Abstract: A system measures the stability of a live a.c. power distribution grid, without disrupting sensitive loads on that grid. The system applies repetitive time-synchronized loads to create current pulses, and resulting voltage instabilities, on the grid. The current pulses are sized to ensure that the resulting voltage instabilities are too small to affect the sensitive loads. Time-synchronized voltage measurement devices record the voltage instabilities. The time synchronization, and the repetitive nature of the current pulses, allow the voltage instabilities caused by the current pulses to be extracted from the larger background voltage variations.

Abstract: A variable-air-volume system for modulating the speed of a supply fan by measuring a plurality of inlet static pressures within the inlet of a corresponding plurality of terminal boxes within the system; calculating a plurality of setpoint errors equal to the difference between the plurality of inlet static pressures and a corresponding plurality of terminal box setpoint pressures; selecting minimum setpoint error out of all of the calculated setpoint errors; and modulating the fan speed as a function of the minimum setpoint error. The system can also utilize a power adjustment factor to modify the terminal box set point pressures.