| With the rapid development of power electronics technology,more a nd more high-power power converters are being applied in industria l fields such as motor drive,aviation power supply,electrolytic electroplating,and metal smelting.Due to the advantages of simple structure,high reliability,and low cost,12-pulse rectifiers are often widely used as interface circuits for high-power power converters to obtain energy from the power grid.However,when using a 12-pulse rectifier alone,there is still a large amount of(12k±1)harmonics in the input current,and the THD of the input current can reach more than 10%,which cannot meet the requirements of harmonic standards such as IEEE-519.In order to significantly suppress the input current harmonics of the rectifier without increasing the volume,weight,and cost of the 12-pulse rectifier,this paper focuses on the DC side harmonic supp ression of the series-connected 12-pulse rectifier based on the Zig-zag phase-shifting transformer.In order to clarify the influence of DC side circulating current on the input current THD and output voltage ripple coefficient of the series-connected 12-pulse rectifier,the influence of circulating current equivalent coefficient on the input current THD and output voltage ripple coefficient of the three-phase rectifier bridge was analyzed when the output current was continuous and intermittent.The circulating current equivalent coefficient with the lowest input current THD and output voltage ripple coefficient was obtained,respectively.Based on the above analysis,the expressions of input current and output voltage corresponding to the minimum input current THD and output voltage ripple coefficient are given.Subsequently,based on the input and output characteristics of the rectifier under intermittent conditions,a passive circulating current inj ection scheme was proposed,and a 24-pulse rectifier based on passive current injection was obtained.Its working principle and pulse multiplication mechanism were analyzed.Afterwards,the manifestation of DC side circulating current on the grid side when the output current of the rectifier bridge is continuous was analyzed,and the mechanism of suppressing grid side harmonics by DC side circulating current was provided.The influence of the energy flow direction of the DC side circulating current and the circulating current parameters on the harmonic suppression performance under continuous conditions is analyzed,and the main circuit topology and control strategy of the single-phase Vienna rectifier realizing circulating current injection are given.Analyzed the capacity of magnetic devices in the rectifier and the voltage and current stress of diodes in the rectifier bridge,clarified the impact of circulating current on the capacity of magnetic devices in the rectifier,and provided reference for the design of the rectifier.The control circuit and drive circuit of single-phase Vienna rectifier are designed.The experiment verifies the harmonic suppression effect of the seriesconnected 12-pulse rectifier with single-phase VIENNA rectifier circuit.The TH D of input current can be reduced from 11.5% to 1.5% under rated conditions.Subsequently,experiments were conducted to analyze the harmonic suppression performance of the rectifier system under load and input voltage fluctuations as well as three-phase imbalance conditions.The experimental results showed that the proposed scheme still has good harmonic suppression effect under load and input voltage fluctuations and imbalance conditions. |
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