Due to wide input fluctuation with line frequency of 50 Hz, power-factor-correction （PFC） Boost converters tend to exhibit fast-scale instability over time domain. The traditional remedy is to impose slope compensat...Due to wide input fluctuation with line frequency of 50 Hz, power-factor-correction （PFC） Boost converters tend to exhibit fast-scale instability over time domain. The traditional remedy is to impose slope compensation so as to weaken or eliminate this instability. A theoretical principle on the implementation of slope compensation signal is still lacking. Empirical design will induce over compensation frequently, resulting in a large decrease of power factor. In order to tackle this issue, by constructing the discrete-time iterative map of the PFC Boost converter from the viewpoint of bifurcation control theory of nonlinear systems, consequently, the criterion of critical stability for the PFC circuit can be established. Based on this stability criterion, appropriate design of slope compensation can be achieved. Our work indicates that 3 main circuit parameters （i.e. switching cycle, output reference voltage and inductor） determine the effective amplitude design of the slope compensation signal. The results, validated by a large quantity of analytical and numerical studies, show that appropriate slope compensation can be effective in weakening （or controlling） fast-scale bifurcation while maintaining a rather high input power factor.展开更多
In this paper we report a kind of fast-scale instability occurring in the single-ended primary inductance converter （SEPIC） power factor pre-regulator, which is designed to operate in discontinuous conduction mode. ...In this paper we report a kind of fast-scale instability occurring in the single-ended primary inductance converter （SEPIC） power factor pre-regulator, which is designed to operate in discontinuous conduction mode. Main results are given by exact cycle-by-cycle computer simulations as well as theoretical analysis. It is found that the instability phenomenon manifests itself as a fast-scale bifurcation at the switching period, which implies the occurrence of border collision bifurcation, or is related to the transition of the regular operating mode of the SEPIC. According to the theoretical analysis and simulation results, the effects of parameters on system stability, and the locations of the bifurcation points are confirmed. Moreover, the effects of such an instability on power factor and switching stress are also discussed. Finally, the occurrence of the asymmetric bifurcation locations is investigated. The results show that this work provides a convenient means of predicting stability boundaries which can facilitate the selection of the practical parameters.展开更多
为了实现生猪耳根体表温度自动检测,减少快速判别尺寸空间跟踪(Fast discriminative scale space tracking,FDSST)方法在热红外视频中进行头部跟踪产生的误差,提出了一种利用骨架扫描策略改进FDSST的生猪耳根体表温度检测方法。首先对...为了实现生猪耳根体表温度自动检测,减少快速判别尺寸空间跟踪(Fast discriminative scale space tracking,FDSST)方法在热红外视频中进行头部跟踪产生的误差,提出了一种利用骨架扫描策略改进FDSST的生猪耳根体表温度检测方法。首先对视频的初始帧进行预处理,提取精简后的生猪整体骨架;其次,设计骨架扫描策略,扫描头部骨架前端关键点,实现头部在初始帧的定位;再次,采用FDSST跟踪生猪头部,每连续跟踪N帧后,采用骨架扫描策略重新定位头部,减少跟踪框漂移;最后提出耳根体表温度提取方法,根据头部左右耳侧温度分布,提取耳根温度并误差校正。利用采集到的30只生猪的视频数据,在Matlab平台上进行了测试,并与FDSST算法、压缩感知跟踪和核相关滤波跟踪等高效算法对比分析。结果表明,本文方法的跟踪平均精确度分别提高了7.82、11.82、8.78个百分点,提取的耳根最大温度误差为0.32℃。展开更多
基金Supported by the National Natural Science Foundation of China (Grant Nos. 60402001, 60672023)the Science and Technological Fund of Anhui Province for Outstanding Youth (Grant No. 08040106807)
文摘Due to wide input fluctuation with line frequency of 50 Hz, power-factor-correction （PFC） Boost converters tend to exhibit fast-scale instability over time domain. The traditional remedy is to impose slope compensation so as to weaken or eliminate this instability. A theoretical principle on the implementation of slope compensation signal is still lacking. Empirical design will induce over compensation frequently, resulting in a large decrease of power factor. In order to tackle this issue, by constructing the discrete-time iterative map of the PFC Boost converter from the viewpoint of bifurcation control theory of nonlinear systems, consequently, the criterion of critical stability for the PFC circuit can be established. Based on this stability criterion, appropriate design of slope compensation can be achieved. Our work indicates that 3 main circuit parameters （i.e. switching cycle, output reference voltage and inductor） determine the effective amplitude design of the slope compensation signal. The results, validated by a large quantity of analytical and numerical studies, show that appropriate slope compensation can be effective in weakening （or controlling） fast-scale bifurcation while maintaining a rather high input power factor.
文摘In this paper we report a kind of fast-scale instability occurring in the single-ended primary inductance converter （SEPIC） power factor pre-regulator, which is designed to operate in discontinuous conduction mode. Main results are given by exact cycle-by-cycle computer simulations as well as theoretical analysis. It is found that the instability phenomenon manifests itself as a fast-scale bifurcation at the switching period, which implies the occurrence of border collision bifurcation, or is related to the transition of the regular operating mode of the SEPIC. According to the theoretical analysis and simulation results, the effects of parameters on system stability, and the locations of the bifurcation points are confirmed. Moreover, the effects of such an instability on power factor and switching stress are also discussed. Finally, the occurrence of the asymmetric bifurcation locations is investigated. The results show that this work provides a convenient means of predicting stability boundaries which can facilitate the selection of the practical parameters.
文摘为了实现生猪耳根体表温度自动检测,减少快速判别尺寸空间跟踪(Fast discriminative scale space tracking,FDSST)方法在热红外视频中进行头部跟踪产生的误差,提出了一种利用骨架扫描策略改进FDSST的生猪耳根体表温度检测方法。首先对视频的初始帧进行预处理,提取精简后的生猪整体骨架;其次,设计骨架扫描策略,扫描头部骨架前端关键点,实现头部在初始帧的定位;再次,采用FDSST跟踪生猪头部,每连续跟踪N帧后,采用骨架扫描策略重新定位头部,减少跟踪框漂移;最后提出耳根体表温度提取方法,根据头部左右耳侧温度分布,提取耳根温度并误差校正。利用采集到的30只生猪的视频数据,在Matlab平台上进行了测试,并与FDSST算法、压缩感知跟踪和核相关滤波跟踪等高效算法对比分析。结果表明,本文方法的跟踪平均精确度分别提高了7.82、11.82、8.78个百分点,提取的耳根最大温度误差为0.32℃。
