Multi-pulse Rectifier System Based On Boost PFC Type Inter-phase Reactor

Three-phase ac-dc converters have been widely used in high-power situations such as electro-chemical processes and converters for renewable energy conversion systems and aerospace fields. However, because of the time-varying and nonlinear characteristics, they could cause a large number of current harmonics to the power grid, resulting of serious problems. The multi-pulse rectifiers are developed for improving power quality to reduce both harmonics of input current at ac side and ripples of output voltage at dc side. Now multi-pulse rectifiers have become an effective method to solve harmonic pollution of three phase ac-dc rectifiers in high power situation. In order to further improve the harmonic suppression capacity of the traditional multi-pulse rectifiers, this paper researches the traditional 12-pulse rectifier and then proposed a novel low harmonic rectifier system based on APIR(Active Inter-Phase Reactor) with interleaved Boost PFC circuit, which could effectively reduce input current harmonics while achievin g harmonics energy recycling.In order to analysis the effect of the AIPR primary current to the harmonic suppression, we analyzed the AC and DC side current characteristics of the 12-pulse rectifier system by using switching function method. Obtain the ci rcuit current relationship among the input side, the AIPR primary side and the output dc side. The results show that to control the AIPR secondary current to meet the requirements on amplitude and phase is the key to reduce harmonics. Also, the influences to the system voltage characteristics and the capacity of main magnetic components have been analyzed. According to the comparative results with the conventional rectifier, the features of the novel system are identified.The primary current of AIPR should be generated by the secondary side circuit. Combined with the desired working conditions and energy flow of the secondary circuit, we proposed a new way of using the interleaved Boost PFC circuit as the secondary circuit. This type Active Inter-Phase Reactor can meet the demand of the current control and improve system harmonic suppression effect; at the same time, the harmonic energy is fed to the 12-pulse rectifier system output load side to achieve re-use of the harmonic energy.The interleaved Boost PFC at secondary side of AIPR has been specifically designed, including the Boost inductance, the output capacitor and other key circuit parameters. According to the system control requirements and the advantages of digital control, we designed a digital control system based on TMS320F28027, in order to control the input current and to realize the system over-current, over-voltage protection at the same time.Simulation has been completed with the help of MATLAB/SIMULINK, also a 9k W prototype based on a digital control system has been completed. The experimental results show that the input current THD can be reduced to 1/4 of the original value by adding the Boost PFC converter, whose power rating is only 2% of the 12-pulse system’s capacity. the effectiveness of the designed system for harmonic suppression has been verified, especially for high power conditions.