Novel Multilevel Converter for Variable Speed Medium Voltage Switched Reluctance Motor Drives

A novel multilevel converter for switched reluctance motor (SRM) drives that is scalable to high voltage and power is proposed. The proposed converter is called the chopper cell (CCC) converter. The converter is naturally capable of variable speed, four-quadrant operation. The CCC converter has a modular construction and offers high reliability; it also has provision for including redundant modules. The CCC converter mainly targets high speed multi-megawatt that typically operate at the medium voltage level which extends from 1 kV all the way up tp 30 kV or more. Examples of potential applications are very high power pumps and compressors in the oil and gas industry. However, due to its multilevel capability and use of low voltage cells, the CCC converter also offers high efficiency and improved performance. Therefore, the proposed converter may also find use in sub-megawatt SRM drive applications that require high efficiency and/or high performance. And by virtue of its reliability, the converter may also be used in critical sub-megawatt SRM drive applications that require very high uptime.


The invention includes the algorithms necessary to successfully control the SRM. Particularly, a novel cell capacitor voltage balancing and control algorithm, without which the drive cannot operate, is proposed. Also a startup algorithm that limits startup current and switching losses, and that ensures cell capacitor voltages remain controlled at startup, is proposed. Finally, a complete scheme that operates the CCM SRM converter drive at a high efficiency is also proposed.


A detailed simulation model was developed and used to validate the converter's operation and all of the above-mentioned control techniques. Experimental validation is also planned.

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Mike Miller
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Virginia Tech Intellectual Properties, Inc.
(540) 443-9228
Ahmed Shehada