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Co-simulation of heterogeneous systems allows for in-depth analysis of various aspects of power systems’ operation while staying within the environments of the simulation tools that are best fit to represent their respective domains. Equipped with a proprietary co-simulation platform, the paper focuses on the issue of power-conjugate coupling between parts of power grids modeled in transient stability and electromagnetic transient simulation tools. The problems of co-simulation stability and precision in presence of delays are tackled by means of designing a proper coupling interface. It is shown that two established interface methods – the V-I method and the Transmission Line Interface – are special cases of a generalized interface framework proposed in the paper. Moreover, a new interface algorithm is described by parametrizing the generalized framework. Analytical tools are also formulated to aid in the analysis of interface stability and precision via the concepts of passivity and transparency. Simulation results of benchmark systems of various complexity demonstrate the application of the developed power coupling interface.

The article proposes a computationally efficient and robust method for estimating impulse or frequency response in the context of black-box multiple-input-multiple-output linear model identification of large power systems from simulations. The proposed approach is validated in conjunction with two realization algorithms – ERA method that is based on the established Ho-Kalman procedure for minimal realization, and the relatively new Loewner matrix based method. Practical aspects of identification in presence of numerical noise and nonlinearities are discussed. Study cases presented in the article include a linear model equivalent of a large-scale power system and the full-scale nonlinear transient model of the Eastern Interconnection.

Developing a general and stable numerical interface for power hardware-in-the-loop (PHIL) applications is a major challenge. This paper proposes a stable, robust and precise implementation of a multi-time-step interface for a PHIL simulator based on the Bergeron transmission line model (BTLM). Two limitations of the transmission-line-based interface were identified, and remedial strategies were formulated in order to ensure that the interface was compatible with the PHIL application. Stability and passivity analyses were then conducted on the resulting interface to verify its performance. The proposed interface was implemented in an experimental 3-kVA PHIL setup, using a custom-made switching power amplifier (PA). Multiple tests were performed in order to demonstrate the stability and accuracy of the closed-loop system under a wide range of operating conditions and with various devices under test (DUTs). Experimental results were obtained from islanding tests involving different simulated load configurations and solar inverter responses to network disturbance while operating in a closed-loop configuration.

This paper performs a fundamental study of very low frequency oscillations characterized by a common mode shape at all system busses (same magnitude and phase). Also known as global or frequency control oscillation mode (below 0.1 Hz), it determines frequency response performance according to NERC requirements. When poorly damped, it poses a serious threat to small signal stability in islanded interconnections (e.g., Quebec and Texas) or hydro-dominated low-inertia systems (e.g., Columbia and Ecuador). Building on the classical damping and synchronizing torque concept, an improved understanding of underlying mechanisms behind common oscillation mode apparition and its frequency and damping are achieved through analytical assessment of the impact of turbine-governor types, load voltage sensitivity as well as system inertia. By revisiting frequency stability definition in light of the damping-synchronizing torque concept, the paper in essence uncovers the important yet poorly understood notion of small-signal (oscillatory) frequency stability.

This paper provides a very detail-oriented study to prepare a full pathway for having an advanced closed-loop control implemented on selected controllable assets of N ew York Power Authority (NYPA), including wind generation to improve dynamic stability performance. The detailed methodology to identify the most effective control devices is outlined. Coordinated tuning of MBPSS is performed. The results show that the advanced closed-loop control with NYPA assets improves the dynamic stability performance of New York power grid and even of Eastern Interconnection as a whole.

The paper presents the results of the power hardware-in-the-loop study of four commercially available residential solar inverters. This study was performed for Hydro-Quebec TransEnergie as part of a mandate to characterize the behavior of PV inverters and assess their impact on the transmission system. The particular focus of the paper is the behavior of the inverters in the conditions of weak network or high penetration level. Firstly, an analysis using a simple network model is done, and the resonance conditions are determined via linear analysis and subsequent experimental tests. Furthermore, a realistic model of an actual rural distribution feeder in Quebec is used to validate the findings. The results demonstrate that the undesirable effects of the resonance are common among various commercial products and can potentially disrupt normal operation of the power grid.

Direct methods have been a promising development for decades, receiving, however, less attention recently. One of the reasons is the limited capacity to include more realistic models of the power systems equipment. This paper derives a structure-preserving analytical energy function for a sixth-order synchronous generator model with subtransient dynamics included. The procedure used to construct the energy function is demonstrated to be applicable to simple governor models as well. The energy function is used to assess critical clearing times for multiple contingencies via a potential energy boundary surface method in the IEEE 10-generator 39-bus benchmark system. Some comparative analysis with transient fourth-order models is performed. The results are validated against simulations using a commercial transient stability package.

This study demonstrates the application of a wide-area control scheme based on multi-functional multi-band power system stabilisers (MF-MBPSS) in New York State grid for the purpose of system stability improvement. The aspects of oscillation damping, frequency and voltage closed-loop control are considered. The study describes useful techniques for placing and tuning of MF-MBPSSs based on simulation models and suitable techniques for very large power grids. The application of these concepts is demonstrated on a transient stability model of Eastern Interconnection. Results show a reduction of system frequency nadir during generation outages, significant improvement in damping of post-disturbance swings and capabilities to contribute to long-term voltage stability using only a modest amount of dynamic reactive power resources.

The purpose of this paper is to present a collaborative simulation setup that aims to better represent the behavior of a smart grid containing components that operate in different system domains, such as communications/cyber, electrical and control. This setup uses a middleware known as InSystemLab (ISL), which offers a proper synchronization and a numerical stabilization method fully compliant with the Functional Mock-up Interface (FMI) standard for cosimulation. ISL also facilitates the combination of various off-the-shelf computer simulators, namely EMTP-RV, HYPERSIM, Simulink and OPNet, by adopting a publisher/subscriber approach included in the High Level Architecture (HLA) standards of cosimulation. This increased flexibility allows simulating large-scale systems covering large areas and including detailed models for specific areas, e.g. substations and relays with communications protocols. The capabilities of the proposed approach are demonstrated on a benchmark power grid, modified to add communication systems and component models coming from simulations or directly from manufacturers. The benefits of this approach are highlighted by showing how each simulator contributes to a global analysis of the grid by using its proper development environment, and focusing on the impact of cyber-attacks and other perturbations on an IEC 61850 model of the communication network on the rest of the components and on the power grid stability.

This paper proposes a quasi-steady-state modeling approach for an approximation of long-term frequency dynamics in power systems. A specific phenomenon of concern is an onset of frequency swings during load/generation imbalance scenarios. The effects of system voltage characteristics, system inertia, and, more importantly, damping controllers are explained and quantified using the described quasi-steady-state models. Application of the methodology to a 14-generator benchmark system demonstrates that described models are suitable for simulation of different disturbance scenarios that can trigger frequency instability. Moreover, linearization of the proposed models can provide convenient means for impact assessment and coordinated design of damping controllers. To demonstrate this, coordinated tuning of multiband power system stabilizers to improve frequency dynamics has been performed and validated through nonlinear simulations using a commercial transient stability software.

This paper provides a very detail-oriented study to prepare a full pathway for applying the technology of multi-band power system stabilizers (MBPSS) to a large industrial interconnection-level power system, the Eastern Interconnection network, with a few selected controllable assets of New York Power Authority (NYPA), including wind generations to improve dynamic stability performance with the emphasis on primary frequency control. The detailed methodology to identify the most effective control devices is outlined. Coordinated tuning of MBPSS is performed. The impact of different wind generation levels on the frequency control is demonstrated. The results show that the technology of the advanced closed-loop control with a limited number of NYPA assets improves the dynamic stability performance of the New York power grid and even of the Eastern Interconnection as a whole. Evaluation of the economic benefit from frequency improvement is analyzed.

The challenge of microgrid protection is associated with many factors, such as frequently changing conditions and topology, lack of established power flow direction, presence of inverter-interfaced generation, among others. To overcome the challenges faced by the conventional protection, the paper demonstrates the application of a synchrophasor-based state estimation algorithm for protection of microgrids. The approach is tested on a model of an existing microgrid/test feeder. The results show the inherent flexibility of the approach towards changing conditions of microgrid operation. It requires minimum coordination that ensures quick detection of various types of faults in different locations.

Multi-band power system stabilisers (MB-PSSs) PSS4B (IEEE standard 421.5-2005) are advanced power system damping controllers that have evident advantages over conventional PSSs in damping low-frequency oscillatory modes. However, finding optimal settings for such controllers is challenging due to the increased complexity of the PSS4B structure. This study describes a methodology for MB-PSS parameter optimisation based on an improved modal performance index as a measure of the controller's stabilising effect. The tuning problem is formulated as a non-linear constrained optimisation search method: proposed modal performance index is chosen as an objective function to be minimised, while properly selected constraints ensure stability of the closed-loop system and robustness of the proposed design. The methodology is demonstrated on a benchmark system that is based on an existing network. Comparative analysis between the MB-PSSs with optimised settings and speed-based PSS1A-type stabilisers designed using the conventional methods show the practicality and effectiveness of the proposed methodology. The implemented approach has an advantage of being scalable and suitable for the model-based tuning of feedback controller of general structure. Additionally, several performance metrics and non-linear simulations in the ElectroMagnetic Transient Program (EMTP) software confirm superior characteristics of PSS4B.

This paper discusses an adaptive wide-area primary frequency controller that improves the dynamic frequency behavior, and consequently overall stability of the power grid. The control scheme is based on wide-area measurement of frequency and rate of change of frequency at several buses in the system, processing the measured values, and modulating the reference voltage of the shunt connected Flexible AC Transmission Systems (FACTS) devices and Power System Stabilizers (PSSs). The control parameters are adaptively being tuned up on a real-time basis according to 1) the severity of the disturbance and 2) the way it affects the power system, which meaning the areas that have been more affected would make greater contribution to modulating the reference voltage signals. The building block of the controller is the Multi-functional Multi-band Power System Stabilizer (MF-MBPSS) technology. This type of advanced control, developed by Hydro-Quebec, is an evolution of the existing IEEE PSS4B type stabilizer that is capable of utilizing wide-area measurements available from Pharos Measurement Units (PMUs) or other devices. The performance of the proposed controller has been verified on the PSS/E model of the Eastern Interconnection which is being widely used for transmission planning and several other system studies in the state of New York.

The paper discusses the impacts of the advanced closed loop control through multi-functional multi-band power system stabilizers on dynamic performance of the New York State power grid. Reference signal modulation of certain devices in the system has been shown to improve system damping and affect frequency response during generator outage scenarios. The methodology behind the development of system models and subsequent tuning of the controllers is discussed. Results demonstrate how feedback control of various power system equipment, including those that are electronically-interfaced, can aid in improving dynamic behavior of large interconnected systems.

This paper proposes a topology for the combined frequency/oscillation damping active power control loop for type 4 wind turbines. In order to assess the effects of standard transient network frequency support control loops and the established controller topology on frequency response a quasi steady-state frequency model for the wind turbine equipped with frequency support auxiliary loop is developed. The performance of the proposed controller is then validated on a 14-generator benchmark system with installed wind capacity implemented in an Electromagnetic Transient Program. Positive impacts of the controller on frequency response, long-term frequency stability and inter-area oscillatory mode are demonstrated. The issues of controller tuning with respect to torsional interactions are also discussed.

The ability of modern wind turbine generators (WTGs) to rapidly and independently control active and reactive power outputs makes them attractive for the purpose of oscillation damping in power systems through P and Q modulation auxiliary loops. However, the problem of coordination and interaction of P and Q control loops emerges. The paper proposes a methodology for coordinated design of active and reactive power modulation loops of wind turbine generators. The method is based on a nonlinear constrained optimization approach with a properly chosen modal performance index as an objective function. The coordinated design is validated on the two-area benchmark system with a wind farm (WF) of significant capacity. The advantage of the control loops coordination approach is demonstrated through separate and simultaneous tuning of both controllers. Results show substantial improvement in damping low frequency inter-area mode, as well as proper coordination achieved between P an Q loops through the proposed methodology.