Journal articles: 'Unbalanced mode'

1

Tang, Zhong, Xiyao Li, Xin Liu, Hui Ren, and Biao Zhang. "Dynamic Balance Method for Grading the Chain Drive Double Threshing Drum of a Combine Harvester." Applied Sciences 10, no. 3 (February 4, 2020): 1026. http://dx.doi.org/10.3390/app10031026.

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Although the individual threshing drum of a combine harvester was balanced on a dynamic balancing machine before it is assembled, there were still unbalances after multiple drums were assembled with the chain drive. In this paper, the double drums with a chain drive of a crawler combined harvester were selected as the research subject. The aim of this study was to develop a dynamic unbalance mode for grading chain drive double drums. Based on the dynamic unbalance characteristics of the main driven drum, the experimental research on the radial balance of the driven drum end face was carried out. It was known that the chain drive had a direct and obvious influence on the unbalanced phase of the drum. The unbalance of the drive load had an obvious effect on unbalanced amplitude of an active drum through the transfer characteristics of the chain drive. For the multi-stage transmission characteristics of a combine harvester, a step-by-step balanced grading chain drive double drum dynamic balancing method was practiced. Results showed that the unbalanced amplitude after balancing threshing drum I chain transmission mode of the combine harvester can be reduced by a maximum of 91%. Simultaneously, the unbalanced amplitude of threshing drum II can reduced by a maximum of 69.2%. The size and position of the wrap angle of the chain drive would directly affect the phase of the two equivalent unbalanced masses.

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Xu, Lin, Wei Yu, and Jian-Xin Chen. "Unbalanced-/Balanced-to-Unbalanced Diplexer Based on Dual-Mode Dielectric Resonator." IEEE Access 9 (2021): 53326–32. http://dx.doi.org/10.1109/access.2021.3070328.

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Huang, Mei, Zhao Yang Xing, Yuan Yuan Zhao, Jian Nan Tang, and Hao Yuan. "Modal Analysis and Unbalanced Response Analysis of Rotor System." Applied Mechanics and Materials 668-669 (October 2014): 209–12. http://dx.doi.org/10.4028/www.scientific.net/amm.668-669.209.

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In this article, the entity model of the bearing-rotor system is established and meshed in ANSYS. The natural frequency and vibration mode of the rotor system is analyzed in order to avoid the occurrence of resonance. At the same time, the results showed that not only the location of the unbalance incentive of the system should be taken into account, but also consider the size of the unbalanced force.

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Xia, Mingchao, and Yanhui Mao. "Integral Sliding Mode Control Strategy of D-STATCOM for Unbalanced Load Compensation under Various Disturbances." Mathematical Problems in Engineering 2013 (2013): 1–14. http://dx.doi.org/10.1155/2013/932389.

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Control strategies of D-STATCOM for unbalanced load compensation under internal and external disturbances were discussed. Linear control strategies do not have a satisfactory dynamic performance and become invalid under internal or external disturbances. To guarantee a good precision and robustness, a control strategy combining input-output feedback linearization technique with integral sliding mode control (ISMC) method was applied to D-STATCOM for unbalanced load compensation. The strategy has features of simple structure and is easy to implement. A 10 MVar/10 kV D-STATCOM simulation system was built in PSCAD/EMTDC to verify the effectiveness and robustness of the control strategy proposed. Simulation results show that the control strategy can compensate reactive power and eliminate unbalance simultaneously under various disturbances.

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Li, Yu, Zhong Tang, Xinzhong Wang, Hao Zhang, and Yaoming Li. "Bearing Seat Vibration Modes Undergoing Unbalanced Excitation of Multirotating Drums." Shock and Vibration 2021 (December 28, 2021): 1–20. http://dx.doi.org/10.1155/2021/5655150.

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Transmission modes of multiple rotating parts on combine harvester are complex and diverse, which resulted in large vibration and poor stability when the entire machine is harvesting. Aiming at the complex vibration problem of the combine harvester threshing system, this paper established the dynamic response model of the multidrum parallel system under different transmission modes and solved the vibration characteristics of the system. An experiment on the axial unbalance response of the parallel drum system under different transmission modes was carried out. The results show that the internal units of the threshing system form a whole through the transmission system, which causes the unbalanced response of the system to be superimposed on parallel threshing drums, thereby increasing the vibration amplitude. In addition, the change of the transmission mode will cause the vibration transmission path in the system to change greatly, and the boundary conditions of the system will be changed at the same time, which will eventually lead to the change of the unbalanced response characteristics.

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Naumov, IgorV, and Sergey V. Podyachikh. "The 0.38 kV “Green Network” Operating Modes Simulation with Multi-Level Unbalanced Power Consumption." IOP Conference Series: Earth and Environmental Science 990, no. 1 (February 1, 2022): 012055. http://dx.doi.org/10.1088/1755-1315/990/1/012055.

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Abstract The article considers modeling, parameters calculation and analysis of the rural electric networks operating modes, containing power take-off units with multi-level unbalanced power consumption. At the same time, a low-voltage electrical network section fragment is considered as a certain cluster in the structure of an extensive and heterogeneous 0.38 kV network. The model is made for a certain “green network” cluster variant, containing several nodes of highly unbalancing power consumption with a balancing device (BD). Connecting options the BD in various power take-off nodes, including power supply buses, are considered. As a balancing technical means, a device is presented that has a minimum resistance to zero-sequence currents with its power automatically control in a zero-sequence currents function. The main criteria for assessing the currents and voltages unbalanced level are the zero-sequence voltage unbalance coefficient, which characterizes the power quality, as well as the power loss coefficient, which characterizes the increase in power and energy losses in the unbalanced mode. Based on the developed method, algorithm and computer program “Unbalance”, the calculation was made and the changes characteristics in the studied indicators were constructed using modern the Matlab graphics editor technologies. The analysis of the studied indicators was carried out, on the which basis the most appropriate node in the electrical network model was determined, where the functioning efficiency of the balancing device will be the greatest.

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Agili, Sedig S., Stephen B. Smith, and Vittal Balasubramanian. "Unbalanced line characterization for differential-mode operation." Microwave and Optical Technology Letters 48, no. 6 (2006): 1169–74. http://dx.doi.org/10.1002/mop.21549.

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Li, Feng Lin, Shu Ju Hu, and Ling Ling Wang. "Control of Quasi-Z Source Inverter with Super Capacitor under Unbalanced Grid Fault Conditions." Applied Mechanics and Materials 291-294 (February 2013): 2124–31. http://dx.doi.org/10.4028/www.scientific.net/amm.291-294.2124.

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The quasi-Z-source inverter (qZSI) has some unique advantages and is suitable for renewable energy sources such as solar and wind generation system. In order to make the inverter have the ride-through ability and the current into the grid symmetrical when unbalanced grid faults occur, the topology of qZSI with super capacitor substituting the low voltage capacitor and the unbalance control strategy were proposed. With a super capacitor the system can balance and smooth the power between the generation unit and grid, also the current injected into the grid can be symmetrical through the unbalance control method. The circuit of the new topology and the mathematical model of the three-phase converter under grid voltage unbalance conditions have been analyzed. And then, closed-loop control scheme for the proposed system is used to control the power flow of generation unit, grid and super capacitor in this system, also unbalance control strategies in positive (dq) + and negative (dq) – reference frames have been implemented in the grid-connected qZSI system to make the current into the grid symmetrical during the grid fault. The operating mode during unbalanced grid fault is simulated in MATLAB/Simulink, and the simulation results are presented to verify the theoretical analysis and the control scheme.

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Wetzel, Alfredo N., Leslie M. Smith, Samuel N. Stechmann, Jonathan E. Martin, and Yeyu Zhang. "Potential Vorticity and Balanced and Unbalanced Moisture." Journal of the Atmospheric Sciences 77, no. 6 (May 6, 2020): 1913–31. http://dx.doi.org/10.1175/jas-d-19-0311.1.

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Abstract Atmospheric flows are often decomposed into balanced (low frequency) and unbalanced (high frequency) components. For a dry atmosphere, it is known that a single mode, the potential vorticity (PV), is enough to describe the balanced flow and determine its evolution. For a moist atmosphere with phase changes, on the other hand, balanced–unbalanced decompositions involve additional complexity. In this paper, we illustrate that additional balanced modes, beyond PV, arise from the moisture. To support and motivate the discussion, we consider balanced–unbalanced decompositions arising from a simplified Boussinesq numerical simulation and a hemispheric-sized channel simulation using the Weather Research and Forecasting (WRF) Model. One important role of the balanced moist modes is in the inversion principle that is used to recover the moist balanced flow: rather than traditional PV inversion that involves only the PV variable, it is PV-and-M inversion that is needed, involving M variables that describe the moist balanced modes. In examples of PV-and-M inversion, we show that one can decompose all significant atmospheric variables, including total water or water vapor, into balanced (vortical mode) and unbalanced (inertio-gravity wave) components. The moist inversion, thus, extends the traditional dry PV inversion to allow for moisture and phase changes. In addition, we illustrate that the moist balanced modes are essentially conserved quantities of the flow, and they act qualitatively as additional PV-like modes of the system that track balanced moisture.

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10

Xue, Quan, Jin Shi, and Jian-Xin Chen. "Unbalanced-to-Balanced and Balanced-to-Unbalanced Diplexer With High Selectivity and Common-Mode Suppression." IEEE Transactions on Microwave Theory and Techniques 59, no. 11 (November 2011): 2848–55. http://dx.doi.org/10.1109/tmtt.2011.2165960.

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11

Zhang, Hongji. "Effect of Unbalanced Force Loading on the Safety of Transmission Tower." IOP Conference Series: Earth and Environmental Science 898, no. 1 (October 1, 2021): 012011. http://dx.doi.org/10.1088/1755-1315/898/1/012011.

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Abstract High-voltage transmission towers, as support points for overhead transmission lines, are often under the condition of unbalanced force loading. Transmission towers can collapse because of the unbalanced forces, leading to the power outage. Therefore, it is of practical importance to set a research on the effect of unbalanced force loading on the safety of transmission tower. In this paper, based on the prototype of 500kV transmission tower, the integral beam element model is established by ABAQUS finite element software for simulation analysis. Static load mode and unbalanced force loading were considered in this simulation model. Through the comparative analysis of the maximum displacement and stress in transmission tower, the safety of the 500kV transmission tower was analyzed. The variations of maximum displacement and Mises stress with the increasing unbalanced force were obtained. The limit of unbalanced force the 500kV transmission tower can sustain was given by comparing the simulated results.

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12

Yang, S. M., and G. J. Sheu. "Vibration Control of a Rotating Shaft: An Analytical Solution." Journal of Applied Mechanics 66, no. 1 (March 1, 1999): 254–59. http://dx.doi.org/10.1115/1.2789155.

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It has been shown that a rotating shaft in the Rayleigh beam model has only a finite number of whirl speeds and vibration modes when the rotating speed is higher than half of the whirl speed. The system’s unbalanced response can therefore be written analytically by the vibration modes and the generalized coordinates. This paper presents an analytical controller design of optimal sensor/actuator location and feedback gain for minimizing the steady-state unbalanced response. Because all of the critical speeds and vibration modes are included in the controller design, there will be no residual mode, hence no spillover. An example is used to illustrate that the controller design in collocated or noncollocated configuration not only guarantees the closed-loop stability but also effectively suppresses the unbalanced response.

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Antsiferov, N. S. "Ways to Reduce Power Losses in Mining Power Supply Lines." Mining science and technology 4, no. 2 (August 25, 2019): 150–56. http://dx.doi.org/10.17073/2500-0632-2019-2-150-156.

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Electric energy is the most common and universal form of energy. It can be produced in large quantities near energy sources, transmitted to large distances, easily distributed between consumers and converted into mechanical, thermal, and light energy. Ensuring reliable and economical quality electric energy supply to mining enterprises with the optimal use of energy resources is one of the most important tasks facing the country's energy sector. In the Russian Federation, high degree of concentration of generating capacities at power plants has been achieved. The main capacities are concentrated in power plants with installed capacity of more than 1 million kW. High importance of the electric power industry is determined by the infrastructural nature of the industry and the direct relationship between the country's economic growth and the level of its development effectiveness. One of the most pressing problems of modern electricity supply is the problem of ensuring the quality of electric energy. The main reason for the deterioration in the electricity quality is widespread non-linear loads that create non-sinusoidal currents and voltage unbalance during their operation. The voltage unbalance is most often caused by the presence of an unbalanced load. Unbalanced load currents flowing through the elements of the power supply system cause unbalanced voltage losses in them. This results in appearance of unbalanced voltages on the terminals of electric apparatus. The voltage deviations at electric apparatus overdriven phase may exceed the normally acceptable values, while the voltage deviations at electric apparatus other phases may remain within the normal limits. In addition to the deterioration of the voltage mode at electric apparatus under the unbalanced voltage conditions, the operating conditions of both the electric apparatus and all the network elements are significantly worsened, and the reliability of the electrical equipment and the power supply system as a whole decreased. The paper considers the issues of reducing the voltage losses in power supply networks by improving quality of electric power.

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Xie, Yan, Ya Ne Liao, and Zhe Mao. "Study on Unbalance Compensation Control of STATCOM Based on MMC." Advanced Materials Research 852 (January 2014): 401–5. http://dx.doi.org/10.4028/www.scientific.net/amr.852.401.

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This paper introduced a new modular multi-level converter (MMC), which could enhance the voltage and power level by sub-converter modules in series and was easy to extend to any level of output. Its structure and working mechanism were described. By analyzing the energy transfer performance of STATCOM based on MMC working conditions in the unbalance compensation, this paper studied compensation control theory in unbalanced complex conditions. To obtain compensation control response speed faster and better compensation effect, a comprehensive compensation control strategy was proposed based on direct current control mode. The simulation results show the strategy has a better tracking precision and response speed for the unbalance compensation current.

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Ahrabian, Alireza, Naveed Ur Rehman, and Danilo Mandic. "Bivariate Empirical Mode Decomposition for Unbalanced Real-World Signals." IEEE Signal Processing Letters 20, no. 3 (March 2013): 245–48. http://dx.doi.org/10.1109/lsp.2013.2242062.

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Liu, Wan Lin, Ling Zhang, and Chun Li Qu. "Unbalanced Quotation Improvement Strategy Research under the Bill of Quantities Valuation Mode." Applied Mechanics and Materials 584-586 (July 2014): 2622–25. http://dx.doi.org/10.4028/www.scientific.net/amm.584-586.2622.

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Combining with China's current bidding methods that are commonly used in tendering process, the article introduces the concept, principle and characteristics of unbalanced bidding, and establishes unbalanced quotation improvement strategy model based on capital time-value theory and linear programming. This model can reduce the enterprise's bidding quotation scientifically and increase the successful bid probability without changing the corporate earnings. Meanwhile, the article combines with actual application cases, indicating that the model is practical and operable.

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Ruiqi, Wang, Jin Zhanxin, Li Sun, Wang Zhaoxin, Jiang Wenjuan, Cheng Yan, and Zhang Yong. "Power Quality Control Strategy of Islanding Microgrid Under Distorted and Unbalanced Conditions." Open Electrical & Electronic Engineering Journal 8, no. 1 (December 31, 2014): 559–66. http://dx.doi.org/10.2174/1874129001408010559.

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This paper presents a novel power quality control strategy for islanding microgrid contains multiple DG units under both distorted and unbalanced conditions. Actually the power quality of microgrid bus and the point of common coupling (PCC) are the main concerns due to the determination of high-quality power energy to the main grid and sensitive loads connected to microgrid bus. To tackle this problem, three control schemes based on PIR cascaded structure for DG units are developed to realize different control objectives. In these categories, the fundamental voltage is regulated by conventional PI controller to ensure direct voltage support and smooth operation mode transition while the harmonics or unbalanced variables are compensated with resonates controller in synchronous reference frame without sequential sequence decomposition. The proposed power quality control strategy that comprehensively utilization of these control schemes can satisfy power quality requirements of islanding microgrid, which is confirmed by simulation results considering both unbalance and distortion.

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Wen-kuan, XU, and ZHANG You-peng. "Research on Wind Turbine Converter Control Based on Resonant Sliding Film Controller." E3S Web of Conferences 236 (2021): 01020. http://dx.doi.org/10.1051/e3sconf/202123601020.

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A resonant sliding mode control strategy based on the resonant sliding film surface is proposed to control the turbine-side converter of the wind turbine so that the wind turbine can be connected to the grid smoothly under the condition of unbalanced grid voltage. Taking the doubly-fed asynchronous wind generator working under unbalanced grid voltage as the control object, establish its mathematical model and its generator-side converter. Taking the instantaneous power in the α β static coordinate system as the state variable of the sliding mode controller, the resonant sliding mode controller is studied, its parameters are designed, and experiments are carried out in the simulation platform MATLAB. A 1.5MW motor model was established and tested, and it was verified that the resonant sliding mode control strategy can control the grid voltage without static error and realize the smooth grid connection of wind turbines.

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Yaroshevich, Nikolay, Volodymyr Gursky, Vitalii Puts, Olha Yaroshevych, and Viktor Martyniuk. "On the dynamics of vibrational capture of rotation of an unbalanced rotor." Vibroengineering PROCEDIA 42 (May 16, 2022): 1–6. http://dx.doi.org/10.21595/vp.2022.22413.

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Stationary (near stationary) rotation modes of an unbalanced rotor with the oscillation frequency of its axis are considered. From the standpoint of I. I. Blekhman vibrational mechanics, explanations of the mechanism of vibrational capture of the rotation of an unbalanced rotor are given. It is demonstrated that the vibration moment arising as a result of oscillations tends to synchronize vibrational and rotational movements. In addition its effect in the stationary mode becomes unambiguous – either braking or accelerating. It is shown that when a stationary rotation mode is established, large, relatively slow oscillations of rotor’s speed can occur. Theoretical results are confirmed by computer simulation.

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Ren, Hongtao, and Huiqing Lv. "Study on the influence of typical faults in AC area on DC voltage." Journal of Physics: Conference Series 2237, no. 1 (March 1, 2022): 012007. http://dx.doi.org/10.1088/1742-6596/2237/1/012007.

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Abstract By summarizing the architecture and operation control of the existing models, this paper establishes a typical DC power distribution structure model, and studies the wiring mode and working principle of the converter. For the DC distribution network under VSC pseudo bipolar operation mode, when considering the grounding mode, we focus on the neutral point of the connection transformer on the AC side, the filter neutral point on the AC side and the capacitor neutral point on the DC side. The causes and recovery process of DC positive and negative unbalanced voltage are analyzed. Begin in the asymmetric fault in the AC area, the paper proposes the cause and recovery process theory of unbalanced voltage of capacitors on DC side, the paper also analyzed the fault characteristics in AC area, and proposes the suitable grounding mode.

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Chouksey, Manita, Carsten Eden, and Nils Brüggemann. "Internal Gravity Wave Emission in Different Dynamical Regimes." Journal of Physical Oceanography 48, no. 8 (August 2018): 1709–30. http://dx.doi.org/10.1175/jpo-d-17-0158.1.

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AbstractWe aim to diagnose internal gravity waves emitted from balanced flow and investigate their role in the downscale transfer of energy. We use an idealized numerical model to simulate a range of baroclinically unstable flows to mimic dynamical regimes ranging from ageostrophic to quasigeostrophic flows. Wavelike signals present in the simulated flows, seen for instance in the vertical velocity, can be related to gravity wave activity identified by frequency and frequency–wavenumber spectra. To explicitly assign the energy contributions to the balanced and unbalanced (gravity) modes, we perform linear and nonlinear modal decomposition to decompose the full state variable into its balanced and unbalanced counterparts. The linear decomposition shows a reasonable separation of the slow and fast modes but is no longer valid when applied to a nonlinear system. To account for the nonlinearity in our system, we apply the normal mode initialization technique proposed by Machenhauer in 1977. Further, we assess the strength of the gravity wave activity and dissipation related to the decomposed modes for different dynamical regimes. We find that gravity wave emission becomes increasingly stronger going from quasigeostrophic to ageostrophic regime. The kinetic energy tied to the unbalanced mode scales close to Ro2 (or Ri−1), with Ro and Ri being the Rossby and Richardson numbers, respectively. Furthermore, internal gravity waves dissipate predominantly through small-scale dissipation, which emphasizes their role in the downscale energy transfer.

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Nakano, Hisamatsu, Tatsuya Igarashi, Hiroshi Oyanagi, Yasushi Iitsuka, and Junji Yamauchi. "Unbalanced-Mode Spiral Antenna Backed by an Extremely Shallow Cavity." IEEE Transactions on Antennas and Propagation 57, no. 6 (June 2009): 1625–33. http://dx.doi.org/10.1109/tap.2009.2019916.

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23

Wong, Sai-Wai, Jing-Yu Lin, YangYang, He Zhu, Rui-Sen Chen, Lei Zhu, and Yejun He. "Cavity Balanced and Unbalanced Diplexer Based on Triple-Mode Resonator." IEEE Transactions on Industrial Electronics 67, no. 6 (June 2020): 4969–79. http://dx.doi.org/10.1109/tie.2019.2928253.

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Han and Ma. "Adaptive-Gain Second-Order Sliding Mode Direct Power Control for Wind-Turbine-Driven DFIG under Balanced and Unbalanced Grid Voltage." Energies 12, no. 20 (October 14, 2019): 3886. http://dx.doi.org/10.3390/en12203886.

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In a wind turbine system, a doubly-fed induction generator (DFIG), with nonlinear and high-dimensional dynamics, is generally subjected to unbalanced grid voltage and unknown uncertainty. This paper proposes a novel adaptive-gain second-order sliding mode direct power control (AGSOSM-DPC) strategy for a wind-turbine-driven DFIG, valid for both balanced and unbalanced grid voltage. The AGSOSM-DPC control scheme is presented in detail to restrain rotor voltage chattering and deal with the scenario of unknown uncertainty upper bound. Stator current harmonics and electromagnetic torque ripples can be simultaneously restrained without phase-locked loop (PLL) and phase sequence decomposition using new active power expression. Adaptive control gains are deduced based on the Lyapunov stability method. Comparative simulations under three DPC schemes are executed on a 2-MW DFIG under both balanced and unbalanced grid voltage. The proposed strategy achieved active and reactive power regulation under a two-phase stationary reference frame for both balanced and unbalanced grid voltage. An uncertainty upper bound is not needed in advance, and the sliding mode control chattering is greatly restrained. The simulation results verify the effectiveness, robustness, and superiority of the AGSOSM-DPC strategy.

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Naumov, I. V., and D. A. Karamov. "On the issue of occurrence of fire-hazardous situations with unbalanced power consumption." Safety and Reliability of Power Industry 14, no. 1 (May 4, 2021): 69–76. http://dx.doi.org/10.24223/1999-5555-2021-14-1-69-76.

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The influence of phase current unbalance on the probability of occurrence of fire-hazardous situations in industrial premises that receive power in various power supply systems is considered. The theoretical prerequisites for the occurrence of fire-hazardous situations are described. It is shown that zero-sequence flows flowing through a neutral conductor in an unbalanced mode significantly heat it, which can lead to short circuits and conditions for the occurrence of fires. The results of studies of unbalanced conditions in Russia and abroad are presented. It is shown that the zero-sequence flows resulting from current unbalance lead to an increase in additional losses of active power and electrical energy. It is proved that additional heat losses caused by unbalanced power consumption can destroy the insulation of neutral and phase conductors, which is the main cause of short circuits and, as a result, fires. Based on the use of the Matlab graphical editor, dynamic characteristics of variations in phase and interphase currents and voltages, as well as the power loss coefficient, which characterizes the increase in heat losses, are constructed. The analysis of fires and their consequences for various objects in the Russian Federation is made. A computational unit has been developed in Matlab, which is used for calculating and plotting the dynamics of fires and their consequences over the investigated period of time. It is shown that the occurrence of fires and their consequences due to violations of the rules of operation of electrical installations occurs in any premises and sometimes reaches more than 20% of all possible causes of fires. Methods and technical means of minimizing zero-sequence currents as a means of preventing the occurrence of fire-hazardous situations are considered. The principle of operation of an automatically controlled shunt-symmetric device with a minimum resistance to zero-sequence currents is described.

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Tran, Yen, Toshiyuki Yamamoto, Hitomi Sato, Tomio Miwa, and Takayuki Morikawa. "The analysis of influences of attitudes on mode choice under highly unbalanced mode share patterns." Journal of Choice Modelling 36 (September 2020): 100227. http://dx.doi.org/10.1016/j.jocm.2020.100227.

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Neef, Lisa J., Saroja M. Polavarapu, and Theodore G. Shepherd. "Four-Dimensional Data Assimilation and Balanced Dynamics." Journal of the Atmospheric Sciences 63, no. 7 (July 1, 2006): 1840–58. http://dx.doi.org/10.1175/jas3714.1.

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Abstract The problem of spurious excitation of gravity waves in the context of four-dimensional data assimilation is investigated using a simple model of balanced dynamics. The model admits a chaotic vortical mode coupled to a comparatively fast gravity wave mode, and can be initialized such that the model evolves on a so-called slow manifold, where the fast motion is suppressed. Identical twin assimilation experiments are performed, comparing the extended and ensemble Kalman filters (EKF and EnKF, respectively). The EKF uses a tangent linear model (TLM) to estimate the evolution of forecast error statistics in time, whereas the EnKF uses the statistics of an ensemble of nonlinear model integrations. Specifically, the case is examined where the true state is balanced, but observation errors project onto all degrees of freedom, including the fast modes. It is shown that the EKF and EnKF will assimilate observations in a balanced way only if certain assumptions hold, and that, outside of ideal cases (i.e., with very frequent observations), dynamical balance can easily be lost in the assimilation. For the EKF, the repeated adjustment of the covariances by the assimilation of observations can easily unbalance the TLM, and destroy the assumptions on which balanced assimilation rests. It is shown that an important factor is the choice of initial forecast error covariance matrix. A balance-constrained EKF is described and compared to the standard EKF, and shown to offer significant improvement for observation frequencies where balance in the standard EKF is lost. The EnKF is advantageous in that balance in the error covariances relies only on a balanced forecast ensemble, and that the analysis step is an ensemble-mean operation. Numerical experiments show that the EnKF may be preferable to the EKF in terms of balance, though its validity is limited by ensemble size. It is also found that overobserving can lead to a more unbalanced forecast ensemble and thus to an unbalanced analysis.

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Sun, Dan, and Xiaohe Wang. "Sliding‐mode DPC using SOGI for DFIG under unbalanced grid condition." Electronics Letters 53, no. 10 (May 2017): 674–76. http://dx.doi.org/10.1049/el.2017.0963.

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Liu, Jun, Hai Jun Yuan, and Hua Li. "The Arching Process Research of SRC Beam." Applied Mechanics and Materials 482 (December 2013): 74–77. http://dx.doi.org/10.4028/www.scientific.net/amm.482.74.

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The purpose: The method to calculate slab-column middle connections under combined interaction of vertical shear and unbalanced moment is given to perfect the design method of slab-column structure; Method: The calculation method is proposed based on the calculation method of slab-column connection and the experimental data made by domestic and foreign scholars is used to verify. Result: The results verified by the formula are shown to be in good agreement with actual results. Conclusion: The interaction of shear and unbalanced moment are taken into account in the formula, including the transfer mode of unbalanced moment and the beneficial effects of shear reinforcement, to make the calculation more reasonable.

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Shihabudin Ismail, Mohd, M. I. Hussain, Zuraidah M. Zain, and Noorhafiza Muhd. "A Management Guide for Determination of Optimal Buffer Allocation in Unpaced Production Line Using 6 Steps OBA." Applied Mechanics and Materials 793 (September 2015): 637–41. http://dx.doi.org/10.4028/www.scientific.net/amm.793.637.

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This paper deals with a buffer allocation problem in unpaced μ-unbalanced production line. Unpaced line is referred to a line with workstations act independently and the material is not pulled by demand but in push mode. In this study, the production line is considered unpaced, μ-unbalanced but reliable. Mean processing time (μ) is the most difficult variable to fix constant in an actual production line due to the complexity of assembly process. The unbalance variance will become higher if the assembly process is more complex. The optimal buffer allocation need to be found for this particular type of production line so that it can maximize throughput rate and minimize total number of work-in-progress (WIP) on the line. This paper used a simulation method to simulate the throughput rate by given sets of buffer size. Based on the simulation results, a basic optimal buffer allocation (OBA) concept represented the characteristics of OBA for a production line was summarized. By applying the concept, a development of 6 Steps OBA tool is carried out. This tool could be utilized by a management in allocating the buffer during designing of the line layout.

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Kwon, Y. W., M. C. Murphy, and V. Castelli. "Buckling of Unbalanced, Sandwich Panels With Titanium and GRP Skins." Journal of Pressure Vessel Technology 117, no. 1 (February 1, 1995): 40–44. http://dx.doi.org/10.1115/1.2842088.

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An unbalanced and asymmetric sandwich composite structure consisting of Titanium 6-4 and glass-reinforced plastic (GRP) skins with a phenolic honeycomb core is being considered for construction of a surface ship mast which will enclose critical shipboard equipment. Stability of the structure is one of the major concerns in the design process. This research focuses on analytical and experimental studies of an unbalanced composite sandwich beam subjected to a compressive axial load. The failure load (i.e., peak load) and failure mode of each skin material and the sandwich construction were measured at the laboratory. An analytical model was developed for predicting the failure load of the unbalanced and asymmetric sandwich composite configuration, including the transverse shear energy of the core material. The experimental data agreed very well with analytical prediction. Postbuckling failure, as well as residual strength after initial failure, were also studied.

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Majdoub, Youssef, Ahmed Abbou, Mohamed Akherraz, and Rachid El Akhrif. "Design of an Improved MPPT Control of DFIG Wind Turbine under Unbalanced Grid Voltage using a Flux Sliding Mode Observer." International Journal of Power Electronics and Drive Systems (IJPEDS) 8, no. 4 (December 1, 2017): 1723. http://dx.doi.org/10.11591/ijpeds.v8.i4.pp1723-1731.

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This study presents a control scheme of the electronic interface of a grid connected Variable Speed Wind Energy Generation System (VS-WEGS) based on a Doubly Fed Induction Generator (DFIG). The efficiency of the wind energy is represented to according to the control strategy applied. Thus, in the case of unbalanced grid voltage, the negative sequence voltage causes additional strong oscillation at twice the grid frequency in the stator instantaneous active and reactive powers. The objective of this work is to present an enhanced MPPT controller uses backstepping approach implemented in both and reference frames rotating to keep a safe operation of DFIG during unbalanced grid voltage associated with regulating rotor flux, in order to estimate rotor flux, a nonlinear observer based on sliding mode is proposed in this work. Note that the conventional controllers (PI, PI-R …) are not provided satisfactory performance during unbalanced voltage dips. The validation of results has been performed through simulation studies on a 4 kW DFIG using Matlab/Simulink®.

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Zhang, Xuesong, Zhaoheng Wang, and Xinxiang Liu. "Analysis of noise during unbalanced braking of disc brake friction plates." Journal of Physics: Conference Series 2187, no. 1 (February 1, 2022): 012030. http://dx.doi.org/10.1088/1742-6596/2187/1/012030.

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Abstract The non-equilibrium contact phenomenon caused by the time difference between the friction plates on both sides and the brake disc during the braking process of the disc brake was analyzed. The brake noise problem in this non-simultaneous clamping condition was studied. Then a three-dimensional assembly model was established and the finite element method was used to find the complex mode and its instability coefficient under different operating conditions when t h e b r ak e w as in u n b al an ce d con ta ct. T he r esults s how th at during non-equilibrium braking, the inherent frequency and low-frequency stability of the braking system decreases, the instability modes increase significantly, and the shorter time difference leads to a strong tendency of whistling.

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Mohammadi Far, Somayeh, Matin Beiramvand, Mohammad Shahbakhti, and Piotr Augustyniak. "Prediction of Preterm Delivery from Unbalanced EHG Database." Sensors 22, no. 4 (February 15, 2022): 1507. http://dx.doi.org/10.3390/s22041507.

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Objective: The early prediction of preterm labor can significantly minimize premature delivery complications for both the mother and infant. The aim of this research is to propose an automatic algorithm for the prediction of preterm labor using a single electrohysterogram (EHG) signal. Method: The proposed method firstly employs empirical mode decomposition (EMD) to split the EHG signal into two intrinsic mode functions (IMFs), then extracts sample entropy (SampEn), the root mean square (RMS), and the mean Teager–Kaiser energy (MTKE) from each IMF to form the feature vector. Finally, the extracted features are fed to a k-nearest neighbors (kNN), support vector machine (SVM), and decision tree (DT) classifiers to predict whether the recorded EHG signal refers to the preterm case. Main results: The studied database consists of 262 term and 38 preterm delivery pregnancies, each with three EHG channels, recorded for 30 min. The SVM with a polynomial kernel achieved the best result, with an average sensitivity of 99.5%, a specificity of 99.7%, and an accuracy of 99.7%. This was followed by DT, with a mean sensitivity of 100%, a specificity of 98.4%, and an accuracy of 98.7%. Significance: The main superiority of the proposed method over the state-of-the-art algorithms that studied the same database is the use of only a single EHG channel without using either synthetic data generation or feature ranking algorithms.

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Zhang, Ben, Yu Li, Zhong Tang, Hao Zhang, Yaquan Liang, and Zhan Su. "Vortex Trajectory of Rotating Shaft Undergoing Vibration Coupling of Parallel Multicylinders." Advances in Materials Science and Engineering 2022 (January 22, 2022): 1–17. http://dx.doi.org/10.1155/2022/8184214.

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Multiple threshing cylinders of combine harvester are mainly driven in parallel, whose transmission methods are complex causing the excitations coupled with each other. The mutual excitation coupling of multiple threshing cylinders causes a severe vibration state of the combine harvester with poor stability. In order to analyze the influence of transmission system coupling on the unbalanced response of the parallel multicylinder system, this paper established a mathematical model of the parallel multicylinder system and derived the general vortex trajectory expression of the unbalanced response of threshing cylinder shaft undergoing vibration coupling of parallel multicylinders. Vibration tests of the bearing seat and the rotating shaft were carried out for comparison and verification. Results showed that the existence of the transmission chain and the transmission mode cause the boundary conditions of the multicylinder system to change, which ultimately led to changes in the unbalanced response of the transmission system. The contribution rate of different transmission methods and rotation speeds to the vibration amount at the fundamental frequency of the multicylinder was 5% to 30%. The existence of the transmission system caused the vibrations of the various units to be coupled with each other, mutually transmitted, and superimposed, leading to changes in the vortex shape of the rotating shaft and the unbalanced response of the transmission system.

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Marques, Carlos A. F., Martinho Marta-Almeida, and José M. Castanheira. "Three-dimensional normal mode functions: open-access tools for their computation in isobaric coordinates (p-3DNMF.v1)." Geoscientific Model Development 13, no. 6 (June 19, 2020): 2763–81. http://dx.doi.org/10.5194/gmd-13-2763-2020.

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Abstract. A free software package for the computation of the three-dimensional normal modes of an hydrostatic atmosphere is presented. This software performs the computations in isobaric coordinates and was developed for two user-friendly languages: MATLAB and Python. The software can be used to expand the global atmospheric circulation onto the 3-D normal modes. This expansion allows the computation of a 3-D energetic scheme, which partitions the energy reservoirs and energy interactions between 3-D spatial scales, barotropic and baroclinic components, and balanced (rotational) and unbalanced (divergent) circulation fields. Moreover, by retaining only a subset of the expansion coefficients, the 3-D normal mode expansion can be used for spatial-scale filtering of atmospheric motion, filtering of balanced motion and mass unbalanced motions, and barotropic and baroclinic components. Fixing the meridional scale, the 3-D normal mode filtering can be used to isolate tropical components of the atmospheric circulation. All of these features are useful both in data analysis and in assessment of general circulation atmospheric models.

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Huang, Ziyuan, Jiancheng Fang, and Kun Wang. "Dynamics of flexible rotor-shaft assembly with consideration of contact behaviors." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 229, no. 5 (June 12, 2014): 859–68. http://dx.doi.org/10.1177/0954406214539470.

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An approach is presented for large error problems of modal analysis of shaft assembly by considering contact behaviors of shaft components. The interference of shaft assembly is firstly calculated analytically through contact theory. The modal analysis of the finite element (FE) model of rotor-shaft assembly is executed by optimizing the normal contact stiffness factor (FKN). The accuracy of simulation results is verified in good agreement with experimental modal testing. The percentage errors of the first two bending natural frequencies are 1.3% and 2.8%, respectively. It is demonstrated that accurate mode of rotor-shaft assembly can be achieved. Then critical speeds of forward and backward are obtained by Campbell diagram. In particular, the amplitude-frequency response of rotor different element node under unbalanced vibration force is obtained by unbalance response analysis. It is important to improve the assembly’s structural integrity in order to minimize operational failure.

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Martinez, M. Itsaso, Ana Susperregui, Gerardo Tapia, and Haritza Camblong. "Sliding-Mode Control for a DFIG-based Wind Turbine under Unbalanced Voltage⋆." IFAC Proceedings Volumes 44, no. 1 (January 2011): 538–43. http://dx.doi.org/10.3182/20110828-6-it-1002.00854.

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Chunyan, Zang, and Liu Zhao. "Advanced compensation mode for cascade multilevel static synchronous compensator under unbalanced voltage." IET Power Electronics 8, no. 4 (April 2015): 610–17. http://dx.doi.org/10.1049/iet-pel.2014.0029.

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Xiong, Linyun, Penghan Li, and Jie Wang. "High-order sliding mode control of DFIG under unbalanced grid voltage conditions." International Journal of Electrical Power & Energy Systems 117 (May 2020): 105608. http://dx.doi.org/10.1016/j.ijepes.2019.105608.

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Ogunboyo, Patrick Taiwo, Remy Tiako, and Innocent E. Davidson. "Investigation of Voltage Unbalance Profile in Low Voltage Electrical Distribution Network with Normal Mode Operation Using MATLAB." International Journal of Engineering Research in Africa 35 (March 2018): 60–76. http://dx.doi.org/10.4028/www.scientific.net/jera.35.60.

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With ever increasing use of semiconductor devices and information technology (ICT) equipment in the industry, homes and offices, power quality is gaining attention to both industry and the electric utility. Power voltage quality cause huge economic losses to businesses all over the world. It is estimated to cost industry and commerce about €100 billion per annum in European Union, since voltage quality problem is one of the major power quality disturbances. This paper presents an investigative a study of the 11/0.4 kV, low voltage electrical distribution network and analyzes voltage unbalance. It recommends an effective method of improving the voltage profile and reducing the voltage unbalance to acceptable standard. The network was modelled using distribution network standard parameters for low voltage distribution network using MATLAB/Simulink sim power system tool box. The simulation results show that the percentage voltage unbalance, correct voltage profile and minimum voltage drop of 0.5 km distribution feeder line is of standard acceptable statutory limit, hence the distribution line operates at optimum performance. However, it is also established that the voltage profile for distribution network feeder lengths of 0.8 km to 5 km for balanced and unbalanced distribution lines from the beginning to the customer terminal of the distribution lengths are less than the acceptable allowable limit of – 5 %, of the nominal voltage value, hence voltages are inadmissible for customers use. Moreso, the percentage voltage unbalance, voltage profile and voltage drop on 0.8 km to 5 km distribution feeder line are all less than standard acceptable statutory limit, hence the distribution line operates below optimum performance. It was established that mitigating these problems require the electricity distribution company to install an effective voltage boosting devices along the network lengths in order provide admissible, permissible and normalize end users standard acceptable voltage.

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Quan, Yu, Lijun Hang, Yuanbin He, and Yao Zhang. "Multi-Resonant-Based Sliding Mode Control of DFIG-Based Wind System under Unbalanced and Harmonic Network Conditions." Applied Sciences 9, no. 6 (March 17, 2019): 1124. http://dx.doi.org/10.3390/app9061124.

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In general, the integral sliding mode control (ISMC) with an integral sliding surface would lead to tracking errors under unbalanced and harmonic grid voltage conditions. In order to eliminate tracking errors under these conditions, multi-resonant items are added to the conventional integral sliding surface in the proposed strategy, which can be called multi-resonant-based sliding mode control (MRSMC). A comparison of tracking precision on the ISMC and MRSMC is analyzed. In order to regulate the system powers directly, the errors of instantaneous active and reactive powers are selected as the state variables. Finally, the output current harmonics and a majority of the doubly-fed induction generator’s (DFIG) electromagnetic torque pulsations can be removed under unbalanced and harmonic grid voltage conditions. Simulation and experimental results are presented to verify the correctness and effectiveness of the proposed strategy.

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Yu, Zhi Yong, Ming Lu, Zhen Nan Wang, and Yi Gong Zhang. "A Droop Control Strategy with Impedance Compensation for Low Voltage Microgrid." Applied Mechanics and Materials 441 (December 2013): 245–48. http://dx.doi.org/10.4028/www.scientific.net/amm.441.245.

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With conventional droop control, parallel operation of distributed generations (DG) in microgrid would lead to unbalanced power sharing. In this paper, inherent limitation of conventional droop control is analyzed. Analysis results show that different converter output impedance and line impedance make the power sharing unbalanced. In order to weaken or eliminate impedance difference from point of common coupling (PCC) to DGs, virtual impedance is introduced. By the introduction of designed virtual impedance, a novel droop control strategy with impedance compensation is proposed in this paper. Simulation results are presented from a two converters parallel-connected microgrid, showing the effectiveness of the droop control with impedance compensation. Simulation results show that DGs with proposed approach can allocate the power equally, and work stably in grid-connected mode, island mode and progress of reconnection to grid.

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Ma, Mingxiang, Zhengliang Hu, Pan Xu, Wei Wang, and Yongming Hu. "Detecting mode hopping in single-longitudinal-mode fiber ring lasers based on an unbalanced fiber Michelson interferometer." Applied Optics 51, no. 30 (October 19, 2012): 7420. http://dx.doi.org/10.1364/ao.51.007420.

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Naumov, Igor, Sergey Podyachikh, Dmitri Ivanov, Alexander Tretyakov, and Andrey Bastron. "Analysis of unbalanced load low-voltage electrical networks operating modes." E3S Web of Conferences 295 (2021): 02005. http://dx.doi.org/10.1051/e3sconf/202129502005.

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The article discusses distribution electrical networks 0.38 kV operating modes, feeding individual residential buildings. The electrical energy parameters measurement were certified RESURS-UF2M device carried out. The currents and voltages time diagrams based on the measurements made and using Matlab technologies were constructed. It is established that the level of phase currents unbalance is quite high and causes significant three-phase power supply system unbalance voltage accordingly. The power of quality indicators - calculations, characterizing voltage unbalance were made, which were based on the measurements and the computer program “Asymmetry” was used. As well as the additional power losses coefficient determining by the phase currents unbalance, were calculations. Time diagrams these indicators are constructed and their analysis were made. As a result, the power of quality is significantly reduced by unbalance power consumption in the studied electrical network were founded. At the same time, the additional power losses are significant increases. Specific recommendations for the normalization electrical network-operating mode are given.

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Elnady, A., and Mohammad AlShabi. "Advanced exponential sliding mode control for microgrid at autonomous and grid-connected modes." Bulletin of Electrical Engineering and Informatics 10, no. 1 (February 1, 2021): 474–86. http://dx.doi.org/10.11591/eei.v10i1.2718.

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This paper introduces a novel control scheme for the operation of multilevel inverters forming a microgrid. The core of the suggested control scheme is an advanced (power-rate) exponential sliding mode controller. This developed controller is robust toward any variation of the system’s parameters and loads in addition to its fast and accurate performance. The presented control scheme provides advantageous characteristics to the microgrid operation in an autonomous mode (microgrid mode) and grid-connected mode. In the microgrid mode, the voltages and frequency are stable at any variable balanced and unbalanced load. In the grid-connected mode, an effective procedure for connecting the microgrid to the main grid is proposed to guarantee a seamless and fast transition to the grid-connected mode. The performance of the presented control scheme along with its proposed controller is validated by comparing its results to another linear and non-linear controllers for the same microgrid loading conditions.

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Hu, Guo, Qin Jun, Hai Wu, Song Hu, Lei Xia, Yajun Zhu, Zhihua Xu, and Jin Yu. "Fault Line Selection of Non-solidly Grounding System Based on EMD and Correlation Analysis of Zero Sequence Current Break-variable." Journal of Physics: Conference Series 2087, no. 1 (November 1, 2021): 012021. http://dx.doi.org/10.1088/1742-6596/2087/1/012021.

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Abstract When a single-phase grounding fault occurs in non-solidly grounding system, the zero sequence transient current is nonlinear and non-stationary. Especially when the resonant system is grounded with high resistance, the transient quantity is weak, which brings challenges to data processing. Therefore, empirical mode decomposition (EMD) is proposed to decompose the transient quantity and obtain different intrinsic mode functions (IMF). The IMF with the largest discrimination is selected as the characteristic quantity for correlation analysis. At the same time, considering the existence of unbalanced current in the actual system, in order to avoid the influence of unbalanced current, a single-phase grounding fault line selection algorithm based on EMD decomposition and correlation analysis of zero sequence current break-variable is proposed. Finally, the effectiveness of the method is verified by simulation and field test waveforms.

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Shen, I. Y., and C. P. R. Ku. "A Nonclassical Vibration Analysis of a Multiple Rotating Disk and Spindle Assembly." Journal of Applied Mechanics 64, no. 1 (March 1, 1997): 165–74. http://dx.doi.org/10.1115/1.2787269.

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This paper studies natural frequencies and mode shapes of a spinning disk/spindle assembly consisting of multiple elastic circular plates mounted on a rigid spindle that undergoes infinitesimal rigid-body translation and rotation. Through use of Lagrangian mechanics, linearized equations of motion are derived in terms of Euler angles, rigid-body translation, and elastic vibration modes of each disk. Compared with a single rotating disk whose spindle is fixed in space, the free vibration of multiple disks with rigid-body motion is significantly different in the following ways. First of all, lateral translation of the spindle, rigid-body rotation (or rocking) of the spindle, and one-nodal diameter modes of each disk are coupled together. When all the disks (say N disks) are identical, the coupled disk/spindle vibration splits into N − 1 groups of “balanced modes” and a group of “unbalanced modes.” For each group of the balanced modes, two adjacent disks vibrate entirely out of phase, while other disks undergo no deformation. Because the out-of-phase vibration does not change the angular momentum, the natural frequencies of the balanced modes are identical to those of the one-nodal-diameter modes of each disk. For the group of the unbalanced modes, all disks undergo the same out-of-plane vibration resulting in a change of angular momentum and a steady precession of the spindle. As a result, the frequencies of the unbalanced modes are significantly lower than those of one-nodal-diameter modes of each disk. Secondly, axial translation of the spindle and the axisymmetric modes of each disk are couple together. Similarly, the coupled motion split into N − 1 groups of “balanced modes” and one group of “unbalanced modes,” where the frequencies of the balanced and unbalanced modes are identical to and smaller than those of the axisymmetric modes of each disk, respectively. Thirdly, the rigid-body motion of the spindle does not affect disk vibration modes with two or more nodal diameters. Response of those modes can be determined through the classical vibration analysis of rotating disks. Moreover, vibration response of the disk/spindle assembly from a ground-based observer is derived. Finally, a calibrated experiment is conducted to validate the theoretical predictions.

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Tajik, Mohsen, and Ardeshir Karami Mohammadi. "Nonlinear vibration, stability, and bifurcation analysis of unbalanced spinning pre-twisted beam." Mathematics and Mechanics of Solids 24, no. 11 (May 23, 2019): 3514–36. http://dx.doi.org/10.1177/1081286519850604.

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In this paper, an Euler–Bernoulli model has been used for nonlinear vibration, stability, and bifurcation analysis of spinning twisted beams with linear twist angle, and with large transverse deflections, near the primary and parametric resonances. The equations of motion, in the case of pure single mode motion are analyzed by two methods: directly applying multiple scales method and using multiple scales method after discretization by Galerkin’s procedure. It is observed that the same final relations are obtained in the two methods. Effects of twist angle, damping ratio, longitudinal to transverse stiffness ratio, and eccentricity on the frequency responses are investigated. Then, the results are compared with the results obtained from Runge–Kutta numerical method on ODEs in a steady state, and confirmed with some previous research. Finally, the results show a good correlation, and it shows that with increasing the twist angle from 0 to 90°, the natural frequencies increase in the first two modes.

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Feng, Wenjie, Wenquan Che, Yongrong Shi, Quan Xue, Yuan Chun Li, and Xin Yu Zhou. "High Selectivity Balanced-to-Unbalanced Filtering Power Dividers Using Dual-Mode Ring Resonators." IEEE Transactions on Components, Packaging and Manufacturing Technology 9, no. 5 (May 2019): 927–35. http://dx.doi.org/10.1109/tcpmt.2018.2866129.

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Journal articles on the topic 'Unbalanced mode'

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