WAMS applications in Chinese power systems

Since the first GPS-based phasor measurement (PMU) unit was invented, synchrophasor technology has developed for more than a decade. During this period many concepts were proposed, for instance, the wide-area measuring/monitoring system (WAMS). It brings great potential for upgrading the supervision, operation, protection and control of modern power systems. In China, this emerging technology also attracts great concerns because of the rapidly expanding scale of many new challenges to Chinese power industry. In this article, we summarize the most recent development of PMU/WAMS in China, with emphasis on the basic architectures and functions of the developed system and the communication infrastructures. The future trend is also discussed.     

Phasing in the Technology

P september/october 2008 ieee power & energy magazine 25 Phasor measurements were introduced as a specialized power system measurement in 1986. Following a paper published in 1983 describing the technique, Virginia Tech produced prototype phasor measurement units (PMU s) that were supplied to American Electric Power (AE P) and the Bonneville Power Administration (BPA). These units were tested and used by these utilities for several years before the first commercial unit, the Macrodyne 1690, was introduced in 1991. Using the original PMU s, AE P and BPA built phasor measurement systems that only provided recorded data for analysis with basic plotting tools. BPA redesigned the measurement system in 1997 into a true real-time, widearea measurement system (Figure 1) using commercial PMU s and a custom phasor data concentrator (PDC ). Since then, many phasor data systems have been developed and deployed throughout the world. Many more PMU models have become available with a range of options. Several variations of PDC units have been produced, and many applications are available for analysis of recorded phasor data as well as real-time display and alarming. This article examines the current phasor measurement systems in North America.     

PMU-WAMS research and application in Brazil

Wide area measurement system (WAMS), which is based on synchronization data from phasor measurement units (PMU) and EMS SCADA, is implemented to establish a system model that can handle certain functions such as realtime power system monitoring, oscillation mode analysis, accident analysis and decision-making assistance for emergency control. The Brazilian Interconnected Power System (BIPS) is a large system covering an extensive geographical region, which faces certain risks and challenges. It has several main transmission corridors associated with large power plants and interconnection between the northern and southeastern regions. Mismatch between the energy base and load pool also exists in Brazil as energy resources are not well-distributed; therefore, the use of large-capacity, long-distance transmission technique to transmit remote power is unescapable. On the other hand, there are many types of voltage levels and multiple entangled electromagnetic loops owing to historical reasons. Then, for insufficient power reservation and defective grid body in load pools, once the external power is cut, it’s easy to raise a blackout. The infrastructure is old and the power system operates close to the upper limit. All these represent risks and challenges to BIPS. Through WAMS technology research method in this project, the electrical power system function of monitoring, analysis, and control improved from the static state to the dynamic state. WAMS enhances data integration and real-time analysis capabilities, and can provide dispatchers with high quality real-time dynamic information and decision-making support information, enhance monitoring of auxiliary services in the electricity market, enable operators to improve the accuracy of power network analysis, thereby increasing power grid monitoring and operation, and improve the transmission capacity and reliability of the power grid operation [1].     

基于PMU的广域测量技术及其应用

分析了相量测量单元（PMU）的测量原理以及广域测量系统（WAMS）的构成,总结和预测了基于PMU的广域测量系统的应用,并比较了PMU／WAMS与传统的SCADA／EMS系统的不同点。预测了今后智能电网发展过程中广域测量技术的发展应用情况。     

Optimal placement of PMUs for the smart grid implementation in Indian power grid—A case study

Efficient utilization of energy resources is essential for a developing country like India. The concept of smart grid (SG) can provide a highly reliable power system with optimized utilization of available resources. The present Indian power grid requires revolutionary changes to meet the growing demands and to make the grid smarter and reliable. One of the important requirements for SG is the instantaneous monitoring of the voltage, current and power flows at all buses in the grid. The traditional monitoring system cannot satisfy this requirement since they are based on nonlinear power flow equations. Synchro-phasor-measurement devices like phasor measurement units (PMUs) can measure the phasor values of voltages at installed buses. Consequently, the currents passing through all branches connected to that bus can be computed. Since the voltage phasor values at the neighboring buses of a bus containing the PMU can be estimated using Ohm’s law, it is redundant to install PMUs at all the buses in a power grid for its complete observability. This paper proposes the optimal geographical locations for the PMUs in southern region Indian power grid for the implementation of SG, using Integer Linear Programming. The proposed optimal geographical locations for PMU placement can be a stepping stone for the implementation of SG in India.     

Optimal redundant placement of PMUs in Indian power grid — northern,eastern and north-eastern regions

Effective utilization of renewable energy sources and efficient management of electric energy are essential for any developing countries like India. This can be envisioned through the implementation of concepts of smart grid (SG). One of the key requisites for SG implementation is that the grid should be completely observable. Renovation of conventional Indian power grid to a SG necessitates incorporation of the phasor measurement units (PMUs) in the present power grid measurement and monitoring system. Since the cost of PMU is high and any bus containing a PMU makes the neighboring connected buses observable, optimal placement of PMUs is very important for complete observability of the grid. This paper proposes optimal redundant geographical locations in the northern, eastern and north-eastern regions of Indian power grid for PMU placement. The PMUs installed in these geographical locations will make the grid completely observable and maintain the observability under the conditions of failure of some PMUs or branch outages. Integer linear programming has been used for finding the optimal PMU locations. The results proposed in this paper can be a stepping stone for revamping the Indian power grid to a SG ensuring complete observability during different contingency conditions.     

Pragmatic multi-stage simulated annealing for optimal placement of synchrophasor measurement units in smart power grids

Conventional power grids across the globe are reforming to smart power grids with cutting edge technologies in real time monitoring and control methods. Advanced real time monitoring is facilitated by incorporating synchrophasor measurement units such as phasor measurement units (PMUs) to the power grid monitoring system. Several physical and economic constraints limit the deployment of PMUs in smart power grids. This paper proposes a pragmatic multi-stage simulated annealing (PMSSA) methodology for finding the optimal locations in the smart power grid for installing PMUs in conjunction with existing conventional measurement units (CMUs) to achieve a complete observability of the grid. The proposed PMSSA is much faster than the conventional simulated annealing (SA) approach as it utilizes controlled uphill and downhill movements during various stages of optimization. Moreover, the method of integrating practical phasor measurement unit (PMU) placement conditions like PMU channel limits and redundant placement can be easily handled. The efficacy of the proposed methodology has been validated through simulation studies in IEEE standard bus systems and practical regional Indian power grids.     

含有限PMU的主动配电网故障定位

对于含分布式电源(DG)的主动配电网,基于同步相量测量单元(PMU)的监测信息进行故障分析与处理,从而达到定位目的.首先采用拓扑优化法对PMU进行布点优化配置,同时将系统划分为不同区域.利用PMU监测所得实时潮流和电气量信息,基于功率增量方向原理可初步判断发生故障的区域;其次计算候选故障区域内各条区段发生不同类型故障时...     

Subsynchronous oscillation monitoring and alarm method based on phasor measurements

Owing to the large-scale grid connection of new energy sources, several installed power electronic devices introduce sub-/supersynchronous inter-harmonics into power signals, resulting in the frequent occurrence of subsynchronous oscillations (SSOs). The SSOs may cause significant harm to generator sets and power systems; thus, online monitoring and accurate alarms for power systems are crucial for their safe and stable operation. Phasor measurement units (PMUs) can realize the dynamic real-time monitoring of power systems. Based on PMU phasor measurements, this study proposes a method for SSO online monitoring and alarm implementation for the main station of a PMU. First, fast Fourier transform frequency spectrum analysis is performed on PMU current phasor amplitude data to obtain subsynchronous frequency components. Second, the support vector machine learning algorithm is trained to obtain the amplitude threshold and subsequently filter out safe components and retain harmful ones. Finally, the adaptive duration threshold is determined according to frequency susceptibility, amplitude attenuation, and energy accumulation to decide whether to transmit an alarm signal. Experiments based on field data verify the effectiveness of the proposed method.     

基于图论的电力系统PMU布点优化算法

基于最小支配集理论和电力系统线性量测模型．提出了可观测节点集合、WAMS可观测矩阵两个概念以及一种新的节点可观测性计算规则。以保证系统的完全可观测性和以系统图的最小支配集为搜索范围构成约束条件,以电力系统状态完全可观测和相量测量装置（PMU）配置数目最小为目标,形成了PMU配置优化问题。并应用禁忌搜索（TS）方法求解该问题,保证了全局寻优。最后采用IEEE14、30、57、118节点系统和新英格兰39节点系统对该方法进行了验证,仿真结果表明该方法的有效性和可行性。     

基于PMU量测的线路参数辨识算法

利用PMU量测数据具有严格时间同步、均匀发送的特点,基于PI型等值电路模型,提出一种新的线路参数辨识方法。该方法以线路两端测量的电压和电流相量为基础,利用最小二乘算法实现线路参数的最小偏差辨识,理论分析和实际算例表明了该方法的可行性。对影响辨识精度的主要误差源进行了分析,并给出了一种实用的坏数据剔除方法,可进一步提高数据辨识的精度;亦对如何利用线路量测的残差分析结果指导状态估计中的权重系数设置进行了详细讨论。与传统方法相比,基于PMU量测的参数辨识方法具有灵活、简便、可重复和连续执行的优点,具有较高的实用价值。     

A PMU data recovering method based on preferred selection strategy

Nowadays, the technology of renewable sources grid-connection and DC transmission has a rapid development. And phasor measurement units (PMUs) become more notable in power grids, due to the necessary of real time monitoring and close-loop control applications. However, the PMUs data quality issue affects applications based on PMUs a lot. This paper proposes a simple yet effective method for recovering PMU data. To simply the issue, two different scenarios of PMUs data loss are first defined. Then a key combination of preferred selection strategies is introduced. And the missing data is recovered by the function of spline interpolation. This method has been tested by artificial data and field data obtained from on-site PMUs. The results demonstrate that the proposed method recovers the missing PMU data quickly and accurately. And it is much better than other methods when missing data are massive and continuous. This paper also presents the interesting direction for future work.     

相量测量装置在750 kV变电站的应用

对在西北电网750 kV变电站装设的PMU装置应用和运行情况进行了阐述。西北电网PMU相量测量装置具备实时监测、动态数据实时记录和实时通信三大功能,且三者互不干扰、互不影响。列举了该装置在满负荷试验和电网故障时的应用实例,对运行中发现的端子接线问题、程序参数设计问题进行了具体分析。通过对广域相量测量的总结说明在750 kV电网范围内推广开展的重要性。     

Implementation and performance evaluation of advance metering infrastructure for Borneo-Wide Power Grid

In this paper, a supervisory computer network for Borneo-Wide Power Grid system have been proposed and implemented, which includes a renewable power generation and advanced metering infrastructure. An Internet-based communication network running on multiprotocol label switching (MPLS) has been implemented for a smart power grid, with the addition of the renewable energy monitoring system. The centralized supervisory control and data acquisition systems (SCADA) are replaced by a wide area monitoring system(WAMS) comprising of a phasor measurement unit (PMU). The implemented communication network used advanced metering infrastructure that operates on worldwide interoperability for microwave access (WiMAX), wireless fidelity (Wi-Fi) and low power Wi-Fi, which are proposed for the distribution systems of Sarawak Energy. The proposed wide area network (WAN) is simulated using OPNET Modeler and the results are compared with the existing WAN used by Sarawak Energy.     

考虑数据时延的电力系统两阶段动态状态估计方法

由于电力系统中SCADA数据和PMU数据采样频率不同,使得这两种数据存在时延.首先提出基于变点重复检测的PMU最佳缓冲长度计算方法,将SCADA数据和PMU数据统一到同一时间尺度下,然后将无迹变换与指数权函数抗差估计算法相结合,针对历史多数据断面进一步提出了两阶段无迹卡尔曼滤波鲁棒动态状态估计方法.该方法在每一断面内,...     

Boosting immunity to blackouts

There have been several key developments that make it conceivable that it would soon be possible to reduce the frequency and intensity of interconnected power system failures. System protection is one of the technologies undergoing radical changes that holds a strong promise that cascading system outages can be mitigated or even eliminated. The increasing use of digital relays that will allow the implementation of exciting new concepts has made this a strong possibility. In this article, we report on future concepts in power system protection, communication, wide area measurement systems (WAMS), system control, and electricity market considerations, Adding a summary of our own research in associated studies and our assessment of future investigations, our aim is to provide a blueprint for a secure power system infrastructure.     

智能配电网广域同步相量测量体系设计方案研究

[目的]随着配电网大规模分布式电源和柔性负荷的接入,传统终端测量的准确性和速度难以满足实际需要,而采用新一代配电网微型同步相量测量装置(Distribution Micro Synchronous Phasor Measurement Unit,D-PMU)是解决上述问题的一个重要途径.[方法]首先,分析了D-PMU的...     

基于混合量测状态估计的保护隐性故障检测系统

继电保护装置的隐性故障可能导致装置失效,不能有效发现电力系统故障,严重时甚至引起电网连锁故障,目前尚缺乏有效手段对其进行检测。为此提出利用SCADA及WAMS采集电网数据进行混合量测状态估计得到系统状态作为参考值,将该参考值与保护信息系统接受的继电保护装置测量数据进行比较,若差值超过预设门槛值,则可判定保护装置存在隐性故障,并在此基础上建立隐性故障检测系统。算例测试结果表明,该系统能在稳态时长期在线检测隐性故障,且在节点量测信息出现偏差时仍能有效检测隐性故障。     

First steps to wide area control

The implementation of synchronized phasor measurements for system monitoring and control is receiving unparalleled attention in the power industry.In this article, we describe recent work to incorporate phasor measurements from several locations in the transmission system into a control center state estimator, the prime application for assisting the operators to understand the operating state of the power system and for making informed decisions with respect to scheduling transmission capacity and responding to contingencies.     

Field experiment using transient energy method to locate a single-phase to ground fault

Distribution networks in China and several other countries are predominantly neutral inefficiently grounding systems (NIGSs), and more than 80% of the faults in distribution networks are single-phase-to-ground (SPG) faults. Because of the weak fault current and imperfect monitoring equipment configurations, methods used to determine the faulty line sections with SPG faults in NIGSs are ineffective. The development and application of distribution-level phasor measurement units (PMUs) provide further comprehensive fault information for fault diagnosis in a distribution network. When an SPG fault occurs, the transient energy of the faulted line section tends to be higher than the sum of the transient energies of other line sections. In this regard, transient energy-based fault location algorithms appear to be a promising resolution. In this study, a field test plan was designed and implemented for a 10 kV distribution network. The test results demonstrate the effectiveness of the transient energy-based SPG location method in practical distribution networks.