Based on multi-module-cascaded inverter topology, this study presented a universal multilevel inverter hybrid topology and unified the researches on multilevel inverter topology. According to the freedom of this unive...Based on multi-module-cascaded inverter topology, this study presented a universal multilevel inverter hybrid topology and unified the researches on multilevel inverter topology. According to the freedom of this universal topology, several new hybrid topologies were constructed. Also, based on conventional modulation strategies- multi-carrier SPWM (Sinusoidal Pulse Width Modulation), hybrid modulation strategies were introduced corresponding to hybrid topologies, and a multilevel SVPWM (Space Vector Pulse Width Modulation) technique based on phase-shifted theory was naturally produced. Simulation and experiment results prove that hybrid topologies and corresponding modulation strategies are valid, which lay a foundation for practical application of hybrid multilevel inverter topologies.展开更多
The truncation error and propagation error are analyzed for velocity determination through differential GPS carrier phase observations,and an approach for the choice of the best number of points for the central differ...The truncation error and propagation error are analyzed for velocity determination through differential GPS carrier phase observations,and an approach for the choice of the best number of points for the central difference method is developed.In order to overcome the disadvantages of existing GPS velocity determination methods,a new velocity determination algorithm is presented,based on combining carrier phase and Doppler observations.The basic idea is that two types of observation are combined by adding their normal equations,and their weights are evaluated by strict Helmet variance-components estimation.In order to control the influence of outliers,a bifactor equivalent weights strategy is adopted.To validate this method,GPS data of the airborne gravimetry campaign MEXAGE2001 is tested.The results show that the precision and reliability of velocity determination are obviously improved by using the proposed method.展开更多
文摘Based on multi-module-cascaded inverter topology, this study presented a universal multilevel inverter hybrid topology and unified the researches on multilevel inverter topology. According to the freedom of this universal topology, several new hybrid topologies were constructed. Also, based on conventional modulation strategies- multi-carrier SPWM (Sinusoidal Pulse Width Modulation), hybrid modulation strategies were introduced corresponding to hybrid topologies, and a multilevel SVPWM (Space Vector Pulse Width Modulation) technique based on phase-shifted theory was naturally produced. Simulation and experiment results prove that hybrid topologies and corresponding modulation strategies are valid, which lay a foundation for practical application of hybrid multilevel inverter topologies.
基金supported by the National High Technology Research and Development of China (Grant No.2006AA12Z22)the National Natural Science Foundation of China (Grant No.40604003)+1 种基金the Foundation for Author of National Excellent Doctoral Dissertation of China (Grant No.2007B51)the China Postdoctoral Science Foundation (Grant No.20080430148,2009020444)
文摘The truncation error and propagation error are analyzed for velocity determination through differential GPS carrier phase observations,and an approach for the choice of the best number of points for the central difference method is developed.In order to overcome the disadvantages of existing GPS velocity determination methods,a new velocity determination algorithm is presented,based on combining carrier phase and Doppler observations.The basic idea is that two types of observation are combined by adding their normal equations,and their weights are evaluated by strict Helmet variance-components estimation.In order to control the influence of outliers,a bifactor equivalent weights strategy is adopted.To validate this method,GPS data of the airborne gravimetry campaign MEXAGE2001 is tested.The results show that the precision and reliability of velocity determination are obviously improved by using the proposed method.
