Voltage Stability Analysis Of Power System Research Articles

Impact of Probabilistic Modelling of Wind Speed on Power System Voltage Profile and Voltage Stability Analysis

Wind speed characteristics may have a significant impact on the power system operation, stability and dynamics. Hence, appropriate modelling and quantification of wind probability distribution function (PDF) are critical for probabilistic power system analysis. Weibull distribution is the most widely used PDF for power system (particularly power system stability) studies, which might not be a valid PDF for different wind regimes having high, average, and low wind speed data. In this study, twenty different wind speed datasets (each dataset is different based on the location, duration, and resolution) have been collected and analysed with eight PDFs to model the wind speed to replicate different wind speed characteristics. The PDFs include Rayleigh, Weibull, Gamma, Lognormal, Normal, Inverse Gaussian, Generalized Extreme Value, and Exponential distributions. Root mean square error (RMSE) and the coefficient of determination (R2) are applied as the measure of accuracy. The obtained results show that the locations, duration, and resolution have a notable impact on the selection of suitable PDFs. It was found that the Gamma distribution is the best-suited PDF for representing low wind speed data. In comparison, the Weibull distribution represents the best PDF for high wind speed data. Also, the selection of the Gamma PDF for low wind speed data and Weibull distribution for high wind speed data is further validated by presenting voltage profile and voltage stability analysis. Study outcomes would assist power system planners to select the appropriate PDF for power system stability studies based on the characteristics of the available wind speed dataset.

Power System Voltage Stability analysis with Renewable power Integration

The purpose of this research is to find the loading limit of a power system before hitting voltage instability and to assess the margin to voltage instability of a system consisting of a wind farm. An index called Bus Apparent Power Difference Criterion (BSDC) is used to find maximum loadable point. The measure depends on the way that in the region of the voltage collapse no extra apparent power can be delivered to the affected bus. The analysis is performed combination of wind power injection at different wind speeds and line outages in the network. In the feasibility and siting studies of wind farms the steady state analysis with network contingencies give the utility or the developer a sense of network condition upon the injection of power in the network. However, the extent of voltage stability impacted due to load growth in the system is not assessed. The research paper makes way to assess the impact on voltage stability margin with obtaining the maximum loadable point of the system and assessing the best suited bus to integrate a wind farm into the system.

Dynamic Thévenin equivalent and reduced network models for PMU-based power system voltage stability analysis

Abstract Measurement-based real-time voltage stability assessment methods typically use a Thevenin Equivalent (TE) model. The TE is computed under the assumption that all generators and loads seen from an individual load-bus are constant during the time-window when measurements are obtained. This assumption does not hold in actual power systems. In fact, load changes at other load-buses result in variations on the voltage of a single-port equivalent model of the power system as seen from a load-bus. To consider these variations, this paper uses an interpolation method to develop a dynamic TE model from synchrophasor measurements, which is suitable for measurement-based real-time voltage stability assessment. In addition, a reduced network model is proposed to separate and quantify the impact of other loads and generators on the voltage stability of an interested load-bus in networks without full observability. The proposed method has been assessed through various simulation scenarios, and illustrated using actual field measurements.

Analiza wpływu źródeł fotowoltaicznych na stabilność napięciową systemu elektroenergetycznego

The paper presents methods of modeling complex load model with photovoltaic sources for analysing the power system voltage stability. The survey was supplemented with examples of analysis of voltage stability using described models of complex load. In the study, the stability margin was determined using P-V curves determined by means of the Power Factory program. The obtained results indicate that the modeling of complex load with photovoltaic cells has a significant impact on the assessment of the power system voltage stability (Analysis of the impact of photovoltaic generation source on power system voltage stability).

An approach to determining the local boundaries of voltage stability region with wind farms in power injection space

A new approach to determining the local boundaries of voltage stability region in power injection space (IVSR) for power system with wind farms is presented. It can be used for power system voltage stability analysis and on-line security assessment with considering the output uncertainty of the wind farms. Firstly, power flow tracing and double dispatching are used to determine the generators that are closely related to the wind farms, in order to balance the power fluctuations caused by the wind speed variation. Then, modal analysis is used to get the key generators to achieve an effective dimension reduction for IVSR. Finally, the forecasting output power (or wind speed) of wind farms is divided into several intervals. For each interval, the corresponding local IVSR boundaries can be calculated by the method based on small disturbance. Moreover, parallel process is used to accelerate the computing speed. The presented approach is validated by several power systems. It can be revealed that the approach can give the local IVSR boundaries at different wind speeds and has a good engineering application prospect.

Local bifurcation in power systems: theory, computation, and application

This paper provides an of overview of local bifurcation theory and its application to power system voltage stability analysis. The qualitative behavior of power system dynamics as modeled by differential-algebraic equations is discussed, followed by a summary of the concepts and tools for the analysis of local bifurcation from equilibria. Computational methods for locating and classifying bifurcation points as they have been applied in power system analysis are reviewed. Several examples are given.

Voltage stability assessment of isolated power systems with power electronic converters

This paper extends the concept of small signal models to the frequency domain and then presents a new method for isolated power system voltage stability analysis. An approximation for the voltage and reactive power relationship of the cycloconverter is proposed and verified by time domain simulation. Small signal models for various nonlinear, power system components including power electronic converters are derived, based upon which, the incremental network of the system is formed. The voltage stability indices of various buses, which are defined in the bus impedance matrix of the incremental network, can be calculated using the conventional factorisation method without the need to determine the matrix eigenvalues and eigenvectors. The model and algorithm can also be used to predict the stiffness of the system with respect to voltage fluctuations during operation.