Kundur's Two-area 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

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.

Model-Predictive Control Design for Power System Oscillation Damping via Excitation – A Data-Driven Approach

This paper presents a novel power system oscillation damping controller design based on a data-driven model-predictive control (MPC) approach. The system dynamics are extracted from the measurements and applied to the synthesis of control actions in an equation-free manner, without requiring explicit knowledge of the underlying system model. Dynamic mode decomposition with control (DMDc), originating from the Koopman operator theory, connects the collected data with the nonlinear dynamical system modeling. The discrepancy between the model identified by DMDc and the real plant is labeled as a total disturbance. It is estimated in real time by an extended state observer (ESO) and mitigated via a linear MPC, assuming the estimate to be constant over the prediction horizon. The overall control framework is referred to as <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ESO-Koopman-MPC (EKM)</i> . Two <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">EKM</i> -based oscillation damping controllers are proposed - a standalone PSS and an integrated AVR+PSS. The controller operation is illustrated on the single machine infinite bus system (SMIB), Kundur two-area system and IEEE 39-bus system, and the performance is compared with conventional power system stabilizers (CPSSs) under various test scenarios.

The Impact of Frequency Support by Wind Turbines on the Small-Signal Stability of Power Systems

Rising wind energy integration, accompanied by a decreasing level of system inertia, requires additional sources of ancillary services. Wind turbines based on doubly fed induction generators (DFIGs) can provide inertial and primary frequency support when equipped with specific controls. This paper investigates the effect of frequency support provision by DFIGs on the small-signal stability of power systems. To this end, a modified version of the Kundur two-area test system is employed to analyze different scenarios. Wind energy generation is either added to the existing system or displaces part of the synchronous generation. Simulations show that primary frequency support tends to improve the damping of electromechanical oscillations and deteriorate it for converter control-based ones. On the other hand, the inertial response depends on the control parameters.

Seamless Transition and Fault-Ride-Through by Using a Fuzzy EO PID Controller in AVR System

One of the most crucial control aspects in electric power networks is ensuring constant voltage levels throughout different circumstances. To overcome this problem, an automatic voltage regulator (AVR) is installed in the electrical power networks to preserve the voltage at its allowable range. In this paper, a fuzzy-based PID controller was used to enhance the AVR dynamic performance under several operating conditions. Moreover, an Equilibrium Optimizer (EO) algorithm was used to initialize the controller gains. The validation of the proposed controller was proven through three different systems. The first was a simple AVR system under fixed and dynamic references. The proposed fuzzy EO PID controller proved its superiority in this case through the reduction of voltage overshoot by around 3–28% compared with the reported methods in the literature. Then, the fault-ride through capability of the proposed controller was proven through the second system, which was the Kundur two-area system suffering from a 3-phase fault condition, where the overshoot with the proposed controller was reduced by 4–7% compared with the default controller and modern weighted method reported in the literature. Lastly, an IEEE 9-bus system performance was tested with the proposed controller under normal, faulty, and dynamic loading conditions. Again, the proposed controller succeeded in reducing the maximum overshoot by around 5% compared with the default controller in the system. Moreover, the proposed controller achieved a seamless transition between the islanding and grid-connected mode of operation.

Power system transient stability improvement with FACTS controllers using SSSC-based controller

Early power systems were rudimentary and local in nature. Power consumption has risen quickly in recent years, resulting in more complicated systems. However, expansion of transmission and generating is limited due to limited resource availability and tight environmental regulations. As a result, today's power systems are increasingly loaded and running under stress, putting them close to their transient stability limits. The study discussed in this paper focuses on employing contemporary PSS to improve power system reliability. The work presented in this thesis mainly focuses on power system stability improvement using modern PSS. In modern power systems trend of using wide area damping controllers and wide area signals are increasing. Also Flexible AC Transmission Systems (FACTS) based controllers are most suitable for stability enhancement and power control. This method proposed tie line power as a broad area control signal for the Static Synchronous Series Compensator (SSSC) based controller based on the geometric measure of joint index value. Kundur's two-area, four-machine system is controlled by this controller. For this system, the effectiveness of the selected signal is applied to an SSSC-based controller. The results reveal that the picked signal performs better than the non-selected signal (rotor speed deviation).

Improving Dynamic Performance of Low-Inertia Systems Through Eigensensitivity Optimization

An increasing penetration of renewable generation has led to reduced levels of rotational inertia and damping in the power network. The consequences are higher vulnerability to disturbances and deterioration of the dynamic response of the system. To overcome these challenges, novel converter control schemes that provide virtual inertia and damping have been introduced, which raises the question of optimal distribution of such devices throughout the network. This paper presents a comprehensive framework for performance-based allocation of virtual inertia and damping to the converter-interfaced generators in a detailed low-inertia system. This is achieved through an iterative, eigensensitivity-based optimization algorithm that determines the optimal controller gains while simultaneously preserving small-signal stability and ensuring that the damping ratio and frequency response after disturbances are kept within acceptable limits. Two conceptually different problem formulations are presented and validated on a modified version of the well known Kundur's two-area system as well as a larger 59-bus South-East Australian network.

Identification of Interarea Modes From Ambient Data of Phasor Measurement Units Using an Autoregressive Exogenous Model

Various modal identification methods for interarea modes have been developed to improve identification accuracy by overcoming the measurement noise in ambient data of phasor measurement units (PMUs). In this study, a modal identification method that is insensitive to measurement noise is proposed by introducing bandpass filters, which extract a modal signal from an autocorrelation function of PMU ambient data. The bandwidth of the filters is set to be adequately narrow such that the noise can be rejected sufficiently. To reduce the computational burden of the proposed method, the filters are designed by transforming a reference lowpass filter. An autoregressive exogenous (ARX) model of interarea modes is applied to the extracted modal signal. The parameters of the ARX model are estimated for modal identification via the least squares method. The identification accuracy of the proposed method is compared with those of conventional modified extended Yule Walker and discrete Fourier transform methods with respect to the signal-to-noise ratio and modal damping by using synthetic ambient data. Finally, the feasibility of the proposed method is demonstrated by identifying interarea modes of Kundur's two-area four-machine system and two real power systems in South Korea.

Parameters determination of time-delayed embedding with application to Koopman operator-based model predictive frequency control

Power systems around the world have been registering a degenerating inertial response in view of the growth of inverter-based resources along with the withdrawal of conventional coal units. Therefore, there is a need for swift frequency support and its control, preferably by means of power electronic-interfaced storage devices, owing to their beneficial capabilities. Despite being particularly efficient, pragmatically, the traditional model-based non-linear control techniques are not highly popular in power system control design, primarily due to the complications faced in obtaining accurately suitable models for certain power system components. Lately, the modelfree Koopman operator-based model predictive control (KMPC) has proven to be highly conducive for data-driven non-linear control design. The principle behind KMPC is to change the coordinates in a manner to get an approximately linear model, which can then be controlled using a linear model predictive control. In this study, we employed time-delayed embedding of measurements to reconstruct a new set of preferable coordinates, thereby suggesting an approach for finding the optimal number of time lags and the embedding dimensions which are the key parameters of this algorithm. The efficacy of this KMPC framework is established by adopting a decentralized frequency control problem through a decoupled synchronous machine system, which we proposed for both the Kundur two-area system as well as the IEEE 39-bus test system.

Event‐triggered load frequency control for multi‐area power systems based on Markov model: a global sliding mode control approach

In this study, a new method is put forward for the stability and stabilisation analysis of the event-triggered load frequency control (LFC) with interval time-varying delays, considering the global sliding mode controller. To lighten the network bandwidth and save more limited networked resources, the event-triggered scheme is optimised through quantum genetic algorithm, according to different circumstances. Additionally, global sliding mode control (GSMC) scheme is proposed to provide stronger robustness performance, which against the frequency deviation caused by power unbalance or transmission time delays better. Based on the proposed schemes, multi-area LFC for the power system model is formulated as a Markov jump linear system model, considering transmission time delays and external disturbances. By applying improved Lyapunov stability theory, criteria about the stability and stabilisation conditions for multi-area power system can be deduced in terms of linear matrix inequality. Finally, to validate a more realistic LFC application, the proposed event-triggered GSMC is also deployed on Kundur's two-area test system. Simulation studies are carried out to illustrate the effectiveness and superiority of the developed schemes.

Wide-area oscillation damping in low-inertia grids under time-varying communication delays

Wide-Area Control (WAC) can be efficiently used for oscillation damping in power systems. However, to implement a WAC, a communication network is required to transmit signals between the generation units and the control center. In turn, this makes WAC vulnerable to time-varying communication delays that, if not appropriately considered in the control design, can destabilize the system. Moreover, with the increasing integration of renewable energy resources into the grid, usually interfaced via power electronics, power system dynamics are becoming drastically faster and making WAC more vulnerable to communication delays. In this paper, we propose a design procedure for a delay-robust wide-area oscillation damping controller for low-inertia systems. Its performance is illustrated on the well-known Kundur two-area system. The results indicate that the obtained WAC successfully improves the oscillation damping while ensuring robustness against time-varying communication delays.

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.

Application of phase sequence exchange in emergency control of a multi-machine system

Phase sequence exchange (PSE) is a recently developed emergency control technology. The effectiveness of PSE in a multi machine system is demonstrated in this paper. Two PSE device installation positions in a multi-machine system are first proposed. The first is at the outlet of each generator, and the second is at the connection lines between two large systems with weak connections. Based on extended equal area criterion (EEAC), a control method is then proposed. After the system out of step, the generator that need PSE and the power angle threshold can be determined quickly. When the threshold value of power angle is reached, the generator in the critical cluster exchanges phase sequence at the same time, which reduces the power angle of the one-machine to infinite bus (OMIB) image by 120° and increases the deceleration area of OMIB image. This prevents out-of-step conditions while maintaining the integrity of the system. The effectiveness of the PSE is verified using Kundur's two-area four-machine power system and the IEEE 39-bus system, and compared with other emergency control methods.

Frequency Regulation and Control of Grid-Connected Wind Farms Based on Online Reduced-Order Modeling and Adaptive Control

This article presents a frequency regulation and stabilization control architecture for a wind turbine generator (WTG) integrated power grid, which can be added to existing WTGs. The architecture uses online reduced-order modeling of the power grid with frequency-dependent network equivalent that can seamlessly evaluate the grid fluctuations with respect to the point of common coupling of the wind farm. Then, an adaptive control architecture with the help of an online identification routine is used to balance the torque control of the wind generator (here doubly fed induction generator is considered) such that the frequency of the system is balanced. The main advantage of the proposed architecture is that the approach ensures frequency stability during grid oscillations at any location due to grid-related or WTG-related problems. The proposed approach not only maintains the frequency within acceptable limits during oscillations, but also makes sure that voltages are at normal values. The approach can work without wind speed measurements. The architecture is evaluated using wind-farm-integrated Kundur two-area and IEEE 39-bus test systems using a real-time digital simulator.

Virtual synchronous machine-controlled grid-connected power electronic converter as a ROCOF control device for power system applications

Rate of change of frequency (ROCOF) is an indicator of frequency stability of a power system network. Maintaining the ROCOF value within the acceptable limit is a major challenge with increasing penetration of converter-based renewable energy generation technologies. A virtual synchronous machine (VSM) is proposed in this paper as a ROCOF control device with a novel battery power management algorithm to extend the lifetime of the batteries. The VSM unit consists of a DC storage connected through a three-phase voltage source converter with a harmonic filter to the grid and the corresponding local control system. The Kundur two-area system is used as a test case to analyse the performance of the VSM. A hardware prototype of the VSM with 1 kW, 200 V and 50 Hz rating is developed in the laboratory environment. The modified Kundur two-area system and the control strategies are implemented in OPAL-RT real-time simulator. The effect of VSM on the modified Kundur two-area system is analysed using the power hardware-in-the-loop concept. The experimental results indicate that the VSM is effective in reducing the ROCOF values in power system networks during rapid fluctuations in frequency caused due to the load switching events. The hardware implementation of a VSM interfaced with the modified Kundur two-area system, the novel battery power management algorithm and the application of VSM as a ROCOF control device for power system applications are the unique contributions in this paper.

New signal subspace approach to estimate the inter‐area oscillatory modes in power system using TLS‐ESPRIT algorithm

The authors propose here a new low-frequency oscillatory (LFO) modes estimation scheme by applying Karhunen–Loeve transform (KLT) with total least square estimation of signal parameter employing rotational invariance technique (TLS-ESPRIT). The proposed KLT provides the perfect decorrelation of the signal from the noise at low signal-to-noise ratio and for both white and coloured noise. KLT also maximally compress the energy of the estimated signal. KLT helps to estimate the signal subspace perfectly for any non-stationary ambient power signal with the fastest computational time. First, the authors applied the KLT denoise to the filtered signal buried with highly correlated coloured Gaussian noise through the first eigenvectors of the correlation matrix and estimated the signal subspace. Finally, TLS-ESPRIT is applied to estimate the modes of the power system. A comparative analysis of the KLT-TLS-ESPRIT with the modified TLS-ESPRIT, multi-channel wavelet transform, data driven-stochastic subspace identification, TLS-ESPRIT, Root-MUSIC, and improved Prony method is presented. To explore the real-time application of the KLT-TLS-ESPRIT, the authors considered Kundur's two-area test system and 16-machine 68-bus system using 50,000 Monte-Carlo simulations. The obtained results show that the KLT-TLS-ESPRIT accurately estimates the LFO with least mean and standard deviation as compared to the remaining six methods.

Estimating electromechanical oscillation modes from synchrophasor measurements in bulk power grids using FSSI

Multi-order stochastic subspace identification (MOSSI) has been extensively used to estimate the electromechanical oscillation modes from probing, ambient and ringdown data. It has been validated with good performances, while the computational burden is still a major obstacle. This study develops a fast iterative MOSSI (FSSI) approach for computational enhancement of MOSSI in mode estimation. In the proposed approach, an initial cluster of eigenvalues is formulated through FSSI with repetitive calculations (RCs), and electromechanical oscillation mode separation (EOMS) is utilised to discriminate the electromechanical modes. The RCs within the FSSI is calculated through changing the model order successively over the defined range given by a mean of singular values based order determination strategy. Additionally, the proposed approach is highly reliable against prevalent measurement noises owing to RCs and the EOMS. The performance of the proposed method is evaluated in Kundur's two-area test system by comparing with MOSSI, Prony and autoregressive moving average exogenous. Its applicability for both the ringdown and ambient data is also demonstrated with the phasor measurement units field-measurement data from the China Southern Power Grid. The results confirmed the accuracy, robustness and efficiency of the proposed approach for oscillation mode estimation.

Virtual Actuators for Wide-Area Damping Control of Power Systems

In this paper, a new approach to design fault-tolerant wide-area damping controllers (WADCs) is presented. Use of actuator redundancy to achieve higher reliability has always been an accepted engineering design technique and is used in this study to help ensure power system security. In our proposed method when an actuator fails or is unavailable (e.g., due to loss of communication), the supervisory controller redistributes the control signals to the remaining actuators. The WADC is initially designed to provide satisfactory damping. In the next step, virtual actuators (VAs) are designed to manage actuator failures without the need to redesign the nominal WADC. By inserting this reconfiguration block between the nominal WADC and the new actuator, there is no need to retune the WADC and the performance of the fault-free system can be recovered. Our proposed block is independent of the nominal WADC and does not need any information beyond that an actuator is unavailable. The approach is applied to Kundur's two-area system, and the 39-bus New England system. Numerical results show the effectiveness of the proposed method subjected to different failures.

Inter-Area Resonance in Power Systems From Forced Oscillations

This paper discusses a recent event in the western American power system when a forced oscillation was observed at a frequency that was close to a well-known 0.38-Hz inter-area electromechanical mode frequency of the western system. The event motivates a systematic investigation in this paper on the possibility of resonant interactions between forced oscillations and electromechanical inter-area oscillatory modes in power systems. When the natural oscillatory mode of a power system is poorly damped, and the forced oscillation occurs at a frequency close to system mode frequency at critical locations for the mode, resonance is observed in simulation test cases of the paper. It is shown that the MW oscillations on tie-lines can be as high as 477 MW from a 10-MW forced oscillation in Kundur test system because of resonance. This paper discusses the underlying system conditions and effects as related to resonance in power systems caused by forced oscillations and discusses ways to detect such scenarios using synchrophasors. Simulated data from Kundur two-area test power system as well as measurement data from western American power system are used to study the effect of forced oscillations in power systems.

PSS parameters values finding using SMVSDFT objective function and a new technique for multi-objective function in a multi-machine power system

In power systems, the application of power system stabiliser (PSS) has been proved to lead to the stability of power systems. It is necessary to determine PSS parameters, exactly. In this study, a new objective function is presented to study stability of the power system. This function applies for the obtaining of PSSs parameters also, when there are several PSSs simultaneously in a multi-machine power system with two areas. Stability of a multi-area power system is a multi-objective problem, so in this study, the use of a new multi-objective function has been presented. The power plant system that is simulated in this study is the model of Kundur's two-area power system. PSSs parameters are optimised particle swarm optimisation and genetic algorithms and by using a new multi-objective function algorithm, simultaneously. The responses are compared with PSS parameters for the Kundur's two area power system. The responses PSO-PSS and GA-PSO are also compared with each other and of the multi-objective function algorithm and of the efficiency new objective function called SMVS-DFT will be proved.