scholarly journals Error Characteristic Analysis of Fluid Momentum Law Test Apparatus

2020 ◽  
Vol 11 (1) ◽  
pp. 90
Author(s):  
Song Yang ◽  
Xianyong Zhu ◽  
Hui Wang
Keyword(s):  
Measurement Error ◽  
Control Method ◽  
Theoretical Research ◽  
Structural Deformation ◽  
Error Characteristic ◽  
Characteristic Analysis ◽  
Jet Impact ◽  
Effect Theory ◽  
Characteristic Points ◽  
Periodic Error

The flat-plate momentum test bench is a widely used experimental device in the verification of the momentum law of fluid mechanics, and its error characteristics are of positive significance for theoretical research and engineering innovation and expansion. The SPH-FEM coupling algorithm and spectrum analysis method are used to calculate and analyze the displacement response and spectrum characteristics of the characteristic points of the sensor under different jet loads. Based on them, the cause, classification, law, scope, influence and control method of the measurement error of the system are discussed and analyzed with the application of the error theory and the lateral effect theory of strain gauges; combined with physical experiments, the relevant analysis methods and conclusions are verified. The results show that the measurement error of the system includes linear error and periodic error. Structural deformation in the direction of jet impact is the main source of linear error; linear error increases with the increase of jet loads. Meanwhile, periodic vibration in non-jet direction is the main cause of periodic error, and the periodic error decreases with the increase of jet loads.

scholarly journals Influencing Factor and Error Analysis of Operating Capacitor Voltage Transformer Harmonic Measurement

2021 ◽  
Vol 2121 (1) ◽  
pp. 012013
Author(s):  
Yan Zhang ◽  
Huajia Wang ◽  
Danwen Yu ◽  
Liu Yang ◽  
Wenjun Cao ◽  
...  
Keyword(s):  
Measurement Error ◽  
Measurement Errors ◽  
Influencing Factor ◽  
Screening Method ◽  
Error Characteristic ◽  
Characteristic Analysis ◽  
Voltage Transformer ◽  
Capacitor Voltage ◽  
The Impact ◽  
Harmonic Measurement

Abstract With the increasing demands of power quality monitoring and management, the problem of harmonic measurement error caused by the widespread operation of capacitor voltage transformers (CVT) in high-voltage power grids has been unavoidable. This paper analyses the influence of environmental factors on harmonic measurement error of CVT, and proposes a new method for analysing the harmonic measurement errors of operating CVT, which explains the unstable phenomenon of CVT measurement errors based on field comparison test, and provides a progressing screening method of effective analysis data. the CVT harmonic error characteristic analysis method proposed in this paper considers the impact of field installation conditions, electromagnetic environment, and other actual operating environment, which can reflect the actual harmonic error characteristics of CVT in field operation. A CVT harmonic measurement system is established based on the proposed method. The validation and effectiveness of the proposed method is illustrated on a field measurements of 1000kV CVT in Shandong Province.

scholarly journals Theoretical basis for the formation of damaging factors during the coal aerosol explosion

2021 ◽  
Vol 15 (4) ◽  
pp. 130-138
Author(s):  
Olena Zavialova ◽  
Viktor Kostenko ◽  
Natalia Liashok ◽  
Mykola Grygorian ◽  
Tetiana Kostenko ◽  
...  
Keyword(s):  
Mine Working ◽  
Gaseous Medium ◽  
Coal Dust ◽  
Theoretical Research ◽  
Dust Explosion ◽  
Characteristic Points ◽  
Explosion Mechanism ◽  
Mine Workings ◽  
Negative Factors ◽  
Dust Deposits

Purpose. Assessing the process of damaging factors formation during the coal aerosol explosion in mine workings on the basis of theoretical research of the explosion of coal dust deposits in order to substantiate promising methods of protecting miners from their impact. Methods. An integrated approach is used, which includes a critical analysis of literature data on the occurrence and development of coal aerosol explosions in mine workings; theoretical research into the state of the gaseous medium at the characteristic points of the development diagram of the coal dust deposits explosion as a result of mining operations based on the laws of classical physics and chemistry. Findings. The main aspects of the explosion mechanism of dust in a powdery state, accumulated on the surfaces along the mine working perimeter, and the formation of such negative factors as the effect of gaseous medium accelerated movement, have been revealed; high temperature formed during coal and methane detonative combustion; increased gas pressure. The revealed aspects of the dust explosion mechanism make it possible to determine the main directions for protection of miners caught in the explosion. The diagram of the development of settled coal dust explosion along the mine working with normal ventilation conditions, taking into account the influence of seismic waves, has been improved. Originality. Analytical dependences, reflecting the value of gas energy at characteristic points of the diagram, have been determined, and the dynamics of the formation of negative factors caused by the explosion have been revealed. Practical implications. Possible ways of protecting miners from the impact of negative factors caused by the coal aerosol explosion and reducing the severe consequences of such accidents are proposed.

A Control Method for Active Power Filters with Three-Level NPC Inverter

2011 ◽  
Vol 268-270 ◽  
pp. 428-433
Author(s):  
Chen Guo ◽  
Cun Bing Gui ◽  
Zhong Ren Chen
Keyword(s):  
Control Algorithm ◽  
Control Method ◽  
Sampling Period ◽  
Active Power ◽  
Pi Control ◽  
State Variables ◽  
Active Power Filters ◽  
Power Filters ◽  
Repetitive Nature ◽  
Periodic Error

This paper researches control problem for active power filters with three-level NPC inverter and proposes a novel PI control algorithm for tracking harmonic command current. This novel PI control algorithm can suppress the periodic error in the whole system to achieve zero steady error tracking. In this scheme, the state variables are estimated with a state observer to cancel the delay of one sampling period in this digital control system. Harmonic current is predicted with a repetitive algorithm simultaneity, which makes use of the repetitive nature of load current. The controller is analyzed and designed in the paper, and the experiment results illustrate that this APF can be controlled in a satisfactory way.

Aeromechanical Analysis of Two-Bladed Downwind Turbine Using a Nacelle Tilt Control

2017 ◽  
Author(s):  
Qiuying Zhao ◽  
Chunhua Sheng ◽  
Yousuf Al-Khalifin ◽  
Abdollah Afjeh
Keyword(s):  
Wind Turbine ◽  
Structural Dynamics ◽  
Control Method ◽  
Offshore Wind ◽  
Structural Deformation ◽  
Offshore Wind Turbine ◽  
System Response ◽  
High Fidelity ◽  
Dynamics Analysis ◽  
Control Concept

The structural dynamics and response of a two-bladed downwind wind turbine using a new nacelle tilt control are numerically investigated based on a coupled Computational Fluid Dynamics and Computational Structural Dynamics analysis. The new wind turbine tilt control method is investigated to regulate the power output under a varying wind speed environment for offshore wind turbines. The high fidelity aerodynamic loads obtained from CFD computations are used as input in a CSD code to perform a structural dynamics analysis in order to predict the system response and structural deformation of the two-bladed downwind turbine. The coupled CFD and CSD analysis provide high fidelity assessments of the aeromechanical performance with increased accuracy to evaluate the new nacelle tilt control concept, which may lead to an alternative wind turbine control strategy with reduced costs for offshore wind turbine operations.

Digitalization Control and Characteristic Analysis of a Superconducting Inductive Energy Management System

2013 ◽  
Vol 416-417 ◽  
pp. 474-479 ◽  
Author(s):  
Jian Xun Jin ◽  
Wei Xu ◽  
Xin Zhou ◽  
Xiao Yuan Chen
Keyword(s):  
Energy Storage ◽  
Energy Management ◽  
Management System ◽  
High Efficiency ◽  
Control Method ◽  
Magnetic Energy ◽  
Storage Device ◽  
Energy Management System ◽  
Characteristic Analysis ◽  
Energy Control

In past decades, the technique of superconducting magnetic energy storage (SMES) has received substantial attention both by academia and industry with the great improvement of applicable high temperature superconductors and relevant control technologies. A bridge-type inductive energy management system topology is presented for SMES applications by using a concept of digitalization. The inductive power charging, storing and discharging status are modelled, and then digitalized for the advanced control implementation. As a consequence, an inductive energy control method can be realized by the digitalized models to satisfy relative project requirements by high efficiency and control precession. New principles and methodologies provide the theoretical foundation to achieve digital power inductor energy control and superconducting inductive energy storage device operation.

scholarly journals Adaptive Gain Control Method of a Phase-Locked Loop for GNSS Carrier Signal Tracking

2018 ◽  
Vol 2018 ◽  
pp. 1-14
Author(s):  
Zhibin Luo ◽  
Jicheng Ding ◽  
Lin Zhao
Keyword(s):  
Control Method ◽  
Tracking Error ◽  
Gain Control ◽  
Phase Locked Loop ◽  
Satellite System ◽  
Error Characteristic ◽  
Loop Gain ◽  
Target Movement ◽  
Signal Tracking ◽  
Global Navigation Satellite

The global navigation satellite system (GNSS) has been widely used in both military and civil fields. This study focuses on enhancing the carrier tracking ability of the phase-locked loop (PLL) in GNSS receivers for high-dynamic application. The PLL is a very popular and practical approach for tracking the GNSS carrier signal which propagates in the form of electromagnetic wave. However, a PLL with constant coefficient would be suboptimal. Adaptive loop noise bandwidth techniques proposed by previous researches can improve PLL tracking behavior to some extent. This paper presents a novel PLL with an adaptive loop gain control filter (AGCF-PLL) that can provide an alternative. The mathematical model based on second- and third-order PLL was derived. The error characteristics of the AGCF-PLL were also derived and analyzed under different signal conditions, which mainly refers to the different combinations of carrier phase dynamic and signal strength. Based on error characteristic curves, the optimal loop gain control method has been achieved to minimize tracking error. Finally, the completely adaptive loop gain control algorithm was designed. Comparable test results and analysis using the new method, conventional PLL, FLL-assisted PLL, and FAB-LL demonstrate that the AGCF-PLL has stronger adaptability to high target movement dynamic.

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