目前,在含统一潮流控制器(unified power flow controller,UPFC)的电网静态安全分析中,UPFC的控制目标有功功率、无功功率通常采用典型运行数据进行离线分析,控制目标值由试探法确定,计算效率低且和实际运行工况存在一定的差异。为弥补...目前,在含统一潮流控制器(unified power flow controller,UPFC)的电网静态安全分析中,UPFC的控制目标有功功率、无功功率通常采用典型运行数据进行离线分析,控制目标值由试探法确定,计算效率低且和实际运行工况存在一定的差异。为弥补现有控制策略整定方法的不足,文中提出了采用潮流转移分布因子的UPFC控制值整定方法,当电网发生N-1故障时,基于直流潮流法定量计算控制目标值,通过UPFC的潮流控制功能消除线路N-1过载,控制策略可根据能量管理系统(energy management system,EMS)数据在线刷新,可为电网调度提供辅助决策。算例仿真验证了文中算法的有效性和实用性。展开更多
Background:Athletes have been shown to exhibit better balance compared to non-athletes(NON).However,few studies have investigated how the surface on which athletes train affects the strategies adopted to maintain bala...Background:Athletes have been shown to exhibit better balance compared to non-athletes(NON).However,few studies have investigated how the surface on which athletes train affects the strategies adopted to maintain balance.Two distinct athlete groups who experience different types of sport-specific balance training are stable surface athletes(SSA) such as basketball players and those who train on unstable surfaces(USA) such as surfers.The purpose of this study was to investigate the effects of training surface on dynamic balance in athletes compared to NON.Methods:Eight NON,eight SSA,and eight USA performed five 20-s trials in each of five experimental conditions including a static condition and four dynamic conditions in which the support surface translated in the anteroposterior(AP) or mediolateral(ML) planes using positive or negative feedback paradigms.Approximate entropy(Ap En) and root mean square distance(RMS) of the center of pressure(Co P) were calculated for the AP and ML directions.Four 3 × 5(group × condition) repeated measures ANOVAs were used to determine significant effects of group and condition on variables of interest.Results:USA exhibited smaller Ap En values than SSA in the AP signals while no significant differences were observed in the ML Co P signals.Generally,the negative feedback conditions were associated with significantly greater RMS values than the positive feedback conditions.Conclusion:USA exhibit unique postural strategies compared to SSA.These unique strategies seemingly exhibit a direction-specific attribute and may be associated with divergent motor control strategies.展开更多
文摘Background:Athletes have been shown to exhibit better balance compared to non-athletes(NON).However,few studies have investigated how the surface on which athletes train affects the strategies adopted to maintain balance.Two distinct athlete groups who experience different types of sport-specific balance training are stable surface athletes(SSA) such as basketball players and those who train on unstable surfaces(USA) such as surfers.The purpose of this study was to investigate the effects of training surface on dynamic balance in athletes compared to NON.Methods:Eight NON,eight SSA,and eight USA performed five 20-s trials in each of five experimental conditions including a static condition and four dynamic conditions in which the support surface translated in the anteroposterior(AP) or mediolateral(ML) planes using positive or negative feedback paradigms.Approximate entropy(Ap En) and root mean square distance(RMS) of the center of pressure(Co P) were calculated for the AP and ML directions.Four 3 × 5(group × condition) repeated measures ANOVAs were used to determine significant effects of group and condition on variables of interest.Results:USA exhibited smaller Ap En values than SSA in the AP signals while no significant differences were observed in the ML Co P signals.Generally,the negative feedback conditions were associated with significantly greater RMS values than the positive feedback conditions.Conclusion:USA exhibit unique postural strategies compared to SSA.These unique strategies seemingly exhibit a direction-specific attribute and may be associated with divergent motor control strategies.
