Development of Multi-Pulse Rectifier System Based on Multi-phase Conversion and Phase Displacement Technique for Medium Voltage Motor Drive

This paper presents a sixty-pulse rectifier for medium voltage drive applications. At all load situations, it is meant to fully optimize performance of a medium-voltage induction motor drive system across whole speed range, from standstill to rated speed. The phase displacement and multi-phase conversion techniques are used in construction of suggested multi-pulse rectifier system. There are three sets of multi-winding transformers in proposed multi-pulse rectifier setup, where primary of these multi winding transformer is designed for adopting three-phase supply from grid while secondary windings are designed for delivering five-phase power supply. Here, modular unit of transformer operates as twenty-pulse rectifier while entire system operates as sixty-pulse rectifier because primary winding is designed with phase displacement technique. Apart from this, a hybrid seven-level inverter is designed and developed to overcome the issue at drive end of medium voltage drive system. Major advantages of presented power converter include simple structure, modular structure, high reliability, and low-harmonic input/output waveforms, without a need of filter element. Practicality of system is confirmed by simulation results using a 4.16 kV, 1250 hp induction motor drive. The viability of innovative circuit and related control method is also confirmed by experiments conducted on a downscaled prototype of 415 V, 7.5 kW.