Showing papers on "Inertia published in 2019"
TL;DR: A comprehensive review of inertia enhancement methods covering both proven techniques and emerging ones and the effect of inertia on frequency control is presented and it is concluded that advances in semiconductors and control promise to make power electronics an enabling technology for inertia control in future power systems.
Abstract: Inertia plays a vital role in maintaining the frequency stability of power systems. However, the increase of power electronics-based renewable generation can dramatically reduce the inertia levels of modern power systems. This issue has already challenged the control and stability of small-scale power systems. It will soon be faced by larger power systems as the trend of large-scale renewable integration continues. In view of the urgent demand for addressing the inertia concern, this paper presents a comprehensive review of inertia enhancement methods covering both proven techniques and emerging ones and also studies the effect of inertia on frequency control. Among those proven techniques, the inertia emulation by wind turbines has successfully demonstrated its effectiveness and will receive widespread adoptions. For the emerging techniques, the virtual inertia generated by the dc-link capacitors of power converters has a great potential due to its low cost. The same concept of inertia emulation can also be applied to ultracapacitors. In addition, batteries will serve as an alternative inertia supplier, and the relevant technical challenges as well as the solutions are discussed in this paper. In future power systems where most of the generators and loads are connected via power electronics, virtual synchronous machines will gradually take over the responsibility of inertia support. In general, it is concluded that advances in semiconductors and control promise to make power electronics an enabling technology for inertia control in future power systems.
261 citations
TL;DR: This paper reviews the inertia concept in terms of values and their evolution in the last decades, as well as the damping factor values.
Abstract: Traditionally, inertia in power systems has been determined by considering all the rotating masses directly connected to the grid. During the last decade, the integration of renewable energy sources, mainly photovoltaic installations and wind power plants, has led to a significant dynamic characteristic change in power systems. This change is mainly due to the fact that most renewables have power electronics at the grid interface. The overall impact on stability and reliability analysis of power systems is very significant. The power systems become more dynamic and require a new set of strategies modifying traditional generation control algorithms. Indeed, renewable generation units are decoupled from the grid by electronic converters, decreasing the overall inertia of the grid. ‘Hidden inertia’, ‘synthetic inertia’ or ‘virtual inertia’ are terms currently used to represent artificial inertia created by converter control of the renewable sources. Alternative spinning reserves are then needed in the new power system with high penetration renewables, where the lack of rotating masses directly connected to the grid must be emulated to maintain an acceptable power system reliability. This paper reviews the inertia concept in terms of values and their evolution in the last decades, as well as the damping factor values. A comparison of the rotational grid inertia for traditional and current averaged generation mix scenarios is also carried out. In addition, an extensive discussion on wind and photovoltaic power plants and their contributions to inertia in terms of frequency control strategies is included in the paper.
241 citations
TL;DR: In this paper, an optimization problem is formulated to optimize the parameters and location of these devices in a power system to increase its resilience, and a case study based on a high-fidelity model of the South-East Australian system is used to illustrate the effectiveness of such devices.
Abstract: The electric power system is witnessing a shift in the technology of generation. Conventional thermal generation based on synchronous machines is gradually being replaced by power electronics interfaced renewable generation. This new mode of generation, however, lacks the natural inertia and governor damping, which are quintessential features of synchronous machines. The loss of these features results in increasing frequency excursions and, ultimately, system instability. Among the numerous studies on mitigating these undesirable effects, the main approach involves virtual inertia (VI) emulation to mimic the behavior of synchronous machines. In this paper, explicit models of grid-following and grid-forming VI devices are developed for inertia emulation and fast frequency response in low-inertia systems. An optimization problem is formulated to optimize the parameters and location of these devices in a power system to increase its resilience. Finally, a case study based on a high-fidelity model of the South-East Australian system is used to illustrate the effectiveness of such devices.
202 citations
TL;DR: A novel design and analysis of virtual inertia control to imitate damping and inertia properties simultaneously to the microgrid, enhancing frequency performance and stability and the efficiency and robustness are compared with the conventional inertia control.
Abstract: Virtual inertia control is considered as an important part of microgrids with high renewable penetration. Virtual inertia emulation based on the derivative of frequency is one of the effective methods for improving system inertia and maintaining frequency stability. However, in this method, the ability to provide virtual damping is usually neglected in its design, and hence, its performance might be insufficient in the system with low damping. Confronted with this issue, this paper proposes a novel design and analysis of virtual inertia control to imitate damping and inertia properties simultaneously to the microgrid, enhancing frequency performance and stability. The proposed virtual inertia control uses the derivative technique to calculate the derivative of frequency for virtual inertia emulation. Trajectory sensitivities have been performed to analyze the dynamic impacts of the virtual inertia and virtual damping variables over the system performance. Time-domain simulations are also presented to evaluate the efficiency of the virtual damping and virtual inertia in enhancing system frequency stability. Finally, the efficiency and robustness of the proposed control technique are compared with the conventional inertia control under a wide range of system operation, including the decrease in system damping and inertia and high integrations of load variation and renewable energy.
133 citations
TL;DR: The comparative results show that the combination of SC with AVR hardware-in-the-loop test and SI offers a better improvement not only on frequency stability but also on the system synchronism under various operating conditions.
Abstract: Inertia reduction due to high-level penetration of converter interfaced components may result in frequency stability issues This paper proposes and analyzes different strategies using synchronous condenser (SC), synthetic inertia (SI) of wind power plant, and their combination to enhance the frequency stability of low-inertia systems under various scenarios and wind conditions Furthermore, one of the SC models includes hardware of automatic voltage regulator (AVR) for better representation of the reality is implemented The simplified Western Danish power system simulated in real-time digital simulator is used as a test system of low inertia to demonstrate the effectiveness of the strategies The comparative results show that the combination of SC with AVR hardware-in-the-loop test and SI offers a better improvement not only on frequency stability (rate of change of frequency and frequency deviation) but also on the system synchronism under various operating conditions
128 citations
TL;DR: It is shown that self-alignment, taking the form of a torque coupling the particle orientation and velocity, is responsible for the emergence of this second dynamical state for which the particle condensates at a finite distance from the trap center.
Abstract: The dynamics of an active walker in a harmonic potential is studied experimentally, numerically, and theoretically. At odds with usual models of self-propelled particles, we identify two dynamical states for which the particle condensates at a finite distance from the trap center. In the first state, also found in other systems, the particle points radially outward from the trap, while diffusing along the azimuthal direction. In the second state, the particle performs circular orbits around the center of the trap. We show that self-alignment, taking the form of a torque coupling the particle orientation and velocity, is responsible for the emergence of this second dynamical state. The transition between the two states is controlled by the persistence of the particle orientation. At low inertia, the transition is continuous. For large inertia, the transition is discontinuous and a coexistence regime with intermittent dynamics develops. The two states survive in the overdamped limit or when the particle is confined by a curved hard wall.
123 citations
TL;DR: A self-adaptive virtual inertia control system using fuzzy logic for ensuring stable frequency stabilization, which is required for successful microgrid operation in the presence of high RESs penetration, and shows remarkable performance in transient response improvement and fast damping of oscillations, preserving robustness of operation.
Abstract: Maintaining frequency stability of low inertia microgrids with high penetration of renewable energy sources (RESs) is a critical challenge. Solving this challenge, the inertia of microgrids would be enhanced by virtual inertia control-based energy storage systems. However, in such systems, the virtual inertia constant is fixed and selection of its value will significantly affect frequency stability of microgrids under different penetration levels of RESs. Higher frequency oscillations may occur due to the fixed virtual inertia constant or unsuitable selection of its value. To overcome such a problem and provide adaptive inertia control, this paper proposes a self-adaptive virtual inertia control system using fuzzy logic for ensuring stable frequency stabilization, which is required for successful microgrid operation in the presence of high RESs penetration. In this concept, the virtual inertia constant is automatically adjusted based on input signals of real power injection of RESs and system frequency deviations, avoiding unsuitable selection and delivering rapid inertia response. To verify the efficiency of the proposed control method, the contrastive simulation results are compared with the conventional method for serious load disturbances and various rates of RESs penetration. The proposed control method shows remarkable performance in transient response improvement and fast damping of oscillations, preserving robustness of operation.
114 citations
TL;DR: A robust virtual inertia control for a low-inertia microgrid to minimize the undesirable frequency measurement effects, improving the microgrid frequency stability and compared to the conventional and optimum proportional-integral (PI)-based inertia control.
Abstract: Virtual inertia emulation could be regarded as an inevitable component of microgrids with renewable energy, enhancing microgrid inertia and damping properties. In applying this control technique, a phase-locked loop (PLL) is necessary to obtain the estimation of the system frequency data. However, the employment of PLL could cause larger frequency oscillation to the microgrid due to its dynamics. This issue would be exacerbated in a low-inertia microgrid driven by high renewable penetration, severely deteriorating the frequency stability. Thus, the effect of PLL with measurement delay is a critical issue in utilizing the virtual inertia control. To overcome such problem, this paper proposes a robust virtual inertia control for a low-inertia microgrid to minimize the undesirable frequency measurement effects, improving the microgrid frequency stability. The robust H
∞
control design using a linear fractional transformation (LFT) technique is used to develop the virtual inertia control loop, considering the dynamics of PLL with measurement delay and the uncertainties of system inertia and damping. The efficacy of the proposed H
∞
control method is compared to the conventional and optimum proportional-integral (PI)based inertia control. The results show that the H
∞
-based robust virtual inertia control is superior to both conventional virtual inertia control and optimum PI-based virtual inertia control against a wide range of microgrid operating conditions, disturbances, and parametric uncertainties.
107 citations
TL;DR: A modified virtual inertia control is proposed to mitigate the differential effect, and thus, alleviating the coupling effect to a great extent in stabilizing three-phase grid-connected power converters for inertia emulation even when connected to the weak grid.
Abstract: The continuous increasing share of power-converter-based renewable energies weakens the power system inertia. The lack of inertia becomes a main challenge to small-scale modern power systems in terms of control and stability. To alleviate adverse effects from inertia reductions, e.g., undesirable load shedding and cascading failures, three-phase grid-connected power converters should provide virtual inertia upon system demands. This can be achieved by directly linking the grid frequency and voltage references of dc-link capacitors/ultracapacitors. This paper reveals that the virtual inertia control may possibly induce instabilities to the power converters under weak grid conditions, which is caused by the coupling between the d - and q -axes as well as the inherent differential operator introduced by the virtual inertia control. To tackle this instability issue, this paper proposes a modified virtual inertia control to mitigate the differential effect, and thus, alleviating the coupling effect to a great extent. Experimental verifications are provided, which demonstrate the effectiveness of the proposed control in stabilizing three-phase grid-connected power converters for inertia emulation even when connected to the weak grid.
105 citations
TL;DR: This paper presents a frequency derivative-based inertia enhancement method for battery storage systems that achieves inertia emulation by proportionally linking the time derivative of the grid frequency and active power references of power converters.
Abstract: Renewable energy sources (RESs) have been extensively employed to replace fossil fuels for reducing carbon footprints. Since RESs are normally coupled to the power grid by fast-response power converters without providing any inertia, the power system inertia generated by synchronous generators continues to decrease, making modern power systems sensitive to frequency events. As a result, undesirable load-shedding, cascading failures, or even large-scale blackouts may occur under severe frequency events. To address the lack of inertia concern, this paper presents a frequency derivative-based inertia enhancement method for battery storage systems. Specifically, the method achieves inertia emulation by proportionally linking the time derivative of the grid frequency and active power references of power converters. The main contribution is to use a frequency-locked-loop to accurately estimate the frequency derivative signal, which avoids the high frequency noises introduced by differential operators. Simulation and experimental results are finally presented to validate the effectiveness of the proposed method.
103 citations
TL;DR: In this article, a human body inspired anti-vibration structure (HBIAVS) for exploring its vibration isolation potential is investigated, which consists of an X-shaped supporting structure to simulate legs of human body and a rotational unit with mass to mimic rotational motion of arms and upper body during human walking.
TL;DR: 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.
Abstract: Active particles which are self-propelled by converting energy into mechanical motion represent an expanding research realm in physics and chemistry. For micron-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 which include inertia. In this perspective article recent developments of active particles with inertia ("microflyers") are summarized both for single particle properties and for collective effects of many particles. There 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 non-inertial frames, and the influence of inertia on motility-induced phase separation. Possible future developments and perspectives are also proposed and discussed.
TL;DR: An adaptive virtual inertia control strategy based on an improved bang-bang control strategy for a micro-grid that can make full use of the variability of virtual inertia to reduce dynamic frequency deviation is presented.
Abstract: With the increasing capacity of new energy in the power system, new energy cannot provide support for the system frequency directly. This characteristic of new energy affects the frequency stability of the power system. Therefore the control strategy of a virtual synchronous generator (VSG) is proposed to improve the frequency stability of the system. An adaptive virtual inertia control strategy based on an improved bang-bang control strategy for a micro-grid is presented. On one hand, it can make full use of the variability of virtual inertia to reduce dynamic frequency deviation. On the other hand, the steady-state interval of frequency and the steady-state inertia are set to improve the system frequency stability. Then the stability analysis of the value range of the virtual inertia is performed by the small signal model of the VSG for the micro-grid. Meanwhile, the ranges of virtual inertia and steady-state inertia are determined. Finally, Matlab/Simulink is applied to accomplish simulation experiments to compare various virtual inertia control strategies. The results indicate the effectiveness of the proposed strategy.
TL;DR: In this article, a modified finite element method (FEM) was used to analyze the transverse vibrations of a Timoshenko beam, made of functionally graded materials (FGMs), on a two-parameter foundation and subjected to a variable-velocity moving mass.
TL;DR: In this article, an online inertia estimation algorithm is proposed for transmission system operators to be able to monitor the system inertia in real time in a highly deregulated and uncertain environment, and the estimator is derived using the recently proposed dynamic regressor and mixing procedure.
Abstract: The increasing penetration of power-electronic-interfaced devices is expected to have a significant effect on the overall system inertia and a crucial impact on the system dynamics. In future, the reduction of inertia will have drastic consequences on protection and real-time control and will play a crucial role in the system operation. Therefore, in a highly deregulated and uncertain environment, it is necessary for transmission system operators to be able to monitor the system inertia in real time. We address this problem by developing and validating an online inertia estimation algorithm. The estimator is derived using the recently proposed dynamic regressor and mixing procedure. The performance of the estimator is demonstrated via several test cases using the 1013-machine ENTSO-E dynamic model.
TL;DR: In this paper, the authors examined the nonlinear stability and free vibration features of GPL-GPLRPC rectangular plates under compressive in-plane mechanical loads in pre/post buckling regimes.
TL;DR: A wave-vegetation model is implemented in an open-source code, SWASH (Simulating WAves till SHore). The governing equations are the nonlinear shallow water equations, including non-hydrostatic pressure as mentioned in this paper.
TL;DR: In this article, the frequency probability density function (PDF) for a given power system was analyzed to uncover key system parameters influencing frequency deviations, and it was shown that system inertia has little effect on the frequency PDF, making virtual inertia services insufficient for keeping frequency close to nominal under ambient load fluctuations.
Abstract: Power system inertia is falling as more energy is supplied by renewable generators, and there are concerns about the frequency controls required to guarantee satisfactory system performance. The majority of research into the negative effect of low inertia has focused on poor dynamic response following major disturbances, when the transient frequency dip can become unacceptable. However, another important practical concern—keeping average frequency deviations within acceptable limits—was mainly out of the sight of the research community. In this manuscript, we present a method for finding the frequency probability density function (PDF) for a given power system. We pass from an initial stochastic dynamic model to deterministic equations for the frequency PDF, which are analyzed to uncover key system parameters influencing frequency deviations. We show that system inertia has little effect on the frequency PDF, making virtual inertia services insufficient for keeping frequency close to nominal under ambient load fluctuations. We establish that aggregate system droop and deadband width are the only parameters that have major influence on the average frequency deviations, suggesting that energy storage might be an excellent solution for tight frequency regulation. We also show that changing the governor deadband width does not significantly affect generator movement.
TL;DR: This model of the high voltage synchronous grid of continental Europe shows that, beyond absorbing frequency disturbances following nearby faults, inertia also mitigates frequency disturbances from distant power losses, provided both the fault and the inertia are located on the support of the slowest modes of the grid Laplacian.
Abstract: Conventional generators in power grids are steadily substituted with new renewable sources of electric power. The latter are connected to the grid via inverters and as such have little, if any rotational inertia. The resulting reduction of total inertia raises important issues of power grid stability, especially over short-time scales. With the motivation in mind to investigate how inertia reduction influences the transient dynamics following a fault in a large-scale electric power grid, we have constructed a model of the high voltage synchronous grid of continental Europe. To assess grid stability and resilience against disturbance, we numerically investigate frequency deviations as well as rates of change of frequency (RoCoF) following abrupt power losses. The magnitude of RoCoF’s and frequency deviations strongly depend on the fault location, and we find the largest effects for faults located on the support of the slowest mode—the Fiedler mode—of the network Laplacian matrix. This mode essentially vanishes over Belgium, Eastern France, Western Germany, northern Italy and Switzerland. Buses inside these regions are only weakly affected by faults occuring outside. Conversely, faults inside these regions have only a local effect and disturb only weakly outside buses. Following this observation, we reduce rotational inertia through three different procedures by either (i) reducing inertia on the Fiedler mode, (ii) reducing inertia homogeneously and (iii) reducing inertia outside the Fiedler mode. We find that procedure (iii) has little effect on disturbance propagation, while procedure (i) leads to the strongest increase of RoCoF and frequency deviations. This shows that, beyond absorbing frequency disturbances following nearby faults, inertia also mitigates frequency disturbances from distant power losses, provided both the fault and the inertia are located on the support of the slowest modes of the grid Laplacian. These results for our model of the European transmission grid are corroborated by numerical investigations on the ERCOT transmission grid.
TL;DR: In this article, the authors introduce the mechanisms and underlying physics in inertial microfluidic systems with specific focuses on inertial particle migration and secondary flow, and outline the opportunities provided by the field, along with an outlook on the field.
Abstract: In 1961, Segre and Silberberg first reported the tubular pinch effect and numerous theoretical studies were subsequently published to explain the inertial particle migration phenomenon. Presently, as fluid mechanics meets micro- and nanotechnology, theoretical studies on intrinsic particle migration and flow phenomena associated with inertia are being experimentally tested and validated. This collective study on the fluid-particle-structure phenomena in microchannels involving fluid inertia is called, “inertial microfluidics”. Beyond theoretical studies, now inertial microfluidics has been gaining much attention from various research fields ranging from biomedicine to industry. Despite the positive contributions, there is still a lack of clear understanding of intrinsic inertial effects in microchannels. Therefore, this minireview introduces the mechanisms and underlying physics in inertial microfluidic systems with specific focuses on inertial particle migration and secondary flow, and outlines the opportunities provided by inertial microfluidics, along with an outlook on the field.
TL;DR: A new inertial power based perturb and observe method is proposed for wind turbines by considering the energy stored in the turbine inertia, which enables to find the maximum power point accurately.
TL;DR: An effective virtual inertia measure for cyber-physical agents that includes both traditional synchronous generators and actuated ESSs is proposed and derived analytically for the case of general ESS-based control.
Abstract: In this paper, we consider a distributed energy storage system (ESS)-based control paradigm for transient stability of power systems. Utilizing a multi-agent control framework, we propose an effective virtual inertia measure for cyber-physical agents that includes both traditional synchronous generators and actuated ESSs. We derive the effective virtual inertia analytically for the case of general ESS-based control. We further consider the case of parametric feedback linearization control (PFL) as an application and investigate the proposed inertia measures after applying the PFL control. The utility of the proposed inertia measures is studied using the IEEE 68-bus test power system. Numerical results demonstrate the impact of storage limits, control scheme aggressiveness, and delay on the proposed inertia measures during a disturbance in the power system.
TL;DR: A novel method of measuring area inertia is presented, with results of simulation and trials on the SP Energy Networks (Scottishpower) transmission system in south Scotland, and enables new, flexible services for the transition to low inertia power systems.
TL;DR: In this paper, a human body inspired passive vibration isolation system with a special coupled nonlinear inertia design is presented, which can improve the vibration isolation at low frequencies and/or in a broadband frequency range, irrespective of the loading and excitation conditions.
TL;DR: In this paper, an adaptive local iterative filtering decomposition is used to identify the frequency and damping ratio of an electric power system to estimate the inertia of a multi-area interconnected power system.
Abstract: The inertia constant is a key parameter of synchronous grids that are robust to disturbances. This paper presents an inertia estimation method for a multi-area interconnected electric power system. The method utilizes the electromechanical oscillation response measured with a phasor measurement unit. On the basis of the classical swing equation, the mathematical relationships between inertia and electromechanical oscillation parameters (i.e., oscillation frequency and damping ratio of a mode) are determined. The equivalent inertia of the system can be estimated by extracting the frequency and damping ratio of a mode from the observed active power on the tie line in the electromechanical oscillation response. Moreover, the system damping coefficient can be estimated without additional calculation and measurement. The inertia estimation errors caused by the poor extraction of oscillation parameters are reduced by utilizing the advanced parameter identification technology called adaptive local iterative filtering decomposition to identify the frequency and damping ratio of a mode. The accuracy and robustness of the proposed method are verified by using two simulation examples and an actual system.
TL;DR: In this paper, the authors study the variations of the force balance when changing the forcing (Rayleigh number, $Ra$) and the ratio between viscous and magnetic diffusivities (magnetic Prandtl number,$Pm$).
Abstract: Dynamo action in the Earth's outer core is expected to be controlled by a balance between pressure, Coriolis, buoyancy and Lorentz forces, with marginal contributions from inertia and viscous forces. Current numerical simulations of the geodynamo, however, operate at much larger inertia and viscosity because of computational limitations. This casts some doubt on the physical relevance of these models. Our work aims at finding dynamo models in a moderate computational regime which reproduce the leading-order force balance of the Earth. By performing a systematic parameter space survey with Ekman numbers in the range $10^{-6} \leq E \leq 10^{-4}$, we study the variations of the force balance when changing the forcing (Rayleigh number, $Ra$) and the ratio between viscous and magnetic diffusivities (magnetic Prandtl number, $Pm$). For dipole-dominated dynamos, we observe that the force balance is structurally robust throughout the investigated parameter space, exhibiting a quasi-geostrophic (QG) balance (balance between Coriolis and pressure forces) at zeroth order, followed by a first-order MAC balance between the ageostrophic Coriolis, buoyancy and Lorentz forces. At second order this balance is disturbed by contributions from inertia and viscous forces. Dynamos with a different sequence of the forces, where inertia and/or viscosity replace the Lorentz force in the first-order force balance, can only be found close to the onset of dynamo action and in the multipolar regime. Our study illustrates that most classical numerical dynamos are controlled by a QG-MAC balance, while cases where viscosity and inertia play a dominant role are the exception rather than the norm.
TL;DR: An analysis of power system inertia estimation from frequency excursions is carried out by considering different inertia estimation methodologies, discussing the applicability and coherence of these methodologies under the new supply-side circumstances and including virtual inertia emulation techniques.
Abstract: Nowadays, power system inertia is changing as a consequence of replacing conventional units by renewable energy sources, mainly wind and photovoltaic power plants. This fact affects significantly the grid frequency response under power imbalances. As a result, new frequency control strategies for renewable plants are being developed to emulate the behaviour of conventional power plants under such contingencies. These approaches are usually called `virtual inertia emulation techniques'. In this study, an analysis of power system inertia estimation from frequency excursions is carried out by considering different inertia estimation methodologies, discussing the applicability and coherence of these methodologies under the new supply-side circumstances. The modelled power system involves conventional units and wind power plants including wind frequency control strategies in line with current mix generation scenarios. Results show that all methodologies considered provide an accurate result to estimate the equivalent inertia based on rotational generation units directly connected to the grid. However, significant discrepancies are found when frequency control strategies are included in wind power plants decoupled from the grid. In this way, authors consider that it is necessary to define alternative inertia estimation methodologies by including virtual inertia emulation. Extensive discussion and results are also provided in this study.
TL;DR: Simulations carried out on the IEEE 39-bus system validate the effectiveness and robustness of the proposed approach in the presence of various sources of uncertainties.
Abstract: The real-time center of inertia frequency plays an important role in power system stability analysis and control. This letter proposes a robust approach to identify power system center of inertia frequency with consideration of system uncertainties and synchrophasor measurement quality. A model decoupling strategy is first presented by taking measured generator active power as the swing equation input, whereas remaining the bus frequency as output. This allows deriving the linear discrete-time state-space form, which will be used by the robust Kalman filter for generator rotor speed, angle, and inertia estimation. The robust Kalman filter is mandatory as the measured frequency can change abruptly due to impulsive noise or system sudden changes. Simulations carried out on the IEEE 39-bus system validate the effectiveness and robustness of the proposed approach in the presence of various sources of uncertainties.
TL;DR: A DC-link inertia control is proposed for providing virtual inertia by using the electrostatic energy stored in the DC capacitor, and the key parameters that affect the virtual inertia provided by this control are discussed in detail.
Abstract: A high proportion of wind energy in modern power system requires wind turbines (WTs) to provide frequency regulation services. In this context, this paper proposes a comprehensive coordinated control strategy of permanent magnet synchronous generator (PMSG)-based WT for providing an inertial response and primary control. First, a DC-link inertia control is proposed for providing virtual inertia by using the electrostatic energy stored in the DC capacitor, and the key parameters that affect the virtual inertia provided by this control are discussed in detail. Moreover, in order to provide more virtual inertia, a virtual capacitor control (VCC) strategy is proposed. With the VCC strategy, the rotor-side converter (RSC) can provide a virtual capacitance much larger than the actual DC capacitance and supply fast and transient extra power support by using the WT's rotor kinetic energy, in a similar way with the synchronous generator (SG) inertial response. Power-frequency droop control is adapted to allow WT to provide primary control service by using the WT's rotor kinetic energy. Furthermore, the virtual inertia constant of the proposed strategy is analytically derived. Finally, the simulation results in PSCAD/EMTDC are presented to verify the effectiveness of the proposed control strategy.