基于Encounter的低功耗时钟树综合研究

以基于Cadence CCOPT引擎设计时钟树为例,介绍了以降低时钟树功耗为主要目的,使用门控技术,以及选择合适缓冲器、反相器构建时钟树的方法。通过完成物理设计动态仿真和功耗分析的数据表明,在保证时序收敛的前提下,使用门控技术和选用不同缓冲器、反向器对整个时钟树的功耗及性能影响进行分析。实验结构表明,对使用门控技术芯片的功耗在不同的操作条件下,整个时钟树上的功耗节省约50%;适合使用缓冲器和方向器构建时钟树。同时,在使用达到相同驱动的能力缓冲器和反相器情况下,使用缓冲器的时钟树较使用反相器的时钟树节省30%。     

混合级联逆变器在STATCOM中的应用研究

随着多电平逆变器在电力系统无功功率补偿领域的广泛应用,为了对目前应用的静止同步补偿器（STATCOM）进行改进,提出了将2H桥与3H桥混合级联逆变器作为STATCOM的拓扑,运用EPWM进行调制的解决方案。该方案可以省去庞大笨重的变压器,减小功耗,降低输出谐波含量。文章对基于混合级联逆变器的STATCOM的工作原理进行了分析,在完成理论研究的基础上,利用电力电子仿真软件Simplorer进行了仿真研究,仿真结果表明,混合级联STATCOM具有输出波形质量好、动态响应速度快的优点。     

Time–optimal current control with constant switching frequency for STATCOM

In this paper a time–optimal current control algorithm with constant switching frequency for a STATCOM is presented. The method enables a fast transient response of the device limited only by its output voltage rating. The main idea behind the time–optimal current control is to find such control voltage that enables us to reach current reference values in a pre-determined minimal length of time. This control approach utilizes the mathematical model of the STATCOM and computes the exact required output to move the system state to the reference waveform. The algorithm is tested by means of simulations using the STATCOM mathematical model and a detailed model. The performance of the control algorithm is validated for reference current tracking and balanced and unbalanced network voltage sags. Simulations were carried out in PSCAD.     

一种逆变器死区效应补偿方法

死区效应的存在使得逆变器输出电压和电流无法跟踪参考电压和电流,相位发生变化,增加了谐波分量,使系统的输出转矩存在很大脉动,尤其电机在低速运行时,可能导致系统不稳定。深入分析了死区效应和零电流箝位对输出电流的影响。针对电流过零区域极性判断不准从而导致误补偿的问题,提出在电流过零点设置夹断区间,在夹断区间外采用固定值补偿占空比,在夹断区间内采用线性补偿占空比。仿真及实验结果表明,采用该方法能有效减小电流的畸变和谐波分量。     

Mechanical bending of flexible complementary inverters based on organic and oxide thin film transistors

Flexible complementary inverters composed of p-channel pentacene thin-film transistors (TFTs) and n-channel amorphous indium gallium zinc oxide TFTs were fabricated on polymer substrates. The characteristics of the TFTs and inverters were evaluated at different bending radii. Throughout the bending experiments, the relationship between the performances of the inverters and the characteristics of the TFTs under mechanical deformation was analyzed. The mechanically applied strain led to a change in the voltage transfer characteristics of the complementary inverters, as well as the source–drain saturation current, field-effect mobility and threshold voltage of the TFTs. The switching threshold voltage of the fabricated inverters decreased with decreasing bending radius, which was related to changes in the field-effect mobility and the threshold voltage of the TFTs.     

对多机并联下应用频移式孤岛检测法面临问题的探讨

针对目前广泛应用的频移式孤岛检测方法——简称频移法,指出当只有部分逆变器采用该方法时,其扰动能力可能不足以撼动孤岛的频率并使其超限,从而提出采用频移法的逆变器比例和频移法正反馈增益的调节等2个问题。针对采用频移法的逆变器比例问题,在最不利情况下进行分析,获得了该比例与逆变器最大过载倍数之间的关系,发现逆变器过载能力越大,采用频移法的逆变器比例可越小;关于频移法正反馈增益的调节问题,本文推导出了正反馈增益与采用频移法逆变器比例的关系,表明正反馈增益必须根据采用频移法的逆变器的比例同步增大。仿真结果验证了上述结论。     

Modeling of switching frequency instabilities in buck‐based DC–AC H‐bridge inverters

In this paper, the dynamical behavior of a full bridge DC–AC buck inverter controlled by fixed frequency and PWM is studied. After showing that the system can undergo both period‐doubling and Neimark–Sacker bifurcation at the fast scale (switching period) by using the exact switching model, an exact solution discrete‐time model able to predict both instability phenomena is derived. The model is obtained without making the quasi‐static approximation and it can be used to obtain the useful operation region in the multi‐dimensional design parameter space from time domain simulations in a very fast and accurate manner. Based on the study of the system, some design guidelines are provided. Copyright © 2010 John Wiley & Sons, Ltd.     

新型并联谐振直流环节逆变器控制策略

为了解决传统的硬开关逆变器存在的高du/dt、高di/dt、高开关损耗以及电磁干扰(EMI)问题,提出了一种新型并联谐振直流环节逆变器(PRDCLI)拓扑及其控制策略.该电路的主要优点是结构简单,所有功率器件均工作在零电压或零电流模式,可以实现与各种PWM策略的匹配控制.阐述了其结构组成和工作原理,重点讨论了逆变器和谐...     

一种三相四桥臂逆变器的数学模型分析

在分析三相四桥臂逆变器工作模态的基础上,引入开关状态函数建立了四桥臂逆变器系统离散的、非线性的数学模型.提出应用开关周期平均算子,将离散的系统化成连续的系统,并用小信号扰动法将非线性的系统化成线性系统,建立了从三相四桥臂逆变器控制输入到逆变器输出的传递函数数学模型.并应用PSIM软件对相同参数下元件电路开关模型和传递函...     

自适应滞环电流控制逆变器复合控制策略

针对传统滞环电流控制下双Buck逆变器功率管开关频率不固定导致开关管损耗大、输出电压中的谐波频率范围广的缺点,采用滞环宽度可以根据逆变器电气参数实时调整的自适应滞环电流控制策略,使得开关频率基本保持固定,且滞环宽度按照2倍输出频率余弦变化.同时在电压外环中采用数字PID控制和重复控制相结合的复合控制策略,减小波形失真,...