联网分布式发电系统规划运行研究

分布式发电（DG）与输电网联合供电成为电力系统发展趋势。输电系统与DG联合供电的规划、运行分析对满足可靠性条件下的经济供电尤为重要。文中针对远离发电中心、与输电系统弱连接的配电系统，为了满足负荷增长要求，以DG投资费用和向输电网购电费用最小为优化目标，分别对输电网正常运行且价格固定、考虑停运状态和实时电价3种典型输电网情况下联网DG系统进行规划。通过应用启发式算法，得到了各种情况下系统最优供电方案。根据不同情况下系统运行性能分析，定量讨论了输电网停运、实时电价以及可再生能源随机发电对分布式电源类型、容量等规划运行结果的影响，优化结果体现了联网DG系统联合供电优势。     

Impact of the penetration of distributed generation on optimal reactive power dispatch

Optimal reactive power dispatch (ORPD) is a complex and non-linear problem, and is one of the sub-problems of optimal power flow (OPF) in a power system. ORPD is formulated as a single-objective problem to minimize the active power loss in a transmission system. In this work, power from distributed generation (DG) is integrated into a conventional power system and the ORPD problem is solved to minimize transmission line power loss. It proves that the application of DG not only contributes to power loss minimization and improvement of system stability but also reduces energy consumption from the conventional sources. A recently proposed meta-heuristic algorithm known as the JAYA algorithm is applied to the standard IEEE 14, 30, 57 and 118 bus systems to solve the newly developed ORPD problem with the incorporation of DG. The simulation results prove the superiority of the JAYA algorithm over others. The respective optimal values of DG power that should be injected into the four IEEE test systems to obtain the minimum transmission line power losses are also provided.     

A technical evaluation framework for the connection of DG to the distribution network

Technical advances and institutional changes in the electric power industry have resulted in a constantly increasing penetration of distributed generation (DG) resources in the grids. For the connection of new DG installations to the network a variety of factors are taken into account, including technical requirements imposed by utilities to ensure that the DG station does not adversely affect the operation and safety of the network. In this paper, fundamental issues related to the interconnection of DG installations to the grid are discussed and evaluation rules are presented, which address power quality considerations and are suitable for application by electric utility and DG engineers. The attention is focused on the steady-state and fast voltage variations, flicker and harmonic emissions. The simplified evaluation procedures of the paper are largely based on the relevant IEC publications and reflect the current practice of several European utilities. A discussion of the interconnection protection requirements is also included in the paper.     

分布式电源接人配电网的规划研究

分布式电源的广泛应用,使得国家能源政策、能源规划等直接渗透到与分布式电源有关的电力系统规划中,并影响规划的决策过程。分析了分布式电源并网对电力系统的影响,综述了分布式电源并网准入功率的计算方法,分析了分布式电源的最优容量计算方法,探讨了分布式电源规划问题的研究方向。     

基于发电预测的分布式发电能量管理系统

随着电力市场和新能源发电的不断发展,研究分布式发电的能量管理技术对分布式发电系统的稳定、经济运行具有非常重要的作用。本文介绍了分布式发电系统的网络拓扑,阐述了分布式发电系统能量管理的基本策略和光伏阵列发电预测的工作原理,提出了一种新颖的分布式发电系统能量管理控制算法。该算法根据发电单元的输出电能预测和储能单元的实时状态确定运行模式,采用模糊控制实时调控系统能量流动的方向和幅值,实现了系统运行成本最优化。     

Distributed generation: a definition

Distributed generation (DG) is expected to become more important in the future generation system. The current literature, however, does not use a consistent definition of DG. This paper discusses the relevant issues and aims at providing a general definition for distributed power generation in competitive electricity markets. In general, DG can be defined as electric power generation within distribution networks or on the customer side of the network. In addition, the terms distributed resources, distributed capacity and distributed utility are discussed. Network and connection issues of distributed generation are presented, too.     

智能配电网研究热点

智能配电网是智能电网的重要组成部分。随着电力生产形式、传输模式和电能利用方式的变化,配电网发展和运营不仅经历着原有技术和设备的升级改造,同时也面临着分布式电源接入、电力市场改革和高新技术集成与应用等许多新的问题和挑战。从能量、信息、市场三个方面介绍了智能化配电网的典型特征,在此基础上指出了配电网在网络规划、自愈控制、态势感知、资产管理、信息通信、分布式电源及储能等方面的关键技术,提出了智能配电网技术发展路线,为相关研究提供了参考。     

Characterization of the loss allocation techniques for radial systems with distributed generation

In the restructured electricity industry, meaningful loss allocation methods are required in order to send correct signals to the market taking into account the location and characteristics of loads and generations, including the local sources forming the distributed generation (DG). This paper addresses the issues related to loss allocation in radial distribution systems with DG, with a three-fold focus. First, the key differences in the formulation of the loss allocation problem for radial distribution systems with respect to transmission systems are discussed, specifying the modeling and computational issues concerning the treatment of the slack node in radial distribution systems. Then, the characteristics of derivative-based and circuit-based loss allocation techniques are presented and compared, illustrating the arrangements used for adapting the various techniques to be applied to radial distribution systems with DG. Finally, the effects of introducing voltage-controllable local generation on the calculation of the loss allocation coefficients are discussed, proposing the adoption of a “reduced” representation of the system capable of taking into proper account the characteristics of the nodes containing voltage-controllable DG units. Numerical results are provided to show the time evolution of the loss allocation coefficients for distribution systems with variable load and local generation patterns.     

Efficient integration of distributed generation for meeting the increased load demand

Distributed generation (DG) can be integrated into distribution systems to meet the increasing load demand while expansion and reinforcement of these systems are faced by economical and environmental difficulties. This paper presents an efficient methodology for integration of DG power into distribution systems, in order to maximize the voltage limit loadability (i.e. the maximum loading which can be supplied by the power distribution system while the voltages at all nodes are kept within the limits). The proposed methodology is based on continuation power flow (CPF). The effectiveness of the presented methodology is demonstrated in a test distribution system that consists of 85 nodes with integration of different penetration levels of DG power. The proposed method yields efficiency in obtaining more benefits from the same amount of DG power, decreasing the losses and improving the voltage profile.     

高比例可再生能源电力系统结构形态演化及电力预测展望

在清洁化、低碳化和智能化的能源革命背景下,高比例可再生能源成为电力系统未来发展的一个突出特征,也导致了电力系统结构形态的巨变。文中对高比例可再生能源电力系统结构形态演化及电力预测方法进行了阐述。首先分析了电力系统结构形态的内涵及其要素,建立了其形态演化的驱动力综合模型,然后结合高比例可再生能源发展趋势,分析其对电力系统形态结构的影响,建立高比例可再生能源驱动的电力系统形态演化模型。围绕高比例可再生能源电力系统结构形态演化机理和复杂多重不确定性运行场景下的电力预测理论两个科学问题,分四个方面对其研究体系进行了详细阐述。     

分散式发电可作为应对电网大面积停电的重要措施

分散式发电是大电网系统的有益补充。介绍了分散式发电的基本概念、特点、运行方式,以及微型燃气轮机、燃料电池等分散式发电机组,分析了我国发展分散式发电技术的必要性和重要意义。针对我国南方地区电网大面积停电的教训．认为大电网系统和分散式发电系统相结合是提高电力系统安全性和可靠性、保障国家电力安全的重要措施。     

分布式发电技术及其对电力系统的影响

随着公平竞争的电力市场逐步建立,分布式发电将凭借其投资省、发电方式灵活、与环境兼容等优点拥有越来越大的市场份额。大量分布式发电系统接入电网,将对传统电力系统产生巨大的影响。首先介绍了分布式发电技术的基本概念以及其相对于集中发电方式的显著优点,并对现在比较热门的几种分布式发电技术做了介绍,然后分析了分布式发电对现有电力系统的影响,指出当大量分布式电源接入系统后,它对系统的影响不再局限于配电网,而将对整个电力系统的动态性能产生巨大的影响。     

Optimal corrective actions for power systems using multi-objective genetic algorithms

In this paper, optimal corrective control actions are presented to restore the secure operation of power system for different operating conditions. Genetic algorithm (GA) is one of the modern optimization techniques, which has been successfully applied in various areas in power systems. Most of the corrective control actions involve simultaneous optimization of several objective functions, which are competing and conflicting each other. The multi-objective genetic algorithm (MOGA) is used to optimize the corrective control actions. Three different procedures based on GA and MOGA are proposed to alleviate the violations of the overloaded lines and minimize the transmission line losses for different operation conditions. The first procedure is based on corrective switching of the transmission lines and generation re-dispatch. The second procedure is carried out to determine the optimal siting and sizing of distributed generation (DG). While, the third procedure is concerned into solving the generation-load imbalance problem using load shedding. Numerical simulations are carried out on two test systems in order to examine the validity of the proposed procedures.     

基于二阶锥规划的含DG与EV配电网分布式发电有功协调方法

分布式电源出力的不确定性与电动汽车充电的随机性给配电网运行效益带来一定的影响。本文根据分布式发电功率和电动汽车充电功率的不确定性,提出了分布式电源出力状态概率模型和电动汽车充电功率状态概率模型,在此基础上形成系统多状态运行空间,建立了含DG和EV配电网分布式发电有功协调模型。以期望的运行成本与期望的停电损失最小为优化目标。利用二阶锥规划,将目标函数和约束条件函数中的非线性形式通过旋转锥转换为线性形式,而新变量间则用特殊结构的锥集表示,从而简化了优化模型。以IEEE14节点的配电系统为例,对所研究的模型与算法进行了验证与分析,获得了较好的效果。     

Investigating distributed generation systems performance using Monte Carlo simulation

A novel algorithm to evaluate the performance of electric distribution systems, including distributed generation (DG) is proposed. This algorithm addresses the deterministic and the stochastic natures of these electrical systems. Monte Carlo simulation is employed to solve the system operation randomness problem, taking into consideration the system operation constraints. The uncertainties in the locations, exported penetration level, and the states (on or off) of the DG units constitute the random parameters of the studied systems. The introduced algorithm incorporates these parameters with the traditional Newton-Raphson solution of the power flow equations. Monte Carlo simulation is implemented to perform the analysis of all the possible operation scenarios of the system under study and thus ensure the validity of the results. The proposed algorithm is employed to obtain the hourly power flow solution for a typical DG connected system. The system loading follows several typical load curves based on load bus types. Furthermore, new hourly steady-state operating system parameters are evaluated to describe the system behavior under the DG random operation. The results obtained are presented and discussed.     

Distributed generation technologies,definitions and benefits

As a result of the application of deregulation in the electric power sector, a new identity appeared in the electric power system map known as “distributed generation” (DG). According to new technology, the electric power generation trend uses disbursed generator sized from kW to MW at load sits instead of using traditional centralized generation units sized from 100 MW to GW and located far from the loads where the natural recourses are available. This paper introduces a survey of this revolutionary approach of DGs, which will change the way electric power systems operate along with their types and operating technologies. Some important definitions of DGs and their operational constraints are discussed to help in understanding the concepts and regulations related to DGs. Furthermore, we will survey the operational and economical benefits of implementing DGs in the distribution network. Most DG literatures are based on studying the definitions, constructions or benefits of DGs separately. However, in our paper we aim to give a comprehensive survey by adding new classifications to relate the DG types, technologies and applications to each other.     

风力发电联网技术与经济效益分析

通过电力电子装置将风能发电接入电力系统是当前工程中普遍采用的首选方式,类似于将直流储能通过柔性交流输电(FACTs)与电力系统互联,所以带来了许多新的问题与挑战。结合北美工程界存在的具体接入方法,研究将风力发电接入电网的技术问题,以及风能接入后电力系统的运行与控制方式,并提供了一种评价分布式发电模式对系统稳定性影响的技术,结合具体实例进行了初步的可行性研究。同时还在市场环境下,对联网过程中的相关行为进行了经济分析。     

Hysteresis current control technique of VSI for compensation of grid-connected unbalanced loads

The global trends nowadays in the power generation industry are to supplement the electricity production using distributed generation (DG) technologies based on renewable energy resources such as photovoltaic, wind power, etc. However, failure to properly control the operation of distributed energy resources as they connect to the exiting power grid could provoke many power quality problems on the grid side. For this reason, due considerations must be given to power generation and safe running before DG units is actually integrated into the power grid. The main aim of this paper is to address the grid interconnection issues that usually arise as DG units connect to the electric grid. The proposed strategy, implemented in Matlab/Simulink environment in different operating scenarios, provides compensation for active, reactive, unbalanced, and harmonic current components of grid-connected nonlinear unbalanced loads. The simulation results obtained in this study demonstrate the level of accuracy of the proposed technique, which ensure a balance in the overall grid phase currents, injection of maximum available power from DG resources to the grid, improvement of the utility grid power factor, and a reduction in the total harmonic distortion of grid currents.     

A Petri net based protection monitoring system for distribution networks with distributed generation

Connection of distributed generation (DG) essentially changes distribution network operation and creates a range of well-documented effects varying voltage levels and short circuit currents. Among others, DG can alter protection system operations in distribution networks, leading to failure of reclosing, disconnection of healthy feeder or prevention of protection operation. This paper proposes a procedure, based on Petri nets and supported by a centralized monitoring architecture for monitoring failures of the protection systems in radial distribution networks. Some case studies applied to a real Italian distribution network proved the effectiveness of the proposed procedure that can therefore represent an effective solution to improve distribution systems reliability in presence of DG.     

An active control technique for integration of distributed generation resources to the power grid

This paper explores stability issues for integration of distributed generation (DG) resources to the power grid by power electronic converters. Application of power converters in power distribution systems is becoming more and more common. Stability study of this kind of systems is crucial because of the potential for negative impedance instability of interfacing converters. In addition, in a power distribution system, a converter can lead to local instabilities when interacting with other dynamic subsystems. In this paper, to investigate the stability of system, the impedance-based small-signal model of each of the subsystem is respectively achieved and then an active control technique is proposed to stabilize the system. The proposed method depends on reshaping the input impedance of the interfaced converter by injection of an active stabilization signal at the control loop of the converter. MATLAB/Simulink simulations are conducted to demonstrate the effectiveness of the proposed control technique during various operating conditions.