A jet inner-loop bioreactor (JIBR) was used to treat synthetic sanitary sewage with low, medium and high COD load. The experimental results show that it could meet discharge standard at 20\|30 min of HRT (hydraulic re...A jet inner-loop bioreactor (JIBR) was used to treat synthetic sanitary sewage with low, medium and high COD load. The experimental results show that it could meet discharge standard at 20\|30 min of HRT (hydraulic retention time) for low COD concentration and 60\|120 min of HRT for medium and high COD concentration. The maximal COD volume loading and COD sludge loading of 27 kg\5m -3 \5d -1 and 5 kg/d per kg MLSS were acheived respectively, that were 10\|20 times higher than those of traditional wastewater treatment processes. The BOD 5 removal efficiency was more than 90% and NH + 4 —N more than 85%. The study on the activity showed that the oxygen consumption rate of the activated sludge in the JIBR was 39.13 mg\5L -1 \5h -1 , which was 1.7 times higher than that of the SBR(Sequencing Batch Reactor) and the dominant bacteria in jet inner\|loop bioreactor was Pseudomonas species.展开更多
针对微特电机驱动控制系统中,双有源桥(dual active bridge,DAB)变换器在高频调制过程中易产生较大电流应力,导致器件温升高、寿命衰减及负载扰动下系统稳定性下降等问题,本文提出一种改进型双移相优化调制策略。该方法基于双有源桥拓扑...针对微特电机驱动控制系统中,双有源桥(dual active bridge,DAB)变换器在高频调制过程中易产生较大电流应力,导致器件温升高、寿命衰减及负载扰动下系统稳定性下降等问题,本文提出一种改进型双移相优化调制策略。该方法基于双有源桥拓扑,建立双移相调制下的功率传输模型与电流应力数学模型,采用拉格朗日乘数法求解最优移相比组合,并进一步推导多功率场景下的电流应力解析表达式;在控制器设计方面,引入电感电流内环补偿机制,提高系统对电机驱动过程中负载变化的动态响应能力。MATLAB/Simulink仿真结果表明,该方法在典型微特电机负载工况下能有效降低变换器的电流应力,缩短暂态响应时间,并改善输出电压纹波,对提升微特电机控制系统的稳态与暂态性能具有良好效果,为高效能电机驱动供电模块的优化设计提供理论依据。展开更多
【目的】跟网型换流器(grid-following converter,GFL)被广泛应用于新能源并网系统。电网发生故障引起电压跌落时,系统进入低电压穿越(low voltage ride-through,LVRT)过程。传统锁相环(phase-locked loop,PLL)的二阶模型因忽略电流暂...【目的】跟网型换流器(grid-following converter,GFL)被广泛应用于新能源并网系统。电网发生故障引起电压跌落时,系统进入低电压穿越(low voltage ride-through,LVRT)过程。传统锁相环(phase-locked loop,PLL)的二阶模型因忽略电流暂态过程,难以准确描述LVRT期间系统的动态特性,导致暂态同步稳定性的提升效果受限。为此,针对对称故障场景,提出一种适用于LVRT过程的电流内环协同控制策略,以增强系统暂态同步稳定性。【方法】基于PLL四阶动态方程,结合暂态能量函数法,分析PLL输出频率突变以及电流内环与PLL耦合作用对系统暂态同步稳定性的影响,并设计相应的控制策略:根据最优阻抗比动态调整电流参考值,以抑制故障期间暂态能量累积;通过在电流内环前馈解耦项中引入频率偏差补偿机制,加速暂态能量耗散过程。两者协同作用,提升系统在LVRT期间的暂态同步稳定性。【结果】PSCAD/EMTDC对称故障时域仿真结果表明:故障瞬间PLL输出频率突变量与电网电压跌落幅值成正比,增大系统失稳风险;所提控制策略能够有效抑制故障期间PLL输出频率偏差,显著降低虚拟功角首摆幅度,缩短故障清除后系统恢复时间,在不同电网参数下均表现出良好的适应性。【结论】所提电流内环协同控制策略,能够在对称故障期间有效抑制暂态能量累积,在故障清除后加速暂态能量耗散,有效提升了GFL并网系统在此类LVRT过程中的暂态同步稳定性。展开更多
文摘A jet inner-loop bioreactor (JIBR) was used to treat synthetic sanitary sewage with low, medium and high COD load. The experimental results show that it could meet discharge standard at 20\|30 min of HRT (hydraulic retention time) for low COD concentration and 60\|120 min of HRT for medium and high COD concentration. The maximal COD volume loading and COD sludge loading of 27 kg\5m -3 \5d -1 and 5 kg/d per kg MLSS were acheived respectively, that were 10\|20 times higher than those of traditional wastewater treatment processes. The BOD 5 removal efficiency was more than 90% and NH + 4 —N more than 85%. The study on the activity showed that the oxygen consumption rate of the activated sludge in the JIBR was 39.13 mg\5L -1 \5h -1 , which was 1.7 times higher than that of the SBR(Sequencing Batch Reactor) and the dominant bacteria in jet inner\|loop bioreactor was Pseudomonas species.
文摘针对微特电机驱动控制系统中,双有源桥(dual active bridge,DAB)变换器在高频调制过程中易产生较大电流应力,导致器件温升高、寿命衰减及负载扰动下系统稳定性下降等问题,本文提出一种改进型双移相优化调制策略。该方法基于双有源桥拓扑,建立双移相调制下的功率传输模型与电流应力数学模型,采用拉格朗日乘数法求解最优移相比组合,并进一步推导多功率场景下的电流应力解析表达式;在控制器设计方面,引入电感电流内环补偿机制,提高系统对电机驱动过程中负载变化的动态响应能力。MATLAB/Simulink仿真结果表明,该方法在典型微特电机负载工况下能有效降低变换器的电流应力,缩短暂态响应时间,并改善输出电压纹波,对提升微特电机控制系统的稳态与暂态性能具有良好效果,为高效能电机驱动供电模块的优化设计提供理论依据。
文摘【目的】跟网型换流器(grid-following converter,GFL)被广泛应用于新能源并网系统。电网发生故障引起电压跌落时,系统进入低电压穿越(low voltage ride-through,LVRT)过程。传统锁相环(phase-locked loop,PLL)的二阶模型因忽略电流暂态过程,难以准确描述LVRT期间系统的动态特性,导致暂态同步稳定性的提升效果受限。为此,针对对称故障场景,提出一种适用于LVRT过程的电流内环协同控制策略,以增强系统暂态同步稳定性。【方法】基于PLL四阶动态方程,结合暂态能量函数法,分析PLL输出频率突变以及电流内环与PLL耦合作用对系统暂态同步稳定性的影响,并设计相应的控制策略:根据最优阻抗比动态调整电流参考值,以抑制故障期间暂态能量累积;通过在电流内环前馈解耦项中引入频率偏差补偿机制,加速暂态能量耗散过程。两者协同作用,提升系统在LVRT期间的暂态同步稳定性。【结果】PSCAD/EMTDC对称故障时域仿真结果表明:故障瞬间PLL输出频率突变量与电网电压跌落幅值成正比,增大系统失稳风险;所提控制策略能够有效抑制故障期间PLL输出频率偏差,显著降低虚拟功角首摆幅度,缩短故障清除后系统恢复时间,在不同电网参数下均表现出良好的适应性。【结论】所提电流内环协同控制策略,能够在对称故障期间有效抑制暂态能量累积,在故障清除后加速暂态能量耗散,有效提升了GFL并网系统在此类LVRT过程中的暂态同步稳定性。
