Novel utility-scale photovoltaic plant electroluminescence maintenance technique by means of bidirectional power inverter controller

Producción CientíficaNowadays, photovoltaic (PV) silicon plants dominate the growth in renewable energies generation. Utility-scale photovoltaic plants (USPVPs) have increased exponentially in size and power in the last decade and, therefore, it is crucial to develop optimum maintenance techniques. One of the most promising maintenance techniques is the study of electroluminescence (EL) images as a complement of infrared thermography (IRT) analysis. However, its high cost has prevented its use regularly up to date. This paper proposes a maintenance methodology to perform on-site EL inspections as efficiently as possible. First, current USPVP characteristics and the requirements to apply EL on them are studied. Next, an increase over the automation level by means of adding automatic elements in the current PV plant design is studied. The new elements and their configuration are explained, and a control strategy for applying this technique on large photovoltaic plants is developed. With the aim of getting on-site EL images on a real plant, a PV inverter has been developed to validate the proposed methodology on a small-scale solar plant. Both the electrical parameters measured during the tests and the images taken have been analysed. Finally, the implementation cost of the solution has been calculated and optimised. The results conclude the technical viability to perform on-site EL inspections on PV plants without the need to measure and analyse the panel defects out of the PV installation.Ministerio de Industria, Economía y Competitividad (grant number RTC-2017-6712-3)Junta de Castilla y León (grant VA283P18

Novel utility-scale photovoltaic plant electroluminescence maintenance technique by means of bidirectional power inverter controller

Nowadays, photovoltaic (PV) silicon plants dominate the growth in renewable energies generation. Utility-scale photovoltaic plants (USPVPs) have increased exponentially in size and power in the last decade and, therefore, it is crucial to develop optimum maintenance techniques. One of the most promising maintenance techniques is the study of electroluminescence (EL) images as a complement of infrared thermography (IRT) analysis. However, its high cost has prevented its use regularly up to date. This paper proposes a maintenance methodology to perform on-site EL inspections as efficiently as possible. First, current USPVP characteristics and the requirements to apply EL on them are studied. Next, an increase over the automation level by means of adding automatic elements in the current PV plant design is studied. The new elements and their configuration are explained, and a control strategy for applying this technique on large photovoltaic plants is developed. With the aim of getting on-site EL images on a real plant, a PV inverter has been developed to validate the proposed methodology on a small-scale solar plant. Both the electrical parameters measured during the tests and the images taken have been analysed. Finally, the implementation cost of the solution has been calculated and optimised. The results conclude the technical viability to perform on-site EL inspections on PV plants without the need to measure and analyse the panel defects out of the PV installation

Implementation of SiC Power Electronics for Green Energy Based Electrification of Transportation

Increase in greenhouse gas emission poses a threat to the quality of air thus threatening the future of living beings on earth. A large part of the emission is produced by transport vehicles. Electric vehicles (EVs) are a great solution to this threat. They will completely replace the high usage of hydrocarbons in the transport sector. Energy efficiency and reduced local pollution can also be expected with full implementation of electrification of transportation. However, the current grid is not prepared to take the power load of EV charging if it were to happen readily. Moreover, critics are doubtful about the long-term sustainability of EVs in terms of different supply chain issues. The first step for tackling this problem from a research perspective was to do a thorough review of the details of charging in modern day grid. The downsides and lack of futuristic vision. Findings showed that implementing end to end DC based on green energy aided by SiC power electronics. To prove the findings analysis and modelling was done for SiC based charging network. A similar approach was implemented in EV powertrain development. The implementation of SiC power electronics in charging network showed lesser losses, higher thermal conductivity, lesser charging time. The effect on long term battery health and additional circuit was also observed. The cost of production can be reduced by volume manufacturing that has been discussed. In powertrain analysis and simulation the loss and heat reduction one shown on a component-by-component basis. Therefore, this research proposes a Silicon Carbide based end to end DC infrastructure based completely on solar and wind power. The pollution will further be reduced, and energy demands will be met

A review of hierarchical control for building microgrids

Building microgrids have emerged as an advantageous alternative for tackling environmental issues while enhancing the electricity distribution system. However, uncertainties in power generation, electricity prices and power consumption, along with stringent requirements concerning power quality restrain the wider development of building microgrids. This is due to the complexity of designing a reliable and robust energy management system. Within this context, hierarchical control has proved suitable for handling different requirements simultaneously so that it can satisfactorily adapt to building environments. In this paper, a comprehensive literature review of the main hierarchical control algorithms for building microgrids is discussed and compared, emphasising their most important strengths and weaknesses. Accordingly, a detailed explanation of the primary, secondary and tertiary levels is presented, highlighting the role of each control layer in adapting building microgrids to current and future electrical grid structures. Finally, some insights for forthcoming building prosumers are outlined, identifying certain barriers when dealing with building microgrid communities

Electric Vehicles Charging Stations’ Architectures, Criteria, Power Converters, and Control Strategies in Microgrids

Electric Vehicles (EV) usage is increasing over the last few years due to a rise in fossil fuel prices and the rate of increasing carbon dioxide (CO2) emissions. The EV charging stations are powered by the existing utility power grid systems, increasing the stress on the utility grid and the load demand at the distribution side. The DC grid-based EV charging is more efficient than the AC distribution because of its higher reliability, power conversion efficiency, simple interfacing with renewable energy sources (RESs), and integration of energy storage units (ESU). The RES-generated power storage in local ESU is an alternative solution for managing the utility grid demand. In addition, to maintain the EV charging demand at the microgrid levels, energy management and control strategies must carefully power the EV battery charging unit. Also, charging stations require dedicated converter topologies, control strategies and need to follow the levels and standards. Based on the EV, ESU, and RES accessibility, the different types of microgrids architecture and control strategies are used to ensure the optimum operation at the EV charging point. Based on the above said merits, this review paper presents the different RES-connected architecture and control strategies used in EV charging stations. This study highlights the importance of different charging station architectures with the current power converter topologies proposed in the literature. In addition, the comparison of the microgrid-based charging station architecture with its energy management, control strategies, and charging converter controls are also presented. The different levels and types of the charging station used for EV charging, in addition to controls and connectors used in the charging station, are discussed. The experiment-based energy management strategy is developed for controlling the power flow among the available sources and charging terminals for the effective utilization of generated renewable power. The main motive of the EMS and its control is to maximize usage of RES consumption. This review also provides the challenges and opportunities for EV charging, considering selecting charging stations in the conclusion.publishedVersio

Single and Dual DC Buses Nanogrids with Decentralized Control

The existing power system is based on a centralized approach. Large power plants produce AC electricity that is transmitted over long distances for distribution to the consumers. To meet a higher load demand, the entire system has to be upgraded, which is costly and acquiring rights of way can take decades. Another approach, called distributed generation, is the deployment of smaller generation units closer to the users. This can be based on renewable energy sources (RESs) that mitigate the environmental impact of power generation. However, the stochastic nature of RESs can lead to power quality issues in the distribution system. This can be addressed with the addition of energy storage units and controlling the system as a cluster or a microgrid. This concept can be extended for small buildings and residences, called nanogrids, offering a means for the realization of net-zero energy homes (NZEHs). These can be AC or DC, but the latter looks more promising since most RESs suitable for NZEHs provide a DC output and DC-DC interfaces tend to present a higher efficiency than their DC-AC counterparts. DC nanogrids also favor the integration of electric vehicles (EVs) and are compatible with modern, electronically controlled, appliances. To date, there are no standards concerning the number of buses and voltage levels of DC nanogrids. The control structure of DC micro and nanogrids, can be based on a hierarchical approach where the primary control level relies on locally measured quantities. This allows a decentralized operation of interfaces using the DC bus voltage as a communication means and V vs. I curves, with specific parameters, for coordination of operation, a method known as DC bus signaling (DBS). There are several aspects of DC nanogrids for NZEHs that deserve further investigation and are addressed in this thesis. These include a means for a smooth transition of the modes of operation of RESs, such as photovoltaic (PV), which employ V vs. I curves with three regions. This can minimize the DC bus voltage variations as the system adjusts to variations in load demand and power generation due to varying solar irradiances. The use of supercapacitors (SCs) along with batteries in hybrid energy storage systems (HESSs) can mitigate the impact of high and fast current variations on the losses and lifetime of the battery units. However, by controlling the HESS as a single unit, one forfeits the potential contribution of the SC and its high power capabilities to dynamically improve voltage regulation in a DC nanogrid. This can be achieved by controlling the SC and battery independently without sacrificing the support the battery receives from the SC. Finally, although dual DC bus nanogrids have been advocated by industry associations, they are conceived to have power sources and storage units only in the high voltage (HV) bus. The low voltage (LV) bus is fed through a unidirectional converter, making it vulnerable to a fault in a single element. This thesis proposes the deployment of generation and storage in both buses, with a bidirectional interface for optimizing power balance in both buses. The techniques proposed in this thesis are verified by means of simulation or experimental results

Review of Electric Vehicle Charging Technologies, Configurations, and Architectures

Electric Vehicles (EVs) are projected to be one of the major contributors to energy transition in the global transportation due to their rapid expansion. The EVs will play a vital role in achieving a sustainable transportation system by reducing fossil fuel dependency and greenhouse gas (GHG) emissions. However, high level of EVs integration into the distribution grid has introduced many challenges for the power grid operation, safety, and network planning due to the increase in load demand, power quality impacts and power losses. An increasing fleet of electric mobility requires the advanced charging systems to enhance charging efficiency and utility grid support. Innovative EV charging technologies are obtaining much attention in recent research studies aimed at strengthening EV adoption while providing ancillary services. Therefore, analysis of the status of EV charging technologies is significant to accelerate EV adoption with advanced control strategies to discover a remedial solution for negative grid impacts, enhance desired charging efficiency and grid support. This paper presents a comprehensive review of the current deployment of EV charging systems, international standards, charging configurations, EV battery technologies, architecture of EV charging stations, and emerging technical challenges. The charging systems require a dedicated converter topology, a control strategy and international standards for charging and grid interconnection to ensure optimum operation and enhance grid support. An overview of different charging systems in terms of onboard and off-board chargers, AC-DC and DC-DC converter topologies, and AC and DC-based charging station architectures are evaluated

DC Networks on the Distribution Level – New Trend or Vision?

"DC networks on Distribution Level – are they a new trend or a Vision?" That is the question that has focused the efforts of the Working Group the last two years, and whose consideration is summarized in this report. This report represents the first phase evaluation of this topic and is focused primarily on medium (MVDC) and low voltage (LVDC) level applications

Design and modelling of a large-scale PV plant.

Aquest TFM té com a objectiu principal el disseny i el modelatge d?una planta solar fotovoltaica de gran capacitat. El projecte estarà més centrat en els aspectes més purament energètics de la planta que els elements elèctrics integrats. Alguns dels elements de la planta que seran estudiats en més profunditat: tipus de panells, disposició dels panells a la planta, estudi de la superfície on la planta serà instal·lada, energia recol·lectada i avaluació del funcionament de la planta, anàlisi econòmic, etc. Finalment, el disseny i el modelatge de la planta seran validats mitjançant l?ús de software