模块化多电平变换器(modular multilevel converter,MMC)拓扑已广泛应用于中高压大功率输配电和电机驱动领域。其中,具有直流故障穿越能力的全桥子模块(full-bridge submodule,FB-SM)型MMC拓扑目前正受到越来越多的关注和应用,但为了抑...模块化多电平变换器(modular multilevel converter,MMC)拓扑已广泛应用于中高压大功率输配电和电机驱动领域。其中,具有直流故障穿越能力的全桥子模块(full-bridge submodule,FB-SM)型MMC拓扑目前正受到越来越多的关注和应用,但为了抑制子模块电容电压纹波,需使用较大电容值的子模块电容,其显著增加系统的硬件成本和体积。该文提出一种基于器件复用的有源功率解耦型FB-SM(FB-SM with active power decoupling,APD-SM),通过子模块中的器件复用,使其兼具电容电压纹波抑制和直流故障穿越能力,同时不改变MMC拓扑的外输出特性。相较于传统FB-SM拓扑,该拓扑可在全功率因数范围内显著抑制子模块电容电压纹波;详细介绍该拓扑的推演规律、运行原理、调制方法和控制策略,并对拓扑结构中的关键参数进行分析和设计,从多方面与传统FB-SM拓扑进行对比分析;最后,基于PLECS仿真平台搭建APD-SM和FB-SM型MMC仿真模型(分别缩写为APD-MMC和FB-MMC),并基于样机模型进行实验验证。仿真和实验结果验证该拓扑和控制策略的有效性。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
Power reversal control strategies for different types of hybrid line-commutated-converter(LCC)/modular multi-level converter(MMC)based high-voltage direct-current(HVDC)systems have been proposed with the consideration...Power reversal control strategies for different types of hybrid line-commutated-converter(LCC)/modular multi-level converter(MMC)based high-voltage direct-current(HVDC)systems have been proposed with the consideration of system configurations and MMC’s topologies.The studies show that the full-bridge(FB)MMC gives better performance than half-bridge(HB)MMCs in terms of power reversal in hybrid LCC/MMC systems.The modulation method employed in this paper can achieve a smooth online polarity reversal for hybrid LCC/FB-MMC HVDC systems.Additional DC switches and/or discharging resistors may be needed to reverse the DC polarity of LCC/HB-MMC HVDC systems.Based on the proposed strate-gies,the power reversal processes of the studied systems can be accomplished within several seconds.The speed can be changed according to system operation requirements.The effectiveness of the proposed control strategies has been verified through simulations conducted in PSCAD/EMTDC.展开更多
文摘模块化多电平变换器(modular multilevel converter,MMC)拓扑已广泛应用于中高压大功率输配电和电机驱动领域。其中,具有直流故障穿越能力的全桥子模块(full-bridge submodule,FB-SM)型MMC拓扑目前正受到越来越多的关注和应用,但为了抑制子模块电容电压纹波,需使用较大电容值的子模块电容,其显著增加系统的硬件成本和体积。该文提出一种基于器件复用的有源功率解耦型FB-SM(FB-SM with active power decoupling,APD-SM),通过子模块中的器件复用,使其兼具电容电压纹波抑制和直流故障穿越能力,同时不改变MMC拓扑的外输出特性。相较于传统FB-SM拓扑,该拓扑可在全功率因数范围内显著抑制子模块电容电压纹波;详细介绍该拓扑的推演规律、运行原理、调制方法和控制策略,并对拓扑结构中的关键参数进行分析和设计,从多方面与传统FB-SM拓扑进行对比分析;最后,基于PLECS仿真平台搭建APD-SM和FB-SM型MMC仿真模型(分别缩写为APD-MMC和FB-MMC),并基于样机模型进行实验验证。仿真和实验结果验证该拓扑和控制策略的有效性。
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.
基金This work was supported by Science and Technology Project of the State Grid Corporation of China,“HVDC Systems/Grids for Transnational Interconnections”,project number:SGTYHT/16-JS-198.
文摘Power reversal control strategies for different types of hybrid line-commutated-converter(LCC)/modular multi-level converter(MMC)based high-voltage direct-current(HVDC)systems have been proposed with the consideration of system configurations and MMC’s topologies.The studies show that the full-bridge(FB)MMC gives better performance than half-bridge(HB)MMCs in terms of power reversal in hybrid LCC/MMC systems.The modulation method employed in this paper can achieve a smooth online polarity reversal for hybrid LCC/FB-MMC HVDC systems.Additional DC switches and/or discharging resistors may be needed to reverse the DC polarity of LCC/HB-MMC HVDC systems.Based on the proposed strate-gies,the power reversal processes of the studied systems can be accomplished within several seconds.The speed can be changed according to system operation requirements.The effectiveness of the proposed control strategies has been verified through simulations conducted in PSCAD/EMTDC.
