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Transient Damping of Virtual Synchronous Generator for Enhancing Synchronization Stability during Voltage Dips
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作者 Shitao Sun Yu Lei +4 位作者 Guowen Hao Yi Lu Jindong Liu Zhaoxin Song Jie Zhang 《CES Transactions on Electrical Machines and Systems》 EI CSCD 2024年第2期143-151,共9页
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
关键词 virtual synchronous generator(VSG) Transient damping synchronization stability Voltage dips
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Improved Strategy of Grid-Forming Virtual Synchronous Generator Based on Transient Damping
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作者 Lei Zhang Rongliang Shi +2 位作者 Junhui Li Yannan Yu Yu Zhang 《Energy Engineering》 EI 2024年第11期3181-3197,共17页
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
关键词 Grid-forming virtual synchronous generator first-order low-pass filter lead-lag filter small-signal model parameter design
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An Adaptive Control Strategy for Energy Storage Interface Converter Based on Analogous Virtual Synchronous Generator
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作者 Feng Zhao Jinshuo Zhang +1 位作者 Xiaoqiang Chen Ying Wang 《Energy Engineering》 EI 2024年第2期339-358,共20页
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
关键词 Adaptive control analogous virtual synchronous generator DC/DC converter inertia of DC microgrid DC microgrid with PV and BES BATTERY DC bus voltage
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Proposal for a realtime Einstein-synchronization-defined satellite virtual clock
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作者 严晨皓 汤雪逸 +4 位作者 王时光 孟李皎悦 孙海媛 何奕彬 王力军 《Chinese Physics B》 SCIE EI CAS CSCD 2024年第7期268-276,共9页
Realization of high performance satellite onboard clock is vital for various positioning, navigation, and timing applications. For further improvement of the synchronization-based satellite time and frequency referenc... Realization of high performance satellite onboard clock is vital for various positioning, navigation, and timing applications. For further improvement of the synchronization-based satellite time and frequency references, we propose a geosynchronous(GEO) satellite virtual clock concept based on ground–satellite synchronization and present a beacon transponder structure for its implementation(scheduled for launch in 2025), which does not require atomic clocks to be mounted on the satellite. Its high performance relies only on minor modifications to the existing transponder structure of GEO satellites. We carefully model the carrier phase link and analyze the factors causing link asymmetry within the special relativity. Considering that performance of such synchronization-based satellite clocks is primarily limited by the link's random phase noise, which cannot be adequately modeled, we design a closed-loop experiment based on commercial GEO satellites for pre-evaluation. This experiment aims at extracting the zero-means random part of the ground-satellite Ku-band carrier phase via a feedback loop. Ultimately, we obtain a 1σ value of 0.633 ps(two-way link), following the Gaussian distribution. From this result, we conclude that the proposed real-time Einstein-synchronization-defined satellite virtual clock can achieve picosecond-level replication of onboard time and frequency. 展开更多
关键词 Einstein synchronization satellite virtual clock geosynchronous satellite carrier phase
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Coordinated control strategy for a PV-storage grid-connected system based on a virtual synchronous generator 被引量:4
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作者 Xing Zhang Qian Gao +3 位作者 Zixuan Guo Haizheng Zhang Ming Li Fei Li 《Global Energy Interconnection》 2020年第1期52-60,共9页
Due to the characteristics of intermittent photovoltaic power generation and power fluctuations in distributed photovoltaic power generation,photovoltaic grid-connected systems are usually equipped with energy storage... Due to the characteristics of intermittent photovoltaic power generation and power fluctuations in distributed photovoltaic power generation,photovoltaic grid-connected systems are usually equipped with energy storage units.Most of the structures combined with energy storage are used as the DC side.At the same time,virtual synchronous generators have been widely used in distributed power generation due to their inertial damping and frequency and voltage regulation.For the PV-storage grid-connected system based on virtual synchronous generators,the existing control strategy has unclear function allocation,fluctuations in photovoltaic inverter output power,and high requirements for coordinated control of PV arrays,energy storage units,and photovoltaic inverters,which make the control strategy more complicated.In order to solve the above problems,a control strategy for PV-storage grid-connected system based on a virtual synchronous generator is proposed.In this strategy,the energy storage unit implements maximum power point tracking,and the photovoltaic inverter implements a virtual synchronous generator algorithm,so that the functions implemented by each part of the system are clear,which reduces the requirements for coordinated control.At the same time,the smooth power command is used to suppress the fluctuation of the output power of the photovoltaic inverter.The simulation validates the effectiveness of the proposed method from three aspects:grid-connected operating conditions,frequency-modulated operating conditions,and illumination sudden-drop operating condition.Compared with the existing control strategies,the proposed method simplifies the control strategies and stabilizes the photovoltaic inverter fluctuation in the output power of the inverter. 展开更多
关键词 Photovoltaic power generation Energy STORAGE unit virtual synchronous GENERATOR SMOOTH FLUCTUATION COORDINATED control
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Research on Seamless Switching Control Strategy Based on Virtual Synchronous Generator 被引量:1
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作者 Wei Kang Jibo Wan +1 位作者 Lixia Zhang Qilong Zhang 《Energy and Power Engineering》 2017年第4期436-444,共9页
This paper studies the voltage, phase and current tracking strategy to eliminate voltage and current mutations when the virtual synchronous generator is switching between grid-connected and islanded. By using these st... This paper studies the voltage, phase and current tracking strategy to eliminate voltage and current mutations when the virtual synchronous generator is switching between grid-connected and islanded. By using these strategies the inverter can realize secondary frequency regulation and voltage regulation. If the phase is near 0 or 2π a little disturbance may made the PLL output a big error, so a new PLL is proposed by this paper. A sine module is added in the PLL to avoid this error. In order to verify the strategy proposed by this paper a simulation model is built in Matlab/Simulink. The simulation results show that the control strategy can realize seamless switching. 展开更多
关键词 virtual synchronous GENERATOR PLL SEAMLESS SWITCHING Micro GRID
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Research on Control Strategy of Grid-connected Brushless Doubly-fed Wind Power System Based on Virtual Synchronous Generator Control 被引量:6
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作者 Shuai Liang Shi Jin Long Shi 《CES Transactions on Electrical Machines and Systems》 CSCD 2022年第4期404-412,共9页
The brushless doubly-fed wind power system based on conventional power control strategies lacks ‘inertia’ and the ability to support grid,which leads to the decline of grid stability.Therefore,a control strategy of ... The brushless doubly-fed wind power system based on conventional power control strategies lacks ‘inertia’ and the ability to support grid,which leads to the decline of grid stability.Therefore,a control strategy of brushless doubly-fed reluctance generator(BDFRG) based on virtual synchronous generator(VSG) control is proposed to solve the problem in this paper.The output characteristics of BDFRG based on VSG are similar to a synchronous generator(SG),which can support the grid frequency and increase the system ‘inertia’.According to the mathematical model of BDFRG,the inner loop voltage source control of BDFRG is derived.In addition,the specific structure and parameter selection principle of outer loop VSG control are expounded.The voltage source control inner loop of BDFRG is combined with the VSG control outer loop to establish the overall architecture of BDFRG-VSG control strategy.Finally,the effectiveness and feasibility of the proposed strategy are verified in the simulation. 展开更多
关键词 virtual synchronous generator Brushless doubly-fed relutance generator Grid support ability Voltage source control
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Consensus-Based Distributed Control with Communication Time Delays for Virtual Synchronous Generators in Isolate Microgrid 被引量:1
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作者 Laijun Chen Yuyang Wang +1 位作者 Tianwen Zheng Zhenquan Sun 《Energy and Power Engineering》 2017年第4期102-111,共10页
A consensus-based distributed control method of coordinated VSGs with communication time delays in isolate microgrid is proposed. When time delays are considered in communication, there are some effects on frequency r... A consensus-based distributed control method of coordinated VSGs with communication time delays in isolate microgrid is proposed. When time delays are considered in communication, there are some effects on frequency restoration and active power output allocation. In the control structure, only local information exchange is needed, while the final frequency can be controlled to the nominal value and the VSGs can automatically share loads according to their rated values. An AC microgrid with three VSGs and some loads is implemented. The proposed control strategy is verified by MATLAB/ Simulink simulation results. 展开更多
关键词 virtual synchronous Generator Time DELAYS Distributed Control CONSENSUS Algorithm
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Active Power Allocation of Virtual Synchronous Generator Using Particle Swarm Optimization Approach
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作者 Fathin Saifur Rahman Thongchart Kerdphol +1 位作者 Masayuki Watanabe Yasunori Mitani 《Energy and Power Engineering》 2017年第4期414-424,共11页
In recent years, the penetration of renewable energy sources (RES) is increasing due to energy and environmental issues, causing several problems in the power system. These problems are usually more apparent in microg... In recent years, the penetration of renewable energy sources (RES) is increasing due to energy and environmental issues, causing several problems in the power system. These problems are usually more apparent in microgrids. One of the problems that could arise is frequency stability issue due to lack of inertia in microgrids. Lack of inertia in such system can lead to system instability when a large disturbance occurs in the system. To solve this issue, providing inertia support to the microgrids by a virtual synchronous generator (VSG) utilizing energy storage system is a promising method. In applying VSG, one important aspect is regarding the set value of the active power output from the VSG. The amount of allocated active power during normal operation should be determined carefully so that the frequency of microgrids could be restored to the allowable limits, as close as possible to the nominal value. In this paper, active power allocation of VSG using particle swarm optimization (PSO) is presented. The results show that by using VSG supported by active power allocation determined by the method, frequency stability and dynamic stability of the system could be improved. 展开更多
关键词 virtual synchronous Generator (VSG) virtual INERTIA Particle SWARM Optimization (PSO) Active Power ALLOCATION Microgrid
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A Virtual Synchronous Machine to Support Dynamic Frequency Control in a Mini-Grid That Operates in Frequency Droop Mode
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作者 Miguel Torres Luiz A. C. Lopes 《Energy and Power Engineering》 2013年第3期259-265,共7页
This paper addresses the problem of dynamic frequency control in a diesel-based mini-grid. It is shown that a virtual synchronous machine (VSM) can support dynamic frequency control by adding virtual inertia and dampi... This paper addresses the problem of dynamic frequency control in a diesel-based mini-grid. It is shown that a virtual synchronous machine (VSM) can support dynamic frequency control by adding virtual inertia and damping to the system. However, it is found that the typical formulation of damping power does not work properly when the grid forming gen-set operates in droop mode because of the unknown stabilization value of the grid frequency. As a solution to this problem, an estimator for the stabilization frequency that works in conjunction with the damping function of the VSM is proposed. Theoretical and experimental results provide evidence of a satisfactory performance of the proposed VSM with estimator for different values of the gen-set droop factor. The estimated stabilization frequency converges in approximately 2 s and the maximum frequency deviation during the transient is reduced in 34%, on average. 展开更多
关键词 FREQUENCY Control Mini-Grid INVERTER virtual synchronous Machine
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The Novel Current Control for Virtual Synchronous Generator
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作者 Atsushi Umemura Rion Takahashi Junji Tamura 《Journal of Power and Energy Engineering》 2020年第2期78-89,共12页
In recent years, power generation using renewable energy sources has been developed as a solution to the global warming problem. Among these power generation methods, wind power generation is increasing. However, as t... In recent years, power generation using renewable energy sources has been developed as a solution to the global warming problem. Among these power generation methods, wind power generation is increasing. However, as the penetration level of wind power generation increases, the low inertia and lack of synchronous power characteristics of the penetrated power system can have a significant impact on the transient stability of the grid. The virtual synchronous generator provides the ability of virtual inertia and synchronous power to interconnected inverters. The interconnected inverter with the virtual synchronous generator ability uses, in general, PI control based current controller. This paper proposes a new current-control method and compares it with conventional methods. The proposed current control is a method that follows virtual synchronous generator model that changes every moment by solving the discrete-time linear quadratic optimal control problem for each sampling time interval. The new method follows the conventional method, and therefore the reactive power fluctuation can be suppressed and the interconnected inverter will be downsized. 展开更多
关键词 WIND Energy Generation State Feedback Electric Current CONTROL LINEARIZATION Techniques Discrete Time Model FOLLOWING CONTROL virtual synchronous GENERATOR
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A Study of Discrete-Time Optimum Current Controller for the Virtual Synchronous Generator under Constraints
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作者 Atushi Umemura Rion Takahashi Junji Tamura 《Smart Grid and Renewable Energy》 2020年第1期1-20,共20页
In recent years, power generation using renewable energy sources has been increasing as a solution to the global warning problem. Wind power generation can generate electricity day and night, and it is relatively more... In recent years, power generation using renewable energy sources has been increasing as a solution to the global warning problem. Wind power generation can generate electricity day and night, and it is relatively more efficient among the renewable energy sources. The penetration level of variable-speed wind turbines continues to increase. The interconnected wind turbines, however, have no inertia and no synchronous power. Such devices can have a serious impact on the transient stability of the power grid system. One solution to stabilize such grid with renewable energy sources is to provide emulated inertia and synchronizing power. We have proposed an optimal design method of current control for virtual synchronous generators. This paper proposes an optimal control method that can follow the virtual generator model under constrains. As a result, it is shown that the proposed system can suppress the peak of the output of semiconductor device under instantaneous output voltage drop. 展开更多
关键词 Wind Energy Generation virtual synchronous Generator Electric Current CONTROL Optimal CONTROL Discreate-Time Model Following CONTROL MULTI-OBJECTIVE GENETIC Algorithm
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Modelling and Implementation of Multi-source Isolated Microgrid Using Virtual Synchronous Generator Technology
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作者 CHEN Xing QIAN Shengnan +2 位作者 LI Fei GE Zhaohui CAO Xin 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI CSCD 2021年第5期747-757,共11页
To improve the living standards,economical efficiency and environmental protection of isolated islands,remote areas and other areas with weak electric power facilities construction,a multi-source independent microgrid... To improve the living standards,economical efficiency and environmental protection of isolated islands,remote areas and other areas with weak electric power facilities construction,a multi-source independent microgrid system is studied,including diesel generators,photovoltaic power generation system,wind power generation system and energy storage unit.Meanwhile,in order to realize the voltage and frequency stability control of AC bus of multisource microgrid,the virtual synchronous generator technology is introduced into the energy storage unit,and the charge and discharge control of the energy storage battery are simulated as the control behavior characteristics of synchronous motors,so as to provide damping and inertia support for the microgrid.The operation mode and control principle of each energy subsystem are expounded and analyzed.The algorithm principle of virtual synchronous generator and the control method of energy storage unit are given.Then,the working modes of the microgrid system under different environmental conditions are analyzed,and the multi-source microgrid system simulation model is built based on MATLAB/Simulink.The simulation results show that the microgrid system can run stably under different working modes and the energy storage unit using the virtual synchronous generator technology can provide good voltage and frequency support for the microgrid system.Finally,experiments verify the supporting function of energy storage unit on the voltage and frequency of the microgrid system. 展开更多
关键词 isolated microgrid wind/solar/diesel/storage virtual synchronous generator MODELLING
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Virtual Synchronous Generator Based Current Synchronous Detection Scheme for a Virtual Inertia Emulation in SmartGrids
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作者 Arvind Parwal Martin Fregelius +7 位作者 Dalmo Cardosa Silva Tatiana Potapenko Johannes Hjalmarsson James Kelly Irina Temiz Janaina Goncalves de Oliveira Cecilia Bostrom Mats Leijon 《Energy and Power Engineering》 2019年第3期99-131,共33页
Renewable energy sources, such as photovoltaic wind turbines, and wave power converters, use power converters to connect to the grid which causes a loss in rotational inertia. The attempt to meet the increasing energy... Renewable energy sources, such as photovoltaic wind turbines, and wave power converters, use power converters to connect to the grid which causes a loss in rotational inertia. The attempt to meet the increasing energy demand means that the interest for the integration of renewable energy sources in the existing power system is growing, but such integration poses challenges to the operating stability. Power converters play a major role in the evolution of power system towards SmartGrids, by regulating as virtual synchronous generators. The concept of virtual synchronous generators requires an energy storage system with power converters to emulate virtual inertia similar to the dynamics of traditional synchronous generators. In this paper, a dynamic droop control for the estimation of fundamental reference sources is implemented in the control loop of the converter, including active and reactive power components acting as a mechanical input to the virtual synchronous generator and the virtual excitation controller. An inertia coefficient and a droop coefficient are implemented in the control loop. The proposed controller uses a current synchronous detection scheme to emulate a virtual inertia from the virtual synchronous generators. In this study, a wave energy converter as the power source is used and a power management of virtual synchronous generators to control the frequency deviation and the terminal voltage is implemented. The dynamic control scheme based on a current synchronous detection scheme is presented in detail with a power management control. Finally, we carried out numerical simulations and verified the scheme through the experimental results in a microgrid structure. 展开更多
关键词 Current synchronous Detection Dynamic Droop Control Energy Storage virtual Inertia virtual synchronous Generator
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Synchronous replication of remote storage
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作者 Timur Mirzoev 《通讯和计算机(中英文版)》 2009年第3期34-39,共6页
关键词 同步性 远程存储 网络存储 虚拟
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Control of Virtual Synchronous Generator for Frequency Regulation Using a Coordinated Self-adaptive Method
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作者 Hongwei Fang Zhiwei Yu 《CSEE Journal of Power and Energy Systems》 SCIE EI CSCD 2024年第1期175-184,共10页
Power inverter adopting virtual synchronous generator(VSG)control can provide inertia support for distributed generation systems.However,it cannot take into account the dynamic regulation characteristics of frequency.... Power inverter adopting virtual synchronous generator(VSG)control can provide inertia support for distributed generation systems.However,it cannot take into account the dynamic regulation characteristics of frequency.Thus,when the system encounters a sudden change in load or disturbance,the dynamic process of frequency regulation will be greatly influenced.In view of this issue,an improved VSG control strategy based on a coordinated self-adaptive(CSA)method is proposed.The time domain analysis method is used to study the influences of virtual inertia and damping parameter perturbation on the system steady and dynamic performances.Furthermore,in order to make the control strategy suitable for large load changes and suppress frequency variations beyond the limit,the secondary frequency modulation is introduced into the control loop.Through the coordinated adaptive control of virtual inertia,virtual damping and frequency modulation,the dynamic performance of vSG frequency regulation can be obviously improved.Simulation and experiment results have verified the effectiveness of the proposed CSA control strategy. 展开更多
关键词 Coordinated self-adaptive method frequency regulation time domain analysis virtual synchronous generator
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Finite Control Set Model Predictive Current Control of a Five-Phase PMSM with Virtual Voltage Vectors and Adaptive Control Set 被引量:9
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作者 Wusen Wang Ying Fan +1 位作者 Siyu Chen Qiushi Zhang 《CES Transactions on Electrical Machines and Systems》 2018年第1期136-141,共6页
This paper presents an improved finite control set model predictive current control(FCS-MPCC)of a five-phase permanent magnet synchronous motor(PMSM).First,to avoid including all the 32 voltage vectors provided by a t... This paper presents an improved finite control set model predictive current control(FCS-MPCC)of a five-phase permanent magnet synchronous motor(PMSM).First,to avoid including all the 32 voltage vectors provided by a two-level five-phase inverter into the control set,virtual voltage vectors are adopted.As the third current harmonics can be much reduced by virtual voltage vectors automatically,the harmonic items in the cost function of conventional FCS-MPCC are not considered.Furthermore,an adaptive control set is proposed based on voltage prediction.Best control set with proper voltage vector amplitude corresponding to different rotor speed can be achieved by this method.Consequently,current ripples can be largely reduced and the system performs much better.At last,simulations are established to verify the steady and transient performance of the proposed FCS-MPCC,and experiments based on a 2 kW five-phase motor are carried out.The results have validated the performance improvement of the proposed control strategy. 展开更多
关键词 Adaptive control set current ripple finite control set model predictive current control(FCS-MPCC) permanent magnet synchronous motor(PMSM) virtual voltage vectors
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Development of a Synchronization Method for Fluid-Thermal Study of Hypersonic Flow
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作者 ShenEnnan Lu Zhiliang +1 位作者 Zhou Di Guo Tongqing 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI CSCD 2018年第6期973-985,共13页
A synchronization method is developed for the fluid-thermal study of hypersonic flow.Different from conventional loosely/tightly coupled methods which separately deal with the flow field and the structure temperature ... A synchronization method is developed for the fluid-thermal study of hypersonic flow.Different from conventional loosely/tightly coupled methods which separately deal with the flow field and the structure temperature field,the presented method expresses the governing equations in a unified framework so that the two fields can be calculated simultaneously.For efficiently solving the unified equations,the finite volume method together with the dual-time stepping approach is employed.Like in the flow field,the local time step is also used in the temperature field,which is determined from thermal conductivity spectral radii.In order to treat the fluid-structure interface more conveniently,an expanded virtual boundary is introduced.For validation,several fluid-thermal hypersonic flow problems are simulated.The computed results are compared with those obtained from the coupled methods and the experiment.In the continuous heating problems,the stagnation temperatures predicted by both the coupled and synchronization methods are in good agreements with the experimental data.In the unsteady flowthermal hypersonic flows,the stagnation heat fluxes predicted by the presented method and tightly coupled method are basically the same,which agree better with the experimental data than those predicted by the loosely coupled method.In terms of prediction of the stagnation temperature,the synchronization method shows better accuracy than the tightly coupled method. 展开更多
关键词 HYPERSONIC flow aerothermal synchronIZATION METHOD expanded virtual BOUNDARY CONDUCTIVITY spectral RADII
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A novel frequency synchronization scheme for OFDM systems
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作者 王雯芳 李兵兵 《Journal of Harbin Institute of Technology(New Series)》 EI CAS 2008年第5期653-656,共4页
A novel frequency synchronization scheme for orthogonal frequency division multiplexing (OFDM) systems is proposed, including a novel frequency offset estimation algorithm and a novel frequency offset compensation alg... A novel frequency synchronization scheme for orthogonal frequency division multiplexing (OFDM) systems is proposed, including a novel frequency offset estimation algorithm and a novel frequency offset compensation algorithm. The frequency offset estimation includes both the fractional frequency offset (FFO) estimation and the integral frequency offset (IFO) estimation. Firstly, the FFO was obtained by the conventional ML algorithm in time domain. After the FFO was compensated in time domain, the IFO was obtained by the proposed algorithm based on the energy of virtual carriers. This algorithm needs only simple calculations and has a large frequency offset estimation range. Furthermore, it is insensitive to symbol synchronization errors and channel changing. Finally, the IFO was compensated based on the carrier-positions offset, which can be completed through carrier-positions cyclic shifts in frequency domain. This proposed frequency synchronization scheme can decrease the system redundancy without any need of assistant data, and can be applied to the fast synchronization with the only need of one OFDM symbol. The analyses and simulations show the improved performance of the proposed frequency synchronization scheme. 展开更多
关键词 OFDM systems frequency synchronization virtual carriers ML
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基于功率微分项的双VSG有功功率振荡抑制策略 被引量:4
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作者 朱军 袁亚飞 +4 位作者 刘鹏辉 杜少通 郭向伟 杨明 曲玉博 《电机与控制学报》 EI CSCD 北大核心 2024年第1期177-188,共12页
针对虚拟同步发电机(VSG)双机并联运行时产生的有功功率振荡问题,通过建立双VSG系统的小信号模型,分析了有功功率振荡产生的机理,提出一种基于改进虚拟阻抗的瞬态功率均分策略和一种基于功率微分项的自适应惯量和阻尼的功率振荡抑制策略... 针对虚拟同步发电机(VSG)双机并联运行时产生的有功功率振荡问题,通过建立双VSG系统的小信号模型,分析了有功功率振荡产生的机理,提出一种基于改进虚拟阻抗的瞬态功率均分策略和一种基于功率微分项的自适应惯量和阻尼的功率振荡抑制策略,将有功功率微分项与角加速度结合起来实现惯量的自适应调节,同时将有功功率微分项引入阻尼控制环节以替代传统的阻尼项,实现阻尼的自适应调节。所提出的策略可以使动态时VSG之间的角频率差更快速地趋近于零,从而减小有功功率振荡的超调,改善频率动态响应性能。搭建了VSG并联的仿真模型,仿真结果表明:所提改进控制策略可以使瞬态时实现有功均分,使动态时的有功功率振荡超调减小41%,振荡过程减小了1秒。 展开更多
关键词 虚拟同步发电机 功率微分项 自适应惯量 阻尼 功率振荡抑制 功率均分
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