Inter-area Oscillations In Power Systems Research Articles

CART-based wide-area damping controller for inter-area oscillations in bulk power system consisting of WAMS data

The paper proposes a WADC approach using CART technique to dampen inter-area oscillations (IAOs) in bulk power systems. In this case, PMU data are filtered to estimate inter-area dynamics in which using pade approximation, a pole-zero IAO compensation block is designed. An online random decrement technique is also developed to identify the coherent groups and damping ratios to activate the WADC for oscillation damping. An offline process is provided to identify 200 critical IAO contingencies and tunes WADC gains using PSO for training CARTs via a set of 200 input inter-area signals and assigning output controlling gains pre-trained data and evaluating the CART estimations through online operation. The WADC approach is validated for oscillation damping on a 39-bus system and a realistic 561-generator Iranian grid. Simulations show 98 % accuracy in achieving sufficient damping ratios (>0.6) across various operating conditions.

Coordination of Controllers to Development of Wide-Area Control System for Damping Low-Frequency Oscillations Incorporating Large Renewable and Communication Delay

AbstractThe modern power systems incorporate high penetration of renewable is a large, composite, interconnected network with dynamic behavior. The small disturbances occurring in the system may induce low-frequency oscillations (LFOs) in the system. If the (LFOs) are not suppressed within a stipulated time, it may cause system islanding or even blackouts. Hence, it is essential to investigate the behavior of the system under various levels of disturbances and control action must be taken to damp these oscillations. The established approach to damping the LFOs is by installing power system stabilizers (PSS). PSS uses the local signals from generators to control the oscillations. The dominant source of inter-area oscillations in power systems is due to overloaded weak interconnected lines, converter-interfaced generation, and the action of the high gain exciter present in the system. Consequently, wide area control is needed to control the inter-area oscillations existent in the system. This paper developed a coordinated design of conventional PSS, static compensator, renewable converters, and wide area controller for damping the local and inter-area oscillations in renewable incorporated power systems. The performance of the developed controller is evaluated through the time domain analysis and eigenvalue analysis. A comparison of the introduced controller has been done with other standard conventional methods. The choice of input signals for the wide area controller from the wide-area measurement system is done based on the controllability index. Additionally, the location of the controller must be identified to dampen the inter-area oscillations in the system. In this paper, the controllability index is calculated to find out the highly affected wide area signals for considering it as the feedback signal to a developed controller. The location of the controller is recognized by computing the participation factor. The developed controller has experimented on renewable incorporated large study power systems when time delay and noise are present in wide area signals.

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.

Augmented random search based inter-area oscillation damping using high voltage DC transmission

The high voltage DC (HVDC) Transmissions are under rapid development all over the world. The HVDC transmission not only provides a low-loss electric energy transfer path, but also acts as an alternative tool for damping inter-area oscillations in modern electric power systems. In this paper, we proposed a novel reinforcement learning based HVDC oscillation damping controller using the augmented random search (ARS) algorithm. By leveraging the wide-area information such as voltages, phase angle, machine speeds, the ARS was able to determine the modulation power of HVDC to effectively damp inter-area oscillations. The proposed research overcomes the challenges of setting optimal controller parameters of the HVDC under various system transient events. The proposed ARS-based HVDC power oscillation damping control approach was tested on a simplified Western American large-scale power system model called minniWECC. Extensive studies have demonstrated the superiority of the proposed ARS-based HVDC control approach over conventional power oscillation damping methods.

A Guided Evolutionary Strategy Based-Static Var Compensator Control Approach for Interarea Oscillation Damping

Static Var compensator (SVC) has often been used in the power system industries to regulate the bus voltage and reactive power. With an increasing concern of the power system transient stability, the SVC has also been used to dynamically regulate the power flow for oscillation dampings in recent years. A guided surrogate-gradient-based evolutionary strategy (GSES)-based SVC control approach is proposed in this article to damp power system interarea oscillations. The GSES algorithm is used to train a reinforcement learning agent to learn the best decisions that control the SVC, with an objective of quickly damping interarea oscillations. The GSES algorithm brings many benefits such as easier, more robust, and efficient training with less required hyperparameters. Because the GSES can engage with multiple individual workers during the training process, parallel computation techniques are implemented in this research to accelerate the computational speed. To test the performance of the proposed GSES-based SVC controller, we compared this novel method with a supplementary SVC damping controller on two different test systems. Results indicate that the proposed GSES-based SVC control approach can effectively damp power system interarea oscillations. Especially, in some case studies, the proposed approach successfully saved the test system from a transient-instability-caused breaking down.

Special issue on “Optimal design and operation of energy systems”

Special issue on “Optimal design and operation of energy systems”

Practical Implementation and Operational Experience of Dynamic Mode Decomposition in Wide-area Monitoring Systems of Italian Power System

This study presents the assumptions and strategies for the practical implementation of the dynamic mode decomposition approach in the wide-area monitoring system of the Italian transmission system operator, Terna. The procedure setup aims to detect poorly damped interarea oscillations of power systems. Dynamic mode decomposition is a data-driven technique that has gained increasing attention in different fields; the proposed implementation can both characterize the oscillatory modes and identify the most influenced areas. This study presents the results of its practical implementation and operational experience in power system monitoring. It focuses on the main characteristics and solutions identified to reliably monitor the interarea electromechanical modes of the interconnected European power system. Moreover, conditions to issue an appropriate alarm in case of critical operating conditions are described. The effectiveness of the proposed approach is validated by its application in three case studies: a critical oscillatory event and a short-circuit event that occurred in the Italian power system in the previous years, and a 15-min time interval of normal grid operation recorded in March 2021.

Online Transfer Function Estimation and Control Design Using Ambient Synchrophasor Measurements

This paper proposes an adaptive control design framework for damping inter-area oscillations in power systems. The design is entirely based on ambient synchrophasor measurements. The proposed framework consists of three components, namely, input-output transfer function estimation, channel selection, and feedback control implementation. For the first part, we propose a simple yet effective novel estimation algorithm in the frequency domain to identify low-order transfer functions in pre-specified frequency ranges between the measured input and output data using ambient synchrophasor measurements. In the second part, based on the identified transfer functions, the joint controllability-observability (JCO) of all identified channels is estimated and most suitable control candidates for damping the target inter-area mode are selected. Finally, an appropriate lead-lag controller is designed using a classical frequency-domain method to improve the damping of a dominant oscillatory inter-area mode. Since ambient data is used in the analysis, the selected channel as well as the designed controller parameters can be updated online whenever the system operating point changes resulting in an efficient adaptive controller. The effectiveness of the proposed framework is illustrated by implementing it on the two-area Kundur test system and the IEEE 39-bus test system.

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.

Optimal hybrid control of interarea oscillation in power system using energy storage systems

AbstractUnmanaged renewables integration into the power system will raise the possibility of small‐signal instability due to higher load deviations in the transmission lines. In power grids with a higher penetration level of the renewables, the load deviation can cause interarea oscillation in the grid. Meanwhile, large‐scale battery energy storage systems are promising solutions to enhance power system stability by smoothening the load profile and their fast response. To damp the interarea oscillations without compromising the voltage stability, we need to consider the battery's dynamic model in axis. The battery's dynamic model in axis allows us to integrate the battery into the power system and simulate both the battery's active and reactive power injection/absorption. In this paper, we model the battery energy storage on axis. Then, the battery model is augmented into the two‐area four‐machine power system. An optimum hybrid controller using linear quadratic regulator techniques is designed to damp generators' frequency deviations. The results show that the interarea oscillations are damped without losing the voltage stability of the system.

Adaptive WADC scheme for damping inter‐area oscillation based on Jaya optimization algorithm in the presence of variable time latencies from WAMS data

The continual increase in the power network topological structure and long distances between load-generation sources lead to modern powers systems are operated near theirs stability margins. For this issue, reliable and secure operations of electric devices through inter-area oscillations remain an essential issue in the system dynamic stability. In the case of improper actions of controlling devices, the severe inter-area interactions may lead to wide-area instabilities and large blackouts. Using wide-area measurement system (WAMS), remote signals are transferred through communications links with different inherent time latencies. In the case of large time delays, the main controllers cannot work appropriately which leads to improper performance of damping controllers through severe inter-area fault event scenarios. For this issue, this paper presents an adaptive wide-area damping controller (AWADC) for damping inter-area oscillations in large power systems equipped with WAMS technology consisting of various time latencies. In this case, based on the IEEE C37.118.1 protocol, the generator buses are equipped with phasor measurement unit devices. Also, owing to the different communication links, the measured global signals (GSs) are involved within different time latencies. In this case, at each time window, considering time delay compensator (TDC) technology provided through Simevents discrete event tool, the overall time delay is evaluated and compensated. For identifying the best controlling GSs, considering two observability and controllability concepts, the system dynamic signals are evaluated which the best input decisioning signals and corresponding output controlling signals are provided. The proposed AWADC scheme consists of different compensating blocks which are adjusted through simple and well-known Jaya optimization algorithm (JOA) through online evaluations. The structure of the proposed AWADC controlling scheme is carried out on a modified 39-bus New England test system consisting of large synchronous generators whose damping performances are evaluated through severe fault events with the potential of unstable inter-area oscillations. Simulation results indicate the effectiveness of developed TDC and JOA techniques to provide proper controlling signals through the AWADC controller in the presence of different time latencies.

Dynamic clustering-based model reduction scheme for damping control of large power systems using series compensators from wide area signals

This paper presents a new scheme of thyristor controlled series compensators (TCSC)-based damping controller for damping inter-area oscillations in bulk power systems based on a wide area measurement system (WAMS). In this regard, the proposed scheme provides an adaptive three-phase step through real-time working mode. In the first step, by proposing dynamic clustering-based technique, wide area signals evaluate the inter-area oscillations of the system which in a real-time procedure identify the corresponding oscillating areas. In the case of reducing the order of power systems through a set of aggregated coherent areas, the proposed scheme implements through the second step which utilizes as a damping controller for damping the inter-area oscillations. In this step, the wide area electromechanical signals use as input data through the proposed TCSC-based damping controller. The corresponding controlling signals consist of inter-area rotor angle (ΔδCOI) and inter-area speed deviation (ΔωCOI) evaluated through center of inertia (COI) frame. In the third step, at each time window (ΔT) through real-time working mode, the proposed scheme examines through a set of fault occurrences which based on online evaluations of the system dynamic responses, the controller parameters adjust adaptively. The proposed controller is an online and non-model-based scheme which properly reduces the system order through a set of coherent areas to provide proper damping performances of inter-area oscillations. The effectiveness of the proposed scheme evaluates through the Iran National Power Grid with the potential of two oscillating areas with proper damping performances for damping the unstable inter-area oscillations.

Scalable design methods for online data‐driven wide‐area control of power systems

A novel online system-identification-based control design for damping inter-area oscillations in power systems using supplementary wide-area excitation control is presented. The identification is based on a partly reduced-order and a partly full-order model of the grid. Assuming the grid to be divided into coherent areas with phasor measurement units located across the grid, the coherent states of the generators are averaged while the non-coherent states, such as the internal states of each power system stabilizer, are not. A hybrid state vector consisting of these averaged and non-averaged states is computed, and used for identifying a hybrid linear time-invariant state-space model. A linear quadratic regulator based on this hybrid model is, thereafter, designed. The reduced-order part of the model is found to save significant amount of online time for both learning and control, while the full-order part serves to enhance closed-loop stability. N4SID with randomized singular value decomposition (rSVD) is used for making the identification loop fast. The reduced-dimensional controller is finally implemented using a broadcast control strategy. The design is extended to non-linear models of power systems using Carleman bilinearization. Results for linear and bilinear control designs are validated using the IEEE 68-bus power system model.

Identification of Low-Frequency Oscillation Modes Using PMU Based Data-Driven Dynamic Mode Decomposition Algorithm

Power system inter-area oscillations curtail the power transferring capabilities of the transmission lines in a large interconnected power system. Accurate identification of dominant modes and associated contributing generators is important to avoid power system failures by taking appropriate remedial measures. This paper proposes a multi-channel Improved Dynamic Mode Decomposition (IDMD) algorithm-based modal analysis technique using Synchrophasors measurement. First, a reduced-order dynamic power system model is estimated and using this model dominant oscillation modes, corresponding modes shapes, damping ratio, coherent group of generators, participation factors are determined. To improve the accuracy data stacking technique is used to capture detailed information of the system. An optimal hard threshold technique is utilized to select the most optimal model order to avoid uncertainties due to the presence of high level of measurement noise. The study results show that the proposed algorithm gives an accurate and robust solution even in systems having high level of noise in the measurement data. The performance of the proposed technique is tested on simulated data from two-area four-machine system and wNAPS 41-bus 16-generator system with PMU measurements corrupted with different levels of measurement noise. To further strengthen the viewpoint, the proposed method is validated on real-time PMU measurement from ISO New England data to validate the accuracy of the proposed work.

A Frequency-shaped Controller for Damping Inter-area Oscillations in Power Systems

This paper discusses how to design an inter-area oscillations damping controller using a frequency-shaped optimal output feedback control approach. This control approach was chosen because inter-area oscillations occur at a particular frequency range, from 0.2 to 1 Hz, which is the interval the control action must be prioritized. This paper shows that using only the filter for the system states can sufficiently damp the system modes. In addition, the paper shows that the filter for the input can be adjusted to provide primary frequency regulation to the system with no effect to the desired damping control action. Time domain simulations of a power system with a set of controllable power injection devices are presented to show the effectiveness of the designed controller.

Optimal siting, sizing, and parameter tuning of STATCOM and SSSC usingMPSO and remote coordination of the FACTS for oscillation damping of powersystems

In electromechanical oscillation damping within power system, power system stabilizers (PSSs) are often deployed. However, a PSS is less effective in damping interarea oscillation and is limited by changes in network configuration due to weak tie-lines and load variations. Consequently, this paper presents a wide-area coordination approach that damps interarea oscillations using FACTS devices and phasor measurement units. We selected a static synchronous compensator (STATCOM) and static series synchronous compensator (SSSC) for realistic power system interarea oscillation damping. The performance of the coordinated FACTS installed in a power system depends on their suitable locations, sizes, tuned parameters, and remote input signal selection. Hence, we formulated a multiobjective problem to provide the STATCOM and SSSC's optimal solutions using multiobjective particle swarm optimization. In addition, we employed a participation factor to select suitable generator speed deviations as the wide area stabilizing signal. The proposed approach was tested on different configurations of the Kundur $2$-area $4$-machine test system within MATLAB and Psat environments. The outcome of the nonlinear simulation proved that the multimachine power system stability was enhanced.

Artificial Neural Network Control of Battery Energy Storage System to Damp-Out Inter-Area Oscillations in Power Systems

This paper proposed an ANN (Artificial Neural Network) controller to damp out inter-area oscillation of a power system using BESS (Battery Energy Storage System). The conventional lead-lag controller-based PSSs (Power System Stabilizer) have been designed using linear models usually linearized at heavy load conditions. This paper proposes a non-linear ANN based BESS controller as the ANN can emulate nonlinear dynamics. To prove the performance of this nonlinear PSS, two linear PSS are introduced at first which are linearized at the heavy load and light load conditions, respectively. It is then verified that each controller can damp out inter-area oscillations at its own condition but not satisfactorily at the other condition. Finally, an ANN controller, that learned the dynamics of these two controllers, is proposed. Case studies are performed using PSCAD/EMTDC and MATLAB. As a result, the proposed ANN PSS shows a promising robust nonlinear performance.

Fast Frequency Response From Smart Induction Motor Variable Speed Drives

Using their fast power reduction capabilities, the induction motor variable speed drives can successfully participate in the power system primary frequency control. A new control strategy for fast frequency support from the diode front-end induction motor variable speed drive is presented in this paper. By this, practical restrictions are considered. In this context, an existing conventional scheme presented in literature is firstly modified by deploying an estimated motor's power losses for a more exactly control design. Next, a novel control scheme is proposed. It attains the fastest frequency support from the drive and simultaneously restricts its minimum power consumption to a given positive value to prevent regeneration mode during the frequency support process. The frequency of applied voltage to the motor is adjusted through a proportional-integrator compensator with deviation of the drive's consumption power from its reference power as input. The reference power is synthesized by permanent and temporary components, which are determined based on deviation and time derivative of the power system's frequency, respectively. The effectiveness of the proposed smart drive for the primary frequency control is investigated using the New England 39 bus and a more realistic Great Britain 36 zone test networks. It improves system frequency response in terms of the rate of change of frequency and the frequency nadir. Furthermore, the new control scheme can contribute to quickly damping inter-area oscillations in multi-machine power systems.

Fixed low-order synchronized and non-synchronized wide-area damping controllers for inter-area oscillation in power system

Low-frequency poorly damped oscillation is a major threat to bulk power transmission through a weak tie-line in the interconnected power system. A wide-area damping controller (WADC) can provide an adequate damping to these low-frequency modes to achieve secure operation of the large power system. In this work, a hybrid optimization algorithm based fixed low-order WADC is designed using wide-area feedback signal to improve the damping of poorly damped inter-area mode. Although wide-area signal can be used to improve the damping of the inter-area oscillations, the introduction of time delay in the wide-area signal can degrade the controller performance and even may lead to instability. Here, two types of delayed (synchronized and non-synchronized) feedback configurations are considered in case of wide-area signal transmission, and the controller is designed by optimizing the design functions such as H∞ norm, spectral abscissa and complex stability radius. The designed controllers enhanced the damping performance of the inter-area oscillations. A higher order mixed sensitivity based H∞ controller is also designed with additional pole placement constraints for comparison with the design functions. From the simulation studies of the Kundur’s two-area system and IEEE-39 bus test system, it is demonstrated that the fixed low-order controllers are effective to improve the damping of the inter-area oscillations and compensating the time delay effect in the wide-area signal.

Wide-Area Robust Sliding Mode Controller for Power Systems With False Data Injection Attacks

In this paper, the issue of interarea oscillations in wide-area power systems with false data injection (FDI) attacks is studied. A wide-area robust sliding mode controller (WARSMC) is proposed to defense the hacker attacks and damp out the interarea oscillations. First, an extended observer is designed to estimate the states and defense actuator attacks simultaneously. Then, a WARSMC based on the estimated states is presented. In which a new sliding function is constructed, meanwhile, the new reaching law is designed. Furthermore, the system dynamics under designed control law is analyzed and the convergence of the proposed algorithm is proved. Finally, the case studies are based on the two-area four-machine and the 16-machine 68-bus power system. Simulation results verify the effectiveness of the designed method for defensing the FDI attacks and damping out the interarea oscillations.