An Energy-Feedback Six-Phase Rectifier Based On Active Harmonic Suppression Technology On Dc Link

With the development of power electronics, diode rectifiers are applied widely in various fields. But due to the uncontrollable characteristic of diodes, the rectifying device injects large harmonic currents into power grid and results in serious problems in the power system and customers. In high-power situation, multi-pulse rectification is one of the most effective measures in improving the performance of rectifiers; however, the higher harmonics of the input currents still cause serious harmonic pollution at the power grid. In order to eliminate more input current harmonics of the three-phase diode rectifiers when the load is varied, and to keep the system's high working efficiency, this paper combines the multi-pulse rectifier technology with the harmonic suppression technology on DC link of rectifiers and designs an energy-feedback six-phase rectifier based on active harmonic suppression technology.In order to ensure the elimination of 3th, 5th, 7th harmonics in input currents and to decrease the volum and cost of the non-isolation high-power rectifier, the 12-pulse rectifier which is based on the Sewan-Choi autotransformer is selected as the basic circuit. According to familiar points of the 12-pulse rectifier and designed rectifying device, the harmonic-suppresion principle and voltage characteristics of the 12-pulse rectifier are analyzed. In addition, working principles of the Zero-Sequence Blocking Transformer and Interphae Reactor are discussed. At last, the equivalent capacity of magnetic components is calculated. All of the above work is the basis of the designed rectifier.The performance of the active harmonic suppressor is the decisive factor of influencing the harmonic-suppresion effect and working efficiency. The mathematic relationship of input current, load current and the active harmonic suppressor's input current is deduced and the fourier-series method is used to analyze the harmonic-suppresion principle of the designed rectifier. The conclusion is obtained that as long as the waveform of the active harmonic suppressor's current is the specific triangular wave, input currents of the designed rectifier could be nearly sinusoidal and then more harmonic currents of the diode rectifier are eliminated.By analyzing the power status of the active inter-phase transformer, this paper can determine that the active harmonic suppressor is actually a single-phase high-frequency PWM rectifier and it feedbacks harmonic power to DC link. Acoording to the above conclusion, the main circuit, driving circuit and control circuit of the active harmonic suppressor are designed. Finally, a 3 kW energy-feedback six-phase rectifier based on active harmonic suppression technology is developed and the experimental system is set up. It is proved by the results of simulation and experiment for the system that the harmonic currents can be eliminated effectively and the working efficiency is high.