The Commitment of Interruptible Load to Ensure Adequate System Primary Frequency Response

The use of interruptible load (IL) resources to improve the primary frequency response (PFR) of an interconnected power system has been proposed and, for speed, it is likely that such resources would operate autonomously on local frequency measurements. The commitment of the resources, however, could be coordinated globally and frequently in accordance with the state of the system. This paper investigates the minimum cost commitment of IL resources to ensure the PFR of a system remains within specified limits. The binary integer programming problem considers the commitment cost of each IL resource and includes nonlinear frequency constraints specified by the transient stability simulation of the system. A method to estimate the contribution of an IL resource towards meeting a frequency constraint is proposed and incorporated into a solution approach that involves the iterative solving of a linear commitment problem. The sensitivity-based estimation method reduces the amount of computationally burdensome transient stability simulation required by the algorithm with little increase in the final solution cost. An IEEE 118-bus test case study with 1000 IL resources demonstrates the benefit of the estimation method.