Optimal Transmission Expansion Planning Research Articles

Transmission Investment and Expansion Planning for Systems With High-Temperature Superconducting Cables

Growing electric power demand in densely populated metropolitan areas presents problems due to the lack of availability of space to build transmission lines and due to short-circuit current limits. One of the solutions to meet the increasing demand is high-temperature superconducting (HTS) cables, which have a sufficiently high capacity and can be installed in the limited space of existing ducts. However, since the characteristics of low-impedance HTS cables result in higher system short-circuit levels, fault current limiter (FCL) HTS cables have been developed to solve the fault current problem without an upgrade of the rating of the existing circuit breakers, which is typically necessary when new power facilities in the power system are installed. This paper investigates the impacts of the installation of HTS cables on optimal transmission expansion planning (TEP). A three-stage TEP framework (identification, system analysis, and optimization) is proposed to select between plain HTS or FCL-HTS cables, and to determine the locations of new transmission expansion lines. The TEP optimization problem is formulated using mixed integer linear programming with the big-M method. The simulation results showed that the benefits of installing the FCL-HTS cable can justify their high installation costs.

Tri‐level transmission expansion planning under intentional attacks: virtual attacker approach – part I: formulation

The first part of this two-part paper proposes tri-level transmission expansion planning (TTEP) under physical intentional attacks. In the first level, the network planner looks for an optimal transmission expansion plan to fortify the power network. In the second level, the attacker tries to maximise damages to the network. In the third level, the adverse effects of the attacks on the network operation are minimised by the network operator. Since the third level problem is a linear programming (LP) problem, the second and third levels are converted into a single-level model by using primal-dual transformation, and consequently, TTEP is converted into a bi-level programming problem. To achieve a single-level model, instead of assuming a unique attacker, a cooperative game of multiple virtual attackers (VAs) of which every VA is to maximise the damage by attacking one transmission line is introduced and modelled. The conditions that enforce Nash and Pareto equilibria of this game are derived as linear constraints which are lower level equivalent. By using this equivalence, the aforementioned bi-level TTEP model is converted into a single-level model that can be recast as a mixed integer LP problem. The numerical results are provided in the second part.

Large‐scale transmission expansion planning: from zonal results to a nodal expansion plan

Performing optimal transmission expansion planning (TEP) in real, large-scale power systems such as the European one can be an unmanageable task, especially when long-term time scopes and multiple scenarios are considered. Project e-Highway had the daunting objective of planning the European network for the very long term and under high renewable energy penetration. The project objectives included the development of a planning methodology capable of applying optimisation to large-scale systems that are currently unmanageable in practice. This study presents this approach, which is based on simplifying the system while keeping its main features and investment drivers. The simplified system is then expanded optimally for the full time scope. Last, the original system is expanded optimally for the first time horizon taking into account the constraints imposed by the full time-scope optimisation of the simplified system. It illustrates the applicability of the method with a case study based on the European Union.

What is the value of the option to defer an investment in Transmission Expansion Planning? An estimation using Real Options

In deregulated markets, Transmission Expansion Planning (TEP) is usually performed by a central network planner seeking to maximize social welfare. In doing that, the network planner commonly follows a traditional project valuation, considering a discounted cash flow (DCF) methodology, although incorporating uncertainty and reliability considerations. Accordingly, once the optimal transmission expansion plan is determined, the network planner frequently auctions the needed investments, obligating the investor to execute the expansion in the fixed (inflexible) terms defined in the bidding process. A key problem is that DCF does not take into account the responses of the planner when uncertainties are resolved because DCF evaluates the project with the information available today. In TEP, managerial flexibility may be valuable because optimal decisions may change over time with the release of new information. Transmission investors may want to defer or expand according to such information. The aim of this article is to estimate the value of adding some flexibility in TEP through real options. In particular, by means of using a real-option approach with binomial trees, we study the benefits for a social network planner of having the option to defer some transmission investments. Our results suggest that incorporating flexibility in TEP may increase social welfare.

An efficient scatter search algorithm to solve transmission expansion planning problem using a new load shedding index

SUMMARY Transmission network expansion planning (TNEP) is one of the most important parts of power system studies. An optimal expansion of a transmission system should also capable of facilitating forecasted load patterns as well as future generation. Mathematically, TNEP is a mixed integer nonlinear programming as a non convex problem that can be solved by either conventional or heuristic optimization algorithms. This paper proposes a methodology for choosing the optimal transmission expansion plan considering less computational effort. The proposed methodology is composed from combination of Modified Scatter Search Algorithm and Constructive Heuristic Algorithm (CHA) considering New Load Shedding Index (NLSI). The proposed NLSI is implemented without generation rescheduling in order to decrease the number of linear programming obtaining an optimal solution. The algorithm is applied to different cases: Garver, 24-Bus IEEE systems and Southern Brazilian System of 46 Buses system. The simulation result shows a significant performance of the proposed method in comparison with some studies addressed in literature. Copyright © 2012 John Wiley & Sons, Ltd.

A Transmission Planning Framework Considering Future Generation Expansions in Electricity Markets

This paper proposes a transmission planning framework in a market environment in which only the generation sector is deregulated. The proposed framework is based on modeling generation companies' (GenCos') strategic behavior and anticipating their expansion patterns from the viewpoint of a transmission system planner. The transmission expansion planning problem in this paper is modeled as a four-level optimization problem. A solution method based on agent-based systems and search-based optimization techniques is proposed to determine the optimal transmission expansion plan.

A new mixed-integer methodology for optimal transmission expansion planning

This paper presents a new model and a solution methodology for optimal planning of high-voltage transmission network investments. The objective of this problem is to minimize capital costs needed for new network elements while meeting imposed operating constraints, and it is formulated via a linear mixed-integer model. Then, a new branch-and-bound methodology is proposed as the problem solution. The fundamental idea of this methodology is to reduce the number of discrete variables contained in the original set of unknowns. This reduction is achieved by using the decomposition principle and by developing a new separation of the region of feasible solutions. The proposed methodology was verified on several test examples, as well as on the real transmission network of the eastern part of former Yugoslavia.

Oscillatory Stability Considerations in Transmission Expansion Planning

Due to fast economic growth on the island of Taiwan, load demand in Taiwan Power Company (TPC) has been rapidly increasing in the past ten years and is expected to continue throughout the next decade. By 1995, the peak load demand in Taiwan is forecasted to reach 16,000 MW, an increase of 60% from the present level of 10,000 MW. Several new generating units have been under construction to meet the future demand. As a result, additional transmission lines are needed to avoid overloads on present lines. The objective of this paper is to report the results from a recent study which was aimed at reaching an optimal transmission expansion plan by comparing the relative merits of three feasible alternatives: EHV lines (345 KV), UHV lines (765 KV), and HVDC lines (± 250 KV). At present, the main factors considered in transmission expansion planning in TPC are the maximum power transfer limits, fault currents, transient stability, system losses, and cost [1]. In addition to these factors used in current practice, oscillatory stability of the power system under each expansion plan will be extensively studied. In particular, the low frequency electromechanical oscillations which tend to appear in a longitudinal power system such as the one in Taiwan will be investigated. The dampings of these oscillation modes are essential in system operation and planning, especially in the case when the transmission line is heavily loaded.