Line commutated converter based high voltage direct current(LCC-HVDC)links are widely employed for long distance bulk power transmission and asynchronous alternating current(AC)grid connections.However,LCC-HVDC system...Line commutated converter based high voltage direct current(LCC-HVDC)links are widely employed for long distance bulk power transmission and asynchronous alternating current(AC)grid connections.However,LCC-HVDC systems often suffer from commutation failures when AC voltage is distorted,oscillating or reduced by AC faults,which leads to overheating of converter valves and interruptions in transmitted power.All of which can have an adverse impact on the safety and stability of the entire power system.This paper proposes a supplementary control for mitigation of successive commutation failures on the basis of analyzing the influence of phase-locked loop(PLL)dynamics on the commutation process.By analyzing the impact of PLL dynamics on the actual leading angle,it is found that changes in the AC voltage phase remarkably influence commutation.Accordingly,the error between the AC voltage phase and PLL’s output angle is added to the output of the extinction angle or DC voltage control to mitigate the successive commutation failures of LCC-HVDC stations.Simulations conducted on the CIGRE benchmark model in PSCAD/EMTDC validate the performance of the supplementary control,which effectively mitigates successive commutation failures.展开更多
The dynamic characteristics of converter-dominated systems are governed by controlling power converters and the interactions between converter systems and conventional alternators.Frequency oscillations can appear und...The dynamic characteristics of converter-dominated systems are governed by controlling power converters and the interactions between converter systems and conventional alternators.Frequency oscillations can appear under dynamic operation conditions caused by the phase-locked loop dynamics and interactions among the converter control systems.The oscillations may be poorly damped,which can result in reduced power generation,longer settling time,or disconnections of sensitive components.It is foreseeable that damping services will be critical for power grid stabilization in the future with high penetration of renewable generation.In this work,synchronous condensers(SCs)are evaluated and applied to provide damping services to the power grid under post-event conditions.An innovative supplementary controller for the automatic voltage regulator of SCs is proposed to improve the frequency stabilization in a converter-dominated system after disturbances.Using local and remote measurements,SCs are able to modulate the reactive power output and hence,the terminal bus voltage,which further impacts the power flow in the system;therefore,damping can be provided to the frequency oscillations.The control is implemented on an industrial-level hardware platform,and the performance is verified by the hardware-in-the-loop simulation.展开更多
基金supported in part by the Joint Fund Program of National Natural Science Fund of China under Grant No.U1766202.
文摘Line commutated converter based high voltage direct current(LCC-HVDC)links are widely employed for long distance bulk power transmission and asynchronous alternating current(AC)grid connections.However,LCC-HVDC systems often suffer from commutation failures when AC voltage is distorted,oscillating or reduced by AC faults,which leads to overheating of converter valves and interruptions in transmitted power.All of which can have an adverse impact on the safety and stability of the entire power system.This paper proposes a supplementary control for mitigation of successive commutation failures on the basis of analyzing the influence of phase-locked loop(PLL)dynamics on the commutation process.By analyzing the impact of PLL dynamics on the actual leading angle,it is found that changes in the AC voltage phase remarkably influence commutation.Accordingly,the error between the AC voltage phase and PLL’s output angle is added to the output of the extinction angle or DC voltage control to mitigate the successive commutation failures of LCC-HVDC stations.Simulations conducted on the CIGRE benchmark model in PSCAD/EMTDC validate the performance of the supplementary control,which effectively mitigates successive commutation failures.
基金This work was supported by Synchronous Condenser Application(SCAPP)project funded by ForskEL program(No.12196)administrated by Energinet.dk.
文摘The dynamic characteristics of converter-dominated systems are governed by controlling power converters and the interactions between converter systems and conventional alternators.Frequency oscillations can appear under dynamic operation conditions caused by the phase-locked loop dynamics and interactions among the converter control systems.The oscillations may be poorly damped,which can result in reduced power generation,longer settling time,or disconnections of sensitive components.It is foreseeable that damping services will be critical for power grid stabilization in the future with high penetration of renewable generation.In this work,synchronous condensers(SCs)are evaluated and applied to provide damping services to the power grid under post-event conditions.An innovative supplementary controller for the automatic voltage regulator of SCs is proposed to improve the frequency stabilization in a converter-dominated system after disturbances.Using local and remote measurements,SCs are able to modulate the reactive power output and hence,the terminal bus voltage,which further impacts the power flow in the system;therefore,damping can be provided to the frequency oscillations.The control is implemented on an industrial-level hardware platform,and the performance is verified by the hardware-in-the-loop simulation.
