This paper deeply introduces a brand-new research method for the synchronous characteristics of DC microgrid bus voltage and an improved synchronous control strategy.This method mainly targets the problem of bus volta...This paper deeply introduces a brand-new research method for the synchronous characteristics of DC microgrid bus voltage and an improved synchronous control strategy.This method mainly targets the problem of bus voltage oscillation caused by the bifurcation behavior of DC microgrid converters.Firstly,the article elaborately establishes a mathematical model of a single distributed power source with hierarchical control.On this basis,a smallworld network model that can better adapt to the topology structure of DC microgrids is further constructed.Then,a voltage synchronization analysis method based on the main stability function is proposed,and the synchronous characteristics of DC bus voltage are deeply studied by analyzing the size of the minimum non-zero eigenvalue.In view of the situation that the line coupling strength between distributed power sources is insufficient to achieve bus voltage synchronization,this paper innovatively proposes a new improved adaptive controller to effectively control voltage synchronization.And the convergence of the designed controller is strictly proved by using Lyapunov’s stability theorem.Finally,the effectiveness and feasibility of the designed controller in this paper are fully verified through detailed simulation experiments.After comparative analysis with the traditional adaptive controller,it is found that the newly designed controller can make the bus voltages of each distributed power source achieve synchronization more quickly,and is significantly superior to the traditional adaptive controller in terms of anti-interference performance.展开更多
Low-voltage direct current(DC)microgrids have recently emerged as a promising and viable alternative to traditional alternating cur-rent(AC)microgrids,offering numerous advantages.Consequently,researchers are explorin...Low-voltage direct current(DC)microgrids have recently emerged as a promising and viable alternative to traditional alternating cur-rent(AC)microgrids,offering numerous advantages.Consequently,researchers are exploring the potential of DC microgrids across var-ious configurations.However,despite the sustainability and accuracy offered by DC microgrids,they pose various challenges when integrated into modern power distribution systems.Among these challenges,fault diagnosis holds significant importance.Rapid fault detection in DC microgrids is essential to maintain stability and ensure an uninterrupted power supply to critical loads.A primary chal-lenge is the lack of standards and guidelines for the protection and safety of DC microgrids,including fault detection,location,and clear-ing procedures for both grid-connected and islanded modes.In response,this study presents a brief overview of various approaches for protecting DC microgrids.展开更多
Conventional coordinated control strategies for DC bus voltage signal(DBS)in islanded DC microgrids(IDCMGs)struggle with coordinating multiple distributed generators(DGs)and cannot effectively incorporate state of cha...Conventional coordinated control strategies for DC bus voltage signal(DBS)in islanded DC microgrids(IDCMGs)struggle with coordinating multiple distributed generators(DGs)and cannot effectively incorporate state of charge(SOC)information of the energy storage system,thereby reducing the system flexibility.In this study,we propose an adaptive coordinated control strategy that employs a two-layer fuzzy neural network controller(FNNC)to adapt to varying operating conditions in an IDCMG with multiple PV and battery energy storage system(BESS)units.The first-layer FNNC generates optimal operating mode commands for each DG,thereby avoiding the requirement for complex operating modes based on SOC segmentation.An optimal switching sequence logic prioritizes the most appropriate units during mode transitions.The second-layer FNNC dynamically adjusts the droop power to overcome power distribution challenges among DG groups.This helps in preventing the PV power from exceeding the limits and mitigating the risk of BESS overcharging or over-discharging.The simulation results indicate that the proposed strategy enhances the coordinated operation of multi-DG IDCMGs,thereby ensuring the efficient and safe utilization of PV and BESS.展开更多
This article presents a distributed periodic eventtriggered(PET)optimal control scheme to achieve generation cost minimization and average bus voltage regulation in DC microgrids.In order to accommodate the generation...This article presents a distributed periodic eventtriggered(PET)optimal control scheme to achieve generation cost minimization and average bus voltage regulation in DC microgrids.In order to accommodate the generation constraints of the distributed generators(DGs),a virtual incremental cost is firstly designed,based on which an optimality condition is derived to facilitate the control design.To meet the discrete-time(DT)nature of modern control systems,the optimal controller is directly developed in the DT domain.Afterward,to reduce the communication requirement among the controllers,a distributed event-triggered mechanism is introduced for the DT optimal controller.The event-triggered condition is detected periodically and therefore naturally avoids the Zeno phenomenon.The closed-loop system stability is proved by the Lyapunov synthesis for switched systems.The generation cost minimization and average bus voltage regulation are obtained at the equilibrium point.Finally,switch-level microgrid simulations validate the performance of the proposed optimal controller.展开更多
In this paper,a grid interface current control strategy is presented for a DC microgrid,which aims to reduce the disturbance from PV generation and the load variation to the main grid without a grid interface converte...In this paper,a grid interface current control strategy is presented for a DC microgrid,which aims to reduce the disturbance from PV generation and the load variation to the main grid without a grid interface converter.The grid interface current is directly controlled by a battery DC-DC converter within the DC microgrid.Based on a comprehensive analysis of the battery DC-DC converter and interface current control,the control system has been mathematically modelled.This enabled two transfer functions to be derived that reflect the dynamic response of the inductor current to the duty cycle variation(inner loop),and the dynamic response of the grid interface current to the inductor current variation(outer loop).Experimental study has been done to assess the effectiveness of the proposed control strategy.The experimental results indicate that the proposed control strategy has a good performance to control the grid interface current without an interface converter,regardless the variations of both PV and the load conditions.展开更多
A single-bus DC microgrid can represent a wide range of applications.Control objectives of such systems include high-performance bus voltage regulation and proper load sharing among multiple distributed generators(DGs...A single-bus DC microgrid can represent a wide range of applications.Control objectives of such systems include high-performance bus voltage regulation and proper load sharing among multiple distributed generators(DGs)under various operating conditions.This paper presents a novel decentralized control algorithm that can guarantee both the transient voltage control performance and realize the predefined load sharing percentages.First,the output-constrained control problem is transformed into an equivalent unconstrained one.Second,a two-step backstepping control algorithm is designed based on the transformed model for bus-voltage regulation.Since the overall control effort can be split proportionally and calculated with locally-measurable signals,decentralized load sharing can be realized.The control design requires neither accurate parameters of the output filters nor load measurement.The stability of the transformed systems under the proposed control algorithm can indirectly guarantee the transient bus voltage performance of the original system.Additionally,the high-performance control design is robust,flexible,and reliable.Switch-level simulations under both normal and fault operating conditions demonstrate the effectiveness of the proposed algorithm.展开更多
Electrifying the on-board subsystems of aircraft becomes an inevitable process as being faced with the environmental pollution,along with the proposed concept called more electric aircraft(MEA).With the increasing num...Electrifying the on-board subsystems of aircraft becomes an inevitable process as being faced with the environmental pollution,along with the proposed concept called more electric aircraft(MEA).With the increasing number of on-board power electronic based devices,the distribution system of the aircraft can be regarded as an onboard microgrid.As it is known that the load power electronic converters can exhibit constant power load(CPL)characteristics and reduce the system stability,it is necessary to accurately predict and enhance the system stability in designing process.This paper firstly analyzes the stability of an on-board DC microgrid with the presence of CPL.Then,discusses the reasons behind instability and proposes a control strategy to enhance system stability.Finally,the simulation results are worked out to validate the analysis and the effect of the proposed control strategy.展开更多
In light of the growing integration of renewable energy sources in power systems,the adoption of DC microgrids has become increasingly popular,due to its simple structure,having no frequency,power factor concerns.Howe...In light of the growing integration of renewable energy sources in power systems,the adoption of DC microgrids has become increasingly popular,due to its simple structure,having no frequency,power factor concerns.However,the dependence of DC microgrids on cyber-networks also makes them susceptible to cyber-attacks.Potential cyberattacks can disrupt power system facilities and result in significant economic and loss of life.To address this concern,this paper presents an attack-resilient control strategy for microgrids to ensure voltage regulation and power sharing with stable operation under cyber-attack on the actuators.This paper first formulates the cyber-security problem considering a distributed generation based microgrid using the converter model,after which an attack-resilient control is proposed to eliminate the actuator attack impact on the system.Steady state analysis and root locus validation illustrate the feasibility of the proposed method.The effectiveness of the proposed control scheme is demonstrated through simulation results.展开更多
The DC microgrid has the advantages of high energy conversion efficiency,high energy transmission density,no reactive power flow,and grid-connected synchronization.It is an essential component of the future intelligen...The DC microgrid has the advantages of high energy conversion efficiency,high energy transmission density,no reactive power flow,and grid-connected synchronization.It is an essential component of the future intelligent power distribution system.Constant power load(CPL)will degrade the stability of the DC microgrid and cause system voltage oscillation due to its negative resistance characteristics.As a result,the stability of DC microgrids with CPL has become a problem.At present,the research on the stability of DC microgrid is mainly focused on unipolar DC microgrid,while the research on bipolar DC microgrid lacks systematic discussion.The stability of DC microgrid using CPL was studied first,and then the current stability criteria of DC microgrid were summarized,and its research trend was analyzed.On this basis,aiming at the stability problem caused by CPL,the existing control methods were summarized from the perspective of source converter output impedance and load converter input impedance,and the current control methods were outlined as active and passive control methods.Lastly,the research path of bipolar DC microgrid stability with CPL was prospected.展开更多
DC-DC converter-based multi-bus DC microgrids(MGs) in series have received much attention, where the conflict between voltage recovery and current balancing has been a hot topic. The lack of models that accurately por...DC-DC converter-based multi-bus DC microgrids(MGs) in series have received much attention, where the conflict between voltage recovery and current balancing has been a hot topic. The lack of models that accurately portray the electrical characteristics of actual MGs while is controller design-friendly has kept the issue active. To this end, this paper establishes a large-signal model containing the comprehensive dynamical behavior of the DC MGs based on the theory of high-order fully actuated systems, and proposes distributed optimal control based on this. The proposed secondary control method can achieve the two goals of voltage recovery and current sharing for multi-bus DC MGs. Additionally, the simple structure of the proposed approach is similar to one based on droop control, which allows this control technique to be easily implemented in a variety of modern microgrids with different configurations. In contrast to existing studies, the process of controller design in this paper is closely tied to the actual dynamics of the MGs. It is a prominent feature that enables engineers to customize the performance metrics of the system. In addition, the analysis of the stability of the closed-loop DC microgrid system, as well as the optimality and consensus of current sharing are given. Finally, a scaled-down solar and battery-based microgrid prototype with maximum power point tracking controller is developed in the laboratory to experimentally test the efficacy of the proposed control method.展开更多
During the operation of a DC microgrid,the nonlinearity and low damping characteristics of the DC bus make it prone to oscillatory instability.In this paper,we first establish a discrete nonlinear system dynamic model...During the operation of a DC microgrid,the nonlinearity and low damping characteristics of the DC bus make it prone to oscillatory instability.In this paper,we first establish a discrete nonlinear system dynamic model of a DC microgrid,study the effects of the converter sag coefficient,input voltage,and load resistance on the microgrid stability,and reveal the oscillation mechanism of a DC microgrid caused by a single source.Then,a DC microgrid stability analysis method based on the combination of bifurcation and strobe is used to analyze how the aforementioned parameters influence the oscillation characteristics of the system.Finally,the stability region of the system is obtained by the Jacobi matrix eigenvalue method.Grid simulation verifies the feasibility and effectiveness of the proposed method.展开更多
In this paper,an improved sag control strategy based on automatic SOC equalization is proposed to solve the problems of slow SOC equalization and excessive bus voltage fluctuation amplitude and offset caused by load a...In this paper,an improved sag control strategy based on automatic SOC equalization is proposed to solve the problems of slow SOC equalization and excessive bus voltage fluctuation amplitude and offset caused by load and PV power variations in a stand-alone DC microgrid.The strategy includes primary and secondary control.Among them,the primary control suppresses the DC microgrid voltage fluctuation through the I and II section control,and the secondary control aims to correct the P-U curve of the energy storage system and the PV system,thus reducing the steady-state bus voltage excursion.The simulation results demonstrate that the proposed control strategy effectively achieves SOC balancing and enhances the immunity of bus voltage.The proposed strategy improves the voltage fluctuation suppression ability by approximately 39.4%and 43.1%under the PV power and load power fluctuation conditions,respectively.Furthermore,the steady-state deviation of the bus voltage,△U_(dc) is only 0.01–0.1 V,ensuring stable operation of the DC microgrid in fluctuating power environments.展开更多
This paper presents performance analysis on hybrid AC/DC microgrid networks for residential home cluster. The design of the proposed microgrid includes comprehensive types of Distributed Generators (DGs) as hybrid pow...This paper presents performance analysis on hybrid AC/DC microgrid networks for residential home cluster. The design of the proposed microgrid includes comprehensive types of Distributed Generators (DGs) as hybrid power sources (wind, Photovoltaic (PV) solar cell, battery, fuel cell). Details about each DG dynamic modeling are presented and discussed. The customers in home cluster can be connected in both of the operating modes: islanded to the microgrid or connected to utility grid. Each DG has appended control system with its modeling that will be discussed to control DG performance. The wind turbine will be controlled by AC control system within three sub-control systems: 1) speed regulator and pitch control, 2) rotor side converter control, and 3) grid side converter control. The AC control structure is based on PLL, current regulator and voltage booster converter with using of photovoltaic Voltage Source Converter (VSC) and inverters to connect to the grid. The DC control system is mainly based on Maximum Power Point Tracking (MPPT) controller and boost converter connected to the PV array block and in order to control the system. The case study is used to analyze the performance of the proposed microgrid. The buses voltages, active power and reactive power responses are presented in both of grid-connected and islanded modes. In addition, the power factor, Total Harmonic Distortion (THD) and modulation index are calculated.展开更多
The dynamic average consensus(DAC)algorithm is to enable a group of networked agents to track the average of their time-varying reference signals.For most existing DAC algorithms,a necessary assumption is that the upp...The dynamic average consensus(DAC)algorithm is to enable a group of networked agents to track the average of their time-varying reference signals.For most existing DAC algorithms,a necessary assumption is that the upper bounds of the reference signals and their derivatives are known in advance,thereby posing significant challenges in practical scenarios.Introducing adaptive gains in DAC algorithms provides a remedy by relaxing this assumption.However,the current adaptive gains used in this type of DAC algorithms are non-decreasing and may increase to infinity if persist disturbance exists.In order to overcome this defect,this paper presents a novel DAC algorithm with modified adaptive gains.This approach obviates the necessity for prior knowledge concerning the upper bounds of the reference signals and their derivatives.Moreover,the adaptive gains are able to remain bounded even in the presence of external disturbances.Furthermore,the proposed adaptive DAC algorithm is employed to address the distributed secondary control problem of DC microgrids.Comparative case studies are provided to verify the superiority of the proposed DAC algorithm.展开更多
In this paper,a set of distributed secondary controllers is introduced that provide active regulation for both steady-state and transient-state performances of an islanded DC microgrid(MG).The secondary control for di...In this paper,a set of distributed secondary controllers is introduced that provide active regulation for both steady-state and transient-state performances of an islanded DC microgrid(MG).The secondary control for distributed converter interfaced generation(DCIG)not only guarantees that the system converges to the desired operating states in the steady state but also regulates the state variations to a prescribed transient-state performance.Compared with state-of-the-art techniques of distributed secondary control,this paper achieves accurate steady-state secondary regulations with prescribed transient-state performance in an islanded DC MG.Moreover,the applicability of the proposed control does not rely on any explicit knowledge of the system topology or physical parameters.Detailed controller designs are provided,and the system under control is proved to be Lyapunov stable using large-signal stability analysis.The steady-state and transient-state performances of the system are analyzed.The paper proves that as the perturbed system converges,the proposed control achieves accurate proportional power sharing and average voltage regulation among the DCIGs,and the transient variations of the operating voltages and power outputs at each DCIG are regulated to the prescribed transient-state performance.The effectiveness of the proposed control is validated via a four-DCIG MG system.展开更多
To achieve global voltage regulation and current sharing with reduced communication demands while enhancing the transient voltage performance of DC microgrid(MG)clusters,this paper proposes a distributed cooperative c...To achieve global voltage regulation and current sharing with reduced communication demands while enhancing the transient voltage performance of DC microgrid(MG)clusters,this paper proposes a distributed cooperative control method featuring output constraints and a dynamic event-triggered average consensus algorithm.The proposed control strategy employs an integrated primary-secondary control structure,where a dynamic event-triggered robust average consensus algorithm(DET-RACA)-based average voltage observer is designed to estimate the average voltage of each distributed generator(DG)within the MG.This estimated average voltage is subsequently utilized to simultaneously achieve voltage regulation and precise current sharing within individual MGs.Furthermore,an outputconstrained voltage controller incorporating a barrier Lyapunov function is developed to ensure high-performance transient voltage regulation for each DG.At the tertiary control level,a DET-RACA-based current observer is implemented to acquire global current information across the MG cluster,enabling the adjustment of bus reference voltages for each MG and guaranteeing global current sharing.The distinctive feature of DETRACA lies in its event-triggering mechanism,which significantly reduces communication frequency across the network topology and effectively alleviates the communication burden of the MG cluster system.Comprehensive simulations under five different operating conditions demonstrate the effectiveness and feasibility of the proposed method for DC MG cluster control.展开更多
This paper proposes an active islanding method based on impedance measurement for DC microgrids with multiple distributed generators(DGs).In the various presented methods,impedance-based islanding detection faces chal...This paper proposes an active islanding method based on impedance measurement for DC microgrids with multiple distributed generators(DGs).In the various presented methods,impedance-based islanding detection faces challenges in DC microgrids with multiple DGs due to the randomness of renewable energy.In the proposed method,the virtual impedance controls are designed to reshape the output impedance of DGs and the input impedance of loads at the detection frequency to ensure a clear distinction between grid-connected conditions and islanding conditions.Thus,the islanding events can be effectively detected under conditions that lead to a distinct decrease in system impedance.In this way,the accuracy of islanding detection is improved.Moreover,a dynamic allocation of the role algorithm is proposed to organize the orderly disturbance injection of DGs without communication,avoiding disturbance dilution.In addition,the selection principle of the frequency of disturbance current is proposed by studying the sensitivity of the point of common coupling(PCC)voltage to the disturbance.As a result,the negative influence of multiple DGs,loads,and disturbance dilution can be avoided compared to the existing methods.Finally,the effectiveness of the proposed method has been verified by both simulation and experimental results.展开更多
An adaptive droop control strategy is proposed for a parallel distributed multi-energy storage system of an isolated DC microgrid with unmatched line impedance and abnormal communication.System line impedance mismatch...An adaptive droop control strategy is proposed for a parallel distributed multi-energy storage system of an isolated DC microgrid with unmatched line impedance and abnormal communication.System line impedance mismatch can cause unbalanced load power distribution and reduce service life of distributed energy storage unit(DESU).Therefore,an improved droop control based on mixed coefficient compensation of state of charge(SOC)and voltage is designed,which can adaptively adjust a power characteristic curve according to the sampling period,so as to ensure precise distribution of load power while minimizing voltage deviation.Considering the stability of the system under communication anomaly,a non-communication backup control based on Metropolis acceptance criterion is proposed,which only uses internal data to adaptively adjust the droop coefficient.In addition,a gradual smooth handover strategy is designed through gradient coefficient to optimize control stability under communication anomaly.Finally,effectiveness and correctness of the proposed control strategy are verified by mathematical analysis and RTDS/DSP hardware-in-the-loop experiments.展开更多
Hybrid energy storage system(HESS)is an effective solution to address power imbalance problems caused by variability of renewable energy resources and load fluctuations in DC microgrids.The goal of HESS is to efficien...Hybrid energy storage system(HESS)is an effective solution to address power imbalance problems caused by variability of renewable energy resources and load fluctuations in DC microgrids.The goal of HESS is to efficiently utilize different types of energy storage systems,each with its unique characteristics.Normally,the energy management of HESS relies on centralized control methods,which have limitations in flexibility,scalability,and reliability.This paper proposes an innovative artifi-cial neural network(ANN)based model predictive control(MPC)method,integrated with a decentralized pow-er-sharing strategy for HESS.In the proposed technique,MPC is employed as an expert to provide data to train the ANN.Once the ANN is finely tuned,it is directly utilized to control the DC-DC converters,eliminating the need for the extensive computations typically required by conven-tional MPC.In the proposed control scheme,virtual re-sistance droop control for fuel cell(FC)and virtual ca-pacitance droop control for battery are designed in a decentralized manner to achieve power-sharing,enhance lifespan,and ensure HESS stability.As a result,the FC is able to support steady state loads,while the battery han-dles rapid load variations.Simulation results using Matlab/Simulink demonstrate the effective performance of the proposed controller under different loads and input variations,showcasing improved performance compared to conventional MPC.展开更多
Renewable energy sources have developed rapidly in recent years.In particular,isolated direct current(DC)microgrids have emerged as new grid structures for the comprehensive utilization of renewable energy and have go...Renewable energy sources have developed rapidly in recent years.In particular,isolated direct current(DC)microgrids have emerged as new grid structures for the comprehensive utilization of renewable energy and have good development prospects in industrial fields.However,the stability analysis of isolated DC microgrids still faces a significant challenge owing to the strong coupling of power converters and abundant transient processes.Thus,a new stability analysis framework for isolated DC microgrids is provided.In detail,the multi-timescale characteristics and stability issues of isolated DC microgrids are first analyzed,and three timescales are defined:the switching period timescale,device control timescale,and system control timescale.Subsequently,the existing stability indices of the microgrids are introduced,and a stability analysis framework for isolated DC microgrids is proposed based on the three defined timescales in this study.Finally,future research directions for the stability of isolated DC microgrids are discussed,and conclusions are drawn.The proposed stability analysis framework provides a reference for solving the stability problems in isolated DC microgrids,such as wide-frequency-band oscillations and the offset of the AC frequency.展开更多
基金supported by the National Natural Science Foundation of China(Nos.51767017 and 51867015)the Basic Research and Innovation Group Project of Gansu(No.18JR3RA13)the Major Science and Technology Project of Gansu(No.19ZD2GA003).
文摘This paper deeply introduces a brand-new research method for the synchronous characteristics of DC microgrid bus voltage and an improved synchronous control strategy.This method mainly targets the problem of bus voltage oscillation caused by the bifurcation behavior of DC microgrid converters.Firstly,the article elaborately establishes a mathematical model of a single distributed power source with hierarchical control.On this basis,a smallworld network model that can better adapt to the topology structure of DC microgrids is further constructed.Then,a voltage synchronization analysis method based on the main stability function is proposed,and the synchronous characteristics of DC bus voltage are deeply studied by analyzing the size of the minimum non-zero eigenvalue.In view of the situation that the line coupling strength between distributed power sources is insufficient to achieve bus voltage synchronization,this paper innovatively proposes a new improved adaptive controller to effectively control voltage synchronization.And the convergence of the designed controller is strictly proved by using Lyapunov’s stability theorem.Finally,the effectiveness and feasibility of the designed controller in this paper are fully verified through detailed simulation experiments.After comparative analysis with the traditional adaptive controller,it is found that the newly designed controller can make the bus voltages of each distributed power source achieve synchronization more quickly,and is significantly superior to the traditional adaptive controller in terms of anti-interference performance.
文摘Low-voltage direct current(DC)microgrids have recently emerged as a promising and viable alternative to traditional alternating cur-rent(AC)microgrids,offering numerous advantages.Consequently,researchers are exploring the potential of DC microgrids across var-ious configurations.However,despite the sustainability and accuracy offered by DC microgrids,they pose various challenges when integrated into modern power distribution systems.Among these challenges,fault diagnosis holds significant importance.Rapid fault detection in DC microgrids is essential to maintain stability and ensure an uninterrupted power supply to critical loads.A primary chal-lenge is the lack of standards and guidelines for the protection and safety of DC microgrids,including fault detection,location,and clear-ing procedures for both grid-connected and islanded modes.In response,this study presents a brief overview of various approaches for protecting DC microgrids.
基金supported by National Key R&D Program of ChinaunderGrant,(2021YFB2601403).
文摘Conventional coordinated control strategies for DC bus voltage signal(DBS)in islanded DC microgrids(IDCMGs)struggle with coordinating multiple distributed generators(DGs)and cannot effectively incorporate state of charge(SOC)information of the energy storage system,thereby reducing the system flexibility.In this study,we propose an adaptive coordinated control strategy that employs a two-layer fuzzy neural network controller(FNNC)to adapt to varying operating conditions in an IDCMG with multiple PV and battery energy storage system(BESS)units.The first-layer FNNC generates optimal operating mode commands for each DG,thereby avoiding the requirement for complex operating modes based on SOC segmentation.An optimal switching sequence logic prioritizes the most appropriate units during mode transitions.The second-layer FNNC dynamically adjusts the droop power to overcome power distribution challenges among DG groups.This helps in preventing the PV power from exceeding the limits and mitigating the risk of BESS overcharging or over-discharging.The simulation results indicate that the proposed strategy enhances the coordinated operation of multi-DG IDCMGs,thereby ensuring the efficient and safe utilization of PV and BESS.
基金supported by the U.S.Office of Naval Research(N00014-21-1-2175)。
文摘This article presents a distributed periodic eventtriggered(PET)optimal control scheme to achieve generation cost minimization and average bus voltage regulation in DC microgrids.In order to accommodate the generation constraints of the distributed generators(DGs),a virtual incremental cost is firstly designed,based on which an optimality condition is derived to facilitate the control design.To meet the discrete-time(DT)nature of modern control systems,the optimal controller is directly developed in the DT domain.Afterward,to reduce the communication requirement among the controllers,a distributed event-triggered mechanism is introduced for the DT optimal controller.The event-triggered condition is detected periodically and therefore naturally avoids the Zeno phenomenon.The closed-loop system stability is proved by the Lyapunov synthesis for switched systems.The generation cost minimization and average bus voltage regulation are obtained at the equilibrium point.Finally,switch-level microgrid simulations validate the performance of the proposed optimal controller.
基金funding from the U.K.EPSRC UKRI Innovation Fellowship scheme(EP/S001662/2)the European Union’s Horizon 2020 research and innovation programme under grant agreement No.734796.
文摘In this paper,a grid interface current control strategy is presented for a DC microgrid,which aims to reduce the disturbance from PV generation and the load variation to the main grid without a grid interface converter.The grid interface current is directly controlled by a battery DC-DC converter within the DC microgrid.Based on a comprehensive analysis of the battery DC-DC converter and interface current control,the control system has been mathematically modelled.This enabled two transfer functions to be derived that reflect the dynamic response of the inductor current to the duty cycle variation(inner loop),and the dynamic response of the grid interface current to the inductor current variation(outer loop).Experimental study has been done to assess the effectiveness of the proposed control strategy.The experimental results indicate that the proposed control strategy has a good performance to control the grid interface current without an interface converter,regardless the variations of both PV and the load conditions.
基金supported in part by the U.S.Office of Naval Research(N00014-16-1-3121,N00014-18-1-2185)the National Natural Science Foundation of China(61673347,U1609214,61751205)
文摘A single-bus DC microgrid can represent a wide range of applications.Control objectives of such systems include high-performance bus voltage regulation and proper load sharing among multiple distributed generators(DGs)under various operating conditions.This paper presents a novel decentralized control algorithm that can guarantee both the transient voltage control performance and realize the predefined load sharing percentages.First,the output-constrained control problem is transformed into an equivalent unconstrained one.Second,a two-step backstepping control algorithm is designed based on the transformed model for bus-voltage regulation.Since the overall control effort can be split proportionally and calculated with locally-measurable signals,decentralized load sharing can be realized.The control design requires neither accurate parameters of the output filters nor load measurement.The stability of the transformed systems under the proposed control algorithm can indirectly guarantee the transient bus voltage performance of the original system.Additionally,the high-performance control design is robust,flexible,and reliable.Switch-level simulations under both normal and fault operating conditions demonstrate the effectiveness of the proposed algorithm.
基金supported by Ministry of Science&Technology under National Key R&D Program of China(No.2021YFE0108600)Ningbo Science and Technology Bureau under S&T Innovation 2025 Major Special Program(No.2019B10071)Key International Cooperation of National Natural Science Foundation of China(No.51920105011)。
文摘Electrifying the on-board subsystems of aircraft becomes an inevitable process as being faced with the environmental pollution,along with the proposed concept called more electric aircraft(MEA).With the increasing number of on-board power electronic based devices,the distribution system of the aircraft can be regarded as an onboard microgrid.As it is known that the load power electronic converters can exhibit constant power load(CPL)characteristics and reduce the system stability,it is necessary to accurately predict and enhance the system stability in designing process.This paper firstly analyzes the stability of an on-board DC microgrid with the presence of CPL.Then,discusses the reasons behind instability and proposes a control strategy to enhance system stability.Finally,the simulation results are worked out to validate the analysis and the effect of the proposed control strategy.
基金supported by VILLUM FONDEN,Denmark under the VILLUM Investigator Grant(No.25920):Center for Research on Microgrids(CROM)。
文摘In light of the growing integration of renewable energy sources in power systems,the adoption of DC microgrids has become increasingly popular,due to its simple structure,having no frequency,power factor concerns.However,the dependence of DC microgrids on cyber-networks also makes them susceptible to cyber-attacks.Potential cyberattacks can disrupt power system facilities and result in significant economic and loss of life.To address this concern,this paper presents an attack-resilient control strategy for microgrids to ensure voltage regulation and power sharing with stable operation under cyber-attack on the actuators.This paper first formulates the cyber-security problem considering a distributed generation based microgrid using the converter model,after which an attack-resilient control is proposed to eliminate the actuator attack impact on the system.Steady state analysis and root locus validation illustrate the feasibility of the proposed method.The effectiveness of the proposed control scheme is demonstrated through simulation results.
基金supported by National Natural Science Foundation of China(No.51767015)Key Project of Natural Science Foundation of Gansu Province(No.22JR5RA317)Tianyou Innovation Team Support Program of Lanzhou Jiaotong University(No.TY202009)。
文摘The DC microgrid has the advantages of high energy conversion efficiency,high energy transmission density,no reactive power flow,and grid-connected synchronization.It is an essential component of the future intelligent power distribution system.Constant power load(CPL)will degrade the stability of the DC microgrid and cause system voltage oscillation due to its negative resistance characteristics.As a result,the stability of DC microgrids with CPL has become a problem.At present,the research on the stability of DC microgrid is mainly focused on unipolar DC microgrid,while the research on bipolar DC microgrid lacks systematic discussion.The stability of DC microgrid using CPL was studied first,and then the current stability criteria of DC microgrid were summarized,and its research trend was analyzed.On this basis,aiming at the stability problem caused by CPL,the existing control methods were summarized from the perspective of source converter output impedance and load converter input impedance,and the current control methods were outlined as active and passive control methods.Lastly,the research path of bipolar DC microgrid stability with CPL was prospected.
基金supported in part by the National Natural Science Foundation of China(62173255, 62188101)Shenzhen Key Laboratory of Control Theory and Intelligent Systems,(ZDSYS20220330161800001)。
文摘DC-DC converter-based multi-bus DC microgrids(MGs) in series have received much attention, where the conflict between voltage recovery and current balancing has been a hot topic. The lack of models that accurately portray the electrical characteristics of actual MGs while is controller design-friendly has kept the issue active. To this end, this paper establishes a large-signal model containing the comprehensive dynamical behavior of the DC MGs based on the theory of high-order fully actuated systems, and proposes distributed optimal control based on this. The proposed secondary control method can achieve the two goals of voltage recovery and current sharing for multi-bus DC MGs. Additionally, the simple structure of the proposed approach is similar to one based on droop control, which allows this control technique to be easily implemented in a variety of modern microgrids with different configurations. In contrast to existing studies, the process of controller design in this paper is closely tied to the actual dynamics of the MGs. It is a prominent feature that enables engineers to customize the performance metrics of the system. In addition, the analysis of the stability of the closed-loop DC microgrid system, as well as the optimality and consensus of current sharing are given. Finally, a scaled-down solar and battery-based microgrid prototype with maximum power point tracking controller is developed in the laboratory to experimentally test the efficacy of the proposed control method.
基金National Natural Science Foundation of China(Nos.51767017,51867015,62063016)Fundamental Research Innovation Group Project of Gansu Province(18JR3RA133)Gansu Provincial Science and Technology Program(20JR5RA048,20JR10RA177).
文摘During the operation of a DC microgrid,the nonlinearity and low damping characteristics of the DC bus make it prone to oscillatory instability.In this paper,we first establish a discrete nonlinear system dynamic model of a DC microgrid,study the effects of the converter sag coefficient,input voltage,and load resistance on the microgrid stability,and reveal the oscillation mechanism of a DC microgrid caused by a single source.Then,a DC microgrid stability analysis method based on the combination of bifurcation and strobe is used to analyze how the aforementioned parameters influence the oscillation characteristics of the system.Finally,the stability region of the system is obtained by the Jacobi matrix eigenvalue method.Grid simulation verifies the feasibility and effectiveness of the proposed method.
基金supported by the NationalNatural Science Foundation of China(No.52067013)the Natural Science Foundation of Gansu Province(No.20JR5RA395)as well as the Tianyou Innovation Team of Lanzhou Jiaotong University(TY202010).
文摘In this paper,an improved sag control strategy based on automatic SOC equalization is proposed to solve the problems of slow SOC equalization and excessive bus voltage fluctuation amplitude and offset caused by load and PV power variations in a stand-alone DC microgrid.The strategy includes primary and secondary control.Among them,the primary control suppresses the DC microgrid voltage fluctuation through the I and II section control,and the secondary control aims to correct the P-U curve of the energy storage system and the PV system,thus reducing the steady-state bus voltage excursion.The simulation results demonstrate that the proposed control strategy effectively achieves SOC balancing and enhances the immunity of bus voltage.The proposed strategy improves the voltage fluctuation suppression ability by approximately 39.4%and 43.1%under the PV power and load power fluctuation conditions,respectively.Furthermore,the steady-state deviation of the bus voltage,△U_(dc) is only 0.01–0.1 V,ensuring stable operation of the DC microgrid in fluctuating power environments.
文摘This paper presents performance analysis on hybrid AC/DC microgrid networks for residential home cluster. The design of the proposed microgrid includes comprehensive types of Distributed Generators (DGs) as hybrid power sources (wind, Photovoltaic (PV) solar cell, battery, fuel cell). Details about each DG dynamic modeling are presented and discussed. The customers in home cluster can be connected in both of the operating modes: islanded to the microgrid or connected to utility grid. Each DG has appended control system with its modeling that will be discussed to control DG performance. The wind turbine will be controlled by AC control system within three sub-control systems: 1) speed regulator and pitch control, 2) rotor side converter control, and 3) grid side converter control. The AC control structure is based on PLL, current regulator and voltage booster converter with using of photovoltaic Voltage Source Converter (VSC) and inverters to connect to the grid. The DC control system is mainly based on Maximum Power Point Tracking (MPPT) controller and boost converter connected to the PV array block and in order to control the system. The case study is used to analyze the performance of the proposed microgrid. The buses voltages, active power and reactive power responses are presented in both of grid-connected and islanded modes. In addition, the power factor, Total Harmonic Distortion (THD) and modulation index are calculated.
基金supported in part by the National Natural Science Foundation of China(20221017-10,62573258,62188101)the National Natural Science Foundation of Shandong Province(ZR2024 JQ018,ZR2022MF227).
文摘The dynamic average consensus(DAC)algorithm is to enable a group of networked agents to track the average of their time-varying reference signals.For most existing DAC algorithms,a necessary assumption is that the upper bounds of the reference signals and their derivatives are known in advance,thereby posing significant challenges in practical scenarios.Introducing adaptive gains in DAC algorithms provides a remedy by relaxing this assumption.However,the current adaptive gains used in this type of DAC algorithms are non-decreasing and may increase to infinity if persist disturbance exists.In order to overcome this defect,this paper presents a novel DAC algorithm with modified adaptive gains.This approach obviates the necessity for prior knowledge concerning the upper bounds of the reference signals and their derivatives.Moreover,the adaptive gains are able to remain bounded even in the presence of external disturbances.Furthermore,the proposed adaptive DAC algorithm is employed to address the distributed secondary control problem of DC microgrids.Comparative case studies are provided to verify the superiority of the proposed DAC algorithm.
基金supported in part by Fundamental Research Funds for the Central Universities,Northwestern Polytechnical University,and in part by Xianyang Key R&D Program(No.L2023-Z DYF-QYCX-012)。
文摘In this paper,a set of distributed secondary controllers is introduced that provide active regulation for both steady-state and transient-state performances of an islanded DC microgrid(MG).The secondary control for distributed converter interfaced generation(DCIG)not only guarantees that the system converges to the desired operating states in the steady state but also regulates the state variations to a prescribed transient-state performance.Compared with state-of-the-art techniques of distributed secondary control,this paper achieves accurate steady-state secondary regulations with prescribed transient-state performance in an islanded DC MG.Moreover,the applicability of the proposed control does not rely on any explicit knowledge of the system topology or physical parameters.Detailed controller designs are provided,and the system under control is proved to be Lyapunov stable using large-signal stability analysis.The steady-state and transient-state performances of the system are analyzed.The paper proves that as the perturbed system converges,the proposed control achieves accurate proportional power sharing and average voltage regulation among the DCIGs,and the transient variations of the operating voltages and power outputs at each DCIG are regulated to the prescribed transient-state performance.The effectiveness of the proposed control is validated via a four-DCIG MG system.
基金supported by Provincial Key Laboratory Performance Subsidy Project(22567612H).
文摘To achieve global voltage regulation and current sharing with reduced communication demands while enhancing the transient voltage performance of DC microgrid(MG)clusters,this paper proposes a distributed cooperative control method featuring output constraints and a dynamic event-triggered average consensus algorithm.The proposed control strategy employs an integrated primary-secondary control structure,where a dynamic event-triggered robust average consensus algorithm(DET-RACA)-based average voltage observer is designed to estimate the average voltage of each distributed generator(DG)within the MG.This estimated average voltage is subsequently utilized to simultaneously achieve voltage regulation and precise current sharing within individual MGs.Furthermore,an outputconstrained voltage controller incorporating a barrier Lyapunov function is developed to ensure high-performance transient voltage regulation for each DG.At the tertiary control level,a DET-RACA-based current observer is implemented to acquire global current information across the MG cluster,enabling the adjustment of bus reference voltages for each MG and guaranteeing global current sharing.The distinctive feature of DETRACA lies in its event-triggering mechanism,which significantly reduces communication frequency across the network topology and effectively alleviates the communication burden of the MG cluster system.Comprehensive simulations under five different operating conditions demonstrate the effectiveness and feasibility of the proposed method for DC MG cluster control.
基金supported by the National Key Research and Development Program of China(2022YFE0101900)the National Natural Science Foundation of China(52107214)the Provincial Key Research and Development Program of Inner Mongolia(2021D0026).
文摘This paper proposes an active islanding method based on impedance measurement for DC microgrids with multiple distributed generators(DGs).In the various presented methods,impedance-based islanding detection faces challenges in DC microgrids with multiple DGs due to the randomness of renewable energy.In the proposed method,the virtual impedance controls are designed to reshape the output impedance of DGs and the input impedance of loads at the detection frequency to ensure a clear distinction between grid-connected conditions and islanding conditions.Thus,the islanding events can be effectively detected under conditions that lead to a distinct decrease in system impedance.In this way,the accuracy of islanding detection is improved.Moreover,a dynamic allocation of the role algorithm is proposed to organize the orderly disturbance injection of DGs without communication,avoiding disturbance dilution.In addition,the selection principle of the frequency of disturbance current is proposed by studying the sensitivity of the point of common coupling(PCC)voltage to the disturbance.As a result,the negative influence of multiple DGs,loads,and disturbance dilution can be avoided compared to the existing methods.Finally,the effectiveness of the proposed method has been verified by both simulation and experimental results.
基金supported by National Key Research and Development Plan of China(2018YFB1503001).
文摘An adaptive droop control strategy is proposed for a parallel distributed multi-energy storage system of an isolated DC microgrid with unmatched line impedance and abnormal communication.System line impedance mismatch can cause unbalanced load power distribution and reduce service life of distributed energy storage unit(DESU).Therefore,an improved droop control based on mixed coefficient compensation of state of charge(SOC)and voltage is designed,which can adaptively adjust a power characteristic curve according to the sampling period,so as to ensure precise distribution of load power while minimizing voltage deviation.Considering the stability of the system under communication anomaly,a non-communication backup control based on Metropolis acceptance criterion is proposed,which only uses internal data to adaptively adjust the droop coefficient.In addition,a gradual smooth handover strategy is designed through gradient coefficient to optimize control stability under communication anomaly.Finally,effectiveness and correctness of the proposed control strategy are verified by mathematical analysis and RTDS/DSP hardware-in-the-loop experiments.
基金supported by the National Natural Sci-ence Foundation(NNSF)of China(No.62103443)Hunan Natural Science Foundation(No.2022JJ40630).
文摘Hybrid energy storage system(HESS)is an effective solution to address power imbalance problems caused by variability of renewable energy resources and load fluctuations in DC microgrids.The goal of HESS is to efficiently utilize different types of energy storage systems,each with its unique characteristics.Normally,the energy management of HESS relies on centralized control methods,which have limitations in flexibility,scalability,and reliability.This paper proposes an innovative artifi-cial neural network(ANN)based model predictive control(MPC)method,integrated with a decentralized pow-er-sharing strategy for HESS.In the proposed technique,MPC is employed as an expert to provide data to train the ANN.Once the ANN is finely tuned,it is directly utilized to control the DC-DC converters,eliminating the need for the extensive computations typically required by conven-tional MPC.In the proposed control scheme,virtual re-sistance droop control for fuel cell(FC)and virtual ca-pacitance droop control for battery are designed in a decentralized manner to achieve power-sharing,enhance lifespan,and ensure HESS stability.As a result,the FC is able to support steady state loads,while the battery han-dles rapid load variations.Simulation results using Matlab/Simulink demonstrate the effective performance of the proposed controller under different loads and input variations,showcasing improved performance compared to conventional MPC.
文摘Renewable energy sources have developed rapidly in recent years.In particular,isolated direct current(DC)microgrids have emerged as new grid structures for the comprehensive utilization of renewable energy and have good development prospects in industrial fields.However,the stability analysis of isolated DC microgrids still faces a significant challenge owing to the strong coupling of power converters and abundant transient processes.Thus,a new stability analysis framework for isolated DC microgrids is provided.In detail,the multi-timescale characteristics and stability issues of isolated DC microgrids are first analyzed,and three timescales are defined:the switching period timescale,device control timescale,and system control timescale.Subsequently,the existing stability indices of the microgrids are introduced,and a stability analysis framework for isolated DC microgrids is proposed based on the three defined timescales in this study.Finally,future research directions for the stability of isolated DC microgrids are discussed,and conclusions are drawn.The proposed stability analysis framework provides a reference for solving the stability problems in isolated DC microgrids,such as wide-frequency-band oscillations and the offset of the AC frequency.
