Recently,high-frequency oscillation of themodularmultilevel converter(MMC)based high-voltage direct current(HVDC)projects has attracted great attentions.In order to analyze the small-signal stability,this paper uses t...Recently,high-frequency oscillation of themodularmultilevel converter(MMC)based high-voltage direct current(HVDC)projects has attracted great attentions.In order to analyze the small-signal stability,this paper uses the harmonic state-space(HSS)method to establish a detailed frequency domain impedance model of the AC-side of the HVDC transmission system,which considers the internal dynamic characteristics.In addition,the suggested model is also used to assess the system’s high-frequency oscillationmechanism,and the effects of the MMC current inner loop control,feedforward voltage links,and control delay on the high-frequency impedance characteristics and the effect of higher harmonic components.Finally,three oscillation suppression schemes are analyzed for the oscillation problems occurring in actual engineering,and a simplified impedance model considering only the highfrequency impedance characteristics is established to compare the suppression effect with the detailed impedance model to prove its reliability.展开更多
The voltage source converter based high voltage direct current(VSC-HVDC)system is based on voltage source converter,and its control system is more complex.Also affected by the fast control of power electronics,oscilla...The voltage source converter based high voltage direct current(VSC-HVDC)system is based on voltage source converter,and its control system is more complex.Also affected by the fast control of power electronics,oscillation phenomenon in wide frequency domain may occur.To address the problem of small signal stability of the VSCHVDC system,a converter control strategy is designed to improve its small signal stability,and the risk of system oscillation is reduced by attaching a damping controller and optimizing the control parameters.Based on the modeling of the VSC-HVDC system,the general architecture of the inner and outer loop control of the VSCHVDC converter is established;and the damping controllers for DC control and AC control are designed in the phase-locked loop and the inner and outer loop control parts respectively;the state-space statemodel of the control system is established to analyze its performance.And the electromagnetic transient simulation model is built on the PSCAD/EMTDC simulation platform to verify the accuracy of the small signal model.The influence of the parameters of each control part on the stability of the system is summarized.The main control parts affecting stability are optimized for the phenomenon of oscillation due to changes in operation mode occurring on the AC side due to faults and other reasons,which effectively eliminates system oscillation and improves system small signal stability,providing a certain reference for engineering design.展开更多
A DC grid based on half-bridge modular multilevel converters(HB-MMC)is a feasible means to realize the friendly grid connection of renewable energy.To solve problems such as the high cost and technical difficulty of D...A DC grid based on half-bridge modular multilevel converters(HB-MMC)is a feasible means to realize the friendly grid connection of renewable energy.To solve problems such as the high cost and technical difficulty of DC circuit breakers(DCCB),a coordinated control method for fault current suppression of DC grid connecting wind power is proposed.The key influencing factors of DC fault current are revealed by fault characteristics analysis,and an adaptive current-limiting control method for MMC is proposed,whose parameter selection principles are designed to ensure the safe operation of equipment while achieving effective suppression of fault current.In addition,a novel configuration method of dissipative resistors with the current-limiting function is proposed,which can solve the problem of surplus power in the DC grid and reduce the current stress of converter valves.Based on this,a coordination scheme of dissipative resistors,the adaptive current-limiting control method,and DCCBs are proposed to block fault current,effectively reducing the manufacturing difficulty and cost of DCCB.Finally,a four-terminal DC grid simulation model is built based on the RTLAB OP5600 real-time digital simulation platform,and the effectiveness and feasibility of the proposed methods are verified.展开更多
基金supported by Research on the Oscillation Mechanism and Suppression Strategy of Yu-E MMC-HVDC Equipment and System(2021Yudian Technology 33#).
文摘Recently,high-frequency oscillation of themodularmultilevel converter(MMC)based high-voltage direct current(HVDC)projects has attracted great attentions.In order to analyze the small-signal stability,this paper uses the harmonic state-space(HSS)method to establish a detailed frequency domain impedance model of the AC-side of the HVDC transmission system,which considers the internal dynamic characteristics.In addition,the suggested model is also used to assess the system’s high-frequency oscillationmechanism,and the effects of the MMC current inner loop control,feedforward voltage links,and control delay on the high-frequency impedance characteristics and the effect of higher harmonic components.Finally,three oscillation suppression schemes are analyzed for the oscillation problems occurring in actual engineering,and a simplified impedance model considering only the highfrequency impedance characteristics is established to compare the suppression effect with the detailed impedance model to prove its reliability.
基金supported by Research on the Oscillation Mechanism and Suppression Strategy of Yu-E MMC-HVDC Equipment and System(2021Yudian Technology 33#).
文摘The voltage source converter based high voltage direct current(VSC-HVDC)system is based on voltage source converter,and its control system is more complex.Also affected by the fast control of power electronics,oscillation phenomenon in wide frequency domain may occur.To address the problem of small signal stability of the VSCHVDC system,a converter control strategy is designed to improve its small signal stability,and the risk of system oscillation is reduced by attaching a damping controller and optimizing the control parameters.Based on the modeling of the VSC-HVDC system,the general architecture of the inner and outer loop control of the VSCHVDC converter is established;and the damping controllers for DC control and AC control are designed in the phase-locked loop and the inner and outer loop control parts respectively;the state-space statemodel of the control system is established to analyze its performance.And the electromagnetic transient simulation model is built on the PSCAD/EMTDC simulation platform to verify the accuracy of the small signal model.The influence of the parameters of each control part on the stability of the system is summarized.The main control parts affecting stability are optimized for the phenomenon of oscillation due to changes in operation mode occurring on the AC side due to faults and other reasons,which effectively eliminates system oscillation and improves system small signal stability,providing a certain reference for engineering design.
基金supported in part by the National Natural Science Foundation of China under Grant 52207078in part by the Joint Funds of the National Natural Science Foundation of China under Grant U2066208.
文摘A DC grid based on half-bridge modular multilevel converters(HB-MMC)is a feasible means to realize the friendly grid connection of renewable energy.To solve problems such as the high cost and technical difficulty of DC circuit breakers(DCCB),a coordinated control method for fault current suppression of DC grid connecting wind power is proposed.The key influencing factors of DC fault current are revealed by fault characteristics analysis,and an adaptive current-limiting control method for MMC is proposed,whose parameter selection principles are designed to ensure the safe operation of equipment while achieving effective suppression of fault current.In addition,a novel configuration method of dissipative resistors with the current-limiting function is proposed,which can solve the problem of surplus power in the DC grid and reduce the current stress of converter valves.Based on this,a coordination scheme of dissipative resistors,the adaptive current-limiting control method,and DCCBs are proposed to block fault current,effectively reducing the manufacturing difficulty and cost of DCCB.Finally,a four-terminal DC grid simulation model is built based on the RTLAB OP5600 real-time digital simulation platform,and the effectiveness and feasibility of the proposed methods are verified.
