Quantifying the Effect of Air Conditioning Dynamics on Power System Stability Limits

Abstract

Dynamic load characteristics are becoming an increasingly important consideration for power systems with a large penetration of residential air conditioning. Residential air conditioner stalling in response to faults plays a large role in Fault-Induced Delayed Voltage Recovery events, which can degrade the operation of electric power systems. To further study this connection, this work seeks to tie load parameter variations directly to changes in assessed stability limits.

This connection is first considered at an area-wide level, before a bus-level locational sensitivity metric is introduced. Stability limits are assessed using PowerWorld for power flow and dynamic simulations with differing dynamic load model parameters. With the area-wide method, dynamic load model parameters are considered uniform for all busses, and individual parameters are varied one at a time to assess the effect on the assessed stability limit. For the locational sensitivity metric, only parameters for one bus at a time are varied. Both approaches are investigated for 2-bus and 2,000-bus test cases.

Using a practical definition of power system stability, test results allow some common assumptions about the effects of air conditioning motor stalling to be validated. For instance, it is shown that increasing the fraction of load composed of residential air conditioning can have a significant, negative impact on the assessed system stability limit, and that increasing the amount of residential air conditioning with undervoltage protection improves system response and stability. The locational sensitivity metric is used to identify which busses are most critical to the system response near the stability limit, and it provides a practical way of identifying which busses’ load model parameters may deserve further attention. The metric might also help justify the placement of dynamic reactive power support devices, such as static var compensators. These possibilities will be explored in future work.