Transient Stability Improvement of a Power System with Parametric Uncertainties Using a Robust Optimal H2 State Feedback Controller

This paper investigates the transient stability of power systems co-dominated\nby different types of grid-forming (GFM) devices. Synchronous generators (SGs\nand VSGs) and droop-controlled inverters are typical GFM devices in modern\npower systems. SGs/VSGs are able to provide inertia while droop-controlled\ninverters are generally inertialess. The transient stability of power systems\ndominated by homogeneous GFM devices has been extensively studied. Regarding\nthe hybrid system jointly dominated by heterogeneous GFM devices, the transient\nstability is rarely reported. This paper aims to fill this gap. It is found\nthat the synchronization behavior of the hybrid system can be described by a\nsecond-order motion equation, resembling the swing equation of SGs. Moreover,\ntwo significant differences from conventional power systems are discovered. The\nfirst is that the droop control dramatically enhances the damping effect,\ngreatly affecting the transient stability region. The second is that the\nfrequency state variable exhibits a jump at the moment of fault disturbances,\nthus impacting the post-fault initial-state location and stability assessment.\nThe underlying mechanism behind the two new characteristics is clarified and\nthe impact on the transient stability performance is analyzed and verified. The\nfindings provide new insights into transient stability of power systems hosting\nheterogeneous devices.\n

The impact of numerous distributed generators (DGs) coupled with the implementation of virtual inertia on the transient stability of power systems has been studied extensively. Time-domain simulation is the most accurate and reliable approach to evaluate the dynamic behavior of power systems. However, the computational efficiency is restricted by their multi-time-scale property due to the combination of various DGs and synchronous generators. This paper presents a novel projective integration method (PIM) for the efficient transient stability simulation of power systems with high DG penetration. One procedure of the proposed PIM is decomposed into two stages, which adopt mixed explicit-implicit integration methods to achieve both efficiency and numerical stability. Moreover, the stability of the PIM is not affected by its parameter, which is related to the step size. Based on this property, an adaptive parameter scheme is developed based on error estimation to fit the time constants of the system dynamics and further increase the simulation speed. The presented approach is several times faster than the conventional integration methods with a similar level of accuracy. The proposed method is demonstrated using test systems with DGs and virtual synchronous generators, and the performance is verified against MATLAB/Simulink and DIgSILENT PowerFactory.

This paper aims at improving the excitation control system for the doubly fed induction generator-based wind farm (WF). The proposed decentralized coordinated neural control is consisted of two controllers, i.e., a multiple model predictive controller (MPC) and an artificial neural network (ANN) controller. The MPC is based on the interaction measurement model and designed to guarantee the performance of system-wide optimization around the chosen operating points, while the ANN controller is used to calculate the weights of MPC controllers and trained to guarantee the control performance over the full operating region. The proposed control strategy allows to reduce the computational cost, and at the same time to take advantage of the distributed nature of the power system. Moreover, a simple, generic hybrid power system is used to demonstrate transient stability contributions. The problems of large-scale WF integration and its impact on transient stabilities of power systems are discussed through the eigenvalue analysis and time domain simulation. The results show that system damping and transient stability of hybrid power system are considerably improved.

This paper introduces the working principle and the mathematical model of additional power system excitation control-Power System Stabilizer (PSS). Through established a typical single machine-infinite bus power system simulation model, we simulate the synchronous generator’s transient operational characteristics following a severe disturbance. The simulation results show that the PSS can not only effectively increase the system damping, but also improve operational characteristics of the generator, considerably enhance power system dynamic and transient stability.

A novel tool for transient stability analysis of large-scale power systems: Its application to the KEPCO system

This paper proposes a method to control the output power of a wind farm with the aim of improving the transient stability of a multi-machine power system. Doubly fed induction generators (DFIG) are considered for the variable speed wind farms. The variation of the frequency of the DFIG terminal bus is used to modulate the torque reference and thus the output power of the DFIG in the post-disturbance condition. This in turn modifies the electrical power of the nearby alternators and causes improvement of stability. The proposed control technique is validated in WSCC 3-machine 9-bus system and IEEE 16-machine 68-bus system. The study is carried out in PSCAD/EMTDC as well as in MATLAB platforms.

Braking resistor is a very powerful tool to improve transient stability in a power system. Usually, a fixed value of the braking resistor is considered for the transient stability analysis. However, when the braking resistor is in operation, temperature of the resistor material rises above ambient temperature which ultimately causes the resistance value to increase. This paper analyzes the effect of the temperature rise of the fuzzy logic-controlled braking resistor on the transient stability in a multimachine power system. The performance of the braking resistor scheme with fuzzy controller is compared to that of with conventional proportional-integral-derivative (PID) controller. Simulation results of both balanced and unbalanced faults at different points in the system indicate that the temperature rise of the fuzzy logic-controlled braking resistors has little or almost no effect on the transient stability of the multimachine power system. Moreover, it is found that the performance of fuzzy logic controller is better than that of conventional PID controller. Thus, the proposed fuzzy control strategy provides a simple and effective method of transient stability enhancement.

A new measure of the relative transient stability of a multimachine power system based on the Lyapunov stability theory is introduced. Techniques of sensitivity analysis are used to determine numerically the influence of variations or errors in the estimation of the system parameters on the transient stability of a power system. In particular, data is presented for an application of these ideas to a one machine infinite bus system.

In this paper we present a robust nonlinear excitation controller of synchronous generator connected through one transmission line to an infinite bus (SMIB) to enhance transient stability. Simulation results show that transient stability of a single machine infinite bus power system under a large sudden fault can be improved.

Constructing or selecting an appropriate model is the foundation for the study of stochastic dynamics. In previous power system analysis, the disturbances to the system are mostly described by deterministic models, such as step-type models and periodic models . And deterministic time-domain or frequency-domain models are often used for system analysis. When studying the dynamic behavior of power systems under stochastic disturbances, the model must be established based on the stochastic disturbance characteristics in the power system, and it is necessary to consider how to introduce the stochastic disturbance model into the construction of the power system model. In this chapter, the ideal and measured stochastic disturbance models are presented, and a stochastic model of power system is constructed to analyze and compare the stochastic dynamic response calculation methods.

This contribution details the application of a developed interactive visual environment for power system analysis. In principle, it is based on a methodology to obtain the numerical solution of the Ordinary Differential Equations (ODEs) that represent the dynamic behavior of power systems. The methodology relies on the application of Object Oriented Programming (OOP) techniques, so that power system components can be represented as objects, which are later used as functional blocks, facilitating the representation of a system of any type of complexity. Parallel Programming (PP) techniques are also applied in order to fully exploit the capabilities of new micro-processors of executing more than one process simultaneously, with the aim of reducing the simulation time. Besides, the parallel evaluation scheme presented in this paper has shown to be effective and can be easily adapted to any other numerical integration method without the need to modify the numerical algorithm. Case studies are presented which demonstrate the effectiveness of the proposed interactive digital tool and the methodology for power system analysis.

This paper focuses on the two degree-of-freedom (2DOF) control design problem for high-speed and precision tracking system. The requirements for tracking resolution, bandwidth are transformed to the H ∞ norm minimizing problem of tracking error. A 2DOF control design approach based on an improved H ∞ linear matrix inequalities (LMI) representation is proposed. The design approach offers a new LMI to obtain the feedforward controller and feedback controller in 2DOF control scheme. The results of simulation experiment demonstrates the proposed approach could obtain a better tracking performance compared with conventional H ∞ 2DOF design based on bounded real lemma.

Preface Notation Part I. Introduction. Robust Decision Problems in Engineering: A linear matrix inequality approach L. El Ghaoui and S.-I. Niculescu Part II. Algorithms and Software: Mixed Semidefinite-Quadratic-Linear Programs J.-P. A. Haeberly, M. V. Nayakkankuppam and M. L. Overton Nonsmooth algorithms to solve semidefinite programs C. Lemarechal and F. Oustry sdpsol: A Parser/Solver for Semidefinite Programs with Matrix Structure S.-P. Wu and S. Boyd Part III. Analysis: Parametric Lyapunov Functions for Uncertain Systems: The Multiplier Approach M. Fu and S. Dasgupta Optimization of Integral Quadratic Constraints U. Jonsson and A. Rantzer Linear Matrix Inequality Methods for Robust H2 Analysis: A Survey with Comparisons F. Paganini and E. Feron Part IV. Synthesis. Robust H2 Control K. Y. Yang, S. R. Hall and E. Feron Linear Matrix Inequality Approach to the Design of Robust H2 Filters C. E. de Souza and A. Trofino Robust Mixed Control and Linear Parameter-Varying Control with Full Block Scalings C. W. Scherer Advanced Gain-Scheduling Techniques for Uncertain Systems P. Apkarian and R. J. Adams Control Synthesis for Well-Posedness of Feedback Systems T. Iwasaki Part V. Nonconvex Problems. Alternating Projection Algorithms for Linear Matrix Inequalities Problems with Rank Constraints K. M. Grigoriadis and E. B. Beran Bilinearity and Complementarity in Robust Control M. Mesbahi, M. G. Safonov and G. P. Papavassilopoulos Part VI. Applications:Linear Controller Design for the NEC Laser Bonder via Linear Matrix Inequality Optimization J. Oishi and V. Balakrishnan Multiobjective Robust Control Toolbox for LMI-Based Control S. Dussy Multiobjective Control for Robot Telemanipulators J. P. Folcher and C. Andriot Bibliography Index.

Small signal stability analysis is very much essential to find stability conditions of a power system due to lack of damping torque when small disturbances are applied. This work is intended to find the effect of wind energy conversion system (WECS) on small signal stability conditions of conventional power system with PMSG based WECS for a SMIB system. The direct drive permanent magnet synchronous generator is considered in the analysis, and the small signal model is derived to assess the small disturbance stability. The eigenvalue analysis investigates the dynamic behaviour of power system under different modes. Therefore, by using eigenvalue analysis, the relation between the modes and the state variables are obtained. By varying the controller parameters, their influence on the eigenvalues are studied. The results show that the system stability can taband grid side converter controller parameters.

This paper presents the Proportional Derivative based fuzzy PI type Static Series Synchronous Compensator (SSSC) and PSS for improving transient stability in power systems in a wide range of operating points. The three phase disturbance at various locations and various constraints are considered for system performance analysis. The positive damping torques produced by this proposed controller improves the steady state error of electromagnetic oscillations very effectively as compared with lead-lag (LL) type SSSC and PSS compensator. A three by three fuzzy logic control rule has been employed in the proposed controller adjusting the controller parameters during unpredictable disturbances in power systems. The input to the controller is generator speed deviation. Modified Sine Cosine Algorithm (mSCA) is used for optimizing problem for controller parameters. The whole work is carried out under MATLAB environment platform.