Inverter Power Stage Connected with PV-Grid

This paper focuses on the design of the inverter power stage connected with PV-grid which supports the contrived PV system. The increased number of grid connected photovoltaic (PV) inverters gave rise to problems concerning the stability and safety of the utility grid, as well as power quality issues. The proposed systems can overcome these issues and improve standard regulation methods for gird connected PV inverter. The maximum available voltage in the PV string is tracked by the power stage which has been planned and designed in such a way. The tracked voltage is boosted then. The important components to voltage source inverter (VSI) are boost inductor and input capacitor which are calculated. To get a clear sinusoidal output phase voltage of 230 V from a DC capacitance bus projected to deal with 400 V, the important inverter stage parameters have been planned and modeled in Mat lab. Each block stage of the converter is easily understandable by the Simlink of the dual stage DC-AC converter explanation. The control schemes which have been proposed would compromise with the inverter power stage which forms the neat grid system. The existing renewable energy sources in the laboratory are integrated by the proposed control.

Period-doubling bifurcation in two-stage power factor correction converters using the method of incremental harmonic balance and Floquet theory

In this paper, period-doubling bifurcation in a two-stage power factor correction converter is analyzed by using the method of incremental harmonic balance （IHB） and Floquet theory. A two-stage power factor correction converter typically employs a cascade configuration of a pre-regulator boost power factor correction converter with average current mode control to achieve a near unity power factor and a tightly regulated post-regulator DC-DC Buck converter with voltage feedback control to regulate the output voltage. Based on the assumption that the tightly regulated postregulator DC-DC Buck converter is represented as a constant power sink and some other assumptions, the simplified model of the two-stage power factor correction converter is derived and its approximate periodic solution is calculated by the method of IHB. And then, the stability of the system is investigated by using Floquet theory and the stable boundaries are presented on the selected parameter spaces. Finally, some experimental results are given to confirm the effectiveness of the theoretical analysis.

Discussion on the Regional Division of the Development Stage of China's Wind Power

This paper constructs the index system of the regional division of the development stage of China's wind power resources,including the index of energy,the index of wind energy endowments and other indices.Based on principal component analysis and layered clustering analysis of these indices,and combined with the conceptual function of the development and utilization stage of the wind power,this paper divides the development and utilization stage of the wind power into four stages taking province as the basic yardstick:optimization growth stage,the rapid growth stage,the slow growth stage and the initial growth stage.In addition,this paper briefly discusses the basic strategy that should be adopted in each development stage of wind power resources.

Contribution to the Optimization of the Transient Stability of an Electric Power Transmission Network Using a Universal Power Flow Compensator Controlled by a Three-Stage Inverter

The use of an electrical network as close as possible to its limits can lead to its instability in the event of a high amplitude disturbance. The damping of system oscillations can be achieved by conventional means of voltage and speed regulation but also by FACTS (Flexible AC Transmission Systems) devices, which are increasingly used in power networks. In this work, optimal control coordination between a hybrid power flow controller and a three-level inverter was used to improve the transient stability of a transmission line. The UPFC is a combination of a serial compensator (SSSC) and a parallel compensator (STATCOM) both connected to a DC-LINK DC bus. The SSSC acts as a voltage source for the network and injects a voltage that can be adjusted in phase and amplitude in addition to the network voltage;the STATCOM acts as a current source. The approach used is tested in the Matlab Simulink environment on a single machine network. Optimal controller tuning gives a better transient stability improvement by reducing the transport angle oscillations from 248.17% to 9.85%.

Isolated single stage high power factor AC/DC converter

The problem of harmonic pollution has brought wide attention with the increase of power customers. The adoption of the technology of active power factor correction (APFC) with advanced high frequency power converter is a more efficient solution to the problem of harmonic pollution. A single stage isolated high power factor AC/DC converter, which features wide range DC output, high power factor, lower harmonic pollution in input current, and phase shift PWM full bridge circuit can achieve soft switching. The principle of the circuit topology and the reasons of voltage surges across the power switch are analyzed. Experiment results illustrate that this circuit has the advantages of high power factor and lower harmonic distortion.

Controlling the output power of soft switching arc welding inverter by two-stage continuous PWM method

The full bridge zero voltage zero current switching （ FB-ZVZCS ） , which could adjust the output power by keeping the duty ratio of lagging leg constant and changing the duty ratio of leading leg, was a common circuit of soft switching arc welding inverter power source. However, when the duty ratio of leading leg was reduced to zero, the output power stayed the constant value instead of becoming zero. The working status and waveforms of some major parameters were studied in this paper while the duty ratio of leading leg was zero. It was concluded that the minimum output power of soft switching inverter was related to the charging voltage of paraUel capacitors, and the output power also could be reduced by reducing the duty ratio of lagging leg. A novel two-stage continuous PWM control method that could switch working-mode between full bridge and half bridge was put forward in this paper. This kind of control method could further reduce the output power of soft switching inverter in order to meet the requirement of low heat input of sheet metal welding.

<i>A Brief Review</i>: Stage-Convertible Power Amplifier Using Differential Line Inductor

In this review article, a stage-convertible RF power amplifier designed with a 0.18-μm RF CMOS process is described. A method to implement a low-power matching network is an essential technology for the stage-convertible power amplifier. Various low-power matching networks with distributed active transformers as an output power combiner are compared in terms of the amounts of undesired coupling, the chip size, and the amount of power loss. The feasibility of a differential line inductor for the stage-convertible power amplifier is assessed and explained. Finally, we show that the differential line inductor is a realistic means of reducing the overall chip size, enhancing the quality factor of the matching network, and minimizing the undesired coupling between the inter-stage matching network and any output matching network. Additionally, the operating mechanism of the stage-convertible power amplifier using the differential line inductor for a low-power matching network is described in detail.

REMOTE SENSING APPLICATION RESEARCH OF WATER POWER AT THE INITIAL EXPLOITING STAGE IN THE LOWER REACHES OF YALONG RIVER

There are abundant water power resources in the Yalong River which are suitable for the large hydroelectric engineering. But a reliability study should be made for the valley which liable to frequent earthquakes. The color infrared aerophotos, multi-spectral photography and thermal infrared scanning had been specially done besides MSS image, processing. Researches on remote sensing applications to engineering geology, hydrogeology, deformation of neo-tectonics, Iandslide, mud-rock flow, ecological environment and geographical information system had been carried out by more than 20 research units.

Ultra-Low Power Pipeline Structure Exploiting Noncritical Stage with Circuit-Level Timing Speculation

With the increase of the clock frequency and silicon integration, power aware computing has become a critical concern in the design of the embedded processor and system-on-chip （SoC）. Dynamic voltage scaling （DVS） is an effective method for low-power designs. However, traditional DVS methods have two deficiencies. First, they have a conservative safety margin which is not necessary for most of the time. Second, they are exclusively concerned with the critical stage and ignore the significant potential free slack time of the noncritical stage. These factors lead to a large amount of power waste. In this paper, a novel pipeline structure with ultra-low power consumption is proposed. It cuts off the safety margin and takes use of the noncritical stages at the same time. A prototype pipeline is designed in 0.13 μm technology and analyzed. The result shows that a large amount of energy can be saved by using this structure. Compared with the fixed voltage case, 50% of the energy can be saved, and with respect to the traditional adaptive voltage scaling design, 37.8% of the energy can be saved.

Optimizing the Stage Resolution of a 10-Bit, 50 Ms/Sec Pipelined A/D Converter &Its Impact on Speed, Power, Area, and Linearity

At high speeds and high resolution, the Pipeline ADCs are becoming popular. The options of different stage resolutions in Pipelined ADCs and their effect on speed, power dissipation, linearity and area are discussed in this paper. The basic building blocks viz. Op-Amp Sample and Hold circuit, sub converter, D/A Converter and residue amplifier used in every stage is assumed to be identical. The sub converters are implemented using flash architectures. The paper implements a 10-bit 50 Mega Samples/Sec Pipelined A/D Converter using 1, 1.5, 2, 3, 4 and 5 bits/stage conversion techniques and discusses about its impact on speed, power, area, and linearity. The design implementation uses 0.18 μm CMOS technology and a 3.3 V power supply. The paper concludes stating that a resolution of 2 bits/stage is optimum for a Pipelined ADC and to reduce the design complexity, we may go up to 3 bits/stage.

New Stage of the Northwest China 330 kV Power System Development - A Brief Introduction of System Planning in Northwest China to the Year 2000

The system planning of the Northwest China 330 kV Power System from present to the year 2000 is introduced in this paper. Some technical problems arising from the system planning, such as network configuration, system stability and reactive power compensation etc. are also briefly summarized.

俄制核电末级叶片围带磨损原因分析及间隙修复

采用试验手段和有限元方法对某核电汽轮机末级叶片围带磨损原因进行了分析,并基于叶片围带在不同间隙下的安全性和经济性分析,确定了叶片安全运行时的围带间隙范围,给出了叶片围带间隙的修复方法和实施工艺流程,为后续末级叶片检修提供了重要的理论依据。

考虑风电不确定性的交直流混联电网受端系统恢复决策优化方法

随着风电渗透率的不断提高,恢复方案受接入风电不确定性的影响越来越大。对含高压直流馈入的受端系统,恢复期间高压直流输电(high-voltage direct current,HVDC)的启动及运行对交流系统的网架结构及功率调度方案均有较高要求。为最大限度地利用HVDC的支援功率加速系统恢复进程,在对HVDC馈入的受端系统进行恢复决策时考虑风电不确定性的影响具有十分重要的意义。为此,该文提出HVDC馈入下考虑风电不确定性的受端系统恢复决策方法。首先,基于非全维凸包不确定集详细刻画风电极端场景;其次,考虑风电不确定性及HVDC的启动及运行特性建立两阶段鲁棒恢复模型;然后,通过伴随网络法将HVDC的启动及运行特性进行线性化处理;之后,采用列与约束生成算法求解所构建的优化模型。最后,通过新英格兰10机39节点算例及我国西南某省实际算例验证所提方法的有效性与实用性。

基于时序运行模拟的水火风光储互补系统电源优化配置

系统时序运行模拟是水火风光储互补系统电源规模优化配置的关键环节。对于水火风光储多能互补系统8760逐小时运行模拟,按照小时尺度构建的模型规模很大,直接求解困难。本文提出按时间尺度逐层分解、递进优化的高效求解算法,精确模拟系统全年逐小时调度运行过程。在此基础上,构建双层规划模型对由风电、光伏、水电、火电、抽水蓄能、梯级水电站混合式抽水蓄能和电化学储能等电源组成的并网多能互补系统的电源容量进行优化配置。将模型应用在青海省电网系统中,对风电、光伏、抽水蓄能电站和基于水电站的可逆机组容量进行优化,得到电源最佳配置方案。

考虑富氧燃烧碳捕集技术和源荷双侧响应的综合能源系统优化调度

为降低燃气轮机的碳排放水平和提高灵活性,提出了计及富氧燃烧碳捕集技术和源荷双侧响应的综合能源系统低碳经济优化策略。首先,研究了富氧燃烧技术的运行原理及其能流特性,并构建空分制氧设备和碳捕集设备的耦合模型;其次,引入可调的热电比作为供给侧响应策略,需求侧对于电力、热能以及气负荷的特性进行综合权衡,借助能源价格的引导,并考虑其相互之间的可替代属性形成需求侧响应机制;最后,通过计及气负荷碳排放的阶梯式碳交易约束碳排放,以系统运行成本为目标优化各时段机组出力。设置多场景进行仿真分析,结果表明富氧燃烧碳捕集技术能够有效减少系统的碳排放量,源荷双侧响应能够灵活调节供给侧与需求侧的供能关系,并有效减少系统运行成本。

基于EWT的分布式光储PCC功率波动自适应平抑方法

分布式光伏在交流侧公共连接点(point of common coupling,PCC)汇流的功率有较大的随机性与波动性,影响电网的稳定运行。为此,提出了基于经验小波变换(empirical wavelet transform,EWT)的分布式光储PCC功率自适应平抑方法。首先,针对混合储能(hybrid energy storage system,HESS)与分布式光伏接入PCC的典型场景,在分析EWT自适应处理波形的特点后,结合功率波动率与储能元件的响应特性,对PCC的光伏原始汇流功率进行EWT分解与优化修正,实现HESS的功率初级分配。之后为避免HESS的荷电状态(state of charge,SOC)频繁越限,提出了一种主动功率补偿的SOC控制策略,通过主动改变储能的参考信号使其SOC在安全范围内工作。结合实际数据的仿真验证表明,该平抑方法能够自适应地实现光伏出力的合理分解与功率分配,在延长储能使用寿命的同时有效满足并网功率波动的要求,为平抑光伏输出功率波动提供了新思路。

一种具有超宽输入功率范围的三路整流电路

本文提出一种具有超宽输入功率范围的三路整流电路.通过在三条整流支路中采用不同阈值电压的二极管,使每条支路对不同输入功率进行高效整流,三条整流支路协同作用,使所提出的整流电路能够在超宽输入功率范围内保持高效率工作;设计并实现了一个工作在2.4 GHz的三支路整流电路,三条整流支路分别实现在-10~11、11~24和24~35 dBm的功率范围内,效率保持在30%以上.测试结果表明:在-6~25 dBm的输入功率范围内,电路的转换效率均可保持在40%以上,最高效率可以达到71.2%.所提出的整流电路对输入功率的灵敏度较低,能够在超宽输入功率范围内实现高效率能量转换,可用于能量收集或动态无线能量传输系统中.

航空三级式发电系统非线性建模与硬件在环实现

针对航空三级式发电系统在故障诊断与状态监控研究中进展缓慢的问题,对系统的非线性关系和信号传递逻辑进行了研究,建立了发电系统的非线性模型,构建了硬件在环测试平台。首先利用电流-磁链神经网络,拟合了电机电流-磁链的非线性关系;其次提出变参数平均值模型的改进型,准确预测了旋转整流器的输出电压降;最后分析了系统的信号传递逻辑,完成了对系统的非线性建模。结合航空三级式发电系统的非线性模型和RT-LAB实时仿真机完成了硬件在环测试平台的构建,并利用GJB 181B—2012标准对平台进行了有效性验证和控制能力的验证。验证结果表明,在小型单发飞机所需的发电系统输出功率为45 kV·A的条件下,平台输出三相交流电的稳态电压为113.0174 V、电压不平衡度为0.2532 V、电压调制幅度为2.0596 V,满足GJB 181B—2012标准对供电品质的要求,并且还可以在30~50 kV·A内跟踪任意指定输出功率。该平台利用非线性建模技术、硬件在环技术打破了传统航空发电系统研究中对于实验环境的要求,可以降低研究成本、缩短研究周期,对于航空发电系统的控制器研究以及航空发电系统的更新换代具有加速功能。

有源缓冲型逆变器功率解耦技术研究

为实现单级单相升压逆变并能有效抑制直流侧二次纹波电流,提出一种带有源缓冲的电流型逆变器电路拓扑,研究该逆变器的6种电路模态并提出其两模态调制策略和三模态调制策略,设计2种调制策略下的模型预测控制策略,提供主电路参数设计准则。从储能电感电流的最大脉动量与二次纹波含量两方面对2种调制策略进行对比分析,得出了三模态调制策略具有更好纹波抑制效果的结论。对2种调制策略下的逆变器进行仿真分析,仿真结果表明,三模态调制下电路的输出电压总谐波失真率、电感电流相对脉动量与二倍频含量均低于两模态调制下的数据。设计并搭建500VA 48VDC/220V50HzAC有源缓冲型单级单相升压逆变器实验装置,给出了三模态调制下基于模型预测控制的逆变器实验波形,进一步证实了所提研究方案在实现单级升压逆变的同时具有二次纹波抑制能力。

考虑台风时空特性的海上风电场群协同紧急防御策略

极端天气发生率逐年升高,威胁电网安全稳定运行。为解决极端天气历史数据抽样建模存在局限性、极端天气预测不准确和电网应对自然灾害防御吸收能力不足等问题,提出一种考虑台风时空特性的海上风电场群协同紧急防御策略。首先,基于Batts梯度风模型分析台风时空特性与影响机理,量化台风物理信息与海上风电场出力间的耦合关系。然后,以偏差考核区间内的紧急防御成本最小为目标函数,提出了考虑台风时空特性的海上风电集群多时间尺度两阶段随机优化模型。模型第一阶段基于台风预报信息定制出包含常规机组备用出力、抽蓄机组启停计划、储能电站出力、计划弃风/切负荷量的防御资源预调度策略,第二阶段将台风预报的不确定性纳入决策过程中,基于灵活分布式资源制定紧急防御调整策略。最后,通过算例验证了所提紧急防御策略的有效性与经济性。