Inter-area Power Oscillations Research Articles

Supplementary Controller on Multi-Terminal Direct Current Link for the Damping of Interarea Power Oscillation of Kundur Two-Area Four-Machine System for Sustainable Grid Network

Supplementary Controller on Multi-Terminal Direct Current Link for the Damping of Interarea Power Oscillation of Kundur Two-Area Four-Machine System for Sustainable Grid Network

Adaptive inter-area power oscillation damping from offshore wind farm and MMC-HVDC using deep reinforcement learning

The coordination of the offshore wind farm (OWF) and high-voltage direct current (HVDC) links to provide ancillary power oscillation damping (POD) services may become a mandatory requirement from the transmission system operators in the near future. However, the performances of the POD controllers (PODCs) are vulnerable to the power system uncertainties and random communication delays of the wide-area signals. To address these issues, this paper proposes the design of the coordinated PODCs by using the deep reinforcement learning (DRL) method. The DRL-based PODCs employ one of the state-of-the-art DRL algorithms, proximal policy optimization, which can learn to adapt to the system uncertainties and time-varying communication delays by interacting with the power system continuously. A detailed simulation model of an OWF connected to the IEEE-39 bus AC grid via the modular multilevel converter based HVDC link has been built as a simulation platform, and the efficacy of the proposed DRL-based PODCs has been validated across a broad spectrum of operating conditions, disturbances, and communication latency.

Analysis of Secondary Controller on MTDC Link with Solar PV Integration for Inter-Area Power Oscillation Damping

Integration of renewable energy sources is important in limiting the continuous environmental degradation and emissions caused by energy generation from fossil fuels and thus becoming a better alternative for a large-scale power mix. However, an adequate analysis of the interaction with the alternating current (AC) network during network disturbance, especially during inter-area power (IAP) oscillations is needed. Insufficient damping of oscillations can significantly impact the reliability and effective operation of a whole power system. Therefore, this paper focuses on the stability of the modified Kundur two-area four-machine (MKTAFM) system. A robust secondary controller is proposed and implemented on a line commutated converter (LCC)-based multi-terminal high voltage direct current (MTDC) system. The solution consists of a local generator controller and the LCC MTDC (LMTDC) system, voltage-dependent current order limiter, and extinction angle controller. The proposed robust controller is designed for the LMTDC systems to further dampen the inter-area power oscillations. Three operational scenarios were implemented in this study, which are the local generator controller and double circuits AC line, local generator controller with LMTDC controllers, and local generator controller with LMTDC controllers and secondary controller. The simulation result carried out on PSCAD/EMTDC recorded better damping of the inter-area power oscillation with LMTDC. A considerable improvement of 100% damping of the IAP oscillations was observed when a secondary controller was implemented on the LMTDC.

A Novel Hybrid Chaotic Jaya and Sequential Quadratic Programming Method for Robust Design of Power System Stabilizers and Static VAR Compensator

This paper proposes a novel hybrid algorithm combining chaotic Jaya (CJaya) and sequential quadratic programming (SQP), namely CJaya-SQP, for solving the coordinated design problem of static var compensator (SVC) and power system stabilizers (PSSs). The CJaya serves as a global optimizer and the SQP as a local optimizer for fine-tuning the solution. In the proposed algorithm, chaotic maps are used to generate the initial solutions and control the search process. In order to prove the performance of the CJaya-SQP, a set of benchmark optimization problems is used where the results are compared with those of the basic Jaya and other recognized algorithms. The proposed optimization method is then applied for the optimal tuning of PSSs and SVC controllers in such a way that damping ratios and damping factors of the electromechanical modes are optimally improved. To illustrate the robustness of the CJaya-SQP-based coordinated PSSs and SVC controllers, the four-machine, two-area system is used. Eigenvalue analysis and nonlinear time-domain simulation vividly show that the CJaya-SQP-based coordinated controllers improve greatly the system’s dynamic stability with a robust damping of local and inter-area power oscillations.

An intelligent two‐level control of Ultrabattery for improved automatic generation control of a multi‐source deregulated power system

This article studies automatic generation control (AGC) problem of a realistic, multi-source deregulated power system with thyristor controlled phase shifter (TCPS) in the tie-line for damping the inter-area power oscillations. In this direction, an intelligent integration of a commercially available, relatively low rating efficient energy storage system in the form of Ultrabattery for AGC enhancement is proposed. Herein, a two-level supervisory cascade control scheme is designed. The supervisory controller comprises of a genetically tuned fuzzy logic controller which ensures the operation of Ultrabattery within its regime of operation while supervising a conventional main controller in the inner loop. The exchange of desired power between the power system and Ultrabattery is governed by the main controller whose parameters are tuned offline using optimization toolbox in MATLAB. To make the power system model realistic, effects of generation rate constraint, governor dead band, boiler dynamics, and communication time delay have been incorporated. Extensive simulation studies conducted on a well-known benchmark two-area power system under various market scenarios demonstrate the effectiveness of the proposed scheme. The results obtained illustrate a substantial mitigation of low magnitude oscillations with TCPS in the tie-line. Following the introduction of an Ultrabattery rated at just 1% of the area capacity in coordination with TCPS, an improvement of at least 87% in the system performance index is achieved. Finally, a sensitivity analysis validates the robustness of the proposed scheme under varying system parameters and market scenarios.

Stabilization of inter-area oscillations in two-area test system via centralized interval type-2 fuzzy-based dynamic brake control

Inter-area oscillations are, by far, the most detrimental oscillation category to the integrity of synchronously interconnected power systems. Inter-area oscillations are characterized by the inherent weak damping. The inherent poor damping associated with the inter-area oscillations leaves open wide probabilities for irrevocable widespread blackouts with the consequent eventual devastating outcomes measured in terms of the huge economic casualties and the possible human fatalities. The main purpose of this work is to mitigate inter-area power oscillations. This article explores the effectiveness of dual thyristor controlled braking resistor units with Interval Type-2 fuzzy-based centralized architecture for neutralizing the jeopardy of inter-area power oscillations in Kundur’s two-area test system using MATLAB™/Simulink environment. The effectiveness of the proposed scheme is examined by considering four case studies with different degrees of severity. The simulation results show that the proposed scheme is simple yet effective in treating the inter-area oscillations appropriately under the considered case studies.

Inter-Area Oscillations Stabilization by Type-2 Fuzzy Based Novel Resistor Brake Model

Inter-area power oscillation is an inherent problem of weakly interconnected power systems. This paper introduces fuzzy logic controller of Type-2 to organize the interventions of novel resistor bake model for inter-area oscillation stabilization in Kundur's two-area benchmark test power system via MATLAB/Simulink-based modelling and simulation environment with the help of Interval Type-2 fuzzy logic controller toolbox. The propositioned controller uses the relative kinetic energy deviation between the two areas as an input control signal. Three case studies, including small, mild, and severe disturbances should elucidate the effectuality of the propositioned scheme. The obtained comparative time-domain simulation results should prove that the suggested stabilization regime is a reliable mean for treating the issue of inter-area power oscillations.

Stabilization of Inter-Area Oscillations in a Two-Area Test System via Interval Type-2 Fuzzy Based Dynamic Brake Control

Inter-area oscillations are, by far, the most detrimental to the synchronous integrity of interconnected power systems. This detriment comes from their wide frequency spectrum and the large numbers of the participant generators. The inherent poor damping associated with the inter-area oscillations leaves open wide probabilities for irrevocable widespread blackouts with the consequent eventual devastating outcomes measured in terms of the huge economic casualties and the possible human fatalities. This article explores the influences of the Interval Type-2 fuzzy logic-based strategized dynamic braking interventions of dual brake models, namely Thyristor Controlled Braking Resistors (TCBRs), for neutralizing the jeopardy of negatively damped inter-area power oscillations in Kundur’s two-area test system, using MATLAB™/Simulink environment. The relative inner generator's speed deviation is employed in this work as a control signal to the proposed controller. The effectiveness of the proposed scheme is authenticated by considering four case studies with different severity degrees. By analyzing the performance repercussions due to four disturbances, without the implementation of the proposed scheme, the unstable nature of the system responses is clearly noticed. With the implementation of the proposed scheme, the system oscillatory behavior is stabilized in an appropriate manner. The performed comparative non-linear time-domain simulation results emphasize the great potential of the proposed scheme in mitigation of inter-area power oscillations according to the considered disturbances. The proposed scheme is simple yet effective in treating the inter-area oscillations appropriately under the considered case studies.

Grid-Forming Power Converters Tuned Through Artificial Intelligence to Damp Subsynchronous Interactions in Electrical Grids

The integration of non-synchronous generation units and energy storage through power electronics is introducing new challenges in power system dynamics. Specifically, the rotor angle stability has been identified as one of the major obstacle with regards to power electronics dominated power systems. To date, conventional power system stabilizer (PSS) devices are used for damping electromechanical oscillations, which are only tuned sporadically leading to significant deterioration in performance against the ever-changing operating conditions. In this paper, an intelligent power oscillation damper (iPOD) is proposed for grid-forming converters to attenuate electromechanical inter-area power oscillation. In particular, the iPOD is applied to a synchronous power controller (SPC) based grid-forming power converter to increases gain of the active power control loop at the oscillatory frequency. Predictions regarding the mode frequency, corresponding to the current operating points, are given by an artificial intelligence ensemble model called Random Forests. The performance of the proposed controller is verified using the two area system considering symmetrical fault for random operating points. In addition, a comparison with PSS installed in each generator reveals the individual contribution with respect to the inter-area mode damping.

A Coordinated Controller Design for DFIG-Based Multi-Machine Power Systems

This paper proposes a novel framework that enables the simultaneous coordination of the controllers of doubly-fed induction generators, synchronous generators, and static compensator devices. The proposed adaptive zero dynamics based approach aims at enhancing the transient stability and improving the voltage regulation of multi-machine power systems under a wide range of operating conditions. The proposed approach was implemented to Kundur's four-machine two-area and the IEEE 39-bus power systems. Its performance was assessed in the presence of various faulty scenarios and disturbances. Eigen-value analysis, time domain simulations, and transient stability margin analysis (measured by critical clearing time) were carried out in the performance assessment. Comparison analysis with other control approaches was also conducted to highlight the effectiveness of the proposed approach. Enhancing the power and voltage stability of large scale multi-machine power systems, damping inter-area power oscillations, and providing faster post-fault recovery time are among the positive features of the proposed approach.

A Dynamic State Estimator Based Control for Power System Damping

Interarea power oscillation damping enhancement in large interconnected power systems is often accomplished using supplementary controls at the synchronous machines involved and with the use of flexible ac transmission system devices. The power system literature has demonstrated that wide area signals could be more effective than the local signals for these controllers. In some cases where phasor measurement units are used, all the required control signals may not be available. To alleviate these cases, control signals are obtained using estimated signals from a “dynamic state estimator,” and a robust supplementary controller is deployed. In this paper, the cited strategy is illustrated using a static var compensator. The feasibility of the proposed method has been demonstrated on the IEEE 50-generator test system.

Coordinated Supplementary Damping Control of DFIG and PSS to Suppress Inter-Area Oscillations With Optimally Controlled Plant Dynamics

This paper proposes a design method to coordinate dual-channel supplementary damping controllers (SDCs) of doubly-fed induction generators (DFIGs) and power system stabilizers (PSSs) for suppression of inter-area power oscillations. A dynamic performance index is introduced to measure the dynamics of the conventional synchronous generator and DFIG during the damping control process. Hence, the proposed method designing the PSS and SDC is formulated as an optimization problem with the objective function being the sum of weighted performance indexes and the constraints indicating the requirements on the damping of the inter-area modes. Solving the optimization problem can obtain the optimal SDC and PSS, which can meet the required damping results as well as optimize dynamics of the controlled plants. Moreover, by adjusting weights in the objective function, the damping control burden can be flexibly and feasibly allocated between active and reactive power channels of DFIGs or among the damping controllers. Simulations with the modified New England and New York interconnected system prove that the proposed optimization based tuning method can not only robustly coordinate the PSS and SDC to effectively damp inter-area oscillations but also improve the dynamics of controlled plants during the damping control process over different operating conditions.

Effects of two‐area variable inertia on transient stabilisation in interconnected power system with DFIG‐based wind turbines

This study investigates a novel operating method of the interconnected power grid to improve dynamic stability using variable inertia control of large wind farms. In this scheme, the system inertia is considered as an adjustable operating parameter which can be regulated for inter-area power oscillation control and frequency support. Based on the linear state equations derived from a two-area interconnected power system, the effect of the controlled inertia on power oscillation damping is evaluated theoretically considering the different cases of power feeding and receiving networks. The respective wind turbine variable inertia control strategies for the feeding and receiving regional networks are proposed to enhance both inter-area power oscillation damping and frequency stability. A typical two-area interconnected power system with a high 30% wind penetration is simulated, which consists of four conventional power plants and two doubly fed induction generator (DFIG)-based wind farms. The results demonstrate that by using the proposed control scheme, the frequency stability and the inter-area oscillation damping are both significantly improved for the more effective inertia support in the interconnected power system.

Coordinated design of PSS and TCSC to mitigate interarea oscillations

Abstract Thyristor controlled series compensator (TCSC) as a promising series flexible AC transmission system (FACTS) device is generally used for controlling the real power flow in transmission lines. It can increase the system stability as the complementary functionality by minimizing the power oscillations. The effectiveness of TCSC in its primary and supplementary applications depends on the selection of its optimal location and defining a proper input signal. In this paper, a new method based on the active power sensitivity approach is applied to find the optimal location of TCSC. In addition, Hankel singular values (HSVs) and right half plane-zeros (RHP-zeros) analyses have been proposed to find the most appropriate stabilizing input signal for the supplementary functionality of TCSC to damp out the interarea modes of oscillation. Finally, the optimal design of power oscillation damper (POD) and simultaneous coordinated design of power system stabilizer (PSS) and POD are implemented separately in a large-scale power system. The tuning problem of POD-TCSC parameters as well as the coordinated POD-TCSC & PSS are converted to a multi-objective optimization problem and solved using particle swarm optimization (PSO) algorithm. The performance of the proposed method has been validated through eigenvalue analysis and nonlinear time domain simulation in a 16-machine 68-bus test system. The simulation results show a satisfactory robust performance with an excellent capability in damping of local and interarea power oscillations.

Design and implementation of an identifier system for inter-area power oscillations

Identifying inter-area oscillations can be a challenge for interconnected grids. Two identifier algorithms (FBMSWA and TBR-EMD) proposed to detect these oscillations are comparatively tested in this research. FBMSWA is implemented with T-STATCOM to damp out 0.15Hz low-frequency inter-area oscillation after interconnection Turkey with ENTSO-E. Developed TBR-EMD algorithm has certain achievements, e.g. admissible for real time, handling intermittency problem of EMD, proved by real data.

Power system stabilizers based on distributed energy resources for damping of inter-area oscillations

This paper deals with inter-area power oscillations damping enhancement by distributed energy resources contained in typical micro grid. Main idea behind this work is to use distributed generation and distributed storage, such as battery energy storage to mimic conventional power system stabilizer, but with regulating active power output, rather than reactive power, as in standard power system stabilizer realization. The analysis of the small signal stability is established for four-machine, two-area system, with inverter based micro grids in each area. Dynamic simulation results are included in this work and they show that proposed controller provides additional damping effect to this test system.

Application of the Phase Compensation Method for the Design of a DC/AC Converter-Based Stabilizer to Damp Inter-Area Power Oscillations

The phase compensation method was proposed based on the concept of the damping torque analysis (DTA). It is a method for the design of a power system stabilizer (PSS) to suppress local-mode power oscillations in a single-machine infinite-bus power system. This paper presents the application of the phase compensation method for the design of a DC/AC converter-based stabilizer to damp inter-area mode power oscillations in a multi-machine power system. The application is achieved by examining the direct damping contribution of the stabilizer to inter-area power oscillations without relying on DTA. The simplicity and localization of the phase compensation method are retained in the application presented in the paper, as the design requires only locally available transmission line information and DC/AC converter unit parameters.

Robustness of an energy storage system-based stabiliser to suppress inter-area oscillations in a multi-machine power system

In order to understand how an energy storage system (ESS)-based stabiliser suppresses a power system inter-area oscillation in a multi-machine power system, this study proposes a tie-line power oscillation-related ESS linearised model. Based on the linearised model, a general conclusion is established to assess the capability of the ESS-based stabiliser to affect the damping of the inter-area power oscillation. Analysis derived from the general conclusion explains how and why the robustness of the ESS stabiliser is different to the variations of the loading conditions of the tie transmission line when the stabiliser is realised by controlling the exchange of either active or reactive power between the ESS and the rest of the power system. It is analytically concluded that when the stabiliser is implemented via controlling the exchange of active power, the stabiliser is of better robustness. The study presents an example multi-machine power system installed with a battery energy storage system (BESS)-based stabiliser. Results of eigensolutions computation and non-linear simulation demonstrate and confirm the analytical conclusion about the robustness of the ESS-based stabiliser in suppressing the inter-area power oscillation.

The Unified Design for Inter-Area Stability Control Based on Backstepping

This paper proposes a unified method for inter-area power oscillations which is the key to solve coordination problems caused by different mathematical models and control theories. Firstly, the unified model, breaking the constraints of the network topology, component and the precise extents in the process, is established based on global signals. Secondly, making use of the structural feature of the unified system model, it combines advanced control theory to resolve the problem of parameter uncertainty and model error. Finally, the control law is effectively derived with backstepping method. The simulation results in Matlab show the validity of the proposed method.

An Adaptive Controller for Power System Stability Improvement and Power Flow Control by Means of a Thyristor Switched Series Capacitor (TSSC)

In this paper, a controller for a thyristor switched series capacitor (TSSC) is presented. The controller aims to stabilize the power system by damping interarea power oscillations and by improving the transient stability of the system. In addition to this, a power flow control feature is included in the controller. The power oscillation damping controller is designed based on a nonlinear control law, while the transient stability improvement feature works in open loop. The damping controller is adaptive and estimates the power system parameters according to a simplified generic model of a two-area power system. It is designed for systems where one poorly damped dominant mode of power oscillation exists. In the paper, a verification of the controller by means of digital simulations of one two-area, four-machine power system, and one 23-machine power system is presented. The results show that the controller improves the stability of both test systems significantly in a number of fault cases at different levels of interarea power flow.