双馈风力发电系统低电压穿越的建模与控制

为提高双馈感应风力发电机组并网的运行稳定性,研究电网故障下双馈风电机组的运行特性,使发电机在电网故障时仍能保持不间断的运行。本文主要研究了基于Orowbar保护控制的低电压穿越运行的控制策略,通过Orowbar保护电路来限制电压跌落时转子回路的最大电流,并通过仿真分析了电压跌落的程度和旁路电阻的取值对控制的影响。仿真结果验证了在电网电压骤降下Crowbar保护电路的有效性,可实现双馈风力发电机不间断的运行。     

基于重复控制的风力发电不平衡控制策略

针对风电场电网接入点电压不平衡问题,文章对双馈风力发电机组在不平衡电网条件下的控制策略进行了研究设计,提出了基于内模的重复控制器应用于双馈风力发电机转子变流器的控制。控制器通过对负序电流的有效控制,使得双馈发电机输出定子电流平衡。并通过风场实际应用证明,这种控制方法可以有效控制电网电压负序引起的风力发电机组输出的三相电流不平衡问题。     

双馈感应风力发电机直接转矩控制的研究

本文对变速恒频双馈风力发电机直接转矩控制进行了理论分析,阐述了它的工作原理结构,并对它进行仿真,结果证明双馈感应风力发电机直接转矩控制在风力发电系统中具有利用率高,并网冲击小,并网速度快的优点。     

双馈感应风力发电机直接转矩控制的研究

直接转矩控制技术已经广泛应用于感应发电机的调速控制领域,并已取得良好的控制效果,而双馈风力发电机的直接转矩控制主要工作在低频区域,并且它的低频特性是一个研究热点。文章对变速恒频双馈风力发电机直接转矩控制进行了理论分析,阐述了它的工作原理结构,推导出具体的控制方程,并对它进行仿真,结果证明双馈感应风力发电机直接转矩控制在风力发电系统中具有利用率高,并网冲击小,并网速度快的优点。     

几种双馈式变速恒频风电机组低电压穿越技术对比分析

新电网运行规则要求风力发电机组在电网故障出现电压跌落的情况下不脱网运行,并在故障切除后能尽·陕帮助电力系统恢复稳定运行,要求风电机组具有一定低电压穿越能力。由于双馈感应发电机（DFIG）励磁变换器容量有限,电网故障时会产生转子过电流和变换器直流环节过电压,须实行保护和控制。本文对国内外学术界和工程界对电网故障时双馈感应发电机的保护原理与控制策略进行了大量研究。以便具体设计时根据要求合理选择。     

考虑无功支撑的双馈风机高电压穿越控制策略

本文针对目前HVRT控制策略的不足之处,提出了一种基于双馈感应发电机(DFIG)的HVRT控制策略。分析了电压骤升故障下DFIG的暂态过程,为改善故障后转子过电流,提出了转子侧模拟电感控制策略,修正了等效阻抗值的范围,并设计了一种网侧与转子侧协同无功控制方式,满足了电网故障下无功支持的需求。最后将传统控制策略与本文控制策略进行了仿真对比,证明了该控制策略在提高HVRT性能方面的有效性和优越性。     

我国最大功率风力发电机在北车集团永济厂完工

日前，拥有自主知识产权的国内最大功率1．5MW水冷式双馈风力发电机在北车集团永济电机厂组装完成。这标志着我国企业已具备了自主研发制造国际主流机型双馈发电机的能力。首批2台1．5MW级风力发电机是永济厂为国内某风电主机厂设计制造的。     

变速恒频风力发电用双PWM变换器的协调控制

文章首先分析了双馈风力发电机的原理以及其数学模型,然后分析了变速恒频风力发电技术采用双PWM变换器常规控制策略,在此基础上提出了采用双PWM变换器的协调控制策略。最后利MATLAB/SIMULINK软件对整个风力发电系统进行仿真。结果表明此策略实现了风力发电机的变速恒频运行,另外在定子电流变化的同时,保持了恒定的功率因数,实现了对双馈感应电机的有功功率和无功功率的独立控制。     

电网电压骤降情况下双馈风力发电机低电压穿越技术分析

根据电网规程要求．在电网故障情况下风力发电机组应能保持与电网的连接并向电网不问断供电。文中建立了在电网故障情况下的双馈感应发电机（DFIC）的数学模型,然后分析了实现低电雁穿越（LVRT）的各种改进控制策略和技术方法。     

DSP在风力发电空载并网技术上的应用

针对风力发电机组直接并网和降压并网都会在并网瞬间产生很大的冲击电流。根据变速恒频双馈发电机组的运行特点,通过对其数学模型分析,建立了双馈异步发电机的空载数学模型,研究了基于电网电压定向的空载并网控制的策略,避免了由于定子磁链检测不准确造成的电网冲击。采用TMS320F2812实现了变速恒频双馈风力发电机组空载并网控制系统,给出了硬件和软件设计方案。实验表明系统动态性能强,稳定性好。该控制策略可以实现大容量风电机组的无冲击软并网,是一种理想的风电机组并网方式。     

The meta-stable dip (MSD) effect in SOI FinFETs

The meta-stable dip (MSD) effect is demonstrated and characterized in SOI FinFETs. With ascending scan of front-gate voltage (V_G1), the magnitude of drain current (I_D) tends to be fixed within a specific region of the front-gate voltage and this leads to a dip of transconductance (g_m). The dip width can be modulated through a control of bias condition or measurement speed such as back-gate voltage (V_G2), drain voltage (V_D) and step size of the front-gate voltage. From the dual-gate transient measurement, it is found that the MSD effect is highly dependent on the floating-body effect. In SOI FinFETs, the MSD effect is significantly affected by the fin width due to the fringing electric field of the lateral gates.     

Bit error rate degradation due to a dip in the frequency responseof an equalizing amplifier

This paper describes an analysis of bit error rate (BER) degradation due to a dip in the frequency response of an equalizing amplifier. An equivalent circuit simulation clarifies the BER degradation factors: (1) the output amplitude decrease of a specific binary sequence that has a repetition frequency equal to the dip frequency and (2) the oscillation in output voltage after rise and fall of signal level. A simple model shows that the center frequency and bandwidth of the dip as well as the depth of the dip strongly affect BER. A circuit simulation and experiment show that a dip at around one tenth the data rate causes the worst BER. The dip tolerance of a dc-suppressed transmission code is also discussed     

三相电压暂变主电路拓扑及其检测方法的研究

提出了一种三相电压暂变补偿的主电路拓扑。针对此方案对三相电压暂变进行独立补偿,提出一种单—三相检测方法,通过将各相电压变换,实现了对三相电压的独立检测。给出了检测方法的基本原理,并对其进行了动态性能分析。最后,得出了此检测方法的仿真结果。     

Emission reserve mapping of CRT-type cathodes

The "dip test" was recommended in 1956 to evaluate the emission activity of cathodes, and this method is now in common use for evaluation of cathodes in microwave tubes and in other electron devices wherein unvarying geometry and field configuration permit simple application of the test and interpretation of results. Application of the "dip test" to CRT cathodes, however, involves complexities associated with a) variation of emission current density from center to edge of the cathode, b) variation of the emitting area and current density with intensity modulation (grid voltage), and c) variation of the grid-cathode geometry which takes place during the cooling period of the dip test. A method has now been developed for accurately evaluating the cathode activity for varying radii of concentric circular cathode areas. A figure of merit is introduced which characterizes the cathode emission.     

Envelope-tracking-based Doherty power amplifier

From the instantaneous efficiency plot, it is observed that the conventional 2-stage Doherty power amplifier (DPA) with high upper power dynamic range (>12 dB) suffers from a substantial dip in the middle of the upper power regime, thus reducing the average efficiency. In this study, an envelope-tracking-based DPA is proposed in order to minimise this dip by adjusting the drain bias voltage of the auxiliary amplifier of the DPA proportional to the input power level.     

High power and narrow spectral linewidth 1.5 μm MQW-DFB-LDs withlow FM dip frequency

FM response as well as spectral linewidth were characterized for 1.5 μm multiple-quantum-well distributed feedback laser diodes (MQW-DFB-LDs). It was experimentally demonstrated that the FM dip frequency where AM-FM phase delay rotates by 180° decreases with reduced thermal resistance and reduced threshold current density, due to reduced thermal effect and enhanced carrier effect. 1.5-μm MQW-DFB-LDs have been developed with <20 kHz FM dip frequency and relatively flat FM response, as well as <1 MHz spectral linewidth, in the 10-35 mW light output power range     

An analysis of base bias current effect on SiGe HBTs

The anomalous dip in scattering parameter S/sub 11/ of SiGe heterojunction bipolar transistors (HBTs) is explained quantitatively for the first time. Our results show that for SiGe HBTs, the input impedance can be represented by a "shifted" series RC circuit at low frequencies and a "shifted" parallel RC circuit at high frequencies very accurately. The appearance of the anomalous dip of S/sub 11/ in a Smith chart is caused by this inherent ambivalent characteristic of the input impedance. In addition, it is found that under constant collector-emitter voltage (V/sub CE/), an increase of base current (which corresponds to a decrease of base-emitter resistance (r/sub /spl pi//) and an increase of transconductance (g/sub m/)) enhances the anomalous dip, which can be explained by our proposed theory.     

高功率半导体激光器电压饱和特性与器件质量

为实现对高功率半导体激光器快速,有效、无损的质量检测和可靠性筛选,对器件进行了电导数和光导数测试及分析.结果表明高功率半导体激光器的结电压饱和特性与其质量和可靠性紧密柏关.结电压饱和特性不好的器件一般都存在某种缺陷,结电压饱和特性的差异超出一定范围的同种类器件一定是质量和可靠性差的器件.因此,阈值处电导数曲线的下沉高度h值可作为器件筛选的一个判据.用模拟测馈的方法,对阵列器件和组成它的单元器件的电压饱和特性的相关性进行了研究,阵列器件的电压饱和特性与组成它的单元器件的一致性(均匀性)紧密相关.均匀性小好的器件的电压饱和特性也不好.     

An Improved Control Strategy of Limiting the DC-Link Voltage Fluctuation for a Doubly Fed Induction Wind Generator

The paper presents to develop a new control strategy of limiting the dc-link voltage fluctuation for a back-to-back pulsewidth modulation converter in a doubly fed induction generator (DFIG) for wind turbine systems. The reasons of dc-link voltage fluctuation are analyzed. An improved control strategy with the instantaneous rotor power feedback is proposed to limit the fluctuation range of the dc-link voltage. An experimental rig is set up to valid the proposed strategy, and the dynamic performances of the DFIG are compared with the traditional control method under a constant grid voltage. Furthermore, the capabilities of keeping the dc-link voltage stable are also compared in the ride-through control of DFIG during a three-phase grid fault, by using a developed 2 MW DFIG wind power system model. Both the experimental and simulation results have shown that the proposed control strategy is more effective, and the fluctuation of the dc-link voltage may be successfully limited in a small range under a constant grid voltage and a non-serious grid voltage dip.