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Stochastic processes in renewable power systems: From frequency domain to time domain

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Science China(Technological Sciences) 2019年第12期62卷 2093-2103页

作者： SONG YongHua CHEN XiaoShuang LIN Jin LIU Feng QIU YiWei Department of Electrical and Computer Engineering University of MacaoMacaoChina State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Department of Electrical EngineeringTsinghua UniversityBeijing 100084China

With the increasing penetration of renewable energy resources(RESs), the uncertainties of volatile renewable generations significantly affect the power system operation. Such uncertainties are usually modeled as stochastic variables obeying specific distributions by neglecting the temporal correlations. Conventional approaches to hedge the negative effects caused by such uncertainties are thus hard to pursue a trade-off between computation efficiency and optimality. As an alternative, the theory of stochastic process can naturally model temporal correlation in closed forms. Attracted by this feature, our research group has been conducting thorough researches in the past decade to introduce stochastic processes within renewable power systems. This paper summarizes our works from the perspective of both the frequency domain and the time domain, provides the tools for the analysis and control of power systems under a unified framework of stochastic processes, and discusses the underlying reasons that stochastic process-based approaches can perform better than conventional approaches on both computational efficiency and optimality. These work may shed a new light on the research of analysis, control and operation of renewable power ***, this paper outlooks the theoretic developments of stochastic processes in future’s renewable power systems.

关键词： renewable energy resources renewable power systems stochastic processes frequency domain time domain

NUMERICAL SIMULATIONS OF WAVE-INDUCED SHIP MOTIONS IN time domain BY A RANKINE PANEL METHOD

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Journal of Hydrodynamics 2010年第3期22卷 373-380页

作者： CHEN Jing-pu ZHU De-xiang China Ship Scientific Research Center Shanghai 214082 China Shanghai Institute of Computing Technology Shanghai 200040 China

A time domain prediction of wave-induced ship motions by a Rankine panel method is investigated. Linear boundary conditions on free surface and mean wetted body surface are adopted, while the numerical damping method is used for the radiation conditions. The motions of two ships in regular head waves are computed by the present method. The related numerical results are compared with the experiment data and those from linear strip theory. The comparison shows satisfactory agreements for pitch and heave transfer functions.

关键词： Rankine source panel method time domain ship motion forward speed

COMPUTATIONAL RESEARCH ON WAVE MAKING OF MOVING WIGLEY HULL IN time domain

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Journal of Hydrodynamics 2008年第4期20卷 469-476页

作者： YANG Xiang-hui YE Heng-kui FENG Da-kui LIU Juan College of Traffic Science and Engineering Huazhong University of Science and Technology Wuhan 430074 China Ship Information Center Beijing 100085 China

Based on Green＇s theorem, a time domain numerical model was constructed to simulate wave making phenomenon caused by a moving ship. In this article, the Rankine sources and dipoles were placed on boundary surfaces （i.e., the ship surface and free surface）, and a time-stepping scheme was employed. Its unique characteristic is that steady state can be realized from initial value by employing the time-stepping scheme and unsteady free surface conditions. In time domain, if the results of unsteady flow problem tend to data stabilization after many time steps of computation, they could be regarded as the data of steady ones. This model could be employed to steady or unsteady problems. Theoretical reasoning and computational process of this method was described in detail The linear and nonlinear boundary conditions on body surface were studied, and the relative means to realize these boundary conditions in iterative computation were also discussed. Some proper parameters about the model of the Wigley hull were determined by many numerical tests, and their influences on wave making resistance and wave pattern were discussed. According to the comparison between numerical results and data available in relative references, the method used in this work is proven to be a reliable method in time domain. And the lattice reorganization in every time step computation is a feasible numerical approach.

关键词： Rankine source dipole time domain Wigley hull lattice reorganization time-stepping scheme Green's theorem

Finite element analysis of second order wave radiation by a group of cylinders in the time domain

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Journal of Hydrodynamics 2013年第3期25卷 348-361页

作者：王赤忠 MITRA Santanu 黄豪彩 KHOO Boo-cheong Department of Ocean Science and Engineering Zhejiang University Department of Mechanical Engineering National University of Singapore Singapore 119260 Singapore

A finite element based numerical method is employed to analyze the wave radiation by multiple or a group of cylinders in the time domain. The nonlinear free surface and body surface boundary conditions are satisfied based on the perturbation method up to the second order. The first- and second-order velocity potential problems at each time step are solved through a Finite Element Method （FEM）. The matrix equation of the FEM is solved through iteration and the initial solution is obtained from the result at the previous time step. The three-dimensional （3-D） mesh required is generated based on a two-dimensional （2-D） hybrid mesh on a horizontal plane and its extension in the vertical direction. The hybrid mesh is generated by combining an unstructured grid away from cylinders and two structured grids near the cylinder and the artificial boundary. The fluid velocity on the free surface and the cylinder surface are calculated by using a differential method. Results for various configurations including the cases of two cylinders and four cylinders and a group of eighteen cylinders are obtained to show the joint influences of cylinders on the first- and second- order waves and forces, including the effects of spacing ratios and wave frequency on the second order waves and the mean force, in particular.

关键词： second order wave radiation time domain a group of cylinders finite element method unstructured mesh

Statistical moment-based structural damage detection method in time domain

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Earthquake Engineering and Engineering Vibration 2013年第1期12卷 13-23页

作者： J.Zhang Y.L.Xu J.Li Y.Xia J.C.Li Department of Civil and Environmental Engineering The Hong Kong Polytechnic University Department of Building Engineering Tongji University Faculty of Engineering University of Technology Sydney

A novel structural damage detection method with a new damage index,i.e.,the statistical moment-based damage detection（SMBDD） method in the frequency domain,has been recently *** aim of this study is to extend the SMBDD method in the frequency domain to the time domain for building structures subjected to non-Gaussian and non-stationary *** applicability and effectiveness of the SMBDD method in the time domainis verified both numerically and *** buildings with various damage scenarios are first numerically investigated in the time domain taking into account the effect of measurement *** applicability of the proposed method in the time domain to building structures subjected to non-Gaussian and non-stationary excitations is then experimentally investigated through a series of shaking table tests,in which two three-story shear building models with four damage scenarios *** identified damage locations and severities are then compared with the preset *** comparative results are found to be satisfactory,and the SMBDD method is shown to be feasible and effective for building structures subjected to non-Gaussian and non-stationary excitations.

关键词： damage detection statistical moment time domain non-Gaussian non-stationary experimental investigation

A time domain INVESTIGATION ON THE HYDRODYNAMIC RESONANCE PHENOMENA OF 3-D MULTIPLE FLOATING STRUCTURES

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Journal of Hydrodynamics 2008年第5期20卷 611-616页

作者： ZHU Hai-rong ZHU Ren-chuan MIAO Guo-ping The State Key Laboratory of Ocean Engineering School of Naval Architecture Ocean and Civil Engineering Shanghai Jiao Tong University Shanghai 200030 China

A 3-D time domain method is developed to investigate the gap influence on the wave threes for 3-D multiple floating structures. Special hydrodynamic resonance due to small gaps between multiple floating structures on wave forces is examined. Strong and complicate hydrodynamic interactions between the floating bodies are observed and the numerical computations have proved the existence of the sharp peak force response on each floating body at some special resonant wave numbers. By comparison with the results from the frequency domain technique, the results obtained from the time domain method reveal the similar resonant phenomena and hydrodynamic interaction. The resonant wave numbers are also proved around kL-nπ （n = 1,2 ……∞） with a corresponding frequency shift. The strong hydrodynamic interaction feature is practically significant for the design of module structures and the links （connection） in whole the floating body system.

关键词： time domain resonance hydrodynamic interaction multiple floating bodies gap influence

An Approximation to Energy Dissipation in time domain Simulation of Sloshing Waves Based on Linear Potential Theory

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China Ocean Engineering 2011年第2期25卷 189-200页

作者：黄硕段文洋马庆位 College of Shipbuilding Engineering Harbin Engineering University School of Engineering and Mathematical Sciences

This paper proposes a new approximation to energy dissipation in time domain simulation of sloshing waves by use of a linear potential theory. The boundary value problem is solved by the NURBS （non-uniform rational B-spline） higher-order panel method, in which a time-domain Green function is employed. The energy dissipation is modeled by changing the boundary condition on solid boundaries. Model experiments are carried out in a partially filled rectangular tank with forced horizontal motion. Sloshing-induced internal pressures and horizontal force obtained numerically and experimentally are compared with each other. It is observed that the present energy dissipation approximation can help produce a fair agreement between experimental forces and those of numerical simulations.

关键词： tank sloshing energy dissipation NURBS higher-order method time domain

Prediction of Non-Cavitation Propeller Noise in time domain

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China Ocean Engineering 2011年第3期25卷 531-538页

作者：叶金铭熊鹰肖昌润毕毅 College of Naval Architecture and Power Naval University of Engineering The Ministry of Education Key Laboratory of High Speed Ship Engineering Wuhan University of Technology

The blade frequency noise of non-cavitation propeller in a uniform flow is analyzed in time domain. The unsteady loading （dipole source） on the blade surface is calculated by a potential-based surface panel method. Then the time- dependent pressure data is used as the input for Ffowcs Williams-Hawkings formulation to predict the acoustics pressure. The integration of noise source is performed over the true blade surface rather than the nothickness blade surface, and the effect of hub can be considered. The noise characteristics of the non-cavitation propeller and the numerical discretization forms are discussed.

关键词： propeller surface panel method, noise time domain

Frequency/time domain modeling of a direct drive point absorber wave energy converter

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Science China(Physics,Mechanics & Astronomy) 2014年第2期57卷 311-320页

作者： CHENG ZhengShun YANG JianMin HU ZhiQiang XIAO LongFei State Key Lab of Ocean Engineering Shanghai Jiao Tong University

Two different methods to model a point absorber wave energy converter （WEC） with direct drive linear power take-off （PTO） are proposed in the present study： the frequency domain （FD） method and the time domain （TD） method. In the FD analysis, the frequency response function （FRF） of the WEC device is obtained via the equation of motion, and the expressions of power capture width in regular and random waves are derived as well. In the TD modeling, based on a state space approximation of the convolution term in the motion equation, both regular wave and random wave simulations are carded out. The regular wave simulation results indicate that the state space approximation is sufficiently accurate and the capture width reaches the maximum in the vicinity of the natural frequency. In the random wave simulations, the effects of buoy size, the PTO damping and wave climate on the power capture width are discussed in detail, which leads to the conclusion that the capture widths are influenced by the natural frequency of the WEC device, peak frequency of the wave spectrum, the amplitude of FRF and PTO damping. Furthermore, the increase of the capture width is at the cost of a relatively large buoy size and PTO damping when control is not included.

关键词： wave energy converter frequency domain time domain power capture width power take-off damping