Effect of Unbalanced and Non-Linear Loads on Operation of the Turbogenerator of a Distributed Generation Unit

Abstract

The article presents a description of models and results of research on separate and joint effects of unbalanced and non-linear loads on the operation of a lower-power synchronous generator. The modeling of the generator included automatic regulators of excitation and rotor speed. For our studies, we used computer models built in the MATLAB environment and the Fazonord package, as well as a physical model of a low-power synchronous generator. The simulation results attested to the occurrence of the following negative effects: there was a noticeable negative sequence current, the generator began to emit higher harmonics into the network, and the amplitude of forced oscillations of the excitation current increased. The presence of these effects can lead to additional mechanical vibrations of the rotor, accelerated wear of the equipment, and loss of stability. To ensure that low-power generators can operate in the presence of unbalance and harmonic distortion, it is necessary to limit their load. The maximum phase current difference, which must not exceed 12% of the nominal current, can be used as a criterion. Furthermore, when distributed generation units serve non-linear and unbalanced loads, it is necessary to implement special measures to protect the generating equipment: the use of direct current links, the use of harmonic filters, the installation of generator protections limiting negative sequence current, the use of automatic excitation current limitation, etc.