Research Of18-pulse Rectifier Based On Autotransformer

In the application of modern power electronics technology, the nonlinear nature of rectifier causes distortion of input line currents, forming harmonic currents which pour into power grid, thus it brings pollution into power grid and does harm to electrical devices. In high power applications, the damage is especially serious. So the most effective way of reducing the harmonic pollution is to better input current waveform of rectifier.The switching power supply used in radar system rectifies the front-end input by employing a diode-based uncontrolled bridge rectifier. The uncontrolled rectifying circuit has obvious nonlinearity. A large number of switching power supplies are connected directly to power grid in radar system, so without effective measures damages would be made due to harmonic pollution from severe distortion of input line currents, such as hidden danger of power electronics and electromagnetic compatibility decline, etc.National Military Standards specify that the root mean square value of total harmonic currents for aircraft AC electrical equipment does not exceed10%effective value of fundamental currents. In small and medium power applications, we can take PFC measures to effectively alleviate harmonic pollution. However, the higher the power is, the more serious the problem is that uncontrolled rectifier device generates harmonic currents. Therefore, PFC technology has been unable to meet the system requirements.The multi-pulse rectifier technology is to use electrical connection method of transformer windings to achieve phase shifting, and to increase pulse waves of the rectifier device. By applying the technology, some specific harmonic interference in input currents is eliminated or inhibited, which decreases harmonic pollution in the grid. Thereby, the quality of power supply improves and it satisfies the system requirements.This dissertation beginning with design principle of the phase-shifting transformer, introduces varieties of implementation of the multi-phase rectifier. Combined with projects, it elaborates comparative analysis and detailed design for18pulse autotransformer concerning radar system demands. Through the application and verification in radar system, the rectifier device is proved to work stably in harsh environment, and satisfy the needs of radar system for enhancing power factor, reducing total harmonic distortion, as well as improving the quality of power waveform to achieve design purposes.