Damping forced oscillations in power system via interline power flow controller with additional repetitive control

With the continuous expansion of power systems and the application of power electronic equipment, forced oscillation has become one of the key problems in terms of system safety and stability. In this paper, an interline power flow controller (IPFC) is used as a power suppression carrier and its mechanism is analyzed using the linearized state-space method to improve the system damping ratio. It is shown that although the IPFC can suppress forced oscillation with well-designed parameters, its capability of improving the system damping ratio is limited. Thus, combined with the repetitive control method, an additional repetitive controller (ARC) is proposed to further dampen the forced power oscillation. The ARC control scheme is characterized by outstanding tracking performance to a system steady reference value, and the main IPFC controller with the ARC can provide higher damping, and further reduce the amplitude of oscillations to zero compared with a supplementary damping controller (SDC). Simulation results show that the IPFC with an ARC can not only greatly reduce the oscillation amplitude, but also actively output the compensation power according to the reference value of the ARC tracking system.     

基于同步真空断路器的智能无功补偿装置

为了提高10kV配电网的供电质量，提出一种基于同步真空断路器的智能无功补偿系统。该系统以同步真空断路器(SVCB)与智能功率因数控制器(IPFC)为核心，通过同步(选相控制)技术减少投切电容器组时所引起的涌流与过电压；IPFC综合电网功率因数、无功需求以及谐波谐振保护作为动作判据。这样不但可以达到最佳无功补偿效果，并能有效地解决暂态冲击、轻载反复投切与谐波谐振等问题，弥补了当前无功补偿装置所存在的不足。仿真分析与试验研究验证了该方案的优越性与可行性。     

A generalized approach for determination of optimal location and performance analysis of FACTs devices

This paper presents a generalized approach for determination of optimal locations for placement of Flexible AC Transmission Systems (FACTs) devices in the power system with an objective of reducing real power loss and to reduce overloading of the lines. An objective function involving above objectives is formulated and a detailed mathematical model for each objective is presented in terms of system parameters. Three FACT devices, namely, Unified Power Flow Controller (UPFC), Interline Power Flow Controller (IPFC), and Optimal Unified Power Flow Controller (OUPFC) which are capable of controlling both active and reactive power are considered in simulation and analysis of the networks. The parameters to be optimized have been identified and incorporated in the objective function for each device. Sensitivity analysis is used to locate optimal buses to place the FACTs devices in the network. Effectiveness of the approach is demonstrated on a 5 Bus and an IEEE 14 Bus systems for each FACT device. Simulation results obtained for each device using proposed approach are compared with those obtained in the literature.     

基于YNvd平衡变压器和模拟负载的同相供电试验系统

为了更深入开展同相供电系统的研究,提出了一种由新型YNvd平衡牵引变压器、模拟负载以及综合潮流控制器(IPFC)构成的同相供电试验系统方案。分别介绍了YNvd平衡变压器、IPFC和模拟负载的结构和工作原理,通过对IPFC与模拟负载制定相应的控制策略,以实现对同相供电系统的仿真模拟。研究结果表明,该试验系统能够模拟牵引负荷特性,实现能量循环利用,模拟同相供电系统,消除了系统负序电流,实现了谐波和无功的动态补偿,验证了同相供电系统的可行性。     

Use of IPFC Detailed Dynamic Model for Analysis of Power Flow Control and Small-Signal Stability Enhancement

This paper presents a study of the power flow control capability of the interline power flow controller (IPFC) and its effect on small-signal stability enhancement. A detailed dynamic model of IPFC suitable for power system electromechanical stability analysis is developed in this paper. The power flow control capability of the proportional-integral (PI) controllers and their effect on power oscillation damping are evaluated first, and modal analysis of the power system is carried out to demonstrate their effectiveness in small-signal stability enhancement. Then the eigenvalue sensitivity based parameter optimization technique is adopted to optimize the control parameters of PI controllers in order to stabilize the oscillatory modes having insufficient damping ratios. Numerical simulation results demonstrate that the IPFC with the proposed control is an effective tool for power flow control and small-signal stability enhancement, and the optimized PI controllers also have a positive effect on improving the performance of IPFC in power flow control. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

线间潮流控制器在改善电能质量中的应用

介绍了线间潮流控制器(IPFC)的基本工作原理,建立了数学模型.提出了应用IPFC装置的有功无功线间综合控制提高电力系统暂态稳定性的两层控制模型并进行了试验仿真.仿真结果表明:IPFC装置比传统的FACTS装置更能有效地提高系统的暂态稳定性和电能质量.     

Energy function for an interline power-flow controller

An IPFC may be applied for steady-state power-flow and voltage control as well as for mastering dynamic phenomena like transient-stability margin enhancement, oscillation damping, etc. For these tasks the Lyapunov energy-function approach is frequently used as a convenient way to control or analyze the electric-power system (EPS). The basis for the implementation of such an approach is to know the energy function of the EPS. Currently, this is not possible for the EPSs that include IPFCs, because the already-known energy functions that proved to be suitable for an EPS do not include such a device. Therefore, in this paper, energy functions that consider the IPFC's action in the form of a supplement to the already-known structure-preserving energy functions were constructed. They are based on a structure-preserving frame and can be applied for an arbitrary number of IPFCs, which may consist of an arbitrary number of series branches. The developed energy functions were applied for a transient-stability assessment using the Lyapunov direct method, and they proved to be adequate.     

同相牵引供电系统的补偿原理及再生制动特性

由平衡变压器和综合潮流控制器(integrated power flow controller,IPFC)组合构成的同相牵引供电系统可解决负序电流、谐波电流、无功电流的补偿及电分相方面存在的问题,分析了该供电系统的补偿原理,比较了牵引和再生制动状态同相牵引供电系统对电力系统供电质量的影响,指出制动状态下IPFC可在不改变控制策略的情况下将能量平衡地回馈到三相电网,节约电能。仿真结果验证了同相牵引供电方案的正确性。     

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.     

A current-based model of an IPFC for Newton–Raphson power flow

In this paper a new approach to modeling an interline power flow controller (IPFC) for power flow calculations by applying the Newton–Raphson method is presented as a continuation of the ideas already applied to static synchronous series compensator (SSSC). The presented approach differs from the methods proposed by other authors in terms of the interpretation of the device's branches. They are considered on the basis of their currents, and so it can, therefore, be denoted as a current-based model of an IPFC. First, the basic features of the IPFC are presented; as this is the basis for the current-based model that is incorporated into the Newton–Raphson load-flow model. Next, the basic equations are derived from the generic IPFC model. Further handling of the constraints is then discussed. The derived model was tested on the IEEE 57, IEEE 118 and IEEE 300 bus systems. The effectiveness of the proposed model's iteration procedure is compared with other models. The comparison is based on data available in the references. We have shown that the proposed model exhibits a faster convergence than other models, and in addition, the number of iterations needed to achieve the prescribed accuracy is almost constant, regardless of the location, a consideration of the constraints or the selection of the controlled variable.