Signal flow graph modelling of interleaved buck converters

This paper presents a systematic development of unified signal flow graph model for an interleaved buck converter system operating in continuous inductor current mode. From this signal flow graph small, large‐signal and steady‐state models are developed, which are useful to study the converter dynamic and steady‐state behaviour. Converter performance expressions like steady‐state voltage gain, efficiency expressions and other small‐signal characteristic transfer functions are derived. Development of unified signal flow graph is explained for a 3‐cell interleaved converter system. Derivation of large, small‐signal and steady‐state models from the unified signal flow graph is demonstrated by considering a 2‐cell interleaved buck converter system. Large signal model was programmed in TUTSIM simulator, and the large‐signal responses against supply, load disturbances were predicted. Signal flow graph analysis results are validated with PSIM simulations. Further, the mathematical models obtained from the signal flow graph modelling are in agreement with those obtained from the state‐space averaging technique. Copyright © 2003 John Wiley & Sons, Ltd.     

Unified power flow controller based on two shunt converters and a series capacitor

In this paper a novel configuration of unified power flow controller (UPFC) which consists of two shunt converters and a series capacitor is proposed. In this configuration, a series capacitor is used between two shunt converters to inject desired series voltage. As a result, it is possible to control the active and reactive power flow as same as the conventional configuration of UPFC. The main advantage of the proposed UPFC in comparison with the conventional configuration is injection of a series voltage waveform with a very low total harmonic distortion (THD). Also, using two shunt converters instead of a series and a shunt converters, results in reduction of design efforts and simplification of control, measuring and protection strategies. An optimal control strategy based on the discrete model of converters is applied to shunt converters. The proposed UPFC is simulated using PSCAD/EMTDC and MATLAB software and simulation results are presented to validate the effectiveness of the novel configuration of UPFC. Also, the experimental results which are obtained from an experimental set-up are presented.     

Auxiliary bridge arm–based switching control for optimal unloading transient performance of multiphase buck converters

For a low-conversion ratio buck converter, the step-down (unloading) transient lasts much longer than the step-up transient for the same change of the load. Regarding this issue, an auxiliary bridge arm (ABA) multiphase buck converter with switching control scheme is proposed for the optimal unloading transient performance. With the ABA, the input voltage is reversely connected into the inductor current freewheeling loop during the unloading transient. In this case, the fall slew rate of the inductor current increases, because of the voltage across the inductor increase. Meanwhile, the capacitor-charge balance theory is used to calculate the switching moment and achieve the minimum settling time and the voltage overshoots. Finally, a 12- to 3.3-V two-phase synchronous buck converter prototype is built. The experimental results show that the settling time and the voltage deviation are both improved over 50% compared with that of the average current sharing scheme and the time-optimal control scheme.     

信号流图在配电网潮流计算中的应用

为了解决采用传统方法进行配电网潮流计算所面临的实际困难,提出了基于流图理论求解线性方程的配电网潮流计算新方法,避免了繁琐的矩阵运算,提高了计算精度,克服了传统算法不适用的配电网特殊环境带来的影响,且该方法不存在计算的收敛性问题及其多解问题,避免了传统的潮流方法的纯“数值计算”所带来的各种误差。     

Global hybrid modeling and control of a buck converter: A novel concept

Several attempts have been made to design suitable controllers for DC–DC converters. However, these designs suffer from model inaccuracy or their inability to desirably function in both continuous and discontinuous current modes. This paper presents a novel switching scheme based on hybrid modeling to control a buck converter using mixed logical dynamical (MLD) methodologies. The proposed method is capable of globally controlling the converter in both continuous and discontinuous current modes of operation by considering all constraints in the physical plant such as maximum inductor current and capacitor voltage limits. Different loads and input voltage disturbances are simulated in MATLAB and results are presented to demonstrate the suitability of the controller. The transient and steady‐state performance of the closed‐loop control over a wide range of operating points shows satisfactory operation of the proposed controller. Copyright © 2008 John Wiley & Sons, Ltd.     

基于图论网络流算法的新能源跨区域交易路径输电定价策略

针对新能源跨区域消纳中存在的关键节点辨识、最大输送额度评估、输电成本归集与分摊问题,提出了一种基于图论网络流算法的跨区域交易路径输电定价策略。首先,通过构建特高压网络的拓扑结构简化图模型,对简化图的网络连通度、系统关键节点的易损性进行分析。其次,在简化图中设定与交易路径中售电、购电方对应的源、汇点,采用Edmond-Karp算法对源、汇点间的增广路径进行搜索,对交易路径的最大输送额度实现有效的快速评估。最后,以社会福利最大化为优化目标,对多个可行交易路径中的不同流量进行优化配置。采用基于图论的输电成本分摊方法对青海至湖南的新能源跨区域交易路径进行了算例分析,与现行交易路径的输电成本进行了对比分析,验证了所提交易路径输电定价策略的有效性与优越性。     

基于二阶锥优化的交直流系统多目标最优潮流研究

为解决广域大范围内新能源的并网和消纳问题,柔性直流电网技术得到了快速的发展,已经发展成为了直流环网的形式.直流环网具有多条冗余线路,能更好更灵活地调度各发电单元和线路之间传输的功率.针对柔性直流电网的特点,提出一种基于二阶锥优化和超效率数据包络分析法的交直流互联系统最优潮流计算方法.基于含VSC-HVDC的交直流系统稳...     

基于潮流控制器的同相牵引供电系统方案研究

文章提出了以大容量潮流控制器为中心,结合斯科特变压器构成同相牵引供电系统。该系统不仅能传递有功功率、补偿无功功率及谐波,还可以取消电分相。大容量潮流控制器由四重化的三电平电压源换流器组成,具有拓扑结构简单,提供容量大等优点。