Design and Implementation of End to End Encrypted Short Message Service (SMS) Using Hybrid Cipher Algorithm

The study on design and implementation of end to end encrypted Short Message Service (SMS) using hybrid cipher algorithm is motivated by high rate of insecurity of data observed during Short Message Service (SMS) on Mobile devices. SMS messages are one of the popular ways of communication. The aim therefore is to design a software for end to end encryption short message service (SMS) that can conceal message while on transit to another mobile device using Hybrid Cipher Algorithm on Android Operating System and implement it for security of mobile SMS. Hybrid encryption incorporates a combination of asymmetric and symmetric encryption to benefit from the strengths of each form of encryption. Various encryption algorithms have been discussed. Secondary sources were employed in gathering useful data. In this research work three methodologies are employed—Structured System Analysis Design Methodology (SSADM), Object Oriented Analysis Design Methodology (OOADM) and prototyping. With the help of the three cryptographic algorithms employed—Message digest 5 (MD5), Blowfish and Rivest-Shamir Adleman (RSA);integrity, confidentiality, authentication and security of messages were achieved. The messages encrypted by developed application are also resistant to brute force attack. The implementing programs were coded in Java.

模块化多电平变流器IGBT开路故障诊断与定位方法综述

随着模块化多电平变流器(modularmultilevel converter,MMC)在工程领域中广泛应用,绝缘栅双极型晶体管(insulated gate bipolar transistors,IGBT)开路故障问题日益突出,并成为制约其稳定运行的主要因素。IGBT开路故障诊断与定位方法作为及时识别开路故障,保证MMC持续稳定运行的主要手段而被广泛研究。文中首先对MMC的基本结构及IGBT开路故障特征进行介绍和分析,阐明故障子模块电流路径及电容电压变化趋势;其次,以定位故障IGBT使用的方法和手段为依据,对国内外相关主要文献进行分类和归纳,总结不同类型故障诊断方法的优点和不足;最后,对MMC开路故障诊断与定位方法的未来发展方向和趋势进行展望,指出基于硬件、基于模型和基于人工智能的3类诊断方案分别在降低硬件复杂度、提高故障诊断准确率和降低计算量等方面应该重点解决的主要问题和思路。

具备直流短路故障阻断能力的子模块桥臂复用型模块化多电平固态变压器

模块化多电平换流器的固态变压器(modular multilevel converter based solid state transformer,MMC-SST)由于具备多电压等级、多电压形态的端口,在交直流混合配电网中得到广泛关注。传统的输入串联输出并联(inputseriesoutput parallel,ISOP)型MMC-SST具有较高的功率密度,但是在中压直流(medium voltage DC,MVDC)端口短路故障情况下无法持续向低压侧供电;双向有源全桥变换器(dualactive bridge,DAB)型MMC-SST则存在功率密度低、成本高等问题,并且传统的半桥结构的DAB型MMC-SST在MVDC端口短路故障情况下同样无法持续向低压侧供电。文章提出了一种子模块桥臂复用(arm integrated submodule,AISM)型MMC-SST拓扑,在不改变MMC-SST端口电气特性的情况下,在有效减少开关器件数量的同时,还使得SST具备中压直流端口短路故障下的不间断运行能力,进而提升SST的功率密度和供电可靠性。针对文中提出的AISM型MMCSST拓扑,该文还提出了一种针对输入级MMC的混频调制方法,基于共模、差模解耦原理,实现输入级MMC桥臂电压的高频分量和低频分量的解耦。通过理论分析与仿真模拟,验证了所提拓扑及控制方法的可行性。

基于纳什均衡量子粒子群算法的分布式能源系统频率控制方法

含风能、太阳能等可再生能源的分布式能源系统存在频率波动过大和混合储能难以控制的问题。为此,文章提出了一种基于纳什均衡量子粒子群算法(NEQPSO)的分布式能源系统频率控制方法。首先,建立了一种含新能源和混合储能的分布式能源系统模型,并将滑模控制器(SMC)与LADRC观测器的输出共同作用于LADRC的PD控制器,实现滑模线性自抗扰控制器(SM-LADRC)的改进;接着,采用NEQPSO对控制器参数进行优化,以获取最优控制器参数;最后,设置不同情况下的对比验证实验。实验结果表明,优化控制器的控制效果明显优于常规PID和PI控制的;NEQPSO的寻优能力明显优于粒子群算法(PSO)和遗传算法(GA)的;同时,由负荷实验和灵敏度验证实验结果可知,基于NEQPSO滑模线性自抗扰控制的分布式能源系统响应快速、抗扰能力更强、频率效果更好且具有良好的稳态性能。

Research on a Secure Communication Protocol Based on National Secret SM2 Algorithm

Most of the public key algorithms used in the exchange of information for power data transmission protocols are RSA. The core of the key part of this kind of algorithm system has not been announced. For the domestic sensitive information data field, there are threats such as preset backdoors and security vulnerabilities. In response to the above problems, the article introduces a secure communication protocol based on the optimized Secret SM2 algorithm, which uses socket programming to achieve two-way encrypted communication between clients and services, and is able to complete the security protection of data encryption transmission, authentication, data tampering, etc., and proves through experiments that the security protocol is more secure than traditional methods, can effectively identify each other, carry out stable and controllable data encryption transmission, and has good applicability.

稀土Sm掺杂PLA/TiO_2杂化材料的制备及抗凝血性能测定

以乳酸为原料、辛酸亚锡为催化剂制备聚乳酸(PLA);以PLA、Sm、钛酸四正丁酯(TBT)为原料,采用溶胶凝胶法制备稀土Sm掺杂PLA/TiO2有机无机杂化材料。XPS分析结果显示了Sm的加入。动态凝血时间测定法测定结果表明,Sm的掺杂提高了PLA/TiO2的抗凝血能力,并且在加入量为wt0.6%时效果最佳。

SM algorithms-based encryption scheme for large genomic data files

With the rapid development of the genomic sequencing technology,the cost of obtaining personal genomic data and effectively analyzing it has been gradually reduced.The analysis and utilization of genomic dam gradually entered the public view,and the leakage of genomic dam privacy has attracted the attention of researchers.The security of genomic data is not only related to the protection of personal privacy,but also related to the biological information security of the country.However,there is still no.effective genomic dam privacy protection scheme using Shangyong Mima(SM)algorithms.In this paper,we analyze the widely used genomic dam file formats and design a large genomic dam files encryption scheme based on the SM algorithms.Firstly,we design a key agreement protocol based on the SM2 asymmetric cryptography and use the SM3 hash function to guarantee the correctness of the key.Secondly,we used the SM4 symmetric cryptography to encrypt the genomic data by optimizing the packet processing of files,and improve the usability by assisting the computing platform with key management.Software implementation demonstrates that the scheme can be applied to securely transmit the genomic data in the network environment and provide an encryption method based on SM algorithms for protecting the privacy of genomic data.

基于拉依达准则的MMC子模块开路故障定位

模块化多电平换流器(modular multilevel converter,MMC)凭借模块化结构等优点,被广泛应用于高压大功率输电领域。MMC含有大量子模块(submodule,SM),SM的开关器件故障是影响MMC可靠性的关键问题之一。其中SM开路故障不易及时检测,威胁系统正常运行,为此提出一种基于拉依达准则的SM开路故障定位方法。首先,对SM开路故障进行故障特性分析,根据SM开路故障会引起SM电容电压的异常变化,应用拉依达准则进行判别。其次,计算同桥臂内SM电容电压的均值和3倍标准偏差来构造一个置信区间,通过判断SM电容电压是否超出置信区间且持续一定时间来检测并定位发生开路故障的SM。该方法不需要额外传感器,不用建立精确数学模型,不用手动设置经验阈值,算法较为简单。最后,在PSCAD/EMTDC中搭建三相MMC系统仿真,并在实验室搭建单相MMC实验平台对该方法进行验证。仿真和实验结果表明,基于拉依达准则的SM开路故障定位方法能够快速有效地定位出发生开路故障的SM。

AES RSA-SM2 Algorithm against Man-in-the-Middle Attack in IEC 60870-5-104 Protocol

The IEC60870-5-104 protocol lacks an integrated authentication mechanism during plaintext transmission, and is vulnerable to security threats, monitoring, tampering, or cutting off communication connections. In order to verify the security problems of 104 protocol, the 104 master-slave communication implemented DoS attacks, ARP spoofing and Ettercap packet filtering and other man-in-the-middle attacks. DoS attacks may damage the network functions of the 104 communication host, resulting in communication interruption. ARP spoofing damaged the data privacy of the 104 protocol, and Ettercap packet filtering cut off the communication connection between the master and the slave. In order to resist the man-in-the-middle attack, the AES and RSA hybrid encryption signature algorithm and the national secret SM2 elliptic curve algorithm are proposed. AES and RSA hybrid encryption increases the security strength of communication data and realizes identity authentication. The digital signature implemented by the SM2 algorithm can realize identity verification, ensure that the data has not been tampered with, and can ensure the integrity of the data. Both of them improve the communication security of the 104 protocol.

适用于少子模块混合型MMC直流故障穿越的均压调制策略

针对混合型模块化多电平换流器(HMMC)在中低压场景子模块个数受限以及直流故障穿越期间的电容电压平衡问题,提出适用于少子模块HMMC直流故障穿越的调制技术以及直流故障穿越期间的电容电压平衡控制方法。从虚拟半桥子模块角度对全桥子模块拓扑进行解耦,统一HMMC的内部拓扑。基于虚拟调制改进载波移相脉宽调制方法,提出适用于HMMC多工况运行模式切换的混合调制技术。进一步考虑直流故障穿越期间的子模块电容电压平衡需求,基于优化子模块充、放电能量分布的思想,重构脉冲映射关系,提出分层脉冲自适应平衡控制方法。仿真结果表明,所提策略实现了少子模块HMMC直流故障穿越,并有效保障了直流故障穿越过程中子模块的动态电容电压平衡。

LCC-FHMMC混合直流输电系统受端交流系统故障穿越控制策略

送端采用电网换相换流器(LCC)、受端采用全半桥子模块混合型模块化多电平变流器(FHMMC)的LCC-FHMMC混合直流输电系统,当受端交流系统发生故障时,受端交流电压跌落,受端功率传输受阻,盈余的功率导致子模块电容过电压,甚至可能造成设备的严重损坏。为此,提出了一种基于FHMMC直流电压降压运行的受端交流系统故障穿越控制策略,使其直流电压始终低于逆变侧交流母线的电压有效值。同时,整流侧LCC保持常规的定直流电流控制,保证逆变侧的直流电流在额定值附近运行,从而实现了进入直流系统的有功功率与逆变器向受端交流系统输出的有功功率之间的平衡。最后在PSCAD/EMTDC仿真平台上对LCC-FHMMC混合直流输电系统受端交流系统发生的对称故障和不对称故障分别进行了仿真分析,仿真结果验证了所提控制策略能够快速有效地穿越受端交流系统故障,并抑制子模块电容过电压。

基于电容电压波动补偿的混合型模块化多电平变换器

为了降低模块化多电平变换器的电容体积,文中提出一种基于电容电压波动补偿混合子模块的模块化多电平变换器。首先,介绍所提混合型模块化多电平变换器的系统结构与减小电容体积的机理,同时对混合子模块的投切原则进行详细分析;然后,通过分析混合子模块内部不同电容的能量波动,给出所有电容的容值设计方法,并与传统的半桥型模块化多电平变换器进行对比;最后,通过仿真与实验验证了所提方案的有效性。结果表明,文中提出的混合型模块化多电平变换器能够以较低的开关器件成本,大幅度提高电容能量利用率,降低模块化多电平变换器子模块电容的体积,实现系统功率密度的提高。

模块化多电平换流器子模块对地电压分析及其dv/dt抑制方法

模块化多电平换流器在开关过程中,子模块对地电压变化产生的dv/dt对杂散电容充放电形成共模电流,造成严重的传导电磁干扰。文中推导子模块对地电压跳变值与桥臂中子模块位置的关系,分析不同跳变值出现的概率,指出某些位置会出现数倍电容电压(UC)的跳变。为将所有位置子模块的最大对地电压跳变抑制为UC,文中提出一种抑制方法,该方法基于上一控制周期的子模块投切状态、桥臂电流方向、电容电压及当前控制周期需要投入的子模块个数,来确定当前周期的子模块投切状态,并限制两个周期之间子模块投切状态改变的数目为一个或一对,从而达到抑制对地电压跳变的目的。最后通过实验验证子模块对地电压跳变规律及所提方法的有效性。

交直流配电网用模块化变换器模型预测控制

针对交直流配电网模块化变换器IGBT开关状态组合多,计算复杂的问题,提出基于改进的子模块电容电压控制算法.利用MMC相电流、环流和子模块电容电压建立目标函数,根据改进子模块电容电压控制算法,消除了目标函数的权重系数,无需计算所有可能开关状态组合的目标函数,简化了传统MPC控制策略,降低了控制算法的计算复杂性.实例分析证明该方法能够在保证计算精度的同时,有效降低计算量.

Operational Reliability Model of Hybrid MMC Considering Multiple Time Scales and Multi-state Submodule

Environmental and electrical factors such as wind speed,air temperature and switching frequency have significant influences on the operational reliability of hybrid modular multilevel converter(MMC),which is commonly used for the wind power transmission.However,the existing reliability model of hybrid MMC based on statistics cannot accurately reflect the impact of these factors.In this paper,a new operational reliability model of hybrid MMC is presented.The reliability index of the hybrid MMC is coupled with its operation characteristics by calculating multi-term thermal cycling.In addition,an operation strategy of hybrid MMC is proposed to improve its reliability.The multi-state submodule(SM)is developed,which is capable of bypassing specific faulty power modules instead of the whole SM.Case studies show that the proposed operational reliability model could describe the impact of environmental and electrical factors.Also,the proposed operation strategy can improve the reliability of hybrid IMMC by extending the operation time of SMs.

配电网混合型MMC双极短路故障后快速恢复策略

故障清除后模块化多电平换流器(modular multilevel converter,MMC)的快速恢复技术是柔性直流配电技术的重要研究内容。本文针对子模块混合型MMC故障后由于子模块电容电压不均导致的故障恢复过电流问题,提出了一种桥臂过电流抑制策略,避免解锁过程中桥臂子模块过电流的发生,使得解锁过程能够稳定可靠进行;在此基础上,还研究了基于桥臂电流前馈的子模块电容电压快速均衡方法,可促进换流器解锁时桥臂子模块电容电压快速重新稳定至额定值,有利于提高换流器直流侧电压恢复速度;最后,在MATLAB/Simulink环境中搭建了单端混合型MMC仿真模型,验证了所提控制方法的有效性和可行性。

基于半桥子模块的混合式直流耗能装置正弦调制补偿策略

混合式直流耗能装置是用于远海风电经柔性直流送出系统的关键故障穿越设备。为了解决系统盈余功率较大时耗能阀正弦调制电压出现负值,进而导致半桥子模块不再适用的问题,提出了一种耗能阀正弦调制电压的交直流分量补偿策略,在保证调制电压非负性的前提下,通过增大耗能支路电流反向时的子模块电容对外放电功率来弥补子模块电容电压反向放电过程的缺失,通过延长单位周期内耗能电阻消耗最大功率时长来保证其峰值功率受限时平均功率仍能与系统盈余功率相当。分别基于盈余功率模拟系统和海上风电经柔性直流送出系统开展了仿真验证,结果表明正弦调制电压的交直流分量补偿策略可有效限制混合式直流耗能装置的功率器件数量,使基于半桥子模块的混合式直流耗能装置实现全系列盈余功率工况下的功率平衡控制,保证柔性直流系统在受端交流故障下的平稳穿越。

混合型模块化多电平变流器电容优化设计

在基于电压源型换流器的柔性高压直流输电(voltage sourced converter based high voltage direct current,VSC-HVDC)场合,由半桥和全桥子模块构成的混合型模块化多电平变流器(modular multilevel converter,MMC)因具备直流短路故障自清除能力,引起了广泛的研究。而大容量MMC子模块电容的质量、体积大,成本较高,逐渐成为其取得更广泛应用的限制因素。分析并建立了混合型MMC子模块电容电压基频纹波系数与桥臂负电压以及功率因数之间的函数关系。根据该函数,提出一种混合型MMC的参数设计方法使子模块电容最小,在提高MMC功率密度的同时降低了子模块的成本和体积。同时,对比传统的桥臂参考电压始终为正的混合型MMC,在直流电压和桥臂电流有效值相等的情况下,建立了桥臂参考电压存在负电压的混合型MMC的功率传输特性函数,并求出了函数的最优解。最后,通过±160 kV混合型MMC的对比仿真验证了所提设计方法的正确性和有效性。

桥臂交替导通多电平换流器电容电压平衡控制

重点研究了桥臂交替导通多电平换流器(AAMC)的电容电压平衡控制。首先阐述了AAMC的运行特性和工作原理;其次基于子模块充放电的基本原则,提出了适用于AAMC的改进最近电平调制策略,根据桥臂电流方向和子模块电容排序结果确定子模块的投切状态;并通过引入最大电压波动系数优化选择子模块投切时机,降低了开关频率并减少了损耗。在PSCAD/EMTDC中搭建了每桥臂10个子模块的模型,时域仿真结果表明,所提出的平衡控制策略能够满足电容电压均衡。

混合型MMC系统直流故障穿越性能研究

针对半桥子模块(HBSM)、全桥子模块(FBSM)及箝位双子模块(CDSM)这3种子模块混合级联模块化多电平换流器(MMC),首先研究了混合型MMC的直流故障机理,此处提出了混合型MMC具备直流故障穿越的约束条件。然后,基于直流电压为±1 200 V、额定容量为20 kVA的21电平混合型MMC系统试验样机,对混合型MMC系统直流故障穿越特性进行研究。试验结果表明,直流故障发生后,混合型MMC系统通过闭锁换流器以阻断短路故障电流,在直流短路故障期间,交流断路器无跳间,且直流短路故障清除后,换流器在10 ms内重新解锁并恢复至稳定运行。