The frequency regulation reserve setting of wind-PV-storage power stations is crucial.However,the existing grid codes set up the station reserve in a static manner,where the synchronous generator characteristics and f...The frequency regulation reserve setting of wind-PV-storage power stations is crucial.However,the existing grid codes set up the station reserve in a static manner,where the synchronous generator characteristics and frequency-step disturbance scenario are considered.Thus,the advantages of flexible regulation of renewable generations are wasted,resulting in excessive curtailment of wind and solar resources.In this study,a method for optimizing the frequency regulation reserve of wind PV storage power stations was developed.Moreover,a station frequency regulation model was constructed,considering the field dynamic response and the coupling between the station and system frequency dynamics.Furthermore,a method for the online evaluation of the station frequency regulation was proposed based on the benchmark governor fitting.This method helps in overcoming the capacity-based reserve static setting.Finally,an optimization model was developed,along with the proposal of the linearized solving algorithm.The field data from the JH4#station in China’s MX power grid was considered for validation.The proposed method achieves a 24.77%increase in the station income while ensuring the system frequency stability when compared with the grid code-based method.展开更多
In high-renewable-energy power systems,the demand for fast-responding capabilities is growing.To address the limitations of conventional closed-loop frequency control,where the integral coefficient cannot dynamically ...In high-renewable-energy power systems,the demand for fast-responding capabilities is growing.To address the limitations of conventional closed-loop frequency control,where the integral coefficient cannot dynamically adjust the frequency regulation command based on the state of charge(SoC)of energy storage units,this paper proposes a secondary frequency regulation control strategy based on variable integral coefficients for multiple energy storage units.First,a power-uniform controller is designed to ensure that thermal power units gradually take on more regulation power during the frequency regulation process.Next,a control framework based on variable integral coefficients is proposed within the secondary frequency regulation model,along with an objective function that simultaneously considers both Automatic Generation Control(AGC)command tracking performance and SoC recovery requirements of energy storage units.Finally,a gradient descent optimization method is used to dynamically adjust the gain of the energy storage integral controller,allowingmultiple energy storage units to respond in real-time to AGC instructions and SoC variations.Simulation results confirmthe effectiveness of the proposedmethod.Compared to traditional strategies,the proposed approach takes into account the SoCdiscrepancies amongmultiple energy storage units and the duration of system net power imbalances.It successfully implements secondary frequency regulation while achieving dynamic power allocation among the units.展开更多
As the development of new power systems progresses,the inherent inertia of power systems continues to diminish.Centralized frequency regulation,which relies on rapid communication and real-time control,can enable inve...As the development of new power systems progresses,the inherent inertia of power systems continues to diminish.Centralized frequency regulation,which relies on rapid communication and real-time control,can enable inverter-based thermostatically controlled load(ITCL)clusters to provide virtual inertia support to the power grid.However,ITCL clusters exhibit significant discrete response characteristics,which precludes the direct integration of load-side inertia support into the synchronous unit side.To address this issue,this paper elaborates on the existing technical framework and analyzes the underlying causes of the problem.It proposes a timestamp allocation mechanism for ITCL cluster control instructions,ensuring that many ITCL terminals can be triggered at staggered times,thereby allowing the load cluster power to adhere to the inertia analog control law at any moment.Building on this foundation,the paper further examines the impact of the inertia response delay of ITCL clusters,which is based on centralized frequency regulation,on the stability of the power system.A design scheme for inertia analog control parameters is proposed,taking into account dual constraints,frequency stability and load cluster regulation capacity.Finally,the feasibility and applicability of the proposed mechanism and parameter design scheme are investigated through simulations conducted via MATLAB/Simulink.展开更多
Large-scale new energy grid connection leads to the weakening of the system frequency regulation capability,and the system frequency stability is facing unprecedented challenges.In order to solve rapid frequency fluct...Large-scale new energy grid connection leads to the weakening of the system frequency regulation capability,and the system frequency stability is facing unprecedented challenges.In order to solve rapid frequency fluctuation caused by new energy units,this paper proposes a new energy power system frequency regulation strategy with multiple units including the doubly-fed pumped storage unit(DFPSU).Firstly,based on the model predictive control(MPC)theory,the state space equations are established by considering the operating characteristics of the units and the dynamic behavior of the system;secondly,the proportional-differential control link is introduced to minimize the frequency deviation to further optimize the frequency modulation(FM)output of the DFPSU and inhibit the rapid fluctuation of the frequency;lastly,it is verified on theMatlab/Simulink simulation platform,and the results show that the model predictive control with proportional-differential control link can further release the FM potential of the DFPSU,increase the depth of its FM,effectively reduce the frequency deviation of the system and its rate of change,realize the optimization of the active output of the DFPSU and that of other units,and improve the frequency response capability of the system.展开更多
The large-scale popularization of electric vehicles(EVs)brings the potential for grid frequency regulation.Considering the characteristics of fast response and adjustment of EVs,two control strategies of automatic gen...The large-scale popularization of electric vehicles(EVs)brings the potential for grid frequency regulation.Considering the characteristics of fast response and adjustment of EVs,two control strategies of automatic generation control(AGC)with EVs are proposed responding to two high frequency regulating signals extracted from area control error(ACE)and area regulation requirement(ARR)by a digital filter,respectively.In order to dispatch regulation task to EVs,the capacity of regulation is calculated based on maximum V2G power and the present V2G power of EVs.Finally,simulations based on a two-area interconnected power system show that the proposed approaches can significantly suppress frequency deviation and reduce the active power output of traditional generation units.展开更多
The application of virtual synchronous generator(VSG)control in flywheel energy storage systems(FESS)is an effective solution for addressing the challenges related to reduced inertia and inadequate power supply in mic...The application of virtual synchronous generator(VSG)control in flywheel energy storage systems(FESS)is an effective solution for addressing the challenges related to reduced inertia and inadequate power supply in microgrids.Considering the significant variations among individual units within a flywheel array and the poor frequency regulation performance under conventional control approaches,this paper proposes an adaptive VSG control strategy for a flywheel energy storage array(FESA).First,by leveraging the FESA model,a variable acceleration factor is integrated into the speed-balance control strategy to effectively achieve better state of charge(SOC)equalization across units.Furthermore,energy control with a dead zone is introduced to prevent SOC of the FESA from exceeding the limit.The dead zone parameter is designed based on the SOC warning intervals of the flywheel array to mitigate its impact on regular operation.In addition,VSG technology is applied for the grid-connected control of the FESA,and the damping characteristic of the VSG is decoupled from the primary frequency regulation through power differential feedback.This ensures optimal dynamic performance while reducing the need for frequent involvement in frequency regulation.Subsequently,a parameter design method is developed through a small-signal stability analysis.Consequently,considering the SOC of the FESA,an adaptive control strategy for the inertia damping and the P/ωdroop coefficient of the VSG control is proposed to optimize the grid support services of the FESA.Finally,the effectiveness of the proposed control methods is demonstrated through electromagnetic transient simulations using MATLAB/Simulink.展开更多
An alternating current(AC)microgrid is a system that integrates renewable power,power converters,controllers and loads.Hierarchical control can manage the frequency of the microgrid to prevent imbalance and collapse o...An alternating current(AC)microgrid is a system that integrates renewable power,power converters,controllers and loads.Hierarchical control can manage the frequency of the microgrid to prevent imbalance and collapse of the system.The existing frequency control methods use traditional proportion integration(PI)controllers,which cannot adjust PI parameters in real-time to respond to the status changes of the system.Hierarchical control driven by fuzzy logic allows real-time adjustment of the PI parameters and the method used a two-layer control structure.The primary control used droop control to adjust power distribution,and fuzzy logic was used in the voltage loop of the primary control.The secondary control was added to make up for frequency deviation caused by droop control,and fuzzy logic was used in the secondary frequency control to deal with the dynamic change of frequency caused by the disturbances of loads.The proposed method was simulated in Matlab/Simulink.In the primary control,the proposed method reduced the total harmonic distortion(THD)of two cycles of the output voltage from 4.19%to 3.89%;in the secondary control,the proposed method reduced the frequency fluctuation of the system by about 0.03 Hz and 0.04 Hz when the load was increased and decreased,respectively.The results show that the proposed methods have a better effect on frequency maintenance and voltage control of the AC microgrid.展开更多
During electric vehicle(EV)-assisted grid frequency modulation,inconsistent state of charge(SOC)among EVs can result in overcharging and discharging of the batteries,affecting the stability of the electrical system.As...During electric vehicle(EV)-assisted grid frequency modulation,inconsistent state of charge(SOC)among EVs can result in overcharging and discharging of the batteries,affecting the stability of the electrical system.As a solution,this paper proposes a priority-based frequency regulation strategy for EVs.Firstly,models for the primary and secondary frequency regulation of EV-assisted power grids are established.Secondly,a consensus algorithm is used to construct a distributed com-munication system for EVs.Target SOC values are used to obtain a local frequency regulation priori-ty list.The list is used in an optimal control plan allowing individual EVs to participate in frequency regulation.Finally,a simulation of this strategy under several scenarios is conducted.The results indicate that the strategy ensures uniform SOC among the participating group of EVs,thereby avoi-ding overcharging and discharging of their batteries.It also reduces frequency fluctuations in the electrical system,making the system more robust compared with the frequency regulation strategy that is not priority-based.展开更多
The configuration of a hybrid energy storage system(HESS)plays a pivotal role in mitigating wind power fluctuations and enabling primary frequency regulation,thereby enhancing the active power support capability of wi...The configuration of a hybrid energy storage system(HESS)plays a pivotal role in mitigating wind power fluctuations and enabling primary frequency regulation,thereby enhancing the active power support capability of wind power integration systems.However,most existing studies on HESS capacity configuration overlook the selfrecovery control of the state of charge(SOC),creating challenges in sustaining capacity during long-term operation.This omission can impair frequency regulation performance,increase capacity requirements,and shorten battery lifespan.To address these challenges,this study proposes a bi-level planning–operation capacity configuration model that explicitly incorporates SOC self-recovery control.In the operation layer,a variable-baseline charging/discharging strategy is developed to restore SOC by balancing positive and negative energy over a 24-h period,with the goal of maximizing daily operational benefits.In the planning layer,the annualized net life-cycle cost of the HESS isminimized by configuring storage capacity based on feedback fromthe operation layer.Thetwo layers operate iteratively to achieve coordinated optimization of capacity sizing and control strategy.Case study results demonstrate the effectiveness of the proposed method.Compared with a configuration without considering SOC self-recovery,the proposed approach reduces the 1-min wind power fluctuation rate to 3.53%,lowers the mean squared frequency error to 0.000084,and decreases the annualized net life-cycle cost by 545,000 CNY/MWh.展开更多
Main Exhauster is one of the main equipment of sintering production. It needs to consume a lot of electricity. Therefore, the system＇ s reconstruction for energy-saving will effectively reduce electricity for the pro...Main Exhauster is one of the main equipment of sintering production. It needs to consume a lot of electricity. Therefore, the system＇ s reconstruction for energy-saving will effectively reduce electricity for the production. The paper takes an iron and steel enterprise that had successfully transformed the synchronous motors of main exhauster of sintering as an example, which describes the application of high-voltage variable frequency speed regulation system in main exhauster of Sintering, so as to provide a reference for other iron and steel enterprises.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
The increasing penetration of renewable energy resources and reduced system inertia pose risks to frequency security of power systems,necessitating the development of fast frequency regulation(FFR)methods using flexib...The increasing penetration of renewable energy resources and reduced system inertia pose risks to frequency security of power systems,necessitating the development of fast frequency regulation(FFR)methods using flexible resources.However,developing effective FFR policies is challenging because different power system operating conditions require distinct regulation logics.Traditional fixed-coefficient linear droop-based control methods are suboptimal for managing the diverse conditions encountered.This paper proposes a dynamic nonlinear P-f droop-based FFR method using a newly established meta-reinforcement learning(meta-RL)approach to enhance control adaptability while ensuring grid stability.First,we model the optimal FFR problem under various operating conditions as a set of Markov decision processes and accordingly formulate the frequency stability-constrained meta-RL problem.To address this,we then construct a novel hierarchical neural network(HNN)structure that incorporates a theoretical frequency stability guarantee,thereby converting the constrained meta-RL problem into a more tractable form.Finally,we propose a two-stage algorithm that leverages the inherent characteristics of the problem,achieving enhanced optimality in solving the HNN-based meta-RL problem.Simulations validate that the proposed FFR method shows superior adaptability across different operating conditions,and achieves better trade-offs between regulation performance and cost than benchmarks.展开更多
The virtual power plant(VPP)facilitates the coordinated optimization of diverse forms of electrical energy through the aggregation and control of distributed energy resources(DERs),offering as a potential resource for...The virtual power plant(VPP)facilitates the coordinated optimization of diverse forms of electrical energy through the aggregation and control of distributed energy resources(DERs),offering as a potential resource for frequency regulation to enhance the power system flexibility.To fully exploit the flexibility of DER and enhance the revenue of VPP,this paper proposes a multi-temporal optimization strategy of VPP in the energy-frequency regulation(EFR)market under the uncertainties of wind power(WP),photovoltaic(PV),and market price.Firstly,all schedulable electric vehicles(EVs)are aggregated into an electric vehicle cluster(EVC),and the schedulable domain evaluation model of EVC is established.A day-ahead energy bidding model based on Stackelberg game is also established for VPP and EVC.Secondly,on this basis,the multi-temporal optimization model of VPP in the EFR market is proposed.To manage risks stemming from the uncertainties of WP,PV,and market price,the concept of conditional value at risk(CVaR)is integrated into the strategy,effectively balancing the bidding benefits and associated risks.Finally,the results based on operational data from a provincial electricity market demonstrate that the proposed strategy enhances comprehensive revenue by providing frequency regulation services and encouraging EV response scheduling.展开更多
This study investigates a safe reinforcement learning algorithm for grid-forming(GFM)inverter based frequency regulation.To guarantee the stability of the inverter-based resource(IBR)system under the learned control p...This study investigates a safe reinforcement learning algorithm for grid-forming(GFM)inverter based frequency regulation.To guarantee the stability of the inverter-based resource(IBR)system under the learned control policy,a modelbased reinforcement learning(MBRL)algorithm is combined with Lyapunov approach,which determines the safe region of states and actions.To obtain near optimal control policy,the control performance is safely improved by approximate dynamic programming(ADP)using data sampled from the region of attraction(ROA).Moreover,to enhance the control robustness against parameter uncertainty in the inverter,a Gaussian process(GP)model is adopted by the proposed algorithm to effectively learn system dynamics from measurements.Numerical simulations validate the effectiveness of the proposed algorithm.展开更多
New energy-vehicle charging and discharging units in vehicle to grid(V2G)application scenarios experience long and large transient fluctuations in power and frequency at their power injection points.Furthermore,the po...New energy-vehicle charging and discharging units in vehicle to grid(V2G)application scenarios experience long and large transient fluctuations in power and frequency at their power injection points.Furthermore,the power matching degree is low,which has a serious impact on the V2G support performance.This paper proposes a two-step model prediction-virtual synchronous machine(MPC-VSG)control strategy that considers the SOC of the charging and discharging unit.First,the VSG equivalent model of the V2G grid-connected inverter is established,and the power weight coefficients of the charging and discharging unit SOC participating in frequency regulation are obtained by analyzing its characteristics.Second,the power change prediction value is obtained from the VSG model,and the two-step prediction of the reference frequency is performed to reduce the error of the reference value remaining unchanged at the instant of sudden power change.Minimizing the sum of squares of real-time output power deviations and frequency fluctuations as a cost function to compensate for the optimal active losses and suppress the frequency transient fluctuations.Finally,simulation analysis is carried out under the working conditions of island mode operation,V2G grid-connected operation,and wind power multi-energy complementary operation,and an experimental verification of the inverter part is carried out to verify the effectiveness and superiority of the proposed control strategy.展开更多
With the increased penetration of renewable energy sources,the grid-forming(GFM)energy storage(ES)has been considered to engage in primary frequency regulation(PFR),often necessitating the use of a frequency deadband(...With the increased penetration of renewable energy sources,the grid-forming(GFM)energy storage(ES)has been considered to engage in primary frequency regulation(PFR),often necessitating the use of a frequency deadband(FDB)to prevent excessive battery charging cycling and mitigate frequency oscillations.Implementing the FDB is relatively straightforward in grid-following(GFL)control.However,implementing the FDB in GFM control presents a significant challenge since the inverter must abstain from providing active power at any frequency within the FDB.Therefore,in this paper,the performance of PFR control in the GFM-ES inverter is analyzed in detail first.Then,the FDB is implemented for GFM inverters with various types of synchronization methods,and the need for inertia response is also considered.Moreover,given the risk of oscillations near the FDB boundary,different FDB setting methods are proposed and examined,where an improved triangular hysteresis method is proposed to realize the fast response and enhanced stability.Finally,the simulation and experiment results are provided to verify the effectiveness of the above methods.展开更多
Islanded microgrids(IMGs)offer a viable and efficient energy self-sustaining solution for distributed resources in remote areas.While without utility grid support,the frequency of IMG is susceptible to mismatches betw...Islanded microgrids(IMGs)offer a viable and efficient energy self-sustaining solution for distributed resources in remote areas.While without utility grid support,the frequency of IMG is susceptible to mismatches between demand and generation.Moreover,IMGs encounter uncertain and nonlinear load disturbances together with system parameter perturbation,which further compromises frequency stability.To this aim,this paper proposes a robust multi-virtual synchronous generators(multi-VSGs)coordinated control strategy for distributed secondary frequency regulation(DSFR)in IMGs,which exhibits minimal model dependency and avoids reliance on global information.Two critical methods are developed:(1)a robust VSG control framework that incorporates the linear active disturbance rejection control(LADRC)technique,which enables the estimation and effective elimination of uncertain load disturbances and system's parameter perturbations;(2)a novel secondorder consensus algorithm-based control law for robust secondary frequency regulation,which is featured with proper power sharing among different participants,suppressed power oscillation caused by response disparities,and reduced reliance on complex communication system.Building on methods(1)and(2),a novel multi-VSGs coordinated control strategy is proposed,providing a robust solution for IMG's frequency restoration,and its dynamic characteristics are explored in detail.The correctness and effectiveness of the proposal are verified by both simulation and the hardware-in-the-loop(HIL)experiment results across typical scenarios.展开更多
Data centers are promising demand-side flexible resources that can provide frequency regulation services to power grids.While most existing studies focus on individual data centers,coordinating multiple geo-distribute...Data centers are promising demand-side flexible resources that can provide frequency regulation services to power grids.While most existing studies focus on individual data centers,coordinating multiple geo-distributed data centers can significantly enhance operational flexibility and market participation.However,the inherent uncertainty in both data center workloads and regulation signals pose significant challenges to maintaining effective operations,let alone determining regulation capacity offerings.To address these challenges,this paper proposes a coordinated bidding strategy for electricity purchases and regulation capacity offerings for multiple geo-distributed data centers in electricity markets.This strategy expands the feasible region of operational decisions,including workload dispatch,server activation,and cooling behaviors.To enhance the participation of data centers in frequency regulation services under uncertainty,chance-constrained programming is adopted.This paper presents explicit models for these uncertainties involved,starting with the Poisson-distributed workloads and then addressing the unpredictable regulation signals.Numerical experiments based on real-world datasets validate the effectiveness of the proposed strategy compared with state-of-the-art strategies.展开更多
With increasing adoption of intermittent renewable generation,challenges to maintain stable frequencies for power systems are increasing.Demand-side resources,such as thermostatically controlled loads(TCLs),have been ...With increasing adoption of intermittent renewable generation,challenges to maintain stable frequencies for power systems are increasing.Demand-side resources,such as thermostatically controlled loads(TCLs),have been proven capable of providing regulation services.The district cooling system(DCS),a type of centralized TCL that provides cooling services for a group of buildings,is an ideal resource for this purpose.A DCS usually has significant regulation flexibility because its rated power capacity is large(up to 100 MW)and it can utilize thermal inertia of an aggregation of buildings.However,as a large-scale system with complex thermal dynamics,its effective regulation is nontrivial,and its traditional demanddriven control scheme has difficulty considering regulation signals from power systems.To address these challenges,we propose a bidirectional-driven control scheme in a DCS for the first time.On this basis,we formulate the thermal and electricity model of a DCS in the frequency domain and derive an equivalent model to control it like a traditional generator.Furthermore,we propose a sensitivity-based control strategy for a DCS to allocate mass flow adjustments among buildings,which effectively considers heterogeneity of buildings to balance temperature impacts.Numerical studies illustrate effectiveness of the proposed model and control strategy.展开更多
As the proportion of renewable energy(RE)increases,the inertia and the primary frequency regulation(FR)capability of the power system decrease.Thus,ensuring frequency security in the scheduling model has become a new ...As the proportion of renewable energy(RE)increases,the inertia and the primary frequency regulation(FR)capability of the power system decrease.Thus,ensuring frequency security in the scheduling model has become a new technical requirement in power systems with a high share of RE.Due to a shortage of conventional synchronous generators,the frequency support of multi-source converters has become an indispensable part of the system frequency resources,especially variable-speed wind turbine generation(WTG)and battery energy storage(BES).Quantitative expression of the FR capability of multi-source converters is necessary to construct frequency-constrained scheduling model.However,the frequency support performance of these converter-interfaced devices is related to their working states,operation modes,and parameters,and the complex coupling of these factors has not been fully exploited in existing models.In this study,we propose an integrated frequency-constrained scheduling model considering the coordination of FR capabilities from multi-source converters.Switchable FR control strategies and variable FR parameters for WTG with or without reserved power are modeled,and multi-target allocation of BES capacity between tracking dispatch instruction and emergency FR is analyzed.Then,the variable FR capabilities of WTG and BES are embedded into the integrated frequency-constrained scheduling model.The nonlinear constraints for frequency security are precisely linearized through an improved iteration-based strategy.The effectiveness of the proposed model is verified in a modified IEEE 24-bus standard system.The results suggest that the coordinated participation of BES and WTG in FR can effectively reduce the cost of the scheduling model while meeting frequency security constraints.展开更多
基金supported by the Scientific Research Project of China Three Gorges Group Co.LTD(Contract Number:202103368).
文摘The frequency regulation reserve setting of wind-PV-storage power stations is crucial.However,the existing grid codes set up the station reserve in a static manner,where the synchronous generator characteristics and frequency-step disturbance scenario are considered.Thus,the advantages of flexible regulation of renewable generations are wasted,resulting in excessive curtailment of wind and solar resources.In this study,a method for optimizing the frequency regulation reserve of wind PV storage power stations was developed.Moreover,a station frequency regulation model was constructed,considering the field dynamic response and the coupling between the station and system frequency dynamics.Furthermore,a method for the online evaluation of the station frequency regulation was proposed based on the benchmark governor fitting.This method helps in overcoming the capacity-based reserve static setting.Finally,an optimization model was developed,along with the proposal of the linearized solving algorithm.The field data from the JH4#station in China’s MX power grid was considered for validation.The proposed method achieves a 24.77%increase in the station income while ensuring the system frequency stability when compared with the grid code-based method.
文摘In high-renewable-energy power systems,the demand for fast-responding capabilities is growing.To address the limitations of conventional closed-loop frequency control,where the integral coefficient cannot dynamically adjust the frequency regulation command based on the state of charge(SoC)of energy storage units,this paper proposes a secondary frequency regulation control strategy based on variable integral coefficients for multiple energy storage units.First,a power-uniform controller is designed to ensure that thermal power units gradually take on more regulation power during the frequency regulation process.Next,a control framework based on variable integral coefficients is proposed within the secondary frequency regulation model,along with an objective function that simultaneously considers both Automatic Generation Control(AGC)command tracking performance and SoC recovery requirements of energy storage units.Finally,a gradient descent optimization method is used to dynamically adjust the gain of the energy storage integral controller,allowingmultiple energy storage units to respond in real-time to AGC instructions and SoC variations.Simulation results confirmthe effectiveness of the proposedmethod.Compared to traditional strategies,the proposed approach takes into account the SoCdiscrepancies amongmultiple energy storage units and the duration of system net power imbalances.It successfully implements secondary frequency regulation while achieving dynamic power allocation among the units.
基金supported by the Key Scientific and Technological Projects(2024KJGG27)of Tianfu Yongxing Laboratorythe Experimental Platform Open Innovation Funding(209042025003)of Sichuan Energy Internet Research Institute,Tsinghua University.
文摘As the development of new power systems progresses,the inherent inertia of power systems continues to diminish.Centralized frequency regulation,which relies on rapid communication and real-time control,can enable inverter-based thermostatically controlled load(ITCL)clusters to provide virtual inertia support to the power grid.However,ITCL clusters exhibit significant discrete response characteristics,which precludes the direct integration of load-side inertia support into the synchronous unit side.To address this issue,this paper elaborates on the existing technical framework and analyzes the underlying causes of the problem.It proposes a timestamp allocation mechanism for ITCL cluster control instructions,ensuring that many ITCL terminals can be triggered at staggered times,thereby allowing the load cluster power to adhere to the inertia analog control law at any moment.Building on this foundation,the paper further examines the impact of the inertia response delay of ITCL clusters,which is based on centralized frequency regulation,on the stability of the power system.A design scheme for inertia analog control parameters is proposed,taking into account dual constraints,frequency stability and load cluster regulation capacity.Finally,the feasibility and applicability of the proposed mechanism and parameter design scheme are investigated through simulations conducted via MATLAB/Simulink.
基金supported by the National Natural Science Foundation of China(Project No.52377082)the Scientific Research Program of Jilin Provincial Department of Education(Project No.JJKH20230123KJ).
文摘Large-scale new energy grid connection leads to the weakening of the system frequency regulation capability,and the system frequency stability is facing unprecedented challenges.In order to solve rapid frequency fluctuation caused by new energy units,this paper proposes a new energy power system frequency regulation strategy with multiple units including the doubly-fed pumped storage unit(DFPSU).Firstly,based on the model predictive control(MPC)theory,the state space equations are established by considering the operating characteristics of the units and the dynamic behavior of the system;secondly,the proportional-differential control link is introduced to minimize the frequency deviation to further optimize the frequency modulation(FM)output of the DFPSU and inhibit the rapid fluctuation of the frequency;lastly,it is verified on theMatlab/Simulink simulation platform,and the results show that the model predictive control with proportional-differential control link can further release the FM potential of the DFPSU,increase the depth of its FM,effectively reduce the frequency deviation of the system and its rate of change,realize the optimization of the active output of the DFPSU and that of other units,and improve the frequency response capability of the system.
基金This work was supported by Sino-US international Science and Technology Cooperation Project(Grant No.2016YFE0105300).
文摘The large-scale popularization of electric vehicles(EVs)brings the potential for grid frequency regulation.Considering the characteristics of fast response and adjustment of EVs,two control strategies of automatic generation control(AGC)with EVs are proposed responding to two high frequency regulating signals extracted from area control error(ACE)and area regulation requirement(ARR)by a digital filter,respectively.In order to dispatch regulation task to EVs,the capacity of regulation is calculated based on maximum V2G power and the present V2G power of EVs.Finally,simulations based on a two-area interconnected power system show that the proposed approaches can significantly suppress frequency deviation and reduce the active power output of traditional generation units.
基金National Natural Science Foundation of China(51977160)“Voltage Self balancing Control Method for Modular Multilevel Converter Based on Switching State Matrix”.
文摘The application of virtual synchronous generator(VSG)control in flywheel energy storage systems(FESS)is an effective solution for addressing the challenges related to reduced inertia and inadequate power supply in microgrids.Considering the significant variations among individual units within a flywheel array and the poor frequency regulation performance under conventional control approaches,this paper proposes an adaptive VSG control strategy for a flywheel energy storage array(FESA).First,by leveraging the FESA model,a variable acceleration factor is integrated into the speed-balance control strategy to effectively achieve better state of charge(SOC)equalization across units.Furthermore,energy control with a dead zone is introduced to prevent SOC of the FESA from exceeding the limit.The dead zone parameter is designed based on the SOC warning intervals of the flywheel array to mitigate its impact on regular operation.In addition,VSG technology is applied for the grid-connected control of the FESA,and the damping characteristic of the VSG is decoupled from the primary frequency regulation through power differential feedback.This ensures optimal dynamic performance while reducing the need for frequent involvement in frequency regulation.Subsequently,a parameter design method is developed through a small-signal stability analysis.Consequently,considering the SOC of the FESA,an adaptive control strategy for the inertia damping and the P/ωdroop coefficient of the VSG control is proposed to optimize the grid support services of the FESA.Finally,the effectiveness of the proposed control methods is demonstrated through electromagnetic transient simulations using MATLAB/Simulink.
基金National Natural Science Foundation of China(No.62303107)Fundamental Research Funds for the Central Universities,China(Nos.2232022G-09 and 2232021D-38)Shanghai Sailing Program,China(No.21YF1400100)。
文摘An alternating current(AC)microgrid is a system that integrates renewable power,power converters,controllers and loads.Hierarchical control can manage the frequency of the microgrid to prevent imbalance and collapse of the system.The existing frequency control methods use traditional proportion integration(PI)controllers,which cannot adjust PI parameters in real-time to respond to the status changes of the system.Hierarchical control driven by fuzzy logic allows real-time adjustment of the PI parameters and the method used a two-layer control structure.The primary control used droop control to adjust power distribution,and fuzzy logic was used in the voltage loop of the primary control.The secondary control was added to make up for frequency deviation caused by droop control,and fuzzy logic was used in the secondary frequency control to deal with the dynamic change of frequency caused by the disturbances of loads.The proposed method was simulated in Matlab/Simulink.In the primary control,the proposed method reduced the total harmonic distortion(THD)of two cycles of the output voltage from 4.19%to 3.89%;in the secondary control,the proposed method reduced the frequency fluctuation of the system by about 0.03 Hz and 0.04 Hz when the load was increased and decreased,respectively.The results show that the proposed methods have a better effect on frequency maintenance and voltage control of the AC microgrid.
基金Supported by the China Postdoctoral Science Foundation(No.2022M710039).
文摘During electric vehicle(EV)-assisted grid frequency modulation,inconsistent state of charge(SOC)among EVs can result in overcharging and discharging of the batteries,affecting the stability of the electrical system.As a solution,this paper proposes a priority-based frequency regulation strategy for EVs.Firstly,models for the primary and secondary frequency regulation of EV-assisted power grids are established.Secondly,a consensus algorithm is used to construct a distributed com-munication system for EVs.Target SOC values are used to obtain a local frequency regulation priori-ty list.The list is used in an optimal control plan allowing individual EVs to participate in frequency regulation.Finally,a simulation of this strategy under several scenarios is conducted.The results indicate that the strategy ensures uniform SOC among the participating group of EVs,thereby avoi-ding overcharging and discharging of their batteries.It also reduces frequency fluctuations in the electrical system,making the system more robust compared with the frequency regulation strategy that is not priority-based.
基金supported by Graduate Research and Innovation Program Project of Nanjing Institute of Technology(No.TB202517022).
文摘The configuration of a hybrid energy storage system(HESS)plays a pivotal role in mitigating wind power fluctuations and enabling primary frequency regulation,thereby enhancing the active power support capability of wind power integration systems.However,most existing studies on HESS capacity configuration overlook the selfrecovery control of the state of charge(SOC),creating challenges in sustaining capacity during long-term operation.This omission can impair frequency regulation performance,increase capacity requirements,and shorten battery lifespan.To address these challenges,this study proposes a bi-level planning–operation capacity configuration model that explicitly incorporates SOC self-recovery control.In the operation layer,a variable-baseline charging/discharging strategy is developed to restore SOC by balancing positive and negative energy over a 24-h period,with the goal of maximizing daily operational benefits.In the planning layer,the annualized net life-cycle cost of the HESS isminimized by configuring storage capacity based on feedback fromthe operation layer.Thetwo layers operate iteratively to achieve coordinated optimization of capacity sizing and control strategy.Case study results demonstrate the effectiveness of the proposed method.Compared with a configuration without considering SOC self-recovery,the proposed approach reduces the 1-min wind power fluctuation rate to 3.53%,lowers the mean squared frequency error to 0.000084,and decreases the annualized net life-cycle cost by 545,000 CNY/MWh.
文摘Main Exhauster is one of the main equipment of sintering production. It needs to consume a lot of electricity. Therefore, the system＇ s reconstruction for energy-saving will effectively reduce electricity for the production. The paper takes an iron and steel enterprise that had successfully transformed the synchronous motors of main exhauster of sintering as an example, which describes the application of high-voltage variable frequency speed regulation system in main exhauster of Sintering, so as to provide a reference for other iron and steel enterprises.
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.
基金supported by the Key Research and Development Program of Inner Mongolia,China(No.2021ZD0039).
文摘The increasing penetration of renewable energy resources and reduced system inertia pose risks to frequency security of power systems,necessitating the development of fast frequency regulation(FFR)methods using flexible resources.However,developing effective FFR policies is challenging because different power system operating conditions require distinct regulation logics.Traditional fixed-coefficient linear droop-based control methods are suboptimal for managing the diverse conditions encountered.This paper proposes a dynamic nonlinear P-f droop-based FFR method using a newly established meta-reinforcement learning(meta-RL)approach to enhance control adaptability while ensuring grid stability.First,we model the optimal FFR problem under various operating conditions as a set of Markov decision processes and accordingly formulate the frequency stability-constrained meta-RL problem.To address this,we then construct a novel hierarchical neural network(HNN)structure that incorporates a theoretical frequency stability guarantee,thereby converting the constrained meta-RL problem into a more tractable form.Finally,we propose a two-stage algorithm that leverages the inherent characteristics of the problem,achieving enhanced optimality in solving the HNN-based meta-RL problem.Simulations validate that the proposed FFR method shows superior adaptability across different operating conditions,and achieves better trade-offs between regulation performance and cost than benchmarks.
基金supported in part by the National Natural Science Foundation of China(No.52477115)(Shanxi)Regional Innovation and Development Joint Fund Project(No.U21A600003).
文摘The virtual power plant(VPP)facilitates the coordinated optimization of diverse forms of electrical energy through the aggregation and control of distributed energy resources(DERs),offering as a potential resource for frequency regulation to enhance the power system flexibility.To fully exploit the flexibility of DER and enhance the revenue of VPP,this paper proposes a multi-temporal optimization strategy of VPP in the energy-frequency regulation(EFR)market under the uncertainties of wind power(WP),photovoltaic(PV),and market price.Firstly,all schedulable electric vehicles(EVs)are aggregated into an electric vehicle cluster(EVC),and the schedulable domain evaluation model of EVC is established.A day-ahead energy bidding model based on Stackelberg game is also established for VPP and EVC.Secondly,on this basis,the multi-temporal optimization model of VPP in the EFR market is proposed.To manage risks stemming from the uncertainties of WP,PV,and market price,the concept of conditional value at risk(CVaR)is integrated into the strategy,effectively balancing the bidding benefits and associated risks.Finally,the results based on operational data from a provincial electricity market demonstrate that the proposed strategy enhances comprehensive revenue by providing frequency regulation services and encouraging EV response scheduling.
基金funded in part by the CURENT Research Center and in part by the National Science Foundation(NSF)(No.ECCS-2033910)。
文摘This study investigates a safe reinforcement learning algorithm for grid-forming(GFM)inverter based frequency regulation.To guarantee the stability of the inverter-based resource(IBR)system under the learned control policy,a modelbased reinforcement learning(MBRL)algorithm is combined with Lyapunov approach,which determines the safe region of states and actions.To obtain near optimal control policy,the control performance is safely improved by approximate dynamic programming(ADP)using data sampled from the region of attraction(ROA).Moreover,to enhance the control robustness against parameter uncertainty in the inverter,a Gaussian process(GP)model is adopted by the proposed algorithm to effectively learn system dynamics from measurements.Numerical simulations validate the effectiveness of the proposed algorithm.
基金Supported by the National Natural Science Foundation of China(61903291)Key R&D Project in Shaanxi Province(2022GY-134)Open Fund Project of New Energy Joint Laboratory of China Southern Power Grid Corporation(GDXNY2022KF01).
文摘New energy-vehicle charging and discharging units in vehicle to grid(V2G)application scenarios experience long and large transient fluctuations in power and frequency at their power injection points.Furthermore,the power matching degree is low,which has a serious impact on the V2G support performance.This paper proposes a two-step model prediction-virtual synchronous machine(MPC-VSG)control strategy that considers the SOC of the charging and discharging unit.First,the VSG equivalent model of the V2G grid-connected inverter is established,and the power weight coefficients of the charging and discharging unit SOC participating in frequency regulation are obtained by analyzing its characteristics.Second,the power change prediction value is obtained from the VSG model,and the two-step prediction of the reference frequency is performed to reduce the error of the reference value remaining unchanged at the instant of sudden power change.Minimizing the sum of squares of real-time output power deviations and frequency fluctuations as a cost function to compensate for the optimal active losses and suppress the frequency transient fluctuations.Finally,simulation analysis is carried out under the working conditions of island mode operation,V2G grid-connected operation,and wind power multi-energy complementary operation,and an experimental verification of the inverter part is carried out to verify the effectiveness and superiority of the proposed control strategy.
基金supported by the Science and Technology of State Grid(No.4000-202432066A-1-1-Z)。
文摘With the increased penetration of renewable energy sources,the grid-forming(GFM)energy storage(ES)has been considered to engage in primary frequency regulation(PFR),often necessitating the use of a frequency deadband(FDB)to prevent excessive battery charging cycling and mitigate frequency oscillations.Implementing the FDB is relatively straightforward in grid-following(GFL)control.However,implementing the FDB in GFM control presents a significant challenge since the inverter must abstain from providing active power at any frequency within the FDB.Therefore,in this paper,the performance of PFR control in the GFM-ES inverter is analyzed in detail first.Then,the FDB is implemented for GFM inverters with various types of synchronization methods,and the need for inertia response is also considered.Moreover,given the risk of oscillations near the FDB boundary,different FDB setting methods are proposed and examined,where an improved triangular hysteresis method is proposed to realize the fast response and enhanced stability.Finally,the simulation and experiment results are provided to verify the effectiveness of the above methods.
基金supported by the National Natural Science Foundation of China(Grant Nos.U22B20104,52407080,52277090,52207097)the International Science and Technology Cooperation Program of China(Grant No.2022YFE0129300)+2 种基金the Science and Technology Innovation Program of Hunan Province(Grant No.2023RC3102)the Excellent Innovation Youth Program of Changsha of China(Grant No.kq2209010)the Key Research and Development Program of Hunan Province(Grant No.2023GK2007)。
文摘Islanded microgrids(IMGs)offer a viable and efficient energy self-sustaining solution for distributed resources in remote areas.While without utility grid support,the frequency of IMG is susceptible to mismatches between demand and generation.Moreover,IMGs encounter uncertain and nonlinear load disturbances together with system parameter perturbation,which further compromises frequency stability.To this aim,this paper proposes a robust multi-virtual synchronous generators(multi-VSGs)coordinated control strategy for distributed secondary frequency regulation(DSFR)in IMGs,which exhibits minimal model dependency and avoids reliance on global information.Two critical methods are developed:(1)a robust VSG control framework that incorporates the linear active disturbance rejection control(LADRC)technique,which enables the estimation and effective elimination of uncertain load disturbances and system's parameter perturbations;(2)a novel secondorder consensus algorithm-based control law for robust secondary frequency regulation,which is featured with proper power sharing among different participants,suppressed power oscillation caused by response disparities,and reduced reliance on complex communication system.Building on methods(1)and(2),a novel multi-VSGs coordinated control strategy is proposed,providing a robust solution for IMG's frequency restoration,and its dynamic characteristics are explored in detail.The correctness and effectiveness of the proposal are verified by both simulation and the hardware-in-the-loop(HIL)experiment results across typical scenarios.
基金supported in part by the Science and Technology Development FundMacao SARChina(No.001/2024/SKL,No.0053/2022/AMJ)。
文摘Data centers are promising demand-side flexible resources that can provide frequency regulation services to power grids.While most existing studies focus on individual data centers,coordinating multiple geo-distributed data centers can significantly enhance operational flexibility and market participation.However,the inherent uncertainty in both data center workloads and regulation signals pose significant challenges to maintaining effective operations,let alone determining regulation capacity offerings.To address these challenges,this paper proposes a coordinated bidding strategy for electricity purchases and regulation capacity offerings for multiple geo-distributed data centers in electricity markets.This strategy expands the feasible region of operational decisions,including workload dispatch,server activation,and cooling behaviors.To enhance the participation of data centers in frequency regulation services under uncertainty,chance-constrained programming is adopted.This paper presents explicit models for these uncertainties involved,starting with the Poisson-distributed workloads and then addressing the unpredictable regulation signals.Numerical experiments based on real-world datasets validate the effectiveness of the proposed strategy compared with state-of-the-art strategies.
文摘With increasing adoption of intermittent renewable generation,challenges to maintain stable frequencies for power systems are increasing.Demand-side resources,such as thermostatically controlled loads(TCLs),have been proven capable of providing regulation services.The district cooling system(DCS),a type of centralized TCL that provides cooling services for a group of buildings,is an ideal resource for this purpose.A DCS usually has significant regulation flexibility because its rated power capacity is large(up to 100 MW)and it can utilize thermal inertia of an aggregation of buildings.However,as a large-scale system with complex thermal dynamics,its effective regulation is nontrivial,and its traditional demanddriven control scheme has difficulty considering regulation signals from power systems.To address these challenges,we propose a bidirectional-driven control scheme in a DCS for the first time.On this basis,we formulate the thermal and electricity model of a DCS in the frequency domain and derive an equivalent model to control it like a traditional generator.Furthermore,we propose a sensitivity-based control strategy for a DCS to allocate mass flow adjustments among buildings,which effectively considers heterogeneity of buildings to balance temperature impacts.Numerical studies illustrate effectiveness of the proposed model and control strategy.
基金supported by the National Key Research and Development Program of China(No.2021YFB2400500)the Science and Technology Project of State Grid Corporation of China“Fast control of photovoltaic and wind power plant for transient frequency/voltage support”.
文摘As the proportion of renewable energy(RE)increases,the inertia and the primary frequency regulation(FR)capability of the power system decrease.Thus,ensuring frequency security in the scheduling model has become a new technical requirement in power systems with a high share of RE.Due to a shortage of conventional synchronous generators,the frequency support of multi-source converters has become an indispensable part of the system frequency resources,especially variable-speed wind turbine generation(WTG)and battery energy storage(BES).Quantitative expression of the FR capability of multi-source converters is necessary to construct frequency-constrained scheduling model.However,the frequency support performance of these converter-interfaced devices is related to their working states,operation modes,and parameters,and the complex coupling of these factors has not been fully exploited in existing models.In this study,we propose an integrated frequency-constrained scheduling model considering the coordination of FR capabilities from multi-source converters.Switchable FR control strategies and variable FR parameters for WTG with or without reserved power are modeled,and multi-target allocation of BES capacity between tracking dispatch instruction and emergency FR is analyzed.Then,the variable FR capabilities of WTG and BES are embedded into the integrated frequency-constrained scheduling model.The nonlinear constraints for frequency security are precisely linearized through an improved iteration-based strategy.The effectiveness of the proposed model is verified in a modified IEEE 24-bus standard system.The results suggest that the coordinated participation of BES and WTG in FR can effectively reduce the cost of the scheduling model while meeting frequency security constraints.
