Stability of grid-connected VSCs in DC voltage control(DVC)timescales(i.e.,the frequency range of dynamics covering converter outer controls)has recently caught increased attention,while the existing approaches,such a...Stability of grid-connected VSCs in DC voltage control(DVC)timescales(i.e.,the frequency range of dynamics covering converter outer controls)has recently caught increased attention,while the existing approaches,such as eigenvalue analysis and dq-domain impedance analysis,have respective limitations on addressing these types of stability issues.This paper proposes an alternative net damping criterion dedicated for analyzing the DVC timescale stability in a multi-VSC system.This criterion is strictly mapped from the Nyquist stability criterion utilizing the gain margin concept,which preserves the advantages of the classical positive net damping criterion suggested by Canay[20]–allowing for decomposition analysis of a subsystem’s contribution to the closed-loop stability in a single-input single-output(SISO)framework,but overcomes its deficiency of possibly erroneous prediction of system dynamic behaviors.Case studies show that the proposed criterion can correctly predict some unstable conditions(e.g.,monotonic divergence)which cannot be identified by the classical net damping criterion.Additionally,the condition for when the classical criterion is available is also pointed out,the proposed criterion can also act as a complement of the classical criterion for stability examination.展开更多
This paper presents an improved virtual synchronous control(VSynC) for the grid-connected voltage source converter(VSC) so as to continuously operate under the grid voltage with steady unbalance.The improved VSynC int...This paper presents an improved virtual synchronous control(VSynC) for the grid-connected voltage source converter(VSC) so as to continuously operate under the grid voltage with steady unbalance.The improved VSynC introduces the negative sequence power controls on basis of conventional VSynC.The improved VSynC is capable of regulating the negative sequence internal voltage to reduce the negative-sequence injected currents and oscillated powers of the VSC aroused by the negative-sequence grid voltage.Three alternative local control objectives for the VSC itself under steady state unbalanced grid conditions and their corresponding power references are deduced and computed.Simulated and experimental results are presented to validate the correctness and effectiveness of the proposed improved VSynC to enhance the continuous operation performance of VSynC-based VSCs during grid voltage steady-state unbalance.展开更多
Power sharing among multiterminal high voltage direct current terminals(MT-HVDC)is mainly developed based on a priority or sequential manners,which uses to prevent the problem of overloading due to a predefined contro...Power sharing among multiterminal high voltage direct current terminals(MT-HVDC)is mainly developed based on a priority or sequential manners,which uses to prevent the problem of overloading due to a predefined controller coefficient.Furthermore,fixed power sharing control also suffers from an inability to identify power availability at a rectification station.There is a need for a controller that ensures an efficient power sharing among the MT-HVDC terminals,prevents the possibility of overloading,and utilizes the available power sharing.A new adaptive wireless control for active power sharing among multiterminal(MT-HVDC)systems,including power availability and power management policy,is proposed in this paper.The proposed control strategy solves these issues and,this proposed controller strategy is a generic method that can be applied for unlimited number of converter stations.The rational of this proposed controller is to increase the system reliability by avoiding the necessity of fast communication links.The test system in this paper consists of four converter stations based on three phase-two AC voltage levels.The proposed control strategy for a multiterminal HVDC system is conducted in the power systems computer aided design/electromagnetic transient design and control(PSCAD/EMTDC)simulation environment.The simulation results significantly show the flexibility and usefulness of the proposed power sharing control provided by the new adaptive wireless method.展开更多
基金This work was supported in part by the Research Grants Council of Hong Kong under Grant GRF 17207818the National Natural Science Foundation of China under Grant 51677160the Themebased Research Scheme(TRS)under T23-701/14-N.
文摘Stability of grid-connected VSCs in DC voltage control(DVC)timescales(i.e.,the frequency range of dynamics covering converter outer controls)has recently caught increased attention,while the existing approaches,such as eigenvalue analysis and dq-domain impedance analysis,have respective limitations on addressing these types of stability issues.This paper proposes an alternative net damping criterion dedicated for analyzing the DVC timescale stability in a multi-VSC system.This criterion is strictly mapped from the Nyquist stability criterion utilizing the gain margin concept,which preserves the advantages of the classical positive net damping criterion suggested by Canay[20]–allowing for decomposition analysis of a subsystem’s contribution to the closed-loop stability in a single-input single-output(SISO)framework,but overcomes its deficiency of possibly erroneous prediction of system dynamic behaviors.Case studies show that the proposed criterion can correctly predict some unstable conditions(e.g.,monotonic divergence)which cannot be identified by the classical net damping criterion.Additionally,the condition for when the classical criterion is available is also pointed out,the proposed criterion can also act as a complement of the classical criterion for stability examination.
基金supported by National Natural Science Foundation of China (No.51607130)National Key Research and Development Program (No.2016YFB0900104)National Natural Science Fund for Excellent Young Scholars (No.51322704)
文摘This paper presents an improved virtual synchronous control(VSynC) for the grid-connected voltage source converter(VSC) so as to continuously operate under the grid voltage with steady unbalance.The improved VSynC introduces the negative sequence power controls on basis of conventional VSynC.The improved VSynC is capable of regulating the negative sequence internal voltage to reduce the negative-sequence injected currents and oscillated powers of the VSC aroused by the negative-sequence grid voltage.Three alternative local control objectives for the VSC itself under steady state unbalanced grid conditions and their corresponding power references are deduced and computed.Simulated and experimental results are presented to validate the correctness and effectiveness of the proposed improved VSynC to enhance the continuous operation performance of VSynC-based VSCs during grid voltage steady-state unbalance.
文摘Power sharing among multiterminal high voltage direct current terminals(MT-HVDC)is mainly developed based on a priority or sequential manners,which uses to prevent the problem of overloading due to a predefined controller coefficient.Furthermore,fixed power sharing control also suffers from an inability to identify power availability at a rectification station.There is a need for a controller that ensures an efficient power sharing among the MT-HVDC terminals,prevents the possibility of overloading,and utilizes the available power sharing.A new adaptive wireless control for active power sharing among multiterminal(MT-HVDC)systems,including power availability and power management policy,is proposed in this paper.The proposed control strategy solves these issues and,this proposed controller strategy is a generic method that can be applied for unlimited number of converter stations.The rational of this proposed controller is to increase the system reliability by avoiding the necessity of fast communication links.The test system in this paper consists of four converter stations based on three phase-two AC voltage levels.The proposed control strategy for a multiterminal HVDC system is conducted in the power systems computer aided design/electromagnetic transient design and control(PSCAD/EMTDC)simulation environment.The simulation results significantly show the flexibility and usefulness of the proposed power sharing control provided by the new adaptive wireless method.
