Unintentional islanding phenomenon has been one of the most important problems of gridconnected photovoltaic inverters. To prevent this phenomenon, all kinds of anti-islanding methods have been discussed. This paper p...Unintentional islanding phenomenon has been one of the most important problems of gridconnected photovoltaic inverters. To prevent this phenomenon, all kinds of anti-islanding methods have been discussed. This paper presents a combined active islanding detection method, which consists of active frequency drift method and automatic phase-shift method. The traditional active anti-islanding methods of grid-connected PV inverters bear nondetection zone possibilities for certain paralleled RLC loads. The combined method shows islanding detection ability effectively, and it can eliminate nondetection zones even in the worst case conditions. Simulation in different load conditions is performed for verification.展开更多
For multiple grid-connected inverters with active filter function,it makes sense to regulate every unit to output maximum active power from photovoltaic arrays,as well as eliminate the harmonic due to the non-linear l...For multiple grid-connected inverters with active filter function,it makes sense to regulate every unit to output maximum active power from photovoltaic arrays,as well as eliminate the harmonic due to the non-linear loads connected to the electric networks.Naturally,a centralized control coordination strategy was proposed for the purpose of high facility utilization,good harmonic compensation ability and unwanted overcompensation condition.Based on a vector decoupling control scheme and generalized instantaneous reactive power theory,the solution was to allocate the harmonic eliminating task for every inverter according to the instantaneous power margin of each.The grid current always keeps sinusoidal in spite of non-linear load change and output active power change for any inverter.The simulation results validate the efficacy of the proposed coordination strategy.展开更多
Modeling method for the current control loop of a grid-connected PWM inverter with the LCL output filter was discussed.Firstly,the current control loop with the LCL inverter-side current as feedback was established.Th...Modeling method for the current control loop of a grid-connected PWM inverter with the LCL output filter was discussed.Firstly,the current control loop with the LCL inverter-side current as feedback was established.Then,parameters of PI controller were calculated on the basis of an equivalent controlled object.Finally,Norton equivalent circuit for the current control loop of grid-connected system was derived by integrating one control equation,which connected the PWM inverter output voltage and the LCL inverter-side current,with two circuit equations,separately using the LCL inverter-side current and the injected current as loop currents.With the induced Norton equivalent circuit,system-level resonant and unstable issues on real grid-connected system applied in weak distributed power systems can be easily analyzed.The validity of substituting Norton equivalent circuit for grid-connected system is verified by simulation and experiment.展开更多
在电气化铁路牵引供电系统中,铁路能量路由器(railway energy router,RER)用于回收列车制动能量、接入光伏等新能源,同时改善负序、无功等电能质量,但是既有结构包含两套逆变器和变压器,存在成本高、工程应用难的问题。为此,提出一种基...在电气化铁路牵引供电系统中,铁路能量路由器(railway energy router,RER)用于回收列车制动能量、接入光伏等新能源,同时改善负序、无功等电能质量,但是既有结构包含两套逆变器和变压器,存在成本高、工程应用难的问题。为此,提出一种基于跨相式单相逆变器的新型铁路能量路由器结构,其交流侧跨接α/β相牵引母线、直流侧接入光伏储能。首先,推导新型结构的数学模型和工作原理;然后,针对逆变器传统两端口模式转变为RER的三端口模式存在的有功/无功耦合问题,提出增加无功补偿装置的硬件解耦方法;其次,针对新型RER三端口间多向能流问题,提出一种多层协调优化控制策略。最后,基于典型工况及实测数据,进行了仿真验证,结果表明:三相电压不平衡度从2.52%降低至1.58%,平均功率因数从0.688上升至0.966,再生制动回收率61.65%,光伏消纳率94.16%;主设备容量降低42.31%,成本降低37.23%,说明所提新型RER在实现现有RER相同功能的前提下大幅降低了成本,具有重要的理论和工程价值。展开更多
文摘Unintentional islanding phenomenon has been one of the most important problems of gridconnected photovoltaic inverters. To prevent this phenomenon, all kinds of anti-islanding methods have been discussed. This paper presents a combined active islanding detection method, which consists of active frequency drift method and automatic phase-shift method. The traditional active anti-islanding methods of grid-connected PV inverters bear nondetection zone possibilities for certain paralleled RLC loads. The combined method shows islanding detection ability effectively, and it can eliminate nondetection zones even in the worst case conditions. Simulation in different load conditions is performed for verification.
基金Project(51107111)supported by the National Natural Science Foundation of China
文摘For multiple grid-connected inverters with active filter function,it makes sense to regulate every unit to output maximum active power from photovoltaic arrays,as well as eliminate the harmonic due to the non-linear loads connected to the electric networks.Naturally,a centralized control coordination strategy was proposed for the purpose of high facility utilization,good harmonic compensation ability and unwanted overcompensation condition.Based on a vector decoupling control scheme and generalized instantaneous reactive power theory,the solution was to allocate the harmonic eliminating task for every inverter according to the instantaneous power margin of each.The grid current always keeps sinusoidal in spite of non-linear load change and output active power change for any inverter.The simulation results validate the efficacy of the proposed coordination strategy.
基金Project(51307009)supported by the National Natural Science Foundation of ChinaProject(12JJ4045)supported by Hunan Provincial Natural Science Foundation,China+2 种基金Project(2011KFJJ003)supported by the Key Laboratory for Power Technology of Renewable Energy Sources of Hunan Province,ChinaProject(2011kfj14)supported by the Fund of Key Laboratory of Hunan Province about Power System Operation and Control,ChinaProject(454.13S-20)supported by the Enterprises’Postdoctoral Funds of Pudong Area of Shanghai,China
文摘Modeling method for the current control loop of a grid-connected PWM inverter with the LCL output filter was discussed.Firstly,the current control loop with the LCL inverter-side current as feedback was established.Then,parameters of PI controller were calculated on the basis of an equivalent controlled object.Finally,Norton equivalent circuit for the current control loop of grid-connected system was derived by integrating one control equation,which connected the PWM inverter output voltage and the LCL inverter-side current,with two circuit equations,separately using the LCL inverter-side current and the injected current as loop currents.With the induced Norton equivalent circuit,system-level resonant and unstable issues on real grid-connected system applied in weak distributed power systems can be easily analyzed.The validity of substituting Norton equivalent circuit for grid-connected system is verified by simulation and experiment.
文摘在电气化铁路牵引供电系统中,铁路能量路由器(railway energy router,RER)用于回收列车制动能量、接入光伏等新能源,同时改善负序、无功等电能质量,但是既有结构包含两套逆变器和变压器,存在成本高、工程应用难的问题。为此,提出一种基于跨相式单相逆变器的新型铁路能量路由器结构,其交流侧跨接α/β相牵引母线、直流侧接入光伏储能。首先,推导新型结构的数学模型和工作原理;然后,针对逆变器传统两端口模式转变为RER的三端口模式存在的有功/无功耦合问题,提出增加无功补偿装置的硬件解耦方法;其次,针对新型RER三端口间多向能流问题,提出一种多层协调优化控制策略。最后,基于典型工况及实测数据,进行了仿真验证,结果表明:三相电压不平衡度从2.52%降低至1.58%,平均功率因数从0.688上升至0.966,再生制动回收率61.65%,光伏消纳率94.16%;主设备容量降低42.31%,成本降低37.23%,说明所提新型RER在实现现有RER相同功能的前提下大幅降低了成本,具有重要的理论和工程价值。
