Modeling and control of distributed generation under distorted and unbalanced conditions

This paper presents a novel distributed generation (DG) control strategy under both distorted and unbalanced conditions. Actually the power quality of microgrid bus and the point of common coupling are the main concerns due to the determination of high-quality power energy to the main grid and sensitive loads connected to microgrid bus. To tackle this problem, three control schemes based on PIR cascaded structure for DG units are developed to realize different control objectives. In these categories, the fundamental voltage is regulated by conventional PI controller to ensure direct voltage support and smooth operation mode transition while the harmonics or unbalanced variables are compensated with resonate controller in synchronous reference frame without sequential sequence decomposition. Modeling analysis and performance evaluation show the flexible and seamless transition of these control schemes. The control strategy can satisfy power quality requirements of microgrid in various operation modes, meanwhile, guarantee the robust and smooth operation of microgrid.