寻找失落的遗传密码：历史风貌核心区空间修复性设计研究——天津市解放北路街区改造示例

随着越来越多的历史街区及建筑遭受到日益严重的破坏，如何有效地对这些街区进行保护，提出可操作性强的控制指标，已经成为历史街区保护所面临的新课题。本文以天津市解放北路历史风貌核心区为便，采用数理统计和参考控制相结合的方式，探求一种新的研究方法，期望通过这种研究方法寻找量化的参数、准确而又清晰地对这些街区风貌进行控制。     

The effect of copper and protein on iron metabolism in rats fed a cereal diet

Weanling male white rats were fed a diet containing a commercially available breakfast cereal. In 28 days they developed a mild anemia coupled with an increased amount of iron in the liver. In parallel work, this same diet was supplemented in a factorial fashion with casein, iron, copper and zinc. The zinc had no effect. Copper supplementation increased the hemoglobin level. Casein decreased liver iron. The copper and casein, when fed together, produced results approaching normal control levels. Supplementation of the diet with additional iron did not increase the hemoglobin or hematocrit but it did further increase iron storage in the liver. It is suggested that cereal enrichment programs might do well to consider copper and protein rather than focus total attention on additional iron and zinc.     

基于广义二阶积分器的表贴式永磁同步电机低速转子位置检测方法

在基于脉振高频电流注入的表贴式永磁同步电机无位置传感器控制中,常采用高阶滤波器来调制信号以抑制阶跃信号带来的误差。该文提出一种基于广义二阶积分器的新型转子位置观测器,由两个广义二阶积分器串联构成。前级实现高频信号提取功能,后级用于误差幅值获取。该结构有效减小了信号处理产生的延时,减轻了运算负担;同时在位置观测器中引入微分前馈控制,明显降低了动态过程中阶跃信号对位置观测器的影响;最后基于RT-LAB控制器对上述方法进行了实验,结果表明所提观测器改善了系统的控制性能。     

考虑磁饱和的感应电机MTPA转矩控制

感应电机的最大转矩电流比(MTPA)控制算法根据需求转矩调节磁链幅值,以达到转矩与定子电流比值的最大化。因磁链随转矩的变化而变化,不再像传统控制算法保持磁场幅值恒定,磁场非线性饱和效应会对控制系统产生影响。针对此问题,该文提出考虑磁饱和特性的MTPA转矩控制系统。根据需求转矩以及饱和模型,通过线性搜索寻找最优磁链目标值,并在计算励磁电流时考虑d轴转子电流的动态特性,用降阶观测器观测转子磁链,并在设计滑模磁链控制器以及反步法设计转矩控制器时考虑观测误差,以确保控制器参数的设置能达到全局稳定。仿真和实验结果证明了所设计控制器的有效性。     

永磁同步电机无位置传感器控制技术研究综述

永磁同步电机具有功率密度高、转矩惯量比大、动态响应速度快的优点,在大功率交流传动领域具有明显的优势。对永磁同步电机的高性能控制依赖于精确的转子位置信息,然而通常使用的光电编码器和旋转变压器等机械式位置传感器成本高、体积大、抗干扰能力差,限制了永磁同步电机的推广应用,无位置传感器控制技术是解决这一问题的重要途径。本文对永磁同步电机的无位置传感器控制技术进行了综述,从转子初始位置检测、低速与零速运行控制、中高速运行控制和全转速范围运行控制四个方面对永磁同步电机无位置传感器控制技术进行了深入阐述和对比分析。最后,对永磁同步电机无位置传感器控制技术的发展趋势进行了展望。     

电网电压不平衡时逆变器无交流电压传感器控制策略

针对非理想电网电压条件,研究一种适应电网电压不平衡情况的并网逆变器无交流电压传感器控制策略。首先基于二阶广义积分器构建正交滤波器及适合电网电压不平衡条件的三相并网逆变器电压观测器,在两相静止坐标系下对电网电压进行观测;然后基于正交滤波器输出量进行正、负序分离,使正、负序分离与电网电压观测同步进行;最后结合逆变器在两相静止坐标系下的PR控制,并采用负序补偿算法,实现逆变器在电网电压不平衡条件下的无交流电压传感器控制。该策略能够避免传统虚拟磁链观测中的积分饱和、初值敏感、静态误差等问题,并克服现有基于正交滤波器的逆变器无交流电压传感器控制无法适应电网电压不平衡情况的问题。通过仿真与实验验证了所提出策略的有效性。     

A Solid State Transformer model for power flow calculations

This paper presents the implementation of a Solid State Transformer (SST) model in OpenDSS. The goal is to develop a SST model that could be useful for assessing the impact that the replacement of the conventional iron-and-copper transformer with the SST can have on the distribution system performance. Test distribution systems of different characteristics and size have been simulated during different time periods. The simulations have been carried out assuming voltage-dependent loads and considering that power flow through either the HV/MV substation transformer or any of the MV/LV distribution transformers can be bidirectional. Simulation results prove that a positive impact should be expected on voltages at both MV and LV levels, but the efficiency of current SST designs should be improved.     

永磁同步电机变频调速系统的内模控制

永磁同步电机是典型的非线性多变量强耦合系统,在同步旋转坐标系下dq轴电流存在耦合,传统的PI控制器无法实现解耦,提出一种基于内模控制原理和空间矢量算法相结合的高性能永磁同步电机解耦控制方法,用内模控制策略控制理想电机模型,对定子电流交叉耦合电势动态解耦,提高系统的动态响应性能,同时在整个电流闭环过程中对参数摄动和外扰动具有良好的鲁棒性,这种方法不需要额外的电机参数和检测硬件,实验结果验证了方法有效可行。     

基于观察者模式的气象卫星数据接收与预处理调度机制研究

针对多颗气象卫星数据在国内外地面站兼容接收及统一自动批量预处理的业务需求,基于观察者模式,设计了系统总体架构,构建了数据接收任务、质量文件传输、预处理与分发作业运行调度机制,实现了有效协同各种资源,对气象卫星多个有效载荷观测数据进行同步自动批量接收、传输、预处理与分发。经过实践检验,该机制简化了设计,降低了耦合度,增强了系统健壮性,满足业务调度的灵活性、可靠性、时效性要求,同时监视界面直观明了,可操作性强,为气象与气候领域的科学研究提供了持续有效的海量数据支撑。     

Mismatched disturbance attenuation control for static var compensator with uncertain parameters

The use of a static var compensator (SVC) as a component of flexible alternating current transmission system (FACTS) devices to control power systems has been investigated for decades. Its aim is to regulate the system voltage and improve the stability and loadability of power systems. A typical assumption in such a system is that the parameters of the controlled system are known accurately, which is rarely satisfied in practice. This paper explores the development of a simple but effective controller for a single-machine infinite-bus power system with SVC subjected to both matched and mismatched disturbances where the controller derivation is based on the assumption that all parameters used in the system modeling are unknown, but bounded in size. The research in this paper illustrates how an indirect robust control can be incorporated with a modified disturbance observer-based feedforward term to attenuate the influence of parameter variations and disturbances from the outputs of the system. Simulation results are presented to confirm the effectiveness of the proposed scheme.