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
To remediate the problem of severe or total losses,and meet the requirements of borehole plugging and pumping at different well depths,a novel crosslinked polymer gel(named HPG/Zr gel)with controlled gelation time and...To remediate the problem of severe or total losses,and meet the requirements of borehole plugging and pumping at different well depths,a novel crosslinked polymer gel(named HPG/Zr gel)with controlled gelation time and high gel strength was developed as loss circulation material,which mainly comprised hydroxypropyl guar gum,zirconium compound and triethanolamine.The influence of hydroxypropyl guar gum concentration,zirconium compound concentration,triethanolamine concentration and temperature on the gelation time of HPG/Zr gel was evaluated.In addition,the performance of HPG/Zr gel was investigated in terms of temperature resistance and shear resistance property,plugging ability and supporting cement slurry ability.According to the results,HPG/Zr gel can form a viscoelastic body with a network structure,and its gelation time can be practically adjustable.The results of the plugging experiment at different temperatures,pressures and pore sizes of quartz sand revealed that HPG/Zr gel could effectively plug sand pores at 150℃,and its pressure-bearing capacity can be up to 5 MPa.Employing its flow resistance and ability of supporting cement slurry,HPG/Zr gel was successfully applied in two geological boreholes by combining with cement slurry.Overall,the results of laboratory research and field tests indicate that HPG/Zr gel is useful for mitigating the lost circulation,and it is of huge importance to engineering applications.展开更多
基金supported in part by the National Natural Science Foundation of China under Grant 51537007。
文摘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.
基金supported by the National Key Research and Development Program of China(No.2018YFC0603406).
文摘To remediate the problem of severe or total losses,and meet the requirements of borehole plugging and pumping at different well depths,a novel crosslinked polymer gel(named HPG/Zr gel)with controlled gelation time and high gel strength was developed as loss circulation material,which mainly comprised hydroxypropyl guar gum,zirconium compound and triethanolamine.The influence of hydroxypropyl guar gum concentration,zirconium compound concentration,triethanolamine concentration and temperature on the gelation time of HPG/Zr gel was evaluated.In addition,the performance of HPG/Zr gel was investigated in terms of temperature resistance and shear resistance property,plugging ability and supporting cement slurry ability.According to the results,HPG/Zr gel can form a viscoelastic body with a network structure,and its gelation time can be practically adjustable.The results of the plugging experiment at different temperatures,pressures and pore sizes of quartz sand revealed that HPG/Zr gel could effectively plug sand pores at 150℃,and its pressure-bearing capacity can be up to 5 MPa.Employing its flow resistance and ability of supporting cement slurry,HPG/Zr gel was successfully applied in two geological boreholes by combining with cement slurry.Overall,the results of laboratory research and field tests indicate that HPG/Zr gel is useful for mitigating the lost circulation,and it is of huge importance to engineering applications.
