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Coordinated Control of HVAC Systems
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Date
2001
Journal Title
Journal ISSN
Volume Title
Publisher
Energy Systems Laboratory (http://esl.tamu.edu)
Texas A&M University (http://www.tamu.edu)
Texas A&M University (http://www.tamu.edu)
Abstract
This paper describes the development of new control logic for starting and stopping energy-intensive
equipment in buildings such as staged air-conditioning units. The concept is to use pulse-width
modulation (PWM) instead of level-crossing logic. A finite state machine is used to handle the case where
a single unit has multiple stages of operation. An optimized coordinator determines the phase of the PWM
signals of each unit so that peak demand for power is minimized over each PWM period. Control logic
for the PWM function was developed so that the phase could be manipulated by the coordinator.
Computer simulations were used to assess the performance of the new strategy and to compare it to levelcrossing
logic. The following five metrics were used to assess the performance: 1) magnitude of the
control error, 2) start/stop frequency, 3) average power consumption, 4) standard deviation of the power
consumption, 5) peak power consumption. The computer simulations showed that the new strategy could
reduce peak power consumption by 20% relative to level-crossing logic. The computer simulations also
showed that the new strategy increased the magnitude of the space temperature control error by 11% and
increased the number of start/stop operations by 27% relative to level-crossing logic.