With the increasing penetration of wind power, stability issues weak AC grid-connected doubly fed induction generator (DFIG)-based turbines during low-voltage ride through (LVRT) cannot be neglected. In order to explore instability mechanism DFIG system grid fault, small signal state-space model is established in this paper. The results modal analysis show that dominant unstable poles are mainly impacted by phase-locked loop (PLL), rotor current control loop, and terminal voltage where PLL...

The voltage-frequency coupled transient stability and risk assessment issues of weak grid-connected large-scale renewable energy plants (REPs) during low voltage ride through (LVRT) have received little attention to date. shape mechanism instability LVRT are investigated in detail by the voltage-vector-triangle graphic (VTG) method utilized this article, which avoids complex mathematical calculations. In addition, margin transmission line's angle (MTVA) is defined article then used...

In this article, the transient synchronization process of grid-connected voltage source converters (VSC) is studied detailly. Firstly, phase-locked loop (PLL)-synchronized VSC modeled according to rotor motion equation synchronous generator (SG). Furthermore, VSC's damping ratio derived, and effects control parameters operation status on equivalent power angle (EPA) investigated. Moreover, influence PLL's dips degree frequency behavior are analyzed. Analysis result reveals that decreases...

The virtual synchronous generator (VSG) control has been widely used in grid-connected inverter to effectively increase the equivalent inertia of power system. However, active oscillation similar electromechanical transient characteristics conventional (SG) is introduced grid, especially under condition multi-virtual synchronizer. In this paper, dynamic stability multiple voltage source converters (VSC) controlled by VSG studied. Firstly, system linearization model established analyze risk....

The dynamic behavior of converters with different synchronous control modes is significantly different. Therefore, the renewable energy grid-connected system cannot be equivalent as same type power electronics equipment. There are interactions among multiple time scale controllers each equipment, which may lead to small signal instability hybrid system. In this paper, a phase-locked loop (PLL) controlled doubly fed induction generator (DFIG) and virtual (VSG) converter studied. On basis...

Automatic page layout generation is a challenging and promising research task, which improves the design efficiency quality of various documents, web pages, etc. However, current layouts that are both reasonable aesthetically pleasing still faces many difficulties, such as shortcomings existing methods in terms structural rationality, element alignment, text image relationship processing, insufficient consideration details mutual influence within page. To address these issues, this article...

The commutation failure fault usually occurs in the line-commutated-converter-based high-voltage direct current transmission system. When occurs, voltage of sending alternate (ac) system changes rapidly, and connected doubly fed induction generator (DFIG)-based wind turbine may be tripped. Thus, ride through (FRT) control strategy DFIG should investigated for enhancing stability ac However, during is not changed rectangular shape, besides, presents "first reduce then rise" characteristic,...

The instability issues of grid-connected voltage source converters (VSC) may easily occur during low ride-through (LVRT), especially when connected to a weak ac grid. In this study, small-signal model the VSC system was developed deal with stability problems deep sags. Based on model, interaction between phase-locked loop (PLL) and current control has been illustrated. addition, eigenvalue modal analysis method employed investigate influencing factors stability, which include bandwidths PLL...

As the share of wind power in system increases, grid exhibits characteristics a weak grid. The dynamic stability issues grid-connected doubly fed induction generator (DFIG)-based turbines caused by interaction between phase-looked loop (PLL) and rotor current controller (RCC) high impedance have become acute, especially during low-voltage ride-through. In this article, output model DFIG is derived, where dynamics PLL been first taken into account. addition, RCC analyzed. Furthermore, novel...

Benefiting from the high breakdown voltage of silicon carbide (SiC) material, medium SiC power module has made an unprecedented breakthrough, which is regarded as a promising route for converter. However, partial discharge (PD) challenges reliability and safety module, limits its massive applications in industrial fields. In this article, insightful models are proposed to reveal mechanism electric-field-dominated PD module. Furthermore, it found that distorted electric field at triple point...

Fragility modeling and real-time risk assessment can be widely applied to evaluate enhances the resilience of power system High-Impact Low Probability events. In previous studies, fragility generally targets extreme weather conditions other than thunderstorm. This paper proposes a model describe relationship between duration thunderstorm probability lightning related trip-out. The thunderstorms, which usually forecasted from meteorological department, together with function expression help...

Small-signal stability issues of the voltage source converters (VSC) connected weak-network during asymmetric faults is currently rarely studied. This paper develops mathematic model VSC system weak-grid faults, which reveals dynamic coupling between phase-locked loop (PLL) and both positive-sequence (PS) control negative-sequence (NS) system. Based on deduced model, generalized Nyquist criterion (GNC) method modal analysis are adopted to study small-signal fault steady-state. The...

Fracturing fluid is a key factor affecting the hydraulic fracture morphology and coal microstructure, which plays role in fracturing effect. To compare effect of clean water, fluid, acid on pore structure coal, this paper used high-pressure mercury injection (MIP), low-temperature N2 adsorption (LT-N2A), scanning electron microscopy (SEM) to determine Guizhou bituminous before after action fluid. The results show that water can cause mineral expansion reduce volume by about 6% increase 3...

Lightning performance evaluation is aimed at classifying transmission lines into different risk levels of thunderstorm-induced trip-out. Its applications range from better lightning protection guidance, arrester installation design, line retrofits, and corridor design. Previous studies fail to consider the real-time intensity, which an essential factor trip-out that must not be ignored. This article proposes a novel model based on idea tower, has record with weaker more susceptible trip out,...

The stability issues of weak grid-connected doubly fed induction generator (DFIG) based wind turbines during asymmetric grid faults become very acute. In this article, a small-signal state-space model was established to deal with the problems DFIG system faults. Based on model, interaction mechanism between power and is described modal analysis performed. results show that dominant unstable poles are mainly affected by phase-locked loop (PLL). Then, according vector relationships voltages...

Purpose – Compared with the traditional printed circuit board (PCB) drilling process, technology of IC substrate is facing more problems, such as much smaller hole diameter, intensive space, thinner sheet and complicated materials are drilled in process. Moreover, base material different from PCB, kinds fillers added which make drill worn seriously during Micro-drills wear micro holes quality most important questions when so far. Wear morphology micro-drill, wall roughness location accuracy...

Abstract To obtain the similar materials with specific physical and mechanical parameters adsorption desorption indexes used in coal gas outburst simulation tests, pulverized was selected as aggregate, sodium humate cementing agent river sand auxiliary materials. Based on this, orthogonal tests 6 factors 5 levels were designed, of weighing, uniaxial compression, firmness, carried out. The such density, compressive strength, elastic modulus, firmness coefficient adsorption–desorption index...

Due to the increasing concern for global climate problem, electric vehicle has drawn considerable attention. The power module with high reliability is key deployment and development of vehicle. However, in-depth evaluations, such as tedious cycling, are generally required verify prior putting it into field application. Therefore, determine failure mechanism evaluate module, in situ full-field characterization 3-D deformation under application essential. Besides, results can also provide a...

The combustion characteristics of spark assistant compression ignition mode under different loads and fuels were explored, as well by constructing artificial neural networks(ANN) model, the prediction ability algorithms for engine performance was discussed. Burning methanol n-butanol can help to improve IMEP induce earlier spontaneous combustion. knock intensity(KI) fueled with highest followed gasoline, but maximum amplitude filtered pressure oscillation(MAPO) shows opposite trend. KI...

In this article, the frequency coupling of weak grid-connected doubly fed induction generator (DFIG) based wind turbines (WT) during asymmetric faults have received little attention. To analyze phenomenon system faults, article established complex transfer function model in αβ frame on transformation relationship between and matrix. According to function, mechanism DFIG is revealed, evolution law frequencies described detail. Finally, correction theoretical analysis validity proposed models...