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
Increased renewable energy integration and international power trades have led to the construction and development of new HVDC transmission systems.HVDC cables,in particular,play an important role in undersea power tr...Increased renewable energy integration and international power trades have led to the construction and development of new HVDC transmission systems.HVDC cables,in particular,play an important role in undersea power transmission and offshore renewable energy integration having lower losses and higher reliability.In this paper,the current commercial feasibility of HVDC cables and the development of different types of HVDC cables and accessories are reviewed.The non-uniform electric field distribution caused by the applied voltage,temperature dependent conductivity,and space charge accumulation is briefly discussed.Current research in HVDC cable for higher operation voltage level and larger power capacity is also reviewed with specific focus on the methodologies of space charge suppression for XLPE extruded cables.展开更多
In this study, an improved trapping/detrapping model was used to simulate the charge dynamics in cross-linkedpolyethylene peelings from different-year aged cables. Injection barrier of trapping parameters was estimate...In this study, an improved trapping/detrapping model was used to simulate the charge dynamics in cross-linkedpolyethylene peelings from different-year aged cables. Injection barrier of trapping parameters was estimated by themodel fitted to experimental data for each type of sample. Moreover, dc breakdown tests were operated on thosesamples. It has been found that the dc breakdown strength of inner-layer samples is the lowest in cable sections withthicker insulation layer taken from high-voltage ac (HVAC) 220 kV service condition, whereas for the cable with thinnerinsulation from HVAC 110 kV, middle-layer samples have worst breakdown performance. This might be explained bythe space charge issues under long-term HVAC condition. More importantly, a clear relationship between estimatedmodel parameters, including injection barrier, trap depth and trap density, with the dc breakdown strength in eachlayer has been reported in this study.展开更多
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 State Grid Corporation of China:Research on Key Technologies of Insulation Material and Accessories for 320 kV HVDC XLPE Cable System(SGRIZLJS(2014)888).
文摘Increased renewable energy integration and international power trades have led to the construction and development of new HVDC transmission systems.HVDC cables,in particular,play an important role in undersea power transmission and offshore renewable energy integration having lower losses and higher reliability.In this paper,the current commercial feasibility of HVDC cables and the development of different types of HVDC cables and accessories are reviewed.The non-uniform electric field distribution caused by the applied voltage,temperature dependent conductivity,and space charge accumulation is briefly discussed.Current research in HVDC cable for higher operation voltage level and larger power capacity is also reviewed with specific focus on the methodologies of space charge suppression for XLPE extruded cables.
基金the financial support from the State Grid Cooperation of China:Research on Key Technologies of Insulation Material and Accessories for 320 kV HVDC XLPE Cable System(SGRIZLJS(2014)888).
文摘In this study, an improved trapping/detrapping model was used to simulate the charge dynamics in cross-linkedpolyethylene peelings from different-year aged cables. Injection barrier of trapping parameters was estimated by themodel fitted to experimental data for each type of sample. Moreover, dc breakdown tests were operated on thosesamples. It has been found that the dc breakdown strength of inner-layer samples is the lowest in cable sections withthicker insulation layer taken from high-voltage ac (HVAC) 220 kV service condition, whereas for the cable with thinnerinsulation from HVAC 110 kV, middle-layer samples have worst breakdown performance. This might be explained bythe space charge issues under long-term HVAC condition. More importantly, a clear relationship between estimatedmodel parameters, including injection barrier, trap depth and trap density, with the dc breakdown strength in eachlayer has been reported in this study.