通过将带LC滤波的桥式不控整流器近似为定直流脉波周期、定导电角的可控整流器与占空比极小的Boost斩波器级联的系统,提出直流侧电流断续模式(discontinuous current mode,DCM)下不控整流器的一种大信号建模方法,并运用开关函数和谐波...通过将带LC滤波的桥式不控整流器近似为定直流脉波周期、定导电角的可控整流器与占空比极小的Boost斩波器级联的系统,提出直流侧电流断续模式(discontinuous current mode,DCM)下不控整流器的一种大信号建模方法,并运用开关函数和谐波平衡原理,分别建立单相、三相桥式不控整流器DCM下的大信号数学模型,该模型具有非线性常微分代数方程组形式。通过与仿真模型进行对比,证明所常微分代数方程组形式。通过与仿真模型进行对比,证明所提出的建模方法是可行的,所建立的大信号数学模型能有效反映不控整流器源侧及负载侧的大扰动特性,且模型维数越高,计算结果越精确。展开更多
Due to low investment cost and high reliability,a new scheme called DR-HVDC(Diode Rectifier based HVDC)transmission was recently proposed for grid integration of large offshore wind farms.However,in this scheme,the ap...Due to low investment cost and high reliability,a new scheme called DR-HVDC(Diode Rectifier based HVDC)transmission was recently proposed for grid integration of large offshore wind farms.However,in this scheme,the application of conventional control strategies for stability operation face several challenges due to the uncontrollability of the DR.In this paper,a coordinated control strategy of offshore wind farms using the DR-HVDC transmission technology to connect with the onshore grid,is investigated.A novel coordinated control strategy for DR-HVDC is proposed based on the analysis of the DC current control ability of the full-bridge-based modular multilevel converter(FB-MMC)at the onshore station and the input and output characteristics of the diode rectifier at the offshore.Considering the characteristics of operation stability and decoupling between reactive power and active power,a simplified design based on double-loop droop control for offshore AC voltage is proposed after power flow and voltage–current(I–V)characteristics of the offshore wind farm being analyzed.Furthermore,the impact of onshore AC fault to offshore wind farm is analyzed,and a fast fault detection and protection strategy without relying on communication is proposed.Case studies carried out by PSCAD/EMTDC verify the effectiveness of the proposed control strategy for the start up,power fluctuation,and onshore and offshore fault conditions.展开更多
为解决直流侧电流断续模式(discontinuous current mode,DCM)下不控整流器因扰动过程中直流脉波周期、导电角均可变而不易数学建模的问题,通过研究带LC滤波的m相桥式不控整流器DCM下的稳态模型,得出导电角和电源电压初始相角的非线性约...为解决直流侧电流断续模式(discontinuous current mode,DCM)下不控整流器因扰动过程中直流脉波周期、导电角均可变而不易数学建模的问题,通过研究带LC滤波的m相桥式不控整流器DCM下的稳态模型,得出导电角和电源电压初始相角的非线性约束方程,提出一种将不控整流器近似为定直流脉波周期、定导电角的可控整流器的小信号建模方法,并运用开关函数法和谐波平衡原理,分别建立带LC滤波的单相、三相桥式不控整流器DCM下状态方程形式的小信号数学模型。通过与经实验验证的仿真模型进行对比,证明所提出的建模方法是有效的,所建立的小信号数学模型维数越高,计算结果越精确。展开更多
基于二极管整流器的高压直流DR-HVDC(diode-rectifer-based high voltage direct current)输电系统是一种很有前景的海上风电低成本接入方案,它可将风能从偏远的海上风电场输送到陆上电力系统。然而随着海上DR-HVDC系统的不断增多,可能...基于二极管整流器的高压直流DR-HVDC(diode-rectifer-based high voltage direct current)输电系统是一种很有前景的海上风电低成本接入方案,它可将风能从偏远的海上风电场输送到陆上电力系统。然而随着海上DR-HVDC系统的不断增多,可能会导致风机WT(wind turbine)的变流器控制难度增大,系统稳定性变差。基于此,提出了一种适用于DR-HVDC连接海上WT变流器的新型电网形成控制方法。该方法采用2个正序控制回路来调节WTs的输出有功功率,并维持海上交流电网的频率和电压,其中第一个控制器可将每台WT的有功功率误差调节为电压角偏差,从而造成系统频率偏差;第二个控制器通过调整WT的交流电压幅值以抵消频率偏差。变流器内部电流控制回路用于限制故障电流,并消除系统中的高频谐振。最后,通过故障穿越、WT功率变化、无功扰动和WTs停机4个方面的电磁暂态仿真,验证了所提控制方法的有效性和优越性。展开更多
A rectifier circuit for wireless energy harvesting(WEH) with a wide input power range is proposed in this paper. We build up accurate models of the diodes to improve the accuracy of the design of the rectifier. Due to...A rectifier circuit for wireless energy harvesting(WEH) with a wide input power range is proposed in this paper. We build up accurate models of the diodes to improve the accuracy of the design of the rectifier. Due to the nonlinear characteristics of the diodes, a new band-stop structure is introduced to reduce the imaginary part impedance and suppress harmonics. A novel structure with double branches and an optimized λ/4 microstrip line is proposed to realize the power division ratio adjustment by the input power automatically. The proposed two branches can satisfy the two cases with input power of-20 dBm to 0 dBm and 0 dBm to 15 dBm, respectively. Here, dBm = 10 log(P mW), and P represents power. An impedance compression network(ICN) is correspondingly designed to maintain the input impedance stability over the wide input power range. A rectifier that works at 2.45 GHz is implemented. The measured results show that the highest efficiency can reach 51.5% at the output power of 0 dBm and higher than 40% at the input power of-5 dBm to 12 dBm.展开更多
为改善变流器单边可控下开绕组永磁同步发电机(permanent magnet synchronous generator,PMSG)的运行性能,提出了三电平中点钳位式(neutral point clamped,NPC)变流器和二极管整流桥集成供电的单边可控开绕组PMSG系统拓扑结构。通过建...为改善变流器单边可控下开绕组永磁同步发电机(permanent magnet synchronous generator,PMSG)的运行性能,提出了三电平中点钳位式(neutral point clamped,NPC)变流器和二极管整流桥集成供电的单边可控开绕组PMSG系统拓扑结构。通过建立开绕组PMSG数学模型,研究了基于三电平变流器的单边可控开绕组PMSG系统控制策略,并结合三电平变流器的中点电压(neutral point potential,NPP)波动机制,分析了在此结构下三电平变流器关于调制度范围和功率因数角范围的运行性能。最后,通过实验验证了所提控制策略的正确性和可行性。展开更多
文摘通过将带LC滤波的桥式不控整流器近似为定直流脉波周期、定导电角的可控整流器与占空比极小的Boost斩波器级联的系统,提出直流侧电流断续模式(discontinuous current mode,DCM)下不控整流器的一种大信号建模方法,并运用开关函数和谐波平衡原理,分别建立单相、三相桥式不控整流器DCM下的大信号数学模型,该模型具有非线性常微分代数方程组形式。通过与仿真模型进行对比,证明所常微分代数方程组形式。通过与仿真模型进行对比,证明所提出的建模方法是可行的,所建立的大信号数学模型能有效反映不控整流器源侧及负载侧的大扰动特性,且模型维数越高,计算结果越精确。
基金supported by State Grid Science and Technology Project“Study on Key Technologies of Large Scale Offshore Wind Power Integrating with Onshore Grid”(4000-202055045A-0-0-00)
文摘Due to low investment cost and high reliability,a new scheme called DR-HVDC(Diode Rectifier based HVDC)transmission was recently proposed for grid integration of large offshore wind farms.However,in this scheme,the application of conventional control strategies for stability operation face several challenges due to the uncontrollability of the DR.In this paper,a coordinated control strategy of offshore wind farms using the DR-HVDC transmission technology to connect with the onshore grid,is investigated.A novel coordinated control strategy for DR-HVDC is proposed based on the analysis of the DC current control ability of the full-bridge-based modular multilevel converter(FB-MMC)at the onshore station and the input and output characteristics of the diode rectifier at the offshore.Considering the characteristics of operation stability and decoupling between reactive power and active power,a simplified design based on double-loop droop control for offshore AC voltage is proposed after power flow and voltage–current(I–V)characteristics of the offshore wind farm being analyzed.Furthermore,the impact of onshore AC fault to offshore wind farm is analyzed,and a fast fault detection and protection strategy without relying on communication is proposed.Case studies carried out by PSCAD/EMTDC verify the effectiveness of the proposed control strategy for the start up,power fluctuation,and onshore and offshore fault conditions.
文摘为解决直流侧电流断续模式(discontinuous current mode,DCM)下不控整流器因扰动过程中直流脉波周期、导电角均可变而不易数学建模的问题,通过研究带LC滤波的m相桥式不控整流器DCM下的稳态模型,得出导电角和电源电压初始相角的非线性约束方程,提出一种将不控整流器近似为定直流脉波周期、定导电角的可控整流器的小信号建模方法,并运用开关函数法和谐波平衡原理,分别建立带LC滤波的单相、三相桥式不控整流器DCM下状态方程形式的小信号数学模型。通过与经实验验证的仿真模型进行对比,证明所提出的建模方法是有效的,所建立的小信号数学模型维数越高,计算结果越精确。
文摘基于二极管整流器的高压直流DR-HVDC(diode-rectifer-based high voltage direct current)输电系统是一种很有前景的海上风电低成本接入方案,它可将风能从偏远的海上风电场输送到陆上电力系统。然而随着海上DR-HVDC系统的不断增多,可能会导致风机WT(wind turbine)的变流器控制难度增大,系统稳定性变差。基于此,提出了一种适用于DR-HVDC连接海上WT变流器的新型电网形成控制方法。该方法采用2个正序控制回路来调节WTs的输出有功功率,并维持海上交流电网的频率和电压,其中第一个控制器可将每台WT的有功功率误差调节为电压角偏差,从而造成系统频率偏差;第二个控制器通过调整WT的交流电压幅值以抵消频率偏差。变流器内部电流控制回路用于限制故障电流,并消除系统中的高频谐振。最后,通过故障穿越、WT功率变化、无功扰动和WTs停机4个方面的电磁暂态仿真,验证了所提控制方法的有效性和优越性。
基金Key Laboratory of Chinese Academy of Sciences Foundation,China(No. 20190918)。
文摘A rectifier circuit for wireless energy harvesting(WEH) with a wide input power range is proposed in this paper. We build up accurate models of the diodes to improve the accuracy of the design of the rectifier. Due to the nonlinear characteristics of the diodes, a new band-stop structure is introduced to reduce the imaginary part impedance and suppress harmonics. A novel structure with double branches and an optimized λ/4 microstrip line is proposed to realize the power division ratio adjustment by the input power automatically. The proposed two branches can satisfy the two cases with input power of-20 dBm to 0 dBm and 0 dBm to 15 dBm, respectively. Here, dBm = 10 log(P mW), and P represents power. An impedance compression network(ICN) is correspondingly designed to maintain the input impedance stability over the wide input power range. A rectifier that works at 2.45 GHz is implemented. The measured results show that the highest efficiency can reach 51.5% at the output power of 0 dBm and higher than 40% at the input power of-5 dBm to 12 dBm.
文摘为改善变流器单边可控下开绕组永磁同步发电机(permanent magnet synchronous generator,PMSG)的运行性能,提出了三电平中点钳位式(neutral point clamped,NPC)变流器和二极管整流桥集成供电的单边可控开绕组PMSG系统拓扑结构。通过建立开绕组PMSG数学模型,研究了基于三电平变流器的单边可控开绕组PMSG系统控制策略,并结合三电平变流器的中点电压(neutral point potential,NPP)波动机制,分析了在此结构下三电平变流器关于调制度范围和功率因数角范围的运行性能。最后,通过实验验证了所提控制策略的正确性和可行性。
