Reliability analysis of single-phase photovoltaic inverters with reactive power support

Reactive power support is expected to be an emerging ancillary requirement for single-phase photovoltaic (PV) inverters. This work assesses related reliability issues and focuses on the second stage or inversion process in PV inverters. Three PV inverter topologies are analyzed and their reliability is determined on a component-by-component level. Limiting operating points are considered for each of these topologies. The capacitor in the dc link, the MOSFETs in the inverting bridge, and the output filter are the components affected. Studies show that varying power-factor operation with a constant real power output increases the energy storage requirement as well as the capacitance required in the dc link in order to produce the double-frequency power ripple. The overall current rating of the MOSFETs and output filter must also be sized to accommodate the current for the apparent power output. Modeling of the inverter verifies the conditions for each of the components under varying reactive power support commands. It is shown that the production of reactive power can significantly increase the capacitance requirement, but the limiting reliability issue comes from the increased output current rating of the MOSFETs

Involvement of Industry in the National High Performance Computing and Communication Enterprise

We discuss aspects of a national computer science agenda for High Performance Computing and Communications (HPCC). We agree with the general direction and emphasis of the current program. In particular, the strong experimental component and linkage of applications with computer science should be continued. We recommend accelerating the emphasis on national challenges with more applications and technologies from the information, as compared to simulation areas. We suggest modifying the grand challenge concept to complement the current teaming of particular computer science and applications researchers. We would emphasize better linking of each application group to the entire (inter) national computer science activity. We express this in terms of a virtual corporation metaphor. The same approach can be used to involve industry in HPCC for both the consumers of HPCC technology (application industries) and producers---Independent Software Vendors (ISV) and the hardware system companies. We illustrate this approach with InfoMall, a HPCC technology transfer program funded by New York State. The federal program should have greater incentives for the involvement of both ISV’s and their products

Wireless Mesh Networks for Infrastructure Deficient Areas

International audienceProvision of internet access in infrastructure deficient areas is expected to bring profound economic and humanitarian benefit to developing countries. Notwithstanding, achieving this goal poses an economic and technical challenge. Due to technological and economical reasons cellular networks are regarded to be unable to deliver affordable distribution in the short term. Instead 802.11s wireless mesh networking standard is identified to be a more viable and affordable partial solution to deliver broadband internet in the periphery of developing countries. A general focus is the individual incentive to participate in a mesh network rather than reliance on organisational bodies. This paper designs an architecture and business model for a low cost, low range distribution of internet access. The technical architecture is evaluated using simulation and is found to be viable, but demands optimisation