| Abstract [eng] |
The final master's thesis examines the increase in the capacities of the distribution network using the reactive power control functions of solar power inverters. The study included a one-day simulation, which reveals a critical situation when highly favourable meteorological conditions prevail for solar power generation, instantaneous electricity consumption is insignificant and the initial voltage of 10 kV at the Riešė TP reaches the maximum maintained voltage (10.4 kV). For the study the 10 kV line L-1200 from the Riešė TP including all 0.4 kV lines was selected. This electric line was chosen because of large number of solar power plants (189 units). Using an electrical network modelling program "NEPLAN," the model of the selected line was created by entering all the line and solar power plant data. According to the applicable regulations, three reactive power functions were selected: Q(U), cosφ(U), and cosφ(P). Their characteristics were determined based on applicable regulations, analysis of scientific articles and practical experiments. A graph of the electrical generation profile for 1 day evaluating the data every 10 minutes was created based on the instantaneous output power quantities of the existing smart meters of solar power plants. The study consisted of 5 regimes: the first regime is normal without voltage restrictions, the second is normal with voltage restrictions, the third applies the Q(U) function to all power plants, the fourth applies cosφ(U), and the fifth applies cosφ(P). Values obtained in modes 3-5 were compared with the first (reference) mode and percentage changes were calculated. The main indicators that were calculated include generated energy, consumed reactive energy, losses of reactive and active power, loads on lines and transformers, number of disconnected power plants and minimum voltage reduction. In the final part of the work, the profitability of investments in the solar power plant was evaluated. The calculations were performed by applying and not applying reactive power control functions, in addition the average number of days per year when 1 kW of allowable generation power is not generated was determined, it was also evaluated how many such days per year could potentially occur. The annual amount of ungenerated energy (average derived from the difference in electricity generated during the first and second modes in each power plant) is subtracted from the modelled annual production forecast of the solar power plant, which considers only meteorological conditions and the electrical configuration. |
