Wide-area Power System Stabilizers Research Articles

Design of a Wide-Area Power System Stabilizer resilient to permanent communication failures using bio-inspired algorithms

The operation of power systems requires a set of requirements and studies to ensure the continuous and safe supply of electricity to consumer centers. In small-signal stability studies, low-frequency oscillation modes need to be evaluated as they can compromise the operation of power systems if they are not properly damped. Many structures and control devices have been proposed to mitigate these oscillation modes and the Wide-Area Power System Stabilizers (WAPSSs) have proven to be effective in improving the damping rates of these modes as they use remote system signals from Phasor Measurement Units (PMUs). However, cyber-attacks and communication failures can affect WAPSS communication channels and affect its operation in the power system. This article proposes a method based on a multiobjective optimization model for WAPSS design that is robust to the permanent loss of one WAPSS communication channel. Bio-Inspired Algorithms are applied and compared to solve the optimization problem. A set of case studies were conducted and discussed for the IEEE 68-bus system through modal analysis and time domain simulations. The achieved results showed the need for a fault-robust damping controller and the WAPSS-type controller was able to guarantee good dynamic performance regardless of permanent communication failures. Furthermore, different bio-inspired algorithms provided different results for the closed-loop control system when applied to the proposed optimization model.

Design of a Wide-Area Power System Stabilizer to Tolerate Multiple Permanent Communication Failures

Wide-Area Power System Stabilizers (WAPSSs) are damping controllers used in power systems that employ data from Phasor Measurement Units (PMUs). WAPSSs are capable of providing high damping rates for the low-frequency oscillation modes, especially the inter-area modes. Oscillation modes can destabilize power systems if they are not correctly identified and adequately damped. However, WAPSS communication channels may be subject to failures or cyber-attacks that affect their proper operation and may even cause system instability. This research proposes a method based on an optimization model for the design of a WAPSS robust to multiple permanent communication failures. The results of applications of the proposed method in the IEEE 68-bus system show the ability of the WAPSS design to be robust to a possible number of permanent communication failures. Above this value, the combinations of failures and processing time are high and they make it difficult to obtain high damping rates for the closed-loop control system. The application and comparison of different optimization techniques are valid and showed a superior performance of the Grey Wolf Optimizer in solving the optimization problem.

Gaussian quantum particle swarm optimization-based wide-area power system stabilizer for damping inter-area oscillations

PurposeThe extensive increase in power demand has challenged the ability of power systems to deal with small-signal oscillations such as inter-area oscillations, which occur under unseen operating conditions. A wide-area measurement system with a phasor measurement unit (PMU) in the power network enhances the observability of the power grid under a wide range of operating conditions. This paper aims to propose a wide-area power system stabilizer (WAPSS) based on Gaussian quantum particle swarm optimization (GQPSO) using the wide-area signals from a PMU to handle the inter-area oscillations in the system with a higher degree of controllability.Design/methodology/approachIn the design of the wide-area stabilizer, a dead band is introduced to mitigate the influence of ambient signal frequency fluctuations. The location and the input signal of the wide-area stabilizer are selected using the participation factor and controllability index calculations. An improved particle swarm optimization (PSO) technique, namely, GQPSO, is used to optimize the variables of the WAPSS to move the unstable inter-area modes to a stable region in the s-plane, thereby improving the overall system stability.FindingsThe proposed GQPSO-based WAPSS is compared with the PSO-based WAPSS, genetic algorithm-based WAPSS and power system stabilizer. Eigenvalue analysis, time-domain simulation responses and performance index analysis are used to assess performance. The various evaluation techniques show that GQPSO WAPSS has a consistently good performance, with a higher damping ratio, faster convergence with fewer oscillations and a minimum error in the performance index analysis, indicating a more stable system with effective oscillation damping.Originality/valueThis paper proposes an optimally tuned design for the WAPSS with a wide-area input along with a dead-band structure for damping the inter-area oscillations. Tie line power is used as the input to the WAPSS and optimal tuning of the WAPSS is performed using an improved PSO algorithm, known as Gaussian quantum PSO.

A multi-objective optimization model for robust tuning of wide-area PSSs for enhancement and control of power system angular stability

A multi-objective optimization model for robust tuning of wide-area power system stabilizers (WAPSSs) aiming the improvement and control of angular stability of electric power system (EPS) is presented in this paper. In this work the WAPSSs are referred to power system stabilizers (PSSs) of fixed-structure with insertion of remote signals, from phasor measurement units (PMUs), in the control loops, that are used in a wide-area control system (WACS). The proposed model is composed of objective functions to maximize both the small-disturbance angular stability (SDAS) through the damping ratio and the large-disturbance angular stability (LDAS) using an index derived from transient energy function (TEF). Moreover, three objectives functions that contribute to the previous ones are taken into account: maximization of power system robustness for several operating conditions, minimization of eigenvalues sensitivity to small disturbances, and minimization of eigenvalues sensitivity with respect to time delay variations of remote signals. Swarm intelligence-based techniques are used to solve the multi-objective optimization model. Simulation results, with the benchmark interconnected system New England test system – New York power system (NETS-NYPS) of 16-generator and 68-bus, corroborate the applicability of the proposal.

Improved Design of Interval Type-2 Fuzzy based Wide Area Power System Stabilizer for Inter-area Oscillation Damping

The interconnection of power system due to the ever-time increase in power demand has caused inter-area oscillations as a challenge to power system stability. The present paper proposes the novel design of an Interval Type-2 Fuzzy based Wide Area Power System Stabilizer to damp the inter-area mode of oscillations for improving the power system stability. The usage of Wide Area Measurement Systems for continuous monitoring of the power grid plays a significant role in maintaining the stability of the power grid. The proposed controller uses wide-area signals from WAMS as the input signals. The controllability index calculation performs the selection of the most affected wide-area signals. The participation factor is used to identify the location of the controller. Sliding Surface approach is introduced in the controller to upgrade the performance of the controller during different operating conditions. The sliding surface approach has made the system insensitive to the parameter variations. The interval type-2 fuzzy control is a model-free approach with better control performance, due to its higher degree of freedom of interval type-2 fuzzy sets. Finally, the optimal tuning of sliding surface parameters has been considered as an optimization problem with the minimization of Integral Time Square Error using Real Coded Genetic Algorithm to enhance the damping control. The proposed Fuzzy controller has been tested in two area, four machine, 11 bus IEEE benchmark system. From the simulation responses and the comparison with different controllers, the proposed controller shows robustness and effectiveness with more accurate dynamic response and better damping of inter-area oscillations under different system operating conditions and load perturbations.

Performance of wide-area power system stabilizers during major system upsets: investigation and proposal of solutions

© 2021 Springer Nature Switzerland AG. This is a post-peer-review, pre-copyedit version of Benasla, M., Denai, M., Liang, J. et al. Performance of wide-area power system stabilizers during major system upsets: investigation and proposal of solutions. Electr Eng (2021). The final authenticated version is available online https://doi.org/10.1007/s00202-020-01168-3

Unified Smith predictor compensation and optimal damping control for time-delay power system

Wide-area signals from wide-area damping controllers have non-negligible delays during acquisition and transmission in power systems. Such delays can undermine the damping performance of wide-area power system stabilizers. To handle this type of delay, we propose an optimal wide-area damping controller considering time delay. First, the open-loop power system is linearized, and the installation locations of the controller and feedback signal are selected from geometric measurements. Then, frequency-domain identification allows to obtain the system estimation model, and a unified Smith predictor provides compensation of time delay, thus mitigating the influence of time delay on the control system. Finally, particle swarm optimization is applied to further improve the controller. The proposed controller not only eliminates the influence of time delay but also ensures robustness by automatically performing particle swarm optimization and using collaborative search of individual local and group global information to speed up convergence. Taking the two-area four-machine and New England systems for testing, simulation results show that the proposed method enhances the ability of the closed-loop system to withstand time delay and effectively improves both the damping of low-frequency oscillations and the dynamic stability of the power systems.

Cyber-Attack Resilient Design of Wide-Area PSS Considering Practical Communication Constraints

This article presents cyber-attack resilient design of wide-area power system stabilizers (WAPSSs) for damping low-frequency oscillations considering practical communication constraints. The measurements estimated by phasor measurement units (PMUs) are inherent to communication constraints such as time-delay, packet drops, and cyber-attacks. In this article, the generator terminal bus frequencies (approximately representing respective rotor speeds) are estimated by PMUs and their differences are considered as input control signals to WAPSSs. In case if the communication constraints associated with transfer of estimated frequencies are not addressed properly then they may reduce the damping capability of WAPSSs. In this context, simple and time-efficient techniques are proposed to compensate time-delay and to predict input signals in case of data drops and attacks for improving the performance of WAPSSs. A cryptographic security by means of hashed algorithms is provided to remote signals for the detection of occurrence and period of cyber-attack. The parameters of WAPSSs are tuned using a hybrid optimization algorithm. The efficacy of proposed technique is validated on IEEE 39-bus system operating under different conditions.

A Computationally Efficient Method to Design Probabilistically Robust Wide-Area PSSs for Damping Inter-Area Oscillations in Wind-Integrated Power Systems

This paper proposes an efficient method that tunes wide-area power system stabilizers (WPSSs) to have probabilistic robustness for damping inter-area electromechanical oscillations in power systems with incorporated random wind power. Specifically, the efficiency of this method benefits from unique consideration and deduction of the analytic forms of cumulative distribution functions (cdfs) of two types of random variables and their derivatives with respect to tunable parameters of the conventionally structured WPSSs, based on approximations of wind power probability density functions by Gaussian mixtures. These cdfs then compose the objective function of an optimization that can rapidly solve for optimal parameters of WPSSs by a sequential quadratic programming algorithm. The optimized WPSSs are probabilistically robust because they enhance the probability of two commonly desired control effects. Simulation studies on a modified IEEE 10-machine and 39-bus system validate the superior efficiency of the proposed tuning method and the excellent performance of the derived WPSSs.

Synchronized Versus Non-Synchronized Feedback for Speed-Based Wide-Area PSS: Effect of Time-Delay

Wide-area power system stabilizers (WAPSSs) based on time-synchronized signals are known to be relatively effective in damping inter-area oscillations. However, the use of wide-area signals introduces time-delay in the feedback loop due to the time taken in fetching the feedback information. In general, delays in the feedback loop are detrimental to the performance of the controller and may lead to instability if the control is not sufficiently robust to tolerate the delay variation. It may be the case that one opts for using non-synchronized signals (not time-synchronized) for WAPSS. This paper investigates and compares the effect of delay in synchronized and non-synchronized feedback-based WAPSS. The analysis is carried out using eigenvalue computation for time-delay systems and applied to two study systems. It is shown that non-synchronized signals are less sensitive to delay from the systems stability viewpoint even though comparable damping can be achieved.

A synchrophasor measurement based wide-area power system stabilizer design for inter-area oscillation damping considering variable time-delays

Owing to the everlasting growth of power demand and continual change in configuration of modern power system, the role of electric utility in supplying secure and reliable power has become more prominent. Presently, the ongoing interconnections of existing power system are adding more complexity to the system and consequently, making it exposed to small-signal stability issues related to inter-area oscillations. If these issues are not adhered efficiently then it may lead to system voltage collapse and even blackouts. However, incorporation of a properly designed power system stabilizer (PSS) based on information received from wide-area measurements can solve the problem. Moreover, design of such PSS is still a challenging task as the network uncertainties are highly unpredictable. The remote signals obtained through wide-area measurement system (WAMS) are needed to be transferred to control center via communication channel. However, this process makes the system subjected to inherent communication time-delays. Consequently, the performance of PSS using these signals may deteriorate if these delays are not compensated appropriately. This motivated the present work of the design of wide-area power system stabilizer (WAPSS) utilizing information contained in synchrophasor measurements for inter-area oscillation damping considering variable communication time-delays. To obtain wide-area synchrophasor measurements, phasor measurement units (PMUs) compliant to IEEE C37.118.1 principles are adopted. The variability in communication time-delays are compensated by a time-delay compensator (TDC) designed using Simevents toolbox available with MATLAB. Based on geometric measures of controllability and observability, the choice of location of WAPSSs and the selection of their respective input signal are obtained. The parameters of WAPSSs are tuned by recently proposed, simple yet efficient, Jaya algorithm (JA). Different case studies of small-signal analysis and nonlinear time-domain simulations are carried out on New England 39-bus test system operating under diverse conditions. The obtained results establish the achievement of desired performance by the JA based WAPSSs regarding inter-area oscillation damping under consideration of variable communication time-delays.

Inter‐area oscillation damping with non‐synchronised wide‐area power system stabiliser

One of the major issues in an interconnected power system is the low damping of inter-area oscillations which significantly reduces the power transfer capability. Advances in Wide-Area Measurement System (WAMS) makes it possible to use the information from geographical distant location to improve power system dynamics and performances. A speed deviation based Wide-Area Power System Stabilizer (WAPSS) is known to be effective in damping inter-area modes. However, the involvement of wide-area signals gives rise to the problem of time-delay, which may degrade the system performance. In general, time-stamped synchronized signals from Phasor Data Concentrator (PDC) are used for WAPSS, in which delays are introduced in both local and remote signals. One can opt for a feedback of remote signal only from PDC and uses the local signal as it is available, without time synchronization. This paper utilizes configurations of time-matched synchronized and nonsychronized feedback and provides the guidelines to design the controller. The controllers are synthesized using $H_\infty$ control with regional pole placement for ensuring adequate dynamic performance. To show the effectiveness of the proposed approach, two power system models have been used for the simulations. It is shown that the controllers designed based on the nonsynchronized signals are more robust to time time delay variations than the controllers using synchronized signal.

Application of Information Gap Decision Theory to the Design of Robust Wide-Area Power System Stabilizers Considering Uncertainties of Wind Power

This paper proposes the application of information gap decision theory (IGDT) to the design of robust wide-area power system stabilizers (WPSSs) with consideration of wind farm (WF) power outputs variations and transmission line outages. According to IGDT, an optimization problem is constructed to tune WPSS parameters. Then, the derived optimal WPSSs can achieve explicit and favorable robustness to ensure the required damping control effects on the interarea oscillations over a maximum variation range of WF steady-state power outputs in normal and emergent operating conditions. Moreover, with the intent of using the excellent global searching capability of particle swarm optimization (PSO), a customized PSO algorithm is proposed to efficiently solve the resulting highly nonlinear programming problem. Finally, simulations are carried out on a modified New England (10-machine 39-bus) system to validate the efficiency of the IGDT-based design method. The derived WPSSs exhibit expected robustness with respect to the wind power variations and transmission line outages.

The Impact of Time Synchronization Deviation on the Performance of Synchrophasor Measurements and Wide Area Damping Control

The phasor measurement unit (PMU) provides synchrophasor measurements for wide area dynamic security monitoring and control. Synchronism of measurements is the essential feature of PMU, whose precision directly affects the accuracy and reliability of phasor measurements. In this paper, the impacts of time synchronization deviation (TSD) on PMU measurements and wide area damping control are analyzed, respectively. Both PMUs in substations and in power plants are included in the analysis. And for each kind of PMU, the impact is elaborated systematically under steady and dynamic states. Furthermore, by studying the TSD's impact on the input signal of a wide area power system stabilizer, the influence of TSD on the effect of wide area damping control based on these two kinds of PMUs is presented. Finally, the validity of theoretical analysis is confirmed through a series of hardware-in-the-loop experiments and simulation results.

The design of delay-dependent wide-area DOFC with prescribed degree of stability α for damping inter-area low-frequency oscillations in power system

In this paper, the delay-dependent wide-area dynamic output feedback controller (DOFC) with prescribed degree of stability is proposed for interconnected power system to damp inter-area low-frequency oscillations. Here, the prescribed degree of stability α is used to maintain all the poles on the left of s=−α in the s-plane. Firstly, residue approach is adopted to select input-output control signals and the schur balanced truncation model reduction method is utilized to obtain the reduced power system model. Secondly, based on Lyapunov stability theory and transformation operation in complex plane, the sufficient condition of asymptotic stability for closed-loop power system with prescribed degree of stability α is derived. Then, a novel method based on linear matrix inequalities (LMIs) is presented to obtain the parameters of DOFC and calculate delay margin of the closed-loop system considering the prescribed degree of stability α. Finally, case studies are carried out on the two-area four-machine system, which is controlled by classical wide-area power system stabilizer (WAPSS) in reported reference and our proposed DOFC respectively. The effectiveness and advantages of the proposed method are verified by the simulation results under different operating conditions.

Design of Probabilistically-Robust Wide-Area Power System Stabilizers to Suppress Inter-Area Oscillations of Wind Integrated Power Systems

This paper proposes a systematic approach to coordinately design probabilistically-robust wide-area power system stabilizers (WPSSs) for suppressing inter-area oscillations of power systems incorporating wind power. Specifically, the operating point of the system varies stochastically due to wind power integration and each operating point corresponds to a wind power generation scenario in the steady state. Thus, the WPSSs tuned by solving a delicately formulated optimization problem can maximize the occurrence probability of scenarios where the inter-area modes possess the acceptable damping ratios, and strictly constrain their unfavorable impacts. Multiple contingencies are also directly considered. In addition, several advanced techniques are tactfully employed for accurate and efficient evaluation of occurrence probability (objective function) during the optimization so as to ensure the proposed tuning method can deal with the highly nonlinear relationships between the system eigenvalues and the steady-state power outputs of wind farms; a customized differential evolution algorithm is proposed as well to efficiently solve the formulated optimization problem. Simulations and comparisons conducted on two classic test systems with proper modifications show the effectiveness and efficiency of the proposed control design method.

Wide-area power system stabilizer design based on Grey Wolf Optimization algorithm considering the time delay

This paper proposes a method for designing wide-area power system stabilizer (WAPSS) based on the Grey Wolf Optimization (GWO) algorithm. The stabilizer is used to damp the inter-area oscillations by considering the communication latency which is related to the remote feedback signals. For this reason, a new multi-objective function is proposed for the design of the WAPSS. In this function, in addition to improving the stability of the system by displacing the critical modes, the stabilizer is designed in the minimum-phase with a less control gain. In this method, the maximum delay margin in which the closed-loop power system can remain stable can also be optimally identified.The proposed approach is tested in a small and a large multi-machine power system. The nonlinear simulation results and eigenvalues analysis have demonstrated that the approach which has been proposed in this article is highly effective in damping the inter-area oscillations as well as compensating for the destructive effects of the communication delay on the remote feedback signals.

基于模糊自整定PID的广域电力系统稳定器设计

本文主要研究广域电力系统稳定器的设计。首先分析了PID控制的原理及特点，结合模糊控制的特点提出了模糊自整定PID控制器及其控制方法，以适应电网的随机性。基于传统的PSS，制定了广域电力系统稳定器的设计流程，确定了模糊控制语言变量和隶属函数，并制定了模糊规则，对控制措施进行具体化。最后通过两区四机系统以及华东地区某电网进行的仿真测试了控制器设计的性能。仿真结果表明，这种控制器能有效适应电网的随机性，改善电力系统的阻尼，提高互联电网的稳定性。 The design of wide area power system stabilizer is studied in this paper. Firstly, the principle and characteristics of PID control are analyzed, and the fuzzy self-tuning PID controller and its control method based on the characteristics of fuzzy control are presented in order to adapt to the randomness of power network. Based on the traditional PSS, the design flow of the wide area power system stabilizer is analyzed, and the fuzzy control language variables and membership functions are determined, and the fuzzy rules are formulated to control the control measures. Finally, the performance of controller designed is tested by the simulation of Two Area and Four Machine Grid System and a region of East China. Simulation results show that the controller can effectively adapt to the randomness of the power grid, improve the damping of the power system and improve the stability of the interconnected power system.

Local and Wide-Area PMU-Based Decentralized Dynamic State Estimation in Multi-Machine Power Systems

Accurate measurement of the rotor angle and speed of synchronous generators is instrumental in developing powerful local or wide-area control and monitoring systems to enhance power grid stability and reliability. Exogenous input signals such as field voltage and mechanical torque are critical information in this context, but obtaining them raises significant logistical challenges, which in turn complicates the estimation of the generator dynamic states from easily available terminal phasor measurement unit (PMU) signals only. To overcome these issues, the authors of this paper employ the extended Kalman filter with unknown inputs, referred to as the EKF-UI technique, for decentralized dynamic state estimation of a synchronous machine states using terminal active and reactive powers, voltage phasor and frequency measurements. The formulation is fully decentralized without single-machine infinite bus (SMIB) or excitation model assumption so that only local information is required. It is demonstrated that using the decentralized EKF-UI scheme, synchronous machine states can be estimated accurately enough to enable wide-area power system stabilizers (WA-PSS) and system integrity protection schemes (SIPS). Simulation results on New-England test system, Hydro-Quebec simplified system, and Kundur network highlight the efficiency of the proposed method under fault conditions with electromagnetic transients and full-order generator models in realistic multi-machine setups.

A Novel Adaptive Wide Area PSS Based on Output-Only Modal Analysis

Usage of wide area PSSs (WAPSS) in actual power systems is limited because of their restricted adaptability to different operating conditions. Numerous adaptive control methods have been proposed to solve this problem, but they are limited due to strict prerequisites, such as the necessity of consistent excitations or large disturbances. This paper, therefore, presents a novel adaptive wide area PSS (AWAPSS), which has the ability of tracking system operating condition without the need for meeting the above prerequisites. The inherent dead-band structure of a WAPSS enables a steady system to perform like in an open loop, thus allowing the parameters of a WAPSS to be tuned adaptively through output-only modal analysis. The effectiveness of the novel AWAPSS has been validated in a two-area four-machine system as well as in a large complex system, China Southern Grid.