Phasor Measurement Unit Information Research Articles

Enhancing Performance of Wide-Area Back-Up Protection Scheme Using PMU Assisted Dynamic State Estimator

Wide-area measurements consisting of phasor measurement information, are lately used for monitoring and protection purposes. However, due to certain constraints related to usage of phasor measurement units (PMU) at all the buses, optimal placement of PMUs are needed for wide area applications. Further, limitations of supervisory control and data acquisition measurements and erroneous PMU measurements due to noise and communication link failure at some instant leads to the requirement of dynamic state estimation (DSE) using PMU information. The proposed scheme deals with wide area back-up protection scheme utilizing cubature Kalman filtering-based DSE in conjunction with fewer PMU measurements for obtaining full observability. A voltage-based index is derived using the DSE information to identify the faulty line. The scheme is tested for several faulted as well as stressed conditions such as line outage, generator outage, load encroachment and voltage stressed conditions including measurement error and missing data at some of the PMU buses. Extensive test on New England 39-bus system indicate that the proposed wide-area back-up protection scheme can reliably take appropriate action for back-up zone.

PMU Assisted Integrated Impedance Angle-Based Microgrid Protection Scheme

Development of protection scheme for microgrid is a challenging issue due to the inclusion of distributed generations (DGs). The research work for developing the primary protection scheme for microgrid is progressing continuously. This paper proposes an integrated impedance angle (IIA) based protection scheme using wide-area positive sequence components of voltages and currents. The proposed scheme uses data retrieved from the phasor measurement units (PMUs) of IEEE C37.118.1 complied standards. Furthermore, the IIA for the line is computed considering both ends PMU information, which is the key indicator for identifying the faults in the microgrid. The proposed protection scheme is extensively tested considering the different operating conditions of microgrid, variation in DG penetration and variation in fault parameters such as fault resistance, fault types, and fault location. Furthermore, cross validation on no-fault situations including section cutoff, disconnection of high penetration DG, grid-islanding resynchronization, motor starting, capacitor switching, and load encroachment are carried out. The proposed scheme is also tested for the insensitivity towards the external faults. The test results on both 15-bus and 34-bus systems clearly indicate that the proposed IIA-based wide-area scheme can be a potential protection measure for microgrid under varied operating circumstances.

Distributed State Estimation for Distribution Network with Phasor Measurement Units Information

As the distribution network structure becomes increasingly complex, this paper proposes a distributed state estimation for distribution network with phasor measurement units (PMUs) information to improve the performance of state estimation. This proposed method takes the PMU installation locations as alternative points of the partition, and takes the scale of sub-zone, the number of real-time measurement, and the DG configuration position as the partition criteria, and then conducts distributed state estimation. During the state estimation, the root bus voltage and branch current are used as state variables to reserve the advantage of measurement conversion technology, and the traditional measurement data and PMU measurement data are converted into corresponding currents, which simplifies the Jacobian matrix, thereby reducing iterations and improving the calculation speed of state estimation. Finally, the IEEE 69-bus radial distribution network is used to verify the effectiveness of the proposed method.

Homogeneity-PMU-Based Method for Detection and Classification of Power Quality Disturbances

Over the past few years, power quality (PQ) monitoring has become of paramount importance for utilities and users since poor PQ generates negative consequences. In monitoring, fast detection and accurate classification of PQ disturbances (PQDs) are desirable features. In this work, a new method to detect and classify PQDs is proposed. The proposal takes advantage of the low computational resources of both a phasor measurement unit (PMU)-based signal processing scheme and the homogeneity approach. To classify the PQDs, if–then–else rules are used. To validate and test the proposal, synthetic and real signals of sags, swells, interruptions, notching, spikes, harmonics, and oscillatory transients are considered. For the generation of real signals, a PQD generator based on a power inverter is used. In the proposed method, the PMU information is directly used to classify sags, swells, and interruptions, whereas the homogeneity index is used to distinguish among the remaining PQDs. Results show that the proposal is an effective and suitable tool for PQ monitoring.

A New Adaptive Dependability-Security Approach to Enhance Wide Area Back-Up Protection of Transmission System

This paper presents a new methodology to adaptively shift the dependability and security bias of the transmission system protection logic depending on the system state. Contingencies such as generator outage, line outage, and line fault can induce stressed system condition. Under stressed conditions, protection logic should be more biased toward security. Phasor measurement unit information is used at the system protection centre to estimate the system state. A data-mining model known as random forest is utilized to accomplish the task of state assessment. Two different protection logics are used to make the final relaying decision. The first protection logic is the existing distance relay and the second protection logic is based on wide area information. Both the protection logics are connected though logic gates to make the final relaying decision. The performance of the proposed scheme is validated on the IEEE-39 bus New England system and 246-bus Indian Northern Regional Power Grid system. The test results indicate that the proposed algorithm can help in shifting the dependability-security bias of the protection logic adaptively, which will help in mitigating cascaded outages in the power transmission system.

On-line dynamic voltage stability status prediction based on DLM and LIB boundaries using phasor measurement unit information

On-line dynamic voltage stability status prediction based on DLM and LIB boundaries using phasor measurement unit information

Power System Real-Time Monitoring by Using PMU-Based Robust State Estimation Method

Accurate real-time states provided by the state estimator are critical for power system reliable operation and control. This paper proposes a novel phasor measurement unit (PMU)-based robust state estimation method (PRSEM) to real-time monitor a power system under different operation conditions. To be specific, an adaptive weight assignment function to dynamically adjust the measurement weight based on the distance of big unwanted disturbances from the PMU measurements is proposed to increase algorithm robustness. Furthermore, a statistical test-based interpolation matrix ${H}$ updating judgment strategy is proposed. The processed and resynced PMU information are used as priori information and incorporated to the modified weighted least square estimation to address the measurements imperfect synchronization between supervisory control and data acquisition and PMU measurements. Finally, the innovation analysis-based bad data (BD) detection method, which can handle the smearing effect and critical measurement errors, is presented. We evaluate PRSEM by using IEEE benchmark test systems and a realistic utility system. The numerical results indicate that, in short computation time, PRSEM can effectively track the system real-time states with good robustness and can address several kinds of BD.

Synchrophasor-Assisted Prediction of Stability/Instability of a Power System

Abstract This paper presents a technique for real-time prediction of stability/instability of a power system based on synchrophasor measurements obtained from phasor measurement units (PMUs) at generator buses. For stability assessment the technique makes use of system severity indices developed using bus voltage magnitude obtained from PMUs and generator electrical power. Generator power is computed using system information and PMU information like voltage and current phasors obtained from PMU. System stability/instability is predicted when the indices exceeds a threshold value. A case study is carried out on New England 10-generator, 39-bus system to validate the performance of the technique.