THE PROBLEM OF OPTIMIZATION OF HYBRID ENERGY SYSTEM ACCORDING TO THE LEVEL OF DISPERSION OF GENERATED POWER

• Дата: 2022
• Автори: Gaevskii, О., Gaevska, А., Bodnyak, V., Konovalov, M.
• Формат: Стаття
• Мова: Ukrainian
• Опубліковано: Institute of Renewable Energy National Academy of Sciences of Ukraine 2022
• Теми: PV plant; smart-inverter; distribution grid; voltage regulation; disconnection of inverter from distribution grid
• Онлайн доступ: https://ve.org.ua/index.php/journal/article/view/331
• Назва журналу: Vidnovluvana energetika

The article considers the operation of a photovoltaic (PV) plant connected to the distribution grid (DG) via a smart inverter, which has the function of stabilizing the output voltage by regulating the reactive power. The electric model of the system “PV plant - radial DG - distribution substation (DSS)” is constructed and the corresponding numerical calculations of nonlinear equations system in the power flow representation are performed. The paper analyzes the influence of the inverter output power on the voltage at the point ofcommon connection (PCC) to the DG under the setting of different characteristics of the network equipment, namely: the parameters of step-up transformers and the power lines capacity. In our work the monitoring data obtained by PV inverters for which disconnections from DG are observed at high levels of solar radiation were used. It was found that the transformers power does not significantly affect the PCC overvoltage if the transformers have the appropriate power, and their electrical insulation is in good condition. The same applies to power losses in the distribution line. It is shown that the main role in exceeding the allowable output voltage of an inverter connected to DG is played by electrical losses in the connecting wires PCC to the step-up transformer. The limit values of the length of the connecting line for different types of wires widely used for low-power PV plants as well as for different types of network equipment DG and DSS are obtained. The possibility of voltage regulation at PCC by smart-inverter reactive power modulating is analysed. Simulation of inverter voltage regulation is performed considering the role of grid equipment (transformers and feeders). Estimates of the influence degree of dynamic inverter regulation as well as the dependence of the regulation effect on the connecting line length and on the step-up transformer power are obtained. It is shown that inverter regulation is more effective on decreasing voltage than on increasing, and that the regulating effect is more pronounced the greater the length of the connecting line.