Considering cost and reliability in electrical and thermal distribution networks reinforcement planning

• A framework for composite electrical and thermal system expansion planning is proposed.
• The model helps planners to identify the installation of new elements or upgrading the existing ones.
• The main objectives are to minimize the costs and reliability.
• A new Improved Teaching Learning optimization (ITLO) algorithm is applied.

The concurrent expansion of both electrical and thermal energy distribution systems has been addressed in this paper. The EEP (energy expansion planning) is formulated as a multi-objective optimization problem which is subjected to reduced I&O (investment and operation) costs as well as to improve the system reliability. As a result, apart from the total costs, the reliability measures of SAIFI (system average interruption frequency index), SAIDI (system average interruption duration index), and AENS (average energy not supplied) have been included in the objective function. Moreover the ability of the system reconfiguration in enhancing the system reliability has also been employed as a failure rate reduction strategy. The proposed EEP problem tries to minimize the objective function with respect to system constraints by means of rewiring, network reconfiguration, installation of new lines and also new electrical/thermal generating units. Such complex large-scale optimization problem mandates the utilization of an effective optimization tool to find the global optimum solution. The well-known TLO (Teaching Learning Optimization) is the core of exploited optimization method, ITLO (Improved TLO), in solving the proposed static EEP problem. In order to evaluate the proposed algorithm, two modified test systems are used as case studies.