鲁棒控制方法可用于高压直流附加阻尼控制器的设计,用以抑制交直流系统低频振荡,但目前普遍存在控制器阶数过高的问题,对实用性影响较大。为此提出对H2/H∞鲁棒控制器进行降阶的动态射影控制方法,并对降阶过程中产生的误差进行优化。首...鲁棒控制方法可用于高压直流附加阻尼控制器的设计,用以抑制交直流系统低频振荡,但目前普遍存在控制器阶数过高的问题,对实用性影响较大。为此提出对H2/H∞鲁棒控制器进行降阶的动态射影控制方法,并对降阶过程中产生的误差进行优化。首先利用总体最小二乘-旋转不变子空间(total least squares-estimation of signal parameters via rotational invariance techniques,TLS-ESPRIT)方法对系统进行低频振荡特性辨识,在此基础上利用主模比指标选择合适的反馈信号;然后利用H2/H∞鲁棒控制理论设计状态反馈鲁棒控制器;最后应用动态射影控制进行降阶,同时利用共轭梯度法对由FH范数评价的误差系统进行优化,得到最优低阶输出反馈控制器。仿真结果表明基于误差最小化射影控制的降阶高压直流鲁棒控制器在不同扰动与故障下都能有效抑制系统的低频振荡,鲁棒性和控制性能强,同时控制器阶数低,适合于实际工程推广应用。展开更多
针对含规模化风电接入的交直流电力系统的频率稳定问题,以抑制风电出力大幅度随机扰动引起的频率波动为目的,提出了高压直流输电(high voltage direct current transmission,HVDC)附加频率控制(frequency control,AFC)和自动发电控制(au...针对含规模化风电接入的交直流电力系统的频率稳定问题,以抑制风电出力大幅度随机扰动引起的频率波动为目的,提出了高压直流输电(high voltage direct current transmission,HVDC)附加频率控制(frequency control,AFC)和自动发电控制(automatic generation control,AGC)配合的辅助频率控制策略。该策略在风电出力发生大幅度随机扰动时,AFC利用HVDC功率快速调制和短时过载能力快速平衡风电出力扰动中变化较快的分量,控制器基于TLS-ESPRIT算法和改进射影控制理论设计,阶数低,易于工程实现;基于传统PI控制的AGC自动跟踪电网功率波动,调整调频机组出力平衡变化较慢的有功功率扰动分量,维持系统有功功率平衡,保持电力系统频率稳定。最后,利用PSCAD/EMTDC在改造的四机两区域模型中进行了仿真分析,结果表明所提策略充分利用了交直流电力系统的频率调节能力,能较好地抑制风电出力引起的频率波动。展开更多
The purpose of this study was to examine the impact of macro social factors （states, religion, region, Arab spring, terrorism, unrest （Shoe index）, democracy, corruption （GPI）, Human development （HDI）, low self...The purpose of this study was to examine the impact of macro social factors （states, religion, region, Arab spring, terrorism, unrest （Shoe index）, democracy, corruption （GPI）, Human development （HDI）, low self-control, life stress events （LSE）, youth unemployment, religiosity, feeling （fear and anger）, youth unemployment and total unemployment） on Arab youth＇s radicalization. A sample of 6,730 Arab youth age 15-24 years was selected from Kuwait, UAE, KSA, Oman, Qatar, Bahrain, Jordan, Tunisia, Libya, Morocco, Lebanon, Egypt, Gaza and Palestine and Syrian refuges in Jordan. A questionnaire of 43 items to measure radicalization was developed based on the literature review. A construct validity of the scale was estimated by calculating the correlation between radicalization scale and Low self-control scale and found a positive significant relationship （0.680, a = 0.000）, a sign of validity of the scale. A Reliability of the scale is strong and was estimated by Cronbach＇s alpha and was 0.947. An average of 46.6% of the participants was categorized as radicals with standard deviation of 12. Macro social factors explained 64% of the variance on radicalization. It has a significant impact on radicalization （F = 807.6, a = 0.000）. Each single variable has a significant impact. The analysis revealed three groups of macro determinants of youth radicalization were identified： （1） Geographic factors： state, region, and Arab spring; （2） Social factors： religion, religiously, feelings, LSE and LSC; （3） Human security： unrest, terrorism, democracy, corruption, human development, youth unemployment and employment rate. To alleviate the consequences of radicalization, prevention policies should take in account youth concerns as partners and victims of radicalization. Policies need to focus on radicalization pull and push factors on micro-meso-macro level.展开更多
文摘鲁棒控制方法可用于高压直流附加阻尼控制器的设计,用以抑制交直流系统低频振荡,但目前普遍存在控制器阶数过高的问题,对实用性影响较大。为此提出对H2/H∞鲁棒控制器进行降阶的动态射影控制方法,并对降阶过程中产生的误差进行优化。首先利用总体最小二乘-旋转不变子空间(total least squares-estimation of signal parameters via rotational invariance techniques,TLS-ESPRIT)方法对系统进行低频振荡特性辨识,在此基础上利用主模比指标选择合适的反馈信号;然后利用H2/H∞鲁棒控制理论设计状态反馈鲁棒控制器;最后应用动态射影控制进行降阶,同时利用共轭梯度法对由FH范数评价的误差系统进行优化,得到最优低阶输出反馈控制器。仿真结果表明基于误差最小化射影控制的降阶高压直流鲁棒控制器在不同扰动与故障下都能有效抑制系统的低频振荡,鲁棒性和控制性能强,同时控制器阶数低,适合于实际工程推广应用。
文摘针对含规模化风电接入的交直流电力系统的频率稳定问题,以抑制风电出力大幅度随机扰动引起的频率波动为目的,提出了高压直流输电(high voltage direct current transmission,HVDC)附加频率控制(frequency control,AFC)和自动发电控制(automatic generation control,AGC)配合的辅助频率控制策略。该策略在风电出力发生大幅度随机扰动时,AFC利用HVDC功率快速调制和短时过载能力快速平衡风电出力扰动中变化较快的分量,控制器基于TLS-ESPRIT算法和改进射影控制理论设计,阶数低,易于工程实现;基于传统PI控制的AGC自动跟踪电网功率波动,调整调频机组出力平衡变化较慢的有功功率扰动分量,维持系统有功功率平衡,保持电力系统频率稳定。最后,利用PSCAD/EMTDC在改造的四机两区域模型中进行了仿真分析,结果表明所提策略充分利用了交直流电力系统的频率调节能力,能较好地抑制风电出力引起的频率波动。
文摘The purpose of this study was to examine the impact of macro social factors （states, religion, region, Arab spring, terrorism, unrest （Shoe index）, democracy, corruption （GPI）, Human development （HDI）, low self-control, life stress events （LSE）, youth unemployment, religiosity, feeling （fear and anger）, youth unemployment and total unemployment） on Arab youth＇s radicalization. A sample of 6,730 Arab youth age 15-24 years was selected from Kuwait, UAE, KSA, Oman, Qatar, Bahrain, Jordan, Tunisia, Libya, Morocco, Lebanon, Egypt, Gaza and Palestine and Syrian refuges in Jordan. A questionnaire of 43 items to measure radicalization was developed based on the literature review. A construct validity of the scale was estimated by calculating the correlation between radicalization scale and Low self-control scale and found a positive significant relationship （0.680, a = 0.000）, a sign of validity of the scale. A Reliability of the scale is strong and was estimated by Cronbach＇s alpha and was 0.947. An average of 46.6% of the participants was categorized as radicals with standard deviation of 12. Macro social factors explained 64% of the variance on radicalization. It has a significant impact on radicalization （F = 807.6, a = 0.000）. Each single variable has a significant impact. The analysis revealed three groups of macro determinants of youth radicalization were identified： （1） Geographic factors： state, region, and Arab spring; （2） Social factors： religion, religiously, feelings, LSE and LSC; （3） Human security： unrest, terrorism, democracy, corruption, human development, youth unemployment and employment rate. To alleviate the consequences of radicalization, prevention policies should take in account youth concerns as partners and victims of radicalization. Policies need to focus on radicalization pull and push factors on micro-meso-macro level.
