This work introduces an observer structure and highlights its distinct advantages in fault detection and isolation. Its application to the issue of shorted turns detection in synchronous generators is demonstrated. Fo...This work introduces an observer structure and highlights its distinct advantages in fault detection and isolation. Its application to the issue of shorted turns detection in synchronous generators is demonstrated. For the theoretical foundation, the convergence and design of Luenberger-type observers for disturbed linear time-invariant （LTI） single-input single-output （SISO） systems are reviewed with a particular focus on input and output disturbances. As an additional result, a simple observer design for stationary output disturbances that avoids a system order extension, as in classical results, is proposed.展开更多
Based on Hamiltonian formulation, this paper proposes a design approach to nonlinear feedback excitation control of synchronous generators with steam valve control, disturbances and unknown parameters. It is shown tha...Based on Hamiltonian formulation, this paper proposes a design approach to nonlinear feedback excitation control of synchronous generators with steam valve control, disturbances and unknown parameters. It is shown that the dynamics of the synchronous generators can be expressed as a dissipative Hamiltonian system, based on which an adaptive H-infinity controller is then designed for the systems by using the structure properties of dissipative Hamiltonian systems. Simulations show that the controller obtained in this paper is very effective.展开更多
The damage of extreme disasters to a power grid is becoming increasingly severe,and energy storage control technology is emerging as a measure to enhance grid resilience.In this study,a novel adaptive inertia control ...The damage of extreme disasters to a power grid is becoming increasingly severe,and energy storage control technology is emerging as a measure to enhance grid resilience.In this study,a novel adaptive inertia control for virtual synchronous generators is proposed for the control of wind-solar-storage combined power generation systems to form the ability for long-term power supply for load.This technology can not only provide inertia for the system but also dynamically adjust inertia according to frequency variation caused by power disturbance,avoiding rapid rise and drop of frequency in the transient process and increasing damping of a wind-solar-storage combined power generation system when the main network fails.Through low pass filtering of the sampled signal and design of the inertia control law,frequent inertia adjustment caused by measurement noise and random small fluctuation of wind speed can be avoided,and the inertia adjustment amount would not exceed the limit under any large power disturbance.The inertial boundary of the system is discussed according to the primary energy storage capacity and the tolerant power of the inverter.Convergence of a novel adaptive control algorithm is proved.Finally,a simulation model is built on PSCAD/EMTDC platform,and the effectiveness of the proposed control strategy is verified.展开更多
The virtual synchronous generator(VSG),utilized as a control strategy for grid-forming inverters,is an effective method of providing inertia and voltage support to the grid.However,the VSG exhibits limited capabilitie...The virtual synchronous generator(VSG),utilized as a control strategy for grid-forming inverters,is an effective method of providing inertia and voltage support to the grid.However,the VSG exhibits limited capabilities in low-voltage ride-through(LVRT)mode.Specifically,the slow response of the power loop poses challenges for VSG in grid voltage support and increases the risk of overcurrent,potentially violating present grid codes.This paper reveals the mechanism behind the delayed response speed of VSG control during the grid faults.On this basis,a compound compensation control strategy is proposed for improving the LVRT capability of the VSG,which incorporates adaptive frequency feedforward compensation(AFFC),direct power angle compensation(DPAC),internal potential compensation(IPC),and transient virtual impedance(TVI),effectively expediting the response speed and reducing transient current.Furthermore,the proposed control strategy ensures that the VSG operates smoothly back to its normal control state following the restoration from the grid faults.Subsequently,a large-signal model is developed to facilitate parameter design and stability analysis,which incorporates grid codes and TVI.Finally,the small-signal stability analysis and simulation and experimental results prove the correctness of the theoretical analysis and the effectiveness of the proposed control strategy.展开更多
The integration of converter-interfaced generators(CIGs)into power systems is rapidly replacing traditional synchronous machines.To ensure the security of power supply,modern power systems require the application of g...The integration of converter-interfaced generators(CIGs)into power systems is rapidly replacing traditional synchronous machines.To ensure the security of power supply,modern power systems require the application of grid-forming technologies.This study presents a systematic small-signal analysis procedure to assess the synchronization stability of gridforming virtual synchronous generators(VSGs)considering the power system characteristics.Specifically,this procedure offers guidance in tuning controller gains to enhance stability.It is applied to six different grid-forming VSGs and experimentally tested to validate the theoretical analysis.This study concludes with key findings and a discussion on the suitability of the analyzed grid-forming VSGs based on the power system characteristics.展开更多
A modified four-dimensional linear active disturbance rejection control(LADRC)strategy is proposed for a dual three-phase permanent magnet synchronous generator(DTP-PMSG)system to reduce cross-coupling between the d a...A modified four-dimensional linear active disturbance rejection control(LADRC)strategy is proposed for a dual three-phase permanent magnet synchronous generator(DTP-PMSG)system to reduce cross-coupling between the d and q axis currents in the d-q subspace and harmonic currents in the x-y subspace.In the d-q subspace,the proposed strategy uses a model-based LADRC to enhance the decoupling effect between the d and q axes and the disturbance rejection ability against parameter variation.In the x-y subspace,the 5th and 7th harmonic current suppression abilities are improved by using quasi-resonant units parallel to the extended state observer of the traditional LADRC.The proposed modified LADRC strategy improved both the steady-state performance and dynamic response of the DTP-PMSG system.The experimental results demonstrate that the proposed strategy is both feasible and effective.展开更多
In recent years, with the growth of wind energy resources,the capability of wind farms to damp low-frequency oscillations(LFOs) has provided a notable advantage for the stabilityenhancement of the modern power grid. M...In recent years, with the growth of wind energy resources,the capability of wind farms to damp low-frequency oscillations(LFOs) has provided a notable advantage for the stabilityenhancement of the modern power grid. Meanwhile, owingto variations in the power system operating point (OP), thedamping characteristics of LFOs may be affected adversely. Inthis respect, this paper presents a coordinated robust proportional-integral-derivative (PID) based damping control approachfor permanent magnet synchronous generators (PMSGs)to effectively stabilize LFOs, while considering power system operationaluncertainties in the form of a polytopic model constructedby linearizing the power system under a given set ofOPs. The proposed approach works by modulating the DC-linkvoltage control loop of the grid-side converter (GSC) via a supplementaryPID controller, which is synthesized by transformingthe design problem into H-infinity static output feedback(SOF) control methodology. The solution of H-infinity SOF controlproblem involves satisfying linear matrix inequality (LMI)constraints based on the parameter-dependent Lyapunov functionto ensure asymptotic stability such that the minimal H-infinityperformance objective is simultaneously accomplished forthe entire polytope. The coordinated damping controllers forthe multiple wind farms are then designed sequentially by usingthe proposed approach. Eigenvalue analysis confirms the improveddamping characteristics of the closed-loop system forseveral representative OPs. Afterward, the simulation results, includingthe performance comparison with existing approaches,validate the higher robustness of the proposed approach for awide range of operating scenarios.展开更多
This paper introduces a novel chattering-free terminal sliding mode control(SMC)strategy to address chaotic behavior in permanent magnet synchronous generators(PMSG)for offshore wind turbine systems.By integrating an ...This paper introduces a novel chattering-free terminal sliding mode control(SMC)strategy to address chaotic behavior in permanent magnet synchronous generators(PMSG)for offshore wind turbine systems.By integrating an adaptive exponential reaching law with a continuous barrier function,the proposed approach eliminates chattering and ensures robust performance under model uncertainties.The methodology combines adaptive SMC with dynamic switching to estimate and compensates for unknown uncertainties,providing smooth and stable control.Finally,the performance and effectiveness of the proposed approach are compared with those of a previous study.展开更多
By simulating the operating dynamics of synchronous generators(SGs),the use of virtual synchronous gen-rators(VSGs)can help overcome inverter-based generators'shortcomings of low inertia and minimal damping for gr...By simulating the operating dynamics of synchronous generators(SGs),the use of virtual synchronous gen-rators(VSGs)can help overcome inverter-based generators'shortcomings of low inertia and minimal damping for gridforming applications.VSGs'stability are very important for their solar and wind electricity applications.Currently,the related research primarily focuses on VSGs and their applications for microgrids.There has been little research to explore how VSGs effect low frequency oscillations in power transmission systems.This paper describes a small-signal model of a VSGSG interconnected system,which is suitable for studying low frequency oscillation damping in a power transmission grid.Based on this model,the effects of VSGs on low frequency oscillations are compared with the effects of SGs to reveal the mechanism of how VSGs infuence damping characteristics.The influence of each VSG control loop on oscillations is also analyzed in this paper.Then,the low frequency oscillation risks with different types of VSGs are described.Finally,experiments on a real-time laboratory(RT-LAB)platform are conducted to verify the small-signal analysis results.展开更多
The grid-forming virtual synchronous generator(GFVSG)not only employs a first-order low-pass filter for virtual inertia control but also introduces grid-connected active power(GCAP)dynamic oscillation issues,akin to t...The grid-forming virtual synchronous generator(GFVSG)not only employs a first-order low-pass filter for virtual inertia control but also introduces grid-connected active power(GCAP)dynamic oscillation issues,akin to those observed in traditional synchronous generators.In response to this,an improved strategy for lead-lag filter based GFVSG(LLF-GFVSG)is presented in this article.Firstly,the grid-connected circuit structure and control principle of typical GFVSG are described,and a closed-loop small-signal model for GCAP in GFVSG is established.The causes of GCAP dynamic oscillation of GFVSG under the disturbances of active power command as well as grid frequency are analyzed.On this basis,the LLF-GFVSG improvement strategy and its parameter design method are given.Finally,the efficiency of the proposed control strategy in damping GCAP dynamic oscillations under various disturbances is verified using MATLAB simulations and experimental comparison results.展开更多
In order to reduce the cogging torque, this paper investigates the influence of some parameters on the cogging torque developed by directly driven permanent magnet synchronous wind generators. Based on the remanent ma...In order to reduce the cogging torque, this paper investigates the influence of some parameters on the cogging torque developed by directly driven permanent magnet synchronous wind generators. Based on the remanent magnetic flux densities, the cogging torque is computed by using finite element method. It is shown that many parameters have influence on cogging torque and the slot and pole number combination has a significant effect on cogging torque. A simple factor has been introduced to indicate the effect of the slot and pole number combination. Some practical experience to reduce the cogging torque was applied to 2 MW three phase permanent magnet synchronous generator at rated speed of 37.5 rpm for wind energy conversion. The simulation and experiment results verify the effect of the proposed method.展开更多
Virtual synchronous generators(VSGs)are widely introduced to the renewable power generation,the variablespeed pumped storage units,and so on,as a promising gridforming solution.It is noted that VSGs can provide virtua...Virtual synchronous generators(VSGs)are widely introduced to the renewable power generation,the variablespeed pumped storage units,and so on,as a promising gridforming solution.It is noted that VSGs can provide virtual inertia for frequency support,but the larger inertia would worsen the synchronization stability,referring to keeping synchronization with the grid during voltage dips.Thus,this paper presents a transient damping method of VSGs for enhancing the synchronization stability during voltage dips.It is revealed that the loss of synchronization(LOS)of VSGs always accompanies with the positive frequency deviation and the damping is the key factor to remove LOS when the equilibrium point exists.In order to enhance synchronization stability during voltage dips,the transient damping is proposed,which is generated by the frequency deviation in active power loop.Additionally,the proposed method can realize seamless switching between normal state and grid fault.Moreover,detailed control design for transient damping gain is given to ensure the synchronization stability under different inertia requirements during voltage dips.Finally,the experimental results are presented to validate the analysis and the effectiveness of the improved transient damping method.展开更多
In the DC microgrid,the lack of inertia and damping in power electronic converters results in poor stability of DC bus voltage and low inertia of the DC microgrid during fluctuations in load and photovoltaic power.To ...In the DC microgrid,the lack of inertia and damping in power electronic converters results in poor stability of DC bus voltage and low inertia of the DC microgrid during fluctuations in load and photovoltaic power.To address this issue,the application of a virtual synchronous generator(VSG)in grid-connected inverters control is referenced and proposes a control strategy called the analogous virtual synchronous generator(AVSG)control strategy for the interface DC/DC converter of the battery in the microgrid.Besides,a flexible parameter adaptive control method is introduced to further enhance the inertial behavior of the AVSG control.Firstly,a theoretical analysis is conducted on the various components of the DC microgrid,the structure of analogous virtual synchronous generator,and the control structure’s main parameters related to the DC microgrid’s inertial behavior.Secondly,the voltage change rate tracking coefficient is introduced to adjust the change of the virtual capacitance and damping coefficient flexibility,which further strengthens the inertia trend of the DC microgrid.Additionally,a small-signal modeling approach is used to analyze the approximate range of the AVSG’s main parameters ensuring system stability.Finally,conduct a simulation analysis by building the model of the DC microgrid system with photovoltaic(PV)and battery energy storage(BES)in MATLAB/Simulink.Simulation results from different scenarios have verified that the AVSG control introduces fixed inertia and damping into the droop control of the battery,resulting in a certain level of inertia enhancement.Furthermore,the additional adaptive control strategy built upon the AVSG control provides better and flexible inertial support for the DC microgrid,further enhances the stability of the DC bus voltage,and has a more positive impact on the battery performance.展开更多
The information of the field current is essential for the brushless synchronous starter/generator system,which determines the performance and health status of this system.However,since the field winding of the main ma...The information of the field current is essential for the brushless synchronous starter/generator system,which determines the performance and health status of this system.However,since the field winding of the main machine is installed in the rotor part,the measurement of the field current in this brushless system seem impossible.Considering that,the field current might be affected by the rectifier mode,the field current estimation method in different rectifier mode is studied in this paper.The main exciter(ME)rotor currents were restructured based on the ME flux equations.With these restructured rotor currents,the field current in different rectifier commutation mode is analyzed,then the field current estimation method considering the rectifier mode can be obtained.The experiments in different rectifier modes are carried out to verify the proposed method.展开更多
With the application of distributed power sources,the stability of the power system has been dramatically affected.Therefore,scholars have proposed the concept of a virtual synchronous generator(VSG).However,after the...With the application of distributed power sources,the stability of the power system has been dramatically affected.Therefore,scholars have proposed the concept of a virtual synchronous generator(VSG).However,after the system is disturbed,how to make it respond quickly and effectively to maintain the stability of the system becomes a complex problem.To address this problem,a frequency prediction component is incorporated into the control module of the VSG to enhance its performance.The Convolutional Neural NetworkLong Short-Term Memory(CNN-LSTM)model is used for frequency prediction,ensuring that the maximum energy capacity released by the storage system is maintained.Additionally,it guarantees that the inverter's output power does not exceed its rated capacity,based on the predicted frequency limit after the system experiences a disturbance.The advantage of real-time adjustment of inverter parameters is that the setting intervals for inertia and damping can be increased.The selection criteria for inertia and damping can be derived from the power angle oscillation curve of the synchronous generator.Consequently,an adaptive control strategy for VSG parameters is implemented to enhance the system's frequency restoration following disturbances.The validity and effectiveness of the model are verified through simulations in Matlab/Simulink.展开更多
In China, regions with abundant wind energy resources are generally located at the end of power grids. The power grid architecture in these regions is typically not sufficiently strong, and the energy structure is rel...In China, regions with abundant wind energy resources are generally located at the end of power grids. The power grid architecture in these regions is typically not sufficiently strong, and the energy structure is relatively simple. Thus, connecting large-capacity wind power units complicates the peak load regulation and stable operation of the power grids in these regions. Most wind turbines use power electronic converter technology, which affects the safety and stability of the power grid differently compared with conventional synchronous generators. Furthermore, fluctuations in wind power cause fluctuations in the output of wind farms, making it difficult to create and implement suitable power generation plans for wind farms. The generation technology and grid connection scheme for wind power and conventional thermal power generation differ considerably. Moreover, the active and reactive power control abilities of wind turbines are weaker than those of thermal power units, necessitating additional equipment to control wind turbines. Hence, to address the aforementioned issues with large-scale wind power generation, this study analyzes the differences between the grid connection and collection strategies for wind power bases and thermal power plants. Based on this analysis, the differences in the power control modes of wind power and thermal power are further investigated. Finally, the stability of different control modes is analyzed through simulation. The findings can be beneficial for the planning and development of large-scale wind power generation farms.展开更多
As the penetration rate of distributed energy increases,the transient power angle stability problem of the virtual synchronous generator(VSG)has gradually become prominent.In view of the situation that the grid impeda...As the penetration rate of distributed energy increases,the transient power angle stability problem of the virtual synchronous generator(VSG)has gradually become prominent.In view of the situation that the grid impedance ratio(R/X)is high and affects the transient power angle stability of VSG,this paper proposes a VSG transient power angle stability control strategy based on the combination of frequency difference feedback and virtual impedance.To improve the transient power angle stability of the VSG,a virtual impedance is adopted in the voltage loop to adjust the impedance ratio R/X;and the PI control feedback of the VSG frequency difference is introduced in the reactive powervoltage link of theVSGto enhance the damping effect.Thesecond-orderVSGdynamic nonlinearmodel considering the reactive power-voltage loop is established and the influence of different proportional integral(PI)control parameters on the system balance stability is analyzed.Moreover,the impact of the impedance ratio R/X on the transient power angle stability is presented using the equal area criterion.In the simulations,during the voltage dips with the reduction of R/X from 1.6 to 0.8,Δδ_(1)is reduced from 0.194 rad to 0.072 rad,Δf_(1)is reduced from 0.170 to 0.093 Hz,which shows better transient power angle stability.Simulation results verify that compared with traditional VSG,the proposedmethod can effectively improve the transient power angle stability of the system.展开更多
Wide-band oscillations have become a significant issue limiting the development of wind power.Both large-signal and small-signal analyses require extensive model derivation.Moreover,the large number and high order of ...Wide-band oscillations have become a significant issue limiting the development of wind power.Both large-signal and small-signal analyses require extensive model derivation.Moreover,the large number and high order of wind turbines have driven the development of simplified models,whose applicability remains controversial.In this paper,a wide-band oscillation analysis method based on the average-value model(AVM)is proposed for wind farms(WFs).A novel linearization analysis framework is developed,leveraging the continuous-time characteristics of the AVM and MATLAB/Simulink’s built-in linearization tools.This significantly reduces modeling complexity and computational costs while maintaining model fidelity.Additionally,an object-based initial value estimation method of state variables is introduced,which,when combined with steady-state point-solving tools,greatly reduces the computational effort required for equilibrium point solving in batch linearization analysis.The proposed method is validated in both doubly fed induction generator(DFIG)-based and permanent magnet synchronous generator(PMSG)-based WFs.Furthermore,a comprehensive analysis is conducted for the first time to examine the impact of the machine-side system on the system stability of the nonfully controlled PMSG-based WF.展开更多
The rapid development of new energy power generation technology and the transformation of power electronics in the core equipment of source-grid-load drives the power system towards the“double-high”development patte...The rapid development of new energy power generation technology and the transformation of power electronics in the core equipment of source-grid-load drives the power system towards the“double-high”development pattern of“high proportion of renewable energy”and“high proportion of power electronic equipment”.To enhance the transient performance of AC/DC hybrid microgrid(HMG)in the context of“double-high,”aπtype virtual synchronous generator(π-VSG)control strategy is applied to bidirectional interface converter(BIC)to address the issues of lacking inertia and poor disturbance immunity caused by the high penetration rate of power electronic equipment and new energy.Firstly,the virtual synchronous generator mechanical motion equations and virtual capacitance equations are used to introduce the virtual inertia control equations that consider the transient performance of HMG;based on the equations,theπ-type equivalent control model of the BIC is established.Next,the inertia power is actively transferred through the BIC according to the load fluctuation to compensate for the system’s inertia deficit.Secondly,theπ-VSG control utilizes small-signal analysis to investigate howthe fundamental parameters affect the overall stability of the HMG and incorporates power step response curves to reveal the relationship between the control’s virtual parameters and transient performance.Finally,the PSCAD/EMTDC simulation results show that theπ-VSG control effectively improves the immunity of AC frequency and DC voltage in the HMG system under the load fluctuation condition,increases the stability of the HMG system and satisfies the power-sharing control objective between the AC and DC subgrids.展开更多
This paper addresses some of the problems related to direct surface temperature measurement of a salient pole synchronous generator excitation winding in rotation. Excitation winding temperature is used for determinin...This paper addresses some of the problems related to direct surface temperature measurement of a salient pole synchronous generator excitation winding in rotation. Excitation winding temperature is used for determining the dynamic limit in a PQ diagram. The paper also addresses procedures of improving the accuracy of surface temperature measurement using the contact DS 18B20 digital temperature probes. The paper also provides experimental results of direct temperature measurement of the excitation winding surface conducted in the salient pole synchronous generator in the rotation.展开更多
文摘This work introduces an observer structure and highlights its distinct advantages in fault detection and isolation. Its application to the issue of shorted turns detection in synchronous generators is demonstrated. For the theoretical foundation, the convergence and design of Luenberger-type observers for disturbed linear time-invariant （LTI） single-input single-output （SISO） systems are reviewed with a particular focus on input and output disturbances. As an additional result, a simple observer design for stationary output disturbances that avoids a system order extension, as in classical results, is proposed.
基金This work was supported by the National Natural Science Foundation of China (No.G60474001) the Research Fund for Doctoral Program of Chinese Higher Education (No.G20040422059).
文摘Based on Hamiltonian formulation, this paper proposes a design approach to nonlinear feedback excitation control of synchronous generators with steam valve control, disturbances and unknown parameters. It is shown that the dynamics of the synchronous generators can be expressed as a dissipative Hamiltonian system, based on which an adaptive H-infinity controller is then designed for the systems by using the structure properties of dissipative Hamiltonian systems. Simulations show that the controller obtained in this paper is very effective.
基金supported by National Natural Science Foundation of China(51777069)Science and Technology Program of China Southern Power Grid Company(037700KK52190010(GDKJXM20198272)).
文摘The damage of extreme disasters to a power grid is becoming increasingly severe,and energy storage control technology is emerging as a measure to enhance grid resilience.In this study,a novel adaptive inertia control for virtual synchronous generators is proposed for the control of wind-solar-storage combined power generation systems to form the ability for long-term power supply for load.This technology can not only provide inertia for the system but also dynamically adjust inertia according to frequency variation caused by power disturbance,avoiding rapid rise and drop of frequency in the transient process and increasing damping of a wind-solar-storage combined power generation system when the main network fails.Through low pass filtering of the sampled signal and design of the inertia control law,frequent inertia adjustment caused by measurement noise and random small fluctuation of wind speed can be avoided,and the inertia adjustment amount would not exceed the limit under any large power disturbance.The inertial boundary of the system is discussed according to the primary energy storage capacity and the tolerant power of the inverter.Convergence of a novel adaptive control algorithm is proved.Finally,a simulation model is built on PSCAD/EMTDC platform,and the effectiveness of the proposed control strategy is verified.
基金supported by the National Natural Science Foundation of China(No.62222309)the Natural Science Foundation of Shandong Province(No.ZR2022JQ29).
文摘The virtual synchronous generator(VSG),utilized as a control strategy for grid-forming inverters,is an effective method of providing inertia and voltage support to the grid.However,the VSG exhibits limited capabilities in low-voltage ride-through(LVRT)mode.Specifically,the slow response of the power loop poses challenges for VSG in grid voltage support and increases the risk of overcurrent,potentially violating present grid codes.This paper reveals the mechanism behind the delayed response speed of VSG control during the grid faults.On this basis,a compound compensation control strategy is proposed for improving the LVRT capability of the VSG,which incorporates adaptive frequency feedforward compensation(AFFC),direct power angle compensation(DPAC),internal potential compensation(IPC),and transient virtual impedance(TVI),effectively expediting the response speed and reducing transient current.Furthermore,the proposed control strategy ensures that the VSG operates smoothly back to its normal control state following the restoration from the grid faults.Subsequently,a large-signal model is developed to facilitate parameter design and stability analysis,which incorporates grid codes and TVI.Finally,the small-signal stability analysis and simulation and experimental results prove the correctness of the theoretical analysis and the effectiveness of the proposed control strategy.
基金supported by Grant PID2021-124571OB-I00 funded by MICIU/AEI/10.13039/501100011033FEDER,EU。
文摘The integration of converter-interfaced generators(CIGs)into power systems is rapidly replacing traditional synchronous machines.To ensure the security of power supply,modern power systems require the application of grid-forming technologies.This study presents a systematic small-signal analysis procedure to assess the synchronization stability of gridforming virtual synchronous generators(VSGs)considering the power system characteristics.Specifically,this procedure offers guidance in tuning controller gains to enhance stability.It is applied to six different grid-forming VSGs and experimentally tested to validate the theoretical analysis.This study concludes with key findings and a discussion on the suitability of the analyzed grid-forming VSGs based on the power system characteristics.
基金Supported by the National Science Fund for Distinguished Young Scholars under Grant 52025073 and the Zhenjiang Key Research Program under Grant GY2020011.
文摘A modified four-dimensional linear active disturbance rejection control(LADRC)strategy is proposed for a dual three-phase permanent magnet synchronous generator(DTP-PMSG)system to reduce cross-coupling between the d and q axis currents in the d-q subspace and harmonic currents in the x-y subspace.In the d-q subspace,the proposed strategy uses a model-based LADRC to enhance the decoupling effect between the d and q axes and the disturbance rejection ability against parameter variation.In the x-y subspace,the 5th and 7th harmonic current suppression abilities are improved by using quasi-resonant units parallel to the extended state observer of the traditional LADRC.The proposed modified LADRC strategy improved both the steady-state performance and dynamic response of the DTP-PMSG system.The experimental results demonstrate that the proposed strategy is both feasible and effective.
基金supported by the Major Program of National Natural Science Foundation of China(No.U2166601)the General Program of National Natural Science Foundation of China(No.52077196).
文摘In recent years, with the growth of wind energy resources,the capability of wind farms to damp low-frequency oscillations(LFOs) has provided a notable advantage for the stabilityenhancement of the modern power grid. Meanwhile, owingto variations in the power system operating point (OP), thedamping characteristics of LFOs may be affected adversely. Inthis respect, this paper presents a coordinated robust proportional-integral-derivative (PID) based damping control approachfor permanent magnet synchronous generators (PMSGs)to effectively stabilize LFOs, while considering power system operationaluncertainties in the form of a polytopic model constructedby linearizing the power system under a given set ofOPs. The proposed approach works by modulating the DC-linkvoltage control loop of the grid-side converter (GSC) via a supplementaryPID controller, which is synthesized by transformingthe design problem into H-infinity static output feedback(SOF) control methodology. The solution of H-infinity SOF controlproblem involves satisfying linear matrix inequality (LMI)constraints based on the parameter-dependent Lyapunov functionto ensure asymptotic stability such that the minimal H-infinityperformance objective is simultaneously accomplished forthe entire polytope. The coordinated damping controllers forthe multiple wind farms are then designed sequentially by usingthe proposed approach. Eigenvalue analysis confirms the improveddamping characteristics of the closed-loop system forseveral representative OPs. Afterward, the simulation results, includingthe performance comparison with existing approaches,validate the higher robustness of the proposed approach for awide range of operating scenarios.
文摘This paper introduces a novel chattering-free terminal sliding mode control(SMC)strategy to address chaotic behavior in permanent magnet synchronous generators(PMSG)for offshore wind turbine systems.By integrating an adaptive exponential reaching law with a continuous barrier function,the proposed approach eliminates chattering and ensures robust performance under model uncertainties.The methodology combines adaptive SMC with dynamic switching to estimate and compensates for unknown uncertainties,providing smooth and stable control.Finally,the performance and effectiveness of the proposed approach are compared with those of a previous study.
文摘By simulating the operating dynamics of synchronous generators(SGs),the use of virtual synchronous gen-rators(VSGs)can help overcome inverter-based generators'shortcomings of low inertia and minimal damping for gridforming applications.VSGs'stability are very important for their solar and wind electricity applications.Currently,the related research primarily focuses on VSGs and their applications for microgrids.There has been little research to explore how VSGs effect low frequency oscillations in power transmission systems.This paper describes a small-signal model of a VSGSG interconnected system,which is suitable for studying low frequency oscillation damping in a power transmission grid.Based on this model,the effects of VSGs on low frequency oscillations are compared with the effects of SGs to reveal the mechanism of how VSGs infuence damping characteristics.The influence of each VSG control loop on oscillations is also analyzed in this paper.Then,the low frequency oscillation risks with different types of VSGs are described.Finally,experiments on a real-time laboratory(RT-LAB)platform are conducted to verify the small-signal analysis results.
基金supported by the Key Laboratory of Modern Power System Simulation and Control&Renewable Energy Technology(Northeast Electric Power University)Open Fund of China under Grant MPSS2024-08.
文摘The grid-forming virtual synchronous generator(GFVSG)not only employs a first-order low-pass filter for virtual inertia control but also introduces grid-connected active power(GCAP)dynamic oscillation issues,akin to those observed in traditional synchronous generators.In response to this,an improved strategy for lead-lag filter based GFVSG(LLF-GFVSG)is presented in this article.Firstly,the grid-connected circuit structure and control principle of typical GFVSG are described,and a closed-loop small-signal model for GCAP in GFVSG is established.The causes of GCAP dynamic oscillation of GFVSG under the disturbances of active power command as well as grid frequency are analyzed.On this basis,the LLF-GFVSG improvement strategy and its parameter design method are given.Finally,the efficiency of the proposed control strategy in damping GCAP dynamic oscillations under various disturbances is verified using MATLAB simulations and experimental comparison results.
文摘In order to reduce the cogging torque, this paper investigates the influence of some parameters on the cogging torque developed by directly driven permanent magnet synchronous wind generators. Based on the remanent magnetic flux densities, the cogging torque is computed by using finite element method. It is shown that many parameters have influence on cogging torque and the slot and pole number combination has a significant effect on cogging torque. A simple factor has been introduced to indicate the effect of the slot and pole number combination. Some practical experience to reduce the cogging torque was applied to 2 MW three phase permanent magnet synchronous generator at rated speed of 37.5 rpm for wind energy conversion. The simulation and experiment results verify the effect of the proposed method.
文摘Virtual synchronous generators(VSGs)are widely introduced to the renewable power generation,the variablespeed pumped storage units,and so on,as a promising gridforming solution.It is noted that VSGs can provide virtual inertia for frequency support,but the larger inertia would worsen the synchronization stability,referring to keeping synchronization with the grid during voltage dips.Thus,this paper presents a transient damping method of VSGs for enhancing the synchronization stability during voltage dips.It is revealed that the loss of synchronization(LOS)of VSGs always accompanies with the positive frequency deviation and the damping is the key factor to remove LOS when the equilibrium point exists.In order to enhance synchronization stability during voltage dips,the transient damping is proposed,which is generated by the frequency deviation in active power loop.Additionally,the proposed method can realize seamless switching between normal state and grid fault.Moreover,detailed control design for transient damping gain is given to ensure the synchronization stability under different inertia requirements during voltage dips.Finally,the experimental results are presented to validate the analysis and the effectiveness of the improved transient damping method.
基金funded by the National Natural Science Foundation of China(52067013),and the Provincial Natural Science Foundation of Gansu(20JR5RA395).
文摘In the DC microgrid,the lack of inertia and damping in power electronic converters results in poor stability of DC bus voltage and low inertia of the DC microgrid during fluctuations in load and photovoltaic power.To address this issue,the application of a virtual synchronous generator(VSG)in grid-connected inverters control is referenced and proposes a control strategy called the analogous virtual synchronous generator(AVSG)control strategy for the interface DC/DC converter of the battery in the microgrid.Besides,a flexible parameter adaptive control method is introduced to further enhance the inertial behavior of the AVSG control.Firstly,a theoretical analysis is conducted on the various components of the DC microgrid,the structure of analogous virtual synchronous generator,and the control structure’s main parameters related to the DC microgrid’s inertial behavior.Secondly,the voltage change rate tracking coefficient is introduced to adjust the change of the virtual capacitance and damping coefficient flexibility,which further strengthens the inertia trend of the DC microgrid.Additionally,a small-signal modeling approach is used to analyze the approximate range of the AVSG’s main parameters ensuring system stability.Finally,conduct a simulation analysis by building the model of the DC microgrid system with photovoltaic(PV)and battery energy storage(BES)in MATLAB/Simulink.Simulation results from different scenarios have verified that the AVSG control introduces fixed inertia and damping into the droop control of the battery,resulting in a certain level of inertia enhancement.Furthermore,the additional adaptive control strategy built upon the AVSG control provides better and flexible inertial support for the DC microgrid,further enhances the stability of the DC bus voltage,and has a more positive impact on the battery performance.
基金supported in part by the Natural Science Foundation of Shaanxi Province under Grant 2023JCQN0534in part by the Natural Science Foundation of Shaanxi Provincial Department of Education under Grant 23JK0660in part by the Xi’an Municipal Bureau of Science and Technology under Grant 24GXF0085。
文摘The information of the field current is essential for the brushless synchronous starter/generator system,which determines the performance and health status of this system.However,since the field winding of the main machine is installed in the rotor part,the measurement of the field current in this brushless system seem impossible.Considering that,the field current might be affected by the rectifier mode,the field current estimation method in different rectifier mode is studied in this paper.The main exciter(ME)rotor currents were restructured based on the ME flux equations.With these restructured rotor currents,the field current in different rectifier commutation mode is analyzed,then the field current estimation method considering the rectifier mode can be obtained.The experiments in different rectifier modes are carried out to verify the proposed method.
文摘With the application of distributed power sources,the stability of the power system has been dramatically affected.Therefore,scholars have proposed the concept of a virtual synchronous generator(VSG).However,after the system is disturbed,how to make it respond quickly and effectively to maintain the stability of the system becomes a complex problem.To address this problem,a frequency prediction component is incorporated into the control module of the VSG to enhance its performance.The Convolutional Neural NetworkLong Short-Term Memory(CNN-LSTM)model is used for frequency prediction,ensuring that the maximum energy capacity released by the storage system is maintained.Additionally,it guarantees that the inverter's output power does not exceed its rated capacity,based on the predicted frequency limit after the system experiences a disturbance.The advantage of real-time adjustment of inverter parameters is that the setting intervals for inertia and damping can be increased.The selection criteria for inertia and damping can be derived from the power angle oscillation curve of the synchronous generator.Consequently,an adaptive control strategy for VSG parameters is implemented to enhance the system's frequency restoration following disturbances.The validity and effectiveness of the model are verified through simulations in Matlab/Simulink.
基金This work was supported by National Key Research and Development Program of China(2018YFB0904000).
文摘In China, regions with abundant wind energy resources are generally located at the end of power grids. The power grid architecture in these regions is typically not sufficiently strong, and the energy structure is relatively simple. Thus, connecting large-capacity wind power units complicates the peak load regulation and stable operation of the power grids in these regions. Most wind turbines use power electronic converter technology, which affects the safety and stability of the power grid differently compared with conventional synchronous generators. Furthermore, fluctuations in wind power cause fluctuations in the output of wind farms, making it difficult to create and implement suitable power generation plans for wind farms. The generation technology and grid connection scheme for wind power and conventional thermal power generation differ considerably. Moreover, the active and reactive power control abilities of wind turbines are weaker than those of thermal power units, necessitating additional equipment to control wind turbines. Hence, to address the aforementioned issues with large-scale wind power generation, this study analyzes the differences between the grid connection and collection strategies for wind power bases and thermal power plants. Based on this analysis, the differences in the power control modes of wind power and thermal power are further investigated. Finally, the stability of different control modes is analyzed through simulation. The findings can be beneficial for the planning and development of large-scale wind power generation farms.
基金supported by theMajor Science and Technology Projects of China Southern Power Grid(Grant number CGYKJXM20210328).
文摘As the penetration rate of distributed energy increases,the transient power angle stability problem of the virtual synchronous generator(VSG)has gradually become prominent.In view of the situation that the grid impedance ratio(R/X)is high and affects the transient power angle stability of VSG,this paper proposes a VSG transient power angle stability control strategy based on the combination of frequency difference feedback and virtual impedance.To improve the transient power angle stability of the VSG,a virtual impedance is adopted in the voltage loop to adjust the impedance ratio R/X;and the PI control feedback of the VSG frequency difference is introduced in the reactive powervoltage link of theVSGto enhance the damping effect.Thesecond-orderVSGdynamic nonlinearmodel considering the reactive power-voltage loop is established and the influence of different proportional integral(PI)control parameters on the system balance stability is analyzed.Moreover,the impact of the impedance ratio R/X on the transient power angle stability is presented using the equal area criterion.In the simulations,during the voltage dips with the reduction of R/X from 1.6 to 0.8,Δδ_(1)is reduced from 0.194 rad to 0.072 rad,Δf_(1)is reduced from 0.170 to 0.093 Hz,which shows better transient power angle stability.Simulation results verify that compared with traditional VSG,the proposedmethod can effectively improve the transient power angle stability of the system.
基金supported by the National Natural Science Foundation of China under Grant 52277072.
文摘Wide-band oscillations have become a significant issue limiting the development of wind power.Both large-signal and small-signal analyses require extensive model derivation.Moreover,the large number and high order of wind turbines have driven the development of simplified models,whose applicability remains controversial.In this paper,a wide-band oscillation analysis method based on the average-value model(AVM)is proposed for wind farms(WFs).A novel linearization analysis framework is developed,leveraging the continuous-time characteristics of the AVM and MATLAB/Simulink’s built-in linearization tools.This significantly reduces modeling complexity and computational costs while maintaining model fidelity.Additionally,an object-based initial value estimation method of state variables is introduced,which,when combined with steady-state point-solving tools,greatly reduces the computational effort required for equilibrium point solving in batch linearization analysis.The proposed method is validated in both doubly fed induction generator(DFIG)-based and permanent magnet synchronous generator(PMSG)-based WFs.Furthermore,a comprehensive analysis is conducted for the first time to examine the impact of the machine-side system on the system stability of the nonfully controlled PMSG-based WF.
基金funded by“The Fourth Phase of 2022 Advantage Discipline Engineering-Control Science and Engineering”,grant number 4013000063.
文摘The rapid development of new energy power generation technology and the transformation of power electronics in the core equipment of source-grid-load drives the power system towards the“double-high”development pattern of“high proportion of renewable energy”and“high proportion of power electronic equipment”.To enhance the transient performance of AC/DC hybrid microgrid(HMG)in the context of“double-high,”aπtype virtual synchronous generator(π-VSG)control strategy is applied to bidirectional interface converter(BIC)to address the issues of lacking inertia and poor disturbance immunity caused by the high penetration rate of power electronic equipment and new energy.Firstly,the virtual synchronous generator mechanical motion equations and virtual capacitance equations are used to introduce the virtual inertia control equations that consider the transient performance of HMG;based on the equations,theπ-type equivalent control model of the BIC is established.Next,the inertia power is actively transferred through the BIC according to the load fluctuation to compensate for the system’s inertia deficit.Secondly,theπ-VSG control utilizes small-signal analysis to investigate howthe fundamental parameters affect the overall stability of the HMG and incorporates power step response curves to reveal the relationship between the control’s virtual parameters and transient performance.Finally,the PSCAD/EMTDC simulation results show that theπ-VSG control effectively improves the immunity of AC frequency and DC voltage in the HMG system under the load fluctuation condition,increases the stability of the HMG system and satisfies the power-sharing control objective between the AC and DC subgrids.
文摘This paper addresses some of the problems related to direct surface temperature measurement of a salient pole synchronous generator excitation winding in rotation. Excitation winding temperature is used for determining the dynamic limit in a PQ diagram. The paper also addresses procedures of improving the accuracy of surface temperature measurement using the contact DS 18B20 digital temperature probes. The paper also provides experimental results of direct temperature measurement of the excitation winding surface conducted in the salient pole synchronous generator in the rotation.
