Análise e controle dos níveis de tensão e fator de potência em redes de distribuição com sistemas fotovoltaicos conectados

Abstract

With the increasing integration of photovoltaic (PV) systems for micro and mini generation connected to the distribution grid, both at medium voltage (MV) and low voltage (LV) levels, new methodologies for analyzing and controlling voltage levels and reactive power flow are required. These needs arise from the changes in voltage levels in distribution lines and the increase in charges for excess reactive power paid by consumers. In this context, grid-connected PV systems must monitor their voltage levels and maintain a minimum power factor (PF) of 0.92 at the point of common coupling (PCC). This study aims to develop a model for analyzing and controlling voltage levels and power factor in units with micro and mini distributed photovoltaic generation. The study presents the use of volt-var and volt-watt control models, combined with active power factor control, achieved through monitoring the output power of intelligent inverters in PV systems and the voltage level at the PCC. Additionally, it considers the use of battery energy storage systems (BESS) at consumer units and in the distribution network as support. To this end, simulations were conducted in OpenDSS using a Python algorithm, utilizing an IEEE 34-node circuit with the addition of an LV network. In this test circuit, thirty new loads were implemented, fifteen MV and fifteen LV, connected to the MV and LV networks of the circuit. In ten of these loads, five in each voltage class, and selected randomly, PV systems were installed together with BESS. Furthermore, a BESS was implemented at the end of the distribution network to assist in controlling voltage levels and reactive power flow. The test simulations were executed in daily mode with a 15-minute interval. After the test simulations, the algorithm was implemented in a real distribution network model, PAL 16. This network has MV and LV circuits with a variety of consumers connected at both voltage levels. In this network, PV systems were installed at consumers with higher demand, allowing greater generation capacity in these systems, with consumers dispersed throughout the distribution network. For analysis purposes, PV systems were also installed concentrated near each other and close to the origin of the network feeder, aiming to highlight the benefits of the control model. The results showed a reduction in reactive power flow and the maintenance of voltage levels in the monitored lines. This reduction in reactive power flow is due to the active management of the power factor, which parametrizes the intelligent inverters and, consequently, promotes the injection of reactive power by the generators themselves to support their loads. The implementation of voltage control modes, combined with the active power factor control in intelligent inverters, demonstrated effectiveness in maintaining voltage levels and power factor in the monitored lines.