Energy saving HVAC system modeling and closed loop control in industrial and commercial adjustable speed drives

Over 40 percent of the world´s energy consumption and 21 percent of greenhouse-gas emissions originate in buildings. Heating, ventilating, air conditioning (HVAC) system is an integral part of the total building architecture. Since the potential for energy savings is enormous, the proliferation of using adjustable speed drives (ASDs) in everyday life is widespread. Even though the ASD technologies are mature, the physical insights of how ASDs are used in HVAC systems to achieve energy savings are not often described in published literatures. At overall system level, this paper provides valuable ASD, and HVAC models of a supply fan system and its closed loop control methodologies for practicing engineers. Although proportional, integral and derivative (PID) controllers dominate the process control landscape, they do have their limitations. When they fail to produce the desired closed-loop performance, they can be time consuming to troubleshoot. The PID tuning is arguably the most challenging aspect of configuring a PID controller. Two PID tuning methods (1. Zeigler Nichols; 2. Gain Margin and Phase Margin) are presented in the context of supply fan energy saving control using an ASD. The steady state and dynamic performances are compared. Theoretical and simulation models of the complete system have been built and validated through a 5.5kW, 380V, 50Hz ASD, induction machine (IM) and supply fan blower experimental establishment.