Research On A Novel Multi-tap Inter-phase Reactor For Power Frequency Rectification

As the connector of most industrial electronic equipment and power grid,power frequency rectifiers are widely used in industrial occasions.However,in high power applications,due to the non-linearity of the device for rectification,the rectifier can inject a large amount of current harmonics into the grid.The conventional multi-pulse rectification technology can suppress the input current harmonics on the AC side to a certain extent,but in some occasions its harmonic content cannot meet the requirements.The AC side harmonic suppression technology of the DC side current modulation is an improvement on the DC side of the conventional multi-pulse rectifier,which can further reduce the i nput current harmonic content of the AC side,and its additional cost is low and the circuit structure is simple.This paper summarizes the harmonic suppression technology based on reactors with taps or rectifier circuit on the secondary side,and proposes a novel multi-tap inter-phase reactor that modulates the output current on the DC side of the rectifier to suppress the harmonics of the input current on the AC side.The multi-pulse rectifier based on the novel three-tap inter-phase reactor uses an auto-transformer for phase-shifting and a double-bridge parallel rectification structure.According to the relationship between the input and output currents of the auto-transformer and the switch function of the rectifier bridge,the relationship between the input current on the AC side and the output current of the two rectifier bridges is deduced.The circuit structure of the inter-phase reactor is discussed,and the type of the circuit on the secondary side can be selected depending on the application.The operating modes of the novel three-tap inter-phase reactor and the output currents of the two rectifier bridges under each mode are analyzed.Based on the relationship between the output currents of the two rectifier bridges and the input current on the AC side,the harmonic suppression principle of the inter-phase reactor is obtained.In order to deeply analyze the operating characteristics of the inter-phase reactor to minimize the input current harmonic content of the AC side,an optimized design method for the inter-phase reactor is established.According to the load voltage expression of the inter-phase reactor operating in each mode,the necessary conditions for the operation of the rectifier circuit on the secondary side are deduced.The optimal parameters of the inter-phase reactor with the lowest input current harmonic content are calculated and the correctness of the analysis of operating principle and optimized design is verified by simulation.In this paper,the novel multi-tap inter-phase reactor is extended to four-tap and five-tap structures.The optimal parameters are calculated and simulated,and the influence of the number of taps on the primary side on the input current harmonic on the AC side is discussed.By comparing the advantages and disadvantages of the inter-phase reactor with different number of taps in terms of harmonic suppression and control difficulty,the novel three-tap and four-tap inter-phase reactor that are more suitable for practical applications are determined as experiment al solutions.In addition,this paper also proposes a fully-controlled multi-tap inter-phase reactor capable of reducing losses in high-current applications.By designing the system structure and control circuit,a multi-pulse rectification experimental platform based on the novel multi-tap inter-phase reactor is built.The validity of the input current harmonic suppression of the novel three-tap and four-tap inter-phase reactor and the correctness of the theoretical calculations of the optimal parameters are verified respectively,and the load characteristics are studied,which provided a reference for the practical application of the n ovel multi-tap inter-phase reactor.