Aiming at the problems of large fluctuation of output active power and poor control performance in the process of frequency support of an energy-storage-type static-var-generator(ESVG),the adaptive adjustment control ...Aiming at the problems of large fluctuation of output active power and poor control performance in the process of frequency support of an energy-storage-type static-var-generator(ESVG),the adaptive adjustment control method for its active-loop parameters is used to realize thewind-farmfrequency support,which has become the current research hotspot.Taking the ESVG with a supercapacitor on the DC side as the research object,the influence trend of the change of virtual rotation inertia and virtual damping coefficient on its virtual angular velocity and power angle is analyzed.Then,the constraint relationship between the equivalent virtual inertia time constant of the supercapacitor and the virtual rotation inertia of the ESVG is clarified.Then,combined with the second-order response characteristics of the ESVG power control loop,the selection principles of the frequency modulation coefficient,the virtual rotation inertia,and the virtual damping coefficient are determined.An ESVG adjustment control method,considering the adaptive adjustment of the active loop parameters of the supercapacitor equivalent inertia,is proposed.While ensuring the frequency support capability of the ESVG,the fluctuation degree of its output active power and the virtual angular velocity are suppressed,and the proposed adjustment method also improves the stability of the ESVG control system and the frequency support capability for the wind farm.Finally,the simulation verifies the correctness of the theoretical analysis and the effectiveness of the proposed strategy.展开更多
We report a comprehensive numerical study of super resolution (SR) structured illumination microscopy (SIM) utilizing the classic Heintzmann-Cremer SIM process and algorithm. In particular, we investigated the impact ...We report a comprehensive numerical study of super resolution (SR) structured illumination microscopy (SIM) utilizing the classic Heintzmann-Cremer SIM process and algorithm. In particular, we investigated the impact of the diffraction limit of the underlying imaging system on the optimal SIM grating frequency that can be used to obtain the highest SR enhancement with non-continuous spatial frequency support. Besides confirming the previous theoretical and experimental work that SR-SIM can achieve an enhancement close to 3 times the diffraction limit with grating pattern illuminations, we also observe and report a series of more subtle effects of SR-SIM with non-continuous spatial frequency support. Our simulations show that when the SIM grating frequency exceeds twice that of the diffraction limit, the higher SIM grating frequency can help achieve a higher SR enhancement for the underlying imaging systems whose diffraction limit is low, though this enhancement is obtained at the cost of losing resolution at some lower resolution targets. Our simulations also show that, for underlying imaging systems with high diffraction limits, however, SR-SIM grating frequencies above twice the diffraction limits tend to bring no significant extra enhancement. Furthermore, we observed that there exists a limit grating frequency above which the SR enhancement effect is lost, and the reconstructed images essentially have the same resolution as the one obtained directly from the underlying imaging system without using the SIM process.展开更多
Frequency droop control is widely used in permanent magnet synchronous generators(PMSGs)based wind turbines(WTs)for grid frequency support.However,under frequency deviations,significant DC-link voltage fluctuations ma...Frequency droop control is widely used in permanent magnet synchronous generators(PMSGs)based wind turbines(WTs)for grid frequency support.However,under frequency deviations,significant DC-link voltage fluctuations may occur during the transient process due to sudden changes in real power of such WTs.To address this issue,a current feedforward control strategy is proposed for PMSG-based WTs to reduce DC-link voltage fluctuations when the WTs are providing frequency support under grid frequency deviations.Meanwhile,the desired frequency support capability of the PMSG-based WTs can be ensured.Simulation results verify the rationality of the analysis and the effectiveness of the proposed control method.展开更多
The self-synchronizing voltage source inverter(SS VSI)is widely studied because of its grid-forming capability.However,the slow response of the active power control loop(APCL)under the weak grid makes it difficult for...The self-synchronizing voltage source inverter(SS VSI)is widely studied because of its grid-forming capability.However,the slow response of the active power control loop(APCL)under the weak grid makes it difficult for the SSVSI to quickly support the frequency of a low-inertia grid.In this pa per,a grid framework is established to analyze the frequency support service process of the SSVSI,and the shortcomings of the regulation of the damping coefficient and virtual inertia co efficient for frequency support are analyzed.Then,an adaptive additional damping control method is proposed to optimize the ability of SSVSI to support the grid frequency.The proposed control method adjusts the damping of the APCL without affect ing the system steady-state characteristics,which improves the active power response speed of the SSVSI.Besides,the pro posed control method adaptively adjusts the additional damp ing coefficient based on the active power response without mea suring the grid parameters.Compared with other forms of con trol,the proposed control method excels in minimizing the rate of change of frequency(RoCoF)and the frequency deviation(FD)within the grid,without succumbing to the constraints posed by unknown grid parameters.Furthermore,the analysis of the system stability is also presented.Finally,the experimen tal hardware results obtained from a miniaturized grid proto type are presented,corroborating the effectiveness of the pro posed control method.展开更多
Wind power plants(WPPs)are increasingly mandated to provide temporary frequency support to power systems during contingencies involving significant power shortages.However,the frequency support capabilities of WPPs un...Wind power plants(WPPs)are increasingly mandated to provide temporary frequency support to power systems during contingencies involving significant power shortages.However,the frequency support capabilities of WPPs under derated operations remain insufficiently investigated,highlighting the potential for further improvement of the frequency nadir.This paper proposes a bi-level optimized temporary frequency support(OTFS)strategy for a WPP.The implementation of the OTFS strategy is collaboratively accomplished by individual wind turbine(WT)controllers and the central WPP controller.First,to exploit the frequency support capability of WTs,the stable operational region of WTs is expanded by developing a novel dynamic power control approach in WT controllers.This approach synergizes the WTs'temporary frequency support with the secondary frequency control of synchronous generators,enabling WTs to release more kinetic energy without causing a secondary frequency drop.Second,a model predictive control strategy is developed for the WPP controller.This strategy ensures that multiple WTs operating within the expanded stable region are coordinated to minimize the magnitude of the frequency drop through efficient kinetic energy utilization.Finally,comprehensive case studies are conducted on a real-time simulation platform to validate the effectiveness of the proposed strategy.展开更多
Frequency support capability for the grid-connected converter(GCC)is one of the basic safeguards for the stability of renewables-dominated power systems.In this paper,analogous to the motion equation of a synchronous ...Frequency support capability for the grid-connected converter(GCC)is one of the basic safeguards for the stability of renewables-dominated power systems.In this paper,analogous to the motion equation of a synchronous generator(SG),an inertial phase-locked loop(iPLL)is proposed for GCC to achieve fast frequency support.The iPLL introduces the inertial and damping loops into the classic PLL structure to emulate the natural frequency regulation characteristics of a SG.Compared with the existing methods,the iPLL has a faster frequency response and is simpler in design and implementation.Finally,the proposed iPLL method is validated by experiments.Index Terms-Frequency support,grid-connected converter,inertial phase-locked loop(iPLL),synchronous generation(SG).展开更多
Due to their fast response and strong short-term power throughput capacity, electric vehicles(EVs) are promising for providing primary frequency support to power grids. However, due to the complicated charging demands...Due to their fast response and strong short-term power throughput capacity, electric vehicles(EVs) are promising for providing primary frequency support to power grids. However, due to the complicated charging demands of drivers, it is challenging to efficiently utilize the regulation capacity of EV clusters for providing stable primary frequency support to the power grid. Accordingly, this paper proposes an adaptive primary frequency support strategy for EV clusters constrained by the charging-behavior-defined operation area. First, the forced charging boundary of the EV is determined according to the driver's charging behavior, and based on this, the operation area is defined. This ensures full utilization of the available frequency support capacity of the EV. An adaptive primary frequency support strategy of EV clusters is then proposed. The output power of EV is adaptively regulated according to the real-time distance from the EV operating point to the forced charging boundary. With the proposed strategy, when the EV approaches the forced charging boundary, its output power is gradually reduced to zero. Then, the rapid state-of-charge declines of EVs and sudden output power reductions in EV clusters caused by forced charging to meet the driver's charging demands can be effectively avoided. EV clusters can then provide sustainable frequency support to the power grid without violating the driver's charging demands. Simulation results validate the proposed operation-area-constrained adaptive primary frequency support strategy, which outperforms the average strategy in terms of stable output maintenance and the optimal utilization of regulation capacities of EV clusters.展开更多
Energy storage systems(ESS)and permanent magnet synchronous generators(PMSG)are speculated to be able to exhibit frequency regulation capabilities by adding differential and proportional control loops with different c...Energy storage systems(ESS)and permanent magnet synchronous generators(PMSG)are speculated to be able to exhibit frequency regulation capabilities by adding differential and proportional control loops with different control objectives.The available PMSG kinetic energy and charging/discharging capacities of the ESS were restricted.To improve the inertia response and frequency control capability,we propose a short-term frequency support strategy for the ESS and PMSG.To this end,the weights were embedded in the control loops to adjust the participation of the differential and proportional controls based on the system frequency excursion.The effectiveness of the proposed control strategy was verified using PSCAD/EMTDC.The simulations revealed that the proposed strategy could improve the maximum rate of change of the frequency nadir and maximum frequency excursion.Therefore,it provides a promising solution of ancillary services for frequency regulation of PMSG and ESS.展开更多
In this paper, the method of relaxed boundary conditions is applied to rectangular plates with edges which are a sort of the mixture of simply supported portions and clamped portions, so that the lower limit of fundam...In this paper, the method of relaxed boundary conditions is applied to rectangular plates with edges which are a sort of the mixture of simply supported portions and clamped portions, so that the lower limit of fundamental frequency of such plates is evaluated. A kind of polynomial satisfying the displacement boundary conditions is designed, os that it is enabled to evaluate the upper limit of fundamental frequency by Ritz' method. The practical calculation examples solved by these methods have given satisfactory results. At the end of this paper, it is pointed out that the socalled exact solution of such plates usually evaluated by the force superposition method is essentially a kind of lower limit of solution, if the truncated error of series which occurs in actual calculation is considered.展开更多
The reduced frequency regulation capability in lowinertia power systems necessitates enhanced frequency support from photovoltaic(PV)systems.However,the regulation capability of PV system under conventional control sc...The reduced frequency regulation capability in lowinertia power systems necessitates enhanced frequency support from photovoltaic(PV)systems.However,the regulation capability of PV system under conventional control scheme is limited,which requires flexible power control and support from battery energy storage systems(BESSs).This paper proposes an energy management strategy of PV-BESS to provide stable frequency support to the grid.The proposed strategy initially develops a maximum power point tracking(MPPT)-based power reserve control(PRC)for PV power reserve.At this stage,the BESS is manipulated to buffer the power fluctuations caused by MPPT execution and environmental variability.To enhance the regulation capability of BESS and mitigate battery aging,the proposed strategy incorporates a flexible PRC for state of charge(SOC)recovery.Subsequently,the battery can be rationally charged or discharged during the PRC process to maintain SOC.Simulation results obtained from MATLAB/Simulink and experimental results from the StarSim platform validate that the proposed strategy achieves stable PV power reserve,mitigates fluctuations induced by environmental uncertainties,enables efficient SOC recovery,and improves grid frequency quality.Overall,the proposed strategy ensures stable operation of PV-BESS both under steady-state conditions and during frequency events.展开更多
The increasing integration of renewable energy sources poses great challenges to the power system frequency se curity.However,the existing electricity market mechanism lacks integration and incentives for emerging fre...The increasing integration of renewable energy sources poses great challenges to the power system frequency se curity.However,the existing electricity market mechanism lacks integration and incentives for emerging frequency regula tion(FR)resources such as wind power generators(WPGs),which may reduce their motivation to provide frequency sup port and further deteriorate the frequency dynamics.In this pa per,a market scheduling and pricing method for comprehen sive frequency regulation services(FRSs)is proposed.First,a modeling approach for flexible FR capabilities of WPGs is pro posed based on the mechanism of inertia control and power re serve control.Subsequently,considering the differences in in verter control strategies,a novel system frequency response model with grid-following and grid-forming inverters is estab lished.Combined with the automatic generation control,the fre quency security constraints of the whole FR process are de rived,and integrated into the market scheduling model to cooptimize the energy and FRSs.Finally,by distinguishing the contributions of various types of resources in different FR stag es,a differentiated pricing scheme is proposed to incentivize producers with various regulation qualities to provide FRSs.The effectiveness of the proposed method is verified on the mod ified IEEE 6-bus system and the IEEE RTS-79 system.展开更多
This paper presents exponential Atomic Basis Functions(ABF),which are called Eup(x;w).These functions are infinitely differentiable finite functions that unlike algebraic up(x)basis functions,have an unspecified param...This paper presents exponential Atomic Basis Functions(ABF),which are called Eup(x;w).These functions are infinitely differentiable finite functions that unlike algebraic up(x)basis functions,have an unspecified parameter-frequency w.Numerical experiments show that this class of atomic functions has good approximation properties,especially in the case of large gradients(Gibbs phenomenon).In this work,for the first time,the properties of exponential ABF are thoroughly investigated and the expression for calculating the value of the basis function at an arbitrary point of the domain is given in a form suitable for implementation in numerical analysis.Application of these basis functions is shown in the function approximation example.The procedure for determining the best frequencies,which gives the smallest approximation error in terms of the least squares method,is presented.展开更多
In order to investigate the effects of probe support on the stall characteristics of micro compressors, an experiment was carried out on a large-scale low-speed research compressor according to the principle of geomet...In order to investigate the effects of probe support on the stall characteristics of micro compressors, an experiment was carried out on a large-scale low-speed research compressor according to the principle of geometric similarity. A cylindrical probe support intruding to 50% blade span was mounted at 50% chord upstream from the rotor blade leading edge. The static pressure rise characteristic of the compressor is measured, with and without the probe support respectively. The dynamic compressor behavior from pre-stall to full stall was also measured. The results indicate that the stability margin of the compressor is lowered after installing the probe support. The stall inception is aroused by modal wave disturbances. The disturbances developed into two stall cells smoothly before installing the probe support, while the disturbances first developed into a single stall cell then splitting into two stall cells after installing the probe support. The presence of probe support lowers the initial intensity of the rotating stall of the compressor, while it doesn't alter the intensity of the rotation stall after the compressor enters into full stall.展开更多
This paper proposes a grid synchronization control strategy for the grid-connected voltage source converters(VSCs)based on the voltage dynamics of the DC-link capacitor in the VSC.The voltage dynamics of the DC-link c...This paper proposes a grid synchronization control strategy for the grid-connected voltage source converters(VSCs)based on the voltage dynamics of the DC-link capacitor in the VSC.The voltage dynamics of the DC-link capacitor are used to regulate the frequency and phase angle of the inner potential of the VSC,synchronizing the VSC with grid.Firstly,in the proposed strategy,the active power regulation and grid synchronization of the VSC are combined,which are separated in the traditional control strategy.This can avoid the instability of the VSC in a weak grid with a low short circuit ratio(SCR),aroused by the dynamic interaction between the separated control loops in traditional control strategies.Secondly,the energy stored in the DC-link capacitor is directly coupled with the grid via the inner potential of the VSC,and the inertia characteristic is naturally featured in the inner potential by the proposed strategy.With the increase of the capacitance,the natural inertial response of the VSC is helpful to improve the grid frequency dynamic.Finally,simulation results are presented to validate the correctness and effectiveness of the proposed strategy in the enhancement of the grid frequency and voltage dynamic support capability.展开更多
基金funded by the Science and Technology Project of State Grid Corporation,grant number 5500-202329500A-3-2-ZN,funding data 2023.10–2025.12.
文摘Aiming at the problems of large fluctuation of output active power and poor control performance in the process of frequency support of an energy-storage-type static-var-generator(ESVG),the adaptive adjustment control method for its active-loop parameters is used to realize thewind-farmfrequency support,which has become the current research hotspot.Taking the ESVG with a supercapacitor on the DC side as the research object,the influence trend of the change of virtual rotation inertia and virtual damping coefficient on its virtual angular velocity and power angle is analyzed.Then,the constraint relationship between the equivalent virtual inertia time constant of the supercapacitor and the virtual rotation inertia of the ESVG is clarified.Then,combined with the second-order response characteristics of the ESVG power control loop,the selection principles of the frequency modulation coefficient,the virtual rotation inertia,and the virtual damping coefficient are determined.An ESVG adjustment control method,considering the adaptive adjustment of the active loop parameters of the supercapacitor equivalent inertia,is proposed.While ensuring the frequency support capability of the ESVG,the fluctuation degree of its output active power and the virtual angular velocity are suppressed,and the proposed adjustment method also improves the stability of the ESVG control system and the frequency support capability for the wind farm.Finally,the simulation verifies the correctness of the theoretical analysis and the effectiveness of the proposed strategy.
文摘We report a comprehensive numerical study of super resolution (SR) structured illumination microscopy (SIM) utilizing the classic Heintzmann-Cremer SIM process and algorithm. In particular, we investigated the impact of the diffraction limit of the underlying imaging system on the optimal SIM grating frequency that can be used to obtain the highest SR enhancement with non-continuous spatial frequency support. Besides confirming the previous theoretical and experimental work that SR-SIM can achieve an enhancement close to 3 times the diffraction limit with grating pattern illuminations, we also observe and report a series of more subtle effects of SR-SIM with non-continuous spatial frequency support. Our simulations show that when the SIM grating frequency exceeds twice that of the diffraction limit, the higher SIM grating frequency can help achieve a higher SR enhancement for the underlying imaging systems whose diffraction limit is low, though this enhancement is obtained at the cost of losing resolution at some lower resolution targets. Our simulations also show that, for underlying imaging systems with high diffraction limits, however, SR-SIM grating frequencies above twice the diffraction limits tend to bring no significant extra enhancement. Furthermore, we observed that there exists a limit grating frequency above which the SR enhancement effect is lost, and the reconstructed images essentially have the same resolution as the one obtained directly from the underlying imaging system without using the SIM process.
基金This work is jointly supported by the National Key R&D Programme of China(No.2017YFB0902000)the National Natural Science Foundation of China(No.U1766206)the Science and Technology Programme of the State Grid Corporation(No.52110418000P).
文摘Frequency droop control is widely used in permanent magnet synchronous generators(PMSGs)based wind turbines(WTs)for grid frequency support.However,under frequency deviations,significant DC-link voltage fluctuations may occur during the transient process due to sudden changes in real power of such WTs.To address this issue,a current feedforward control strategy is proposed for PMSG-based WTs to reduce DC-link voltage fluctuations when the WTs are providing frequency support under grid frequency deviations.Meanwhile,the desired frequency support capability of the PMSG-based WTs can be ensured.Simulation results verify the rationality of the analysis and the effectiveness of the proposed control method.
基金supported by the Natural Science Foundation of China(No.52077070)Young Scientists Fund of National Natural Science Foundation of China(No.52207201)+1 种基金Hunan Provincial Natural Science Foundation of China(No.2024JJ3012)Young Scientists Fund of Hunan Provincial Natural Science Foundation of China(No.2024JJ6172).
文摘The self-synchronizing voltage source inverter(SS VSI)is widely studied because of its grid-forming capability.However,the slow response of the active power control loop(APCL)under the weak grid makes it difficult for the SSVSI to quickly support the frequency of a low-inertia grid.In this pa per,a grid framework is established to analyze the frequency support service process of the SSVSI,and the shortcomings of the regulation of the damping coefficient and virtual inertia co efficient for frequency support are analyzed.Then,an adaptive additional damping control method is proposed to optimize the ability of SSVSI to support the grid frequency.The proposed control method adjusts the damping of the APCL without affect ing the system steady-state characteristics,which improves the active power response speed of the SSVSI.Besides,the pro posed control method adaptively adjusts the additional damp ing coefficient based on the active power response without mea suring the grid parameters.Compared with other forms of con trol,the proposed control method excels in minimizing the rate of change of frequency(RoCoF)and the frequency deviation(FD)within the grid,without succumbing to the constraints posed by unknown grid parameters.Furthermore,the analysis of the system stability is also presented.Finally,the experimen tal hardware results obtained from a miniaturized grid proto type are presented,corroborating the effectiveness of the pro posed control method.
基金supported by the National Key R&D Program of China under Grant 2021YFB2400500。
文摘Wind power plants(WPPs)are increasingly mandated to provide temporary frequency support to power systems during contingencies involving significant power shortages.However,the frequency support capabilities of WPPs under derated operations remain insufficiently investigated,highlighting the potential for further improvement of the frequency nadir.This paper proposes a bi-level optimized temporary frequency support(OTFS)strategy for a WPP.The implementation of the OTFS strategy is collaboratively accomplished by individual wind turbine(WT)controllers and the central WPP controller.First,to exploit the frequency support capability of WTs,the stable operational region of WTs is expanded by developing a novel dynamic power control approach in WT controllers.This approach synergizes the WTs'temporary frequency support with the secondary frequency control of synchronous generators,enabling WTs to release more kinetic energy without causing a secondary frequency drop.Second,a model predictive control strategy is developed for the WPP controller.This strategy ensures that multiple WTs operating within the expanded stable region are coordinated to minimize the magnitude of the frequency drop through efficient kinetic energy utilization.Finally,comprehensive case studies are conducted on a real-time simulation platform to validate the effectiveness of the proposed strategy.
基金supported in part by the National Natural Science Foundation of China under Grant 52277180in part by the Delta Power Electronics Science and Education Development Program of Delta Group under Grant DREG2021005。
文摘Frequency support capability for the grid-connected converter(GCC)is one of the basic safeguards for the stability of renewables-dominated power systems.In this paper,analogous to the motion equation of a synchronous generator(SG),an inertial phase-locked loop(iPLL)is proposed for GCC to achieve fast frequency support.The iPLL introduces the inertial and damping loops into the classic PLL structure to emulate the natural frequency regulation characteristics of a SG.Compared with the existing methods,the iPLL has a faster frequency response and is simpler in design and implementation.Finally,the proposed iPLL method is validated by experiments.Index Terms-Frequency support,grid-connected converter,inertial phase-locked loop(iPLL),synchronous generation(SG).
基金supported by the Science and Technology Project of State Grid Corporation of China (No.5100-202199274A-0-0-00)。
文摘Due to their fast response and strong short-term power throughput capacity, electric vehicles(EVs) are promising for providing primary frequency support to power grids. However, due to the complicated charging demands of drivers, it is challenging to efficiently utilize the regulation capacity of EV clusters for providing stable primary frequency support to the power grid. Accordingly, this paper proposes an adaptive primary frequency support strategy for EV clusters constrained by the charging-behavior-defined operation area. First, the forced charging boundary of the EV is determined according to the driver's charging behavior, and based on this, the operation area is defined. This ensures full utilization of the available frequency support capacity of the EV. An adaptive primary frequency support strategy of EV clusters is then proposed. The output power of EV is adaptively regulated according to the real-time distance from the EV operating point to the forced charging boundary. With the proposed strategy, when the EV approaches the forced charging boundary, its output power is gradually reduced to zero. Then, the rapid state-of-charge declines of EVs and sudden output power reductions in EV clusters caused by forced charging to meet the driver's charging demands can be effectively avoided. EV clusters can then provide sustainable frequency support to the power grid without violating the driver's charging demands. Simulation results validate the proposed operation-area-constrained adaptive primary frequency support strategy, which outperforms the average strategy in terms of stable output maintenance and the optimal utilization of regulation capacities of EV clusters.
基金supported by Open Fund of National Engineering Research Center for Offshore Wind Power“Stabilization Mechanism and Control Technology of the Intelligent Wind-Storage Integration System Based on Voltage-Source and Self-Synchronizing Control(HSFD22007)”.
文摘Energy storage systems(ESS)and permanent magnet synchronous generators(PMSG)are speculated to be able to exhibit frequency regulation capabilities by adding differential and proportional control loops with different control objectives.The available PMSG kinetic energy and charging/discharging capacities of the ESS were restricted.To improve the inertia response and frequency control capability,we propose a short-term frequency support strategy for the ESS and PMSG.To this end,the weights were embedded in the control loops to adjust the participation of the differential and proportional controls based on the system frequency excursion.The effectiveness of the proposed control strategy was verified using PSCAD/EMTDC.The simulations revealed that the proposed strategy could improve the maximum rate of change of the frequency nadir and maximum frequency excursion.Therefore,it provides a promising solution of ancillary services for frequency regulation of PMSG and ESS.
文摘In this paper, the method of relaxed boundary conditions is applied to rectangular plates with edges which are a sort of the mixture of simply supported portions and clamped portions, so that the lower limit of fundamental frequency of such plates is evaluated. A kind of polynomial satisfying the displacement boundary conditions is designed, os that it is enabled to evaluate the upper limit of fundamental frequency by Ritz' method. The practical calculation examples solved by these methods have given satisfactory results. At the end of this paper, it is pointed out that the socalled exact solution of such plates usually evaluated by the force superposition method is essentially a kind of lower limit of solution, if the truncated error of series which occurs in actual calculation is considered.
基金supported by the National Natural Science Foundation of China(No.52207218)。
文摘The reduced frequency regulation capability in lowinertia power systems necessitates enhanced frequency support from photovoltaic(PV)systems.However,the regulation capability of PV system under conventional control scheme is limited,which requires flexible power control and support from battery energy storage systems(BESSs).This paper proposes an energy management strategy of PV-BESS to provide stable frequency support to the grid.The proposed strategy initially develops a maximum power point tracking(MPPT)-based power reserve control(PRC)for PV power reserve.At this stage,the BESS is manipulated to buffer the power fluctuations caused by MPPT execution and environmental variability.To enhance the regulation capability of BESS and mitigate battery aging,the proposed strategy incorporates a flexible PRC for state of charge(SOC)recovery.Subsequently,the battery can be rationally charged or discharged during the PRC process to maintain SOC.Simulation results obtained from MATLAB/Simulink and experimental results from the StarSim platform validate that the proposed strategy achieves stable PV power reserve,mitigates fluctuations induced by environmental uncertainties,enables efficient SOC recovery,and improves grid frequency quality.Overall,the proposed strategy ensures stable operation of PV-BESS both under steady-state conditions and during frequency events.
基金supported by the National Key Research and Development Program of China(No.2023YFB2406800).
文摘The increasing integration of renewable energy sources poses great challenges to the power system frequency se curity.However,the existing electricity market mechanism lacks integration and incentives for emerging frequency regula tion(FR)resources such as wind power generators(WPGs),which may reduce their motivation to provide frequency sup port and further deteriorate the frequency dynamics.In this pa per,a market scheduling and pricing method for comprehen sive frequency regulation services(FRSs)is proposed.First,a modeling approach for flexible FR capabilities of WPGs is pro posed based on the mechanism of inertia control and power re serve control.Subsequently,considering the differences in in verter control strategies,a novel system frequency response model with grid-following and grid-forming inverters is estab lished.Combined with the automatic generation control,the fre quency security constraints of the whole FR process are de rived,and integrated into the market scheduling model to cooptimize the energy and FRSs.Finally,by distinguishing the contributions of various types of resources in different FR stag es,a differentiated pricing scheme is proposed to incentivize producers with various regulation qualities to provide FRSs.The effectiveness of the proposed method is verified on the mod ified IEEE 6-bus system and the IEEE RTS-79 system.
文摘This paper presents exponential Atomic Basis Functions(ABF),which are called Eup(x;w).These functions are infinitely differentiable finite functions that unlike algebraic up(x)basis functions,have an unspecified parameter-frequency w.Numerical experiments show that this class of atomic functions has good approximation properties,especially in the case of large gradients(Gibbs phenomenon).In this work,for the first time,the properties of exponential ABF are thoroughly investigated and the expression for calculating the value of the basis function at an arbitrary point of the domain is given in a form suitable for implementation in numerical analysis.Application of these basis functions is shown in the function approximation example.The procedure for determining the best frequencies,which gives the smallest approximation error in terms of the least squares method,is presented.
基金funded by the National Natural Science Foundation of China(Grant No.51161130525 and 51136003)the 111 Project,No.B07009
文摘In order to investigate the effects of probe support on the stall characteristics of micro compressors, an experiment was carried out on a large-scale low-speed research compressor according to the principle of geometric similarity. A cylindrical probe support intruding to 50% blade span was mounted at 50% chord upstream from the rotor blade leading edge. The static pressure rise characteristic of the compressor is measured, with and without the probe support respectively. The dynamic compressor behavior from pre-stall to full stall was also measured. The results indicate that the stability margin of the compressor is lowered after installing the probe support. The stall inception is aroused by modal wave disturbances. The disturbances developed into two stall cells smoothly before installing the probe support, while the disturbances first developed into a single stall cell then splitting into two stall cells after installing the probe support. The presence of probe support lowers the initial intensity of the rotating stall of the compressor, while it doesn't alter the intensity of the rotation stall after the compressor enters into full stall.
基金supported by Science and Technology Project of Yunnan Power Grid Co.,Ltd.(No.YNKJXM20222105)。
文摘This paper proposes a grid synchronization control strategy for the grid-connected voltage source converters(VSCs)based on the voltage dynamics of the DC-link capacitor in the VSC.The voltage dynamics of the DC-link capacitor are used to regulate the frequency and phase angle of the inner potential of the VSC,synchronizing the VSC with grid.Firstly,in the proposed strategy,the active power regulation and grid synchronization of the VSC are combined,which are separated in the traditional control strategy.This can avoid the instability of the VSC in a weak grid with a low short circuit ratio(SCR),aroused by the dynamic interaction between the separated control loops in traditional control strategies.Secondly,the energy stored in the DC-link capacitor is directly coupled with the grid via the inner potential of the VSC,and the inertia characteristic is naturally featured in the inner potential by the proposed strategy.With the increase of the capacitance,the natural inertial response of the VSC is helpful to improve the grid frequency dynamic.Finally,simulation results are presented to validate the correctness and effectiveness of the proposed strategy in the enhancement of the grid frequency and voltage dynamic support capability.
