11. Energy Management of the Grid-Connected PV Array

Solar energy has an important place in the global energy context, this leading to an intense concern in the unconventional energies field. Even if the earth receives only a small fraction of the solar radiation emitted by the Sun (because the radiation suffers the phenomena of absorption and diffusion in the atmosphere) the solar energy has become one of the most important renewable sources. Solar energy can be captured and converted into electrical energy by using the photovoltaic technologies and/or thermal energy, through the use of various types of solar panels heat shields. In this context, the field of producing electricity with photovoltaic panels is approached in this chapter. The photovoltaic panels are devices that convert the solar energy into electrical energy. Depending on weather conditions, the generated renewable energy oscillates, being required an energy storage system to store the excess energy or to discharge energy during the lack of energy. The best solution applied for short-term storage of energy is the battery. On the other hand, the photovoltaic systems only use a portion of the solar radiation and of certain wavelengths, in order to produce electrical energy. The rest of the energy received at the surface is converted into heat, leading to a rise in temperature of the cells components and reduction in yield. In conclusion, increasing productivity and energy efficiency of these facilities involves both the efficiency of their operation in the electric field and the study of the thermal phenomena that take place. In order to ensure a high degree of felicity of the electrical energy management at the level of a microgrid type user, it is necessary to know the energy flows, the structure of the distribution network, and identification of the technical solutions depending on the field. In this chapter, the main functional parameters of the system considered will be analyzed, the quality parameters at the level of the electricity system of the user will be estimated, and the operating parameters of the system considered will be also analyzed. The objective of the chapter is to propose a technical solution to improve the efficiency of a photovoltaic power plant within an area of seventy hectares through control, surveillance, metering and monitoring of the system from distance based on Supervisory Control and Data Acquisition (SCADA) system. The photovoltaic power plant used to carry out the experiments is located in Romania. The location of the photovoltaic park is in a plain area where solar radiation is higher (over 1450 kWh/m² year, in particular in the summer). With the help of the SCADA system, the energy management of the photovoltaic park can be achieved for: a short period (one day) or for a longer period (a week). The SCADA system offers information about: total energy delivered (kWh), day energy delivered (kWh), active inverter power (kW), percent of availability for photovoltaic power plant, weather info (ambient temperature, plane radiation etc.), hourly graphs about plant production, alarms, current strings, energy meter (exported active-reactive power, imported active-reactive power), data about the weather station, inverter graphs, state of power transformers, breaker state, earthing state, month radiation, month exported active energy, currents variation (I_a, I_b, I_c), leakage current variation (I_g), and voltage variation (V_a, V_b, V_c). The data stored by the system will allow the user to receive current information, but also these data can be compared with the data stored in the same period of the past years, in order to establish the productive efficiency of the photovoltaic power plant.