A Multi-Area Architecture for Real-Time Feedback-Based Optimization of Distribution Grids

Distributed energy resources (DERs) include distributed generations (DGs), distributed energy storages (DESs), and the demand response resources (DRRs). With the increasing penetration of DERs in distribution network, more and more users change from power consumers to prosumers which have great influences on distribution network as well as generate new business models on the demand side. Based on the emerging change of the power system, this paper proposes a transactive energy scheme (TES) based on multi-factor evaluation and contract net protocol to determine energy trading strategies among prosumers to realize economic and stable operation of distribution network. In the proposed TES, a TE market is built in the deregulatory retail power market. Power consumers, smart homes, industrial parks, or virtual power plants with DERs take the initiative as transactive nodes (TNs), and the peer to peer transactions among TNs in TE market can be carried out based on the multi-factor evaluation and contract protocol. When a TN cannot meet its own electricity demand, it launches the contract net to other TNs, requests to carry on the electric energy transaction, and determines the selected TNs according to the multi-factor evaluation. The simulation results show compared with the traditional electricity business model, the market participants who use the proposed TES can gain more economic benefits as well as protecting their own privacy.

FERC Order No. 2222 was issued to remove barriers to integrating distributed energy resources (DERs) into wholesale electricity markets and improve economic incentives for their adoption, which promotes benefits such as enhanced operational efficiency, reduced carbon emissions, and lower consumer costs. However, integrating DERs presents significant techno-economic challenges due to their unique characteristics compared to conventional generators. Existing wholesale markets primarily accommodate large generators connected to high-voltage transmission grids, neglecting the complexities of the unbalanced low-voltage distribution networks (DNs) that integrate DERs. Consequently, transmission operators cannot effectively assess the impacts of DER dispatch on distribution systems, potentially causing operational inefficiencies and pricing inaccuracies. To address these challenges, this paper develops a novel decentralized optimization approach utilizing reduced DN models, wherein DER market offers are aggregated based on their locations along the primary feeder of the distribution system into networks of virtual power plants (VPPs), thus facilitating coordinated transmission and distribution (T&D) operations. Additionally, a five-stage testbed is proposed to simulate coordinated T&D dispatch and evaluate solution performance across multiple scenarios. Simulation case studies on IEEE 6-, 118-, and 300-bus transmission systems integrated with modified 43-bus distribution networks have demonstrated the effectiveness and efficiency of the proposed framework, which obtains high-quality solutions requiring fewer deviations from scheduled dispatch levels compared to traditional methods, particularly for systems with interconnections between DNs.

P2P flexibility markets models to support the coordination between the transmission system operators and distribution system operators

A hierarchy model to use local resources by DSO and TSO in the balancing market

A competitive decentralized framework for Volt-VAr optimization of transmission and distribution systems with high penetration of distributed energy resources

Distributed energy resources (DER), such as rooftop solar and combined heat and power (CHP), create a unique opportunity to reduce transmission and distribution network capacity requirements, decrease electrical losses, and potentially improve reliability, resiliency, and other operating metrics. This dissertation examines how DER benefit different stakeholders in the electric power sector: DER owners, ratepayers, utilities, and society. In Chapter 2, we investigate how increasing commercial CHP system peak penetrations may affect net emissions, the distribution network, and total system energy costs. We find that small commercial CHP, due to low and inconsistent heat loads, can increase emissions relative to the bulk grid. We suggest policy options to encourage CHP operation during times of high heat loads. In Chapter 3, we develop metrics based on existing best utility practices that characterize how much solar can reduce peak demand on distribution network feeders. We conclude that solar can act as a capacity resource, but the size of the resource depends on the geographic region. Energy storage or an allowance for occasional overloading within a transformer’s tolerance can increase the capacity resource of solar. Chapter 4 is a value of solar and rate impact study for the Pennsylvania Public Utility Commission (PUC). The Pennsylvania PUC can use it to decide whether the environmental benefits of solar are worth the relatively small rate impact caused by rooftop solar. In Chapter 5, we assess the ability of rooftop solar and storage to reduce peak loads and defer distribution capacity projects in the PECO service territory. We find that targeted placement of solar can increase the total deferral value up to fourfold, but capacity deferral opportunities are rare and large administrative efforts to manage deferral projects, such as markets, are probably not warranted.

Distributed energy resources (DERs) provide various benefits to distribution networks, including the enhancement of reliability, resilience, sustainability, security, energy efficiency, and deferral of capacity upgrades, where each benefit should be valued individually. Accordingly, DER valuation which corresponds with its stated objective in a distribution network is viewed as a challenging task in electric power systems. This paper presents a method to calculate the valuable portion of installed DERs regarding their contribution to the network capacity upgrade deferral. The proposed approach will assign priority-based marginal values to existing DER locations in a distribution network and calculates the corresponding DER amounts for the deferral of capacity upgrades, which is based on respective locational marginal values. The proposed method utilizes the DistFlow method for DER valuation that considers branch flow constraints in radial distribution networks. The IEEE 33 and the modified IEEE 123 node distribution networks are studied in which several scenarios are analyzed to demonstrate the merits of the proposed method. The results provide additional insights on distribution networked-constrained DER valuation and demonstrate that the DER valuation can provide an alternative for deferring capacity upgrades economically in a distribution network.

Market-Based Coordination of Transmission and Distribution Network Planning with Distributed Energy Resources Planning

Smart grids have benefits such as high reliability and availability due to distributed energy resources (DERs) which are integrated to the power transmission and distribution grid. These DERs will maintain an uninterrupted power supply for electricity consumers in a case of isolation from the primary electricity grid due to failure of the system. The integration of DERs into the transmission and distribution grid introduces new consequence for distributed network operators (DNOs). In traditional electricity grid, power flow is happening normally from the bulk generation stations to consumers and all control operations are done at the centralized control station. In the modern electricity grid with DERs, the energy follows in both directions via substations due to randomly spread energy sources at the lower voltage side. Although distribution network was considered as a static system without major control operations or reconfiguration requirements. For a smart grid, distribution network can be considered as a dynamic system due to DERs. Power routing is an emerging concept. Its main purpose is to make the distribution network more flexible which will help to solve the technical issues related to DERs. With the introduction of DERs, DNOs have faced many challenges. Communication is one of major challenges in DNO Technology. Nowadays most of the communication architectures are based on the Internet that creates major security issues with the system. Cyber-security Enabled Communication Architecture is the most important concept for Power Routing. In this paper we introduce a cyber-security enabled communication architecture that facilitates the security for the information of an electricity grid.

Distributed energy storage system (DESS) has flexible operating characteristics, and DESSs can be properly configured to effectively serve the voltage regulation of the active distribution network. The existing voltage regulation-oriented DESSs optimization configuration studies are usually based on the balanced network model to analyze the impact of energy storage operation characteristics on the system voltage, but the distribution network is actually three-phase unbalanced. To this end, a method for the sequence optimization of DESSs in unbalanced distribution networks based on voltage sensitivity analysis is proposed, and the optimal configuration of DESSs in unbalanced distribution networks is studied from the perspective of improving the network voltage performance. Firstly, the DESSs placement is determined based on the proposed comprehensive voltage sensitivity analysis method; secondly, taking into account the economy of system operation, optimize the capacity of DESSs with the goal of minimizing the investment and operation and maintenance cost of DESSs, and the model solved by the improved grey wolf optimization algorithm. Finally, numerical simulations are analyzed by two unbalanced distribution testing networks. The results show that the proposed method can effectively improve the voltage profile of the unbalanced distribution network while ensuring the economy of system operation.

In this paper, a planning model for active distribution network (ADN) is proposed considering distributed energy resources (DERs) and distribution network expansion planning (DNEP) to cope with load growth and to maximize profits to the distribution system operator (DSO). The DERs considered in this paper include distributed renewable energy resources (RESs), distributed thermal generators (TGs), and battery energy storage system (BESS). DNEP options, such as adding new lines to the distribution network (DN) and upgrading existing lines are taken into account. The main motivation of this research is to find the optimal sizing and siting of DERs with considering DNEP to meet the load growth requirements and to maximize the total payoff to the DSO. The DSO trades energy externally with an independent system operator (ISO) at the market-clearing price (MCP) and internally with consumers at a predetermined cost. The overall performance of the proposed model is investigated on a 38-bus radial distribution test system. Simulation results indicate that considering DERs contributes to maximizing the total payoff to DSO and meeting the load growth requirements. In addition to that DERs can relieve the congestion in the DN's lines; therefore, it can mitigate or postpone DNEP's investment.

This paper presented a mixed-integer second order conic programming (SOCP) model for the distributed energy storage system (DESS) planning in the distribution network. Aimed at minimizing the present value of total investment of DESSs and operation costs of distribution network with high DG penetration, active and reactive power regulation and reconfiguration of the distribution network in different periods were investigated simultaneously. The proposed model used second order conic relaxation to enlarge the feasible region and make the optimal problem convex. Effectiveness of the model was tested on the Wulong distribution network, which is a practical network with high hydroelectric penetration. Result of DESS planning in the distribution network was compared with the simulation of distribution network operation without DESSs. Besides, the effectiveness of SOC relaxation was verified.

This paper proposes an equivalencing‐tracking‐based (ETB) method to incorporate distributed energy resources (DERs) in transmission system economic dispatch (TED). This method has three key steps. The first is a ‘dispatch model equivalencing’ step in which an equivalent dispatch model is created by an aggregator or a distribution system operator (DSO) to represent the aggregate operational features of the numerous DERs on the distribution side. In the second step, the equivalent dispatch model is sent to the transmission system operator (TSO) who then solves a DER‐equivalent‐included TED problem. The optimal solution regarding the DERs' equivalent dispatch model is returned to the aggregator, who will, in the third step, solve an optimal tracking problem to provide each DER with an optimal dispatch scheme that best tracks the optimal solution regarding the equivalent model. Case studies on a real power system confirm that the transmission system operation benefits from DERs' being incorporated in TED, and also that the proposed method can attain a nearly optimal solution without repeated iterations between TSOs and DSOs, which is a notable advantage over mathematical decomposition methods.

The FLEXGRID project develops a digital platform designed to offer Digital Energy Services (DESs) that facilitate energy sector stakeholders (i.e. Distribution System Operators - DSOs, Transmission System Operators - TSOs, market operators, Renewable Energy Sources - RES producers, retailers, flexibility aggregators) towards: i) automating and optimizing the planning and operation/management of their systems/assets, and ii) interacting in a dynamic and efficient way with their environment (electricity system) and the rest of the stakeholders. In this way, FLEXGRID envisages secure, sustainable, competitive, and affordable smart grids. A key objective is the incentivization of large-scale bottom-up investments in Distributed Energy Resources (DERs) through innovative smart grid management. Towards this goal, FLEXGRID develops innovative data models and energy market architectures (with high liquidity and efficiency) that effectively manage smart grids through an advanced TSO-DSO interaction as well as interactions between Transmission Network and Distribution Network level energy markets. Consequently, and through intelligence that exploits the innovation of the proposed market architecture, FLEXGRID develops investment tools able to examine in depth the emerging energy ecosystem and allow in this way: i) the financial sustainability of DER investors, and ii) the market liquidity/efficiency through advanced exploitation of DERs and intelligent network upgrades.

The reliability of an electrical network is essential in providing uninterrupted power supply to consumers. To achieve a high level of reliability, Singapore's underground medium voltage network utilizes several protection schemes that co-exist and function simultaneously to ensure that the distribution grid minimizes or if possible, eliminates any downtime for consumers. Distance protection is one such scheme that is commonly integrated within transmission networks to identify and isolate faults. It is particularly effective for transmission systems with long cable spans, as well as ensuring fast fault isolation while maintaining selectivity, as only the affected section is disconnected and isolated from other functioning parts of the overall network. Due to its niche usage in the transmission network, distance protection is typically not implemented within distribution networks, as it comprises shorter spans and denser cable layouts as compared to transmission networks. Nonetheless, distance protection could still prove to be potentially useful in distribution systems, especially with the increasing adoption of distributed energy resources (DERs) like solar, wind, and battery storage. This study aims to analyse the feasibility of implementing distance protection within Singapore's distribution network. It focuses on two main criteria: the specifications of existing equipment, such as the voltage and current sensitivity of distance relays, and the implementation costs. By addressing these factors, this study seeks to evaluate whether distance protection can be used to improve the reliability of distribution networks in an increasingly complex power system.