A multiagent approach to distribution system restoration

This paper proposes a multiagent approach to decentralized power system restoration for a distribution system network. The proposed method consists of several feeder agents (FAGs) and load agents (LAGs). LAG corresponds to the customer load, while a FAG is developed to act as a manager for the decision process. From the simulation results, the proposed multiagent system was able to reach the right solution by making use of only local information. This means that the proposed multiagent restoration system is a promising approach to more large‐scale distribution networks. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 152(3): 21–28, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20065     

A multiagent approach to power system normal operation

Recently, the electric utility industry worldwide has been facing pressure to be deregulated or restructured in order to increase its efficiency, to reduce operational cost, or to give consumers more alternatives. For this aspect, a great deal more research is needed to achieve a better, intelligent knowledge process. The present centralized system for power system control, operation, and planning must be remodeled to cope with these situations. With the promotion for the deregulation of the electric power system, the definition of the objective function for the optimization problem such as outage work operation for electric power systems is becoming critical. Currently, agents are an intense focus in many subfields of computer science and artificial intelligence. Agents are being used in an increasingly wide variety of applications. In this paper, we developed a power system normal operation application by multiagent architecture. Our multiagent system consists of several facilitator agents, equipment agents, and switch‐box agents. Facilitator agent acts as a manager for negotiation process between agents. Equipment agent corresponds to the element of the electric power system, such as bus, transformer, and transmission line, while switch‐box agent is the pseudo object which consists of neighboring current breakers and disconnecting switches. The proposed system realizes the appropriate switching operations by interacting with corresponding agents. The proposed approach is applied to a simple network, and the results show that the proposed multiagent system is an efficient decentralized approach for solving power system normal operations. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 146(4): 26–33, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10227     

A multi‐agent approach to unit commitment

This paper proposes a multiagent system to power system unit commitment problems. Multiagent is a new paradigm for developing software applications. Coordinating the behavior of autonomous agents is a key issue in agent‐oriented programming techniques today. Recently, agents are being used in an increasingly wide variety of applications, ranging from comparatively small systems such as E‐mail filters to large, open, complex systems such as air traffic control. Though some agent frameworks have been proposed in the power system field, the number of studies is limited. In this paper, we developed a power system unit commitment application by multiagent architecture. Our multiagent system has the following characteristics: (1) The system consists of a single facilitator agent, two mobile agents, and one or more generator agents which are elements of power system network. (2) The facilitator agent is developed to act as a manager for the process by using the singleton design pattern. The mobile agents migrate to generator‐agents to increase or decrease their power generations. The generator agents have their operational data. (3) Message object is developed to communicate between the agents using KQML‐like object. The proposed approach is applied to a simple model system, and the results show that the multiagent system is an efficient decentralized approach for solving power system unit commitment problems. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 141(2): 41–47, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10057     

A Multiagent‐Based Microgrid Operation Method

In this paper, we propose an autonomous microgrid operation using a multiagent approach. The proposed multiagent system consists of seven types of agent: a single microgrid controller agent (MGC), several load agents (LAGs), several gas‐turbine (gas‐engine) agents (GAGs), several photovoltaic generation agents (PVAGs), several wind‐turbine generation agents (WTAGs), several battery agents (BAGs), and a single grid agent (GridAG). In a microgrid, LAGs act as consumers or buyers, GAGs, PVAGs, and WTAGs act as producers or sellers, and BAGs act as prosumers or sellers/buyers. In order to verify the performance of the proposed system, it is applied to a simple model system with different electrical power prices. From the simulation results, it can be seen that the proposed multiagent system can perform microgrid operations efficiently.     

基于交替方向乘子法的电力系统分散式经济调度

现代电力系统中分布式电源特性各异,数量越来越多且接入具有分散特点,传统的集中式经济调度方法将面临计算负担大、通信复杂以及灵活性不足等限制。鉴于此,文中综合考虑了风电功率波动特性和分布式电源的动态模型及其综合发电成本,提出了一种基于交替方向乘子法的电力系统分散式经济调度方法。该方法在每次迭代过程中仅需收集系统净负荷及分布式电源平均有功功率,即可实现每台分布式电源有功功率最优值的分散式独立求解。最后,利用MATLAB/Simulink搭建了含有多个分布式电源的配电网系统,在风电功率波动和负荷实时变化的情况下对所提方法进行测试,通过与传统集中式经济调度方法的比较验证了所提分散式经济调度方法的准确性和有效性。     

含分布式电源的配电网多代理故障自恢复系统

提出一种完全分布式的多代理系统(multi-agent system,MAS),来实现包含分布式电源配电网的故障自恢复功能。该MAS由母线代理组成,每一个母线代理(bus agents,BA)都具备独立引导供电恢复的能力,通过BA之间的通讯与协作来完成供电恢复任务。为保障BA间通讯的有效进行,制定了深度优先通讯机制,该通讯机制与深度优先搜索类似。该MAS不仅能处理单一故障的情况,而且能处理连锁故障的极端情况。采用Java语言和多代理开发框架设计MAS。通过典型的故障算例验证了该MAS的有效性。     

Two-level optimal load–frequency control for multi-area power systems

In large-scale power systems, classical centralized control approaches may fail due to geographically distribution of information and decentralized controllers result in sub-optimal solution for load–frequency control (LFC) problems. In this paper, a two-level structure is presented to obtain optimal solution for LFC problems and also reduce the computational complexity of centralized controllers. In this approach, an interconnected multi-area power system is decomposed into several sub-systems (areas) at the first-level. Then an optimization problem in each area is solved separately, with respect to its local information and interaction signals coming from other areas. At the second-level, by updating the interaction signals and using an iterative procedure, the local controllers will converge to the overall optimal solution. By parallel solving of areas, the computational time of the algorithm is reduced in contrast to centralized controllers. This approach is applicable to any interconnected large-scale power system. However, for simulation purposes, a three-are power system is presented to show advantages and optimality of the proposed algorithm.     

考虑分布式电源支撑作用的输配电系统协同恢复方法

随着高密度分布式电源不断接入配电系统,配电系统向上支撑大电网恢复成为可能.首先,结合高密度分布式电源对电力系统分区并行恢复的促进作用,分析含分布式电源的大电网恢复分区需要满足的基本条件.然后,针对含高密度分布式电源的大电网待恢复子区,考虑相关运行约束等,构建输配电系统协同恢复的双层混合整数线性规划(MILP)模型.其中...     

A mathematical programming approach to service restoration for distribution systems

This paper aims to develop a suitable power system restoration method by using mathematical programming (MP). Generally, the problem of determining the target configuration can be formulated as a mixed integer programming (MIP) problem. Whether or not each branch is included in a target system is expressed as a 0–1 variable, while the other constraints such as the demand and supply balance conditions are formulated in terms of continuous variables. Although an MP‐based method can obtain an optimal solution under specified operational constraints, in the case of large‐scale problems the solution time often exceeds the computation time that is practically available due to combinatorial explosion. The object of this paper is to develop an efficient solution algorithm for service restoration in distribution systems. First, an MIP problem is solved to determine the sound network configuration that maximizes the available power to the out‐of‐service area, then an MIP problem is solved to determine the target configuration for the out‐of‐service network. The proposed method has been applied to distribution system restoration problems, and simulation results demonstrate its effectiveness. © 2001 Scripta Technica, Electr Eng Jpn, 135(4): 35–42, 2001     

A multiagent‐based microgrid operation method considering charging and discharging strategies of electric vehicles

In this paper, we propose a multiagent‐based microgrid (MG) operation method considering charging and discharging electric vehicles (EVs). The proposed system consists of five types of agents: single microgrid controller agent, several load agents, several gas turbines/engine agents, several photovoltaic generation agents, and several electric vehicle agents. In the proposed method, the load balancing can be realized by suppressing sudden fluctuations in supply and demand balance due to the synchronization of charging and discharging of EVs. From the simulation results, it can be seen that the proposed multiagent system could realize the load equalization in MG.     

Multiagent‐Based Electric Power Interchange between Microgrids

In this paper, we propose a multiagent‐based electric power interchange method between microgrids (MGs). The proposed multiagent system consists of eight types of agent: a single micro virtual power plant (MVPP) agent , several MG controller agents (MGCs), several load agents, several gas turbine (gas engine) agents, several photovoltaic generation agents, several wind turbine generation agents, several battery agents, and a single grid agent. In the proposed system, the MVPP plays an important role, facilitating electric power exchange between MGCs. Simulation results suggest that the proposed multiagent system could improve the load factor and reduce the MG operation cost.     

A Voltage Control Method for a Distributed Line Feeder by means of Multiagent Approach

This paper proposes a method for the coordinated control of power factor by means of a multiagent approach. The proposed multiagent system consists of two types of agent: single feeder agent (F_AG) and bus agent (B_AG). In the proposed system, an F_AG plays as an important role, which decides the power factors of all distributed generators by executing the load flow calculations repeatedly. The voltage control strategies are implemented as the class definition of Java into the system. In order to verify the performance of the proposed method, it has been applied to a typical distribution model system. The simulation results show that the system is able to control very violent fluctuation of the demands and the photovoltaic (PV) generations.     

考虑光储型电热协同系统灵活性的多代理削峰填谷策略

为解决光储型电热协同系统（electric-thermal system, ETS）协作参与电网削峰填谷问题,并减小负荷预测误差和新能源波动对调节效果的影响,提出一种多代理削峰填谷策略。该策略依托由配网代理、区域代理、ETS/光伏发电（PV）代理和执行单元构成的多代理系统实施,包含集中式能量优化和分布式能量管理环节。在集中式能量优化过程中,配网代理可通过求解以自身运行成本最小为优化目标的模型预测控制（model predictive control,MPC）优化模型,为区域代理及其内部的光伏系统提供日内有功功率上限计划。分布式能量管理过程中,区域代理和ETS/PV代理基于多智能体一致性算法获取供暖设备的有功功率修正值,从而减小实际区域代理有功功率与其计划值间的偏差。仿真结果表明：该策略可使系统协同参与削峰填谷且结果更精确。     

考虑多代理供电恢复系统通信失效的配电网CPS风险评估

提出一种考虑多代理供电恢复系统通信失效的配电网信息物理系统(CPS)风险评估方法。该方法将整个供电恢复过程分解为多个包含输入和输出的子任务,当通信系统失效时,依赖于失效通信链路的子任务将输出无效值,进而影响供电恢复的效果。通过计算不同供电恢复系统失效状态下的负荷缺额、恢复容量以及各个状态的概率,可以得到供电恢复后的电力不足期望值,并据此构建配电网CPS风险评价指标。通过计算并比较风险指标对各条通信链路丢包率的灵敏度大小,可以确定关键通信链路,并指出在通信系统的设计中应差异化提升这些通信链路的可靠性。最后,通过典型算例验证了所述方法的有效性。     

Market-based multiagent system for reconfiguration of shipboard power systems

On ships, the electric shipboard power system (SPS) supplies electrical power to critical functions such as navigation, communication, emergency systems, and in the case of warships, weapon systems. During ship operation, some parts of the SPS may become unavailable due to damage, fault, or maintenance. For the survivability and reliability of ships, it is desired to make the SPS highly reconfigurable. This paper presents a market-based multiagent system (MAS) for the reconfiguration of radial SPS. Radial SPSs are found on majority of ships. In the proposed MAS, each agent only communicates with its neighbor agents to make the system work in a fully decentralized manner. The MAS is implemented using Java Agent Development Framework (JADE), which is fully implemented in Java and compliant with Foundation of Intelligent Physical Agents (FIPA). An SPS with two generators and four loads is used for testing the proposed MAS. The results show the proposed MAS can successfully reconfigure a radial SPS.     

A decentralized control system for stabilizing multimachine power systems

A decentralized control system is studied for stabilizing multimachine power systems. A longitudinal power system with three areas, each having one machine, is considered in this study. A decentralized control design method is proposed, which is based on the optimal regulator theory. First a centralized control system is designed without any consideration on whether state variables are all available or not. Second a pseudo-decentralized control system is designed by omitting control gains corresponding to state variables which give hardly any effects on the power system stability. It is found that only one variable of phase angle of each machine is absolutely necessary for the pseudo-decentralized control system. This leads to an idea based on power system engineering, that is to say, new variables of tieline power flow are introduced in the decentralized control system design to substitute for the phase angle of each machine. Thus a decentralized control system for power system stability can be designed using the new variables of tieline power flow. It is demonstrated from simulation studies that the decentralized control system improves even longitudinal power system stability as well as the centralized control system.     

Optimal Decentralized Load Frequency Control

The paper presents a novel methodology for feasibility analysis and design of optimal decentralized load frequency control for multi-area interconnected electric power systems. Feasibility of the proposed decentralized control scheme is determined with a fixed mode evaluation algorithm based on eigenvalue dynamics. The eigenvalue sensitivity expressions are also used to determine decentralized feedback gains that will result in system transient performance similar to the one obtained with a centralized optimal control law. The methodology is illustrated with a two-area power system example.     

A Multi-Agent Solution to Distribution Systems Restoration

The goal to provide faster and faster restoration after a fault is pushing the technical envelope related to new algorithms. While many approaches use centralized strategies, the concept of multi-agent systems (MAS) is creating a new option related to distributed analyses for restoration. This paper provides details on a MAS that restores a power system after a fault. The development of agents and behaviors of the agents are described, including communication of agents. The MAS is tested on two test systems and facilitates both full and partial restoration, including load prioritization and shedding.     

Incorporating microgrids coupling with utilization of flexible switching to enhance self-healing ability of electric distribution systems

Electric distribution networks have to deal with issues caused by natural disasters. These problems possess unique characteristics, and their severity can make load restoration methods impotent. One solution that can help in alleviating the aftermath is the use of microgrids (MGs). Employing the cumulative capacity of the generation resources through MG coupling facilitates the self-healing capability and leads to better-coordinated energy management during the restoration period, while the switching capability of the system should also be considered. In this paper, to form and schedule dynamic MGs in distribution systems, a novel model based on mixed-integer linear programming (MILP) is proposed. This approach employs graph-related theories to formulate the optimal formation of the networked MGs and management of their proper participation in the load recovery process. In addition, the Benders decomposition technique is applied to alleviate computability issues of the optimization problem. The validity and applicability of the proposed model are evaluated by several simulation studies.     

事故备用分散转移的效益评估

由于可再生能源装机比例增大,传统机组预留大量事故备用,运行经济性显著降低。为此,首先提出了事故备用分散转移(DTCR)的概念:将原本集中在发电侧和电网侧的部分事故备用向用电侧分散转移。然后,提出了DTCR的效益评估方法和参考指标:观测到DTCR的边际效益递减现象可作为选取合理分散备用容量的参考;提出经济负载率阈值,可用于定量评估产生DTCR效益的经济负载率区间。最后,结合14节点至300节点等5个IEEE标准系统,并计及风机和需求响应的影响,分析了DTCR的效益大小、产生机理、影响因素和适用场景。结果表明,DTCR能够在日常调度中持续产生经济效益,优化潮流分布和降低网损。