Generation scheduling in non-interconnected islands with high RES penetration

Comparative Assessment of Priority Listing and Mixed Integer Linear Programming Unit Commitment Methods for Non-Interconnected Island Systems

“…Actual wind generation at t is given by Equation 3, determined by available wind power, limited by the minimum loading, Equation (4), and dynamic, Equation (5), limitations of conventional units, discussed in References [5,29,32]. The empirical coefficient l w represents in principle the fraction of wind generation that can be lost during operation and therefore needs to be covered by fast operating reserves, as discussed in References [7,29]. For the simplified PL-UC approach, where reserves types are not distinguished according to their deployment time, l w should be quantified more conservatively, so as to further incorporate wind power forecasting errors and variability.…”

“…The operating reserves policy adopted for the PL-UC variant relies only on system spinning reserve, a common practice adopted by NII system operators [13,29]. Constraint (7) estimates the conventional capacity to be committed, so that a spinning reserve of at least ε(%) (e.g., ε = 15%) of net demand to be maintained.…”

“…In this section the mathematical formulation of a MILP-based UC-ED optimization method is presented, as a more systematic and coordinated generation management for a NII system. The MILP optimization algorithm is based on Reference [29], aiming at minimizing NII system production cost and maximizing RES penetration, while guaranteeing secure operation via maintaining the required levels of active power reserves [33].…”

“…The objective function of the UC problem, given by (9), aims at minimizing the operating costs of conventional units (C p ), including start-up (C su ) and shut-down (C sd ) costs [34,35], and maximizing RES penetration. The latter is achieved by assuming in (9) zero cost for RES energy and further penalizing RES curtailments, as discussed in Reference [29]. The leftmost term of (9) reflects the variable operating costs of conventional units, that are generally approximated by a quadratic function [36] (grey line in Figure 2a), that can be piecewise linearized (dashed-black line in Figure 2) and incorporated in the MILP via Constraints (10) to (12).…”

“…Tertiary reserves requirements are calculated based on the variabilities of load and renewables for longer time scales (20 min), while accounting for forecasting errors as well. The quantification of secondary and tertiary reserves requirements is discussed more extensively in Reference [29].…”