Estudo e regulação dos níveis de tensão em sistemas de distribuição com alta penetração de renováveis utilizando simulações em tempo real

Abstract

This work presents a voltage analysis in distribution systems with different levels of PhotoVoltaic (PV) penetration. In addition, the work brings modeling of a single-stage converter, based on a Voltage Source Converter (VSC) topology with its respective control loops. Synchronous Reference Frame Phase-Locked Loop (SRF-PLL) and Maximum Power Point Tracking (MPPT) are also discussed and applied. Simulations are performed in real time using Real Time Digital Simulation (RTDS). For the IEEE 13 Node Test Feeder, modeling is developed in the RTDS software and the control is processed externally in dSPACE, resulting in a Hardware In The Loop (HIL) simulation. The European 18 Bus system obtained from Cigré is also modeled in RSCAD software and its controls are embedded in a programming block in the software’s own "C" language. The smart inverter concept is introduced in the work for the European system, using the Volt-Var-Watts control, in order to avoid overvoltage at the Common Coupling Point (PCC) and its consequent uncoupling from the network. The Volt-Watt performance developed to act in the MPPT algorithm is a possible contribution of the work, since in the literature its form of actuation in the system is not specific. Residential load profiles, solar radiation curves, and temperature are discretized on an hourly basis over a daily period, the purpose of which is to make the simulations more realistic. Simulation results are separated into two scenarios, the first being defined for the IEEE system 13 buses in Medium Voltage (MV), where the control of the voltage profile is done by a Voltage Regulator (VR) present in the substation. The second is defined for the system Cigré 18 buses in Low Voltage (LV), using the concept of smart inverters. The use of distributed inverters is investigated as an economically viable alternative to avoid the increase of investment in infrastructure by the concessionaire and to assist in the control of the energy tariff passed on to consumers, considering that only the RT may not be enough to maintain the voltage of systems with high local penetration of renewables in the form of Distributed Generation (DG). The results obtained with RT are satisfactory, however, for high levels of PV penetration, and depending on the distance from the PAC to the load center of the distribution network, it is not able to keep the voltage at acceptable levels. The Volt-Var-Watt control was promising for local control in the network for up to 20 % of PV penetration, above this percentage, at sporadic times of time overvoltage occurred in some buses of the system.