Robert M. Reedy

Power line carrier permissive as a simple and safe method of enabling inverter ride-through operation of distributed grid-tied photovoltaic systems

Conventional anti-islanding techniques used in grid-tied photovoltaic (PV) systems pose many disadvantages at high levels of PV deployment. One such issue is the inability of these systems to ride-through grid disturbances. In this paper, the use of a Power Line Carrier Communications (PLCC) Permissive anti-islanding scheme is investigated as a means of safely enabling ride-through operation of grid-tied photovoltaic systems. Here potential fault scenarios are considered, along with performance, cost, and design considerations for the PLCC Permissive components, as well as potential system configurations and methods of implementation. While PV systems are the largest (and growing) form of distributed generation (DG) generating in parallel with utility feeders, it is important to note that this technique is effective for any DG technology, whether inverter-based or rotating, including wind, hydro and fossil fueled bio-gas machines.

New results for power line carrier-based islanding detection and an updated strengths and weaknesses discussion

As PV deployment levels increase, loss of mains detection, or islanding detection, has again arisen as a primary concern among the utility community. This is true especially in multi-inverter cases, cases with a mix of distributed resources, and on difficult feeders on which false tripping may be a disproportionately significant problem. Power line carrier communications can be effective in solving this problem for all types of distributed generation. This paper provides an update on laboratory and field testing of this technique; discusses some of its unique but lesser-known advantages; and examines some of its weaknesses.

Solar energy grid integration systems : final report of the Florida Solar Energy Center Team.

Initiated in 2008, the Solar Energy Grid Integration Systems (SEGIS) program is a partnership involving the U.S. DOE, Sandia National Laboratories, private sector companies, electric utilities, and universities. Projects supported under the program have focused on the complete-system development of solar technologies, with the dual goal of expanding utility-scale penetration and addressing new challenges of connecting large-scale solar installations in higher penetrations to the electric grid. The Florida Solar Energy Center (FSEC), its partners, and Sandia National Laboratories have successfully collaborated to complete the work under the third and final stage of the SEGIS initiative. The SEGIS program was a three-year, three-stage project that include conceptual design and market analysis in Stage 1, prototype development and testing in Stage 2, and moving toward commercialization in Stage 3. Under this program, the FSEC SEGIS team developed a comprehensive vision that has guided technology development that sets one methodology for merging photovoltaic (PV) and smart-grid technologies. The FSEC teams objective in the SEGIS project is to remove barriers to large-scale general integration of PV and to enhance the value proposition of photovoltaic energy by enabling PV to act as much as possible as if it were at the very least equivalent to a conventional utility power plant. It was immediately apparent that the advanced power electronics of these advanced inverters will go far beyond conventional power plants, making high penetrations of PV not just acceptable, but desirable. This report summarizes a three-year effort to develop, validate and commercialize Grid-Smart Inverters for wider photovoltaic utilization, particularly in the utility sector.

Effects of solar resource variability on the future Florida transmission and distribution system

A common critique of photovoltaic energy is the susceptibility of the systems to high variability- passing clouds can affect a sites day-to-day energy production substantially. This research developed a tool to simulate photovoltaic energy systems in several scenarios throughout the state of Florida and quantifies the hour-to-hour impact of these systems on the statewide generation mix using 11 years of historical weather data. While the hourly changes in aggregate system output for distributed PV systems was predictable between months, finer geographic granularity of irradiance data coupled with sub-hourly time intervals are required to further develop this model into one that is indispensable for utility system operators.

Quantifying solar power variability for a large central PV plant and small distributed PV plant

Photovoltaic energy is susceptible to high variability, caused by passing clouds that may affect a sites daily energy production substantially. The reduction in solar variability due to geographic diversity was compared for a large central PV plant and small distributed PV plants using a multistep approach. At short timescales, geographic smoothing offers a strong benefit, which decreases with longer timescales and increased spatial correlation. The design attributes and relative locations of individual PV systems on a distribution feeder could significantly change the geographic dispersion effects.

Recent activities on wider utilization of photovoltaic technology in Florida

In the last year numerous developments have occurred for wider utilization of photovoltaic (PV) technology in Florida with the initiatives of the state administration and government officials. Some progressive utilities have also spurred PV use through rebates to consumers and decisions to deploy large PV projects. The most notables have included the state grants and rebates by the Florida Energy Office (FEO) under the Renewable Energy Technologies Grants Program, SunSmart Schools Program, Solar Energy Systems Incentives Program, a new regulation on interconnection and net metering by the Florida Public Service Commission (FPSC) and Executive Orders by the Florida Governor driving a Renewable Portfolio Standard and wider use of PV in government buildings.