Design and statistical analysis of low power and high speed 10T static random access memory cell

Static random access memory (SRAM)-based cache memory is an essential part of electronic devices. As the technology node reduces, the power loss and stability has become the major problems. Several SRAM cells had been developed to address the stability and power loss problem. But still, it is a challenge to achieve balance performance among all the parameters of the SRAM cell for sub-nanometer technology. This paper proposes a novel SRAM cell, which is having comparatively less total, static power loss, less delay, and high stability compared with the conventional cells for 45-nm complementary metal-oxide-semiconductor (CMOS) technology. The total power cost of the proposed 10T cell has been reduced by 90.3%, 85.84%, 51.02%, and 90.9% compared with 6T, N-controlled (NC), 10T sub, and 10T, respectively. Similarly, the static power cost of the proposed cell has been reduced by 55.17%, 5.72%, -41.6%, and 52.9% compared with 6T, NC, 10T-sub, and 10T, respectively. The proposed cell provides better stability, less delay, and comparable area compared with other considered 10T cells. Finally, the Monte Carlo (MC) simulation and process analysis of SRAM cells validate the efficiency of the proposed 10T cell.     

基于改进动态阻抗法的电网静态电压稳定裕度快速评估

戴维南等效参数准确辨识是实现电网静态稳定在线评估的关键。采用两个时刻潮流的辨识方法很难保证两时刻之间等效参数不变的假设条件。首先分析了现有等效参数辨识方法存在的问题,提出了一种基于动态等效阻抗的改进等效参数辨识方法,利用当前运行点和预估点在线快速计算等效参数。改进方法解决了负荷功率恒定和多节点负荷功率同时变化时原方法失效的问题。在此基础上,利用阻抗模指标对电网静态稳定裕度进行评估。最后,通过仿真验证了所提方法的有效性。     

Charge‐sharing read port with bitline pre‐charging and sensing scheme for low‐power SRAMs

In this paper, we present our decoupled differential read (DDR) port and bitline (BL) pre‐charging scheme. The proposed scheme allows the charge sharing between bitlines during the read operation. DDR port isolates the internal nodes, thus improves the read static noise margin and allows the subthreshold operation. BLs are not pre‐charged to full V_DD. Read port is designed such that for the read ‘1’ operation, BL shares its charge with BLB, and for read ‘0’ operation, BL is charged toward V_DD and BLB is discharged to the ground. The proposed non‐V_DD BL pre‐charging and the charge‐sharing mechanism provide substantial read power savings. Virtual power rail is used to suppress the BL leakages. A dynamic voltage level shifting pre‐amplifier is used that shifts both BLs to the middle voltage and amplifies the voltage difference. Single‐ended write driver is also presented that only conditionally charges the write BL. The proposed 10‐transistor static random access memory cell using DDR provides more than 2 times read static noise margin, ~72% read power savings, and ~40% write power savings compared with the conventional six‐transistor static random access memory. Copyright © 2016 John Wiley & Sons, Ltd.     

One-sided 10T static-random access memory cell for energy-efficient and noise-immune internet of things applications

This paper presents a one-sided 10-transistors static-random access memory (SRAM) cell appropriate for the internet of things (IoT) applications in which energy-efficient SRAM cells are necessary to raise the battery lifetime. The bit-cell core of the proposed SRAM cell is composed of two inverters with different structures based on the gate-wrap-around (GWA) carbon nanotube (CNT)-gate-diffusion input (GDI) technique and only one-bit line to perform both read and write operations to minimize active power consumption. The proposed bit-cell uses a transmission gate network and write-assist schemes to significantly improve the write-ability and stack read-decoupling technique to enhance hold-/read-stability. Moreover, a memory mini-array has been implemented using the proposed cell along with all the principal circuitries. Extensive Monte Carlo (MC) simulations show that write/hold/read static noise margins (SNMs) are improved by about 1.252, 1.196, and 1.152 times, respectively. Also, the results of evaluating the write- and read-yield parameters for the proposed SRAM bit-cell are about 22% and 13% better than counterpart bit-cell designs, respectively. In addition, the bit error rate (BER) and energy dissipation parameters for the proposed memory cell are almost 61% and seven times higher than the studied SRAM bit-cell in the same simulation process. Finally, to evaluate the effectiveness of the proposed SRAM bit-cell in the real-world application, a memory array architecture with an online (or off-chip) adaptive power supply voltage based on a hardware algorithm for storing digital images at a minimum energy dissipation is proposed. Our simulation results emphasize that the proposed memory array can be a good candidate for energy-efficient and noise-immunity IoT platforms.     

基于改进随机森林算法的电力业务实时流量分类方法

为了更有效地对电力业务系统安全接入过程中日渐增多的流量进行实时分类,提高电力系统的业务处理速度,提出了一种基于改进随机森林算法的电力业务实时流量分类方法。在分析电力业务安全接入实时流量特征的基础上,改进传统随机森林算法,基于分类间隔加权对随机森林进行修剪来提高分类实时性;对新的样本数据进行数据剪辑来提高分类的准确性。在此改进算法的基础上设计了电力业务安全接入实时流量分类流程。最后以某省电力公司安全接入实时流量分类为例,验证了所提方法的准确性和实时性。     

基于PSS/E的大电网静态电压稳定裕度计算

阐述了一种基于电力系统仿真软件PSS/E求解静态电压稳定裕度的方法。该法通过PSS/E提供的函数模块,采用内嵌的PYTHON语言进行编程。由于包含了对3绕组变压器和潮流初值回存的处理语句,使其能应用于大规模电网静态电压稳定裕度的求解。几个IEEE标准算例和一个大型电网静态电压稳定裕度的求解验证了所提方法的有效性和可行性。     

高压直流输电系统功率/电压静态稳定性的建模与分析

高压直流输电系统功率/电压静态稳定性与所连接的交流系统的强弱及其所采用的控制方式密切相关.阐述了用于分析直流输电系统功率/电压静态稳定性的系统小信号模型及分析方法,对不同控制下系统静态稳定指标进行了分析,结论表明,弱交流系统的功率稳定性与电压稳定性都较差,随着SCR的逐渐增大,都将有所改善;逆变器采用定直流电压控制比采用定熄弧角控制时系统的功率稳定性与电压稳定性要好.     

一种用于含风电场电力系统电压稳定概率分析的混合方法

为了进行风电并网后电力系统电压稳定性的评估,利用具有概率特征的负荷裕度指标,提出了一种含风电场电力系统电压稳定概率分析的混合方法。当系统随机参数扰动量很小时将系统简化为线性化模型,根据线性方程的叠加性原理,在计算负荷裕度关于随机参数的灵敏度矩阵的基础上运用叠加性原理并结合正态分布的特性,将系统负荷裕度在期望值附近的随机扰动分解为单独考虑负荷随机变化和风速随机变化两种情况下求得的负荷裕度扰动量之和。该方法与Monte Carlo法和半不变量法同时在IEEE-30节点系统上进行仿真计算,通过对比分析表明了本文方法在保证准确性的基础上节省了计算时间。     

A directional control method for interface flow considering static voltage stability

A directional control method (DCM) for power flows on a set of interface lines between two regions of power system considering static voltage stability margin is developed in this paper. A surface approximation approach is firstly used to obtain the relationship between the interface flow solution and the generation direction of generator (the portion of generation variation in each participating generator to satisfy the desired power increase on the interface and the system loss). Then, an optimization model is built to determine the optimum dispatching scheme of generators. This method not only can control the total power on the interface to satisfy the power demand but also can realize the directional control of power on each interface line based on the needs of operation. The proposed DCM is further extended to determine the optimum dispatching scheme of generators for maximizing the interface flow margin (IFM), which is the active power margin of the key transmission lines between two regions of power system constrained by static voltage stability. A modified continuation power flow (MCPF) is used to show and evaluate the impacts of the DCM on the IFM. The New England 39-bus system and the IEEE 300-bus system have been employed to verify the effectiveness of the DCM.     

考虑新能源发电不确定性的静态电压稳定故障筛选与排序方法

为了有效地分析电力系统设备故障和新能源发电不确定性对系统静态电压稳定的影响,提出了一种考虑新能源发电不确定性的静态电压稳定故障筛选与排序方法。假设各新能源发电出力为均值,建立N-1故障场景下确定性的电压稳定临界点模型,根据所得的故障后负荷裕度筛选得到严重故障集。考虑风电和光伏发电的随机分布,建立故障场景下的电压稳定概率评估模型,采用随机响应面法求解获得故障场景的负荷裕度累积概率分布。根据负荷裕度累积概率分布,设计了2种故障后系统电压稳定性的排序指标,确定严重故障集的排序。IEEE 118节点标准系统的计算结果表明,所提故障筛选与排序方法是有效的,可以甄别和排序各故障场景下系统的概率静态电压稳定性;根据故障排序结果构建的电力系统概率电压稳定域有助于对概率稳定边界的分析和研究。     

分布式光伏电站接入低压配电网系统暂态电压稳定性研究

运用Matlab SPS建立了分布式光伏电站接入0.4 kV低压配电网的典型系统仿真模型。运用时域仿真法考察了光伏电站接入配电网的电缆线路在发生短路、闪络以及断线故障时对光伏电站出口母线暂态电压稳定性的影响。当电缆线路发生短路和断线故障时,光伏电站出口母线会发生电压幅值不断增大的电压失稳现象。而当电缆线路发生闪络故障时,投入重合闸可使光伏电站出口母线电压快速恢复。当光照强度发生大幅度突降时,光伏电站出口母线电压幅值会发生跌落,电压跌落程度主要取决于正常运行时光伏有功出力的大小。一般而言,当光伏出力为数十kW及以下时,光强突降并不会导致光伏电站出口母线电压发生失稳或崩溃。     

综合灵敏度和静态电压稳定裕度的直流受端交流系统电压薄弱区域评估方法

提出综合无功-电压灵敏度与静态电压稳定裕度的直流受端交流系统电压薄弱区域评估方法,并在灵敏度及静态电压稳定计算中计及了负荷静态电压特性。以计及负荷静态电压特性的交直流电力系统潮流方程为基础,计算交流节点电压相对于直流落点无功功率的灵敏度;基于连续潮流法,计算计及负荷静态电压特性的直流受端交流系统静态电压稳定裕度,综合这2个指标识别电压薄弱区域。并进一步地比较了不同ZIP负荷占比、不同直流控制方式对直流落点近区交流系统电压薄弱区域评估的影响。     

单相分布式发电接入台区电网的谐波补偿控制

非线性负荷不断增加导致台区电网的谐波问题愈加严峻,而越来越多分布式发电(DG)接入在实现新能源就地并网的同时,也为台区电网的谐波治理提供了一个有效途径。以含单相DG的台区电网为对象,考虑三相不对称负荷的接线方式差异,提出了一种利用单相DG的分相谐波补偿控制策略。首先对含单相DG的台区电网接线方式和典型台区谐波源负荷情况进行分析,将不对称负荷等值成星形有中性线、星形无中性线和三角形接线方式,分别讨论了台区电网的谐波电流分布,进而推导了单台和两台单相DG接入时的谐波电流补偿函数。据此,采用基于延时环节和同步坐标变换的谐波电流检测方法,提取各相负荷电流和线路电流的谐波分量,建立不同接线方式下单相DG的谐波补偿控制方案。最后,利用Matlab/Simulink验证了所提的分相谐波补偿控制对台区电网谐波的治理效果。     

A subthreshold current‐sensing ΣΔ modulator for low‐voltage and low‐power sensor interfaces

A continuous‐time (CT) ΣΔ modulator for sensing and direct analog‐to‐digital conversion of nA‐range (subthreshold) currents is presented in this work. The presented modulator uses a subthreshold technique based on subthreshold source‐coupled logic cells to efficiently convert subthreshold current to digital code without performing current‐to‐voltage conversion. As a benefit of this technique, the current‐sensing CT ΣΔ modulator operates at low voltage and consumes very low power, which makes it convenient for low‐power and low‐voltage current‐mode sensor interfaces. The prototype design is implemented in a 0.18 µm standard complementary metal‐oxide semiconductor technology. The modulator operates with a supply voltage of 0.8 V and consumes 5.43 μW of power at the maximum bandwidth of 20 kHz. The obtainable current‐sensing resolution ranges from effective number of bits (ENOB) = 7.1 bits at a 5 kHz bandwidth to ENOB = 6.5 bits at a 20 kHz bandwidth (ENOB). The obtained power efficiency (peak FoM = 1.5 pJ/conv) outperforms existing current‐mode analog‐to‐digital converter designs and is comparable with the voltage‐mode CT ΣΔ modulators. The modulator generates very low levels of switching noise thanks to CT operation and subthreshold current‐mode circuits that draw a constant subthreshold current from the voltage supply. The presented modulator is used as a readout interface for sensors with current‐mode output in ultra low‐power conditions and is also suitable to perform on‐chip current measurements in power management circuits. Copyright © 2014 John Wiley & Sons, Ltd.     

分布式发电接入电网的静态电压稳定特性及影响分析

分布式发电(Distributed Generation,DG)接入电网在缓解环境污染和能源短缺压力的同时,也会给电网的安全运行分析带来新的挑战,特别是DG控制策略的多样性将使电网静态电压稳定问题更加复杂。DG接入电网对静态电压稳定性的影响主要取决于DG的接入容量、控制方式等因素。首先对DG接入线路的复杂外部网络进行等值,推导负荷节点电压与分布式发电渗透率的解析表达式。在此基础上,分析不同DG渗透率下的节点电压以及负荷PV特性,比较DG采用不同无功控制策略对负荷PV特性的影响。最后,将扩展线路电压稳定指标应用于含DG的电网静态电压稳定分析,研究DG采用主动无功控制策略对线路电压稳定指标的影响。     

基于连续潮流法及内点法的交直流负荷裕度算法

基于连续潮流法和原始-对偶内点法,提出了一种新的分段求解交直流系统负荷裕度方法。首先根据直流系统的调节特性,运用连续潮流法计算初始运行点到直流控制方式调整点系统的负荷增量。然后基于交直流网络间的耦合关系,推导得到交直流系统的Jacob i、Hessian矩阵,进而运用原始-对偶内点法求解直流控制方式改变后交直流系统的负荷裕度。该方法具有较好的收敛性,且能方便考虑直流量的约束和控制方式调整的问题,并经算例仿真验证该方法的准确性和快速收敛性。     

一种新的电力系统稳定控制策略表表述及存储方式

通过对策略表的科学分析,提出了一种新的策略表表述和存储方法,该方法将安全稳定控制策略表分解为接线方式、潮流方式、故障信息、保护动作信息及控制策略五种基本策略元素,每一种策略元素均用一逻辑表达式表述,并将各策略元素间的关系用树表示,即以树状结构形式存放控制策略表。这种方法所生成的控制策略表不仅存储容量小、通用性强、易于修改,最重要的是易于实现通用的策略表查寻程序,从而保证了能够快速、准确、可靠地实现策略查寻。     

Comparative performance analysis and complementary triode based CMFB circuits for fully differential class AB symmetrical OTAs with low power consumption

In this paper we extend the figures of merit for class AB symmetrical OTAs to the fully differential case and compare topologies from the literature. This analysis shows that the power consumption of the CMFB can have a significant role in determining the efficiency of the OTA, but on the other hand a CMFB is needed both to set the desired output common mode voltage and to improve the CMRR. We propose the complementary triode CMFB, i.e. a triode CMFB applied both at the NMOS and PMOS current mirrors, as suitable for class AB symmetrical OTAs, and show some case studies in deep submicron CMOS technology to assess the effectiveness of the proposed solution. Copyright © 2015 John Wiley & Sons, Ltd.     

Dynamic modeling and control of the tidal current turbine using DFIG and DDPMSG for power system stability analysis

This paper describes the overall dynamic models of tidal current turbine driving either a doubly fed induction generator (DFIG) or a direct drive permanent magnet synchronous generator (DDPMSG) connected to a single machine infinite bus system including controllers to improve system stability. Testing with ranges of controller gains is carried out to establish zones of stability. The overall results show the advantages of using the DDPMSG over the DFIG. In this paper we used two different models for each machine; the full model and the reduced order model. Also IEEE-9 bus system is used in this work for multi-machine system and tested for a small signal stability analysis.     

一种基于节点聚合的区域联络线潮流调整方法

在线安全稳定分析数据由本地状态估计数据和上级下发的其他调度机构数据拼接构成,由于两者时间不同步造成区域联络线功率出现偏差。文中提出了一种内外网数据拼接的区域联络线潮流调整方法,在将联络线聚合成联络通道以及将对联络通道灵敏度较大的若干节点聚合的基础上,通过求解聚合节点调整量和联络通道潮流偏差量的线性方程组获得调整量,避免采用优化方法时计算速度慢和部分节点调整量过大的问题;当方程组病态时,通过求解极小范数最小二乘解避免线性方程组无解的问题。该方法可以满足在线安全稳定分析计算速度和准确性要求,且某实际电网的算例验证了该方法的有效性。