Section: New Results

Estimation and control of quality of service in demand dispatch

Flexibility of energy consumption can be harnessed for the purposes of grid-level ancillary services. In particular, through distributed control of a collection of loads, a balancing authority regulation signal can be tracked accurately, while ensuring that the quality of service (QoS) for each load is acceptable on average. Subject to distributed control approaches advocated in recent research, the histogram of QoS is approximately Gaussian, and consequently, each load will eventually receive poor service. In [11], published this year in IEEE Transactions on Smart Grid, statistical techniques are developed to estimate the mean and variance of QoS as a function of the power spectral density of the regulation signal. It is also shown that additional local control can eliminate risk. The histogram of QoS is truncated through this local control, so that strict bounds on service quality are guaranteed. While there is a tradeoff between the grid-level tracking performance (capacity and accuracy) and the bounds imposed on QoS, it is found that the loss of capacity is minor in typical cases.

The previous designs for distributed control of TCLs ensure that the indoor temperature remains within a pre-specified bound, but other QoS metrics, especially the frequency of turning on and off was not limited. In [19], presented at ACM BuildSys 2018, we propose a more advanced control architecture that reduces the cycling rate of TCLs. We show through simulations that the proposed controller is able to reduce the cycling of individual TCLs compared to the previous designs with little loss in tracking of the grid-supplied reference signal.