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Prior research has shown that autocorrelation and variance in voltage measurements tend to increase as power systems approach instability. This paper seeks to identify the conditions under which these statistical indicators provide reliable early warning of instability in power systems. First, the paper derives and validates a semi analytical method for quickly calculating the expected variance and...
This paper presents the design and implementation of an advanced Battery Management System (BMS). The basic concept is to divide each series battery array into sub-arrays where each battery is individually monitored and managed. The proposed BMS continuously monitors the voltage, current, and energy of each battery. Based on these measurements, the BMS can calculate individual State of Charge (SoC)...
The method to identify the sources of the neutral-to-earth voltage (NEV) rise as presented in a companion paper is verified in this paper through extensive simulation studies and field measurements. Sensitivity studies are conducted to determine factors that affect the performance of the proposed method. The results show that the NEV contribution factor index is effective in identifying load unbalance...
In recent years there has been increased interest in dynamic assessment of transfer capability of transmission lines in power systems based on real-time measurements of atmospheric data. The dynamic transfer capability enables the transmission system operators to utilize existing power lines more effectively and more safely with regards to critical power line temperatures and to enforce safety measures...
This paper presents a sensor fault tolerant control approach for grid connected microgrids. The proposed approach diagnoses (detects and estimates) faults in the sensed microgrid output currents using sliding mode observer theory. Once a sensor fault is diagnosed, a mitigation action follows, which controls the output currents, using the estimated fault signals. The mitigation action ensures that...
This paper studies the coordination of MMC converter protection and DC line protection in DC transmission networks. To quickly isolate a DC line fault, hybrid DC circuit breaker is connected at each end of every DC transmission line. DC line protection based on measuring derivative of DC voltage is employed to timely trip faulted DC line only. The goal of protection coordination is to prevent blocking...
Many station auxiliary transformers (SATs) in service today were not tested for complete zero sequence impedance data prior to installation. It is impractical to send them to a testing facility, and on-site testing using standard methods is difficult to perform. While it has been customary to approximate the zero sequence impedances from positive sequence data, the need for accurate zero sequence...
The main task of the state estimator in power systems is the provision of the power system state accurately. In order to achieve this, the measurement set has to be validated by identifying erroneous measurements. This is usually achieved by using either the Chi-square or the Largest Normalized Residual test. In both tests, the estimated states that are provided by the state estimator and the measurement...
Recently, many aspects of power system dynamic analysis, including oscillation identification, load model identification and system state estimation, are conducted based on the measurement data from phasor measurement unit (PMU). However, the impact of PMU measurement error, especially in power system dynamic process, has an assignable impact on these analysis results and thus cannot be neglected...
In a modern transmission system, wide area monitoring system (WAMS), which is capable to perform real time monitoring and control, is employed. State estimation process using PMU data is one of the important parts in WAMS since the current operating condition of the power system should be represented precisely. Practically, the measurement errors due to the communication congestion are existed and...
In most substation protection studies, capacitor bank parameters are derived from manufacturer nameplate values. However, the actual parameters could be different from the nominal rating as a result of manufacturing variance, assembling, material aging, and temperature dependencies. Wide manufacturing tolerance could lead to non-negligible calculation inaccuracy that affecting successive studies....
The encroachment of the measured load impedance into the outer tripping zone was one of the main problems of distance protection relays since their application. Highly loaded transmission lines intensified this issue and caused cascading failures worldwide during the last decades. Restricted zone reach settings or load blinders in the R-X-impedance plane were the common countermeasures until now....
Wind turbine controllers are generally designed for grid connected operation. Under certain grid conditions such as islanding of offshore wind farms following HVDC converter blocking, voltage and frequency of the island remains uncontrolled. Measurements in real wind farms show that the voltage in this situation can rise to unacceptably high values. In this paper the performance of the well-known...
This paper presents measurement and simulation results in offshore wind farms following blocking of the HVDC converter used for connecting the wind farm to the main onshore grid. It is shown that the voltage will rise by approximately 30% within 50–100 ms in the ensuing island operation. The process is superimposed by transients caused by short but repetitive periods of saturation of the transformer...
This paper proposes an approach for distribution system state forecasting, which aims to provide an accurate and high speed state forecasting with an optimal synchrophasor sensor placement (OSSP) based state estimator and an extreme learning machine (ELM) based forecaster.
Current transformers (CTs) are an indispensable equipment for power system current measurement. If a fault occurs in a power system, iron cores of CTs may face saturation problem and cause current measurement errors, resulting in false responses in protection relays. This research proposed a new current measurement technology using Hall integrated circuits (Hall ICs) symmetrically surrounding a power...
Phasor measurement units (PMUs) are being deployed in increasing numbers in power systems. Thus, it is not unrealistic to expect that in the not so distant future, utilization of PMU measurements directly and exclusively for static state estimation will become a viable alternative to traditional SCADA-based static state estimation. This paper considers such a future where a robust linear state estimator...
Accurate power flow in a MT system can be achieved with droop controllers. However, almost all publications have assumed that the DC voltage, DC current and DC cable resistances can be measured with 100% accuracy. In this paper, a novel power flow solver is developed which enables the user to analyse the impact of these parameters on power flow accuracy. The developed Parameter Uncertainty Power Flow...
As the power distribution grid moves towards actualizing the concept of a smart grid, the dependence of reliable and secure grid operation on the communication architecture and data is increasing rapidly, along with the possible cyber-attack surface. In this paper first an agreement algorithm for a distribution substation with radial topology is presented that leverages the communication capabilities...
Networks of phasor measurement units (PMUs) continue to grow, and along with them, the amount of data available for analysis. With so much data, it is impractical to identify and remove poor quality data manually. The data quality filter described in this paper was developed for use with the Data Integrity and Situation Awareness Tool (DISAT), which analyzes PMU data to identify anomalous system behavior...
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