Influence of nonlinear loads on the operation of turbo generators on distributed generation plants
The use of distributed generation plants (DGPs), including those based on renewable energy resources, allows stabilizing the voltage in peak hours, reducing losses in grids and releasing link capacities. In railroad power supply systems (RPSSs) based on DGPs it is possible to improve the quality of electric power, as well as the efficiency and reliability of power supply. However, the use of DGPs in RPSSs requires consideration of asymmetry and harmonic distortion, caused by single-phase loads and nonlinear draft load. These factors lead to additional heating of DGP units, which determines the need to limit power on them. The paper discusses the results of studies on the influence nonlinear loads on the operation of generators, fitted with automatic field and rpm controllers. Computer simulation results show that the increase in harmonic distortion of the load current may lead to an increase of the stator and the rotor currents of the turbo generator beyond acceptable values. This increases the amplitude of forced oscillations of the generator field current with a frequency which is a multiple of 300 Hz, which leads to additional losses and heating. The emergence of forced oscillations of electrical and mechanical parameters of the turbo generator in large nonlinear loads may cause increased wear and even generators winding failure. In addition to these conditions, the reduced margin of stability, damping properties deteriorate and increasing the probability of transition of the turbo generator in asynchronous mode. Therefore, the introduction of DGPs in RPSSs need to take measures to reduce the harmonic components in the load current, as well as to take into account these circumstances when selecting the settings of automatic field and rpm controllers.