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Showing papers on "Inertia published in 2020"


Journal ArticleDOI
TL;DR: A virtual synchronous generator control based on adaptive virtual inertia based on Lyapunov stability theory combines the merits of large inertia and small inertia, which contributes to the improvement of dynamic frequency response.
Abstract: A virtual synchronous generator (VSG) control based on adaptive virtual inertia is proposed to improve dynamic frequency regulation of microgrid. When the system frequency deviates from the nominal steady-state value, the adaptive inertia control can exhibit a large inertia to slow the dynamic process and, thus, improve frequency nadir. And when the system frequency starts to return, a small inertia is shaped to accelerate system dynamics with a quick transient process. As a result, this flexible inertia property combines the merits of large inertia and small inertia, which contributes to the improvement of dynamic frequency response. The stability of the proposed algorithm is proved by Lyapunov stability theory, and the guidelines on the key control parameters are provided. Finally, both hardware-in-the-loop and experimental results demonstrate the effectiveness of the proposed control algorithm.

152 citations


Journal ArticleDOI
TL;DR: In this paper, the authors summarized recent developments of active particles with inertia (i.e., microflyers, hop-flies, or runners) for single particle properties and for collective effects of many particles.
Abstract: Active particles that are self-propelled by converting energy into mechanical motion represent an expanding research realm in physics and chemistry. For micrometer-sized particles moving in a liquid (“microswimmers”), most of the basic features have been described by using the model of overdamped active Brownian motion. However, for macroscopic particles or microparticles moving in a gas, inertial effects become relevant such that the dynamics is underdamped. Therefore, recently, active particles with inertia have been described by extending the active Brownian motion model to active Langevin dynamics that include inertia. In this perspective article, recent developments of active particles with inertia (“microflyers,” “hoppers,” or “runners”) are summarized both for single particle properties and for collective effects of many particles. These include inertial delay effects between particle velocity and self-propulsion direction, tuning of the long-time self-diffusion by the moment of inertia, effects of fictitious forces in noninertial frames, and the influence of inertia on motility-induced phase separation. Possible future developments and perspectives are also proposed and discussed.

138 citations


Journal ArticleDOI
TL;DR: A fuzzy controller is proposed, which is augmented on the virtual synchronous generator topology to damp the perturbation during transients by increasing the inertia of the system by adding a correction term to the governor's output power that increases the system inertia duringtransients.
Abstract: The absence of rotational masses from synchronous generators in converter-interfaced microgrids leads to a lack of inertia. Consequently, the system exhibits steeper frequency variations and higher frequency nadir, which may degrade the dynamic performance and challenge the operation of sensitive equipment such as protective relays in the grid. Virtual synchronous generator is introduced as an effective solution to increase the inertial response of converter interfaced renewable energy sources. This article proposed a fuzzy controller, which is augmented on the virtual synchronous generator topology to damp the perturbation during transients by increasing the inertia of the system. The proposed fuzzy control adds a correction term to the governor's output power that increases the system inertia during transients. In order to compare the inertial response improvement, a comparison between proposed fuzzy control technique and cost function based inertia and damping coefficient optimization is done on a virtual synchronous generator platform. It is shown that online measurement based adaptive methods have a better inertial response against other time-consuming techniques. To further verification, a number of experiments are done, which confirm the merits of the proposed fuzzy based virtual synchronous generator control method.

108 citations


Journal ArticleDOI
TL;DR: The closed-loop attitude stabilization system is proved to be fixed-time stable with the convergence time independent of initial states and the attitude stabilization performance is robust to disturbance and uncertainties in inertia and actuators.
Abstract: A robust fixed-time control framework is presented to stabilize flexible spacecraft’s attitude system with external disturbance, uncertain parameters of inertia, and actuator uncertainty. As a stepping stone, a nonlinear system having faster fixed-time convergence property is preliminarily proposed by introducing a time-varying gain into the conventional fixed-time stability method. This gain improves the convergence rate. Then, a fixed-time observer is proposed to estimate the uncertain torque induced by disturbance, uncertain parameters of inertia, and actuator uncertainty. Fixed-time stability is ensured for the estimation error. Using this estimated knowledge and the full-states’ measurements, a nonsingular terminal sliding controller is finally synthesized. This is achieved via a nonsingular and faster terminal sliding surface with faster convergence rate. The closed-loop attitude stabilization system is proved to be fixed-time stable with the convergence time independent of initial states. The attitude stabilization performance is robust to disturbance and uncertainties in inertia and actuators. Simulation results are also shown to validate the attitude stabilization performance of this control approach.

103 citations


Journal ArticleDOI
TL;DR: Results confirm that the proposed dual-adaptivity inertia control strategy not only achieves rapid frequency response with slight dynamic deviations under disturbances but also strikes a balance between the frequency and power and leads to improved overall control.
Abstract: The virtual synchronous generator (VSG) improves the robustness of the inverter-interfaced distributed generator (IIDG) against instability by introducing a virtual inertia. However, the transient response of the active power and the angular frequency conflict with each other for the IIDG with fixed inertia control. It is necessary to adopt adaptive control to improve overall performances of power and frequency as the operating condition changes. This paper analyzes the impact of the inertia on power and angular frequency. A dual-adaptivity inertia control strategy is proposed to offer a responsive and stable frequency support and also achieve the balance between power regulation and frequency regulation according to different operating conditions. The principle of parameter design is given to obtain the range of adaptivity. Quantitative assessment considering the cumulative effect of the output deviation and its duration is also presented to evaluate the proposed strategy intuitively. The strategy is further verified based on PSCAD/EMTDC and a hardware-in-loop experiment platform based on RTDS. Results confirm that the proposed strategy not only achieves rapid frequency response with slight dynamic deviations under disturbances but also strikes a balance between the frequency and power and leads to improved overall control.

64 citations


ReportDOI
01 May 2020

64 citations


Journal ArticleDOI
TL;DR: Results obtained for the 39 bus New England system for various test cases, using Real-Time Digital Simulator (RTDS), prove the efficacy and superiority of the proposed approach over the existing approaches in the literature.
Abstract: System inertia plays a vital role in controlling the angular stability of the system during a disturbance. Due to increased penetration of power electronic interfaced sources, such as Solar Photovoltaic (SPV) source, the overall system inertia reduces and varies depending on their operating conditions. In this paper, an approach for online inertia estimation in the power system network with SPV sources is proposed, using the synchronized measurements from Phasor Measurement Units (PMUs). An equivalent swing equation is used to emulate the network dynamics. A relationship between the inertia constant and the roots of this equation is determined. In order to numerically obtain the roots, the Estimation of Signal Parameter via Rotational Invariance Techniques (ESPRIT) method is first used to find the modes present in the frequency signal. A new formulation is proposed to extract an equivalent mode from all the obtained modes. Also, to avoid phase step error, Rate Of Change Of Frequency (ROCOF) is estimated from the equivalent mode of the frequency signal. Results obtained for the 39 bus New England system for various test cases, using Real-Time Digital Simulator (RTDS), prove the efficacy and superiority of the proposed approach over the existing approaches in the literature.

56 citations


Journal ArticleDOI
TL;DR: An improved method to estimate the available inertia in an islanded AC microgrid, which can accurately estimate the inertia provided by the synchronous sources within the generation mix and is segregated into synchronous and nonsynchronous inertia estimation.
Abstract: This paper presents an improved method to estimate the available inertia in an islanded AC microgrid. Inertia estimation is carried out based on measured frequency response for any arbitrary disturbance that occurs in the system. Modifications are made to the conventional swing equation-based curve-fitting method to obtain an accurate estimate for a system with high penetration of renewable generations. A polynomial curve fit over the total power generation is introduced to estimate the size of the disturbance accurately. Additionally, a variable order polynomial fit is carried out over the measured frequency, which not only improves the estimate of inertia but also helps to refrain the influence of network topology and size/location of the disturbance. The test microgrid system considered is a modified Standard IEEE distribution network, which consists of radial feeders and distributed generations. Firstly, the proposed method is tested on a system with only synchronous generations to assess the accuracy of the estimate. This is followed by the integration of Type 3 and Type 4 wind turbines, and a PV array within the microgrid system. Virtual inertia control is then implemented in the wind turbines to obtain inertial support. Estimation study of the microgrid system with virtual inertia is then carried out. The developed estimation method can accurately estimate the inertia provided by the synchronous sources within the generation mix. Finally, from all the results and observations, the inertia estimation process in a microgrid system is segregated into synchronous and nonsynchronous inertia estimation.

51 citations


Journal ArticleDOI
Ismail Esen1
TL;DR: In this article, the stiffness and mass property matrices of small-scale size-dependant two-node finite element are obtained by using new shape functions derived from the static state of motion equations created using classical Timoshenko beam theory and modified couple stress theory.

49 citations


Journal ArticleDOI
15 Jul 2020-Energy
TL;DR: In this article, the impact of minimum inertia constraint on the performance of synchronous machines in European power systems was investigated and it was shown that an increasing inertia constraint elevates total generation costs, variable renewable energy curtailment and carbon dioxide emissions across Europe for an ambitious decarbonisation scenario.

47 citations


Journal ArticleDOI
TL;DR: A novel technique for tapping the virtual inertia potential of RES (Photo Voltaic system), by cultivating the the derivative control mechanism and further improves the dynamic performance of the system.
Abstract: The microgrid system with a high share of Renewable Energy Sources (RES), is the need of hour. The RES provides clean, economical and never-ending active power support to the system. However, the inertia deficiency is the negative side of RES based systems, as it adversely affects the dynamic performance of the microgrid and may lead to severe consequences like loss of synchronization and instability. For addressing the issue of inertia deficiency, several techniques were already proposed for emulating the virtual inertia. Among these, the Derivative Control Technique (DCT) is quite popular, because of its simplicity and effectiveness. The previous research work utilizes the Energy Storage System (ESS) for providing virtual inertia support through DCT during load imbalance. However, such a system neglects the possibility of extracting virtual inertia support obtained from RES. This paper proposes a novel technique for tapping the virtual inertia potential of RES (Photo Voltaic system), by cultivating the the derivative control mechanism and further improves the dynamic performance of the system. Further, the efficiency of the proposed system is evaluated through time-domain simulations under different scenarios and compare it with conventional and ESS based systems.

Journal ArticleDOI
TL;DR: In this paper a closed-form solution to the differential equation describing frequency dynamics is proposed, which allows to obtain frequency-security algebraic constraints to be implemented in optimization routines.
Abstract: A reduced level of system inertia due to renewable integration increases the need for cost-effective provision of ancillary services, such as Frequency Response (FR). In this paper a closed-form solution to the differential equation describing frequency dynamics is proposed, which allows to obtain frequency-security algebraic constraints to be implemented in optimization routines. This is done while considering any finite number of FR services with distinguished characteristics, such as different delivery times and activation delays. The problem defined by these frequency-security constraints can be formulated as a Mixed-Integer Second-Order Cone Program (MISOCP), which can be efficiently handled by off-the-shelf conic optimization solvers. This paper also takes into account the uncertainty in inertia contribution from the demand side by formulating the frequency-security conditions as chance constraints, for which an exact convex reformulation is provided. Finally, case studies highlighting the effectiveness of this frequency-secured formulation are presented.

Journal ArticleDOI
TL;DR: Eigenvalue analysis is performed to evaluate the sensitivity of the design parameters on stability of a grid-connected virtual inertia PV system for smart grid applications.
Abstract: Renewable energy sources normally provide low inertia, which allows a little time for controlling the system. The inertia emulation has recently been introduced for photovoltaic (PV) generation to fight against the small inertia and improve the energy efficiency. The main purpose of this article is to analyze the stability of a virtual inertia-based three-phase two-stage PV system for smart grid applications. Dynamics of DC/DC converter, DC/AC converter, AC side filter, virtual inertia controller, and controllers of the DC/DC and DC/AC converters are considered in the modeling procedure. Eigenvalue analysis is performed to evaluate the sensitivity of the design parameters on stability of a grid-connected virtual inertia PV system. Time-domain simulations using MATLAB/Simscape Power System toolbox are used to validate the eigenvalue analysis results.

Journal ArticleDOI
TL;DR: The proposed control strategy is implemented in the energy storage system, which provides inertia support to smooth the DC voltage under power fluctuations, and the range of virtual inertia control coefficient and damping control coefficient are determined.
Abstract: In DC microgrids, the inherent inertia from DC capacitors is low and the DC bus voltage is susceptible to power fluctuations, which results in low DC voltage quality. In this article, an inertia and damping control (IDC) method is proposed and applied in the energy storage system to strengthen the inertia and damping of DC microgrids. The proposed control strategy is obtained based on the charging and discharging conversion form of capacitors and aims to control the external characteristics of converters in DC microgrids to improve its inertia and damping feature. The small signal model of the proposed control strategy is built to identify the stability and dynamic characteristic. In order to eliminate the abrupt change in the beginning of the voltage dynamic characteristic, a feedforward control is implemented and the dynamic characteristic is revised. Then by analyzing system stability, the range of virtual inertia control coefficient and damping control coefficient are determined. Finally, hardware- in-the-loop (HIL) simulation based on RT-LAB is carried out to verify the validity of the above theoretical analysis and control strategy. In this simulation, the proposed control strategy is implemented in the energy storage system, which provides inertia support to smooth the DC voltage under power fluctuations.

Journal ArticleDOI
TL;DR: The proposed method can estimate the inertia constant under normal operating conditions, and therefore, can provide the tracking trajectory of the power system inertia constant in real-time and is validated in the IEEE 39-bus system.
Abstract: An online estimation method for the power system inertia constant under normal operating conditions is proposed. First of all, a dynamic model relating the active power to the bus frequency at the generation node is identified in the frequency domain using ambient data measured with the phasor measurement units (PMUs). Then, the inertia constant at the generation node is extracted from the unit step response of the identified model in the time domain using the swing equation. Finally, with the sliding window method and the exponential smoothing method, the estimated inertia constant is updated in real-time. Compared to the conventional methods using large disturbance data or field test data, the proposed method can estimate the inertia constant under normal operating conditions, and therefore, can provide the tracking trajectory of the power system inertia constant in real-time. The effectiveness of the proposed method is validated in the IEEE 39-bus system. The results show that the relative error of the identified inertia constant is below 5% and the identified inertia constant can be updated within 1s.

Journal ArticleDOI
TL;DR: The active power impact is reduced effectively under the circumstance of damping coefficient D ω equal to 0 and a large inertia, thus the dynamic characteristic of active power is improved and its steady-state characteristic is maintained.
Abstract: Virtual synchronous generator (VSG) simulates the first-order motion equation of a synchronous generator (SG) with the algorithm. VSG can improve the system voltage and frequency support capabilities of a microgrid or a weak grid. It is now widely applied at a high penetration level of distributed generation (DG) systems. However, because there is a contradiction between active power steady-state deviation of VSG and dynamic impact regulation, the VSG running in grid-connected mode with existing strategies cannot meet the steady and dynamic control requirements. Thus, an improved virtual inertial control strategy of VSG is proposed in this paper. The active power impact is reduced effectively under the circumstance of damping coefficient D ω equal to 0 and a large inertia, thus the dynamic characteristic of active power is improved and its steady-state characteristic is maintained. Firstly, based on the analysis of the damping coefficient effect on the system dynamic process, two forms of improved virtual inertia algorithms are put forward by cascading a differential link into different positions of the first-order virtual inertia forward channel. Then, by comparing the characteristics of the system with the two improved algorithms, the improved virtual inertial strategy based on differential compensation is proven to be better, and the design of its parameters is analyzed. Finally, simulation and experimental results verify the effectiveness of the proposed algorithm.

Journal ArticleDOI
TL;DR: The study of the correlations in the underdamped regime of the active Ornstein-Uhlenbeck model is extended to the case of a chain of active particles interacting via harmonic springs and reveals the existence of marked equal-time correlations between velocity and active force in the non-equilibrium steady state.
Abstract: We study a self-propelled particle moving in a solvent with the active Ornstein Uhlenbeck dynamics in the underdamped regime to evaluate the influence of the inertia. We focus on the properties of potential-free and harmonically confined underdamped active particles, studying how the single-particle trajectories modify for different values of the drag coefficient. In both cases, we solve the dynamics in terms of correlation matrices and steady-state probability distribution functions revealing the explicit correlations between velocity and active force. We also evaluate the influence of the inertia on the time-dependent properties of the system, discussing the mean square displacement and the time-correlations of particle positions and velocities. Particular attention is devoted to the study of the Virial active pressure unveiling the role of the inertia on this observable.

Journal ArticleDOI
TL;DR: In this paper, the stability of pipes conveying fluid with viscoelastic fractional foundation is investigated, where the pipe is fixed at the beginning while the pipe end is constrained with two lateral and rotational springs.

Journal ArticleDOI
TL;DR: An autoregressive model is proposed which is able to describe the dynamic evolution of the power system inertia and is modeled as the sum of a periodic component and a noise stochastic process distributed according a non-Gaussian model.
Abstract: Large-scale deployment of renewable energy sources in power systems is basically motivated by two universally recognized challenges: the need to reduce as far as possible the environmental impact of the massive increase of energy request and the dependency on fossil-fuel. Renewable energy sources are interfaced to the network by means of interfacing power converters which inherently exhibit zero inertia differently from the conventional synchronous generators. This matter jointly to the high level of time variability of the renewable resources involve dramatically frequency changes, recurrent frequency oscillations and high variability of frequency profile in general. The need of a fast estimation of time variability of the power system inertia arises at the aim of predicting critical conditions. Based on the analysis of some actual data of the Italian Transmission Network, in this paper the authors propose an autoregressive model which is able to describe the dynamic evolution of the power system inertia. More specifically, the inertia is modeled as the sum of a periodic component and a noise stochastic process distributed according a non-Gaussian model. The numerical results reported in the last part of the paper, demonstrating the efficiency and precision of estimation of inertia, allow justifying the assumptions of the above modeling.

Journal ArticleDOI
TL;DR: In this paper, the authors present results from an experiment designed to better understand the mechanism by which ocean currents and winds control flotsam drift, and explain the differences in the trajectories described by the special drifters as a result of their inertia, primarily buoyancy.
Abstract: We present results from an experiment designed to better understand the mechanism by which ocean currents and winds control flotsam drift. The experiment consisted of deploying in the Florida Current and subsequent satellite tracking of specially designed drifting buoys of various sizes, buoyancies, and shapes. We explain the differences in the trajectories described by the special drifters as a result of their inertia, primarily buoyancy, which constrains the ability of the drifters to adapt their velocities to instantaneous changes in the ocean current and wind that define the carrying flow field. Our explanation of the observed behavior follows from the application of a recently proposed Maxey–Riley theory for the motion of finite-sized particles floating on the ocean surface. The nature of the carrying flow and the domain of validity of the theory are clarified, and a closure proposal is made to fully determine its parameters in terms of the carrying fluid system properties and inertial particle characteristics.

Journal ArticleDOI
26 Feb 2020
TL;DR: It is demonstrated that a quadrotor's tilt, angular velocity, linear velocity and the parameters shown in Table II may be estimated using only an inertial measurement unit (IMU) and motor speed feedback for sensing.
Abstract: In this letter, we demonstrate that a quadrotor's tilt, angular velocity, linear velocity and the parameters shown in Table II may be estimated using only an inertial measurement unit (IMU) and motor speed feedback for sensing. Motor speed commands are used to drive the process model and the motor speed and IMU measurements are used in the measurement model of an unscented Kalman filter (UKF) containing 32 states, 14 of which are constant parameters. We analytically show the observability of this system. Furthermore, we demonstrate through experiments that a blade flapping moment term is not only significant, but necessary to include in the rotation dynamics to get a sensible moment of inertia estimate. We also model the motor torque as a function of the angular acceleration and velocity of the motors in order to obtain a more accurate moment of inertia estimate.

Journal ArticleDOI
TL;DR: This paper investigated how do operating point, line-side and machine-side converter, phase-locked loop and pitch angle control impact the inertial response of the total power controlled type III WECS (DFIG) which is one of the most common wind turbine topologies used today.

Journal ArticleDOI
TL;DR: In this paper, the authors considered the effect of convective fluid inertia and turbulent fluid-velocity gradients on the particle orientation and showed that the fluid-inertia torque prevails in high Reynolds number flows.
Abstract: How non-spherical particles orient as they settle in a flow has important practical implications in a number of scientific and engineering problems. In a quiescent fluid, a slowly settling particle orients so that it settles with its broad side first. This is an effect of the torque due to convective inertia of the fluid that is set in motion by the settling particle, which maximises the drag experienced by the particle. Turbulent fluid-velocity gradients, on the other hand, tend to randomise the particle orientation. Recently the settling of non-spherical particles in turbulence was analysed neglecting the effect of convective fluid inertia, but taking into account the effect of the turbulent fluid-velocity gradients on the particle orientation. These studies reached the opposite conclusion, namely that the particle tends to settle with its narrow edge first, therefore minimising the drag on the particle. Here, we consider both effects, the convective inertial torque as well as the torque due to fluctuating fluid-velocity gradients. We ask under which circumstances either one or the other dominates. To this end we estimate the ratio of the magnitudes of the two torques. Our estimates suggest that the fluid-inertia torque prevails in high-Reynolds-number flows. In this case non-spherical particles tend to settle with orientations maximising drag. But when the Reynolds number is small, then the torque due to fluid-velocity gradients may dominate, causing the particle to settle with its narrow edge first, minimising the drag.

Journal ArticleDOI
TL;DR: The analysis shows that, voltage-dependent loads coupled with electric spring (ES) technology can be operated as smart loads (SL) within the +/−5% tolerance of the ac mains voltage and offer virtual inertia.
Abstract: The inertia of future power systems is expected to decrease with increasing penetration of renewable energy resources. Sufficient inertia is required to avoid large fluctuations in grid frequency and also limit the excessive rate of change of frequency (RoCoF). Unlike many previous works focusing on virtual inertia on the power supply side, this paper studies and quantifies potential virtual inertia from the load side. The analysis shows that, voltage-dependent loads coupled with electric spring (ES) technology can be operated as smart loads (SL) within the +/−5% tolerance of the ac mains voltage and offer virtual inertia. Following the U.K. National Grid frequency requirements, it is shown that the ES based SL can provide virtual inertia up to an inertia coefficient of $H_{SL}=2.5$ s (when $n_{p}=2$ ) with respect to its load power rating. The effectiveness of such virtual inertia extraction from SL has been verified by the simulation study on a CIGRE benchmark microgrid with high-resolution domestic demand model. The value of $H_{SL}$ is shown to be around 1.3 s during the most part of the day and can increase the overall system inertia coefficient by 0.53 s if all the domestic loads are transformed into the proposed smart loads.

Journal ArticleDOI
TL;DR: A formulation of system strength and inertia constrained generator dispatch to reassure NEM operational security in light of emerging high renewable penetration is proposed.
Abstract: System strength and inertia inherently provided by synchronous generators (SGs) empower a power system to ride through voltage and frequency disturbances. The requirements of system strength and inertia were not enforced in the National Electricity Market (NEM) of Australia since SGs dominated the generation fleet in the past. However, the increasing wind and solar generation continuously displaces SGs and consequently reduces system strength and inertia in the NEM. This paper proposes a formulation of system strength and inertia constrained generator dispatch to reassure NEM operational security in light of emerging high renewable penetration. A fault current iterative solver is developed to evaluate system strength, in which the current limitation and voltage control logic of inverter-based generators, and the fault current contribution from VAR compensators are properly modelled in the phasor domain. The system strength contribution factor of an SG is defined to linearize system strength constraint for unit commitment (UC). System and sub-network inertia constraints are also formulated for the UC to limit the rate of change of frequency (RoCoF) in the event of generator/interconnector trip. The proposed generator dispatch formulation can fully meet system strength and inertia requirements in the NEM.

Journal ArticleDOI
TL;DR: This paper calculates analytically the effect of finite translational and rotational particles' inertia on the diffusion of a system of noninteracting spherical active Brownian particles and finds that their sum becomes asymptotically sensitive to the square root of its rotational inertia.
Abstract: It has been discovered that active matter generates novel physical quantities such as the swim pressure. This quantity arises from the exchange of extra momentum between active particles and the boundaries of the system. Given its origin, this quantity can exist at different scales; hence microorganisms and larger organisms like fish or birds generate their own swim pressure. For larger organisms or for high swimming speeds, inertia cannot necessarily be neglected; hence in this paper, we start by calculating analytically the effect of finite translational and rotational particles' inertia on the diffusion of a system of noninteracting spherical active Brownian particles. From this analysis, an enhanced diffusion coefficient due to rotational inertia is obtained, and an alternative effective persistence length and an alternative reorientation time, both sensitive to rotational inertia, are also identified. Afterwards, and to see the implications of finite inertia on bulk properties, the pressure of this system is elucidated by calculating its respective swim and Reynolds pressures. It is found that their sum becomes asymptotically sensitive to the square root of its rotational inertia. To validate our analytical results, Langevin dynamics simulations are also performed showing an excellent agreement between our theoretical predictions and the numerical results.

Journal ArticleDOI
TL;DR: This paper proposes a fast-responding energy storage system such as supercapacitor can mimic inertial responses through some specified control algorithm that can overcome the low inertia problem in dc microgrids.
Abstract: In dc microgrids (dc MGs), the dc link capacitor is very small to provide the inherent inertial. As a result, large voltage deviations occur during load changes or uncertain fluctuations from the fluctuated power resources. This leads to degradation of voltage quality. To overcome the low inertia problem, this paper proposes a fast-responding energy storage system such as supercapacitor can mimic inertial responses through some specified control algorithm. A bidirectional dc–dc converter is used for interfacing supercapacitor energy storage to a dc MG. The proposed control scheme is composed of a virtual capacitor and a virtual conductance. It is implemented in the inner loop controls, i.e. current loop control to be fast enough emulating inertia and damping concept. In order to study the stability of dc MG, a comprehensive small-signal model is derived and then, an acceptable range of inertia response parameters is determined by using the system's root locus analysis. Performance of the proposed control structure is demonstrated through numerical simulations.

Journal ArticleDOI
TL;DR: A novel methodology to automatically assess the power system inertial constant using an autoregressive moving average exogenous input (ARMAX) model and demonstrating it using power system disturbance responses measured by a Wide-Area Measurement System (WAMS).

Posted Content
28 Aug 2020
TL;DR: In this article, the authors provide an overview and classification of inertia estimation methods, considering the time horizon the methods are applicable to, i.e., offline post mortem, online real time and forecasting methods, and the scope of the inertia estimation, e.g., system-wide, regional, generation, demand, individual resource.
Abstract: Accurate inertia estimates and forecasts are crucial to support the system operation in future low-inertia power systems. A large literature on inertia estimation methods is available. This paper aims to provide an overview and classification of inertia estimation methods. The classification considers the time horizon the methods are applicable to, i.e., offline post mortem, online real time and forecasting methods, and the scope of the inertia estimation, e.g., system-wide, regional, generation, demand, individual resource. Shortcomings of the existing inertia estimation methods have been identified and suggestions for future work have been made.

Journal ArticleDOI
TL;DR: The development and validation of artificial neural network (ANN)-based tools, utilizing the power system variables measured by phasor measurement units through wide-area measurements systems, for estimation/forecasting of power system inertia with high penetration of wind farms are presented.
Abstract: Increased penetration of power electronics interfaced renewable energy sources-based generation, for instance, wind farms, that displaces much of the conventional synchronous generation, has a profound effect on the inertia of modern/future power system networks. This article presents the development and validation of artificial neural network (ANN)-based tools, utilizing the power system variables measured by phasor measurement units through wide-area measurements systems, for estimation/forecasting of power system inertia with high penetration of wind farms. The development stage involves the correlation analysis to identify the best power system variables that can be nominated as inputs, and the training of the proposed inertia forecasting tools with the best-nominated inputs that are highly correlated with the power system inertia. Whereas, in the validation stage, the functionality of the trained ANN-based inertia forecasting tools have been validated using the hardware-in-the-loop testing facility developed at the University of Manchester. The development and validation procedures of the proposed inertia forecasting tools have been demonstrated on the IEEE 9-bus modified test system. The validation results revealed the effectiveness of the proposed inertia forecasting tools in estimating the inertia of modern/future power system networks with high penetration of wind farms.