| Multi-pulse rectifier system is widely used in practice as an interface between AC grid and power electronics.The common parallel-type 12-pulse rectifier system has the advantages of simple structure and high efficiency.However,its harmonic reduction capability is limited.To this end,three harmonic reduction methods based on passive current injection type inter-phase converters in the DC side of the rectifier system with the premise of playing the inherent advantages of the 12-pulse rectifier system,which significantly improves the power quality of the parallel-type multi-pulse rectifier system.In order to reduce the harmonic content of the grid-side current of a 12-pulse rectifier system,a harmonic reduction method based on a single passive current injection type with secondary-winding full-bridge rectifier inter-phase converter(SFRIC)is proposed.The operating modes of the method are analyzed,and the design and optimization of the inter-phase converter are aimed at minimizing the total harmonic distortion(THD)of the grid-side current.The impact of the method on the capacity of the rectifier system is analyzed,and the additional conduction loss of the method is calculated.The theoretical study and simulation results show that the method can multiply the pulse wave number of the rectifier system and the grid-side current harmonics are effectively suppressed.A single passive current injection type double-tap inter-phase converters(DICs)with low loss characteristics is proposed to address the problem that the full-bridge rectifier in SFRIC is connected in series with the load circuit,resulting in large conduction losses.The necessary operating conditions of DICs are derived,their three operating modes are analyzed,and the parameters of DICs are optimized with the objective of minimizing the THD of the grid-side current;the capacity and additional conduction loss of the rectifier system are analyzed and calculated.The theoretical study and simulation results show that the method not only has the same harmonic reduction effect as the SFRIC method,but also can effectively reduce the conduction loss and is suitable for high-power applications.To further improve the harmonic reduction capability of the 12-pulse rectifier system and achieve better input and output power quality,a harmonic reduction method based on a dual passive four-tap inter-phase converter(PFIC)is proposed.The four operating modes of the PFIC are analyzed,and the internal and external tap turn ratios of the PFIC are optimized with the objective of maximizing the reduction of grid-side current THD.The capacity and additional conduction losses of the rectifier system are analyzed and calculated after adopting this method.The theoretical results show that the rectifier system with higher power density and lower cost of harmonic reduction after adopting this method is a simple structure and cost-effective harmonic reduction method.The simulation verifies the correctness of the theoretical analysis.The 10 k W rectifier system is used as an example for quorum analysis,and the power loss rate and efficiency of the three rectifier systems are calculated under the same parameter conditions.And the three rectifier systems are compared and analyzed in terms of power quality and efficiency,and the results obtained will provide theoretical support for the rational application of the three rectifier systems.Finally,the influence of load change on the power quality of rectifier system is explored,and the adaptability of different loads is evaluated. |
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