Vehicle positioning with the global navigation satellite system （GNSS） in urban environments faces two problems which are attenuation and dynamic. For traditional GNSS receivers hardly able to track dynamic weak sig...Vehicle positioning with the global navigation satellite system （GNSS） in urban environments faces two problems which are attenuation and dynamic. For traditional GNSS receivers hardly able to track dynamic weak signals, the coupling between all visible satellite signals is ignored in the absence of navigation state feedback, and thermal noise error and dynamic stress threshold are contradictory due to non-coherent discriminators. The vector delay/frequency locked loop （VDFLL） with navigation state feedback and the joint vector tracking loop （JVTL） with coherent discriminator which is a synchronization parameter tracking loop based on maximum likelihood estimation （MLE） are proposed to improve the tracking sensitivity of GNSS receiver in dynamic weak signal environments. A joint vector position tracking loop （JVPTL） directly tracking user position and velocity is proposed to further improve tracking sensitivity. The coherent navigation parameter discriminator of JVPTL, being able to ease the contradiction between thermal noise error and dynamic stress threshold, is based on MLE according to the navigation parameter based linear model of received baseband signals. Simulation results show that JVPTL, which combines the advantages of both VDFLL and JVTL, performs better than both VDFLL and JVTL in dynamic weak signal environments.展开更多
压缩空气储能(Compressed air energy storage,CAES)因其寿命长、经济性好等优点在微电网中前景广泛。直驱型压缩空气储能(Direct-drive compressed air energy storage,DD-CAES)因其灵活性高、转速可变、效率较高等优势广泛应用于分布...压缩空气储能(Compressed air energy storage,CAES)因其寿命长、经济性好等优点在微电网中前景广泛。直驱型压缩空气储能(Direct-drive compressed air energy storage,DD-CAES)因其灵活性高、转速可变、效率较高等优势广泛应用于分布式压缩空气储能系统,但DD-CAES透平发电系统是具有非线性、强耦合的复杂系统,采用传统比例积分(Proportional-integral,PI)控制在功率跟踪和频率调节时易出现功率波动,进而导致频率扰动。因此,建立直驱型压缩空气储能透平发电系统的动态仿真模型,提出一种基于改进线性自抗扰控制(Linear active disturbance rejection control,LADRC)的DD-CAES调频控制策略,其控制系统主要包含用于预留容量的变工况功率跟踪模块和用于频率调节的变流器控制模块,对系统动态响应特性与调频特性分析可知,该控制系统可实现部分负载下的稳定频率支撑,且改进自抗扰控制可有效减小系统功率波动。最后通过仿真试验,验证不同工况场景下所提控制策略可在响应速度不变的前提下,同时减少系统最大频率偏差量(6.43%)和频率变化率最大值(11.65%),为建立电网友好型直驱型压缩空气储能电站提供了理论参考。展开更多
基金supported by the National Natural Science Foundation for Young Scientists of China(61201190)
文摘Vehicle positioning with the global navigation satellite system （GNSS） in urban environments faces two problems which are attenuation and dynamic. For traditional GNSS receivers hardly able to track dynamic weak signals, the coupling between all visible satellite signals is ignored in the absence of navigation state feedback, and thermal noise error and dynamic stress threshold are contradictory due to non-coherent discriminators. The vector delay/frequency locked loop （VDFLL） with navigation state feedback and the joint vector tracking loop （JVTL） with coherent discriminator which is a synchronization parameter tracking loop based on maximum likelihood estimation （MLE） are proposed to improve the tracking sensitivity of GNSS receiver in dynamic weak signal environments. A joint vector position tracking loop （JVPTL） directly tracking user position and velocity is proposed to further improve tracking sensitivity. The coherent navigation parameter discriminator of JVPTL, being able to ease the contradiction between thermal noise error and dynamic stress threshold, is based on MLE according to the navigation parameter based linear model of received baseband signals. Simulation results show that JVPTL, which combines the advantages of both VDFLL and JVTL, performs better than both VDFLL and JVTL in dynamic weak signal environments.
文摘压缩空气储能(Compressed air energy storage,CAES)因其寿命长、经济性好等优点在微电网中前景广泛。直驱型压缩空气储能(Direct-drive compressed air energy storage,DD-CAES)因其灵活性高、转速可变、效率较高等优势广泛应用于分布式压缩空气储能系统,但DD-CAES透平发电系统是具有非线性、强耦合的复杂系统,采用传统比例积分(Proportional-integral,PI)控制在功率跟踪和频率调节时易出现功率波动,进而导致频率扰动。因此,建立直驱型压缩空气储能透平发电系统的动态仿真模型,提出一种基于改进线性自抗扰控制(Linear active disturbance rejection control,LADRC)的DD-CAES调频控制策略,其控制系统主要包含用于预留容量的变工况功率跟踪模块和用于频率调节的变流器控制模块,对系统动态响应特性与调频特性分析可知,该控制系统可实现部分负载下的稳定频率支撑,且改进自抗扰控制可有效减小系统功率波动。最后通过仿真试验,验证不同工况场景下所提控制策略可在响应速度不变的前提下,同时减少系统最大频率偏差量(6.43%)和频率变化率最大值(11.65%),为建立电网友好型直驱型压缩空气储能电站提供了理论参考。
