The AC/DC hybrid distribution network is one of the trends in distribution network development, which poses great challenges to the traditional distribution transformer. In this paper, a new topology suitable for AC/D...The AC/DC hybrid distribution network is one of the trends in distribution network development, which poses great challenges to the traditional distribution transformer. In this paper, a new topology suitable for AC/DC hybrid distribution network is put forward according to the demands of power grid, with advantages of accepting DG and DC loads, while clearing DC fault by blocking the clamping double sub-module(CDSM) of input stage. Then, this paper shows the typical structure of AC/DC distribution network that is hand in hand. Based on the new topology, this paper designs the control and modulation strategies of each stage, where the outer loop controller of input stage is emphasized for its twocontrol mode. At last, the rationality of new topology and the validity of control strategies are verified by the steady and dynamic state simulation. At the same time, the simulation results highlight the role of PET in energy regulation.展开更多
This paper presents a three-phase integrated power electronic transformer(PET)topology with the capability of DC fault clearance based on the investigation of PET topology.The proposed PET has three ports of high-volt...This paper presents a three-phase integrated power electronic transformer(PET)topology with the capability of DC fault clearance based on the investigation of PET topology.The proposed PET has three ports of high-voltage AC,high-voltage DC and low-voltage DC,which can achieve the flexible access of distributed energy resources・The power unit of the PET adopts a three-phase integrated topology,and the single-phase fluctuating power in the DC-link capacitor is reduced by a 4-port DC/DC converter,thereby reducing the capacitance of the DC-link capacitor;Meanwhile,the power unit uses the clamp double sub-module(CDSM)to allow for self-clearing of the short-circuit fault on the high-voltage DC side.Finally,this paper verifies the proposed PET through an EMT simulation and experimental prototype.展开更多
The concept of a flexible power electronics substation(FPES)was first applied in the Zhangbei DC distribution network demonstration project.As a multi-port power electronics transformer(PET)with different AC and DC vo...The concept of a flexible power electronics substation(FPES)was first applied in the Zhangbei DC distribution network demonstration project.As a multi-port power electronics transformer(PET)with different AC and DC voltage levels,the FPES has adopted a novel topology integrating modular multilevel converter(MMC)and four-winding medium frequency transformer(FWMFT)based multiport DC-DC converter,which can significantly reduce capacitance in each sub-module(SM)of a MMC and also save space and cost.In this paper,in order to accelerate speed of electromagnetic transient(EMT)simulations of FPES based hybrid AC/DC distribution systems,an averaged-value model(AVM)is proposed for efficient and accurate representation of FPES.Assume that all SM capacitor voltages are perfectly balanced in the MMC,then the MMC behavior can be modeled using controlled voltage sources based on modulation voltages from control systems.In terms of the averaged current transfer characteristics among the windings of the FWMFT,we consider that all multiport DC-DC converters are controlled with the same dynamics,a lumped averaged model using controlled current and voltage sources has been developed for these four-port DC-DC converters connected to the upper or lower arms of the MMC.The presented FPES AVM model has been tested and validated by comparison with a detailed IGBT-based EMT model.Results show that the AVM is significantly more efficient while maintaining its accuracy in an EMT simulation.展开更多
基金supported by National Key Research and Development Program of China (2016YFB0900500,2017YFB0903100)the State Grid Science and Technology Project (SGRI-DL-F1-51-011)
文摘The AC/DC hybrid distribution network is one of the trends in distribution network development, which poses great challenges to the traditional distribution transformer. In this paper, a new topology suitable for AC/DC hybrid distribution network is put forward according to the demands of power grid, with advantages of accepting DG and DC loads, while clearing DC fault by blocking the clamping double sub-module(CDSM) of input stage. Then, this paper shows the typical structure of AC/DC distribution network that is hand in hand. Based on the new topology, this paper designs the control and modulation strategies of each stage, where the outer loop controller of input stage is emphasized for its twocontrol mode. At last, the rationality of new topology and the validity of control strategies are verified by the steady and dynamic state simulation. At the same time, the simulation results highlight the role of PET in energy regulation.
基金supported by National Key Research and Development Program of China(2016YFB0400505)Science and Technology Project of State Grid Corporation(SGRIGLBDTKJ[2017]676).
文摘This paper presents a three-phase integrated power electronic transformer(PET)topology with the capability of DC fault clearance based on the investigation of PET topology.The proposed PET has three ports of high-voltage AC,high-voltage DC and low-voltage DC,which can achieve the flexible access of distributed energy resources・The power unit of the PET adopts a three-phase integrated topology,and the single-phase fluctuating power in the DC-link capacitor is reduced by a 4-port DC/DC converter,thereby reducing the capacitance of the DC-link capacitor;Meanwhile,the power unit uses the clamp double sub-module(CDSM)to allow for self-clearing of the short-circuit fault on the high-voltage DC side.Finally,this paper verifies the proposed PET through an EMT simulation and experimental prototype.
基金This work was supported in part by the National Nature Science Foundation of China(51977142)。
文摘The concept of a flexible power electronics substation(FPES)was first applied in the Zhangbei DC distribution network demonstration project.As a multi-port power electronics transformer(PET)with different AC and DC voltage levels,the FPES has adopted a novel topology integrating modular multilevel converter(MMC)and four-winding medium frequency transformer(FWMFT)based multiport DC-DC converter,which can significantly reduce capacitance in each sub-module(SM)of a MMC and also save space and cost.In this paper,in order to accelerate speed of electromagnetic transient(EMT)simulations of FPES based hybrid AC/DC distribution systems,an averaged-value model(AVM)is proposed for efficient and accurate representation of FPES.Assume that all SM capacitor voltages are perfectly balanced in the MMC,then the MMC behavior can be modeled using controlled voltage sources based on modulation voltages from control systems.In terms of the averaged current transfer characteristics among the windings of the FWMFT,we consider that all multiport DC-DC converters are controlled with the same dynamics,a lumped averaged model using controlled current and voltage sources has been developed for these four-port DC-DC converters connected to the upper or lower arms of the MMC.The presented FPES AVM model has been tested and validated by comparison with a detailed IGBT-based EMT model.Results show that the AVM is significantly more efficient while maintaining its accuracy in an EMT simulation.
