This paper presents the design and experimental voltage quality evaluation of controllers for the output voltages of 3-phase four-leg voltage source inverters. These inverters are needed in stand-alone power systems to supply linear and non-linear, balanced or unbalanced loads with constant RMS value voltages at fixed frequency. Comparisons include closed loop outer voltage controllers based on predictive, sliding mode and decoupled proportional-integral controllers in dqo synchronous space, fitted with an inner hysteretic current loop vector controller in αβγ space. The 3-phase four-leg VSI output voltages waveform quality is analysed under unbalanced and non-linear loads.
Keywords: stand-alone four-leg inverter; non-linear voltage vector modulator; voltage waveform quality
Ricardo Luís 1,2,*, José Fernando Silva 1 and José Carlos Quadrado 2
1INESC-ID, Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal
2Instituto Superior de Engenharia de Lisboa, Polytechnic Institute of Lisbon, 1959-007 Lisboa, Portugal
*Author to whom correspondence should be addressed.