摘要
柔性直流配电系统中定功率控制的换流器具有恒功率负载特性,会降低系统阻尼,对系统的稳定性产生不利影响。针对该问题,在直流配电系统中加入超导磁储能SMES(superconducting magnetic energy storage)装置来提高系统的稳定性。推导了柔性直流配电系统的反馈控制模型,采用频域分析法研究了换流器恒功率负载特性对系统稳定性的影响,并结合数学模型和频域分析,指出SMES装置能够为电网提供正阻尼,增大了系统开环传递函数在剪切频率处的相位裕度,从而改善了系统稳定性。为防止超导磁体两端电压过高,SMES装置与直流配电网连接的DC/DC换流器需具备一定的电压调节性能,因此研究了采用模块化多电平DC/DC换流器DC-MMC(modular multilevel DC/DC converter)的SMES装置,通过调节子模块个数灵活设置换流器电压变比,在实现换流器能量双向流动的同时控制超导磁体两端电压,以保护储能装置。最后通过时域仿真波形验证了采用DC-MMC的SMES装置在提高柔性直流配电系统稳定性方面的可行性和有效性。
The converter with constant-power control in a flexible DC distribution system has characteristics of constant-power load,which will reduce the system damping and adversely affect the system stability.To address this problem,a superconducting magnetic energy storage(SMES)device is introduced to improve the system stability.A feedback control model of the flexible DC distribution system is derived,and the effect of constant-power load characteristics of the converter on system stability is investigated by frequency-domain analysis.Combined with a mathematical model and frequency-domain analysis,it is also pointed out that the SMES device can improve the system stability by introducing positive damping to grid and increasing the phase margin of the system’s open-loop transfer function at the shear frequency.To prevent over-high voltage at both ends of the superconducting magnet,the DC/DC converter which connects the SMES device with the DC distribution network needs to have certain voltage regulation performance.Therefore,the SMES device with a modular multilevel DC/DC converter(DC-MMC)is studied,which can adjust the number of sub-modules flexibly to set the voltage ratio of the converter.Moreover,the DC-MMC can control the voltage at both ends of the superconducting magnet while realizing a bidirectional flow of energy in the converter,thus protecting storage device.The feasibility and effectiveness of the SMES device with DC-MMC in improving the stability of flexible DC distribution system is verified by time-domain simulation waveforms.
作者
李岚
丁安敏
田洪英
张彦
张奎同
马文忠
LI Lan;DING Anmin;TIAN Hongying;ZHANG Yan;ZHANG Kuitong;MA Wenzhong(College of New Energy,China University of Petroleum(East China),Qingdao 266580,China;Shandong Energy Group Co.,Ltd,Ji’nan 273500,China)
出处
《电源学报》
CSCD
北大核心
2024年第2期250-262,共13页
Journal of Power Supply
基金
国家自然科学基金资助项目(51777216)
山东省自然科学基金资助项目(ZR2018MEE040,ZR2019MEE094)。
关键词
柔性直流配电系统
超导磁储能
小信号稳定性
反馈控制模型
模块化多电平DC/DC换流器
Flexible DC distribution system
superconducting magnetic energy storage(SMES)
small signal stability
feedback control model
modular multilevel DC/DC converter(DC-MMC)
