Previous studies have demonstrated that disharmony among voltage-source-controlled units(VSCUs)may occur on an alternating current(AC)transmission or distribution line under steady-state operating conditions(SSOCs)or ...Previous studies have demonstrated that disharmony among voltage-source-controlled units(VSCUs)may occur on an alternating current(AC)transmission or distribution line under steady-state operating conditions(SSOCs)or quasistatic operating conditions(QSSOCs).As the studies on frequency disharmony have been expanded to multiple disharmonized vS-CUs in the local power grid,its adverse effects on AC lines and equivalent load(EL)at the bus without active voltage control ability(non-active bus)need to be investigated further.Considering the locality of disharmony and common topological con-nections among VSCUs,this paper adopts a Y-type three-termi-nal local power grid(LPG)as the research object.The disharmony among the three VSCUs is discussed.Firstly,for the load at non-active bus,the formulas for single-phase instantaneous voltage,load current,load power,as well as average power un-der disharmony operating conditions(DOCs)are derived.The characteristic indicators of the above electrical quantities are defined,which can measure the amplification and reduction de-grees of the above electrical quantities before and after disharmony.Secondly,for the line directly connected to VSCUs,the formulas for single-phase instantaneous line current and power and the average power under DOCs are derived.The characteristic indicators of power flow are defined,which can be used to quantify the peak amplification impact of oscillation before and after disharmony.Finally,the case study on the Y-type three-terminal LPG under the single-disharmony and the multi-dis-harmony switching scenarios indicates that the long-period pow-er oscillation caused by disharmony may occur in the load flow at the non-active bus and the line flow.The oscillation causes a serious decrease in load capability and a significant amplification of the peak of line power oscillation.展开更多
基金supported by Science and Technology Project of State Grid Corporation of China“Research on new energy grid-connection control methods and key technologies to improve power grid security and stability”(No.5100-202140498A-0-5-ZN)。
文摘Previous studies have demonstrated that disharmony among voltage-source-controlled units(VSCUs)may occur on an alternating current(AC)transmission or distribution line under steady-state operating conditions(SSOCs)or quasistatic operating conditions(QSSOCs).As the studies on frequency disharmony have been expanded to multiple disharmonized vS-CUs in the local power grid,its adverse effects on AC lines and equivalent load(EL)at the bus without active voltage control ability(non-active bus)need to be investigated further.Considering the locality of disharmony and common topological con-nections among VSCUs,this paper adopts a Y-type three-termi-nal local power grid(LPG)as the research object.The disharmony among the three VSCUs is discussed.Firstly,for the load at non-active bus,the formulas for single-phase instantaneous voltage,load current,load power,as well as average power un-der disharmony operating conditions(DOCs)are derived.The characteristic indicators of the above electrical quantities are defined,which can measure the amplification and reduction de-grees of the above electrical quantities before and after disharmony.Secondly,for the line directly connected to VSCUs,the formulas for single-phase instantaneous line current and power and the average power under DOCs are derived.The characteristic indicators of power flow are defined,which can be used to quantify the peak amplification impact of oscillation before and after disharmony.Finally,the case study on the Y-type three-terminal LPG under the single-disharmony and the multi-dis-harmony switching scenarios indicates that the long-period pow-er oscillation caused by disharmony may occur in the load flow at the non-active bus and the line flow.The oscillation causes a serious decrease in load capability and a significant amplification of the peak of line power oscillation.
