A Low Harmonic Twelve-Pulse Rectifier Based On Active Inter-Phase Reactor

High power rectifiers have been widely used in a number of industrial systems such as adjustable speed drives, electro-chemical processes and converters for renewable energy conversion systems. But the rectifiers genenate a large number of harmonic to the power source because of the nonlinear and time-varying characteristics. Multi-pulse rectifier technique is an effective method to solve harmonic pollution of the high power rectifier. In order to improve harmonic suppression efficiency of multi-pulse rectifier further, this paper researches a low harmonic 12-pulse rectifier based on Active Inter-Phase Reactor (AIPR) which harmonic is suppressed by current modulation on the DC side. It can be applied for the systems which don't need to be isolated between AC and DC sides.In order to obtain the principle that harmonic of input current can be suppressed by circulating current of DC side, this paper analyzes the relationship between input current, output current and circulating current of DC side by switching function method. The amplitude and phase of the triangular circulating current are identified when the harmonic is suppressed most greatly. This paper also analyzes the output voltage and the capacity of the main parts. According to the comparative results with the conventional rectifier, the salient features of system are identified.Load adaptability of the system is analyzed in dedail. For LR type and LCR type of load which are widely used in industrial applications, this paper analyzes the influence of output current ripple on input current harmonic and gets the relationship between THD of input current and load parameters. In order to ensure harmonic suppression efficiency for LCR type of load, this paper also gives a kind of parameter design method for LC filter. The method provides some foundation for application of the system.The circulating current should be generated by current modulation of the auxiliary circuit at secondary side of AIPR. According to energy flow derection and other conditions of the auxiliary circuit, one method that using a series circuit as auxiliary circuit which is composed by a single phase PWM rectifier and a DC/DC converter is proposed. This method can improve versatility and adaptability of the system.The rectifier system which auxiliary circuit is composed by a PWM rectifier and a boost converter is designed. And a 6.4kW experimental system is developed based on the design. Experimental results are analyzed in detail to verify harmonic suppression efficiency and other features of the system. 12-pulse rectifier based on AIPR has significant harmonic suppression efficiency. The auxiliary circuit has little capacity and doesn't consume additional energy. Theoretical and experimental analysis shows the application value in high power rectifier.