Impacts of Lock-off Time on Virtual Battery Model from Thermostatically Controlled Loads

We examine through simulation the impacts of lock-off time of thermostatically controlled loads (TCLs) on their aggregated flexibility, which are characterized as a virtual battery (VB). The VB model provides a simple and general way to quantify the aggregated flexibility of TCLs, but the physical device operation constraints such as lock-off time are not considered. Many TCLs should not be immediately switched on after being turned off, and this lock-off time constraint affects not only the availability of individual TCLs but also the aggregated flexibility from a group of TCLs. In this paper, impacts of lock-off time on the efficacy of VB models are studied through simulations using both artificial and practical signals with low and high frequency. It is found that with the lock-off time, the VB flexibility changes little when following slow signals, but is much reduced when following fast signals.