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1. Dynamic life cycle economic and environmental assessment of residential solar photovoltaic systems

   https://doi.org/10.1016/j.scitotenv.2020.137932  

   Ren, Mingcheng ; Mitchell, Clayton R. ; Mo, Weiwei ( June 2020 , Science of the total environment)

   With the increasing implementation of solar photovoltaic (PV) systems, comprehensive methods and tools are required to dynamically assess their economic and environmental costs and benefits under varied spatial and temporal contexts. This study integrated system dynamics modeling with life cycle assessment and life cycle cost assessment to evaluate the cumulative energy demand, carbon footprint, water footprint, and life cycle cost of residential grid-connected (GC) and standalone (SA) solar PV systems. The system dynamics model was specifically used for simulating the hourly solar energy generation, use, and storage during the use phase of the solar PVs. The modeling framework was then applied to a residential prototype house in Boston, MA to investigate various PV panel and battery sizing scenarios. When the SA design is under consideration, the maximum life cycle economic saving can be achieved with 20 panels with no battery in the prototype house, which increases the life cycle economic savings by 511.6% as compared to a baseline system sized based upon the engineering rule-of-thumb (40 panels and 40 batteries), yet decreases the demand met by 55.7%. However, the optimized environmental performance was achieved with significantly larger panel (up to 300 units) and battery (up to 320 units) sizes. Thesemore »optimized configurations increase the life cycle environmental savings of the baseline system byup to 64.6%, but significantly decrease the life cycle economic saving by up to 6868.4%. There is a clear environmental and economic tradeoff when sizing the SA systems. When the GC system design is under consideration, both the economic and environmental benefits are the highest when no battery is installed, and the benefits increase with the increase of panel size. However, when policy constraints such as limitations/caps of grid sell are in place, tradeoffs would present as whether or not to install batteries for excess energy storage.« less
2. Planning for Distribution Resilience under Variable Generation: Prevention, Surviving and Recovery

   https://doi.org/10.1109/GreenTech.2018.00018  

   Jin, Tongdan ; Mai, Nhi ; Ding, Yi ; Vo, Long ; Dawud, Rana ( April 2018 , 2018 IEEE Green Technologies Conference)

   Power grids based on traditional N-1 design criteria are no longer adequate because these designs do not withstand extreme weather events or cascading failures. Microgrid system has the capability of enhancing grid resilience through defensive or islanded operations in contingency. This paper presents a probabilistic framework for planning resilient distribution system via distributed wind and solar integration. We first define three aspects of resilient distribution system, namely prevention, survivability and recovery. Then we review the distributed generation planning models that comprehend moment estimation, chance constraints and bi-directional power flow. We strive to achieve two objectives: 1) enhancing the grid survivability when distribution lines are damaged or disconnected in the aftermath of disaster attack; and 2) accelerating the recovery of damaged assets through pro-active maintenance and repair services. A simple 9-node network is provided to demonstrate the application of the proposed resilience planning framework
3. A Multiport Bidirectional LLC Resonant Converter for Grid-Tied Photovoltaic-Battery Hybrid System

   Adel Nasiri, Garry Jean-Pierre ( June 2020 , International Journal of Renewable Energy Research)

   Distributed power generation plants with combined photovoltaic (PV) systems and integrated energy storage for grid-connected applications have seen an increase in research interest in recent years. However, the combination of multiple energy sources requires numerous DC-DC converters and thus becomes more complex. To address this issue, a multiport bidirectional DC-DC LLC resonant converter for grid connected applications is presented in this research. In order to minimize the control complexity of the proposed system, a zone based controller approach with an integrated modified maximum power point tracking (MMPPT) method, which is based on the incremental conductance method, is also developed. This proposed controller is able to regulate the converter voltage and power flow while either delivering or taking power from the utility grid. The converter presented in this study contains a bidirectional buck-boost converter and an LLC resonant converter in addition to a voltage source grid-tied inverter which are interfacing the PV, the battery and the utility. Extensive simulation analyses through MATLAB/Simulink have proved the operations of the proposed topology.
4. An integrated approach to microgrid sizing and flow shop scheduling via climate analytics

   Subramanyam, V. ; Jin, T. ; Novoa, C. ( April 2020 , Journal of cleaner production)

   A variety of methods have been proposed to assist the integration of microgrid in flow shop systems with the goal of attaining eco-friendly operations. There is still a lack of integrated planning models in which renewable portfolio, microgrid capacity and production plan are jointly optimized under power demand and generation uncertainty. This paper aims to develop a two-stage, mixed-integer programming model to minimize the levelized cost of energy of a flow shop powered by onsite renewables. The first stage minimizes the annual energy use subject to a job throughput requirement. The second stage aims at sizing wind turbine, solar panels and battery units to meet the hourly electricity needs during a year. Climate analytics are employed to characterize the stochastic wind and solar capacity factor on an hourly basis. The model is tested in four locations with a wide range of climate conditions. Three managerial insights are derived from the numerical experiments. First, time-of-use tariff significantly stimulates the wind penetration in locations with medium or low wind speed. Second, regardless of the climate conditions, large-scale battery storage units are preferred under time-of-use rate but it is not the case under a net metering policy. Third, wind- and solar-based microgrid ismore »scalable and capable of meeting short-term demand variation and long-term load growth with a stable energy cost rate.« less
5. Microgrid Control Strategy Based on Battery Energy Storage System-Virtual Synchronous Generator (BESS-VSG)

   https://doi.org/10.1109/KPEC47870.2020.9167653  

   Gao, Wei ( July 2020 , 2020 IEEE Kansas Power and Energy Conference (KPEC))

   With more and more renewable energy resources integrated into the power grid, the system is losing inertia because power electronics-based generators do not provide natural inertia. The low inertia will cause the microgrid to be more sensitive to disturbance and thus a small load change may result in a severe deviation in frequency. Based on the basic VSG algorithm, which is to mimic the characteristic of the traditional synchronous generator, the frequency can be controlled to a stable value faster and more smoothly when there is a fluctuation in the PV power generation and/or load change. However, characteristic of the VSG depends on the system structure in consideration of multiple generations, such as Synchronous Generator (SG), PV and Battery Energy Storage System (BESS), which greatly increases the complexity of applying VSG in practical power system. Furthermore, with BESS-VSG, Maximum Power Point (MPP) operation of PV is guaranteed. In addition, an adaptive VSG method is developed for a microgrid system, and the corresponding simulation in Matlab/Simulink shows the effectiveness of the adaptive VSG method.