Hybrid Inter-Phase Converter For Multi-Pulse Rectification

As the interface between many power electronic devices and the power grid,the power frequency rectifier has strong nonlinear and time-varying characteristics that causes the power frequency rectifier to cause varying degrees of harmonic pollution to the power grid,especially for high power rectifiers,distortions will not be ignored.Multi-pulse rectifier is one of the important ways to solve the harmonic pollution of rectifier.The harmonic suppression effect of the multi-pulse rectifier circuit using the passive harmonic suppression method on the DC side is limited,while the active harmonic suppression method on the DC side has a significant harmonic suppression effect,but it does not improve the output voltage rippl e characteristics and its active part capacity and peak current are large.In this paper,the active method and the passive method are combined,the active current contro l link is added on the passive converter,and the hybrid inter-phase converter is studied to give full play to the advantages of passive conversion and active conversion.The switching function method was used to analyze the current relationship between the AC and DC sides of the parallel 12-pulse rectifier.With the goal of no harmonics in the grid-side input current,the optimal circulating current expression to be satisfied by the primary side of the inter-phase reactor under the condition of large inductance was analyzed.And the simulation verifies its harmonic suppression ability and the voltage and current characteristics of the system.The modulation effect of the primary double-tap passive inter-phase reactor on the DC side output current of the rectifier is analyzed,and the numerical relationship between the tap position of the double-tap passive inter-phase converter and the grid-side current THD value is obtained and the optimal value of the tap position are obtained.On this basis,it made a foundation for the research of hybrid inter-phase converter.The effects on input current harmonics,DC output voltage ripple,peak current and capacity of the secondary circuit when the passive circul ating current and the compensation circulating current of the hybrid inter-phase converter are synthesized in different ratios are obtained.Obtained the range of the ratio of circulating current synthesis when the circuit operating characteristics are goo d.The advantages of the hybrid harmonic suppression method in current harmonic control,output voltage quality and active link capacity are clearly defined.Among the two passive interphase reactors with double taps on the primary side and the rectifier on the secondary side,a more suitable double-tap type was selected as the further research object.The primary tap change ratio and active compensation current of the hybrid interphase converter were studied to optimize the design.The design of hardware and control software for the active auxiliary circuit of the secondary side of the hybrid balance converter is given.The designed multi-pulse rectification system using hybrid inter-phase converter is simulated and analyzed,and the influence of the leakage inductance of its magnetic device on the circulating current modulation is considered.The load adaptability of the circuit under different load types and load parameters is studied,the harmonic suppression effect of the system for common load types is analyzed,and the filter parameter selection method for the most common RLC load in the industry is given.