Wide-area Damping Controller Research Articles

Design of a delay dependent wide area damping controller using Cyber–Physical Power System architecture

With the wide application of information and communication technology in power grids, the integration and collaboration of information networks and physical grid have become an essential feature of the smart grid, constituting a typical power information physical system. However, information network has communication time delay problem, which tends to deteriorate the system controller performance or even counter-tune, leading to system instability. To effectively reduce low-frequency oscillation of the wide-area interconnected grid and overcome the negative impact of the communication network’s delay problem, a delay dependent Wide Area Damping Controller(WADC) is designed using cyber–physical power system architecture. First, we establish a power information physical system simulation platform based on Object linking and embedding for Process Control (OPC) technology, implementing the joint operation of the power system simulation tool DIgSILENT and the information system simulation tool MATLAB. The platform can effectively respond to the system’s information system and physical system interaction effects during simulation. Then, to compensate for communication delays in the power information physical system, this paper proposes a new WADC strategy that uses a Model Predictive Controller (MPC) to generate control commands and an adaptive time delay compensator to compensate for the random communication delays generated in the communication. Finally, a case study with various uncertainties and through the interference test of a four-machine system and 39 bus system, the proposed control strategy is proposed.

Large-Scale Solar PV Converter based Robust Wide-Area Damping Controller for Critical Low Frequency Oscillations in Power Systems

Integration of large-scale renewable energy sources in legacy power system has negative impact on inertia and low-frequency oscillations (LFOs). Critical LFO modes are the primary concern in system stability as they limit the power transfer capability in inter-region tie-lines. Therefore, to provide adequate damping to critical LFO modes, a robust wide-area damping controller (WADC) design is required. In this paper, time delayed feedback control (TDFC) based WADC design is carried out with large-scale solar photovoltaic (SPV). In the design process, geometric technique is used to determine the appropriate wide-area signals. Time delays and noises in feedback signals as well as different operating scenarios have severe implications on the damping performance of WADC. Hence, considering these uncertainties, the proposed WADC parameters are tuned by modified particle swarm optimization (PSO) algorithm. The performance of proposed WADC is demonstrated on SPV-integrated IEEE 4-machine 11-bus and 16-machine 68-bus systems. Critical modes of the system are damped by more than 10 % damping ratio in both cases. Furthermore, nonlinear dynamic simulations demonstrate that the proposed WADC provides robust performance over wide operating scenarios. Finally, practical efficacy of the proposed method is established by experimental validation through real-time simulation using OPAL-RT.

Laboratory Implementation of a Wide-area Damping Controller using a Dynamic Hardware Emulator

The ongoing decarbonisation of the electric power system brings new challenges in terms of system dynamics and stability, as the substitution of generation units with rotating masses towards generation units based on power electronics entails a substantial loss of inertia. To meet the new challenges and maintain the reliability of the electrical grid, innovative solutions are required. Therefore, this paper presents a two-step approach to test and validate controller structures for damping inter-area oscillations. First, the controller was developed and tested in a control hardware in the loop environment. Then, the controller was transferred to a dynamic hardware emulator (scaled version of the Kundur's two area transmission network in the laboratory consisting of physical hardware) for final performance validation. It is shown that with a conventional power system stabilizer (PSS) and a proportional wide-area damping controller (WADC), the damping of inter-area oscillations is improved in an emulated power system. In addition, with the setup created, different types of controllers and other challenges related to wide-area damping control can be investigated in the future.

Enhancement of inter‐area oscillation damping by wide‐area controlled hydropower plants

This paper examines how the combined use of hydro governors and a wide-area damping controller (WADC) can improve the damping of inter-area oscillations in power systems. Such oscillations can endanger the stability of power grids, thus damping them is a high priority for transmission system operators (TSO). To ensure that low-frequency oscillations decay as fast as possible, a modal linear quadratic Gaussian (LQG) is proposed as a wide-area controller approach. Using the 10-machine New England Test System, the combined application of the WADC in hydropower plants via generator excitation as well as via the hydro governor is examined for their effectiveness in terms of damping capability. In order to minimize the number of essential PMUs in power systems for the model-based WADC, the residue-based input/output signal selection method is applied. To increase the robustness against large disturbance faults, the generator voltage as additional signal is utilized for the WADC. For controller performance and robustness, the verification has been done under various operating points, tie-line failures as well as different PMU delays. The successful damping of the inter-area oscillation by means of wide-area controlled hydropower plants has been also demonstrated through a nonlinear time domain simulation.

A UPFC‐based robust damping controller for optimal use of renewable energy sources in modern renewable integrated power systems

This paper proposes coordinated design of wide-area damping controller (WADC) in the presence of renewable energy resources in a large-scale power system. To tackle with constant and time-varying delays in wide-area system, a robust criterion based on H∞ has been used for the coordinated WADC design. By using an auxiliary function in Lyapunov function, conservatism of linear inequality matrix (LMI) is reduced, such that larger delay margin and larger feasibility region is obtained in the presence of delays. The wind farms here are composed of doubly-fed induction generator (DFIG) and squirrel-cage induction generator (SCIG), which are connected to common bus of photovoltaic (PV) system by using unified power flow controller (UPFC). Then, the renewable energy units are integrated with 10 and 16-machine power systems. Afterwards, by identifying oscillating modes, the coordinated design of WADC is carried out for rotor-side-converter (RSC) in DFIG, DC/AC converter in the PV units, shunt converter (SHC) in UPFC, and power system stabilizer (PSS). Different scenarios of power system operating conditions are considered to evaluate performance of the proposed approach. The simulations in power system analysis toolbox (PSAT) and programming in MATLAB demonstrate effectiveness of the conducted method.

Design of a Reduced-Order WADC for Wind Turbine System-Integrated Power System

The impact of wind turbine system (WTS) on power system stability is elaborately addressed in the literature. However, low-frequency oscillations, especially inter-area oscillations (IAOs) can be adversely affected due to their intermittent nature. This article proposes a wide-area damping controller (WADC) for WTS-integrated power system to damp IAOs effectively. The feedback signals (linear combination of the system states) are directly measurable from phasor measurement units. Therefore a reduced-order estimator is proposed instead of a full-order estimator to design the WADC. Furthermore, to select appropriate feedback signals for WADC design, combined geometric measure and modal decomposition techniques are utilized. The overall procedure to design the reduced-order WADC includes feedback signal selection, state feedback formulation using modal transformation approach, and reduced-order estimator design using loop transfer recovery procedure. Moreover, the WADC parameters are selected considering operating point uncertainties and variable time delays in feedback signals. Performance of the proposed WADC is validated on WTS-integrated 16-machine, 68-bus system. The simulation results show that the proposed WADC gives robust performance over broad operating scenarios.

Quantifying Resilience of Wide-Area Damping Control Against Cyber Attack Based on Switching System Theory

Since the cyber attack on the communication network will deteriorate the performance of wide-area damping controllers (WADCs) or even cause instability, many resilient WADCs are developed to mitigate the adverse influence of cyber attacks recently. However, there is a lack of quantitative indexes to guide the controller design in order to achieve the trade-off between attack resilience and damping performance. To address this problem, an index is proposed to quantify the strongest attack that the power system with a given WADC can tolerate, which is called as resilience margin. Firstly, the power system with a WADC subjected to cyber attack is modeled as a switching system consisting of stable and unstable subsystems. Then, based on switching system theory, the definition of resilience margin is presented. To calculate the resilience margin, the Lyapunov stability analysis is implemented on the switching power system to derive a practical calculation algorithm, which combines the bisection method and the linear matrix inequalities (LMIs) technology. The case study on the 16-machine 68-bus system with a voltage source converter based high voltage direct current system is performed. Simulation results demonstrate the effectiveness of the calculation algorithm and the significance of the resilience margin in the design of WADC.

Time Delay of Wide Area Damping Control in Urban Power Grid: Model-Based Analysis and Data-Driven Compensation

Due to the rapid development of economies, large urban cities consume an increasing amount of energy and have a higher requirement for power quality. Voltage source converter based high voltage direct current (VSC-HVDC) is a promising device to transmit clean power from remote regions to urban power systems, while also providing wide area damping control (WADC) for frequency stabilization. However, the time-delay naturally existing in the VSC-HVDC system may degrade the performance of WADC and even result in instability. To address this issue, this paper develops a time-delay correction control strategy for VSC-HVDC damping control in urban power grids. First, a small signal model of WADC is built to analyze the negative impacts of time delay. Then, a data-driven approach is proposed to compensate for the inherent time delay in VSC-HVDC damping control. The extensive training data will be generated under various disturbances. After offline training, the long short-term memory network (LSTM) can be implemented online to predict the actual frequency deviation based on real-time measurements. Finally, the proposed method is validated through MATLAB-Simulink in a two-area four-machine system. The results indicate that the data-driven compensation has a strong generalization ability for random delay time constants and can improve the performance of WADC significantly.

Delay dependent wide area damping controller with actuator saturation and communication failure for wind integrated power system

Integration of wind farm with power system introduces nonlinearity and complexity of the power system, which deteriorates the performance of a wide area damping controller (WADC). A WADC is designed in this paper for wind energy conversion system (WECS) integrated power system taking the communication latency and communication failure of the wide area measurement system (WAMS) into consideration. Apart from communication delay and communication failure, the effect of saturation is also considered in this paper. A state feedback stabilizing controller is designed using linear matrix inequality (LMI) platform. The control signal chosen here is combination of local and global signal to ensure stability during communication failure. The inter-area oscillation is reduced by controlling the reactive power of the wind farm. The effectiveness of the controller developed is verified using a WECS integrated modified 11-bus test system and modified IEEE 39-bus test system. The simulation results show that the designed controller guarantees stability and also can eliminate inter-area oscillations effectively of a WECS integrated power system.

Incomplete Information Stochastic Game Theoretic Vulnerability Management for Wide-Area Damping Control Against Cyber Attacks

While securing wide-area damping controllers (WADCs) against cyber attacks becomes critical, most existing efforts deal with model-based attacks. A smart attacker may not follow the prescribed models and can intelligently change the attack actions. To tackle this challenge, this work proposes a stochastic game theoretic framework that can model the dynamic interaction between the attacker (a jammer) and the defender (intrusion detector in the WADC) with the player’s type uncertainty to optimally manage the vulnerability of the power system. Uniquely, the always opponent assumption of the other player made in most of the existing works is removed as this assumption may lead to serious resource waste due to the high over-defense rate. In this incomplete information stochastic game, the attacker intelligently jams the communication links between phasor measurement units (PMUs) and WADCs, while the intrusion detection of the WADCs is considered as the defense action. The vulnerability level of the power system resulted from the attack and defense actions in the cyber-layer is indexed by the trace of the observability Gramian. Therefore, the proposed stochastic game framework provides a cyber-physical view to make the optimal cyber-layer intrusion detection system (IDS) triggering strategy for the WADC. As the types of the other player are unknown to the defender, a Bayesian based posterior type belief update method is proposed for the defender to update the type belief about the opponent by the boundary probability based on the Bayesian Nash Equilibrium. The proposed cyber-layer IDS triggering strategy is tested and compared with other game approaches on the IEEE 39-bus 10-generator system. Simulation results show that the proposed approach can achieve the same defense performance compared to the complete information stochastic game while reducing the over-defense rate from 40% to 16%.

A Modal Transformation Approach to Design Reduced Order Functional Observer-Based WADC for Low-Frequency Oscillations

Low-frequency oscillations (LFOs) are one of the major concerns in modern power system; hence, these should be appropriately treated in order to achieve reliable operation. In this regard, we propose a novel wide-area damping controller (WADC) to dampen LFO modes effectively. The proposed WADC utilized thyristor controlled series compensator (TCSC) based flexible ac transmission system (FACTS) device through which supplementary input is provided. The selection of modal feedback signals for WADC design is carried out using coordinated modal transformation and linear quadratic regulator (LQR) approach. However, these signals are not accessible directly through the phasor measurement devices (PMDs). Hence, this paper utilizes a reduced-order functional observer to estimate the feedback signals using PMD data. The estimated feedback signals are further modulated by simple gains to improve the damping of critical LFO modes. The proposed methodology is validated on benchmark 4-machine 11-bus system and a more practical 25-machine, 105-bus system representing the complex Eastern Regional Grid (ERG) of India. The results obtained on these nonlinear systems show a significant improvement in damping of the critical LFOs leaving the other modes almost unaffected.

Resilient Adaptive Wide-Area Damping Control to Mitigate False Data Injection Attacks

The wide-area damping controller (WADC) using the remote signals obtained from wide-area measurement system (WAMS) as input is an effective measure to suppress interarea oscillations. Once the input signal of WADC is threatened by false data injection attacks (FDIAs), its performance will be decreased dramatically. To address this problem, this article proposes a resilient adaptive wide-area damping control (RAWADC) framework combined with linear state estimator (LSE) and goal representation heuristic dynamic programming (GrHDP). The LSE is proposed and adopted as a preprocessor to detect and correct the attacked data. By detecting and correcting FDIA, the integrity of the WAMS measurement signal is guaranteed. The GrHDP algorithm is employed to design the WADC, which not only does not require a detailed mathematical model of the system but can also adapt to variations of the operating conditions. Simulation results of the 16-machine 68-bus system with voltage source converter based HVdc indicate that the RAWADC can suppress interarea oscillation effectively under a wide range of operating conditions, different FDIA types and measurement noise.

Output-feedback photovoltaic WADC by H∞ criterion using auxiliary function

The wide-area damping controller (WADC) is vital in suppressing wide-area oscillations. However, the power system is now developing very fast, traditional output-feedback linear matrix inequality (LMI) criteria adopted in this field may not be very applicable. This paper proposes an output-feedback H∞ robust criterion to design a WADC installed in the photovoltaic plant considering the wide-area signal delay. We use the auxiliary function technique, and adopt Lyapunov functions containing triple summation, augmented variables and cross terms to deduce a stability analysis criterion followed by the corresponding controller design criterion. The low conservatism and control performance of the proposed criteria are verified in a 68-bus 16-machine test system. In addition, as system parameters often change, the control performance of integrating the proposed controller design criterion into a gain scheduling algorithm to handle the system parameter variance is validated.

A model-free sparse wide-area damping controller for inter-area oscillations

As the successor of local control, wide-area damping control (WADC) is considered to be an effective tool for damping inter-area oscillations. The state-of-the-art WADC approaches are either model-based or centralized, so they are subject to model inaccuracy, bad data, high communication costs, and other nontrivial design challenges. On the other hand, current data-driven WADC practices are affected by the selection of input/output measurements, need to be pre-tuned and trained offline, or lack clear physical interpretation of the power grid small-signal dynamics. In this paper, we propose a novel online purely data-driven WADC method using phasor measurement unit (PMU) data, which requires no power system model information and can damp multiple inter-area modes simultaneously using minimal control effort. To directly shape the closed-loop characteristics of poorly-damped inter-area modes and account for physical constraints on communication network, we develop a modal linear quadratic regulator (MLQR)-based sparsity-promoting optimal state feedback controller. The developed WADC strategy does not require offline training, is adaptive to the applied PMU dataset and can be mapped to the actual grid physics. Dynamic simulations on the widely studied IEEE 68-bus benchmark system verify the effectiveness of the proposed approach in spite of measurement noise, PMU losses, and communication network restrictions. Moreover, it is shown that the proposed controller can adapt to different operating conditions due to its data-driven nature. Finally, our data-driven sparse WADC has comparable performance to conventional model-based and centralized data-driven WADC, while overcoming their limitations.

Online DMDc Based Model Identification Approach for Transient Stability Enhancement Using Wide Area Measurements

This letter proposes an online control strategy to enhance the overall damping of low-frequency power system oscillations of large inter-connected electrical networks. To achieve this objective, the proposed approach employs wide area measured signals to estimate an accurate online model of power system dynamics using the dynamic mode decomposition with control (DMDc) method. The DMDc technique applies singular value decomposition (SVD) to the collected data matrices such that an accurate low-order approximation of system dynamics is obtained. The estimated model is thereafter utilized in designing the wide area damping controller (WADC) using discrete linear quadratic regulator (DLQR). Furthermore, kalman filtering is deployed to update the states of the designed controller and to remove the noise that is contained in the measured signals. The effectiveness of the proposed method is tested on the 10 machines, 39-bus New England test system.

Mitigating inter-area oscillation of an interconnected power system considering time-varying delay and actuator saturation

A wide area damping controller (WADC) is designed in this paper to mitigate the frequency deviation of interconnected power system. The effect of time delay during wide area measurement system (WAMS) and saturation of the actuator is also considered in this work while designing the WADC. The effect of communication delay along with the saturation of a actuator can make the interconnected power system unstable. This paper focuses on finding a stabilization criterion of the power system connected with a WADC. The WADC is designed taking the effect of time-varying delay in the WAMS and saturation of the actuator into consideration. The saturation of the actuator is modelled with the help of dead zone type non-linearity. In this paper, a Lyapunov–Krasovskii functional is used to design a state feedback control law based on linear matrix inequality (LMI) taking time-varying delay and the actuator saturation into consideration. A thyristor controlled series capacitor (TCSC) is used as an actuator. A supplementary damping controller (SDC) is used as the WADC in this paper to provide sufficient damping. Simulation study on four machine 11 bus power system and New England 39 bus power system is performed to understand the performance of the designed controller. The results are also verified in real-time using OPAL-RT.

Coordinated design of delay‐dependent wide‐area damping controllers considering multiple time delays

This paper investigates coordinated design of multiple wide-area damping controllers (WADCs) for damping multiple inter-area oscillations considering communication delays in multiple control loop. Two approaches have been investigated: the sequential approach which uses the stability criteria for single delay and design the WADC independently, and the coordinated approach which employs a less conservative and fast Lyapunov stability criterion for linear system with multiple delays to calculate delay margins simultaneously and coordinately design the multiple WADCs. The sequential approach cannot reveal the interaction among several WADCs loops with multiple delays and may lead to inaccurate delay margins, while the coordinated approach takes into account interactions of delays between different WADC control loops and can result in accurate delay stable region and relationship between delay margins and the WADC gains. Gains of WADCs are determined based on a trade-off between damping performance and delay margin. Case studies are based on the modified IEEE 10-machine 39-bus power system equipped with two FACTS devices and two WADCs. The feasibility and effectiveness of the proposed approach is verified by simulation studies.

WAMS-Based Model-Free Wide-Area Damping Control by Voltage Source Converters

In this paper, a novel model-free wide-area damping control (WADC) method is proposed, which can achieve full decoupling of modes and damp multiple critical inter-area oscillations simultaneously using grid-connected voltage source converters (VSCs). The proposed method is purely measurement based and requires no knowledge of the network topology and the dynamic model parameters. Hence, the designed controller using VSCs can update the control signals online as the system operating condition varies. Numerical studies in the modified IEEE 68-bus system with grid-connected VSCs show that the proposed method can estimate the system dynamic model accurately and can damp inter-area oscillations effectively under different working conditions and network topologies.

A Hybrid Particle Swarm Optimization Algorithm for the Wide-Area Damping Control Design

The presence of low-frequency and low-dampened oscillation modes can compromise the operating stability of power systems. Recent research has shown that the use of phasor measurement units data to compose a wide-area damping controller (WADC) has been shown to be effective in mitigating such oscillation modes but the possibility of loss of communication channels due to cyber-attacks or failures can compromise the proper operation of this controller. Besides, traditional control design methods present difficulties for the WADC control design. This article proposes a method based on hybrid particle swarm optimization in order to design a WADC that ensures robustness to power system-operating uncertainties, time delays variations on the WADC channels, and the permanent failure of the WADC communication channels. Modal analysis and nonlinear time-domain simulations were conducted in the IEEE 68-bus power system considering a set of scenarios.

An Efficient Eigenvalue Tracking Method for Time-Delayed Power Systems Based on Continuation of Invariant Subspaces

Time delays are inevitable in the power systems with wide-area control signals, which may compromise the control pe-rformance and thus jeopardize the stability of the power systems. To analyze the impacts of system parameters on critical oscillation modes of a time-delayed power system (TDPS), a new method for eigenvalue trajectory tracking of TDPS is proposed in this paper based on the continuation theory of invariant subspaces. When small changes are imposed on system parameters, such as parameters of wide-area damping controllers (WADCs) and time delays, the invariant subspaces are continuously predicted and corrected, followed by the eigenvalues and eigenvectors. In the process, the predictor and corrector are computed by solving linear equations sparsely and in blocks, which is highly scalable and computationally efficient for large-scale power system applications. The 16-generator 68-bus test system and two real-world power grids in China are used to test and demonstrate the proposed method. The results show that the proposed method can accurately and efficiently track eigenvalue trajectories for TDPS, especially for large-scale power grids. In addition, the sensitivities of eigenvalues and eigenvectors with respect to WADCs' parameters and time delays are obtained as by-products of the approach.