Micro-grid smooth switchover between different operation modes is important for steady operation and reliable power supply of micro-grid. In order to reduce the transient fluctuation of voltage and frequency during sw...Micro-grid smooth switchover between different operation modes is important for steady operation and reliable power supply of micro-grid. In order to reduce the transient fluctuation of voltage and frequency during switchover, this paper proposed a new switchover method based on controller state following. When transferring to island mode, the control method for inverter of storage device changed from PQ control to V/f control. Before switchover, the output of V/f controller is always following the output of PQ controller. So that the sudden change of output is avoided at the moment of switchover. A micro-grid model with photovoltaic and battery is built on DIgSILENT Power Factory simulation software, to simulate micro-grid switchover from grid-connected mode to island mode. Results show this method can effectively suppress the transient fluctuation of voltage and frequency, and reduce the influence of transient process on power grid. This conclusion has important practical significance on micro-grid smooth switchover from grid-con- nected mode to island mode.展开更多
The merits of compressed air energy storage(CAES)include large power generation capacity,long service life,and environmental safety.When a CAES plant is switched to the grid-connected mode and participates in grid reg...The merits of compressed air energy storage(CAES)include large power generation capacity,long service life,and environmental safety.When a CAES plant is switched to the grid-connected mode and participates in grid regulation,using the traditional control mode with low accuracy can result in excess grid-connected impulse current and junction voltage.This occurs because the CAES output voltage does not match the frequency,amplitude,and phase of the power grid voltage.Therefore,an adaptive linear active disturbance-rejection control(A-LADRC)strategy was proposed.Based on the LADRC strategy,which is more accurate than the traditional proportional integral controller,the proposed controller is enhanced to allow adaptive adjustment of bandwidth parameters,resulting in improved accuracy and response speed.The problem of large impulse current when CAES is switched to the grid-connected mode is addressed,and the frequency fluctuation is reduced.Finally,the effectiveness of the proposed strategy in reducing the impact of CAES on the grid connection was verified using a hardware-in-the-loop simulation platform.The influence of the k value in the adaptive-adjustment formula on the A-LADRC was analyzed through simulation.The anti-interference performance of the control was verified by increasing and decreasing the load during the presynchronization process.展开更多
The core of smoothed particle hydrodynamics （SPH） is the nearest neighbor search subroutine. In this paper, a nearest neighbor search algorithm which is based on multiple background grids and support variable smooth...The core of smoothed particle hydrodynamics （SPH） is the nearest neighbor search subroutine. In this paper, a nearest neighbor search algorithm which is based on multiple background grids and support variable smooth length is introduced. Through tested on lid driven cavity flow, it is clear that this method can provide high accuracy. Analysis and experiments have been made on its parallelism, and the results show that this method has better parallelism and with adding processors its accuracy become higher, thus it achieves that efficiency grows in pace with accuracy.展开更多
The importance of computational grids in hydraulic numerical models is studied by numerical simulation of jet flow in a rectangular duct which is linked with a fixed width inlet and a different width outlet using a st...The importance of computational grids in hydraulic numerical models is studied by numerical simulation of jet flow in a rectangular duct which is linked with a fixed width inlet and a different width outlet using a standard k-epsilon turbulence model. The computational results show the numerical solutions may not be reasonable because of the incorrect computational grid and each numerical model bass grid-independent solution. The computational grid has a definitive effect on the accuracy and stability of the computational solution, which must be divided well according to the simulated geometry and physical characters of hydraulic problems. The main guidelines about the formation of computational grid in such aspects as node distribution, smoothness and skewness of grid, have been given.展开更多
This paper extends the SPH method to gas simulation. The SPH （Smoothed Particles Hydrodynamics） method is the most popular method of flow simulation, which is widely used in large-scale liquid simulation. However, i...This paper extends the SPH method to gas simulation. The SPH （Smoothed Particles Hydrodynamics） method is the most popular method of flow simulation, which is widely used in large-scale liquid simulation. However, it is not found to apply to gas simulation, since those methods based on SPH can＇t be used in real-time simulation due to their enormous particles and huge computation. This paper proposes a method for gas simulation based on SPH with a small number of particles. Firstly, the method computes the position and density of each particle in each point-in-time, and outlines the shape of the simulated gas based on those particles. Secondly the method uses the grid technique to refine the shape with the diffusion of particle＇s density under the control of grid, and get more lifelike simulation result. Each grid will be assigned density according to the particles in it. The density determines the final appearance of the grid. For ensuring the natural transition of the color between adjacent grids, we give a diffuse process of density between these grids and assign appropriate values to vertexes of these grids. The experimental results show that the proposed method can give better gas simulation and meet the request of real-time.展开更多
文摘Micro-grid smooth switchover between different operation modes is important for steady operation and reliable power supply of micro-grid. In order to reduce the transient fluctuation of voltage and frequency during switchover, this paper proposed a new switchover method based on controller state following. When transferring to island mode, the control method for inverter of storage device changed from PQ control to V/f control. Before switchover, the output of V/f controller is always following the output of PQ controller. So that the sudden change of output is avoided at the moment of switchover. A micro-grid model with photovoltaic and battery is built on DIgSILENT Power Factory simulation software, to simulate micro-grid switchover from grid-connected mode to island mode. Results show this method can effectively suppress the transient fluctuation of voltage and frequency, and reduce the influence of transient process on power grid. This conclusion has important practical significance on micro-grid smooth switchover from grid-con- nected mode to island mode.
基金supported by National Natural Science Foundation of China(Project No.52077079).
文摘The merits of compressed air energy storage(CAES)include large power generation capacity,long service life,and environmental safety.When a CAES plant is switched to the grid-connected mode and participates in grid regulation,using the traditional control mode with low accuracy can result in excess grid-connected impulse current and junction voltage.This occurs because the CAES output voltage does not match the frequency,amplitude,and phase of the power grid voltage.Therefore,an adaptive linear active disturbance-rejection control(A-LADRC)strategy was proposed.Based on the LADRC strategy,which is more accurate than the traditional proportional integral controller,the proposed controller is enhanced to allow adaptive adjustment of bandwidth parameters,resulting in improved accuracy and response speed.The problem of large impulse current when CAES is switched to the grid-connected mode is addressed,and the frequency fluctuation is reduced.Finally,the effectiveness of the proposed strategy in reducing the impact of CAES on the grid connection was verified using a hardware-in-the-loop simulation platform.The influence of the k value in the adaptive-adjustment formula on the A-LADRC was analyzed through simulation.The anti-interference performance of the control was verified by increasing and decreasing the load during the presynchronization process.
基金Project supported by the National Natural Science Foundation of China(Grant No.11002086)the Shanghai Leading Academic Discipline Project(Grant No.J50103)
文摘The core of smoothed particle hydrodynamics （SPH） is the nearest neighbor search subroutine. In this paper, a nearest neighbor search algorithm which is based on multiple background grids and support variable smooth length is introduced. Through tested on lid driven cavity flow, it is clear that this method can provide high accuracy. Analysis and experiments have been made on its parallelism, and the results show that this method has better parallelism and with adding processors its accuracy become higher, thus it achieves that efficiency grows in pace with accuracy.
文摘The importance of computational grids in hydraulic numerical models is studied by numerical simulation of jet flow in a rectangular duct which is linked with a fixed width inlet and a different width outlet using a standard k-epsilon turbulence model. The computational results show the numerical solutions may not be reasonable because of the incorrect computational grid and each numerical model bass grid-independent solution. The computational grid has a definitive effect on the accuracy and stability of the computational solution, which must be divided well according to the simulated geometry and physical characters of hydraulic problems. The main guidelines about the formation of computational grid in such aspects as node distribution, smoothness and skewness of grid, have been given.
基金Supported by National Natural Science Foundation of China(No.61272024)
文摘This paper extends the SPH method to gas simulation. The SPH （Smoothed Particles Hydrodynamics） method is the most popular method of flow simulation, which is widely used in large-scale liquid simulation. However, it is not found to apply to gas simulation, since those methods based on SPH can＇t be used in real-time simulation due to their enormous particles and huge computation. This paper proposes a method for gas simulation based on SPH with a small number of particles. Firstly, the method computes the position and density of each particle in each point-in-time, and outlines the shape of the simulated gas based on those particles. Secondly the method uses the grid technique to refine the shape with the diffusion of particle＇s density under the control of grid, and get more lifelike simulation result. Each grid will be assigned density according to the particles in it. The density determines the final appearance of the grid. For ensuring the natural transition of the color between adjacent grids, we give a diffuse process of density between these grids and assign appropriate values to vertexes of these grids. The experimental results show that the proposed method can give better gas simulation and meet the request of real-time.
