COORDINATED OPERATION OF MICROGRIDS AND DERs INTEGRATED DISTRIBUTION NETWORK

Abstract

The deployment of renewable energy sources (RESs) is increasing in the current energy generation scenario due to economic and environmental concerns. This has shifted the generation from traditional fossil fuel-dependent to distributed ones, mostly by RES, known as distributed energy resources (DERs), for establishing local sustainability because of their proximity to load centers. These DERs, individually or in combination, can form a microgrid (MG), which ensures a cost-effective supply to their own consumers and to the demand of the distribution network by delaying investments in large power plants and reducing their dependence on the transmission network. In the future, many MGs and DERs are expected to get connected to the distribution network, requiring their independent, economical, and controllable operation. The diversified presence of these DERs within the MGs and distribution network cater to operation and management challenges for the system operators, i.e., DN operator (DNO) and MG operators (MGOs). However, their coordination introduces major challenges in developing a local power-sharing framework where the MGOs and DNO manage their surplus and deficit power collaboratively. This management is mainly depends on the power buying and selling prices offered to the MGOs to participate in local power-sharing framework. Generally, these prices are decided by the transmission network operator (TNO) considered as the wholesale electricity prices. However, these prices do not encourage MGOs to participate in a local power-sharing framework, further impacting the motivation to install RES-based generation within the MGOs or DNO. Also, the operational jurisdictions and distinct cost characteristics of the DERs at MGs (mDERs) pose significant challenges to their integrated and cost-effective utilization. Therefore, this thesis develops three local power-sharing frameworks established by the DNO for coordinated operation with MGOs. These frameworks mainly depend on the centralized and distributed operation of MGs and DER integrated distribution networks. These proposed frameworks employ a multi-period optimization approach to address the broader class of optimization problems of the integrated MGs and DERs while ensuring the economic operation of MGOs and DNO. In the first work, a pricing mechanism for local power-sharing i between DNO and MGOs is proposed, where MGOs declare their power surplus/deficit status with DNO at their economic operation. In return, the DNO derives buying/selling prices for MGOs based on their statuses. This framework incentivizes DNO by buying power from surplus MGOs and selling the same to deficit MGOs. It also incentivizes MGOs to sell (buy) their surplus (deficit) power to (from) DNO. This process encourages local power-sharing, which benefits their operation and motivates the existence of MGs. The proposed framework is also demonstrated during congestion in the distribution network due to the power-sharing with MGs. In the second work, a centralized model is formulated to optimize the utilization of DERs under different operational jurisdictions, introducing a pricing mechanism based on local and grid price signals. With this pricing mechanism and local power-sharing frameworks, the coordinated operation among the DNO, MGOs, and DERs is established. For the scheduling of mDERs, their participation in the local power-sharing framework is considered as per the operational jurisdiction, which is either operated by DNO or their respective MGOs. The proposed pricing mechanism enables the DNO-MGOs to buy and sell at local prices when their resources are available within the distribution network and MGs. Moreover, for the applicability of the local prices, the operating intervals are identified based on the power buying and selling between DNO-TNO and DNO-MGOs. This pricing mechanism incentivizes mDERs’ participation based on their operational jurisdictions and the power-sharing status between DNO-MGOs and DNO-TNO, ensuring their economic viability and reducing dependence on the TNO. Finally, the third work proposes a distributed coordination approach using the consensusbased Alternating Direction Method of Multipliers (c-ADMM) to ensure the balance between the DNO and MGOs at the point of their interconnection. Also, to encourage the participation of MGOs in the local power-sharing framework, an incentive-driven pricing mechanism is proposed, in which the incentive-driven factors are evaluated based on the slope of the price-demand curve. The proposed local power-sharing framework ensures the distributed operation of DNO and MGOs as well as incentives for the MGOs to participate in the local power-sharing framework and their economic operation. The above mentioned proposed frameworks are modeled considering the mixed integer ii linear programming problem and validated on two modified IEEE 33-bus and Caracas 141- bus distribution networks connected with MGs and DERs. Results show significant reductions in power procurement costs for the DNO from TNO, improved economic performance for MGOs, and effective utilization of DERs. The proposed frameworks ensure scalable, distributed coordination, making them suitable for future distribution networks. This work lays the foundation for transactive energy systems by bridging operational, economic, and coordination gaps between DNO and MGOs in a distributed energy landscape.