A novel operation control method for relay protection in flexible DC distribution networks with distributed power supply is proposed to address the issue of inaccurate fault location during relay protection,leading to...A novel operation control method for relay protection in flexible DC distribution networks with distributed power supply is proposed to address the issue of inaccurate fault location during relay protection,leading to poor performance.The method combines a fault-tolerant fault location method based on long-term and short-term memory networks to accurately locate the fault section.Then,an operation control method for relay protection based on adaptive weight and whale optimization algorithm(WOA)is used to construct an objective function considering the shortest relay protection action time and the smallest impulse current.The adaptive weight and WOA are employed to obtain the optimal strategy for relay protection operation control,reducing the action time and impulse current.Experimental results demonstrate the effectiveness of the proposed method in accurately locating faults and improving relay protection performance.The longest operation time is reduced by 4.7023 s,and the maximum impulse current is limited to 0.3 A,effectively controlling the impact of large impulse currents and enhancing control efficiency.展开更多
为满足海上风电直流升压汇集需求,提出一种具备非对称双向功率传输能力的DC-DC变换器方案。在海上风电功率正向外送时,能够实现并联输入串联输出升压功能。在风电场需要功率反向支撑时,通过改变变换器调制策略,能够实现较小功率容量下...为满足海上风电直流升压汇集需求,提出一种具备非对称双向功率传输能力的DC-DC变换器方案。在海上风电功率正向外送时,能够实现并联输入串联输出升压功能。在风电场需要功率反向支撑时,通过改变变换器调制策略,能够实现较小功率容量下反向功率传输。首先分析正/反向模态下,变换器零电压开关(zero voltage switching,ZVS)软开关与功率传输特性。在此基础上,同时考虑输出电压调节与串联电压均衡多运行目标,构建相应调制与控制策略。与传统双向变换器相比,所提拓扑在满足非对称双向功率变换需求的同时,通过降低元件数量,能够降低变换器成本。基于仿真与实验结果,对所提出非对称双向变换器功率调节、模式切换与软开关特性进行测试,验证所提非对称双向变换器概念与方案的有效性。展开更多
Recently H_(2)^(+)ion beam finds widespread use in many fields,and the demand of high-current H_(2)^(+)ion sources is urgent for numerous applications.However,there are currently almost no reported ion sources capable...Recently H_(2)^(+)ion beam finds widespread use in many fields,and the demand of high-current H_(2)^(+)ion sources is urgent for numerous applications.However,there are currently almost no reported ion sources capable of generating a directcurrent(DC)H_(2)^(+)beam with tens of mA current.In previous work at Peking University(PKU),H_(2)^(+)ion beams with a current of over 40 mA have been obtained in pulse mode,and a current of 16 mA was achieved in DC mode.In this paper,we report the generation of a DC H_(2)^(+)ion beam with a current of 22 mA extracted from an improved miniaturized microwave driven ion source(MMDIS).Beam analysis shows that the H_(2)^(+)fraction in the extracted beam is about 70%.The emittance of the mixed hydrogen beam is about 0.12π·mm·mrad.These results provide references for the applications of H_(2)^(+)beam and the design of H_(2)^(+)ion source.展开更多
DCS系统(Distributed Control System)作为热工控制系统的核心部分,其性能指标对发电机组安全稳定运行有着至关重要的影响。DCS系统在长期运行中常存在如卡件故障、信号干扰等问题,需依据行业技术标准,通过科学的测试手段,对其主要安全...DCS系统(Distributed Control System)作为热工控制系统的核心部分,其性能指标对发电机组安全稳定运行有着至关重要的影响。DCS系统在长期运行中常存在如卡件故障、信号干扰等问题,需依据行业技术标准,通过科学的测试手段,对其主要安全性指标如网络性能、控制器性能、响应时间、控制器冗余监测、控制器切换、抗干扰能力等进行测试,可有效判断出DCS长周期运行过程中存在的安全隐患,并进行针对性运行维护,以提升其安全可靠性。展开更多
结合新能源混合发电要求,介绍一种三端口电气隔离、软开关运行和低输入电流纹波的三端口多向DC-DC变流器。首先通过对三绕组高频变压器的T/Δ等效变换,对5种工作模态下的功率和变压器电流有效值进行近似统一,得出全运行范围下的通用表达...结合新能源混合发电要求,介绍一种三端口电气隔离、软开关运行和低输入电流纹波的三端口多向DC-DC变流器。首先通过对三绕组高频变压器的T/Δ等效变换,对5种工作模态下的功率和变压器电流有效值进行近似统一,得出全运行范围下的通用表达式,简化了分析和降低了设计复杂度;然后对开关管的软开关运行条件进行分析,证明该拓扑具有良好的软开关特性;最后设计了一台2.5 k W的实验样机,对此变流器在宽电压输入范围条件下的工作模态和软开关特性进行实验验证,证明了理论分析的正确性。展开更多
由于换流站数目、控制模式以及指令值的不同,电压源换流器型多端直流(voltage source converter based multi terminal dc,VSC-MTDC)输电系统在实际运行中具有多种运行方式,并且随着电网运行条件的变化,VSC-MTDC输电系统的运行方式也随...由于换流站数目、控制模式以及指令值的不同,电压源换流器型多端直流(voltage source converter based multi terminal dc,VSC-MTDC)输电系统在实际运行中具有多种运行方式,并且随着电网运行条件的变化,VSC-MTDC输电系统的运行方式也随之改变。因此,直流运行中心需要根据换流站运行特性、电网条件和系统参数等快速确定VSCMTDC输电系统运行控制模式与系统状态量,这对系统调控和安全运行具有重要意义。基于此,分析主导换流站、辅助换流站、定有功功率控制换流站和风电场换流站的直流电压–电流运行特性,推导各换流站在不同控制模式下的特性方程,给出各换流站不同控制模式下的电气量范围。接着,提出VSC-MTDC输电系统稳态工作点的计算方法,完善换流站的控制模式修正方法。最后,以典型的五端直流输电系统为例,Matlab编程验证了直流运行特性分析方法和稳态工作点计算方法的准确性;计算结果表明,该稳态分析方法能够快速准确地计算出VSC-MTDC输电系统的稳态工作点。展开更多
基于电压源换流器高压直流输电(voltage source converter based HVDC,VSC-HVDC)的直流系统存在与交流线路并联运行的情况。交直流系统之间相互切换的运行工况复杂,且切换过程存在切换依据难以确定、切换冲击大以及通信延时等问题。为...基于电压源换流器高压直流输电(voltage source converter based HVDC,VSC-HVDC)的直流系统存在与交流线路并联运行的情况。交直流系统之间相互切换的运行工况复杂,且切换过程存在切换依据难以确定、切换冲击大以及通信延时等问题。为解决该问题,在分析VSC-HVDC工作原理、数学模型及其控制策略的基础上,提出了一种大型风电场经VSC-HVDC交直流并联系统并网的运行控制策略,该策略在不改变换流站控制方式的情况下,可实现交直流并联系统运行方式的无缝切换。基于MATLAB/Simulink仿真软件,建立了系统仿真模型,对交直流并联系统稳态运行及动态切换过程进行了仿真分析。仿真结果表明,所提出的控制策略能够较好地实现交直流并联系统有功功率的精确分配和运行方式的无缝切换,算法简单,可靠性高。展开更多
文摘A novel operation control method for relay protection in flexible DC distribution networks with distributed power supply is proposed to address the issue of inaccurate fault location during relay protection,leading to poor performance.The method combines a fault-tolerant fault location method based on long-term and short-term memory networks to accurately locate the fault section.Then,an operation control method for relay protection based on adaptive weight and whale optimization algorithm(WOA)is used to construct an objective function considering the shortest relay protection action time and the smallest impulse current.The adaptive weight and WOA are employed to obtain the optimal strategy for relay protection operation control,reducing the action time and impulse current.Experimental results demonstrate the effectiveness of the proposed method in accurately locating faults and improving relay protection performance.The longest operation time is reduced by 4.7023 s,and the maximum impulse current is limited to 0.3 A,effectively controlling the impact of large impulse currents and enhancing control efficiency.
文摘为满足海上风电直流升压汇集需求,提出一种具备非对称双向功率传输能力的DC-DC变换器方案。在海上风电功率正向外送时,能够实现并联输入串联输出升压功能。在风电场需要功率反向支撑时,通过改变变换器调制策略,能够实现较小功率容量下反向功率传输。首先分析正/反向模态下,变换器零电压开关(zero voltage switching,ZVS)软开关与功率传输特性。在此基础上,同时考虑输出电压调节与串联电压均衡多运行目标,构建相应调制与控制策略。与传统双向变换器相比,所提拓扑在满足非对称双向功率变换需求的同时,通过降低元件数量,能够降低变换器成本。基于仿真与实验结果,对所提出非对称双向变换器功率调节、模式切换与软开关特性进行测试,验证所提非对称双向变换器概念与方案的有效性。
基金supported by the National Natural Science Foundation of China(Grant No.11975036)support from the State Key Laboratory of Nuclear Physics and Technology at PKU.
文摘Recently H_(2)^(+)ion beam finds widespread use in many fields,and the demand of high-current H_(2)^(+)ion sources is urgent for numerous applications.However,there are currently almost no reported ion sources capable of generating a directcurrent(DC)H_(2)^(+)beam with tens of mA current.In previous work at Peking University(PKU),H_(2)^(+)ion beams with a current of over 40 mA have been obtained in pulse mode,and a current of 16 mA was achieved in DC mode.In this paper,we report the generation of a DC H_(2)^(+)ion beam with a current of 22 mA extracted from an improved miniaturized microwave driven ion source(MMDIS).Beam analysis shows that the H_(2)^(+)fraction in the extracted beam is about 70%.The emittance of the mixed hydrogen beam is about 0.12π·mm·mrad.These results provide references for the applications of H_(2)^(+)beam and the design of H_(2)^(+)ion source.
文摘DCS系统(Distributed Control System)作为热工控制系统的核心部分,其性能指标对发电机组安全稳定运行有着至关重要的影响。DCS系统在长期运行中常存在如卡件故障、信号干扰等问题,需依据行业技术标准,通过科学的测试手段,对其主要安全性指标如网络性能、控制器性能、响应时间、控制器冗余监测、控制器切换、抗干扰能力等进行测试,可有效判断出DCS长周期运行过程中存在的安全隐患,并进行针对性运行维护,以提升其安全可靠性。
文摘结合新能源混合发电要求,介绍一种三端口电气隔离、软开关运行和低输入电流纹波的三端口多向DC-DC变流器。首先通过对三绕组高频变压器的T/Δ等效变换,对5种工作模态下的功率和变压器电流有效值进行近似统一,得出全运行范围下的通用表达式,简化了分析和降低了设计复杂度;然后对开关管的软开关运行条件进行分析,证明该拓扑具有良好的软开关特性;最后设计了一台2.5 k W的实验样机,对此变流器在宽电压输入范围条件下的工作模态和软开关特性进行实验验证,证明了理论分析的正确性。
文摘由于换流站数目、控制模式以及指令值的不同,电压源换流器型多端直流(voltage source converter based multi terminal dc,VSC-MTDC)输电系统在实际运行中具有多种运行方式,并且随着电网运行条件的变化,VSC-MTDC输电系统的运行方式也随之改变。因此,直流运行中心需要根据换流站运行特性、电网条件和系统参数等快速确定VSCMTDC输电系统运行控制模式与系统状态量,这对系统调控和安全运行具有重要意义。基于此,分析主导换流站、辅助换流站、定有功功率控制换流站和风电场换流站的直流电压–电流运行特性,推导各换流站在不同控制模式下的特性方程,给出各换流站不同控制模式下的电气量范围。接着,提出VSC-MTDC输电系统稳态工作点的计算方法,完善换流站的控制模式修正方法。最后,以典型的五端直流输电系统为例,Matlab编程验证了直流运行特性分析方法和稳态工作点计算方法的准确性;计算结果表明,该稳态分析方法能够快速准确地计算出VSC-MTDC输电系统的稳态工作点。
文摘基于电压源换流器高压直流输电(voltage source converter based HVDC,VSC-HVDC)的直流系统存在与交流线路并联运行的情况。交直流系统之间相互切换的运行工况复杂,且切换过程存在切换依据难以确定、切换冲击大以及通信延时等问题。为解决该问题,在分析VSC-HVDC工作原理、数学模型及其控制策略的基础上,提出了一种大型风电场经VSC-HVDC交直流并联系统并网的运行控制策略,该策略在不改变换流站控制方式的情况下,可实现交直流并联系统运行方式的无缝切换。基于MATLAB/Simulink仿真软件,建立了系统仿真模型,对交直流并联系统稳态运行及动态切换过程进行了仿真分析。仿真结果表明,所提出的控制策略能够较好地实现交直流并联系统有功功率的精确分配和运行方式的无缝切换,算法简单,可靠性高。
