Investigations in the Modeling and Control of a Medium-Voltage Hybrid Inverter System That Uses a Low-Voltage/Low-Power Rated Auxiliary Current Source Inverter

Abstract

Investigations in the modelling and control of a medium voltage hybrid inverter system that uses a low voltage /low power rated auxiliary current source inverter. IEEE Journal of Emerging and Selected Topics in Power Electronics, 4 (1). pp. 126-140. ISSN 2168-6785 Access from the University of Nottingham repository: http://eprints.nottingham.ac.uk/32220/1/Investigations%20in%20the%20Modelling%20and %20Control%20of%20a%20Medium%20Voltage%20Hybrid%20Inverter%20System_final %20%282%29.pdf Copyright and reuse:The Nottingham ePrints service makes this work by researchers of the University of Nottingham available open access under the following conditions. This article is made available under the University of Nottingham End User licence and may be reused according to the conditions of the licence. For more details see: http://eprints.nottingham.ac.uk/end_user_agreement.pdf A note on versions:The version presented here may differ from the published version or from the version of record. If you wish to cite this item you are advised to consult the publisher's version. Please see the repository url above for details on accessing the published version and note that access may require a subscription.For more information, please contact eprints@nottingham.ac.uk  Abstract-Hybrid converters consist of a main inverter processing the bulk of the power with poor waveform performance and a fast and versatile auxiliary inverter to correct the distortion. In this paper, the main converter is a medium voltage NPC inverter and the auxiliary inverter is a low-voltage and low-current rated current source inverter (CSI), with series capacitor being used to minimize the CSI voltage stress. The result is a high output current quality which is obtained with a very low switching stress in the main converter and a very small added installed power (<4%) in the CSI. This paper expands this concept by investigating the hybridization of a medium voltage inverter with an existing LCL filter and investigates the additional challenges related to resonances and proposes a solution for stable operation. Experimental validation of active ripple cancellation has been provided at 3kW. Index Terms-Active filters, Noise cancellation, Nonlinear filtersI. INTRODUCTION onversion of DC into AC at medium and high voltage levels has become a very important research topic now when the need to transfer very large amounts of power (GW) over long distances favour HVDC transmission systems. In the medium term it is predicted that the distribution system will remain AC which will require the use of high voltage DC/AC inverters to interface the transmission and distribution systems. Standard two-level inverters built using series connected devices were initially used in the first generation of forced commutated HVDC systems for their simplicity and the easiness to embed redundancy by adding additional devices in series; however, difficulties in achieving static and more importantly dynamic voltage sharing during switching meant that the harmonic performance of su...

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