linear model is given based on the inverse system method. A linear quadratic controller is designed to meet some performance index in terms of the pseudo-linear system. The whole simulating system is realized by means of detecting the current of the load, the simulation results show that dynamic compensation can be achieved using the two methods in the situation of 3-phase symmetrical circuit.Finally, on the basis of theoretical analysis and simulated research, the shunt active power filter based on TMS320F2812 has been designed, meanwhile the software and hardware have been introduced in detail. Initial lab research on the shunt active power filter has been done, the results show that the current detection method and the control strategy can compensate harmonic current well.