In this paper, a novel contingency-aware method for N-2 security-constrained transmission expansion planning is proposed. To ensure that the transmission construction plan satisfies the N-2 security criterion, the proposed method takes advantage of the adjustable robust optimization (ARO) framework and upgrades it. We construct a discrete uncertainty set in which component failures are treated as uncertain events that are handled as binary variables. In addition to the failure of existing lines and generators, we explicitly model the failure of candidate lines. The proposed model comprises a master problem that makes the transmission construction decision, and a series of subproblems that can detect not only the worst contingency, but also the potential contingencies. Computational studies on the IEEE RTS 24-bus and IEEE 118-bus test systems are carried out to validate the effectiveness of the proposed method. Compared with the deterministic method and ARO method in the literature, the proposed method has higher computational efficiency.

Compared with traditional transmission network expansion planning, the exact life cycle cost is worth further studying. A three-dimensional life cycle cost (LCC) model for entire transmission network which consists of time dimension, component dimension and cost dimension is proposed. The device layer, the system layer and the cost of externalities of cost dimension are described and formulated in detail. The conditional value at risk (CVaR) of social welfare is established through optimal power flow calculation so as to take social responsibility into consideration. The multi-objective multi-stage transmission network expansion planning model is constituted with two objectives which are minimum LCC and minimum CVaR of social welfare. Four uncertain factors including wind power are considered and simulated through Monte Carlo method. An effective normal boundary intersection algorithm integrated with improved niche genetic method is presented to solve the proposed model. The case studies carried out on the 18-bus system and 77-bus system not only generate even distributed pareto set but also recommend the optimal planning scheme. The comparisons between the proposed scheme and existing method verify the feasibility and validity. Copyright © 2012 John Wiley & Sons, Ltd.

How to consider the differentiated inertia levels of each node during the retirement of coal-fired power units to ensure system frequency security is a current research challenge. This paper proposes a source-grid collaborative planning method that accounts for the differentiated inertia levels of network nodes during the coal-fired power unit retirement. First, a frequency response model based on a multi-machine equivalence approach and a differentiated inertia level model based on a virtual synchronous machine transformation approach for each network node are established, and a node inertia constraint model can be obtained. Next, the characteristics of coal-fired power unit retirement are analyzed. Subsequently, a source-grid collaborative planning model that considers the differentiated inertia levels of network nodes during the retirement of coal-fired power units is proposed. Finally, the feasibility and effectiveness of the coal-fired unit retirement and source-grid planning model are validated by the IEEE 24-node case and a real-region case. The case study analysis indicates that compared with the conventional planning scheme, the planning scheme considering the node inertia level constraints has less retired thermal unit capacity, more installed capacity of new thermal units, and a uniform distribution of inertia levels.