Both the real part and imaginary part of complex permittivity approximately have a log-linear frequency dependency at low fre- quencies, especially at ultra-low frequencies under conditions of different moisture conce...Both the real part and imaginary part of complex permittivity approximately have a log-linear frequency dependency at low fre- quencies, especially at ultra-low frequencies under conditions of different moisture concentrations and temperatures, which is recognized as the low frequency dispersion (LFD). In order to explain this dispersion, a new mechanism of dielectric response of LFD of oil-paper insula- tion is proposed. A simplified one-dimensional mathematical model of concentration polarization carrier caused by slow migration is developed and solved, which indicates that ion mobility is closely related to the size of gap and the adsorption capacity of cellulose molecu- lar chains to ions. A stochastic statistical model of the carrier mobility induced LFD is also developed. Moreover, actual tests under 50 °C and 2% moisture content were put forward, as well as simulations with according current waveforms. The simulation results agreed well with the experimental data in that concentration polarization of carriers caused by slow migration is the probable cause of low frequency dispersion of dielectric response for oil-paper insulation diagnosis.展开更多
风电机组一般通过综合惯量控制提供辅助调频,然而其调频效果受控制参数影响较大。文中综合考虑风电机组自身可调能力与系统频率响应指标,对风电调频参数整定进行研究。首先,建立计及风电和火电参与调频的系统频率响应(system frequency ...风电机组一般通过综合惯量控制提供辅助调频,然而其调频效果受控制参数影响较大。文中综合考虑风电机组自身可调能力与系统频率响应指标,对风电调频参数整定进行研究。首先,建立计及风电和火电参与调频的系统频率响应(system frequency response,SFR)模型,并推导频率响应指标的解析式。其次,对风电机组的转子运动方程进行线性化并建立转速模型,在不同风速工况下验证其准确性。然后,以提升系统频率最低点为目标,同时考虑风电机组转速下限和系统频率安全约束,整定其控制参数。最后,仿真结果验证所提风电调频控制参数整定方法在不同风电渗透率以及功率扰动下,均能够在确保系统频率安全的前提下充分利用风电机组的转子动能。展开更多
新型电力系统面临惯性降低、调频容量减少导致频率失稳风险上升的问题,需求侧响应(demand response,DR)作为灵活的调频技术,成为解决电力系统频率失稳的重要手段。首先,建立需求侧资源参与互联电力系统调频的频率稳定分析及负荷频率控制...新型电力系统面临惯性降低、调频容量减少导致频率失稳风险上升的问题,需求侧响应(demand response,DR)作为灵活的调频技术,成为解决电力系统频率失稳的重要手段。首先,建立需求侧资源参与互联电力系统调频的频率稳定分析及负荷频率控制(load frequency control,LFC)模型;其次,设计需求侧资源参与互联电力系统调频的分布式模型预测控制(distributed model predictive control,DMPC)算法,推导DMPC控制DR参与互联电力系统调频的预测模型,进而设计互联电力系统DMPC的调频控制器;最后,仿真分析自动发电控制方式、DR方式、DR容量和DR通信延时对系统频率稳定性的影响。仿真算例表明,所设计的调频控制器具有良好的调频性能,DR能提升系统频率暂态稳定。展开更多
基金Project supported by National Nature Science Foundation of China （51107105）, Sichuan Science Fund for Young Scholars （2011JQ0009）.
文摘Both the real part and imaginary part of complex permittivity approximately have a log-linear frequency dependency at low fre- quencies, especially at ultra-low frequencies under conditions of different moisture concentrations and temperatures, which is recognized as the low frequency dispersion (LFD). In order to explain this dispersion, a new mechanism of dielectric response of LFD of oil-paper insula- tion is proposed. A simplified one-dimensional mathematical model of concentration polarization carrier caused by slow migration is developed and solved, which indicates that ion mobility is closely related to the size of gap and the adsorption capacity of cellulose molecu- lar chains to ions. A stochastic statistical model of the carrier mobility induced LFD is also developed. Moreover, actual tests under 50 °C and 2% moisture content were put forward, as well as simulations with according current waveforms. The simulation results agreed well with the experimental data in that concentration polarization of carriers caused by slow migration is the probable cause of low frequency dispersion of dielectric response for oil-paper insulation diagnosis.
文摘风电机组一般通过综合惯量控制提供辅助调频,然而其调频效果受控制参数影响较大。文中综合考虑风电机组自身可调能力与系统频率响应指标,对风电调频参数整定进行研究。首先,建立计及风电和火电参与调频的系统频率响应(system frequency response,SFR)模型,并推导频率响应指标的解析式。其次,对风电机组的转子运动方程进行线性化并建立转速模型,在不同风速工况下验证其准确性。然后,以提升系统频率最低点为目标,同时考虑风电机组转速下限和系统频率安全约束,整定其控制参数。最后,仿真结果验证所提风电调频控制参数整定方法在不同风电渗透率以及功率扰动下,均能够在确保系统频率安全的前提下充分利用风电机组的转子动能。
文摘新型电力系统面临惯性降低、调频容量减少导致频率失稳风险上升的问题,需求侧响应(demand response,DR)作为灵活的调频技术,成为解决电力系统频率失稳的重要手段。首先,建立需求侧资源参与互联电力系统调频的频率稳定分析及负荷频率控制(load frequency control,LFC)模型;其次,设计需求侧资源参与互联电力系统调频的分布式模型预测控制(distributed model predictive control,DMPC)算法,推导DMPC控制DR参与互联电力系统调频的预测模型,进而设计互联电力系统DMPC的调频控制器;最后,仿真分析自动发电控制方式、DR方式、DR容量和DR通信延时对系统频率稳定性的影响。仿真算例表明,所设计的调频控制器具有良好的调频性能,DR能提升系统频率暂态稳定。
