HVDC与发电机励磁的非线性综合控制策略

提出了一种用于改善交直流混联系统暂态稳定性的非线性控制策略,具体做法是通过建立高压直流输电(HVDC)与发电机组成的综合系统模型,应用最优变目标控制(OVAC)理论推导出了HVDC与发电机励磁的非线性综合控制策略.该控制策略首先驱动系统到达按最大稳定域选择的人工中间稳定平衡点,然后才驱动系统到达期望的稳定平衡点.仿真实验结果表明,该控制策略能够较好地提高交直流互联系统的暂态稳定性.     

DETERMINATION OF COPPER(II) IN NATURAL WATERS BY EXTRACTION USING N-O-VANILLIDINE-2-AMINO-P-CRESOL AND FLAME ATOMIC ABSORPTION SPECTROMETRY

A simple and accurate solvent extraction method was developed for the separation and preconcentration of trace levels of copper(II) in water using N-o-vanillidine-2-amino-p-cresol prior to its determination using flame atomic absorption spectrometry. Analytical parameters such as the pH of the aqueous phase, extraction time, concentration of the reagent, concentration of the nitric acid back extraction agent, volumes of aqueous phase and back extraction agent, and concomitant ions on the extraction yield of the copper(II) were investigated and optimized. Under the optimal conditions, the detection limit (3σ) was 0.61 µ g L^?1 for a 25 mL blank solution, yielding a preconcentration factor of 12.5. The method was succesfully applied to the determination of copper(II) in tap water, river water, and seawater. The accuracy of the method was verified by analyzing two certified reference materials and spiked water samples. The results obtained were in agreement with the certified values and the recoveries for spiked water samples were between 98 and 112%.     

基于最优变目标的HVDC与SVC非线性综合协调控制

直流功率调制能有效地提高交直流系统的稳定性,但同时直流换流站也要消耗大量的无功,影响交流系统的电压稳定。为此,提出了基于最优变目标的HVDC与SVC综合控制策略,通过直流功率调制改善系统稳定性的同时,利用SVC来对直流逆变侧进行无功补偿,使逆变侧电压更具稳定性。首先建立了交直流混合系统中HVDC与SVC的综合控制模型,在此基础上,推导出基于最优变目标的控制理论的HVDC与SVC非线性综合控制策略。仿真结果表明,以该控制策略设计的控制器能有效地提高系统阻尼,改善逆变侧交流母线电压特性。     

基于最优变目标策略的TCSC与励磁系统协调控制

发电机励磁系统以及可控串联电容补偿器(thyristor- controlled series capacitor,TCSC)对远距离输电系统的稳定性影响很大。基于最优变目标控制(optimal variable aim control,OVAC)理论,提出了TCSC与励磁系统协调控制的方法。首先针对含有TCSC的单机无穷大系统的非线性模型,建立了状态空间方程;然后利用最优变目标控制理论推导出了TCSC与励磁系统的协调控制规律;最后利用算例进行了仿真验证。仿真结果表明,该策略提高了系统阻尼,有效地抑制了系统的功率振荡,改善了系统的稳定性。