Based on the characteristic of AC-excited variable speed constant frequency(VSCF)wind power generation,the vector control technique was applied in a doubly fed induction generator(DFIG).Maximum wind energy or maximum ...Based on the characteristic of AC-excited variable speed constant frequency(VSCF)wind power generation,the vector control technique was applied in a doubly fed induction generator(DFIG).Maximum wind energy or maximum output power point can be tracked by decoupling control of active power and reactive power.The research result shows that the net power of generation system delivered to grid in maximum wind energy tracking mode is not the most.We presented a novel maximum power point tracking(MPPT)control strategy by analyzing the DFIG mathematic model and power relations which delivered the maximum power to the grid.The maximum power point could be tracked automatically without measuring wind speed in the control strategy and the control was independent of optimal turbine power curve,which had excellent dynamic and static performances and robustness.Simulation and experimental results testify the accuracy and validity of the control strategy.展开更多
This paper presents a solution to the circulating current fault of aircraft power supply.The DC-link type Variable Frequency to Constant Frequency(VFCF)converter system is the preferred scheme to feed the constant 400...This paper presents a solution to the circulating current fault of aircraft power supply.The DC-link type Variable Frequency to Constant Frequency(VFCF)converter system is the preferred scheme to feed the constant 400 Hz load in an aircraft with a variable frequency power supply.Due to the requirement of aircraft standards,both grounds of the rectification and inversion stage are tied to the metal frame of the aircraft.With such a tied ground,the DC bus voltage rises greatly,and a large circulating current appears in the casing as the ground,which leads to equipment failure and potential safety hazards.According to the existing methods of circulating current fault suppression,this paper analyzes the causes of the above faults and the harmonic components of circulating current and points out the limitations of the existing methods.Therefore,a Common-Mode(CM)choke-based method is proposed to provide a high impedance in the path of the CM circulating current.By doing so,the circulating current can be suppressed without the additional burden of the hardware and control algorithm,which is quite friendly for quality control of mass-production aircraft.Moreover,a simplified mathematic model of the VFCF converter system is derived to calculate the minimum inductance value reference of the CM choke,which saves the weight of passive devices to the greatest extent.Finally,simulation and experimental results are studied to verify the effectiveness of the proposed method.展开更多
Based on the SinoMOS 1 μm 40 V CMOS process, a novel power factor corrention (PFC) converter with a low-power variable frequency function is presented. The circuit introduces a multi-vector error amplifier and a pr...Based on the SinoMOS 1 μm 40 V CMOS process, a novel power factor corrention (PFC) converter with a low-power variable frequency function is presented. The circuit introduces a multi-vector error amplifier and a programmable oscillator to achieve frequency modulation, which provides a rapid dynamic response and precise output voltage clamping with low power in the entire load. According to the external load variation, the system can modulate the circuit operating frequency linearly, thereby ensuring that the PFC converter can work in frequency conversionmode. Measured results show that the normal operating frequency of the PFC converter is 5-6 kHz, the start-up current is 36 μA, the stable operating current is only 2.43 mA, the efficiency is 97.3%, the power factor (PF) is 0.988, THD is 3.8%, the load adjust rate is 3%, and the linear adjust rate is less than 1%. Both theoretical and practical results reveal that the power consumption of the whole supply system is reduced efficiently, especially when the load varies. The active die area of the PFC converter chip is 1.61 ×1.52 mm^2.展开更多
As wind power penetration has been gaining in the power grid for decades,a large number of the doubly fed induction generator(DFIG)based wind farms are being established around the globe.The power capacities of these ...As wind power penetration has been gaining in the power grid for decades,a large number of the doubly fed induction generator(DFIG)based wind farms are being established around the globe.The power capacities of these wind farms may vary around hundreds of MW,and most of the wind farms are connected to long transmission cables whose impedances can not be ignored and require careful attention.Several works have investigated the impedance interaction between the DFIG based wind farm and long transmission cables which may unfortunately cause high frequency resonance(HFR).The main contribution of this paper is to investigate the influence of the variable wind farm capacity on the behavior of the HFR when certain transmission cables are provided.It is found out that the potential HFR may happen in certain wind farms,and the larger wind farm capacity causes more severe HFR due to the relatively weaker grid transmission capability.Simulation results based on Matlab/Simulink are given to validate the analysis of HFR.展开更多
针对风电全直流系统并网给交流电网带来的系统惯量降低、调频能力不足等问题,提出一种改善惯性响应与一次调频的变系数风电全直流系统协调控制策略。在惯量响应方面,网侧换流站采用惯性同步控制,直流升压站采用恒变比控制,实现直流电容...针对风电全直流系统并网给交流电网带来的系统惯量降低、调频能力不足等问题,提出一种改善惯性响应与一次调频的变系数风电全直流系统协调控制策略。在惯量响应方面,网侧换流站采用惯性同步控制,直流升压站采用恒变比控制,实现直流电容对电网的惯量支撑及直流低压侧的直流电压对交流系统频率的感知,在此基础上对直流风电机组(direct current wind turbine,DCWT)附加变虚拟惯性系数的虚拟惯量控制,使风电全直流系统在不同频率响应阶段具备不同的等效惯量。在一次调频方面,DCWT采用超速与变桨相结合的减载运行方式,通过变下垂控制来改变其有功出力,充分利用不同风速下的备用容量,使风电全直流系统更有效地参与一次调频。仿真算例表明,文中所提策略改善了风电全直流系统接入后电力系统的惯性响应及一次调频。展开更多
矿井下常常存在地下水渗积问题,通过控制主泵出水压力,能够有效地排除积水,保持井下环境相对干燥,增强煤矿地下环境的安全性。但由于矿井下的透水后压力负荷通常是不确定的,单纯以压力为传感信号的主泵排水控制的稳定性会受到较大影响,...矿井下常常存在地下水渗积问题,通过控制主泵出水压力,能够有效地排除积水,保持井下环境相对干燥,增强煤矿地下环境的安全性。但由于矿井下的透水后压力负荷通常是不确定的,单纯以压力为传感信号的主泵排水控制的稳定性会受到较大影响,当前排水多以人工观测为主,排水控制智能化实现难度较大。提出一种扬程特性关联下矿井主泵排水智能控制方法。分析矿井下大功率变频式主泵的扬程特性(H-Q),获取变频式主泵排水压力和扬程特性(H-Q)之间的关系。利用这一关系作为传感信号,采用解耦补偿器和神经网络,利用神经网络在线调整比例、积分和微分(proportional integral derivative,PID)控制参数,组建大功率变频式主泵出水压力智能控制器,实现泵出水压力智能控制。通过实验分析证明,研究方法应用后在22 s左右矿井主泵达到最佳状态,过程中产生的相对误差均在0.5%以下。在多次迭代控制下,所提方法的控制延误始终低于0.1 ms。展开更多
基金Funded by the National Natural Science Foundation of China(No.60974049)the Science and Technology Support Industrial Project of Jiangsu Province(No.BZ2008031,No.BE2008074,and No.BE2009090)+1 种基金the Nantong International Cooperative Project(No.W2009003)the Natural Science Foundation of Nantong University(No.08Z022 and No.08Z025).
文摘Based on the characteristic of AC-excited variable speed constant frequency(VSCF)wind power generation,the vector control technique was applied in a doubly fed induction generator(DFIG).Maximum wind energy or maximum output power point can be tracked by decoupling control of active power and reactive power.The research result shows that the net power of generation system delivered to grid in maximum wind energy tracking mode is not the most.We presented a novel maximum power point tracking(MPPT)control strategy by analyzing the DFIG mathematic model and power relations which delivered the maximum power to the grid.The maximum power point could be tracked automatically without measuring wind speed in the control strategy and the control was independent of optimal turbine power curve,which had excellent dynamic and static performances and robustness.Simulation and experimental results testify the accuracy and validity of the control strategy.
基金supported by the Natural Science Foundation for Young Scientists of Shanxi Province,China(No.52007154).
文摘This paper presents a solution to the circulating current fault of aircraft power supply.The DC-link type Variable Frequency to Constant Frequency(VFCF)converter system is the preferred scheme to feed the constant 400 Hz load in an aircraft with a variable frequency power supply.Due to the requirement of aircraft standards,both grounds of the rectification and inversion stage are tied to the metal frame of the aircraft.With such a tied ground,the DC bus voltage rises greatly,and a large circulating current appears in the casing as the ground,which leads to equipment failure and potential safety hazards.According to the existing methods of circulating current fault suppression,this paper analyzes the causes of the above faults and the harmonic components of circulating current and points out the limitations of the existing methods.Therefore,a Common-Mode(CM)choke-based method is proposed to provide a high impedance in the path of the CM circulating current.By doing so,the circulating current can be suppressed without the additional burden of the hardware and control algorithm,which is quite friendly for quality control of mass-production aircraft.Moreover,a simplified mathematic model of the VFCF converter system is derived to calculate the minimum inductance value reference of the CM choke,which saves the weight of passive devices to the greatest extent.Finally,simulation and experimental results are studied to verify the effectiveness of the proposed method.
基金supported by the National Natural Science Foundation of China(Nos.60676009,60776034)the Doctoral Foundation of Ministry of Education of China(No.20050701015)the National Outstanding Young Scientist Foundation of China(No.60725415).
文摘Based on the SinoMOS 1 μm 40 V CMOS process, a novel power factor corrention (PFC) converter with a low-power variable frequency function is presented. The circuit introduces a multi-vector error amplifier and a programmable oscillator to achieve frequency modulation, which provides a rapid dynamic response and precise output voltage clamping with low power in the entire load. According to the external load variation, the system can modulate the circuit operating frequency linearly, thereby ensuring that the PFC converter can work in frequency conversionmode. Measured results show that the normal operating frequency of the PFC converter is 5-6 kHz, the start-up current is 36 μA, the stable operating current is only 2.43 mA, the efficiency is 97.3%, the power factor (PF) is 0.988, THD is 3.8%, the load adjust rate is 3%, and the linear adjust rate is less than 1%. Both theoretical and practical results reveal that the power consumption of the whole supply system is reduced efficiently, especially when the load varies. The active die area of the PFC converter chip is 1.61 ×1.52 mm^2.
文摘As wind power penetration has been gaining in the power grid for decades,a large number of the doubly fed induction generator(DFIG)based wind farms are being established around the globe.The power capacities of these wind farms may vary around hundreds of MW,and most of the wind farms are connected to long transmission cables whose impedances can not be ignored and require careful attention.Several works have investigated the impedance interaction between the DFIG based wind farm and long transmission cables which may unfortunately cause high frequency resonance(HFR).The main contribution of this paper is to investigate the influence of the variable wind farm capacity on the behavior of the HFR when certain transmission cables are provided.It is found out that the potential HFR may happen in certain wind farms,and the larger wind farm capacity causes more severe HFR due to the relatively weaker grid transmission capability.Simulation results based on Matlab/Simulink are given to validate the analysis of HFR.
文摘针对风电全直流系统并网给交流电网带来的系统惯量降低、调频能力不足等问题,提出一种改善惯性响应与一次调频的变系数风电全直流系统协调控制策略。在惯量响应方面,网侧换流站采用惯性同步控制,直流升压站采用恒变比控制,实现直流电容对电网的惯量支撑及直流低压侧的直流电压对交流系统频率的感知,在此基础上对直流风电机组(direct current wind turbine,DCWT)附加变虚拟惯性系数的虚拟惯量控制,使风电全直流系统在不同频率响应阶段具备不同的等效惯量。在一次调频方面,DCWT采用超速与变桨相结合的减载运行方式,通过变下垂控制来改变其有功出力,充分利用不同风速下的备用容量,使风电全直流系统更有效地参与一次调频。仿真算例表明,文中所提策略改善了风电全直流系统接入后电力系统的惯性响应及一次调频。
文摘矿井下常常存在地下水渗积问题,通过控制主泵出水压力,能够有效地排除积水,保持井下环境相对干燥,增强煤矿地下环境的安全性。但由于矿井下的透水后压力负荷通常是不确定的,单纯以压力为传感信号的主泵排水控制的稳定性会受到较大影响,当前排水多以人工观测为主,排水控制智能化实现难度较大。提出一种扬程特性关联下矿井主泵排水智能控制方法。分析矿井下大功率变频式主泵的扬程特性(H-Q),获取变频式主泵排水压力和扬程特性(H-Q)之间的关系。利用这一关系作为传感信号,采用解耦补偿器和神经网络,利用神经网络在线调整比例、积分和微分(proportional integral derivative,PID)控制参数,组建大功率变频式主泵出水压力智能控制器,实现泵出水压力智能控制。通过实验分析证明,研究方法应用后在22 s左右矿井主泵达到最佳状态,过程中产生的相对误差均在0.5%以下。在多次迭代控制下,所提方法的控制延误始终低于0.1 ms。