Enabling a Flexible, Non-disruptive Demand Control to Improve Grid Security & Performance

Iowa State University, Ames IA

Investigators

Abstract

As the penetration of smart controllable loads in the distribution system has been increasing, there has been a rising interest by utilities and ISOs to use these devices to improve the overall grid performance. Thermostatic controllable loads (TCLs) (heating, ventilation and air-conditioners (HVAC)) are rarely used for directly handling stability and security related issues. In this project, we systematically utilize the thermal storage of the HVAC systems to improve the security of the grid over various time scales (5 sec - 2 hrs). While we will concentrate on enhancing system stability, the proposed DR aggregation and control methodology can be utilized for other services (emergency reserves, spinning reserves, load shaping, etc.) in a manner that ensures the customer comfort is not disrupted. The research results will be disseminated at relevant conferences. Also, we plan to develop curriculum modules and short courses based on the research. The uniqueness of the Demand Response(DR) aggregator with set-point control is that it reduces the control cost of DR imposed by frequent switching and reduces the likelihood of involuntary service interruption, enabling a more flexible, aggressive, and smooth demand control for a broad range of applications. A time-varying Extended Markov Model (EMM) is used in an online manner to control temperature set points of TCLs by taking into account the customer discomfort. The EMM is complimented by a time varying model predictive control (MPC) scheme to ensure effective control of TCLs to follow the reference power. The proposed scheme effectively broadens the set of available tools and resources to save the system at the onset of a severe event. The proposed approach monitors real-time voltage stability margin (VSM) and predicts VSM in a nonstationary operating environment and ensures that the customer dissatisfaction is limited while ensuring voltage stability via demand side control. The novel detection of the location and proportion of HVAC stalling devices using phasor measurement units (PMUs) & micro-PMUs within 2-5 seconds ensures that relevant devices are selected for DR control, leading to an improvement in the short-term stability of the system. Also, to ensure that the reconnection does not induce synchronization of TCLs, an MPC formulation using EMMs is solved to determine the effective reconnection scheme. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.