With photovoltaic(PV)sources becoming more prevalent in the energy generation mix,transitioning grid-connected PV systems from grid-following(GFL)mode to gridforming(GFM)mode becomes essential for offering self-synchr...With photovoltaic(PV)sources becoming more prevalent in the energy generation mix,transitioning grid-connected PV systems from grid-following(GFL)mode to gridforming(GFM)mode becomes essential for offering self-synchronization and active support services.Although numerous GFM methods have been proposed,the potential of DC voltage control malfunction during the provision of the primary and inertia support in a GFM PV system remains insufficiently researched.To fill the gap,some main GFM methods have been integrated into PV systems featuring detailed DC source dynamics.We conduct a comparative analysis of their performance in active support and DC voltage regulation.AC GFM methods such as virtual synchronous machine(VSM)face a significant risk of DC voltage failure in situations like alterations in solar radiation,leading to PV system tripping and jeopardizing local system operation.In the case of DC GFM methods such as matching control(MC),the active support falls short due to the absence of an accurate and dispatchable droop response.To address the issue,a matching synchronous machine(MSM)control method is developed to provide dispatchable active support and enhance the DC voltage dynamics by integrating the MC and VSM control loops.The active support capability of the PV systems with the proposed method is quantified analytically and verified by numerical simulations and field tests.展开更多
The fast-response feature from a superconducting magnetic energy storage(SMES)device is favored for suppressing instantaneous voltage and power fluctuations,but the SMES coil is much more expensive than a conventional...The fast-response feature from a superconducting magnetic energy storage(SMES)device is favored for suppressing instantaneous voltage and power fluctuations,but the SMES coil is much more expensive than a conventional battery energy storage device.In order to improve the energy utilization rate and reduce the energy storage cost under multiple-line power distribution conditions,this paper investigates a new interline DC dynamic voltage restorer(IDC-DVR)scheme with one SMES coil shared among multiple compensating circuits.In this new concept,an improved current-voltage(I/V)chopper assembly,which has a series of input/output power ports,is introduced to connect the single SMES coil with multiple power lines,and thereby satisfy the independent energy exchange requirements of any line to be compensated.Specifically,if two or more power lines have simultaneous compensating demands,the SMES coil can be selectively controlled to compensate the preferable line according to the priority order of the line.The feasibility of the proposed scheme is technically verified to maintain the transient voltage stability in multiple-line voltage swell and sag cases caused by either output voltage fluctuations from external power sources or power demand fluctuations from local sensitive loads.The simulation results provide a technical basis to develop a cost-effective SMES-based IDC-DVR for use in various DC distribution networks.展开更多
基金supported in part by the National Key R&D Program of China(No.2022YFB2402900)the National Natural Science Foundation of China(No.U2066601)。
文摘With photovoltaic(PV)sources becoming more prevalent in the energy generation mix,transitioning grid-connected PV systems from grid-following(GFL)mode to gridforming(GFM)mode becomes essential for offering self-synchronization and active support services.Although numerous GFM methods have been proposed,the potential of DC voltage control malfunction during the provision of the primary and inertia support in a GFM PV system remains insufficiently researched.To fill the gap,some main GFM methods have been integrated into PV systems featuring detailed DC source dynamics.We conduct a comparative analysis of their performance in active support and DC voltage regulation.AC GFM methods such as virtual synchronous machine(VSM)face a significant risk of DC voltage failure in situations like alterations in solar radiation,leading to PV system tripping and jeopardizing local system operation.In the case of DC GFM methods such as matching control(MC),the active support falls short due to the absence of an accurate and dispatchable droop response.To address the issue,a matching synchronous machine(MSM)control method is developed to provide dispatchable active support and enhance the DC voltage dynamics by integrating the MC and VSM control loops.The active support capability of the PV systems with the proposed method is quantified analytically and verified by numerical simulations and field tests.
基金This work was supported in part by the National Natural Science Foundation of China under Grant No.51807128State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources under Grant No.LAPS20017.
文摘The fast-response feature from a superconducting magnetic energy storage(SMES)device is favored for suppressing instantaneous voltage and power fluctuations,but the SMES coil is much more expensive than a conventional battery energy storage device.In order to improve the energy utilization rate and reduce the energy storage cost under multiple-line power distribution conditions,this paper investigates a new interline DC dynamic voltage restorer(IDC-DVR)scheme with one SMES coil shared among multiple compensating circuits.In this new concept,an improved current-voltage(I/V)chopper assembly,which has a series of input/output power ports,is introduced to connect the single SMES coil with multiple power lines,and thereby satisfy the independent energy exchange requirements of any line to be compensated.Specifically,if two or more power lines have simultaneous compensating demands,the SMES coil can be selectively controlled to compensate the preferable line according to the priority order of the line.The feasibility of the proposed scheme is technically verified to maintain the transient voltage stability in multiple-line voltage swell and sag cases caused by either output voltage fluctuations from external power sources or power demand fluctuations from local sensitive loads.The simulation results provide a technical basis to develop a cost-effective SMES-based IDC-DVR for use in various DC distribution networks.
