Auxiliary bearings(ABs)are important backup and safety components in active magnetic bearing(AMB)systems.The performance of ABs significantly affects the reliability,safety,and serviceability of theAMB system and the ...Auxiliary bearings(ABs)are important backup and safety components in active magnetic bearing(AMB)systems.The performance of ABs significantly affects the reliability,safety,and serviceability of theAMB system and the rotating equipment.Research on the dynamic behavior during the touchdown process is crucial for analyzing the severity of the touchdown and the behavior is closely related to the performance of theAB.In this paper,a friction torque coefficient is introduced to evaluate the performance ofAB and the touchdown process is simulated and evaluated with various values of this coefficient with a detailed rotor-AB model of a verticalAMB system.The results show that large friction torque coefficient will result in undesired backward whirl of the rotor and catastrophic large load on the AB.Based on these results,this paper suggests that large friction torque coefficient ofABshould be avoided in practice.展开更多
The problem of steady rotation of a composite sphere located at the centre of a spherical container has been investigated. A composite particle referred to in this paper is a spherical solid core covered with a permea...The problem of steady rotation of a composite sphere located at the centre of a spherical container has been investigated. A composite particle referred to in this paper is a spherical solid core covered with a permeable spherical shell. The Brinkman＇s model for the flow inside the compos- ite sphere and the Stokes equation for the flow in the spheri- cal container were used to study the motion. The torque ex- perienced by the porous spherical particle in the presence of cavity is obtained. The wall correction factor is calculated. In the limiting cases, the analytical solution describing the torque for a porous sphere and for a solid sphere in an un- bounded medium are obtained from the present analysis.展开更多
Grid-forming(GFM)control is a key technique for power systems with high penetration of converter-interfaced generation.However,its application to photovoltaic(PV)systems faces challenges related to DC voltage transien...Grid-forming(GFM)control is a key technique for power systems with high penetration of converter-interfaced generation.However,its application to photovoltaic(PV)systems faces challenges related to DC voltage transient stability.This paper investigates a common countermeasure involving a PI-based DC voltage controller for GFM-PV systems,revealing that their small-signal stability is sensitive to parameter tuning.The study develops a generalized DC voltage-dominated 2nd-order GFM model and successfully conducts complex torque analysis,showing that this approach can be effectively extended to other dynamics governed by DC voltage-dominated GFM systems.Subsequently,the paper establishes a stability criterion for GFM-PV systems and proposes a parameter tuning method for DC voltage controllers that incorporates damping margin considerations.The performance of the tuned single-machine-infinite-bus GFM-PV system is validated on the RT-LAB real-time simulation platform under scenarios involving solar irradiance fluctuations and grid frequency disturbances.The proposed method proves effective in ensuring the stability of the GFM-PV system,with robust theoretical support.展开更多
基金National Key R&D Program of China[2018YFB2000100]the National Science and Technology Major Project of China(2019ZX069).
文摘Auxiliary bearings(ABs)are important backup and safety components in active magnetic bearing(AMB)systems.The performance of ABs significantly affects the reliability,safety,and serviceability of theAMB system and the rotating equipment.Research on the dynamic behavior during the touchdown process is crucial for analyzing the severity of the touchdown and the behavior is closely related to the performance of theAB.In this paper,a friction torque coefficient is introduced to evaluate the performance ofAB and the touchdown process is simulated and evaluated with various values of this coefficient with a detailed rotor-AB model of a verticalAMB system.The results show that large friction torque coefficient will result in undesired backward whirl of the rotor and catastrophic large load on the AB.Based on these results,this paper suggests that large friction torque coefficient ofABshould be avoided in practice.
文摘The problem of steady rotation of a composite sphere located at the centre of a spherical container has been investigated. A composite particle referred to in this paper is a spherical solid core covered with a permeable spherical shell. The Brinkman＇s model for the flow inside the compos- ite sphere and the Stokes equation for the flow in the spheri- cal container were used to study the motion. The torque ex- perienced by the porous spherical particle in the presence of cavity is obtained. The wall correction factor is calculated. In the limiting cases, the analytical solution describing the torque for a porous sphere and for a solid sphere in an un- bounded medium are obtained from the present analysis.
基金supported in part by Northeast Branch of State Grid Corporation of China(52992624000W).
文摘Grid-forming(GFM)control is a key technique for power systems with high penetration of converter-interfaced generation.However,its application to photovoltaic(PV)systems faces challenges related to DC voltage transient stability.This paper investigates a common countermeasure involving a PI-based DC voltage controller for GFM-PV systems,revealing that their small-signal stability is sensitive to parameter tuning.The study develops a generalized DC voltage-dominated 2nd-order GFM model and successfully conducts complex torque analysis,showing that this approach can be effectively extended to other dynamics governed by DC voltage-dominated GFM systems.Subsequently,the paper establishes a stability criterion for GFM-PV systems and proposes a parameter tuning method for DC voltage controllers that incorporates damping margin considerations.The performance of the tuned single-machine-infinite-bus GFM-PV system is validated on the RT-LAB real-time simulation platform under scenarios involving solar irradiance fluctuations and grid frequency disturbances.The proposed method proves effective in ensuring the stability of the GFM-PV system,with robust theoretical support.
