Abstract: Techniques for detecting an island in a system including a node that is operatively coupled to a primary power source (e.g., grid) and one or more distributed power generation sources are disclosed. In one embodiment, a current pulse is included in the output of a distributed power source. The grid voltage is monitored at the node to determine if a pulse-related disturbance occurs. If the grid is present, no pulse-related disturbance will manifest. If grid is down, then a pulse-related disturbance will manifest. Detection of the pulse-related disturbance is used to signal island detection.

Abstract: The invention in the simplest form is a power conditioning and inverting system for improved and efficient power generation. In particular, the present invention is a modulated dc link scheme that dramatically reduces the switching frequency ripple across the PWM output filter inductor and provides cost, size, and weight reductions, as well as efficiency enhancements. In a preferred embodiment of the present invention, the DC-DC converter control takes a feedback signal proportional to the inverter output voltage. This feedback is “summed” into the primary DC-DC volts command thereby causing the dc bus/link voltage to vary at a multiple of the output fundamental frequency causing the DC link to become a signal at a fundamental frequency voltage with a dc offset. The tooth modulator DC supply tracks the AC output voltage, reducing the difference between the applied DC volts and the AC output volts, thereby reducing inductor core losses.

Abstract: The invention in the simplest form is a system for managing distributed power sources connected to a power grid. The present invention manages power flow to/from the power grid whether for a stand-alone power sourece or for local area utility grid or microgrid. When two or more power sources are interconnected by the local grid, each source has a power conditioning unit and a circuit breaker manager for controlling and regulating the electric flow to/from the grid. The individual power sources are able to independently draw power from the grid when required without extensive master control schemes. In a preferred embodiment the power sources are reformer equipped fuel cells and the heat from the fuel cell is used as a heat source for efficiency.