Distribution System Model Research Articles

Multi-stage planning of clean resources and energy storage assets with hybrid uncertainty modeling for low-carbon resilient distribution systems

Climate change drives the urgent need for low-carbon and resilient energy system transitions. However, current planning methods ignore the inherent conflicts between carbon emission reduction and resilience enhancement, failing to optimally balance asset allocation for both aspects. They also neglect the long-term dynamic and stochastic nature of transitions, exposing systems to hybrid uncertainties. This paper presents a multi-stage dynamic planning method for clean resources and energy storage assets in power distribution networks. First, to facilitate low-carbon and resilient transitions, adaptive, stage-wise planning decisions are optimally determined under various planning strategies to mitigate risks stemming from hybrid uncertainties. Second, to precisely quantify the impact of hybrid uncertainties on decision-making, a systematic hybrid-uncertainty modeling approach is designed to capture short- and long-term uncertainties arising from both exogenous and endogenous factors. Third, to alleviate computational complexity, a decomposition-based stochastic dynamic dual integer programming method with augmented cut generation is introduced, which decomposes the original problem into stage-wise subproblems coordinated through forward and backward steps. Numerical results show that the proposed method generates cost-effective planning schemes, yielding $60 K in savings and reducing carbon emissions by 3853 tons. The method also demonstrates strong scalability, with a 52% reduction in solution time for large-scale planning problems.

Control valve simulation method integrable into the global gradient algorithm

ABSTRACT This paper presents a refinement of a method that simulates flow- and pressure-regulating valves by replacing them with pipes and adjusting the resistances (diameters) of those pipes to meet the valve settings. The method, referred to as the replacing pipe method (RPM), is readily integrable into the global gradient algorithm, which is the heart of the commonly used EPANET 2 water distribution system modeling software. The RPM proved to be more robust, yet slower than the EPANET 2 valve handling heuristics. In this work, the RPM was modified to increase its computational speed. The modification involved the RPM check valve handling algorithm and condition for updating the diameters of the valve-replacing pipes. The modified RPM was tested as part of a hybrid simulator, which switches from the EPANET 2 valve handling heuristics to the RPM when the former fails. The test networks included a large network with thousands of nodes, pipes, and valves, and a case of an ill-posed problem. As the testing showed, the modified RPM offers a significant reduction in the number of iterations compared to its previous version.

Dynamic Determination Method of Line Drop Compensator Parameters for Voltage Regulators Based on Mixture of Experts Using Real‐Time Information

In this paper, a method for determining line drop compensator (LDC) parameters for step voltage regulators and on‐load tap changers is proposed to avoid voltage violations in distribution systems with voltage fluctuations due to photovoltaic (PV) generation and electric vehicle (EV) charging. Distribution system operators need to effectively solve voltage problems caused by the widespread installation of distributed energy resources with the existing voltage regulators to construct an efficient and rational infrastructure. Our focus was on improving the method for determining the LDC parameters for the existing voltage regulators based on LDC control. A mechanism to dynamically change the LDC parameters depending on the situations in the distribution system was developed by using a mixture of experts, one of the machine learning techniques, and real‐time voltage and power flow information from information technology switches. The power flow calculations were performed using a distribution system model constructed based on the topology, loads, and generation characteristics of an actual distribution system in the Hokuriku region. The effectiveness of the proposed method was evaluated in terms of its improved effect on PV and EV hosting capacity, as well as the impact on the frequency of tap operations of voltage regulators. © 2024 The Author(s). IEEJ Transactions on Electrical and Electronic Engineering published by Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

A hierarchical framework for aggregating grid-interactive buildings with thermal and battery energy storage

The behind-the-meter (BTM) thermal and battery energy storage can help improve energy efficiency, reduce energy costs, and enhance energy resilience, particularly in rural areas and for disadvantaged communities. Aggregating numerous BTM energy storage systems can act as a price influencer with a significant source of load shifting and peak demand reduction. An integrated and scalable control mechanism is required to effectively utilize energy storage systems and flexible building loads to maximize the economic benefits, considering various distribution system constraints. This paper presents an innovative hierarchical coordination framework for energy storage and flexible load in buildings, considering various factors such as electricity prices, thermal comfort, and distribution system modeling and constraints. At the upper level, a distribution system operator optimizes the power flow to minimize its power procurement costs from the electricity wholesale market, while at the lower level, aggregators determine the optimal dispatch of battery and thermal energy storage systems in multiple buildings on behalf of end-users to minimize operating costs according to the power prices. These problems are solved using a game-theoretic approach through negotiations between the distribution system operator and aggregators as a bi-level decision model. Simulation case studies have been performed for a test distribution network with a number of building end-users using energy storage systems to quantify the performance of aggregators. The results demonstrate that the proposed strategy can reduce peak load for a reliable electricity distribution network while saving electricity bills for customers.

Development of Rice Distribution Model to Support Food Security in East Java Province

This study aims to analyze problems in food distribution from upstream to downstream and the efficiency of the distribution values of the food chain, and formulate an efficient food distribution system model in Pacitan Regency. A mixed method, which combines quantitative and qualitative analyses, was used. The first objective was analyzed with the fishbone diagram, the second objective with the value chain model, and the third objective with the Matrix of Alliances and Conflicts: Tactics, Objectives, and Recommendations (MACTOR). This study used primary and secondary data obtained from observations, surveys, in-depth interviews, and focus group discussions. Respondents consisted of stakeholders in agriculture and distribution channels, namely farm laborers, landowners, wholesalers, warehousing, brokers, agents, retailers, bankers / financial institutions, and information providers. The objectives associated with product flow included transportation, risk, price, distribution, profit. The results show that there are problems in the four areas of production, post-harvest, trading system, and institution. There are three food distribution systems in Pacitan East Java but the most efficient model is farmers-millers-retailers-consumers. Although farmers must allow more time to reimbursement, prices are more affordable for consumers. The results of stakeholder analysis found that the stakeholders with the highest competitiveness are retailers, agents, information and warehousing, while those with the lowest are farm laborers and landowners. The results of the convergence show that close relationship is observed between farm laborers, collectors, warehousing and landowners in Order One 1; between warehouses, landowners, and collectors in Order Two 2; and between agents and collectors in Order Three 3. This shows that collectors have the strongest potential to play the central role in the agricultural chain.

Analysis of Underground Distribution System Models for Secondary Substations

Analysis of Underground Distribution System Models for Secondary Substations

Multi-overlapping disaster rolling recovery of unbalanced distribution systems collaborated with repair crews and mobile power sources

Traditional distribution system recovery strategies can handle non-overlapping disasters, typically a single N-k failure, rather than multi-overlapping disasters. Multi-overlapping disaster refers to a scenario in which a system experiences multiple N-k failures, with a new N-k failure occurring before the system has been fully restored from the previous one. To address the recovery problem under multi-overlapping disasters, a rolling recovery model for unbalanced distribution systems that considers both repair crews (RCs) and mobile power sources (MPSs) is proposed. The proposed rolling recovery model can automatically optimize preceding recovery strategies based on the grid topology and the state of each resilient resource at the overlapping moment of each disaster. Case studies are conducted on the modified IEEE 33-node test system to demonstrate the concept of multi-overlapping disaster recovery. Compared to traditional methods that treat multi-overlapping disasters as multiple individual disasters, the case studies demonstrate that the proposed model can reduce load shedding by about 6.91 %, which verifies the effectiveness of the proposed methodology for updating recovery strategies at overlapping moments of disasters.

Linear optimal power flow model for modern distribution systems: Management of normally closed loop grids and on-load tap changers

Modern distribution systems face new challenges due to the rise of small-scale renewable energy resources and the electrification of energy demand. Additionally, the complexity of network management increases with the exchange of flexibility services between distribution and higher voltage levels. The system operator's role involves optimizing the planning and operation of the distribution network. In current scenarios, this includes managing flexibility resources (such as generators, demand response, and on-load tap changers) and implementing new operating strategies (such as closed-loop topologies and dynamic reconfiguration). This paper proposes a reformulation of one of the most used linear approximations of the Optimal Power Flow model for distribution networks. The novelty of this reformulation lies in integrating equations to handle tap-changing transformers with closed-loop/meshed network operation, while preserving the original linear formulation and computational tractability.

Mitigation of overvoltage in LVDC distribution system with constant power load using generic energy storage system

The operation of a high-speed DC circuit breaker can cause overvoltage transients in the Low Voltage Direct Current (LVDC) distribution system, especially when driving a constant power load (CPL). Without adequate damping, the destabilizing effect of the CPL can push the system towards instability. This paper proposes a novel approach to mitigate over-voltage transients caused by DC circuit breaker operation in the LVDC system using a generic energy storage system (GESS). The paper begins by introducing the concept, modeling, coordinated operation and practical application of GESS. GESS employs both power-centric storage, such as supercapacitors, to limit the switching over-voltage within safe limits, and energy-centric storage, such as batteries, to ensure the energy sustainability. A state-space model of a detailed LVDC distribution system with CPL and GESS is subsequently developed. Additionally, to ensure system stability, analytical expressions are derived to determine the required sizing of the power-centric storage under different case scenarios. Simulation analysis using MATLAB's Control System Toolbox validates that GESS can stabilize voltage transients and reduce overshoots within 10 ms. Moreover, the proposed GESS solution is proven to be more reliable and cost-effective than supercapacitor and hybrid energy storage solutions. It is also scalable to larger LVDC networks and adaptable to different load scenarios.

Optimal allocation strategy of SOP in flexible interconnected distribution network oriented high proportion renewable energy distribution generation

Focusing on the issues of high distributed generation in the distribution network, this paper presents an SOP capacity allocation method for flexible interconnected distribution networks based on sensitivity analysis. Firstly, the improved sensitivity analysis is used to determine the best SOP installation position; Then, the number of SOPs is set in advance, and the location and capacity of SOPs are optimized using the second-order cone programming algorithm, with the minimum annual cost of distribution network as the optimization goal. Finally, this optimization method is verified on the modified IEEE 33-node distribution system model. The results show that the application of the optimization strategy proposed in this paper can significantly reduce the annual operating cost of distribution network and improve voltage stability, and the proposed model can effectively adjust the location and capacity of SOP access, thus improving the economic benefits and reliability of active distribution network.

Electric Vehicle Cluster Scheduling Model for Distribution Systems Considering Reactive-Power Compensation of Charging Piles

With the increasing number of electric vehicles (EVs), their uncoordinated charging poses a great challenge to the safe operation of the power grid. In addition, traditional individual-EV scheduling models may be difficult to solve due to the increasing number of constraints. Therefore, this paper proposes a cluster-based EV scheduling model. Firstly, electric vehicle clusters (EVCs) are formed based on the charging and discharging preferences of EV users and the expected time for EVs to leave. Secondly, the EVC energy and power boundary aggregation method based on the Minkowski addition algorithm is proposed. Finally, for the sake of reducing user charging cost and distribution network energy loss, and smoothing the daily load curve, an EVC scheduling model for EV participation in grid auxiliary services is proposed. The optimization model includes the reactive-power compensation of EV charging piles. The simulation results show that the proposed EVC scheduling model can greatly reduce the solution time compared to traditional individual-EV scheduling model. The model has high potential to be applied to large-scale EV scheduling. The reactive-power compensation provided by EV charging piles improves the voltage quality of the grid and enables more EVs to be connected to the grid.

Aggregated model of an active distribution system for coordinated TSO–DSO fast frequency control

The growing integration of distributed energy sources (DERs) challenges the traditional independent operation of transmission system operators (TSOs) and distribution system operators (DSOs). The coordination between TSOs and DSOs becomes essential, as DERs not only offer local ancillary services but also enable the provision of these services at the distribution network level following disturbances in the transmission system. To enhance power system analyses in TSO–DSO coordination, the availability of reduced-order or aggregated models proves crucial, avoiding detailed modeling and reducing computational burden. Addressing the lack of reduced-order models capturing the dynamics of diverse distributed technologies and their control systems within a unified single-device model, this paper introduces a single equivalent device based on virtual synchronous machine (VSM) technology. This device effectively subsumes the frequency response of various DERs and loads. The proposed aggregation methodology undergoes validation on systems of different sizes and compositions of DERs. Results from simulated scenarios consistently demonstrate the accuracy and generalizability of the proposed aggregated model, irrespective of system size and included technologies.

Using 3D Printing for Teaching and Outreach

The water industry is a valuable and often overlooked asset to a functioning, successful society. Water utilities have dreams and nightmares about the communities they serve touring their treatment plants. To educate and benefit the public, consider using three‐dimensional (3D) printing to create models of water distribution and treatment systems.

Integrated Index Vector Method and Hybrid Ant Lion Chaotic Evolutionary Programming Optimization (HALCEP) Technique for Loss Minimization in Distribution System

Distribution system is the final section of the electrical power system, apart from the transmission and generation system. The distribution system acts as the interface that connects the high-voltage network to the low-voltage consumer service point. Consequently, the distribution system contributes the most of the overall losses in the electrical power system. Hence, evolutionary computation was introduced to accomplish a reduction of the previously said losses. The evolutionary computation involves optimization techniques to allocate distributed generation (DG) to the distribution system. Unfortunately, several optimization techniques are not capable of achieving accurate results and are trapped at local optima. This paper presents the Integrated Index Vector Method and Hybrid Ant Lion Chaotic Evolutionary Programming Optimization (HALCEP) technique for loss minimization in a distribution system. In this study, Evolutionary Programming (EP), Ant Lion Optimization (ALO) and HALCEP optimization engines are developed. The validation process was simulated on the IEEE 33-bus radial distribution system (RDS) model. Comparative studies were performed to gain a clear observation of the advantage of the developed HALCEP over the conventional EP and the ALO techniques, effectively showing its capability to outperform them.

A robust optimization method for new distribution systems based on adaptive data-driven polyhedral sets

In order to better describe the uncertainty of renewable energy output, this paper proposed a novel robust optimization method for new distribution systems based on adaptive data-driven polyhedral sets. First, an ellipsoidal uncertainty set was established using historical data on renewable energy output, and a data-driven convex hull polyhedral set was established by connecting high-dimensional ellipsoidal vertices; on this basis, an adaptive data-driven polyhedral set model was established to address the problem of high conservatism in the scaling process of convex hull polyhedral sets. Furthermore, a novel adaptive data-driven robust scheduling model for new distribution systems was established, and a column-and-constraint generation (C&CG) algorithm was used to solve the robust scheduling model. Finally, the improved IEEE-33 bus system simulation verification shows that the robust scheduling model for new distribution systems based on adaptive data-driven polyhedral sets can reduce conservatism and improve the robustness of optimization results.

A Stochastic Sequential Service Restoration Model for Distribution Systems Considering Microgrid Interconnection

A Stochastic Sequential Service Restoration Model for Distribution Systems Considering Microgrid Interconnection

DEVELOPMENT AND TRAINING OF LSTM MODELS FOR CONTROL OF VIRTUAL DISTRIBUTED SYSTEMS USING TENSORFLOW AND KERAS

DEVELOPMENT AND TRAINING OF LSTM MODELS FOR CONTROL OF VIRTUAL DISTRIBUTED SYSTEMS USING TENSORFLOW AND KERAS

A Decentralized Voltage Regulation Scheme Using Improved Volt‐Var Function of PV Smart Inverter

With the growing distributed PV installation rate in distribution systems, voltage regulation difficulties such as local voltage violations and fluctuations have become common. To solve the voltage regulation problems, the local voltage regulation method using volt‐var (VV) function is effective for its high regulation speed, high accuracy, and flexibility. However, there are still hurdles on real application, such as parameter setting difficulties, insufficient voltage fluctuation mitigation effect, and unfairness of reactive power generation between PV customers. To further improve the VV function, this paper proposes a PID closed‐loop based VV function and mode‐switching function of PV smart inverter (SI). To validate the proposed methods, numerical simulations were conducted using a 6‐feeder distribution system model based on the JST‐CREST 126 distribution feeder model. According to the simulation result, the proposed method can better mitigate the local voltage violation compared to basic VV function based on the VV curve, also improve the fairness between PV customers, while the total reactive power generation and tap operations increases for the aim of more adequate voltage regulation. © 2024 The Authors. IEEJ Transactions on Electrical and Electronic Engineering published by Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

The Hourly Peak Coefficient of Single-Family and Multi-Family Buildings in Poland: Support for the Selection of Water Meters and the Construction of a Water Distribution System Model

Taking care of water resources and minimizing water losses in water supply networks requires a broad approach to identifying and neutralizing operational problems. The correct selection of water meters to minimize apparent losses requires knowledge of the characteristic flows that may occur in the facility to which water is supplied. The research aimed to develop tools in the form of mathematical models and water consumption curves along with hourly water consumption coefficients to facilitate the process of selecting water meters for engineers and creating computer models of water supply systems. The research involved monitoring the flow of 76 single-family and multi-family buildings in four towns in Poland, followed by data analysis and development of tools supporting the selection of water meters and the construction of computer models of water distribution networks. High correlation coefficients of the studied variables indicate the results’ usefulness. Four models were developed to determine the maximum flow values in multi-family buildings (three models) and single-family buildings (one model) in the range of water meter diameters DN15-DN40. Characteristics of the average hourly peak coefficient (HPC) values were also developed, along with the range of changes in HPC values for single-family and multi-family buildings.

Stackelberg Game-based Coordinative Dispatch of EV Charging Stations and Urban Distribution Systems Considering Temporal-spatial Dynamic Traffic Flow

This paper proposes a Stackelberg Game-based coordinative dispatch model of electric vehicle charging stations (EVCSs) and urban distribution systems (UDS) considering temporal-spatial dynamic traffic flow. The model is formulated hierarchically and consists of an upper-level problem and two lower-level problems. Firstly, a detailed EVCS dispatching model considering both electricity prices and charging service prices is developed in the upper-level. Then the electricity pricing model of UDS and travel decision model of EV users are proposed in the lower model. Particularly, a temporal-spatial dynamic model is developed to capture the traffic flow evolution in urban transport network preciously. EVCS, UDS operator (DSO) and EV users can make decisions independently as different stakeholders. Finally, a multi-layer iterative framework is designed to capture the tripartite benefit equilibrium of distribution grid, EV charging stations, and EV users, and to realize the effective solution of the model. Numerical studies based on a modified IEEE 33-bus system demonstrate the effectiveness and accuracy of our proposed approach.