This paper presents an efficient technique for processing of 3D meshed surfaces via spherical wavelets. More specifically, an input 3D mesh is firstly transformed into a spherical vector signal by a fast low distortio...This paper presents an efficient technique for processing of 3D meshed surfaces via spherical wavelets. More specifically, an input 3D mesh is firstly transformed into a spherical vector signal by a fast low distortion spherical parameterization approach based on symmetry analysis of 3D meshes. This signal is then sampled on the sphere with the help of an adaptive sampling scheme. Finally, the sampled signal is transformed into the wavelet domain according to spherical wavelet transform where many 3D mesh processing operations can be implemented such as smoothing, enhancement, compression, and so on. Our main contribution lies in incorporating a fast low distortion spherical parameterization approach and an adaptive sampling scheme into the frame for pro- cessing 3D meshed surfaces by spherical wavelets, which can handle surfaces with complex shapes. A number of experimental ex- amples demonstrate that our algorithm is robust and efficient.展开更多
The Smart Transformer (ST) is a solid-state transformer with control and communication functionalities, interfacing medium voltage and low voltage (LV) grids. The ST can work in both ways: it can operate in a radial n...The Smart Transformer (ST) is a solid-state transformer with control and communication functionalities, interfacing medium voltage and low voltage (LV) grids. The ST can work in both ways: it can operate in a radial network independently, and it also provides meshed operation. In particular, a meshed ST-fed grid is able to optimize the power flow of the network, therefore largely avoiding the reinforcement of utilities. Though the ST can address system-level issues, challenges in terms of control and stability are encountered. The modeling as well as stability analysis of ST converter and its control for meshed operation have rarely been studied. More importantly, the interactions between ST and grid-interfaced converters during meshed operation have not yet been investigated. To ensure reliable ST-fed grid, this paper develops a complete model of ST LV converter considering all the key elements for the meshed operation. System stability is assessed based on the developed model for different scenarios. The interactions between the ST and local grid converters are examined to provide comprehensive design guidelines for the meshed ST-fed grid. The control strategy and the theoretical analysis are validated by the simulation and experimental results.展开更多
The Smart Transformer(ST)is a solid-state transformer with control and communication functionalities,interfacing medium voltage and low voltage grids.The ST can independently operate in a radial network configuration,...The Smart Transformer(ST)is a solid-state transformer with control and communication functionalities,interfacing medium voltage and low voltage grids.The ST can independently operate in a radial network configuration,and also in a meshed grid operation.The meshed operation has high potential to optimize the power flow in the network,avoiding or postponing the reinforcement of distribution grids.Nevertheless,the control and synchronization during the meshed operation are not trivial.The perturbation of the voltage in transition between the two operations is inevitable.This could lead to uncontrolled power flow and endanger the meshed operation.Moreover,the stability of the meshed grid has seldom been studied.To address these issues,this paper proposes a voltage control with power-based synchronization for the ST.This allows the universal operation of both radial and meshed grids,while ensuring smooth transition.Modeling and stability analysis of such a system are investigated to make sure of safe operation.Simulation and experimental results are provided to validate the effectiveness of the proposed control and theoretical analysis.展开更多
This paper proposes the design of a novel DC current flow controller(CFC)and evaluates the control performance of balancing and regulating the DC branch currents using the DC CFC in a meshed multi-terminal HVDC(MTDC)g...This paper proposes the design of a novel DC current flow controller(CFC)and evaluates the control performance of balancing and regulating the DC branch currents using the DC CFC in a meshed multi-terminal HVDC(MTDC)grid.The DC CFC consists of two identical full bridge DC-DC converters with the capacitors of the two converters being connected in parallel.The scalability of the DC CFC is easily achievable due to the identical bridge converter topology;the cost of this DC CFC is also relatively low due to its simple physical structure and low voltage ratings.The control performance of the DC CFC is tested on a meshed 3-terminal(3-T)HVDC grid,which is based on modular multilevel converters(MMC).The DC branch current control in the meshed MTDC grid is achieved using the proposed control strategy of the DC CFC,and is verified through case studies on the real-time digital simulator(RTDS).展开更多
Based on the comparison of existing power flow controllers(PFC)in meshed HVDC grids,the full-bridge modular multilevel converter based PFC(MMPFC)is proposed.At first,the general branch current calculation method of me...Based on the comparison of existing power flow controllers(PFC)in meshed HVDC grids,the full-bridge modular multilevel converter based PFC(MMPFC)is proposed.At first,the general branch current calculation method of meshed HVDC grids with the PFC is presented,and then,the issue of over-voltage on the thyristor based PFC is described and analyzed.Through the analysis of different operating modes of the full-bridge sub-module,the mechanism of over-voltage ride through of the MMPFC is indicated.The control strategy of the MMPFC,which is used to control branch current and keep capacitor voltage balancing,is elaborated.Finally,the performance on current regulation,bidirectional operation and over-voltage ride through is simulated and verified in a built model with PSCAD/EMTDC.展开更多
基金Supported by the National Natural Science Foundation of China(No.61173102)the NSFC Guangdong Joint Fund(No.U0935004)+2 种基金the Fundamental Research Funds for the Central Universities(No.DUT11SX08)the Opening Foundation of Key Laboratory of Symbolic Computation and Knowledge Engineering of Ministry of Education of China(No.93K172012K02)the Doctor Research Start-up Fund of North East Dian Li university(No.BSJXM-200912)
文摘This paper presents an efficient technique for processing of 3D meshed surfaces via spherical wavelets. More specifically, an input 3D mesh is firstly transformed into a spherical vector signal by a fast low distortion spherical parameterization approach based on symmetry analysis of 3D meshes. This signal is then sampled on the sphere with the help of an adaptive sampling scheme. Finally, the sampled signal is transformed into the wavelet domain according to spherical wavelet transform where many 3D mesh processing operations can be implemented such as smoothing, enhancement, compression, and so on. Our main contribution lies in incorporating a fast low distortion spherical parameterization approach and an adaptive sampling scheme into the frame for pro- cessing 3D meshed surfaces by spherical wavelets, which can handle surfaces with complex shapes. A number of experimental ex- amples demonstrate that our algorithm is robust and efficient.
基金supported in part by the National Natural Science Foundation of China under Grant 52377171in part by the Fundamental Research Funds for the Central Universities under Grant 2242024K40030.
文摘The Smart Transformer (ST) is a solid-state transformer with control and communication functionalities, interfacing medium voltage and low voltage (LV) grids. The ST can work in both ways: it can operate in a radial network independently, and it also provides meshed operation. In particular, a meshed ST-fed grid is able to optimize the power flow of the network, therefore largely avoiding the reinforcement of utilities. Though the ST can address system-level issues, challenges in terms of control and stability are encountered. The modeling as well as stability analysis of ST converter and its control for meshed operation have rarely been studied. More importantly, the interactions between ST and grid-interfaced converters during meshed operation have not yet been investigated. To ensure reliable ST-fed grid, this paper develops a complete model of ST LV converter considering all the key elements for the meshed operation. System stability is assessed based on the developed model for different scenarios. The interactions between the ST and local grid converters are examined to provide comprehensive design guidelines for the meshed ST-fed grid. The control strategy and the theoretical analysis are validated by the simulation and experimental results.
基金supported by the National Natural Science Foundation of China under Grant 52377171.
文摘The Smart Transformer(ST)is a solid-state transformer with control and communication functionalities,interfacing medium voltage and low voltage grids.The ST can independently operate in a radial network configuration,and also in a meshed grid operation.The meshed operation has high potential to optimize the power flow in the network,avoiding or postponing the reinforcement of distribution grids.Nevertheless,the control and synchronization during the meshed operation are not trivial.The perturbation of the voltage in transition between the two operations is inevitable.This could lead to uncontrolled power flow and endanger the meshed operation.Moreover,the stability of the meshed grid has seldom been studied.To address these issues,this paper proposes a voltage control with power-based synchronization for the ST.This allows the universal operation of both radial and meshed grids,while ensuring smooth transition.Modeling and stability analysis of such a system are investigated to make sure of safe operation.Simulation and experimental results are provided to validate the effectiveness of the proposed control and theoretical analysis.
基金supported by UK-China Smart Grid Project ERIFT via UK EPSRC,University of Birmingham SiGuang Li Scholarship and China Scholarship Council。
文摘This paper proposes the design of a novel DC current flow controller(CFC)and evaluates the control performance of balancing and regulating the DC branch currents using the DC CFC in a meshed multi-terminal HVDC(MTDC)grid.The DC CFC consists of two identical full bridge DC-DC converters with the capacitors of the two converters being connected in parallel.The scalability of the DC CFC is easily achievable due to the identical bridge converter topology;the cost of this DC CFC is also relatively low due to its simple physical structure and low voltage ratings.The control performance of the DC CFC is tested on a meshed 3-terminal(3-T)HVDC grid,which is based on modular multilevel converters(MMC).The DC branch current control in the meshed MTDC grid is achieved using the proposed control strategy of the DC CFC,and is verified through case studies on the real-time digital simulator(RTDS).
基金supported by the National High Technology Research and Development Program of China("863"Program)(Grant No.2012AA050205)
文摘Based on the comparison of existing power flow controllers(PFC)in meshed HVDC grids,the full-bridge modular multilevel converter based PFC(MMPFC)is proposed.At first,the general branch current calculation method of meshed HVDC grids with the PFC is presented,and then,the issue of over-voltage on the thyristor based PFC is described and analyzed.Through the analysis of different operating modes of the full-bridge sub-module,the mechanism of over-voltage ride through of the MMPFC is indicated.The control strategy of the MMPFC,which is used to control branch current and keep capacitor voltage balancing,is elaborated.Finally,the performance on current regulation,bidirectional operation and over-voltage ride through is simulated and verified in a built model with PSCAD/EMTDC.
