Study Of Dc Magnetic Bias And Harmonic Current Compensation Equipment's Key Issues

With the development and progress of the science and technology, the application for a lot of power electronic equipment and other perceptual load caused great harmonic pollution in recent years. At the same time, the more advanced the electric equipments is, the high power quality is demanded. The sharp contradiction has greatly restricted the pace of the economic development. The harmonic content has become the important power index the same as voltage and frequency. Meanwhile, as one of the rapid development and transmission technology, HVDC transmission technology will have great interference on the power transformer nearby when in the state of single earth loop. The interference mainly reflects in neutral potential drift, which will make the power transformer have the phenomenon of DC magnetic bias, as a result, caused very serious problems: the exciter current distortion, loss increase, and noise rise, and so on. The request of the intelligent power is put forward during the National Twelfth Five-Year Plan Period, in order to response the call of countries, this paper designs a device that can determine to do harmonic compensation or transformer DC magnetic bias compensation in light of the power grid state. This paper puts forward an active power filter with DC magnetic bias compensation function (referred to as the APF), which is based on the two pollution problems, proposing intelligent power requirements and be harmful to the safe and stable operation of the power system.The paper mainly introduces the causes of formation and hazards of the harmonic and DC magnetic bias, and then puts forward an improved method of harmonic detection that can detect harmonics of the power grid more quickly and accurately. At the same time, the design of multiple orders'Chebyshev Digital Filter provides reliable guarantee for real-time compensation harmonic current. The Filter has many advantages, such as: the separation realization of the base wave current, negative sequence, zero sequence and harmonic current, higher calculation speed, lower quantity of DSP. After analyzing the topological structure of APF in the market, and in the light of this topic, A suitable structure is selected and detailed derivation is given with the mathematical model. For DC magnetic bias compensation, the mathematical model of the controlled rectifier is deducted when the experiment device working in DC magnetic bias compensation state. The hardware and software is design and the general design principle is put forward based on the voltage level and capacity of the experiment device. What's more, the detailed instruction is given in accordance with the basis of selection of the original parameters. In the end, each element's specific parameters and the overall design project are given. Besides that, the simulation is set up by MATLAB /SIMULINK to test the experiment device in the effects of the harmonic treatment and DC magnetic bias compensation. Finally, according to the difficulty and shortages of the experimental device, the next step of work prospect is put forward.