The unit commitment and economic dispatch problem in electricity markets has mixed-integer variables with piecewise linear bids. By using Lagrangian relaxation, a concave and piecewise linear dual problem is obtained.The resulting multipliers can be used to set prices in the convex hull pricing model, and this would result in the minimal uplift payment. This paper presents a subgradient-based cutting plane method to obtain the optimal multipliers in a computationally efficient way. The idea is to use subgradients to find an approximate center of the feasible polyhedron within the cutting plane framework. The time consuming process of finding centers such as analytic centers can thus be reduced. At nondifferentiable points, the cuts resulting from approximate centers may oscillate, and this difficulty is overcome by choosing a proper linear combination of these oscillating subgradients. The analytic centers are inserted as needed as spacer steps to ensure algorithm convergence. Testing results demonstrate the effectiveness of the algorithm.
With increased variable generation, the power grid operator faces more challenges in operation. This report presents several methods that the RTO developed to manage the uncertainties through better management of generation and demand. The results of an internal analysis indicate that clear benefits can be achieved through these enhancements. The RTO constantly reviews its operation and makes necessary improvements to add values to society by reliably operating the system in an economic way.Index Terms--security constrained unit commitment (SCUC), security constrained economic dispatch (SCED), rampable capability, wind generation, dispatchable intermittent resources, demand response program.
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