Deyu Cai

Wide-Area Monitoring, Protection, and Control of Future Electric Power Networks

Wide-area monitoring, protection, and control (WAMPAC) involves the use of system-wide information and the communication of selected local information to a remote location to counteract the propagation of large disturbances. Synchronized measurement technology (SMT) is an important element and enabler of WAMPAC. It is expected that WAMPAC systems will in the future reduce the number of catastrophic blackouts and generally improve the reliability and security of energy production, transmission, and distribution, particularly in power networks with a high level of operational uncertainties. In this paper, the technological and application issues are addressed. Several key monitoring, protection, and control applications are described and discussed. A strategy for developing a WAMPAC system in the United Kingdom is given as well.

Measurements get together

This article deals with the synchronized measurement technology that has the potential of becoming the backbone for real-time monitoring system. The secure and reliable operation of modern power systems is an increasingly challenging task due to the ever-increasing demand for electricity, the growing number of interconnections, penetration of variable renewable energy sources, and deregulated energy market conditions. Power companies in different parts of the world are therefore feeling the need for a real-time wide area monitoring, protection, and control (WAMPAC) system. Synchronized measurement technology (SMT) has the potential of becoming the backbone of this system. The major advantages of using SMT are that 1) the measurements from widely dispersed locations can be synchronized with respect to a Global Positioning System (GPS) clock, 2) voltage phase angles can be measured directly, which was so far technically infeasible, and 3) the accuracy and speed of energy management system (EMS) applications increases manifold.

Wide Area Inter-Area Oscillation Monitoring Using Fast Nonlinear Estimation Algorithm

This paper presents the results of the development of Smart Grid transmission network applications in the Great Britain (GB) power system. A new Wide Area Monitoring System (WAMS) application for monitoring inter-area oscillations is developed. The core of this novel application is a fast nonlinear algorithm for the real-time estimation of the dominant inter-area oscillation mode, which processes GPS synchronized information obtained from Phasor Measurement Units (PMUs) installed in the power system. It is based on the Newton-Type Algorithm (NTA), an efficient parameter estimator. The paper focuses on the practical application of the new WAMS application: two data sets were tested, one based on computer simulations and the other based on real-life data records. The computer simulated oscillatory signals were obtained through dynamic simulations of the full GB power system model consisting of over 200 generators. The real-life data records used information collected by the FlexNet Wide Area Monitoring System (FlexNET-WAMS) installed in the GB network. Based on these data records, the features of inter-area oscillations in the GB network are drawn.

Frequency and Power Components Estimation from Instantaneous Power Signal

In this paper, the problem of the simultaneous estimation of frequency and power components is investigated. It is solved through a new recursive estimator capable of estimating the unknown model parameters during severe dynamic changes in the system. By this, a simple nonlinear parameter model for the instantaneous power, taking into account the fundamental components of voltage and current, is used as a starting point for the power components and frequency estimation. In the model, the system frequency is considered as an unknown model parameter, and it is simultaneously estimated with other unknown parameters. This resulted in an efficient numerical algorithm for the measurement of power components, which is not sensitive to variations of the system frequency. This is an important achievement, which improves the accuracy of the method during network transients. The new estimator has been improved by the strategy for tuning its forgetting factor according to the system dynamics, and it is tested through computer simulations and by using data records obtained under laboratory conditions. The algorithm was developed for a single-phase system, and the approach might be easily extended to multiphase systems.

Enhanced state estimation with real-time updated network parameters using SMT

This paper presents a brief explanation how Synchronized Measurement Technology (SMT) and WAMPAC architecture can support State Estimation and it discusses the existing correlation between each other. Additionally, it is presented a practical implementation of Phasor Measurement Units for updating network parameter data bases to improve the performance of state estimators. The methodology presented can be implemented only when full observability of the network parameters is available. The performance of the enhanced state estimator is assessed for different types of measurements and parameter errors. It is shown how the proposed solution delivers a more reliable estimation, especially when parameter errors are difficult to detect.

Development of a flexible laboratory testing platform for assessing steady-state and transient performance of WAMS

This paper analyzes the development of an experimental setup for the steady state and transient analysis of Wide Area Measurement Systems (WAMS). The flexibility of the generated input signals for which the PMU performance is assessed represents a novel contribution of the designed setup. Transient disturbances modeled by mathematical functions or extracted from simulated networks within DigSILENT PowerFactory software are converted to COMTRADE files and uploaded into two signal generators in order to build relevant analogue waveforms for analyzing Phasor Measurement Units (PMUs) steady state and transient behavior. A novel characteristic of the design consists of the automated generating, acquisition and analysis procedure capable of processing the large quantity of results on which the steady state and transient performance assessment of WAMS is based. The assessment has revealed some equipment introduced phase shift errors, but their cause has been identified and overcome through the comparison of qualitative parameters of the input and output signals.

Protection scheme for blackout prevention in distribution networks with mixed energy resources

The main goal of this paper is to present a new methodology for the estimation of magnitudes of disturbances (EMD). This methodology can be utilized in the adaptive Low Frequency Demand Control schemes in the next generation of distribution and transmission networks. In the focus of this paper will be distribution networks, consisting of conventional consumers and mixed renewable energy sources. The paper is divided into two main parts: in the first part, the methodology of the EMD will be presented; in the second part, the algorithm of the EMD will be tested. The testing will be carried out using three different test networks having the same topology, but different profile of energy sources.