Research On The Three/Twelve-Phase Rectifier Based On Rotating Magnetic Field And Its Operational Characteristic Tests

With development of the power electronic technology and social demand driven, The widespread use of high-efficiency and energy-saving loads becomes inevitable. But in the power grid's fixed frequency and voltage,these new loads cann't always work in the best state and get the highest efficiency and the best performance. The typical characteristic of these new loads is converting Ac power to smooth DC power by using the rectifier technology and then converting the DC power to their suitable frequency and value of voltage. The remarkable characteristic of the traditional AC power system is to tansfer the ac power efficiehtly only in the condition of three-phase symmetric sinusoidal case. The wide use of rectifying devices is thought to bring serious harmonic pollution for the power sysytem and severe challenges to its security, stable operation. To solve these problems and meet the challenges,The usual practice of current compensation gives priority to the idea of "who pollution, who responsible for ",that is to formulate relevant regulations and harmonic standards, requiring for each user to improve technology respectively for their own nonlinear equipments in order to make them consume only sinusoidal power. This paper attemps to solve these problem actively through technical improvement of the power transmission and distribution system, The basic method is to develop a twelve-phase rectifier device based on the rotating magnetic field, which isolating harmonics in an electromagnetic way by using the harmonic own energy. The electromagnetic method for harmonic filtering belongs to the passive filter ways.Its structure is simple,and it can supply stable DC power and have low THD of AC input current without additional other devices. That means it can work reliably and efficiently on highly power occasion. With it, we can supply steady DC power for all users in all fields and solve the harmonic problem uniformly in the power transmission and distribution system.This paper first discusses the technical features of the present harmonic suppression means for rectifier equipments and points out that they are not an effective way to suppress the current sharp pulse peak of the retifier. So we should have to look for other new ways.Based on the analysis of the passive filtering ways such as LC filter,multi-pulse rectifier,A new three phase rectifier with a series reactor based on rotating magnetic field is put forward.The principle of space motion magnetic field generated by distortion current is studied in order to show that the magnetic way for harmonics filter is feasibl and easy. Then we apply the magnetic way to a transformer form and get a novel twelve-phase rectifier. The depth analysis of the characteristics of periodic movement in space of its magnetic field is done.Under the reaction of the movement of the rotating magnetic field, Distorted electromagnetic power can be transferred between phases,so the power plant could generate only sinusoidal power to balance the distortion power needed by the nonlinear loads.Based on the above analysis, the paper developed a twelve-phase rectifier.The data gained by physical experiment shows that the new rectifier can meet its firstly design indexes which are the indexes of 5% of THD in AC current and 5% of ripple coefficient in DC voltage fluctuation.In addition,it has electromagnetic speed to respond dynamicly to suppress the harmonics. Its application of engineering is very extensive and can not only be used for the power transmission and distribution system to supply steady DC power but also serve as an highly efficient power converter for DC electric traction system, HVDC, etc.