A Fuzzy Optimization Model for Distribution System Asset Planning With Energy Storage

The distribution system asset (DSA) planning process for a new or existing subdivision involves a comparison of several feasible plans and selection of the least costly plan. The costs comprise the cost of new assets and their replacements, operation and maintenance costs, as well as reliability costs. DSA planning tools have been used for distribution utilities for decades, so that mature methods are available for traditional distribution systems. However, most of the DSA planning tools fail to include battery energy storage systems (BESS) as an asset solution for systems with high penetration of renewable energy sources. In addition, minimizing the investment cost and maximizing the reliability performance, which can be measured by the system average interruption duration index (SAIDI), are contradicting objectives. With a large investment, the system will have a small SAIDI, and vice versa. In this paper, a multi-objective algorithm that uses fuzzy optimization technique to handle these contradicting objectives is proposed. The algorithm includes traditional types of assets as well as BESS. One of the main advantages of the proposed method is that the customer interruption costs are not explicitly necessary, as these values cannot be precisely determined for all loads. In the tool, the annual investment cost and SAIDI are minimized, and the optimal size of BESS is obtained. Its performance is demonstrated on a 33-bus distribution system and the results are compared with other methods available in the literature.