在“双碳”背景下,风电作为零碳电力和新能源发电的主力军,在助力社会全面绿色低碳转型方面发挥了关键性作用。在保证发电稳定的前提下实现风能的最大化利用,提升风力发电系统发电量至为重要。文中针对永磁同一步风力发电系统的最大功...在“双碳”背景下,风电作为零碳电力和新能源发电的主力军,在助力社会全面绿色低碳转型方面发挥了关键性作用。在保证发电稳定的前提下实现风能的最大化利用,提升风力发电系统发电量至为重要。文中针对永磁同一步风力发电系统的最大功率跟踪(maximum power point tracking, MPPT)问题进行研究。首先建立了永磁同步风力发电系统的机理仿真模型,用两电平双PWM全功率换流器连接风力发电机与电网。然后基于以上模型,分别设计了整数阶PI控制器、分数阶PI"控制器、模糊分数阶PP控制器以实现MPPT控制。最后对以上控制策略进行了仿真研究。结果表明,无论在阶跃风速还是随机风速下,模糊分数阶PU控制器相较于其他两种均具有更出色的MPPT性能与更强的鲁棒性。展开更多
Electromagnetic and mechanical forces are main reasons of oscillations in hydro-generators.The oscillation is fairly complicated as to the coupling of them.Using the method of multiple scales in nonlinear oscillations...Electromagnetic and mechanical forces are main reasons of oscillations in hydro-generators.The oscillation is fairly complicated as to the coupling of them.Using the method of multiple scales in nonlinear oscillations,instabilities of hydro-generator rotors caused by the unbalanced magnetic pull,which comes from the eccentricity of the rotor,are discussed.Considering nonlinear properties of the unbalanced magnetic pull,the super-harmonic resonance phenomena are observed as the critical rotating speed of rotors is close to twice of the operating speed.This is verified by a model experiment,and should be considered during the design of hydro-generator rotors.展开更多
Oxyfuel combustion with carbon capture and sequestration （CCS） is a carbon-reduction technology for use in large-scale coal-fired power plants. Significant progress has been achieved in the research and development ...Oxyfuel combustion with carbon capture and sequestration （CCS） is a carbon-reduction technology for use in large-scale coal-fired power plants. Significant progress has been achieved in the research and development of this technology during its scaling up from 0.4 MWth to 3 MWth and 35 aWth by the combined efforts of universities and industries in China. A prefeasibility study on a 200 MWe large-scale demonstration has progressed well, and is ready for implementation. The overall research development and demonstration （RD＆D） roadmap for oxyfuel combustion in China has become a critical component of the global RD＆D roadmap for oxyfuel combustion. An air combustion/oxyfuel combustion compatible design philosophy was developed during the RD＆D process. In this paper, we briefly address fundamental research and technology innovation efforts regarding several technical challenges, including combustion stability, heat transfer, system operation, mineral impurities, and corrosion. To further reduce the cost of carbon capture, in addition to the large-scale deployment of oxyfuel technology, increasing interest is anticipated in the novel and next- generation oxyfuel combustion technologies that are briefly introduced here, including a new oxygen-production concept and flameless oxyfuel combustion.展开更多
For efficient utilization of a limited geothermal resource in practical projects,the cycle parameters were comprehensively analyzed by combining with the heat transfer performance of the plate heat exchanger,with a va...For efficient utilization of a limited geothermal resource in practical projects,the cycle parameters were comprehensively analyzed by combining with the heat transfer performance of the plate heat exchanger,with a variation of flowrate of R245 fa.The influence of working fluid flowrate on a 500 W ORC system was investigated.Adjusting the working fluid flowrate to an optimal value results in the most efficient heat transfer and hence the optimal heat transfer parameters of the plate heat exchanger can be determined.Therefore,for the ORC systems,optimal working fluid flowrate should be controlled.Using different temperature hot water as the heat source,it is found that the optimal flowrate increases by 6-10 L/h with 5 ℃ increment of hot water inlet temperature.During experiment,lower degree of superheat of the working fluid at the outlet the plate heat exchanger may lead to unstable power generation.It is considered that the plate heat exchanger has a compact construction which makes its bulk so small that liquid mixture causes the unstable power generation.To avoid this phenomenon,the flow area of plate heat exchanger should be larger than the designed one.Alternatively,installing a small shell and tube heat exchanger between the outlet of plate heat exchanger and the inlet of expander can be another solution.展开更多
Remarkable improvement in efficiency and stability has been observed in a doped organic electroluminescence device, which consists of a hole-transport layer, an electron-transport layer and a luminescent layer. The ho...Remarkable improvement in efficiency and stability has been observed in a doped organic electroluminescence device, which consists of a hole-transport layer, an electron-transport layer and a luminescent layer. The hole-transport layer is a N,N’-bis(3-methyphenyl)-N,N’-diphenylbenzidine film. The doped emitting layer consists of 8-(quinolinolate)-aluminum as the host and rubrene as the emission dopant. The doped device demonstrated a brightness in excess of 40 000 cd/m 2 and the maximum external quantum efficiency of 3.4%, which is about six times and four times respectively greater than those of the undoped device. For no packaged deviced, a luminance half-life on the order of about 230 h has been achieved under a constant current density of 15 mA/cm 2, starting at 500 cd/m 2 at the room temperature.展开更多
Small-hydro power station is often used in remote areas beside a river,but it doesn't match electricity demand so well,especially in dry seasons. A photovoltaic (PV) system with battery is a suitable option to com...Small-hydro power station is often used in remote areas beside a river,but it doesn't match electricity demand so well,especially in dry seasons. A photovoltaic (PV) system with battery is a suitable option to complement the electricity gap. In this paper,a new structure of megawatt-class PV system integrating battery at DC-bus (DC: direct current) is proposed to be used in hydro/PV hybrid power system,and 4 main designing considerations and several key equipments are discussed. In 2011,a 2 MWp PV station with the proposed structure was built up in Yushu,China. From stability analysis,the station shows a strong stability under load cut-in/off and solar irradiance's fluctuation.展开更多
Permanent magnetic actuator （PMA）, as a new electronic actuator of vacuum circuit breakers, certainly will be used to replace the traditional mechanical actuator. It has such advantages as simple structure, high rel...Permanent magnetic actuator （PMA）, as a new electronic actuator of vacuum circuit breakers, certainly will be used to replace the traditional mechanical actuator. It has such advantages as simple structure, high reliability, free maintenance, and so on. This paper summarizes the development, structure, magnetic analysis, character analysis, and control strategy of PMA, and also predicts the future trend of PMA development展开更多
The impact of large-scale grid-connected PV （photovoltaics） on power system transient stability is discussed in this paper. In response to an increase of PV capacity, the capacity of conventional synchronous generat...The impact of large-scale grid-connected PV （photovoltaics） on power system transient stability is discussed in this paper. In response to an increase of PV capacity, the capacity of conventional synchronous generator needs to be reduced relatively. This leads to the lower system inertia and the higher generator reactance, and hence, the power system transient stability may negatively be affected. In particular, the impact on the transient stability may become more serious when the considerable amounts of PV systems are disconnected simultaneously during voltage sag. In this work, the potential impact of significant PV penetration on the transient stability is assessed by a numerical simulation using PSCAD/EMTDC.展开更多
The impact of large-scale grid-connected renewable power sources, such as wind generators and solar photovoitaic systems, on transient stability of synchronous generators is discussed in this paper. The permanent magn...The impact of large-scale grid-connected renewable power sources, such as wind generators and solar photovoitaic systems, on transient stability of synchronous generators is discussed in this paper. The permanent magnet synchronous generator with variable speed wind turbine is used in the simulation analysis as a wind generator model. The transient stability analysis is performed for IEEE 9-bus system model with high-penetration renewable power sources. The effect of FRT （fault ride-through） capability implemented for each power source on the transient stability is investigated.展开更多
文摘在“双碳”背景下,风电作为零碳电力和新能源发电的主力军,在助力社会全面绿色低碳转型方面发挥了关键性作用。在保证发电稳定的前提下实现风能的最大化利用,提升风力发电系统发电量至为重要。文中针对永磁同一步风力发电系统的最大功率跟踪(maximum power point tracking, MPPT)问题进行研究。首先建立了永磁同步风力发电系统的机理仿真模型,用两电平双PWM全功率换流器连接风力发电机与电网。然后基于以上模型,分别设计了整数阶PI控制器、分数阶PI"控制器、模糊分数阶PP控制器以实现MPPT控制。最后对以上控制策略进行了仿真研究。结果表明,无论在阶跃风速还是随机风速下,模糊分数阶PU控制器相较于其他两种均具有更出色的MPPT性能与更强的鲁棒性。
基金Sponsored by the National Natural Science Foundation of China(Grant No.59493700),Key Project of the National Tenth-Five Year Research Programme of China(Grant No.ZZ01-01-04-03).
文摘Electromagnetic and mechanical forces are main reasons of oscillations in hydro-generators.The oscillation is fairly complicated as to the coupling of them.Using the method of multiple scales in nonlinear oscillations,instabilities of hydro-generator rotors caused by the unbalanced magnetic pull,which comes from the eccentricity of the rotor,are discussed.Considering nonlinear properties of the unbalanced magnetic pull,the super-harmonic resonance phenomena are observed as the critical rotating speed of rotors is close to twice of the operating speed.This is verified by a model experiment,and should be considered during the design of hydro-generator rotors.
基金supported by the National Key Basic Research and Development Program (2011CB707301)the National Key Technology R&D Program (2011BAC05B00)+1 种基金the Specialized Research Fund for the Doctoral Program of Higher Education (20130142130009)the Fund of State Key Laboratory of Coal Combustion
文摘Oxyfuel combustion with carbon capture and sequestration （CCS） is a carbon-reduction technology for use in large-scale coal-fired power plants. Significant progress has been achieved in the research and development of this technology during its scaling up from 0.4 MWth to 3 MWth and 35 aWth by the combined efforts of universities and industries in China. A prefeasibility study on a 200 MWe large-scale demonstration has progressed well, and is ready for implementation. The overall research development and demonstration （RD＆D） roadmap for oxyfuel combustion in China has become a critical component of the global RD＆D roadmap for oxyfuel combustion. An air combustion/oxyfuel combustion compatible design philosophy was developed during the RD＆D process. In this paper, we briefly address fundamental research and technology innovation efforts regarding several technical challenges, including combustion stability, heat transfer, system operation, mineral impurities, and corrosion. To further reduce the cost of carbon capture, in addition to the large-scale deployment of oxyfuel technology, increasing interest is anticipated in the novel and next- generation oxyfuel combustion technologies that are briefly introduced here, including a new oxygen-production concept and flameless oxyfuel combustion.
基金Project (2012AA053001) supported by High-tech Research and Development Program of China
文摘For efficient utilization of a limited geothermal resource in practical projects,the cycle parameters were comprehensively analyzed by combining with the heat transfer performance of the plate heat exchanger,with a variation of flowrate of R245 fa.The influence of working fluid flowrate on a 500 W ORC system was investigated.Adjusting the working fluid flowrate to an optimal value results in the most efficient heat transfer and hence the optimal heat transfer parameters of the plate heat exchanger can be determined.Therefore,for the ORC systems,optimal working fluid flowrate should be controlled.Using different temperature hot water as the heat source,it is found that the optimal flowrate increases by 6-10 L/h with 5 ℃ increment of hot water inlet temperature.During experiment,lower degree of superheat of the working fluid at the outlet the plate heat exchanger may lead to unstable power generation.It is considered that the plate heat exchanger has a compact construction which makes its bulk so small that liquid mixture causes the unstable power generation.To avoid this phenomenon,the flow area of plate heat exchanger should be larger than the designed one.Alternatively,installing a small shell and tube heat exchanger between the outlet of plate heat exchanger and the inlet of expander can be another solution.
基金The National Natural Science Foundation of China , National "863" P
文摘Remarkable improvement in efficiency and stability has been observed in a doped organic electroluminescence device, which consists of a hole-transport layer, an electron-transport layer and a luminescent layer. The hole-transport layer is a N,N’-bis(3-methyphenyl)-N,N’-diphenylbenzidine film. The doped emitting layer consists of 8-(quinolinolate)-aluminum as the host and rubrene as the emission dopant. The doped device demonstrated a brightness in excess of 40 000 cd/m 2 and the maximum external quantum efficiency of 3.4%, which is about six times and four times respectively greater than those of the undoped device. For no packaged deviced, a luminance half-life on the order of about 230 h has been achieved under a constant current density of 15 mA/cm 2, starting at 500 cd/m 2 at the room temperature.
基金Chinese Academy of Science (No.KGCX2- YW- 366)Ministry of Science and Technology(No. 2011AA05A106)
文摘Small-hydro power station is often used in remote areas beside a river,but it doesn't match electricity demand so well,especially in dry seasons. A photovoltaic (PV) system with battery is a suitable option to complement the electricity gap. In this paper,a new structure of megawatt-class PV system integrating battery at DC-bus (DC: direct current) is proposed to be used in hydro/PV hybrid power system,and 4 main designing considerations and several key equipments are discussed. In 2011,a 2 MWp PV station with the proposed structure was built up in Yushu,China. From stability analysis,the station shows a strong stability under load cut-in/off and solar irradiance's fluctuation.
文摘Permanent magnetic actuator （PMA）, as a new electronic actuator of vacuum circuit breakers, certainly will be used to replace the traditional mechanical actuator. It has such advantages as simple structure, high reliability, free maintenance, and so on. This paper summarizes the development, structure, magnetic analysis, character analysis, and control strategy of PMA, and also predicts the future trend of PMA development
文摘The impact of large-scale grid-connected PV （photovoltaics） on power system transient stability is discussed in this paper. In response to an increase of PV capacity, the capacity of conventional synchronous generator needs to be reduced relatively. This leads to the lower system inertia and the higher generator reactance, and hence, the power system transient stability may negatively be affected. In particular, the impact on the transient stability may become more serious when the considerable amounts of PV systems are disconnected simultaneously during voltage sag. In this work, the potential impact of significant PV penetration on the transient stability is assessed by a numerical simulation using PSCAD/EMTDC.
文摘The impact of large-scale grid-connected renewable power sources, such as wind generators and solar photovoitaic systems, on transient stability of synchronous generators is discussed in this paper. The permanent magnet synchronous generator with variable speed wind turbine is used in the simulation analysis as a wind generator model. The transient stability analysis is performed for IEEE 9-bus system model with high-penetration renewable power sources. The effect of FRT （fault ride-through） capability implemented for each power source on the transient stability is investigated.
