An alternating current(AC)microgrid is a system that integrates renewable power,power converters,controllers and loads.Hierarchical control can manage the frequency of the microgrid to prevent imbalance and collapse o...An alternating current(AC)microgrid is a system that integrates renewable power,power converters,controllers and loads.Hierarchical control can manage the frequency of the microgrid to prevent imbalance and collapse of the system.The existing frequency control methods use traditional proportion integration(PI)controllers,which cannot adjust PI parameters in real-time to respond to the status changes of the system.Hierarchical control driven by fuzzy logic allows real-time adjustment of the PI parameters and the method used a two-layer control structure.The primary control used droop control to adjust power distribution,and fuzzy logic was used in the voltage loop of the primary control.The secondary control was added to make up for frequency deviation caused by droop control,and fuzzy logic was used in the secondary frequency control to deal with the dynamic change of frequency caused by the disturbances of loads.The proposed method was simulated in Matlab/Simulink.In the primary control,the proposed method reduced the total harmonic distortion(THD)of two cycles of the output voltage from 4.19%to 3.89%;in the secondary control,the proposed method reduced the frequency fluctuation of the system by about 0.03 Hz and 0.04 Hz when the load was increased and decreased,respectively.The results show that the proposed methods have a better effect on frequency maintenance and voltage control of the AC microgrid.展开更多
大规模风电并网对电网调频提出了严重挑战。VSC-MTDC(Voltage Source Converter Based Multi-Terminal Direct Current)是实现大规模风电并网的主要方式之一。VSC-MTDC可以通过采用频率下垂控制为交流电网提供辅助调频服务。然而传统频...大规模风电并网对电网调频提出了严重挑战。VSC-MTDC(Voltage Source Converter Based Multi-Terminal Direct Current)是实现大规模风电并网的主要方式之一。VSC-MTDC可以通过采用频率下垂控制为交流电网提供辅助调频服务。然而传统频率下垂控制采用固定的控制参数,忽略直流系统运行状态和交流电网的调频能力差异,可能导致换流站过度调制。通过分析传统频率下垂控制的功率支援特性,提出一种VSC-MTDC模糊自适应频率控制,根据交流电网频率变化量、直流电压变化量、换流站功率裕度调节频率控制系数,在保证系统稳定的前提下增强交流电网频率稳定性。最后,仿真验证了所提控制策略的有效性。展开更多
基金National Natural Science Foundation of China(No.62303107)Fundamental Research Funds for the Central Universities,China(Nos.2232022G-09 and 2232021D-38)Shanghai Sailing Program,China(No.21YF1400100)。
文摘An alternating current(AC)microgrid is a system that integrates renewable power,power converters,controllers and loads.Hierarchical control can manage the frequency of the microgrid to prevent imbalance and collapse of the system.The existing frequency control methods use traditional proportion integration(PI)controllers,which cannot adjust PI parameters in real-time to respond to the status changes of the system.Hierarchical control driven by fuzzy logic allows real-time adjustment of the PI parameters and the method used a two-layer control structure.The primary control used droop control to adjust power distribution,and fuzzy logic was used in the voltage loop of the primary control.The secondary control was added to make up for frequency deviation caused by droop control,and fuzzy logic was used in the secondary frequency control to deal with the dynamic change of frequency caused by the disturbances of loads.The proposed method was simulated in Matlab/Simulink.In the primary control,the proposed method reduced the total harmonic distortion(THD)of two cycles of the output voltage from 4.19%to 3.89%;in the secondary control,the proposed method reduced the frequency fluctuation of the system by about 0.03 Hz and 0.04 Hz when the load was increased and decreased,respectively.The results show that the proposed methods have a better effect on frequency maintenance and voltage control of the AC microgrid.
文摘大规模风电并网对电网调频提出了严重挑战。VSC-MTDC(Voltage Source Converter Based Multi-Terminal Direct Current)是实现大规模风电并网的主要方式之一。VSC-MTDC可以通过采用频率下垂控制为交流电网提供辅助调频服务。然而传统频率下垂控制采用固定的控制参数,忽略直流系统运行状态和交流电网的调频能力差异,可能导致换流站过度调制。通过分析传统频率下垂控制的功率支援特性,提出一种VSC-MTDC模糊自适应频率控制,根据交流电网频率变化量、直流电压变化量、换流站功率裕度调节频率控制系数,在保证系统稳定的前提下增强交流电网频率稳定性。最后,仿真验证了所提控制策略的有效性。
