Wide-area Damping Controller Research Articles

Enhancing damping of low‐frequency oscillations in power networks through energy storage system‐based controller

SummaryMitigating inter‐area low‐frequency oscillations is a significant concern in multi‐machine power systems due to their adverse effects on system stability. These oscillations are intricately linked with power oscillations. So appropriate power modulation through the Battery Energy Storage System (BESS) can be an effective strategy for preserving system stability. In this paper, the maximal of all minimal residue indices under variations in power system operating conditions is utilized as the index for identifying the location for installation of the BESS, the damping control loop, and the feedback signal. A fixed‐structure scheme‐based wide‐area damping controller (WADC) is proposed for the BESS, providing sufficient damping of inter‐area oscillation modes. A modified IEEE 39‐bus system is simulated using a real‐time digital simulator as a test system in this work. The simulation results confirmed that the proposed WADC could effectively damp various inter‐area oscillation modes. Furthermore, it offers robust damping performance over contingencies associated with the system's various operating scenarios as well as the uncertainty associated with fixed and variable communication delays in the feedback signal of WADC and the integration of solar photovoltaic systems. Moreover, a comparative analysis of the proposed WADC is carried out with a BESS‐based wide‐area power system stabilizer, which is found to be more effective in mitigating system inter‐area oscillations.

Synchronous and non synchronous delay-dependent robust wide-area controllers for power system

Wide-area control is highly efficacious for maintaining sufficient damping of the low-frequency oscillations in the power system. The Wide-Area Measurement System (WAMS) provides wide-area signals to the control site through a communication channel. Even though the wide-area signal improved the dynamic behavior of the power system, a time delay usually exists during the transmission, which is unavoidable. The damping performance of the power system is degraded due to the time delay. In this paper, synchronized and non-synchronized feedback configurations are considered, and the time delay margin is calculated. The Lyapunov theory is adopted for investigating the synchronous and non-synchronous delay-dependent stability criteria for the power system. A lead–lag and a robust H∞ wide-area damping controller (WADC) are proposed to measure the delay margin for synchronized and non-synchronized delay feedback. The relationship between the damping performance and the delay margin is established. It is observed that a non-synchronous feedback-based controller can endure a larger time delay variation than a synchronous feedback-based controller. The nonlinear simulation is carried out to verify the effectiveness of the proposed controllers in Kundur’s two-area system and the IEEE-39 bus test system.

Improving the time delay in the design of the damping controller with the aim of improving the stability of the power system in the presence of high penetration of renewable energy sources

Due to the high penetration of renewable energy sources (RES) such as wind units in power systems, the need to check the stability of transmission networks has been given more attention than before. Therefore, in this paper, due to the importance of the topic, the wide area damping controller (WADC) has been used for the battery energy storage system (BESS) connected to the photovoltaic unit and the permanent magnet synchronous generator (PMSG) in the dc link. The WADC design is based on free weight matrices (FWM), which can solve a set of constraints based on the linear matrix inequality (LMI) based on the delay-dependent feedback control theory. The working method is that the constraints related to LMI are considered in such a way that it has the ability to tolerate the maximum amount of time delay. FWM has been used to communicate between LMI constraints and the maximum value of the time delay margin. FWM matrices are also based on an iterative algorithm based on linearization of the conical complement, which tries to search for the most optimal value for the control parameters. To implement the simulation results in MATLAB software, an improved power system of 16 machines has been used, the results of which are clearly analyzed and show the superiority of the proposed method compared to other mentioned methods.

A robust damping control for battery energy storage integrated power systems to mitigate inter-area oscillations

This paper presents the effect of a Battery Energy Storage System (BESS) on the power system inter-area oscillations under changing load conditions. The dynamic interaction between the BESS control modes and synchronous generators, along with BESS control parameters, influence the damping of prominent inter-area oscillations under different loading conditions. Furthermore, H∞ mixed sensitivity scheme-based Wide-Area Damping Controller (WADC) is proposed for BESS. This controller is designed using the Linear Matrix Inequality (LMI) framework to mitigate the prominent inter-area oscillation of the power system. Sensitivity to control parameter variation and the geometric measure of the observability are utilized to select the location and feedback signal for the WADC. The performance of the proposed WADC is compared with an Energy Storage System-based stabilizer and WADC proposed in an existing work on a modified New England ten-machine benchmark system. The Real-Time Digital Simulator (RTDS) platform is used to assess the real-time viability of the proposed WADC. The simulation results demonstrate that the proposed WADC can effectively diminish several inter-area modes. Additionally, it offers robust performance under varying load conditions, contingencies and with communication delays in feedback signals. The proposed controller is also effective under the system integrated with Doubly Fed Induction Generator-based Wind Turbine System.

Robust damping control for integrated wind turbine power networks during low inertia condition

AbstractThis paper presents a modal analysis‐based impact analysis of the change in system inertia due to the integration of the large‐scale doubly fed induction generator (DFIG)‐based wind turbine system (WTS) on the power system damping in inter‐area oscillation modes. The impact of replacement of a synchronous generator by WTS of same MVA capacity on system dynamics such as emergence of new critical modes of inter‐area oscillations affecting system stability is studied. Further, a double‐channel scheme‐based wide‐area damping controller (WADC) is proposed for WTS, which provides sufficient damping of prominent oscillation modes and enhanced stability margin to alleviate the negative impact of reduction in system inertia. The comparative assessment of the proposed controller with a PSS‐based WADC on a modified New England 10‐machine system validates the performance and is found to be more effective in mitigating inter‐area oscillation in the system. The real‐time feasibility of the proposed double‐channel WADC is evaluated on the Real‐Time Digital Simulator (RTDS) platform. The simulation results show that the proposed WADC can successfully mitigate various inter‐area modes simultaneously. Furthermore, it provides robust performance for a variety of contingencies, time delays in feedback signals, and uncertainties associated with different operating scenarios of WTS.

Structurally Constrained Fuzzy Selective LQ WADC Based on the Spectral Decomposition of Gramians

We propose a number of improvements for a previously presented method of selective wide-area damping control (WADC) using spectral decomposition of Lyapunov equation solutions. Namely, accounting for structural constraints, fuzzy selectivity, and compatibility with global optimization methods. We demonstrate that the improved method is capable of providing useful WADC strategies when the availability of measurement data is severely limited.

An Improved Smith Predictor for Wide-Area Damping Control Considering Time-Delays in Power System

An Improved Smith Predictor for Wide-Area Damping Control Considering Time-Delays in Power System

Robust design and best control channel selection of FACTs-based WADC for improving power system stability using Grey Wolf Optimizer

With recent advances in wide-area measurement systems (WAMS), wide-area damping controllers (WADCs) based on remote signals can effectively damp inter-area oscillations. However, these signals are inherently subjected to communication time-delay which may adversely affect the damping of inter area oscillations. The purpose of this paper is to present a optimization-based method for designing a WADC for a static synchronous series compensator (SSSC) to improve the damping of inter-area oscillations by considering the time delays of remote control signals. For this aim, the control gain value of the WADC, shifting of the critical modes to a desirable area, and the maximum time delay margins are simultaneously considered as an objective function. Moreover, to design a WADC as minimum-phase structure, the suitable constraints have been determined and added to the objective function as penalty factors. A grey wolf optimization (GWO) algorithm is utilized to solve the optimization problem. Robustness of the designed SSSC-based WADC in amplitude and phase control channels against the time delay has been compared and then the best control channels to damp inter-area oscillations has been selected. Based on simulations and statistical results conducted on 4 and 50 machine multi-machine power systems, it is evident that the proposed method based on the GWO outperforms other techniques in achieving the optimal design of a SSSC-based WADC for damping inter-area oscillations.

Distributed Generation Based WADC for Inter-Area Oscillations Considering Unknown Inputs

Inter-area oscillations (IAOs) are one of the main problems for contemporary power systems because of their low-damping characteristics. Additionally, the damping behaviors of IAOs might be further deteriorated by the addition of low inertial distributed generation (DG) to the power system. Therefore, a novel wide-area damping controller (WADC) for DG-integrated power systems is developed utilizing a modal linear quadratic regulator (LQR) technique that only targets essential IAOs without degrading other local modes. The states participated in linear combination from modal LQR are generally unavailable and need to be estimated. Full order observers are frequently used in literature, although they may not function if some inputs are unavailable. Hence, an unknown input observer (UIO) is suggested in this paper to estimate the states despite certain inputs being unknown. The proposed methodology is then tested on a DG-integrated 4-machine, 11-bus system and 10-machine, 39-bus system to validate the overall proposed design process. Results show that the proposed WADC successfully dampens the crucial IAO modes by 10% and 15% while not degrading other modes of the system.

STATCOM-Based Intelligent Wide-Area Controller for Damping Interarea Oscillation

This article presents an online scheme of static synchronous compensator (STATCOM)-based wide-area damping controller for interarea oscillation based on the oscillatory signals from a wide-area measuring system. For this purpose, by evaluating the rotor angles and speed deviations between coherent groups and providing them into the center-of-inertia frame, interarea signals are provided. For estimating controlling gains, using two classification and regression techniques (CART <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> and CART <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) as intelligent gain estimators, controlling gains <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">K</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">K</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> are estimated. In this case, each wide-area damping controller (WADC) consists of an intelligent STATCOM with global control signals for adjusting the line susceptance. The proposed classification and regression trees (CARTs) are trained offline in which by using interarea signal (IASs) through real-time evaluations, global controlling signals (GCGs) are estimated. It is an online nonmodel-based controller that estimates the STACOM susceptance based on the interarea oscillations. The effectiveness of the proposed STATCOM-based wide-area controller (SWADC) is evaluated on the New England 39-bus test system and practical Iran nation power grid with the potential of different interarea oscillation patterns. Results present the promising effects for damping the interarea oscillations.

Assessment of Bus Inertia to Enhance Dynamic Flexibility of Hybrid Power Systems With Renewable Energy Integration

The integration of renewable energy resources and employment of multi-terminal dc links have dramatically transformed the structure of traditional power systems into hybrid networks with reduced inertia levels. Therefore, the new paradigm requires a coherent architecture for computing the spatiotemporal distribution of total system inertia. With this objective in mind, a novel approach is proposed in this paper for calculating bus inertia that captures power system dynamics and facilitates the real-time computation of grid flexibility. The bus inertia is defined as the distribution of the total inertia across all system buses located in different geographical regions. In this context, a simplified mathematical formulation for bus inertia computation is developed that does not require a linearized model for hybrid power systems. In the existing methods, linearizing the whole power grid is complex, computationally challenging, requires mathematical modification for any change in systems and not rigid enough in terms of accuracy. The computation of bus inertia can be used during planning and operation phases that span long and short-time horizons to enhance system flexibility. Furthermore, it assists in identifying the spatial system strength for any area or zone. Consequently, the proposed method can be further utilized to meet the increasing penetration levels of renewable energy resources (RES) and enhance grid flexibility. The computed bus inertia (and eventually system inertia) can also be applied for load shifting, allocation of wide-area damping controllers (WADCs), coherency detection, relay setting, sitting of RES and energy storage systems (ESS) to ensure stable and flexible operation of the power grids. The efficacy of the proposed method is tested and verified using the two-areas, four machines test system, IEEE 39 bus, IEEE 68 bus and IEEE 118 bus standard test systems.

Wide-Area Measurement-Based Two-Level Control Design to Tolerate Permanent Communication Failures

The operation of modern power systems must meet stability requirements to guarantee the supply of electrical energy. One of these requirements is to ensure that the low-frequency oscillation modes have high damping ratios to avoid angular instability and future power system blackouts. Advances in phasor measurement units (PMUs) have contributed to the development and improvement of wide-area damping controllers (WADCs) capable of increasing the damping rates of the oscillation modes of the system, especially the inter-area modes. Nevertheless, the operation of WADCs is vulnerable to communication failures and cyber-attacks, and if not properly designed the WADC can affect the stability of the entire system. This research proposes a procedure for designing a WADC robust to permanent communication failures using a linear quadratic regulator (LQR) and genetic algorithms. Case studies conducted on an IEEE 68-bus test power system show the effectiveness of the WADC designed by the proposed procedure even when communication failures are occurring in the system. The use of genetic algorithms improves the convergence and results of the LQR-based method.

Resilient Wide-Area Damping Control to Mitigate Strong Cyber Attack: A Multiple-Controller Switching Approach

The growing risk of cyber attacks targeting wide-area damping control (WADC) has spawned much research on designing attack-resilient controllers recently. However, the issue of attack strength did not get enough attention so that most existing resilient WADCs may fail to defend strong attacks. To address this problem, this paper proposes a multiple-controller switching approach based resilient wide-area damping controller (MCS-RWADC) to suppress inter-area oscillations and mitigate strong attacks. It is inclusive of multiple secure networked prediction control based modules (SNPMs) and a switch-monitor module (MSM). The SNPM can detect attacks, differentiate attack strength and compensate for weak attacks. In terms of strong attacks, multiple SNPMs are implemented to work as backup and three operating states as well as the corresponding switching rules are designed to realize automatic switching among them. MSM is responsible for monitoring the states and directing the switching. Case studies are conducted on a 4-area 5-terminal voltage source converter-based multi-terminal high voltage direct current based offshore wind farm integration system. Simulation results verify MCS-RWADC cannot only suppress the inter-area oscillation but also handle the strong attacks under a wide range of operating conditions with various wind power output.

Damping of Inter-Area Oscillations Using TCPS Based Delay Compensated Robust WADC

Low-frequency oscillations (LFOs) pose a significant obstacle in achieving optimal power flow and utilizing transmission corridors in large interconnected power systems. In this study, linear matrix inequality (LMI) base robust wide-area damping controller (WADC) is introduced to effectively address critical LFOs. The proposed WADC utilizes wide-area signals, which modulate the phase angle of a thyristor-controlled phase shifter device. To ensure that the concerned modes of LFOs lie in left half of the complex plane, a D-space sub-region approach is applied. However, using wide-area signals introduces time delays, which negatively impact the efficacy of the WADC; hence, a time delay compensator (TDC) is incorporated into the feedback path of the signals. The proposed approach involves four key steps: selecting feedback signals using a combined modal transformation and geometric approach, designing an appropriate TDC, building a generalized plant with mixed sensitivity weights, and solving the LMI. The dynamic efficacy is verified on IEEE 4-machine 11-bus system, and 10-machine 39-bus system. Poorly damped single and multiple critical modes are placed in the D-space region of interest with specified damping ratios viz. 10% and 15%. Furthermore, damping ratios of critical modes are maintained with TDC based proposed WADC while deteriorating with other counterparts.

Interacting Multiple Model Strategy Based Adaptive Wide-Area Damping Controller Design for Wind Farm Embedded Power System

The intermittent nature of Wind Turbine Systems (WTSs) can severely affect the Low-Frequency Oscillations (LFOs) in the power system. Hence, a Wide-Area Damping Controller (WADC) is designed in this paper to provide adequate damping to critical LFO modes. This WADC utilizes a modal-based prescribed degree approach, ensuring the specified shift of concerned modes from their existing position. However, the design of WADC at a fixed operating point and time delay in feedback signals does not provide robust performance as these uncertainties may vary for different time intervals. Specifically, time-varying delays should be tackled appropriately, or the system's damping performance will be severely hampered. Keeping this in view, an Interacting Multiple Model (IMM) infrastructure is employed to provide robust damping performance for such uncertainties. The IMM strategy utilizes the deviation of output error between actual and probable plants, through which weights are assigned to corresponding probable WADCs via the Bayesian framework. The simulations are performed on the nonlinear 4-machine, 11-bus system and the complex 16-machine, 68-bus system using MATLAB/Simulink platform. The results demonstrate that the proposed IMM-based WADC furnishes adequate damping to critical LFO modes for operating point and time delay uncertainties.

Optimal design and control loop selection for a STATCOM wide-area damping controller considering communication time delays

Wide-area damping controllers (WADC) have been shown to be effective in damping interarea oscillation modes. The varying nature of power system operating point requires the design of an adaptive WADC. Majority of the existing control design techniques rely on empirical approaches at one or more of their design stages, which makes it difficult to implement in adaptive control techniques. Therefore, the purpose of this study is to provide a systematic procedure based entirely on numerical approaches for designing a STATCOM-based WADC. The proposed procedure involving control loop selection, control design and adaptive time delay compensation, can then be implemented in adaptive WADC schemes. Geometric analysis has been used to choose the STATCOM location. Then, a novel optimization-based signal selection methodology is proposed. The proposed methodology employs a combination of multiple input signals to optimally generate a signal with the required modal objectives like enhancing observability and reducing interaction between different control loops. After that, another optimization problem is formulated to tune the controller parameters using integral of time multiplied by absolute error (ITAE) as the optimization objective. Both optimization problems have been evaluated using two optimization techniques: Particle swarm optimization (PSO) and self-adaptive multi-population elitist Jaya algorithm (SAMPE-JAYA). Finally, an adaptive delay compensator is designed to mitigate the effects of communication time delays. The proposed control strategy is applied on the IEEE 68-bus system and the controller performance is evaluated by modal analysis and multiple time-domain simulation scenarios.

Design and analysis of modal resonance-oriented cyber-attack against wide-area damping control

The existence of cyber-attacks has brought great challenges to the stability of cyber physical power system (CPPS). Moreover, the modal resonance issue as one of the emerging stability issues should be carefully investigated in power systems dominated by power electronics. Hence, this paper proposes a potential modal resonance-oriented cyber-attack (MROCA) against wide-area damping control (WADC) and investigates the impact of the attack on the stability of CPPS. In the design of the attack, Prony analysis is adopted to acquire the oscillation mode in the system. Then the attack signals are designed to force the oscillation mode of the virtual cyber-attack system interact with the oscillation mode of the physical system, resulting in system instability. Also, the impact of the attack on the system is studied by analyzing the sensitivity of eigenvalues with respect to attack parameters. Finally, a case study is carried out in IEEE 39-bus benchmark system to verify the effectiveness of the proposed attack and study the impact of the attack on CPPS.

Online damping control of power system with LME function of wind farm

The wide-area damping controller (WADC) is suggested by this paper in an online for power systems based on the line modal energy (LME) function of the wind farm. The presence of a wind farm always increases inter-area oscillations, but the proposed method has been made doubly-fed induction generators (DFIG) as a strong point to improve inter-area oscillations. For this purpose, an approach was presented based on energy function, a simple Brunovsky system, and an extended state observer (ESO) to control DFIG. The modal energy function supply traits in a network are evaluated in dissimilar methods, and the system overriding mode is recognized with the Tufts-Kumaresan method (TK). Finally, the wide-area control signals in the DFIG grid side converter (GSC) are selected and it is implemented with the voltage-oriented control (VOC). It is effected in diverse conditions on the standard two-area standard network to authenticate the suggested technique by MATLAB.

Design and Optimal Location of Power System Stabilizer in the Multi-Machine Power Network

This paper proposes a damping torque index (DTI) to determine the optimal installation location of the power system stabilizer (PSS) in the multi-machine power network. The proposed index is based on the classical damping torque analysis (CDTA) method for power system low-frequency electro-mechanical (LFEO) analysis. The selection criteria of the PSS location is the maximum magnitude of DTI under normal operating conditions. The CDTA method is used to design PSS, and the phase compensation technique subsequently adjusts the associated parameters. Furthermore, to analyze the power system’s critical oscillation mode, a wide-area damping controller (WADC) is design for the synchronous generator where optimal location of PSS is install. The reduced-order model-based WADC includes time-varying delay in the wide-area signal. The WADC’s input signals from the phasor measurement unit (PMU) and the location of the PMU are selected using geometric measures of observability and WADC parameters design based on the residue approach. The proposed approach is validated in two separate test systems, and modal analysis is carried out on MATLAB software. The simulated results have been validated on the real-time digital simulator (RTDS) RSCAD 5.012. Results obtained on RTDS show that the proposed approach efficiently damps low-frequency electro-mechanical oscillations.

Improved Data-Driven Model-Free Adaptive Damping Controller Design for Interconnected Power Systems With Stochastic Communication Delays

The original model-based wide-area damping control (WADC) is difficult to obtain good damping performance due to the complex structure of interconnected power systems. In this paper, an improved data-driven model-free adaptive control (ID-MFAC) algorithm is proposed to design WADC for interconnected power systems with stochastic communication delays. First, the multiple-input multiple-output power system can be decoupled as multiple single-input single-output subsystems by considering controller interactions and system disturbances. Second, a step-size vector is designed to adjust the pseudo-partial derivative and make the algorithm more flexible by considering both input and output data adequately. Furthermore, an adaptive delay compensator is designed to compensate stochastic communication delays. Last, simulations are conducted to verify that the ID-MFAC algorithm can efficiently suppress multiple inter-area oscillations modes under various stochastic communication delays.