Panagiotis N. Papadopoulos

Probabilistic Framework for Transient Stability Assessment of Power Systems With High Penetration of Renewable Generation

This paper introduces a probabilistic framework for transient stability assessment (TSA) of power systems with high penetration of renewable generation. The critical generators and areas of the system are identified using a method based on hierarchical clustering. Furthermore, statistical analysis of several transient stability indices is performed to assess their suitability for TSA of reduced inertia systems. The proposed framework facilitates robust assessment of transient stability of uncertain power systems with reduced inertia.

Measurement-Based Hybrid Approach for Ringdown Analysis of Power Systems

System identification methods have been widely used for the study of low frequency electromechanical oscillations and the development of low order dynamic models. This paper introduces a hybrid frequency/time-domain approach to estimate the dominant modes contained in ringdown responses of power systems. Practical issues and solutions encountered in the application of the hybrid method are discussed. The performance of the proposed technique is evaluated by applying the Monte Carlo method to synthetic signals and simulated responses from a large-scale power system, as well as to measurements recorded in a microgrid laboratory test facility. Results in all cases proved to be very accurate, verifying the robustness of the proposed method.

Dynamic modeling of a microgrid using smart grid technologies

In this paper a dynamic equivalent model of a microgrid based on Prony analysis is presented. The model parameters are considered to be derived from measurements using parameter estimation techniques. Fourier analysis is also used to study the frequencies involved in the transient response of the system. A microgrid with synchronous generators and inverter-interfaced units is studied and the effect of increased inverter penetration is also examined. Results for various transient disturbances such as changes in the synchronous generators torque, load changes and changes in the inverters setpoints are presented.

Impact of penetration of non-synchronous generators on power system dynamics

Due to the integration of Distributed Energy Resources (DERs), both non-synchronous generators and energy storage technologies, the dynamic behavior of power systems is changing. The extent of the impact is yet to be fully investigated and quantified. Proper models, suitable for large scale studies but also representing all the DER control and protection mechanisms that affect the dynamic behavior of individual components and the system as a whole are used in this study. The effect of DER location, penetration level and decommissioning of conventional generators is studied. A Monte Carlo approach is used to account for uncertainties resulting from different fault location, duration and loading of the system. The focus of the paper is to illustrate the effect of DERs on power system stability and dynamic signature.

Dynamic modelling of a grid-connected PEM fuel cell in a distributed generation network

This paper presents a dynamic Proton Exchange Membrane Fuel Cell Model (PEMFC) model based on mass balance and semi-empirical equations. A complete PEMFC System containing a Power Conditioning Unit (PCU) is also investigated and various scenarios are simulated to assess the behaviour of a grid-connected FC in a Distributed Generation (DG) network.

Online parameter identification and generic modeling derivation of a dynamic load model in distribution grids

The advent of smart grids and the installation of phasor measurement units in the distribution network have renewed the interest on the measurement-based load modeling approach. In this paper, a real-time load modeling and identification procedure of the well-known exponential recovery dynamic load model using synchrophasor data is presented. The performance of the proposed method is evaluated using measurements recorded in a low-voltage laboratory scale test rig. Several parameters of the procedure are investigated to evaluate the applicability of the method under real world conditions, including the impact of filtering techniques, outlier rejection, model optimization algorithms, etc. The findings of this paper verify the validity of the proposed method for realtime applications.

A framework to assess the effect of reduction in inertia on system frequency response

This paper presents a framework to analyze the impact of different penetration levels of renewable generation sources (RES) and consequent reduction in inertia on grid frequency. The developed methodology is demonstrated using three operating conditions of the network. For each operating condition, the decrease in the network loading is balanced by disconnecting a part of synchronous generation. To establish the critical penetration levels of renewables and inertia limits for the grid frequency, the uncertainty of loads, intermittent and stochastic patterns of RES generation around each operating condition are simulated. The results clearly identify the critical penetration levels of RES and reduction in inertia limits of the system for frequency stability. In addition, the performed analysis quantifies the effect of primary frequency response and reduction in inertia on frequency nadir. The proposed framework is applied to the modified 16 machine and 68 bus network.

Comparison of ensemble decision tree methods for on-line identification of power system dynamic signature considering availability of PMU measurements

This paper compares the most commonly used ensemble decision tree methods for on-line identification of power system dynamic signature considering the availability of Phasor Measurement Units (PMU) measurements. Since previous work has shown that the surrogate split method included in classification and regression tree is not good enough to handle the unavailability of measurement signals, more effective methods are needed to be explored. Bagging, boosting and random forest methods are investigated and compared in this work. When evaluating their performance, all possible scenarios of missing PMU measurements are tested for the test network. For each ensemble decision tree model, the result is presented as a probabilistic classification error depending on the availability of PMU signals. The test network used is the 16-machine, 68-bus reduced order equivalent model of the New England Test System and the New York Power System.

Probabilistic Framework for Online Identification of Dynamic Behavior of Power Systems With Renewable Generation

The paper introduces a probabilistic framework for online identification of post fault dynamic behavior of power systems with renewable generation. The framework is based on decision trees and hierarchical clustering and incorporates uncertainties associated with network operating conditions, topology changes, faults, and renewable generation. In addition to identifying unstable generator groups, the developed clustering methodology also facilitates identification of the sequence in which the groups lose synchronism. The framework is illustrated on a modified version of the IEEE 68 bus test network incorporating significant portion of renewable generation.

Probabilistic assessment of transient stability in reduced inertia systems

A probabilistic approach to assess the transient stability of power systems with increased penetration of wind and Photo-Voltaic generation is presented in this paper. The impact on transient stability due to the intermittent behavior of Distributed Energy Resources (DERs) as well as due to their dynamic response when a disturbance happens is investigated. Moreover, the effect of conventional generation disconnection and consequently inertia reduction is studied. Apart from calculating transient stability related indices, a clustering technique is also applied to provide more information considering the impact of DERs and conventional generation disconnection on transient stability.