Stability Analysis Of Power Systems Research Articles

A General Linear Framework for Analysis of Islanded Inverter-Based Microgrids

Simulation and stability analysis of power systems are challenging topics due to nonlinear models. Fortunately, most power components are weakly nonlinear and by taking the advantages of this characteristic and also using the first-order term of the Taylor expansion, a general linear time-variant model for such systems is derived. Specifically, this article analyzes islanded inverter-based microgrids (IBMGs) using the proposed linear model driven directly from a general nonlinear model of IBMGs, and it is just as comprehensive as the reference one. Two methods to linearize the weakly and severely nonlinear state-space models are presented. A new time-step simulation is developed to modify the model dynamically and to calculate time-domain response as well as eigenvalues directly, which are much faster and more efficient than numerical methods and small-signal stability analyses. The capabilities of the proposed models make it possible to easily develop a time-saving eigenvalue calculator as well as a fast- and low computational direct power flow analysis. Different time-domain simulations in MATLAB/Simulink and other tests are investigated to verify the performance of the proposed simulations and their applications.

An Analytical Model for Small Signal Stability Analysis in Unbalanced Electrical Power Systems

This paper presents a general model to carry out a small signal stability analysis in electrical power systems (EPSs) that operate in unbalanced conditions. The classic traditional approach is based on a phase representation where it is supposed that the triphasic electric grid does not suffer any variations during its operation. With the presence of unbalances in transmission lines and loads, it is necessary to develop a general model that allows answering the needs and challenges with which modern electric systems must deal. The present work firstly intends to address the three-phase representation of an EPS, including the controllers. The proposed model is applied to a classical test system, a three machine-nine bus system, considering all the dynamic and algebraic variations associated with angular stability analysis. The proposed approach to small signal stability analysis shows results that differ from the classical analysis. The results are backed up with time domain simulations, and therefore, these results could be used in the calculation of the controllers that operate in unbalanced multimachine systems.

Comparison of Numerical Methods and Open-Source Libraries for Eigenvalue Analysis of Large-Scale Power Systems

This paper discusses the numerical solution of the generalized non-Hermitian eigenvalue problem. It provides a comprehensive comparison of existing algorithms, as well as of available free and open-source software tools, which are suitable for the solution of the eigenvalue problems that arise in the stability analysis of electric power systems. The paper focuses, in particular, on methods and software libraries that are able to handle the large-scale, non-symmetric matrices that arise in power system eigenvalue problems. These kinds of eigenvalue problems are particularly difficult for most numerical methods to handle. Thus, a review and fair comparison of existing algorithms and software tools is a valuable contribution for researchers and practitioners that are interested in power system dynamic analysis. The scalability and performance of the algorithms and libraries are duly discussed through case studies based on real-world electrical power networks. These are a model of the All-Island Irish Transmission System with 8640 variables; and, a model of the European Network of Transmission System Operators for Electricity, with 146,164 variables.

Cyber-Enabled Intelligence Control and Security Optimization for Complex Microgrid Networks Transient Frequency Stability Analysis of Power Systems considering Photovoltaic Grid Connection

In view of the photovoltaic grid-connected power system, the transient frequency stability of the system is analyzed in this paper. First, the photovoltaic grid-connected power system was modeled and analyzed. On this basis, the maximum frequency deviation is used as the index to determine the interval in which the system accommodates the maximum photovoltaic capacity, and the influence of frequency stability of the high-permeability photovoltaic high disturbance system is studied. Second, the evaluation and prediction methods of frequency dynamic characteristics of photovoltaic access nodes based on surface fitting are proposed, and the critical values of high penetration photovoltaic access for different grid points are given. Finally, an improvement measure based on the optimization of the frequency modulation parameters of large-capacity units is proposed, and the effectiveness of the proposed method in improving the transient frequency stability of the system after photovoltaic access is verified by the IEEE 39-standard system.

Imitation and Transfer Q-Learning-Based Parameter Identification for Composite Load Modeling

Fast and accurate load parameter identification has a large impact on power systems operation and stability analysis. This article proposes a novel Imitation and Transfer Q-learning (ITQ)-based method to identify parameters of composite constant impedance-current-power (ZIP) and induction motor (IM) load models. Firstly, an imitation learning process is introduced to improve the exploitation and exploration processes. Then, a transfer learning method is employed to overcome the challenge of time-consuming optimization when dealing with new identification tasks. An associative memory is designed to realize dimension reduction, knowledge learning and transfer between different identification tasks. Agents can exploit the optimal knowledge from source tasks to accelerate the search rate in new tasks and improve solution accuracy. A greedy action selection rule is adopted for agents to balance the global and local search. The performance of the proposed ITQ approach has been validated on a 68-bus test system. Simulation results in multi-test cases verify that the proposed method is robust and can estimate load parameters accurately. Comparisons with other methods show that the proposed method has superior convergence rate and stability.

Augmented Block Householder Arnoldi Method Applied in Small-Signal Stability Analysis of Power Systems

Iterative methods built on Krylov subspaces have been little explored to date for the computation of eigenvalues and eigenvectors in small-signal stability analysis. Such computation is challenging and computationally expensive for matrices with a certain number of multiple and clustered eigenvalues, conditions that can be found in many dynamic state Jacobian matrices. The present paper aims to contribute with a block algorithm to perform small-signal stability analysis with this particular type of matrix, built on the Augmented Block Householder Arnoldi (ABHA) method. The advantages of using a block method lie on the fact that the searching subspace for approximate solutions is the sum of every Krylov subspace, and therefore, the solution is expected to converge in less iterations than an unblock method. The efficiency and robustness of the proposal are examined through numerical simulations using three power systems and two other methods: the conventional Arnoldi (unblock) and QR decomposition. The results indicate that the proposed numerical algorithm is more robust than the other two for handling dynamic state Jacobian matrices having a certain number of multiple and clustered eigenvalues.

Comparação de simulações dinâmicas de máquinas síncronas entre o ANATEM – CEPEL e o modelo de dois eixos

Transient stability analysis for electrical power systems is essential for the correct functioning of the system. Thus, due to reliability and efficiency, the use of computational tools has been widely used in order to assist in studies and in the search for solutions that involve stability analysis. The number of disturbances that can affect an electrical power system is very large, and the degree of seriousness of these disorders is related to the complexity of the arrangement and the control meshes. With good approximation,   the two-axis model of the synchronous machine  connected   to an infinite bus will be used,  the problem will be implemented in the Simulink tool® of MATLAB® and after the simulation will have its results compared with results obtained with ANATEM.&nbsp

Load stability analysis of Kazakhstan photovoltaic power system based on data visualization

Traditional methods can not track the load migration of Kazakhstan photovoltaic power system dynamically, and the analysis results have limitations. Therefore, this paper introduces the data visualization method to analyze the load stability of Kazakhstan photovoltaic power system. The simulation model of photovoltaic power system is built to set the model parameters. The system stability node is obtained by using the principle of power flow calculation. The load stability analysis of the system is realized by controlling the output impedance of boost converter. In order to verify the effectiveness of the proposed method, a comparative experiment was designed. The results show that this method can control the operation state of Kazakhstan photovoltaic power system, and has a good effect on the load stability analysis of the system.

Dq-Frame Impedance Modeling of Three-Phase Grid-Tied Voltage Source Converters Equipped With Advanced PLLs

With the increased prevalence of power converters in power systems, especially three-phase voltage source converters (VSCs), the stability analysis of power electronics-based power systems has received much attention recently. To this end, different impedance models, such as the dq -domain, sequence-domain, and phasor-domain impedance models among others, have been developed for three-phase VSCs in recent years. A common trend in all these impedance models, which have no noticeable practical advantage compared to each other, is considering a standard synchronous reference frame phase-locked loop (SRF-PLL) for the synchronization of the VSC with the power grid. The standard SRF-PLL, however, has a limited filtering ability and, therefore, may not be very practical in most applications. To deal with this shortcoming of the SRF-PLL, a great number of advanced three-phase PLLs have been proposed in the literature. These advanced PLLs may have different feedback/feedforward loops and filters in their structures, which make including their dynamics in the available impedance models complicated. Bridging this gap in research is the objective of this article. To this end, it is demonstrated that advanced three-phase PLLs have an alternative representation, which can be easily obtained and included in the available dq -frame impedance model. Several case studies are presented to verify this idea.

Impact analysis of DERs on bulk power system stability through the parameterization of aggregated DER_a model for real feeders

With an ever increasing percentage of distributed energy resources (DERs) connected behind the meter in the distribution system, it is becoming increasingly important to equip transmission planners with the visibility of DER dynamic performance in distribution system. Not having visibility of the disconnection of DERs with the occurrence of transmission events, could result in an erroneous view of the stability of bulk power system.In this paper, a parameterized aggregated model (DER_a) serves as a representation of the distribution-level dynamics of real residential feeders, which is used for analysis of bulk power system stability. The parameters are obtained by executing dynamic Monte Carlo simulations. Faults are then induced at the substation level causing the DERs to trip which subsequently enables the parameterization of the low and high voltage breakpoints (vl0, vl1, vh0, and vh1) of the DER_a model’s partial voltage trip block. These parameters are then utilized to study the effectiveness of the DER_a model to represent the behavior of the aggregated DERs’ response and their impact on the bulk power system. The case study shows the ability of the positive-sequence DER_a model to provide an accurate estimation of DERs that are susceptible to trip due to 3-ϕ and 1-ϕ faults of transmission.

Quantitative short‐term voltage stability analysis of power systems integrated with DFIG‐based wind farms

With the growing penetration of doubly-fed induction generator (DFIG)-based wind farms (WFs) in power systems, short-term voltage stability problem has become more prominent. This study proposes a new approach for post-fault short-term voltage stability analysis by establishing a quantitative relationship between the system states/outputs and external disturbances. The concept of the integral-integral estimate, which is equivalent to input-to-state stability, was adopted to perform quantitative analysis at the subsystem level, and practical algorithms were developed to study the local input-to-state/output stability properties of subsystems. System-level quantitative analysis was achieved through the proposed criterion considering the stability properties of subsystems and their connections. The proposed method reveals the dynamic responses of the system under external disturbances and quantifies the size of the external disturbance that the system can tolerate, thus facilitating the operation of the power system integrated with DFIG-based WFs. The short-term voltage stability of a test power system was analysed using the proposed quantitative stability analysis approach, and the results were verified through time-domain simulations.

Dynamic equivalent method of PMSG‐based wind farm for power system stability analysis

This study presents a dynamic equivalent method of wind farms with permanent magnetic synchronous generator (PMSG) wind turbines for power system stability analysis. First, a novel clustering indicator is set up based on the morphology similarity distance and cosine similarity between trajectories with the measurable output characteristics time series of wind turbines, and the K-means algorithm is applied to cluster the PMSGs. Combining silhouette coefficient, the robustness analysis of the clustering method under different scenarios is adopted. In each cluster, a trajectory sensitivity based key parameters selection is introduced to reduce the control parameters to be identified. Moreover, a multi-objective adaptive function is established and the multi-controllers aggregated parameters are optimised by adaptive evolutionary particle swarm optimisation algorithm. Thus, a wind farm model represented by multi equivalent wind turbines is obtained. The IEEE 39-bus system with a PMSG-based wind farm is used as test system to verify the validity of the proposed dynamic equivalent approach in time domain and frequency domain, respectively. It has been demonstrated that the proposed model can reduce the model complexity and improve the calculation efficiency of wind farms.

Identification of coherent generators based on clustering methods

The identification of coherent generators is very important for the stability analysis and control of power system. So far, there are three main identification methods of coherent generators which have cetain disadvantages. In this paper, two new algorithms based on clustering are proposed for the identification of coherent generators. Algorithm 1 is the optimal classification of generators based on given swing curves. By introducing the validity index into the algorithm, the optimal classification of the given generator swing curves can be obtained. Algorithm 2 is identification of coherent generators under specific faults. This algorithm firstly calculates the critical clear time of the system. Since the swing curves obtained at the critical clear time(critical curves) contain the complete information reflecting the swing and oscillation between generators, they can be used as reliable samples for clustering. Examples show that the two algorithms are effective.

Analysis of Transient Stability for Multimachine Power System

The stability is an important guarantee for the safe and reliable operation of the power system, it is a decisive factor to limit the transmission distance and conveying capacity of the power system. Therefore, various measures must be taken to improve the system stability. The stability of the power system includes power angle stability, voltage stability and frequency stability. Among them, the power angle stability includes static stability and transient stability. Considering the importance of stability to the power system, the power system stability analysis methods and the measures to improve the power system stability is studied, so as to provide some useful reference for the safe and reliable operation of the power system. Generally, for multi-machine system transient stability becomes a major concern of wide power system due to load demand increasing day by day. In order to withstand disturbances with power quality issues requires evaluation of power system’s ability. There are many different kinds of methods for analysis of transient stability usually for multi-machine system. These methods include extended equal area criteria, time domain analysis and direct stability methods such as the transient energy function.

Analysis of Power System Stability by using Facts Devices

The existing years power structure is a big composite unified network that contains of n number of buses and hundreds of power plants. The placing of fresh positions or fixing of new generating unites executes many conservation and economic limitations. As an effect, the present transmission lines are more severely stressed than forever before and which in turn can leave power system exposed to instabilities. To continue safety of such systems, it is necessary to design appropriate procedures to expand power system safety and growth voltage stability limitations. In this project the conclusion of three FACTScontrollers – SVC, UPFC and TCSC on voltage stability are studied. The IEEE-14 bus system is simulated with continuation power flow feature of PSAT software. The benefit of this simulated model is to progress a simple, fast and appropriate procedure which can be applied efficiently to improve the voltage stability.

Optimal design of probabilistic robust damping controllers to suppress multiband oscillations of power systems integrated with wind farm

This paper proposes a general optimal design method of probabilistic robust damping controllers (PRDCs) to suppress multiband oscillations in the power system integrated with wind farm. The proposed optimal design method consists of the following two steps. In the first step, owing to the high efficiency of the probabilistic collocation method (PCM), it is adopted to investigate the probabilistic small signal stability analysis (PSSSA) of power system integrated with wind farm. In the second step, a novel adaptive compass search (ACS) with an adaptive sequence of exploration directions is proposed to enhance the global searching ability through the previous searching results, and the proposed ACS is used to obtain the parameters of the PRDCs via solving an optimization problem based on the results of PSSSA obtained from the first step. Case studies are conducted on 16-machine 68-bus system to verify the accuracy and computational efficiency of the PCM. Moreover, simulation studies are also conducted to verify the advantages of the control performances of ACS in the design of damping controllers compared with that of the traditional residue method, particle swarm optimization (PSO), grey wolf optimizer (GWO), and teaching learning-based optimization (TLBO), respectively. Finally, the effectiveness of the proposed method is validated by the time-domain simulation.

Stability and Stabilization for T–S Fuzzy Large-Scale Interconnected Power System With Wind Farm via Sampled-Data Control

This article focuses on the stability and stabilization analysis of large-scale multiarea interconnected power systems (LSMAIPSs) involving the wind farm through the Lyapunov stability theory. Instead of linearizing the nonlinear model at a certain operating point the Takagi-Sugeno (T-S) fuzzy model is able to achieve better performance. In this article, a doubly fed induction generator (DFIG)-based wind turbine systems (WTSs) are integrated into each area of the power system. The main reason behind the integration is because the power factor has the ability to destabilize the performance of the power supply. To ensure the stability of the LSMAIPS, a decentralized sampled-data feedback load frequency control is designed. The stability and stabilization conditions are derived through constructing suitable Lyapunov function which contains the sampling information and the solvable linear matrix inequalities (LMIs) along with an evaluation of H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub> performance. To an evident, the simulation results are performed based on experimental values of two-area large-scale interconnected power system with DFIG-based wind farm, which guarantees the asymptotic stability of the proposed T-S fuzzy system under the sampled-data controller.

Small Signal Stability Analysis of Multi-Area Power System

This paper focuses on methodologies for calculation and examination of oscillatory security of interconnected power system network against constant disturbances. For instance, voltage soundness, transient dependability and oscillatory behaviors are also the measure of power system stability, which must be evaluated. For that proposed strategies based on proportional integral and fuzzy logic controlling techniques are implemented. The integral controller-based technique provides the zero steady-state error and with adequate damping, time to reach steady state can be reduced, on the cost of oscillation in frequency and tie-line power. On the contrary, fuzzy logic has demonstrated that strategies of computational intelligence can alleviate the quick appraisal of oscillatory solidness with less time to reach steady state. Furthermore, Eigenvalues are constructed for small signal stability analysis, utilizing a parallel variation of Arnoldi technique, reducing the time essential for calculation of vast Multi-Area power frameworks. For exhibit purposes, models have been composed utilizing MATLAB/SIMULINK and with the assistance of the fuzzy logic.

A Distributed Cooperative Control Strategy of Offshore Wind Turbine Groups with Input Time Delay

With large-scale development of offshore wind power and the increasing scale of power grid interconnection, more and more attention has been drawn to the stable operation of wind power units. When the wide area measurement system (WAMS) is applied to the power system, the time delay mainly occurs in the signal measurement and transmission of the power system. When 10MW wind turbines transmit information through complex communication network, time delay often exists, which leads to the degradation of performance and instability for system. This affects the normal operation of a wind farm. Therefore, in this paper, the distributed control problem of doubly fed wind turbines with input time delay is studied based on the Hamiltonian energy theory. Firstly, the Port-controlled Hamiltonian system with Dissipation (PCH-D) model is implemented with the Hamiltonian energy method. Then, the Casimir function is introduced into the PCH-D model of the single wind turbine system to stabilize the time delay. The wind turbine group is regarded as one network and the distributed control strategy is designed, so that the whole wind turbine cluster can remain stable given a time delay occurring in the range of 30–300 ms. Finally, simulation results show that the output power of the wind turbine cluster with input delay converges to the expected value rapidly and remains stable. Additionally, the system error caused by time delay is greatly reduced. This control method can effectively solve the problem of input time delay and improve the stability of the wind turbine cluster. Moreover, the method proposed in this paper can adopt the conventional time step of dynamic simulation, which is more efficient in calculation. This method has adaptability in transient stability analysis of large-scale power system, however, the third-order mathematical model used in this paper cannot be used to analyze the internal dynamics of the whole power converter.

Study of stability analysis of power system with increasing wind power

AbstractThe use of energy in the world today is increasing with increase in population. The cost and availability of energy significantly impacts our quality of life, the health of national economies and the stability of our environment. The rapid depletion of fossil fuel resources on a worldwide basis has necessitated an urgent search for alternative energy sources to cater to the present day demands. In recent years there has been a significant global commitment to develop clean and alternative sources of energy such as solar and wind. Wind energy technology has been the fastest growing energy source because it is fairly distributed around the world and readily available for use. However, more penetration of wind energy into existing power networks has some impacts on the stability of the power system. Therefore, this paper studies and analyzes the stability of a power system with increasing wind penetration. The paper presents some analyses of a power system and the dynamic behavior which identify the issues that limit the large-scale integration of wind generators in a power system.