A Novel Power Injection Model of IPFC for Power Flow Analysis Inclusive of Practical Constraints

This paper describes a novel power injection model (PIM) of interline power flow controller (IPFC) for power flow analysis. In this model, the impedance of the series coupling transformer and the line charging susceptance are all included. In this situation, it is proved that the original structure and symmetry of the admittance matrix can still be kept, and thus, the Jacobian matrix can keep the block-diagonal properties, and sparsity technique can be applied. The IPFC state variables are adjusted simultaneously with the network state variables in order to achieve the specified control targets. Furthermore, the model can take into account the practical constraints of IPFC in Newton power flow. Numerical results based on the IEEE 57-bus and IEEE 300-bus systems are used to demonstrate the effectiveness and performance of the IPFC model     

A simple implementation of power mismatch STATCOM model into current injection Newton–Raphson power-flow method

This paper presents a simple implementation of Static Shunt Compensator (STATCOM) into Newton–Raphson current injection load flow method. The controlled STATCOM bus in the network is represented by voltage-controlled bus with zero active power generation at the required voltage magnitudes. The power mismatch equation of the connected STATCOM bus is included in Newton–Raphson current injection load flow algorithm, while the other PQ buses are represented by current mismatch equations. Moreover, the parameters of STATCOM can be calculated during iterative process and the final value will be updated after the convergence is achieved. This representation of generator buses reduces the number of required equations with respect to the classical and improved versions of the current injection methods. In addition of that the developed model reduces the complexities of the computer program codes and enhances the reusability by avoiding modifications in the Jacobian matrix. The performance of the developed STATCOM model has been tested using standard IEEE systems.     

A parallel distributed computing framework for Newton–Raphson load flow analysis of large interconnected power systems

This paper proposes a simple parallel and distributed computing framework for the conventional Newton–Raphson load flow (NRLF) solution of large interconnected power systems. The proposed approach is based on message-passing distributed-memory architecture with separate workstations, and involves the piecewise analysis of power systems utilizing the network tearing procedure. The NRLF solution method, applied to each torn system at the selected buses, employs the matrix inversion lemma consisting of the factorization, forward elimination and back substitution procedures. The computational requirements of the state-of-the art parallel algorithm to obtain the correction vector involved in the back substitution procedure is reduced with the proposed approach in which the back substitution is carried out in parallel taking into account the split buses, rather than the order in which the forward elimination is performed. The investigations are carried out on the IEEE 118 bus standard test system in a Redhat Linux based 100 Mbps Ethernet LAN environment. The investigations reveal that the proposed method is significantly faster than the conventional NRLF and also the NRLF based on the state-of-the-art parallel algorithm, and thus finds potential applications for the real-time load flow solution of both regulated and deregulated power systems distributed over large geographical areas.     

A Novel Location Method for Interline Power Flow Controllers Based on Entropy Theory

As one of the new generation flexible AC transmission systems (FACTS) devices, the interline power flow controller (IPFC) has the significant advantage of simultaneously regulating the power flow of multiple lines. Nevertheless, how to choose the appropriate location for the IPFC converters has not been discussed thoroughly. To solve this problem, this paper proposes a novel location method for IPFC using entropy theory. To clarify IPFC''s impact on system power flow, its operation mechanism and control strategies of different types of serial converters are discussed. Subsequently, to clarify the system power flow characteristic suitable for device location analysis, the entropy concept is introduced. In this process, the power flow distribution entropy index is used as an optimization index. Using this index as a foundation, the power flow transfer entropy index is also generated and proposed for the IPFC location determination study. Finally, electromechanical electromagnetic hybrid simulations based on ADPSS are implemented for validation. These are tested in a practical power grid with over 800 nodes. A modular multilevel converter (MMC)-based IPFC electromagnetic model is also established for precise verification. The results show that the proposed method can quickly and efficiently complete optimized IPFC location and support IPFC to determine an optimal adjustment in the N-1 fault cases.     

基于牛顿法的配电网络Zbus潮流计算方法

根据配电网的特点,在比较各类算法的基础上提出了一种新的基于牛顿法的配电网潮流算法。该算法从Zbus算法出发,对网络方程进行虚实部分解,形成的雅可比矩阵与节点导纳矩阵有极大的相似性,迭代中雅可比矩阵仅有少部分对角元素需要修改。算法通过修改雅可比矩阵元素来处理PV节点,还能够处理几种不同类型的负荷模型。理论分析和计算表明该算法性能优良,是配电网络潮流分析的有效方法。     

Voltage control devices models for distribution power flow analysis

This paper presents the development of mathematical models for thyristor controlled series compensator (TCSC), for voltage regulator devices and for remote bus voltage control that are suitable to be used with the three-phase current injection method (TCIM) for power flow calculation. TCIM is a Newton method where the equations are written in rectangular coordinates resulting in a 6n×6n Jacobian matrix. The representation of a control device requires an augmented system of equations to incorporate the additional relationship between each control action and the controlled variable, resulting in an augmented Jacobian matrix. Practical distribution systems are tested and the effectiveness of the proposed formulation is demonstrated     

线间潮流控制器应用评估策略研究

随着社会负荷不断增长、网架结构日益复杂,骨干网络潮流分布不均、电压支撑能力不足等问题已成为制约系统输送能力的重要因素。线间潮流控制器(Interline Power Flow Controller, IPFC)是一种潮流控制能力强大的新型FACTS装置,可应用于多条通道的潮流控制和暂态稳定控制,提升稀缺廊道资源的输电效率。考虑到目前缺乏对IPFC应用效果评估的理论研究和指导规划,本文提出了一种基于模糊层次分析的综合评判方法。首先,从静态、暂态、动态等方面定义了电网柔性评估指标,建立评估层次结构,并给出各指标的权重赋值方法。进一步地,在大系统中选取关键输电断面,通过多组算例获取各指标的标度,评估IPFC在典型应用场景下的控制潜力、安全指标及投资价值。最后结合模糊分析给出IPFC方案的综合分值和整体评价,量化装置对系统的作用,为IPFC的规划应用工程提供一定理论依据和技术支撑。     

Power flow control schemes for series-connected FACTS controllers

Unified power flow controller (UPFC) and interline power flow controller (IPFC) are FACTS devices that can control the power flow in transmission lines by injecting active and reactive voltage components in series with the lines, using power converter modules, based on an externally regulated dc-link voltage. One key issue, in this application, is to find a relationship between the injected voltage and the resulting power flow in the line. In this paper, this relationship is derived analytically, and used to design two power flow control schemes. The proposed control schemes are applicable to any series-connected FACTS controller with the capability of producing a controllable voltage. In this paper, the proposed power flow control schemes are applied to a voltage-sourced converter-based IPFC, and the resulting control performances are examined using PSCAD/EMTDC simulation package. The simulation results show the effectiveness of the proposed power flow control schemes.     

配电网电压稳定的分布式评估方法

提出了一种分布式评估配电网静态电压稳定性的方法.基于Distflow潮流模型建立包括平衡节点在内的配电网潮流方程组,对方程组求导后得到雅克比矩阵;利用Shur补对上述雅克比矩阵进行降阶,降阶雅克比矩阵的行列式作为配电网电压稳定性的评估指标;进一步研究发现,降阶雅克比矩阵属于对角占优阵,行列式的值约等于对角元的乘积,且其...     

A robust power flow model for active power flow control via thyristor‐controlled series compensator

In this paper, a new power flow model for active power flow control through a thyristor‐controlled series compensator (TCSC) in an AC network system is proposed. The proposed power flow model is based on the Newton–Raphson method. In this model, TCSC's admittance effect is included as a state variable into the Jacobian matrix to avoid the divergence problem. Unlike similar studies in the literature, TCSC's admittance is ignored in the bus admittance matrix, and the need for rebuilding the bus admittance matrix in each power flow iteration caused by the change of TCSC's admittance is prevented. So, faster convergence for power flow calculation is achieved. For this aim, new power equations are obtained. Also, in the proposed approach, we need not consider each terminal of TCSC as an individual bus in the power flow calculation. Thus, increasing the Jacobian and bus admittance matrixes sizes caused by the total bus number is prevented. The proposed approach is tested on an IEEE 57‐bus test system. The obtained results prove that this approach provides efficient, reliable, and fast convergence. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

基于直流潮流的网损微增率算法

介绍了一种基于直流潮流的网损微增率新算法直流雅可比矩阵法,该方法以直流潮流为基础,引入虚拟网损负荷变量并构造出带有松弛负荷变量的有功不平衡方程雅的可比矩阵,在解潮流过程中只需求解n阶矩阵的转置矩阵,即可获得各个节点的网损微增率。算例表明,直流雅可比矩阵法在计算速度和优化结果等方面都具有很大的优越性。     

含线间潮流控制器的电力系统联合潮流计算

线间潮流控制器(IPFC)能实现线路间的潮流转移和分配,可用于解决电力系统中潮流不均引起的一系列问题,具有较大的应用潜力和价值。为评估IPFC工程应用价值,需实现含IPFC的大系统潮流计算,但目前我国多用于电网规划设计的大型电力系统分析软件中没有开发IPFC模型。为解决上述问题,提出了一种基于Matlab与PSD-BPA的含IPFC电力系统的联合潮流计算方法。首先推导了IPFC功率注入模型的数学表达式,并设计了Matlab与BPA联合潮流计算的计算框架,由Matlab进行IPFC求解计算,BPA进行大电网潮流计算,通过数据交换接口完成两种仿真软件的交互与交替求解。进一步对IPFC功率注入模型进行改进,提出了一种基于PI控制器的变步长潮流迭代策略提高了计算方法的收敛性。以南通西北片电网为例,对提出方法进行了仿真验证,计算结果表明了提出方法的正确性和有效性。     

ATC enhancement in electricity markets with GUPFC and IPFC – A comparison

Available transfer capability (ATC) needs to be declared well in advance by the system operator to reserve transactions and avoid any congestion in the network. In this paper, an optimal power flow based approach has been utilized for bilateral/multi-transactions deregulated environment to obtain the ATC. The ATC has been obtained with generalized unified power flow controller (GUPFC) and interline power flow controller (IPFC) for intact and line contingency cases. The impact of ZIP load model has been evaluated on the ATC with both the devices. The main contribution of the paper is the comparison of the ATC obtained with. GUPFC and IPFC for intact and contingency cases with constant P,Q load model and ZIP load model. The results have been determined for intact and line contingency cases taking simultaneous as well as single transaction cases. The results obtained are also compared with DC/AC and PTDFs. The proposed method have been applied for IEEE 24 bus RTS.     

The power flow algorithm for balanced and unbalanced bipolar multiterminal ac–dc systems

Bipolar dc terminals are used for hvdc transmission in an ac–dc system. The sequential ac–dc power flow algorithm has been proposed for an ac–dc system consisting of balanced and unbalanced bipolar multiterminal in this paper. The algorithm has two superiority. Firstly, as dc system variables are not included in Jacobian matrix the convergence time of the algorithm and necessity of computer memory is little. Secondly, both this algorithm has been developed for (balanced and unbalanced) bipolar system (not only monopolar) and this algorithm also can be run with current controlled, voltage controlled and power controlled terminals without making any changes in proposed method.     

基于自动微分技术的内点法最优潮流算法

讨论了一种基于自动微分（AD）技术的内点法最优潮流（OPF）算法。与已有的基于AD技术的OPF算法相比,该算法使用高效的基于操作符重载的AD工具,充分利用直角坐标下雅可比矩阵和海森矩阵的大部分元素是常数的特点,加入了识别上述矩阵中不变元素的功能,避免了重复计算。对一组大规模算例的测试分析表明,该算法在保持代码可维护性、灵活性的同时,计算速度接近手动编程,表明AD技术在电力系统OPF中具有取代传统手动编程的潜力。     

Determination of IPFC operating constraints in power flow analysis

In recent years, the Flexible AC Transmission System (FACTS) controllers have been widely used to enhance the controllability, security and flexibility in power transmission networks. Interline power flow controller (IPFC) is a versatile member of FACTS devices that can be used to control the power flow in multiple lines in network. Modeling of IPFC with handling its operating constraints is an important issue to determine the practical capabilities of this device. This paper presents a simple modeling with strategies for handling all operating constrains of IPFC in Newton–Raphson (NR) load flow algorithm. The various operating constraints such as; the injected series voltages, injected line currents passing through the converters and exchanged powers among the series converters are investigated. The developed IPFC model with these constraints is validated using standard IEEE 30-bus and IEEE 118-bus test systems.     

电力系统潮流的并行松弛牛顿计算方法

将矩阵求逆运算的松弛方法应用于电力系统潮流计算,提出了一种新的电力系统潮流的并行松弛牛顿计算方法。该并行算法既适合于向量机,亦适合于非向量、多处理器并行结构。利用并行虚拟机技术在计算机网络上对所提出的并行算法进行了实际装配。研究结果表明,所提出的并行算法具有较好的收敛性和并行程度,可以获得较高的加速比和并行效率。     

Power flow control approach to power systems with embedded FACTS devices

This paper focuses on developing an approach to steady-state power flow control of flexible AC transmission systems (FACTS) device-equipped power systems. Based on a power-injection model of FACTS devices and an optimal power flow model, a novel versatile power flow control approach is formulated, which is capable of implementing power flow control incorporating any FACTS device flexibly. Different from existing FACTS device control approaches, the active and (or) reactive power injections are taken as independent control variables. Therefore, using this method, Jacobian matrix need not be changed, although various FACTS devices possess different physical models and different control parameters. Furthermore, it enables the integration of FACTS devices into the existing power system analysis and control programs efficiently. Physical limits of the FACTS devices are also considered in the model. Numerical results on a reduced practical system and a 1500-bus practical system with various FACTS devices are presented to illustrate the vigorousness of the proposed approach.     

中性点不接地配网潮流算法研究

针对中性点不接地系统无零序通路的特点,推导出一种新的适用于负荷不对称配网的序分量潮流算法。该方法将不对称的三相负荷转化为正序功率和负序功率,同时引入耦合功率,将正序、负序功率解耦,仅求解正序潮流,而节点负序分量则通过耦合功率求出。该算法将现有配网三相潮流算法中的3n阶矩阵降为n阶,大大降低了计算量。将该算法和传统方法分别应用于某一基于统计数据的19节点实际系统,对两者的计算结果进行比较,并分析差异产生的原因。以一个基于实时数据的28节点仿真系统算例验证了该算法的正确性。     

Numerical observability analysis based on network graph theory

This paper presents a numerical method for topological observability analysis of a measured power system. By floating-point operations on the echelon form of a rectangular test matrix, which is based on network graph properties, observability and maximal observable islands are determined. A minimal set of pseudo measurements, which make an unobservable network barely observable, is selected in a noniterative manner. The existing numerical methods are based on the number of zero pivots that may appear during the factorization of the measurement Jacobian or the gain matrix. Due to round-off errors, the zero pivots may be misclassified. The problem becomes more severe when the number of injection measurements is large, resulting in a great disparity of values in Jacobian or gain matrix. In the proposed method, the test matrix consists of +/-1 values, it is numerically better conditioned and zero pivots are identified more accurately. By topological processing of the flow measured branches and by removing the redundant injection measured nodes that are incident only to flow measured branches or branches which form loops with flow measured branches, a reduced test matrix is created with fewer nonzero elements than the Jacobian or the gain matrix, resulting in less computational effort. The method details are illustrated by various test systems.