• Energy Research

Smart networks are a research topic that is currently of great interest both in the academic community and in the business sector, within smart networks today you can find microgrid, nanogrid, and picogrid without it has been possible to define a standard that differentiates them; It is necessary to investigate more thoroughly in these topics and train professionals to support the research and development processes around them. To achieve this, some institutes, research centers, and universities are advancing assemblies in the laboratory for their studies. This work is framed within the development of a pilot micro-network laboratory that can work isolated or interconnected, implemented at the Universidad del Valle. This article presents a particular case of a nanogrid-part of the microgrid under development at Universidad del Valle-with the initial objective of investigating problems associated with non-interconnected systems, applicable to the Colombian context. Details of the design of the nanogrid are presented where the use of an Etap-Real Time software is considered, allowing monitoring, real-time management, simulation, and prediction integral. In particular, for the case in hand, details of the study are shown considering the flows in DC and AC, contrasted in a simulation with Etap-Real Time versus operational data of the nanogrid.

The photovoltaic systems are electrical, electronic, and mechanical elements. These systems also face different environmental and operating conditions susceptible to failure. In addition, photovoltaic systems can be the only source of electricity generation, and an affectation on the energy supply can harm the community. In many places, photovoltaic systems are the only source of energy because they are not part of what is known in Colombia as the National Interconnected System (SIN). Which comprises the direct connection between large generators (hydroelectric and/or thermal plants) and consumers. In fact, PV system damage would affect food refrigeration or everyday things like charging a cell phone. Therefore, it is necessary to register, monitor the operation elements of PV systems, and develop strategies that allow the diagnosis to detect faults. In this work, we propose a fault-diagnosis using the PV systems measurements that is, power converter, photovoltaic panels with also mathematical models to determine the deviation between the estimated and measured signals as voltages and currents.

The DC-link capacitor is one of the components that are more prone to faults in energy-distributed systems based on voltage source inverters. A predictive maintenance approach should allow to foresee the risk of an unexpected system shutdown. In this study, a two-stage diagnostic approach that is aimed at determining the health status of the DC-link capacitor in a single-phase grid-connected PV system was proposed. The equivalent series resistance (ESR) and the capacitance (C) values were used as indicators in the estimation of the degradation stage. Electrochemical impedance spectroscopy (EIS) was used to estimate the impedance curve of the DC-link capacitor, and a multi-fitting algorithm allowed us to determine the ESR and C parameters. A comparison between the estimated values C and ESR and the nominal values was used to quantify the fault severity. It was demonstrated that the EIS allowed the determination of the capacitor impedance regardless of the actual operating conditions of the photovoltaic generator, such as during irradiance changes and with the maximum power point algorithm turned off. By using the capacitor simplified model and a multi-fitting algorithm, the C and ESR values were estimated with an error that was lower than 1%. An analysis of the hardware required to implement the proposed approach in real applications by achieving the desired accuracy was also proposed.