Damping Resistance Research Articles

Passivity Enhancement of Grid-Tied Converters by Series LC-Filtered Active Damper

The series LC -filtered active damper can be used for stabilizing a grid converter tied to the nonideal grid. Its operation principle is to mimic a damping resistance at the resonance frequencies appearing in the grid. However, the selection of the damping resistance has not been fully analyzed in the literature. Its effect with parasitic capacitance present in the grid has also usually been ignored, even though it may bring new challenges to the active damper. To address these issues, passivity is applied to study the grid converter stability before the understanding gained is used for formulating a damping resistance selection method. The method formulated can further be improved by admittance shaping so that system stability can always be ensured even when considering grid parasitic capacitance and control imperfection. Experimental results obtained have verified the expectations, and, hence, the suitability of the presented methods for the series LC -filtered active damper.

Компенсация неизохронности в резонаторе с нелинейным сопротивлением потерь

Компенсация неизохронности в резонаторе с нелинейным сопротивлением потерь

Model-Based Active Damping Control for Three-Phase Voltage Source Inverters With LCL Filter

This paper presents a robust model-based active damping control in natural frame for a three-phase voltage source inverter with LCL filter. The presence of the LCL filter complicates the design of the control scheme, particularly when system parameters deviation is considered. The proposed control method is addressed to overcome such difficulties and uses a modified converter model in a state observer. In this proposal, the converter model is modified by introducing a virtual damping resistor. Then, a Kalman filter makes use of this model to estimate the system state-space variables. Although the state estimates do not obviously match the real world system variables, they permit designing three-current sliding-mode controllers that provide the following features to the closed loop system: 1) robust and active damping capability like in the case of using a physical damping resistor; 2) robustness because the control specifications are met independently of variation in the system parameters; 3) noise immunity due to the application of the Kalman filter; and 4) power loss minimization because the system losses caused by the physical damping resistor are avoided. An interesting side effect of the proposed control scheme is that the sliding surfaces for each controller are independent. This decoupling property for the three controllers allows using a fixed switching frequency algorithm that ensures perfect current control. To complete the control scheme, a theoretical stability analysis is developed. Finally, selected experimental results validate the proposed control strategy and permit illustrating all its appealing features.

Design and Analysis of Second Order Passive Filters for Grid Connected Inverter with Series and Parallel Damping Resistors

Background/Objectives: Grid connected inverters are widely used to integrate renewable sources into the grid. The suitable power quality is required which can be either achieved using active or passive filters. This paper focuses on second order passive filters such as inductor capacitor (LC) and LC inductor (LCL) which can be used to attenuate harmonics for grid connect inverters. Methods/Statistical Analysis: To overcome the resonance of LCL filters passive damping 6-8 or active damping can be used. Active power filters are more expensive because of sensors and control systems additional cost. Passive damping strategies due to simple circuit and low cost are more favored. A LCL filter equipped with series or parallel resistor with a capacitor forms a LCL filter with damped resistor Addition of resistor to filter circuit will cause an increase in power losses. The peak resonance of LCL filter depends upon the value of resistor so select a value of resistor which decline peak resonance of filter. Findings: At resonance frequency they have some issues related to stability. LCL filter can be equipped with damping resistor but there are some power loss and introduction of voltage, current harmonic. Mathematical characteristics of passive filters such as LC, LCL, LCL with series resistor and LCL with parallel resistors are discussed in terms of effectiveness and stability in this paper. Application/Improvements: It is very useful for industrial application and power electronic converter.

Experimental characterisation of cork agglomerate core sandwich panels for wall assemblies in buildings

In recent times, the construction market has seen a very significant increase in the demand of prefabricated solutions of nonstructural elements, such as sandwich panels for buildings walls. Due to the inherent low weight, good mechanical behaviour, ease of assembly and cost-effectiveness, these types of wall assemblies are especially competitive in construction of single-family houses or one unit dwelling structures.However, the low fire resistance of many of these solutions, such as sandwich panels with expanded polystyrene core or polyethylene terephthalate foam core, precludes their use in buildings with more than one floor. The substandard fire resistance is generally due to the fact that the constituent materials are combustible or, at least, their properties are extremely sensible when subjected to high temperatures or flame.Given the isolation properties, good mechanical damping and fire resistance, cork agglomerate can be used as the core material for sandwich panels. However, this material is heavier than the other materials commonly used as core for sandwich panels. In order to deal with this drawback, it is necessary to choose a material for the panel facings that could fulfil the mechanical requirements and the condition not excessively increase the panel weight. The use of a glass fibre reinforced polymer seemed a suitable solution for the facing component. Therefore, the proposed wall assembly solution consists in a sandwich panel with cork agglomerate core and glass fibre reinforced polymer facings.The scope of this work was the assessment of the feasibility of a new configuration of vertical (wall) sandwich panels that could, not only be a cost effective solution for prefabricated construction, but also provide good mechanical performance and fire resistance. This sandwich wall panel configuration was tested for characterisation of its mechanical behaviour, resistance to impact and to fire. The results of the experimental campaign carried out are presented in this manuscript along with some conclusions about the suitability of this solution as sandwich wall panel for buildings façades.

Study on EMTP Simulation Applying Dual Reactor for Prevention of the Ferro-resonance and VT Burnout in Substation System

Abstract When the line and switchgear of the substation system are disconnected, ferro-resonance can occur. This happens even if the capacitive reactance and inductive reactance are not equal, which are not common resonance conditions. Resonance conditions vary depending on the busbar configuration environment. Although the damping resistance method applying the existing saturable reactor to cope with ferro-resonance has been su ccessfully applied on site, th ere can be loss of normal function during long-term operat ion. The reason is because the rise in the operating frequency of saturable reactors means the saturation number is increased. Therefore, it can no longer function as saturable reactor since the resistor having inadequate capacity is burned out. To address this problem, in this paper, an EMTP-based simulation test was performed by designing and applying a dual reactor method, which adds an extended divergence reactor to the 1st side of the VT. The test result confirms that when the divergence reactor is inserted, the voltage and current values obtained at the 1st side and 2nd side of the VT as well as current values of divergence reactor part were stabilized from the transient phenomena and return to normal values. When compared with existing measures, although this method is similar in adding having a reactor added to a system regarding ferro-resonance, it has the advantage of being able to prevent ferro-resonance in advance since the reactor is added before the system is s aturated. In addition, because it does not use damping resistance, it can extend the equ ipment life and stabilize its operation. Therefore, there are a lot of differences in terms of its operating characteristics and achivement of goal between the conventional method and new divergence reactor method.

Transplacental Administration of Rosiglitazone Attenuates Hyperoxic Lung Injury in a Preterm Rabbit Model

Introduction: Continuous improvements in perinatal care have allowed the survival of increasingly more prematurely born infants. The establishment of respiration in an extremely immature yet still developing lung results in chronic lung injury with significant mortality and morbidity. We experimentally evaluated a novel medical strategy to prevent hyperoxia-induced lung injury by prenatal rosiglitazone. Materials and Methods: Pregnant rabbits were injected with saline or rosiglitazone (3 mg/kg) 48 and 24 h prior to preterm delivery at 28 days of gestation (term = 31 days). The pups were held in normoxia (21% O₂) or hyperoxia (>95% O₂), and assessment was done at three different time points (1 h, 24 h and 7 days). Results: The administration of rosiglitazone resulted in a significant decrease in tissue damping (resistance) on day 7. Furthermore, significantly increased expression of vascular endothelial growth factor, fetal liver kinase 1 and surfactant protein B immediately after delivery was noted by immunohistochemistery. On day 7, there was a more mature lung parenchymal architecture in rosiglitazone-exposed pups. Discussion: In a preterm rabbit model, prenatal maternal administration of rosiglitazone attenuates neonatal hyperoxic lung injury and results in a more mature pulmonary parenchyma.

Inhibition of HMGCoA reductase by simvastatin protects mice from injurious mechanical ventilation.

BackgroundMortality from severe acute respiratory distress syndrome exceeds 40% and there is no available pharmacologic treatment. Mechanical ventilation contributes to lung dysfunction and mortality by causing ventilator-induced lung injury. We explored the utility of simvastatin in a mouse model of severe ventilator-induced lung injury.MethodsMale C57BL6 mice (n = 7/group) were pretreated with simvastatin or saline and received protective (8 mL/kg) or injurious (25 mL/kg) ventilation for four hours. Three doses of simvastatin (20 mg/kg) or saline were injected intraperitoneally on days −2, −1 and 0 of the experiment. Lung mechanics, (respiratory system elastance, tissue damping and airway resistance), were evaluated by forced oscillation technique, while respiratory system compliance was measured with quasi-static pressure-volume curves. A pathologist blinded to treatment allocation scored hematoxylin-eosin-stained lung sections for the presence of lung injury. Pulmonary endothelial dysfunction was ascertained by bronchoalveolar lavage protein content and lung tissue expression of endothelial junctional protein Vascular Endothelial cadherin by immunoblotting. To assess the inflammatory response in the lung, we determined bronchoalveolar lavage fluid total cell content and neutrophil fraction by microscopy and staining in addition to Matrix-Metalloprotease-9 by ELISA. For the systemic response, we obtained plasma levels of Tumor Necrosis Factor-α, Interleukin-6 and Matrix-Metalloprotease-9 by ELISA. Statistical hypothesis testing was undertaken using one-way analysis of variance and Tukey’s post hoc tests.ResultsVentilation with high tidal volume (HVt) resulted in significantly increased lung elastance by 3-fold and decreased lung compliance by 45% compared to low tidal volume (LVt) but simvastatin abrogated lung mechanical alterations of HVt. Histologic lung injury score increased four-fold by HVt but not in simvastatin-pretreated mice. Lavage pleocytosis and neutrophilia were induced by HVt but were significantly attenuated by simvastatin. Microvascular protein permeability increase 20-fold by injurious ventilation but only 4-fold with simvastatin. There was a 3-fold increase in plasma Tumor Necrosis Factor-α, a 7-fold increase in plasma Interleukin-6 and a 20-fold increase in lavage fluid Matrix-Metalloprotease-9 by HVt but simvastatin reduced these levels to control. Lung tissue vascular endothelial cadherin expression was significantly reduced by injurious ventilation but remained preserved by simvastatin.ConclusionHigh-dose simvastatin prevents experimental hyperinflation lung injury by angioprotective and anti-inflammatory effects.

Estimation of Electronic Suppression Circuit Resistance for Protective Relaying Applications

The transient response of instrument transformers affects the performance of high-speed relays, particularly speed and overreach in case of distance protection. Transient response of a capacitive voltage transformer depends on the type of ferro-resonance suppression circuit (FSC), i.e., active, passive, or electronic, provided in the secondary to damp the ferro-resonant oscillations. The objective of this article is not to estimate optimum resistance but to provide a systematic approach instead of the trial-and-error approach to estimate damping resistance for the electronic ferro-resonance suppression circuit used in the: capacitive voltage transformer for protective relaying application. The performance of the numerical distance relay for the: capacitive voltage transformer with estimated damping resistance in the electronic ferro- resonance suppression circuit is tested and validated in real time using a field programmable gate array.

Potential Harmonic Resonance Impacts of PV Inverter Filters on Distribution Systems

This paper presents a clarification study to identify the potential resonance phenomenon between photovoltaic (PV) inverters and the distribution system. LCL and LC filters are widely applied in PV inverters to mitigate high-order harmonic components generated by PV inverters. There is a possibility that these filters will excite harmonic resonance by interacting with the system impedance. The mechanism of this phenomenon is investigated here by mathematical analysis and measurement. The results indicate that the resonance can be attenuated if the damping resistance, such as damping resistor and residential linear loads, is large enough. Alternatively, three sets of field tests are conducted in the laboratory to verify and clarify the potential harmonic resonance and its factors. Furthermore, a full case of an actual North American distribution system with PV installations is also studied. The results indicate that the harmonic resonance caused by the PV filter is almost attenuated and cannot cause serious problems. At the same time, the filter may have some advantages in mitigating harmonics. Finally, to complete this paper, other sustainable energy resources with voltage-source converters (VSCs) are compared.

Systematic Input Filter Design of Matrix Converter by Analytical Estimation of RMS Current Ripple

A filter is required to eliminate the high-frequency switching ripple present in the input current of a matrix converter (MC). Design of such a filter requires an estimation of the higher harmonic components present in the input current. This paper presents a simple closed-form analytical expression for the RMS input current ripple injected by the MC. The expression shows the variation with load power factor and is independent of the output frequency. This is used in a step-by-step procedure to design various input filter components from the specifications of allowable total harmonic distortion in the grid current and distortion in the input voltage. The MC is modeled for the grid frequency component in order to evaluate the design for input power factor and voltage drop across the filter. A damping resistance has been designed ensuring minimum ohmic loss. The analytical estimation of the ripple current and the proposed design procedure have been validated by simulations in MATLAB/Simulink and experiments on a laboratory prototype.

On electrical optimisation using a Duffing-type vibrational energy harvester

There has been much recent interest in the response analysis and optimisation of the linear energy harvester under ambient vibrations. To transfer maximum power to an electrical load in a resonant system, the load resistance should be equal to the sum of the electrical analogue of mechanical damping and internal resistance. However, principally because of the limited bandwidth offered by the linear energy harvester, the potential benefit of nonlinearity has recently been applied to improve the effectiveness of energy harvesting devices. For example, a Duffing-type oscillator can provide a wider bandwidth and greater effectiveness when subject to periodic excitations. The motivating hypothesis has been that the nonlinear Duffing energy harvester can also be optimised to maximise the available electrical power. This paper presents theoretical optimisation and numerical studies under three different conditions with the designed Duffing-type devices. First, the simplest model without any transmission mechanism and optimisation constraints is considered. Second, a device operated under low frequency and large force excitations using a ball screw to convert low-speed linear motion to high-speed rotation is analysed, where the optimum lead and load resistance are derived. Finally, considering the limitation of some dimensions in practical implementation, the constrained optimisation subjected to the maximum displacement of the seismic mass is also shown in this paper.

Grid-Side AC Line Filter Design of a Current Source Rectifier With Analytical Estimation of Input Current Ripple

This paper presents a systematic step-by-step design procedure for the input filter of a current source rectifier (CSR). The design is based on the specifications of allowable ripple in the input voltage of the CSR and high-frequency harmonic components in the grid current. Analytical techniques have been developed to estimate the ripple present in the input current and to model the converter for fundamental or grid frequency. The analysis is done for carrier-based and space-vector modulation of the current source rectifier and the model at grid frequency is used to evaluate the design of the filter for grid power factor, voltage drop across filter, etc. A damping resistance is designed ensuring a minimum power loss. The analysis and design of the input filter have been verified by simulations in MATLAB/Simulink and experimental tests on a laboratory prototype.

Estimation of mechanical properties of soft tissue subjected to dynamic impact

Human soft tissue is highly deformable leading to a difficulty in estimating itsmechanical properties. This paper focuses on the extraction of human tissue dampeningproperties under dynamic impact, which enabled an efficient implementation ofmechanical response of tissue, which is of growing interest and importance inbiomedical research and forensic science. Such properties are not only useful forrealistic surgical simulation, preoperative planning, and robot-assisted medicalprocedures, but also may be useful in deriving impact characteristics necessary tocause contusions for forensics purposes. The estimates of the damping propertiesof human soft tissue was done by using spring and damper system as a model; massdamper-spring (MDS). Spring stiffness is represented by the spring constant K anddashpot damping resistance is represented by the damper constant C. Data werecollected by striking human subjects with a weighted pendulum at different levelsof energy, velocity, and mass. The estimation process involved conditioning the data,such that the modeling process and estimation were feasible, resulting in estimates ofK and C. In conclusion, using impact data collected on living human tissue to estimatethe dampening properties is plausible. The results showed that both the stiffness andthe dampening resistance are highly correlated with the mass of the striking object, itsenergy and velocity. Hence, knowledge of these properties may be used in determiningthe impact parameters required by a striking object, which might be helpful in forensicinvestigation when contusions were induced.

Three-Phase Primary Control for Unbalance Sharing between Distributed Generation Units in a Microgrid

For islanded microgrids, droop-based control concepts have been developed both in single and three-phase variants. The three-phase controllers often assume a balanced network; hence, unbalance sharing and/or mitigation remains a challenging issue. Therefore, in this paper, unbalance is considered in a three-phase islanded microgrid in which the distributed generation (DG) units are operated by the voltage-based droop (VBD) control. For this purpose, the VBD control, which has been developed for single-phase systems, is extended for a three-phase application and an additional control loop is added for unbalance mitigation and sharing. The method is based on an unbalance mitigation scheme by DG units in grid-connected systems, which is altered for usage in grid-forming DG units with droop control. The reaction of the DG units to unbalance is determined by the main parameter of the additional control loop, viz., the distortion damping resistance, Rd. The effect of Rd on the unbalance mitigation is studied in this paper, i.e., dependent on Rd, the DG units can be resistive for unbalance (RU) or they can contribute in the weakest phase (CW). The paper shows that the RU method decreases the line losses in the system and achieves better power equalization between the DG unit’s phases. However, it leads to a larger voltage unbalance near the loads. The CW method leads to a more uneven power between the DG unit’s phases and larger line losses, but a better voltage quality near the load. However, it can negatively affect the stability of the system. In microgrids with multiple DG units, the distortion damping resistance is set such that the unbalanced load can be shared between multiple DG units in an actively controlled manner rather than being determined by the microgrid configuration solely. The unit with the lowest distortion damping resistance provides relatively more of the unbalanced currents.

Investigating different passive methods for enhancement of low voltage ride through capability of Doubly Fed Induction Generator

In recent years with the increasing use of wind generators in power systems, the issue of keeping these generators stable and maintaining their connection to the network in the presence of fault or voltage sag has gained a great importance. In this paper some enhancement methods for the low voltage ride through of Doubly Fed Induction Generator (DFIG), including Crowbar resistance, Rotor series limiter, and Stator damping resistor, are introduced, and then the advantages and disadvantages of each method will be discussed using simulation results. Simulations have been performed by MATLAB/Simulink software.

Stability Analysis of Grid-Connected Inverter With LCL Filter Adopting a Digital Single-Loop Controller With Inherent Damping Characteristic

The stability problem of the grid-connected inverter with LCL filter adopting a digital single-loop controller without extra damping resistance is analyzed. The digital single-loop control based on the grid-side current feedback can attenuate the resonance introduced by LCL filters due to the inherent damping characteristic embedded in the control loop. The stability analysis is performed by means of a Nyquist diagram in the discrete domain and to provide a general design direction for filter and controller. The quantitative relationship of ratios of LCL resonance angular frequency to control frequency and controller parameters on the system stability is investigated. It is derived that the system would obtain preferable stability margin when the ratio is located at a certain range. The theoretical analyses are validated by experimental tests based on a 5-kW single-phase inverter laboratory prototype.

Experimental Identification of Overall Structural Damping of System

The dynamic behaviour of large and complex structures largely depends on damping resistance in the structure. A portion of the structural energy is lost to deformations in material, friction between the contact surfaces, and relative motion within the structure. Often, in an analysis of numerical models, before the dynamic analysis of transient events (transient analysis), the damping resistance is adopted on the basis of recommendations, which implies an error of transient response (introduced by frequencies, logarithmic decrements and maximal amplitudes). Decreasing amortized vibratory movement is dependent on the extent of the structural damping. This paper presents the importance of structural damping in structural analysis and shows the experimental and theoretical procedure for identifying G values of the structural damping coefficient. A model for determining the G coefficient is shown in the example of a real tower crane structure. The experimentally obtained values were then used in the transient numerical FEM analysis, as the basis for adopting the conclusions about the dynamic behaviour of this class of structures (transportation machines). The effect of the external perturbation force of trapezoidal impulse form (lifting and quickly lowering of load) is introduced and the dynamic task, as an example of the use of the G coefficient G, is solved. The experimentally determined damping (theoretically isolated for tall truss structures) can be used in similar transient analyses.

Dual-loop Control Strategy for Grid-connected Inverter with LCL Filter

As to the concrete topology of three-phase LCL type grid-connected inverter with damping resistance, mathematical model was deduced in detail, using method of equivalent transformation to the structure diagram, damping resistance was virtualized, mathematical model under the DQ frame that can realize decoupling control was established, a dual-loop control strategy for grid-connected inverter with LCL filter was proposed, the system stability was analyzed and the design method of controller was given. The proposed method overcame the flaws of loss increase, efficiency reduce and cost increase which were caused by damping resistance in LCL type grid-connected inverter, the system efficiency and power supply quality of the output were improved. Feasibility and effectiveness of the new method were validated by simulation and experimental results.

Dynamic behavior of a single-phase self-excited induction generator using a three-phase machine feeding single-phase dynamic load

This paper is motivated to analyze the transient behavior of a single-phase self-excited induction generator (SEIG) using a three-phase machine due to switching of single-phase dynamic load like induction motors. The generator consists of a three-phase star connected induction machine excited with three-capacitors and a single-phase induction motor (IM) load. The developed dynamic models of the SEIG and the motor are based on stationary reference frame d–q axes theory incorporating the effect of cross-saturation in the magnetic circuit of the machine and the equations of excitation capacitors are described by three-phase abc model. The system suffers from heavy transients during switching of induction motor and becomes unstable. These problems may be due to resonance caused by series capacitors and the inductive motor load. The use of damping resistors across one series capacitor is proposed to damp out the starting transients for the stable operation. The motor can be started up successfully using the damping resistor. The variation of the damping resistance with the increase in load on the motor after successful starting to maintain constant terminal voltage has been presented. The eigenvalue technique is also employed to examine the transient conditions in the studied SEIG-IM system. The simulated and experimental results are presented for both the unsuccessful and successful starting of the motor. These results are in close agreement with each other, which show the effectiveness of the approach.