Damping Of Low Frequency Oscillations Research Articles

Stabilizer Design Based on UPFC Using Simulated Annealing

This paper presents the application of Unified Power Flow Controller (UPFC) to enhance damping of Low Frequency Oscillations (LFO) at a Single-Machine Infinite-Bus (SMIB) power system installed with UPFC. Since UPFC is considered to mitigate LFO, a supplementary UPFC like power system stabilizer is designed to reach the defined purpose. Simulated Annealing (SA) is used to tune UPFC supplementary stabilizer. To show effectiveness, the proposed method is compared with another optimization method named Genetic Algorithms (GA). Several linear timedomain simulation tests visibly show the validity of proposed method in damping of power system oscillations. Also simulation results emphasis on the better performance of SA in comparison with GA.

Stabilizer design based on UPFC using simulated annealing

This paper presents the application of Unified Power Flow Controller (UPFC) to enhance damping of Low Frequency Oscillations (LFO) at a Single-Machine Infinite-Bus (SMIB) power system installed with UPFC. Since UPFC is considered to mitigate LFO, a supplementary UPFC like power system stabilizer is designed to reach the defined purpose. Simulated Annealing (SA) is used to tune UPFC supplementary stabilizer. To show effectiveness, the proposed method is compared with another optimization method named Genetic Algorithms (GA). Several linear timedomain simulation tests visibly show the validity of proposed method in damping of power system oscillations. Also simulation results emphasis on the better performance of SA in comparison with GA.

Supplementary stabilizer design based on STATCOM

This paper presents the application of static synchronous compensator (STATCOM) to enhance damping of Low Frequency Oscillations at a single-machine infinite-bus power system installed with a STATCOM as cast study. STATCOM is considered in order to damping of Low Frequency Oscillations. Therefore, the supplementary stabilizer based STATCOM (like power system stabilizer) is designed to reach defined purpose. Optimization methods such as Particle Swarm Optimization (PSO) and Genetic Algorithms (GA) are considered to design STATCOM supplementary stabilizer controller. To show effectiveness and also comparing these two methods, the proposed methods are simulated under different operating conditions. Several linear time-domain simulation tests visibly show the validity of proposed methods in damping of power system oscillations. Also simulation results emphasis on the better performance of PSO in comparison with GA method.

Comparison of artificial intelligence strategies for UPFC supplementary controller design

This paper presents the application of STATCOM to enhance damping of Low Frequency Oscillations at a single-machine infinite-bus power system installed with a STATCOM as cast study. Since STATCOM has been considered to damping of Low Frequency Oscillations, therefore the supplementary damping controller based STATCOM like power system stabilizer is designed to reach defined purpose. Artificial intelligence methods like Fuzzy Logic schemes and Genetic Algorithms optimization are considered to design STATCOM supplementary damping controller. To show effectiveness and also comparing these two methods in damping of power system oscillations based STATCOM, the proposed methods are applied and simulated. Several linear time-domain simulation tests visibly show the validity of proposed methods in damping of power system oscillations. Also Simulation results emphasis on the better performance of Fuzzy method in compare with GA method. Simulations are carried out in MATLAB.

Pole placement approach for robust optimum design of PSS and TCSC-based stabilizers using reinforcement learning automata

Power system stability enhancement via robust optimum design of power system stabilizers (PSSs) and thyristor controlled series capacitor (TCSC)-based stabilizers is thoroughly investigated in this paper. The design problem of PSS and TCSC-based stabilizers is formulated as an optimization problem where a reinforcement learning automata-based optimization algorithm is applied to search for the optimal setting of the proposed PSS and CSC parameters. A pole placement based objective function is considered to shift the dominant system eigenvalues to the left in the s-plane. For evaluation of the effectiveness and robustness of the proposed stabilizers, their performances have been examined on a weakly connected power system subjected to different disturbances, loading conditions, and system parameter variations. The nonlinear simulation results and eigenvalues analysis demonstrate the high performance of the proposed stabilizers and their ability to provide efficient damping of low frequency oscillations. In addition, it is observed that the proposed CSC has greatly improved the voltage profile of system under severe disturbances.

Damping of low frequency oscillations in power system network using swarm intelligence tuned fuzzy controller

In this paper, a particle swarm intelligent optimisation based optimal fuzzy scheme has been developed to design intelligent adaptive controllers for improving the dynamic and transient stability performance of multimachine power system. This concept is applied to power system stabiliser (PSS) connected to a nine bus power system network having three synchronous machines. The rules of the neuro-fuzzy scheme are derived from the speed error and their derivatives. The parameters of the fuzzy logic are to be optimised for better control performance. The optimisation of the fuzzy logic parameters are performed through particle swarm intelligent algorithm. The performance of the proposed controller is analysed in multimachine power systems subjected to various dynamic and transient disturbances. The proposed particle swarm intelligent neuro-fuzzy control scheme exhibits a superior damping performance in comparison to the existing controllers. The advantage of neuro-fuzzy logic and particle swarm optimisation shows that the proposed technique is attractive for real-time implementation. The results evident that such a nonlinear adaptive PSS will yield better and fast damping, under small and large disturbances even with change in system operating conditions.

A PSO based unified power flow controller for damping of power system oscillations

On the basis of the linearized Phillips–Herffron model of a single-machine power system, we approach the problem of select the best input control signal of the unified power flow controller (UPFC) and design optimal UPFC based damping controller in order to enhance the damping of the power system low frequency oscillations. The potential of the UPFC supplementary controllers to enhance the dynamic stability is evaluated. This controller is tuned to simultaneously shift the undamped electromechanical modes to a prescribed zone in the s-plane. The problem of robustly UPFC based damping controller is formulated as an optimization problem according to the eigenvalue-based multiobjective function comprising the damping factor, and the damping ratio of the undamped electromechanical modes to be solved using particle swarm optimization technique (PSO) that has a strong ability to find the most optimistic results. To ensure the robustness of the proposed damping controller, the design process takes into account a wide range of operating conditions and system configurations. The effectiveness of the proposed controller is demonstrated through eigenvalue analysis, nonlinear time-domain simulation and some performance indices studies. The results analysis reveals that the tuned PSO based UPFC controller using the proposed multiobjective function has an excellent capability in damping power system low frequency oscillations and enhance greatly the dynamic stability of the power systems. Moreover, the system performance analysis under different operating conditions show that the δ E based controller is superior to the m B based controller.

Optimal Design of UPFC Based Damping Controller Using Iteration PSO

This paper presents a novel approach for tuning unified power flow controller (UPFC) based damping controller in order to enhance the damping of power system low frequency oscillations. The design problem of damping controller is formulated as an optimization problem according to the eigenvalue-based objective function which is solved using iteration particle swarm optimization (IPSO). The effectiveness of the proposed controller is demonstrated through eigenvalue analysis and nonlinear time-domain simulation studies under a wide range of loading conditions. The simulation study shows that the designed controller by IPSO performs better than CPSO in finding the solution. Moreover, the system performance analysis under different operating conditions show that the δE based controller is superior to the m B based controller.

Design of Robust Decentralized Control for UPFC Controller Based on Structured Singular Value

New approach based on structured singular value (µ-synthesis) was proposed for the robust decentralized unified power flow controller (UPFC) design. To achieve decentralization, using the Schauder fixed point theorem the synthesis and analysis of multi-input multi-output (MIMO) control system translated into a set of equivalent multi-input single-output (MISO) control system. Power systems similar to other industrial plants contain different kinds of uncertainties which should be considered in controller design procedure. For this reason, the idea of µ-synthesis technique being used for designing of UPFC controllers. The proposed µ-based controller had a decentralized scheme and advantage of a decentralized controller design reduction in the controller complexity and suitability for practical implementation. The effectiveness of the proposed control strategy evaluated under operating conditions on damping of low frequency oscillations in comparison with the classical controller to demonstrate its robust performance through nonlinear time simulation and some performance indices.

Damping of Low-Frequency Oscillations by Supplementary Control of Power System Stabilizers

This work presents studies of the small signal stability applied to an electric power system with the consideration of the Power System Stabilizer in operation. The Power Sensitivity Model is used to represent the electric power system. Information about the stability of the electric power system when subjected to small disturbances is obtained simulating a test system.

Comparison of Different Control Strategies in GA-Based Optimized UPFC Controller in Electric Power Systems

This study presents a study of the application of a Unified Power Flow Controller (UPFC) to control power transmission, generator terminals voltage and better damping of Low Frequency Oscillation (LFO) in Single-Machine Infinite-Bus (SMIB) power system. The UPFC integrates properties of both shunt and series compensations and can effectively alter power system parameters in a way that increases power transfer capability and stabilizes system. In practice systems use simple Proportional Integral (PI) controllers for control of UPFC. However, since the PI control parameters are usually tuned based on classical or trial-and-error approaches, they are incapable of obtaining a good dynamic performance for a wide range of operation conditions. To address this problem, in this research an optimization approach, based on the Genetic Algorithms (GA) method is proposed for the design of UPFC controllers (power-flow controller, DC-voltage regulator and generator terminals voltage controller) and also supplementary damping controller for increase damping of power system oscillations is developed. A SMIB power system installed with a UPFC is considered for case study. Several linear time-domain simulation tests visibly show the effectiveness and validity of proposed method in control of power transmission, terminal voltage of generator and enhance of LFO damping.

Analyzing the Influence of Induction Motor Inertia on Power System Low Frequency Oscillation

The influence of inertia constant (H D ) of induction motor on low frequency oscillation (LFO) is studied by integral manifolds theory. The oscillation frequency and the damping ratio are formulated in single-machine infinite bus (SMIB) system. The theoretical analysis shows that H D influences mainly the damping of LFO, the extent of which is related to the system structure and initial operating condition. The eigenvalue analysis of SMIB system and a simple two-area system shows the influence of H D on local and inter-area oscillation modes of LFO. The results of full-order system and reduced-order system by integral manifolds theory are compared.

New External Neuro-Controller for Series Capacitive Reactance Compensator in a Power Network

The controllable capacitive reactance can be used as the input variable for the external controller of a series capacitive reactance compensator (SCRC) to improve the damping of low-frequency oscillations of the rotor angle and active power in a power system. Conventional linear PI controllers are tuned for best performance at one specific operating point of the nonlinear power system. At other operating point its performance degrades. Nonlinear optimal neuro-controllers are able to overcome this degradation. In this paper, the dual heuristic dynamic programming (DHP) optimization algorithm is applied to design an external nonlinear optimal neuro-controller for the SCRC. Simulation studies using PSCAD/EMTDC/spl reg/ software are presented.

Allocation and design of power system stabilizers for mitigating low-frequency oscillations in the eastern interconnected power system in Japan

Low-frequency oscillations have been observed on trunk transmission systems in Japan, and have been the subject for studies in fields of operation, control, and devices by the many power system utilities. Power system stabilizers (PSSs) are very effective controllers in enhancing the damping of low-frequency oscillations, since the controllers can increase damping torque for inter area modes by introducing additional signals into the excitation controllers already equipped with generators. In this paper, allocation of PSSs in an interconnected power system with inter area modes has been determined by an eigenvalue analysis, and PSSs for the allocated generators have been designed by a frequency response method. The designed PSSs have been verified in a Japanese power system standard model. This test system is created as a standard model based on the trunk transmission systems in the eastern area of Japan, and reflects characteristic features of the real power systems; therefore, realistic allocation and design for enhancement of the stability of low-frequency oscillations have been verified.

PSS design for damping of inter-area power oscillations by coherency-based equivalent model

In Japan, low-frequency oscillations have been observed on trunk transmission systems, and have been the subject for studies in fields of operation, control, and devices by many power system utilities. Power system stabilizers (PSS) are very effective controllers in enhancing the damping of low-frequency oscillations, since the controllers can increase damping torque for inter area modes by introducing additional signals into the excitation controllers already equipped with generators. To analyze and solve the problem of long-term poor damping oscillation phenomena, a method is presented to find the best allocation and to design PSS for damping inter-area power oscillations. The method is based on the single-machine-infinite-bus models derived from the multi-machine power system by coherency-based reduction technique. Dynamic simulations using a 10-machine power system model are presented in order to show the effectiveness of the PSS designed according to the proposed method.

Design of power system stabiliser for single-machine system using robust periodic output feedback controller

Power system stabilisers (PSS) are added to excitation systems to enhance the damping of low-frequency oscillations. The design of PSS for a single machine connected to an infinite bus using periodic output feedback is proposed. The non-linear model of a machine is linearised at different operating points and 16 linear plant models are obtained. For each of these plants an output injection gain is obtained using the LQR technique. A robust periodic output feedback gain which realises these output gains is obtained using an LMI approach. This robust periodic output control is applied to a non-linear plant model of the machine at different operating (equilibrium) points. This method does not require the complete set of states of the system for feedback and is easily implementable.

Damping of the low-frequency oscillations of the generator: dynamic interactions and the effectiveness of the controllers

Dynamic interactions among various controllers used for stabilising a synchronous generator are investigated. The effectiveness of a power system stabiliser (PSS) connected to the exciter and/or governor in damping electromechanical oscillations of isolated synchronous generator is examined. The interaction(s) among power system stabiliser(s) connected to the exciter and/or the governor loop, automatic voltage regulator, governor and multi-stage double-reheat turbine and dynamic load are considered. It is shown that depending on the type and number of controllers used and dynamics modelled, interactions can result in unstable operation of the system for a range of operating conditions. It is also shown that the power system stabiliser connected to the governor loop provides better damping of low-frequency oscillations and better robustness of the generator to a change in operating conditions than the PSS connected to the exciter loop.

The Effect of Load Models on Unstable Low-Frequency Oscillation Damping in a Longitudinal Power System

This paper uses the eigenvalue analysis approach to observe the influence of load models on the electromechanical oscillation mode phenomena during an unstable low-frequency oscillation incident which recently occurred on the Taiwan power system. Three kinds of the derived load models (dynamic model, composite model, and exponential model), based on the component approach with measured characteristic of power system loads, are used. Time simulations are compared with field test results. These are thus extensively used to verify the eigenvalue analysis results and to evaluate the mean of the respective load models.

Effect of Load Models on Unstable Low-Frequency Oscillation Damping in Taipower System Experience with and without Power System Stabilizers

This paper uses the eigenvalue analysis approach to observe the impact of load models on an unstable low-frequency oscillation damping, which recently occurred in the Taiwan power system. In order to enhance oscillation damping, the effect of load models on power system stabilizers is also investigated. Three kinds of the derived load models (a dynamic model, a composite model, and an exponential model) based on the component approach with the measured characteristics of power system loads are used in this paper. Time simulation results are used extensively to verify the eigenvalue analysis results with and without power system stabilizers. One set of field test data obtained from the Taiwan power nuclear plant with power system stabilizers is used to determine which load model provides a more accurate result in enhancement of oscillation damping. Depending on the results, the effect of load models on electromechanical oscillation damping with and without power system stabilizers is verified.

The effect of load models on unstable low-frequency oscillation damping in Taipower system experience w/wo power system stabilizers

This paper uses the eigenvalue analysis approach to observe the impact of load models on an unstable low frequency oscillation damping, which recently occurred in the Taiwan power system. In order to enhance oscillation damping, the effect of load models on power system stabilizers is also investigated. Three kinds of the derived load models (a dynamic model, a composite model, and an exponential model) based on the component approach with the measured characteristics of power system loads are used in this paper. Time simulation results are extensively used to verify the eigenvalue analysis results with and without power system stabilizers. One set of field test data obtained from the Taiwan power nuclear plant with power system stabilizers is used to determine which load model provides a more accurate result in enhancement of oscillation damping. Depending on the results, the effect of load models on electromechanical oscillation damping with and without power system stabilizers is verified.