A study on cooperative tap control method for voltage profile maintenance in distribution networks with distributed generators

The introduction of distributed generators (DGs) that can utilize renewable energy is of prime importance to solve the energy and environmental issues. When a distribution network has a large number of DGs, voltage maintenance becomes a serious problem. To solve this problem, we had proposed the ‘voltage profile control method’ using reactive power control of DGs. However, the control is limited to continuous reactive power control so far, and tap control has not been considered. It is important that the conventional voltage control equipment such as the load ratio tap changer (LRT) or step voltage regulator (SVR) is utilized in order to enhance the control efficiency of the voltage profile control method. Therefore, in this paper, we develop a new method that can realize a cooperative work between inverters and tap control of LRT and SVR. The proposed method is tested in 8‐ and 24‐node model systems and its effectiveness is shown. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

含分布式光伏的主动配电网电压分布式优化控制

针对高比例分布式光伏接入配电网所带来的电压越限问题,提出一种含分布式光伏的主动配电网电压分布式优化控制策略.根据配电网支路潮流模型和光伏逆变器控制模型,构建以节点电压偏差、光伏削减量和网损最小为目标的主动配电网电压优化控制模型;利用二阶锥松弛技术对所构建的模型进行凸化处理;针对集中式优化控制存在计算复杂度高和信息私密性...     

A study of centralized voltage profile control of distribution network considering dynamics of distributed generator

In a future distribution network, it will be difficult to maintain system voltage because a large number of distributed generators are introduced into the system. The authors have previously proposed a voltage profile control method using power factor control of distributed generators. When all information on the system is available, an ideal stationary solution of control orders to distributed generators is given by an optimization calculation. However, it is difficult to apply optimization control in real time because a long calculation time is required for the optimization. Therefore, it is possible that a voltage change may occur before the power factor control has finished. Thus, in this paper, we develop a new control method which can save the excessive voltage changes by taking into consideration the controlled response time of distributed generators. The proposed method was tested in a 24‐node distribution network model. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 179(1): 29–39, 2012; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21231     

一种低压微电网中的分布式电压控制算法

为了实现电压调节和提高供电能力,提出了一种在低压微电网中利用分布式电源(Distributed Generators,DGs)发出的有功来进行电压控制的分布式电压算法。针对低压微电网的线路阻抗特性,分析了电压和有功的关系。由系统线路结构建立通信链路,并对电压超出上下限的母线初始化,计算出所需补偿的有功功率。基于本地信息,利用参数化状态转移矩阵对电压进行修正,并考虑了分布式电源的有功容量限制。通过该算法协调和分配各分布式电源所需承担的功率,共同作用实现电压控制。仿真结果表明该算法能够有效实现电压调节和减小电压偏差,提高电压质量。     

Active coordinated operation of a distribution network system for many connections of distributed generators

Recently, the total number of distributed generators (DGs) such as photovoltaic generation system and wind turbine generation system connected to an actual distribution network has increased drastically. The distribution network connected to many distributed generators must be operated keeping reliability of power supply, power quality, and loss minimization. In order to accomplish active distribution network operation to take advantage of many connections of DGs, a new coordinated operation of distribution system with many connections of DGs is necessary. In this paper, the authors propose a coordinated operation of distribution network system connected to many DGs by using newly proposed sectionalizing switch control, sending voltage control, and computation of available DG connection capability. In order to check the validity of the proposed coordinated operation of distribution system, numerical simulations using the proposed coordinated distribution system operation are carried out in a practical distribution network model. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 167(3): 46–57, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20655     

Influence of distribution voltage control methods on maximum capacity of distributed generators

Recently, the number of distributed generators (DGs) connected to distribution systems has been increasing. It is important to know how large a generator output is permitted when the generators are connected to a distribution system with regulation of the line voltage, the line current, and the power factor of the generator connection point. The authors demonstrate differences of maximum output of the DGs caused by various voltage control systems in a short‐length system and a long‐length system by load flow calculation. The voltage regulation systems include the following six types: no control equipment, SVC (Static Var Compensator), existing SVR (Step Voltage Regulator), reverse flow type SVR which operates even in reverse flow, existing SVR and SVC, and reverse flow type SVR and SVC. A synchronous generator is considered as a DG in this paper. The calculation results show that the DG's maximum output is about 3300 kW in a short‐length system and about 540 kW in a long‐length system. However, the DG's maximum output increases to about 3750 kW on installing a SVC, and the SVC's capacity decreases on replacing an existing SVR with a reverse power flow type SVR in the long‐length system. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 150(1): 8–17, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20050     

Extended flow algorithm for online reconfiguration of large‐scale distribution system with interconnected distributed generators

The interconnection of distributed generators (DGs) in a power system increases the difficulty of managing the system. The minimization of the voltage deviation by network reconfiguration is an important requirement for dealing with the issue. We had previously developed a reconfiguration technique, named the intelligent flow algorithm (IFA), for determining the optimum or suboptimum network configuration within a short computation time. In the present paper, we propose an extension of IFA, named the extended flow algorithm (EFA), for more effective determination of the optimal network configuration of a distribution system containing massive installations of DGs. EFA is a two‐stage method in which the configuration that produces uniform power supply, referred to as the balanced configuration, is first generated, and then used to seek the optimal configuration using an improved branch exchange approach. Accordingly, EFA is more simplified to improve its computation speed on large‐scale systems. The algorithm was tested by case studies of different test distribution systems in the MATLAB environment, and was confirmed to have high performance to cope with DG installations and large‐scale systems. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

含分布式光伏发电的中压配电网电压控制策略

随着分布式光伏发电并网规模的不断扩大,由光伏发电功率与负荷之间不平衡引发的逆向潮流导致的电压越限问题日益受到关注。在光伏接入点的电压分析及无功/有功调压分析的基础上,提出了无功/有功协调控制策略,通过光伏逆变器的无功输出补偿及光伏发电量优化管理,实现配电网节点电压的控制。仿真分析结果表明,该策略能在兼顾光伏利用效率和经济性的同时,较好地解决含分布式光伏发电的配电网的电压越限问题。     

Study on voltage regulation methods for distribution systems with dispersed generators

Connection of a large number of the dispersed generators to distribution networks is not easy due to various technical considerations. Thus, we have been trying to devise a concept for future electrical distribution systems with many dispersed generators. In this work, it has been considered that each customer's load and each generator's active and reactive power should be controlled in order to stabilize and optimize the networks. Under this consideration, two control methods for future distribution systems are proposed, a cooperative control and an independent control. We have confirmed experimentally that the voltage regulation ability is higher with the cooperative control than with the independent control, especially in cases of an eccentric load profile in a feeder and a heavy load. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 154(4): 16–23, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20246     

An optimal allocation of distributed generation and voltage control devices for voltage regulation considering renewable energy uncertainty

Distributed generation (DG) may result in voltage fluctuation by changing line flow and reactive power injection, especially DG that generates power from renewable energy resources. To cope with this problem, this paper proposes an optimization process to optimally regulate the system voltage profile to lie close to the desired values by using the adaptive Tabu search (ATS) algorithm. The system voltages will be regulated by using dispatchable DG and voltage control devices, i.e. voltage regulator and capacitor. Moreover, probabilistic load flow calculation by using Monte Carlo simulation is chosen to evaluate the uncertainty of DG powered by renewable energy resources. The number of switching operations of the voltage regulator and capacitor are also accounted for in the optimization constraints, as excessive frequent switching operations can damage these devices. The optimal sizes and locations of dispatchable DGs and capacitors are considered as the optimization variables. The proposed method is demonstrated in an IEEE 34‐bus distribution test system and a modified 21‐bus Provincial Electricity Authority (PEA) system (Thailand). © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

A study of autonomous reactive power control method for distributed power generators to maintain power quality of the grid

Distributed power generators, such as cogenerators and renewable energy systems, have continued to advance and their penetration capacity is increasing. However, they may cause power quality problems in voltage regulation because of the reverse power flow. At present, when the distribution line voltage exceeds the limit value, distributed generators control reactive power to reduce the voltage, and if the reactive power output is not enough, they reduce the active power output. Therefore, an imbalance of active power output between distributed generators may occur because the voltage of generators varies by location and generators at lower voltage locations do not control the reactive power. A power control method for distributed generators needs to be established to solve these problems. In this study, an autonomous reactive power control method of sharing reactive power between distributed generators is proposed. The availability of this method is discussed experimentally and its applicability area is considered analytically by use of a model distribution system. © 2006 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

考虑分布式电源详细模型的配电网多相状态估计

在传统配电网状态估计中,主要考虑拓扑约束和线性阻抗元件约束。在大量分布式电源接入配电网后,关于负序和零序的控制也相应增加。对于三相不平衡的状态估计,除了线性阻抗元件约束外,还要考虑分布式电源对不平衡分量即负序和零序的约束方程。因此,首先建立了常见的分布式电源在状态估计中的模型,然后提出了基于改进节点法的配电网多相状态估计方法,最后通过算例分析考虑与不考虑分布式电源的模型对状态估计结果的影响。     

含逆变型分布式电源的花瓣型配电网故障定位策略研究

针对含逆变型分布式电源(Inverter Interfaced Distributed Generation, IIDG)的花瓣型配电网的故障定位问题,文中提出了一种基于电气参数的综合故障定位方法,可用于解决三种不同类型的故障问题。对于两相短路故障,采用基于负序电流相位差的故障线路识别方法;针对单相接地故障,基于零序分量推导出测距方程,并利用区段线路长度约束排除虚假根,准确确定实际故障位置;对于对称故障,利用多线路正序电流的相位和幅值来确定故障位置;利用PSCAD/EMTDC系统对所提出的方法在不同故障情景下进行了故障距离和接地电阻测试。结果表明,与其他方法相比,所提方法定位精度更高,在不同故障类型下的定位误差不超过1%,从而验证了该方法在含IIDG的花瓣型配电网中具有更高的精度和抗故障能力。     

分布式光伏并网对配电网电压的影响

分布式发电以其经济、环保的优势在飞速发展,其中分布式光伏电源发展最为迅速。分布式光伏接入配电网,具有很大的随机性,对配电网系统的电能质量、短路电流、电网损耗、谐波等方面产生显著影响,重点分析对配电网电压的影响。通过理论分析分布式光伏接入点的位置、光伏接入容量以及馈线长度对配电网电压的影响,并通过仿真验证其成正比关系,最后提出解决对策,有利于深入研究分布式光伏接入对配电网的影响。     

Three‐phase voltage control method by single‐phase distributed generators connected to islanded distribution network

We have proposed a concept model of emergency islanded operation by using distributed generators (DGs) such as photovoltaics, electric vehicles, or batteries, which can provide power to customers via undamaged distribution network in order to develop the resilient power system against large disasters, and it is named Islanded Distribution Network (IDN). Since there is no guarantee that the three‐phase generation system is interconnected to the IDN, the single‐phase DGs that are installed in the distribution network may be treated as main generators in the IDN operation. If the IDN has only single‐phase DGs, it is difficult to regulate the three‐phase voltage within the allowable range and to compensate the unbalance voltage. The aim of this study is to develop the method to supply three‐phase balanced voltage by single‐phase generators in the IDN. First, the operating condition of the generators is proposed for the supply of three‐phase balanced voltage in the IDN model by algebra calculation. The control method for three single‐phase generators has been developed by using the conditions obtained from the derivation of the generators conditions.     

分布式电源准入容量对电力系统的影响分析

探讨了不同电压调整方法对分布式电源接入系统后准入容量的影响并进行了仿真模拟,运用二分法算法,结合IEEE-112节点系统的算例对各种模型进行了求解并分析计算了分散电源事故解列前后的准入容量,证明模型的合理有效性.     

含分布式电源的配电网电压越限薄弱环节识别方法

提出一种含分布式电源(DG)的配电网电压越限薄弱环节的识别方法。对电压越限原因进行机理分析,确定导致电压越限可能的原因及其电压敏感度;定义压降比系数,提出计及网损的各节点DG/负荷最大准入容量的计算方法;研究将各节点实际接入DG容量归算至馈线末端的方法,并将其与馈线末端的最大准入容量进行比较,识别配电网中易发生电压越限的薄弱节点及越限原因;在MATLAB上搭建IEEE 33节点系统验证所提方法的有效性和正确性。     

含分布式光伏和电动汽车的主动配电网电压一致性协同控制

分布式电源渗透率的快速增加使得低压配电网中出现严重的电压问题,而电动汽车(Electric Vehicle,EV)的广泛应用使得其参与电压控制成为了可能。提出了一种利用电动汽车的电池能量管理和分布式光伏阵列的无功、有功控制,来调节光伏发电渗透率较高的配电网中的电压。考虑到电动汽车电池容量和荷电状态(SoC)的不同,提出基于一致性算法的分布式控制策略来有效利用EV电池的有限存储容量。在此基础上,提出基于分布式光伏组件无功调节和有功调节的本地电压控制策略,并计算分布式光伏的无功与有功控制调节量。通过仿真分析,验证了文中所提的分布式一致性电压协同控制的有效性,可以有效缓解由反向潮流引起的电压升高,并补偿峰值负载导致的电压降落,消除由分布式电源大量接入带来的电压越限问题。     

Evaluation of cost and reliability of power systems with large numbers of distributed generators

The authors have proposed the Flexible, Reliable and Intelligent ENergy Delivery System (called “FRIENDS”), which is a new concept for future power distribution systems. Also, a “micro grid” which is a similar concept to FRIENDS has been developed. In a micro grid, an independent distribution system can be constituted by a number of distributed generators. In this paper, FRIENDS, Micro grid, and conventional distribution systems are compared quantitatively in supply reliability and system cost through time sequential Monte Carlo simulations. In addition, for cost evaluation, interruption costs are included to show risk incurred by unsupplied energy. Finally, the authors search for preferable form with install and operation of distributed generators and network composition according to social cost including interruption cost and system cost. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 167(2): 28–37, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20659     

分布式光伏电源极端可接入容量极限研究

为了防止大量分布式光伏电源接入配电网后可能引起电压偏差和电压波动越限,建立了负荷和分布式光伏电源引起的电压偏差和电压波动的计算模型。并在此基础上定义了分布式光伏电源极端可接入容量极限的概念,即负荷为0的极端情况下不致引起电压偏差和电压波动问题的分布式光伏电源接入容量极限。推导了6种典型分布情况下线路电压偏差和电压波动不越限时所能允许接入的极端容量极限。针对10 k V典型线路,给出了不同线型下城市配电网和农村配电网中分布式光伏电源安全接入的极端容量极限值。结果表明,分布式光伏电源极端可接入容量极限是保守的限值,只要满足该容量极限,无论分布式光伏电源和负荷的如何分布情况,都不至于对配电网产生不可接受的电压偏差或电压波动。