Photovoltaic systems provide electrical power with reduced emissions at competitive costs compared to legacy systems. A low or medium voltage dc distribution system is usually used for solar integration. In dc systems, parallel and series arc faults are a safety concern. Thus, reliable and timely detection and mitigation of arc faults are critical. DC arc detection methods typically use time or frequency spectrum variations of the circuit current or voltage to differentiate the arcing event from other system events. Since practical systems include power electronics and maximum-power-point tracking, any detection scheme must perform robustly in the electrical environment that these components establish in the dc power system. A capacitor placed in parallel with the main system is an effective sensor for series arc fault detection and localization applicable in this complex electrical environment. This article shows that the analysis of the amplitude, polarity, and spectrum characteristics of the capacitor current and voltage resulting from perturbations caused by the arc provides an effective method to identify and localize faults. The detection accuracy of the proposed approach is 98.3% and the localization accuracy rate is 100% for the correctly detected faults.

Urban transit agencies across the United States operate several types of services, including paratransit operations and fixed route fleets. The paratransit service operations are unique, since they do not run fixed routes and have relatively long passenger stops. During these stops, passengers onboard the vehicle must be kept comfortable, requiring operation of the heating, ventilation, and air conditioning (HVAC). In a conventional bus configuration, the engine must be idling to power the HVAC compressor and other accessories. Thus, the engine idle time in a paratransit fleet is a substantial portion of the daily operation. This paper describes a research program with goals of lowering paratransit bus emissions, improving fuel economy, and reducing engine idle time. The program concept is electrification of the bus accessories using a high voltage battery and alternator system. With the vehicle engine running, the high voltage battery is charged via the engine driven high voltage alternator. During vehicle stops, the engine can be turned off to reduce emissions, increase fuel economy, and reduce idle time while still having HVAC for passenger comfort powered from the high voltage battery. This paper will describe the modeling, design, installation, and testing phases of the vehicles.