Algorithm Resisting Current Harmonic Disturb In Three-Phase Power Systems And DSP Implementation

With the rapid development of the power electronics, more and more power electronic equipments have been used in most fields. In these equipments there are most nonlinear loads. This results to the serious pollution in power net. So the real-time harmonic compensation becomes more and more important. All kinds of electrical and electronic devices for harmonics elimination come into use. Among of them, the Active Power Filter (APF) is most representative.Firstly, the basic concept and analysis method of harmonic for electric power system are presented in this thesis. Then the necessity of harmonics elimination is analyzed. At last the classes, basic work theory and system structure of APF are discussed.Secondly, the basic theory of instantaneous reactive power is analyzed. And at same time p-q and i_p-i_q harmonics detecting algorithms based on the theory are studied. And then the characteristic of these algorithms are analyzed. The key technique of these algorithms is digital Low-Pass Filter (LPF). Through accurate analysis and systemic compare, parameters and type of the LPF are given. Simulation results verify the feasibility of the proposed algorithm. In order to demonstrate the validity of the proposed algorithm further, the algorithm is tested in ICETEK-LF2407A experiment board. Considering possible unsteadiness of the filter system due to the limited word length of DSP TMS320LF2407A in the ICETEK-LF2407A experiment board, a new method by extending effectual word length is put forward. And the flow chart and software for the experiment board are given.Finally, the control method of APF is discussed. The APF requires that the change of command current signal is tracked compensation current which is generated its circuit in real time. So the Pulse-Width Modulation (PWM) control mode of tracking style is used generally current control circuit. The main PWM control modes are hysteresis compare mode and triangular-wave compare mode. The triangular-wave compare is conveniently implemented with the PWM output in TMS320LF2407 experiment board, so PWM output is implemented with the triangular-wave compare mode in this thesis.