Dynamic filtering of stochastic solar resources using HVAC drive control — A determination of feasible bandwidth

This paper defines a bandwidth over which power electronic HVAC (heating, ventilation, and air-conditioning) drives can operate such that when integrated with stochastic solar power they act as an effective electric swing bus to mitigate solar power variability. In doing so, grid power is shown to be substantially more constant, reducing the need for fast grid resources or dedicated energy storage. The concept is equivalent to using building thermal energy as virtual dynamic storage in support of power grid operation. Two years of solar data have been collected on sub-millisecond time scales to test the results. Here a three-day sample is used to evaluate efficacy, determine solar frequency-domain content, and test a low-pass filtering concept introduced to model ideal power compensation. A more practical band-pass filter is realized that provides 1) lower frequency bounds such that the building maintains consistent room temperature via the HVAC system as demonstrated by a thermal modeling study, and 2) upper frequency bounds that ensure commanded HVAC fan speeds do not update arbitrarily fast. The latter primarily avoids acoustic discomfort to users. The combination is illustrated by experimental results based on various update rates of a variable frequency fan drive over a sample of actual stochastic solar data.