Research And Implementation Of Control Strategy In Active Power Filter

Along with the wide application of nonlinear loads in power system, the harmonic pollution caused by the harmonics in power system has being become more and more serious. The harm of harmonic pollution is huge. It can cause the low efficiency of electric energy production, transmission and utilization. It can make the electrical equipment overheating and result in vibration and noise. It can accelerate the insulation aging and shorten the service life. When serious, it would cause failure or burning of electrical equipment. Therefore, the control of power harmonic has become a key issue in the field of electric power industry. As a kind of power electronic device, which can effectively control the reactive power of harmonics and compensate reactive power, active power filter has been a new hot spot in the field of power quality for its wide application prospects and good economic benefits. In this thesis, the key technology issues of active power filter have been studied in detail, and a new control strategy has been proposed to improve the accuracy of harmonic detection, which has achieved good compensation effect.Firstly,the basic concept of harmonic generation and its harm have been introduced. The advantages and disadvantages of the main measures of harmonic suppression have been analyzed and the advantage of active power filter in harmonic control has been clearly stated in this paper. Secondly, against the shunt active power filter, which is most widely used in industrial applications, the key technology has been further studied, including the detection of harmonic signal, the tracking of compensation current and the stability of the DC side voltage. Based on the comparison of several control methods, in order to improve the harmonic suppression performance of active power filter effectively, the detection of harmonic currents using the Fourier transform fast(Fourier Transform Fast, FFT) algorithm, the tracking and compensating current using the non-fixed frequency hysteretic space vector pulse width modulation(Space Vector Pulse Width Modulation, SVPWM) algorithm, and the control of the DC side voltage using the closed-loop control have been adapted in this thesis. Then, by Matlab/Simulink software, a large number of simulation experiments have been carried out to verify the above control technology and strategy. All of the simulation results have shown that the active power filter based on the control strategy of this paper is effective obviously to compensate the harmonic of the power grid very well.Finally, based on the theoretical analysis and simulation experiment, an experimental prototype of active power filter has been built in this thesis. Then the control software design of the system has been completed. Based on the prototype, the function test and grid connected experiment of the active power filter have been finished. The experimental results have verified the correctness and practicability of the proposed control strategy and the control software design there, which have laid a good technical foundation for the follow-up research work of the related topics.