Current Balancing Strategy in Parallel-Connected Legs of Power Inverters Josep Pou, Jordi Zaragoza, Gabriel Capella TECHNICAL UNIVERSITY OF CATALONIA Colom, 1 08222 Terrassa, Catalonia-Spain Tel.: +34 / 937398306 Fax: +34 / 937398016 E-Mail: pou@eel.upc.edu; zaragoza@eel.upc.edu; capella@eel.upc.edu URL: http://www.upc.edu Igor Gabiola, Salvador Ceballos, Eider Robles ROBOTIKER-TECNALIA TECHNOLOGIC CORPORATION, ENERGY UNIT Parque Tecnológico Edif. 202 48170 Zamudio, Basque Country-Spain Tel.: +34 / 94 600 22 66 Fax: +34 / 94 600 22 99 E-Mail: igabiola@robotiker.es; sceballos@robotiker.es; erobles@robotiker.es URL: http://www.robotiker.es Acknowledgements This work was supported by the Ministerio de Ciencia y Tecnologia of Spain under Projects ENE2007-67033-C03-01 and ENE2007-67033-C03-03, the Department d’Universitats Recerca i Societat de la Informació of the Generalitat de Catalunya, the Basque Country Government, and the Torres Quevedo Program. Keywords «Modulation Strategies», «Converter Control», «Pulsewidth Modulation», «Parallel legs», «Current Balance». Abstract The parallel connection of inverter legs is a way to increase the output currents and thus the converter rated power. The connection is made by inductors and a critical issue is to achieve balanced currents among the legs. Circulating currents produce additional losses and stress to the power devices of the converter. Therefore, they should be controlled and minimized. An efficient technique to achieve such a balance is presented in this paper. The proposed strategy does not include proportional-integral (PI) controllers and parameter tuning is not required. The exact control action to achieve current balance is straightforward calculated and applied. Simulation and experimental results are shown in this paper to verify efficiency of the proposed balancing method. Introduction Multilevel converters are extensively used in high power systems. The main reason for this is because they can deal with high voltages. However, in some fields such as wind generation, high power is sometimes achieved by increasing the output current levels and not the voltage levels [1]. Consequently, they are kept in the low-voltage range and, therefore, under the low-voltage regulations, which are less demanding than mid-voltage regulations. Furthermore, the cost of low-voltage maneuver devices is much cheaper under such conditions. Current Balancing Strategy in Parallel-Connected Legs of Power Inverters POU Josep EPE 2009 - Barcelona ISBN: 9789075815009 P.1