This paper develops a flexible power regulation and limitation strategy of voltage source inverters(VSIs)under unbalanced grid faults.When the classical power theory is used under unbalanced grid faults,the power osci...This paper develops a flexible power regulation and limitation strategy of voltage source inverters(VSIs)under unbalanced grid faults.When the classical power theory is used under unbalanced grid faults,the power oscillations and current distortions are inevitable.In the proposed strategy,the extended power theory is introduced to compute the power feedbacks together with the classical power theory.Based on the combination of the classical and extended power theory,the proposed strategy can achieve the sinusoidal current provision and the flexible regulation between three common targets,i.e.,constant active power,balanced current,and constant reactive power.Meanwhile,the proposed strategy is associated with a power limiter,which is capable to keep the currents under the pre-defined threshold and to compute the maximum apparent power for better utilization of the inverter capacity.With this power limiter,the rated inverter capacity is fully used for both the active and reactive power provisions under unbalanced grid faults.Using the proposed power regulation and limitation,the VSI can avoid overcurrent tripping and flexibly regulate its power under unbalanced grid faults.All the conclusions are verified by the real-time hardware-in-loop tests.展开更多
As essential pillars of passenger mobility and freight transport,road and rail transportation have experienced a rapid increase over the past years.This trend indicates an increase in energy consumption,especially ele...As essential pillars of passenger mobility and freight transport,road and rail transportation have experienced a rapid increase over the past years.This trend indicates an increase in energy consumption,especially electricity,due to higher energy efficiency and less carbon emission,but it exacerbates the contradiction between the power supply and demand.Nowadays,for additional power sources,increased solar power generation has been widely installed in their own available spaces for road and rail transportation,which has attracted a great deal of attention.This paper reviews the current status of solar power generation and its integrated application in the transport sector.Then,the photovoltaic generation potential of road and rail transportation in China are evaluated.Finally,further developments and perspectives of solar energy-powered road and rail transportation are presented,which not only contributes to lower-carbon and green transportation,but also promotes the development of renewable power generation for energy transformation.It is confirmed that solar energy-powered road and rail transportation is a promising approach for sustainable transportation with more renewable energy and less carbon emission.展开更多
Recently,electric railways have experienced a rapid development causing an increasing power demand.Due to the flexible installation available at trackside land along railways,photovoltaic(PV)generation is suggested as...Recently,electric railways have experienced a rapid development causing an increasing power demand.Due to the flexible installation available at trackside land along railways,photovoltaic(PV)generation is suggested as an extension to the traction power supply system(TPSS)in railways.First,this paper proposes a three-phase integrated configuration for PV generation connected to a two-phase traction network and the on-site consumption of solar resources alongside railways.In this configuration,another inverse V/V transformer is used to maintain a balanced three-phase low voltage(LV)AC bus from a two-phase traction network.It is more convenient for accessing PV generation units.Then,in order to mitigate the negative sequence currents caused by electric trains,an individual phase current(IPC)control strategy for PV converters is developed for power quality improvement.It can not only supply the locomotive with asymmetrical currents,but also provide feedback to the grid through symmetrical currents.All the implementation and calculations are conducted in the three-phase stationary reference frame without any sequence extracting and power compensations.Finally,simulation results are presented to validate the effectiveness of the proposed IPC control strategy.展开更多
As the global energy transforms to renewablebased power system, the wind power generation has experienced a rapid increase. Due to the loss of synchronous machines and its frequency control mechanisms, the gradual evo...As the global energy transforms to renewablebased power system, the wind power generation has experienced a rapid increase. Due to the loss of synchronous machines and its frequency control mechanisms, the gradual evolution leads to critical challenges in maintaining the frequency stability. Under post-fault condition, the wind power generation has a slow recovery due to the fault ride-through(FRT) control strategy and may cause a larger frequency deviation due to the power imbalance between the supply and demand. Then, the impacts of the frequency deviations would further cause inaccuracy and instability in the control system for wind power generation. Considering the long parking time of electric vehicles(EVs), the demand-side response is provided to support the power grid via load-to-grid technology. Thus, a power-balancing coordinated control strategy of the wind power and the demand-side response is developed. It can significantly mitigate the power imbalance, thereby resulting in the enhanced frequency stability. Finally, the simulation results are provided to validate the power-balancing coordinated control strategy.展开更多
The rail transit system plays a crucial role in modern transportation.With the increasing demand for clean and green energy in the transport sector,its energy system is expected to achieve low-carbon and highly effici...The rail transit system plays a crucial role in modern transportation.With the increasing demand for clean and green energy in the transport sector,its energy system is expected to achieve low-carbon and highly efficient energy utilization in rail transit.However,the gradual development of the rail transport energy system has led to an increase in its complexity,and the rising difficulty of system assessment has faced the limitations of traditional assessment methods.Hence,it is essential to develop effective assessment methods.This paper begins by providing a systematic review of the development status of Reliability,Availability,Maintainability and Safety(RAMS)assessment and analyzing the shortcomings of traditional RAMS assessment technology in the context of rail transit energy systems.Subsequently,based on the four fundamental properties of RAMS,it summarizes the current state of key assessment technologies in the field of rail transit.Moreover,the paper delves into the challenges and potential solutions concerning the implementation of RAMS assessment technology for rail transit energy systems.Finally,the paper offers an outlook on the future development of RAMS assessment for rail transport energy systems.By comprehensively analyzing these aspects,the paper aims to contribute valuable insights into optimizing the rail transit energy system,promoting its sustainable and efficient operation in the context of clean and green energy utilization.展开更多
In recent years,the achievement of a renewable and sustainable traction power supply system(TPSS)in the rail sector has become a significant challenge.Focusing on this issue,this paper firstly provides a comprehensive...In recent years,the achievement of a renewable and sustainable traction power supply system(TPSS)in the rail sector has become a significant challenge.Focusing on this issue,this paper firstly provides a comprehensive overview and classification of the state-of-art TPSSs in DC and AC railway.Then,together with low voltage(LV)DC,medium voltage(MV)DC,LV AC,and hybrid AC/DC interconnected microgrid(IMGs),various architectures of resilient TPSSs are proposed for renewable energy integration into DC and AC railway.The resilient TPSS offers on-site access and local consumption of renewable sources alongside railways and guarantees a sustainable power supply in the case of grid disturbances and failures,e.g.,voltage unbalance,harmonic and violent fluctuation,power outage,and extreme events in the wake of natural disasters and extreme weather.This approach also helps facilitate the development of the next generation TPSSs for enhanced flexibility and sustainability.Then,based on a comparative analysis of different resilient TPSSs,a brief outlook of the future trend is given.Finally,it is concluded that resilient TPSS provides a universal solution for both renewable energy integration and high-quality power supply against grid disturbances and failures.展开更多
The installed capacity of renewable energy generation has continued to grow rapidly in recent years along with the global energy transition towards a 100%renewable-based power system.At the same time,the grid-connecte...The installed capacity of renewable energy generation has continued to grow rapidly in recent years along with the global energy transition towards a 100%renewable-based power system.At the same time,the grid-connected large-scale renewable energy brings significant challenges to the safe and stable operation of the power system due to the loss of synchronous machines.Therefore,self-synchronous wind turbines have attracted wide attention from both academia and industry.However,the understanding of the physical operation mechanisms of self-synchronous wind turbines is not clear.In particular,the transient characteristics and dynamic processes of wind turbines are fuzzy in the presence of grid disturbances.Furthermore,it is difficult to design an adaptive fault ride-through(FRT)control strategy.Thus,a dual-mode switching FRT control strategy for self-synchronous wind turbines is developed.Two FRT control strategies are used.In one strategy,the amplitude and phase of the internal potential are directly calculated according to the voltage drop when a minor grid fault occurs.The other dual-mode switching control strategy in the presence of a deep grid fault includes three parts:vector control during the grid fault,fault recovery vector control,and self-synchronous control.The proposed control strategy can significantly mitigate transient overvoltage,overcurrent,and multifrequency oscillation,thereby resulting in enhanced transient stability.Finally,simulation results are provided to validate the proposed control strategy.展开更多
基金This work is supported by the National Key Research and Development Program of China under Project 2021YFB2601600。
文摘This paper develops a flexible power regulation and limitation strategy of voltage source inverters(VSIs)under unbalanced grid faults.When the classical power theory is used under unbalanced grid faults,the power oscillations and current distortions are inevitable.In the proposed strategy,the extended power theory is introduced to compute the power feedbacks together with the classical power theory.Based on the combination of the classical and extended power theory,the proposed strategy can achieve the sinusoidal current provision and the flexible regulation between three common targets,i.e.,constant active power,balanced current,and constant reactive power.Meanwhile,the proposed strategy is associated with a power limiter,which is capable to keep the currents under the pre-defined threshold and to compute the maximum apparent power for better utilization of the inverter capacity.With this power limiter,the rated inverter capacity is fully used for both the active and reactive power provisions under unbalanced grid faults.Using the proposed power regulation and limitation,the VSI can avoid overcurrent tripping and flexibly regulate its power under unbalanced grid faults.All the conclusions are verified by the real-time hardware-in-loop tests.
基金This work was supported in part by the National Natural Science Foundation of China(No.51807182).
文摘As essential pillars of passenger mobility and freight transport,road and rail transportation have experienced a rapid increase over the past years.This trend indicates an increase in energy consumption,especially electricity,due to higher energy efficiency and less carbon emission,but it exacerbates the contradiction between the power supply and demand.Nowadays,for additional power sources,increased solar power generation has been widely installed in their own available spaces for road and rail transportation,which has attracted a great deal of attention.This paper reviews the current status of solar power generation and its integrated application in the transport sector.Then,the photovoltaic generation potential of road and rail transportation in China are evaluated.Finally,further developments and perspectives of solar energy-powered road and rail transportation are presented,which not only contributes to lower-carbon and green transportation,but also promotes the development of renewable power generation for energy transformation.It is confirmed that solar energy-powered road and rail transportation is a promising approach for sustainable transportation with more renewable energy and less carbon emission.
基金supported in part by the National Natural Science Foundation of China(51807182)。
文摘Recently,electric railways have experienced a rapid development causing an increasing power demand.Due to the flexible installation available at trackside land along railways,photovoltaic(PV)generation is suggested as an extension to the traction power supply system(TPSS)in railways.First,this paper proposes a three-phase integrated configuration for PV generation connected to a two-phase traction network and the on-site consumption of solar resources alongside railways.In this configuration,another inverse V/V transformer is used to maintain a balanced three-phase low voltage(LV)AC bus from a two-phase traction network.It is more convenient for accessing PV generation units.Then,in order to mitigate the negative sequence currents caused by electric trains,an individual phase current(IPC)control strategy for PV converters is developed for power quality improvement.It can not only supply the locomotive with asymmetrical currents,but also provide feedback to the grid through symmetrical currents.All the implementation and calculations are conducted in the three-phase stationary reference frame without any sequence extracting and power compensations.Finally,simulation results are presented to validate the effectiveness of the proposed IPC control strategy.
基金supported in part by the National Natural Science Foundation of China (No. 52007174)。
文摘As the global energy transforms to renewablebased power system, the wind power generation has experienced a rapid increase. Due to the loss of synchronous machines and its frequency control mechanisms, the gradual evolution leads to critical challenges in maintaining the frequency stability. Under post-fault condition, the wind power generation has a slow recovery due to the fault ride-through(FRT) control strategy and may cause a larger frequency deviation due to the power imbalance between the supply and demand. Then, the impacts of the frequency deviations would further cause inaccuracy and instability in the control system for wind power generation. Considering the long parking time of electric vehicles(EVs), the demand-side response is provided to support the power grid via load-to-grid technology. Thus, a power-balancing coordinated control strategy of the wind power and the demand-side response is developed. It can significantly mitigate the power imbalance, thereby resulting in the enhanced frequency stability. Finally, the simulation results are provided to validate the power-balancing coordinated control strategy.
基金supported by the National Key R&D Plan Foundation of China(Grant No.2021YFB2601300)Supported by the Fundamental Research Funds for the Central Universities(Grant No.2023JC007).
文摘The rail transit system plays a crucial role in modern transportation.With the increasing demand for clean and green energy in the transport sector,its energy system is expected to achieve low-carbon and highly efficient energy utilization in rail transit.However,the gradual development of the rail transport energy system has led to an increase in its complexity,and the rising difficulty of system assessment has faced the limitations of traditional assessment methods.Hence,it is essential to develop effective assessment methods.This paper begins by providing a systematic review of the development status of Reliability,Availability,Maintainability and Safety(RAMS)assessment and analyzing the shortcomings of traditional RAMS assessment technology in the context of rail transit energy systems.Subsequently,based on the four fundamental properties of RAMS,it summarizes the current state of key assessment technologies in the field of rail transit.Moreover,the paper delves into the challenges and potential solutions concerning the implementation of RAMS assessment technology for rail transit energy systems.Finally,the paper offers an outlook on the future development of RAMS assessment for rail transport energy systems.By comprehensively analyzing these aspects,the paper aims to contribute valuable insights into optimizing the rail transit energy system,promoting its sustainable and efficient operation in the context of clean and green energy utilization.
基金supported in part by the National Natural Science Foundation of China(No.51807182).
文摘In recent years,the achievement of a renewable and sustainable traction power supply system(TPSS)in the rail sector has become a significant challenge.Focusing on this issue,this paper firstly provides a comprehensive overview and classification of the state-of-art TPSSs in DC and AC railway.Then,together with low voltage(LV)DC,medium voltage(MV)DC,LV AC,and hybrid AC/DC interconnected microgrid(IMGs),various architectures of resilient TPSSs are proposed for renewable energy integration into DC and AC railway.The resilient TPSS offers on-site access and local consumption of renewable sources alongside railways and guarantees a sustainable power supply in the case of grid disturbances and failures,e.g.,voltage unbalance,harmonic and violent fluctuation,power outage,and extreme events in the wake of natural disasters and extreme weather.This approach also helps facilitate the development of the next generation TPSSs for enhanced flexibility and sustainability.Then,based on a comparative analysis of different resilient TPSSs,a brief outlook of the future trend is given.Finally,it is concluded that resilient TPSS provides a universal solution for both renewable energy integration and high-quality power supply against grid disturbances and failures.
基金supported in part by the National Natural Science Foundation of China(No.52007174)。
文摘The installed capacity of renewable energy generation has continued to grow rapidly in recent years along with the global energy transition towards a 100%renewable-based power system.At the same time,the grid-connected large-scale renewable energy brings significant challenges to the safe and stable operation of the power system due to the loss of synchronous machines.Therefore,self-synchronous wind turbines have attracted wide attention from both academia and industry.However,the understanding of the physical operation mechanisms of self-synchronous wind turbines is not clear.In particular,the transient characteristics and dynamic processes of wind turbines are fuzzy in the presence of grid disturbances.Furthermore,it is difficult to design an adaptive fault ride-through(FRT)control strategy.Thus,a dual-mode switching FRT control strategy for self-synchronous wind turbines is developed.Two FRT control strategies are used.In one strategy,the amplitude and phase of the internal potential are directly calculated according to the voltage drop when a minor grid fault occurs.The other dual-mode switching control strategy in the presence of a deep grid fault includes three parts:vector control during the grid fault,fault recovery vector control,and self-synchronous control.The proposed control strategy can significantly mitigate transient overvoltage,overcurrent,and multifrequency oscillation,thereby resulting in enhanced transient stability.Finally,simulation results are provided to validate the proposed control strategy.
