Solar Photovoltaic and Thermal Energy Systems: Current Technology and Future Trends

Solar systems have become very competitive solutions for residential, commercial, and industrial applications for both standalone and grid connected operations. This paper presents an overview of the current status and future perspectives of solar energy (mainly photovoltaic) technology and the required conversion systems. The focus in the paper is put on the current technology, installations challenges, and future expectations. Various aspects related to the global solar market, the photovoltaic (PV) modules cost and technology, and the power electronics converter systems are addressed. Research trends and recommendations for each of the PV system sectors are also discussed.Junta de Andalucía P11-TIC-7070Ministerio de Ciencia e Innovación TEC2016-78430-

A Review of Current Research Trends in Power-Electronic Innovations in Cyber-Physical Systems.

In this paper, a broad overview of the current research trends in power-electronic innovations in cyber-physical systems (CPSs) is presented. The recent advances in semiconductor device technologies, control architectures, and communication methodologies have enabled researchers to develop integrated smart CPSs that can cater to the emerging requirements of smart grids, renewable energy, electric vehicles, trains, ships, internet of things (IoTs), etc. The topics presented in this paper include novel power-distribution architectures, protection techniques considering large renewable integration in smart grids, wireless charging in electric vehicles, simultaneous power and information transmission, multi-hop network-based coordination, power technologies for renewable energy and smart transformer, CPS reliability, transactive smart railway grid, and real-time simulation of shipboard power systems. It is anticipated that the research trends presented in this paper will provide a timely and useful overview to the power-electronics researchers with broad applications in CPSs.post-print2.019 K

Fault Discrimination Using SiC JFET Based Self-Powered Solid State Circuit Breakers in a Residential DC Community Microgrid

This thesis validates the use of ultra-fast normally-on SiC JFET based self-powered solid state circuit breakers (SSCBs) as the main protective device for a 340Vdc residential DC community microgrid. These SSCBs will be incorporated into a radial distribution system so that line to line short circuit faults and other types of faults can be isolated anywhere within the microgrid. Because of the nature and characteristics of short circuit fault inception in DC microgrids, the time-current trip characteristics of protective devices must be several orders of magnitude of faster than conventional circuit breakers. The proposed SSCB detects short circuit faults by sensing its drain-source voltage rise, and draws power from the fault condition to turn and hold off the SiC JFET. The new two-terminal SSCB can be directly placed in a circuit branch without requiring any external power supply or additional wiring. To achieve the coordination between upstream and downstream SSCBs in the DC community microgrid, a little change has been made to the proposed SSCB. A resistor in the schematic of SSCB has been changed to a potentiometer to have a different response time to short circuit fault. In order to figure out the value of that potentiometer to get the best coordination, a transfer function is derived. LTspice VI and PLECS are used to verify the analytical work in the design. In the simulation layout, the DC community microgrid has been simplified to a radial system and 5 SSCBs are connected in series. Short circuit fault is applied at different locations in the DC system to test the effectiveness of the coordination scheme

A review on power electronics technologies for power quality improvement

Nowadays, new challenges arise relating to the compensation of power quality problems, where the introduction of innovative solutions based on power electronics is of paramount importance. The evolution from conventional electrical power grids to smart grids requires the use of a large number of power electronics converters, indispensable for the integration of key technologies, such as renewable energies, electric mobility and energy storage systems, which adds importance to power quality issues. Addressing these topics, this paper presents an extensive review on power electronics technologies applied to power quality improvement, highlighting, and explaining the main phenomena associated with the occurrence of power quality problems in smart grids, their cause and effects for different activity sectors, and the main power electronics topologies for each technological solution. More specifically, the paper presents a review and classification of the main power quality problems and the respective context with the standards, a review of power quality problems related to the power production from renewables, the contextualization with solid-state transformers, electric mobility and electrical railway systems, a review of power electronics solutions to compensate the main power quality problems, as well as power electronics solutions to guarantee high levels of power quality. Relevant experimental results and exemplificative developed power electronics prototypes are also presented throughout the paper.This work has been supported by FCT-Fundação para a Ciência e Tecnologia within the R&D Units Project Scope: UIDB/00319/2020. This work has been supported by the FCT Project DAIPESEV PTDC/EEI-EEE/30382/2017 and by the FCT Project newERA4GRIDs PTDC/EEIEEE/30283/2017

Photovoltaics, Batteries, and Silicon Carbide Power Electronics Based Infrastructure for Sustainable Power Networks

The consequences of climate change have emphasized the need for a power network that is centered around clean, green, and renewable sources of energy. Currently, Photovoltaics (PV) and wind turbines are the only two modes of technology that can convert renewable energy of the sun and wind respectively into large-scale power for the electricity network. This dissertation aims at providing a novel solution to implement these sources of power (majorly PV) coupled with Lithium-ion battery storage in an efficient and sustainable approach. Such a power network can enable efficiency, reliability, low-cost, and sustainability with minimum impact to the environment. The first chapter illustrates the utilization of PV- and battery-based local power networks for low voltage loads as well as the significance of local DC power in the transportation sector. Chapter two focuses on the most efficient and maximum utilization of PV and battery power in an AC infrastructure. A simulated use-case for load satisfaction and feasibility analysis of 10 university-scale buildings is illustrated. The role of PV- and battery-based networks to fulfill the new demand from the electrification of the surface transportation sector discussed in Chapter three. Chapter four analyzes the PV- and battery- based network on a global perspective and proposes a DC power network with PV and complementary wind power to fulfill the power needs across the globe. Finally, the role of SiC power electronics and the design concept for an SiC based DC-to-DC converter for maximum utilization of PV/wind and battery power through enabling HVDC transmission is discussed in Chapter six

A Viable Residential DC Microgrid for Low Income Communities – Architecture, Protection and Education

The availability of fossil fuels in the future and the environmental effects such as the carbon footprint of the existing methodologies to produce electricity is an increasing area of concern. In rural areas of under-developed parts of the world, the problem is lack of access to electrification. DC microgrids have become a proven solution to electrification in these areas with demonstrated exceptional quality of power, high reliability, efficiency, and simplified integration between renewable energy sources (principally solar PV) and energy storage. In the United States, a different problem occurs that can be addressed with the same DC microgrid approach that is finding success internationally. In disinvested, underserved communities with high unemployment and low wages, households contribute a significant portion of their income towards the fixed cost of their electrical utility connection, which by law must be supplied to every household. In order to realize such a microgrid in these communities, there are three major areas which need to be accounted for. Firstly, there needs to be a custom architecture for the community under consideration and it needs to be economical to match the needs of the underserved community. Secondly, DC microgrid for home energy interconnection is potentially less complex and less expensive to deploy, operate and maintain however, faster protection is a key element to ensuring resilience, viability and adoptability. Lastly, these types of efforts will be sustainable only if the people in the community are educated and invested in the same as they are the key stakeholders in these systems. This dissertation presents an approach to make the DC Microgrid economically feasible for low income households by reducing the cost they incur on electric bills. The approach is to overlay a DC system into homes that have a utility feed in order to incorporate renewable energy usage into an urban setting for the express purpose of driving down individual household utility costs. The results show that the incorporation of a certain level of “smart” appliances and fixtures into the renovation of vacated homes and the use of a microgrid to enable sharing of renewable energy, such as solar power combined with energy storage, between homes in the proposed architecture yields the least expensive option for the patrons. The development of solid state circuit breakers that interface between the microgrid and the home DC power panels helps in faster protection of the DC system. In this dissertation, a SiC JFET based device is designed and built to protect against DC faults at a faster rate than the available solutions. The prototype is tested for verification and used to discriminate against short circuit faults and the results show the successful fault discrimination capabilities of the device. A basic system level simulation with the protection device is implemented using Real Time Hardware in the loop platform. Finally, as a part of engaging the community members, the high school kids in the area who might potentially be living in some of the houses in this community are being educated about the microgrid, appliances and other technologies to get a better understanding of STEM and hopefully inspiring them to pursue a career in STEM in the future

A Viable Residential DC Microgrid for Low Income Communities – Architecture, Protection and Education

The availability of fossil fuels in the future and the environmental effects such as the carbon footprint of the existing methodologies to produce electricity is an increasing area of concern. In rural areas of under-developed parts of the world, the problem is lack of access to electrification. DC microgrids have become a proven solution to electrification in these areas with demonstrated exceptional quality of power, high reliability, efficiency, and simplified integration between renewable energy sources (principally solar PV) and energy storage. In the United States, a different problem occurs that can be addressed with the same DC microgrid approach that is finding success internationally. In disinvested, underserved communities with high unemployment and low wages, households contribute a significant portion of their income towards the fixed cost of their electrical utility connection, which by law must be supplied to every household. In order to realize such a microgrid in these communities, there are three major areas which need to be accounted for. Firstly, there needs to be a custom architecture for the community under consideration and it needs to be economical to match the needs of the underserved community. Secondly, DC microgrid for home energy interconnection is potentially less complex and less expensive to deploy, operate and maintain however, faster protection is a key element to ensuring resilience, viability and adoptability. Lastly, these types of efforts will be sustainable only if the people in the community are educated and invested in the same as they are the key stakeholders in these systems. This dissertation presents an approach to make the DC Microgrid economically feasible for low income households by reducing the cost they incur on electric bills. The approach is to overlay a DC system into homes that have a utility feed in order to incorporate renewable energy usage into an urban setting for the express purpose of driving down individual household utility costs. The results show that the incorporation of a certain level of “smart” appliances and fixtures into the renovation of vacated homes and the use of a microgrid to enable sharing of renewable energy, such as solar power combined with energy storage, between homes in the proposed architecture yields the least expensive option for the patrons. The development of solid state circuit breakers that interface between the microgrid and the home DC power panels helps in faster protection of the DC system. In this dissertation, a SiC JFET based device is designed and built to protect against DC faults at a faster rate than the available solutions. The prototype is tested for verification and used to discriminate against short circuit faults and the results show the successful fault discrimination capabilities of the device. A basic system level simulation with the protection device is implemented using Real Time Hardware in the loop platform. Finally, as a part of engaging the community members, the high school kids in the area who might potentially be living in some of the houses in this community are being educated about the microgrid, appliances and other technologies to get a better understanding of STEM and hopefully inspiring them to pursue a career in STEM in the future

Increasing the capacity of the Low Voltage Distribution Networks using All-SiC AC-AC Converters

Towards 2020, future energy scenarios predict an excessive penetration of distributed generation (DG) in low voltage (LV) networks as well as a significant uptake of electric vehicles (EVs) and electro-heating. The Distribution Network Operators (DNOs) in UK will face significant challenges towards this de-carbonised electricity generation and consumption shift. The deployment of these so-called low carbon technologies (LCTs) will impact the performance of the distribution network in such way where solutions will be needed to maintain capacity, reliability and the availability of the electricity supply to customers. The practise to put more copper on the ground – reinforcement - in order to facilitate these changes is found to be expensive and disruptive to the public and business. An innovative solution proposed in this thesis is to increase the voltage along the distribution feeders and step it back down at a customer’s premises. Results show that a significant increase at the hosting capacity of the existing network can be achieved and power quality problems such as overvoltage caused by DG can be avoided. The voltage step-down device, which is termed a voltage control unit (VCU), is to be located in the meter-box of each house. This location raises challenges round the temperature rise in the box caused by VCU losses, and the subsequent effect on the electricity meter and cut-out fuse. It also imposes constraints on the size and weight of the VCU so that a very high efficiency design is required, with high power density and small mass. The optimum VCU design was found to be a power electronic AC Chopper using new Silicon Carbide (SiC) MOSFETs and diodes. The technology was demonstrated by designing, constructing and testing two interleaved, parallel operation, 1 kW AC Chopper modules. Results from the prototype were compared against Spice simulation results and theory and confirmed that the target efficiency of 99% was achieved