基于直流保护的直驱风电机组低电压穿越特性分析

研究了基于加装和未加装直流保护的直驱风电机组在电网故障状态下的低电压穿越运行特性。根据GB／T19963--2011对风电机组低电压穿越能力的技术要求,结合直驱风电机组工作原理,构造了直驱风电机组在PSCAD／EMTDC环境下的系统控制模型。以电网三相对称短路故障为案例,对加装和未加装直流保护的直驱风电机组的低电压穿越特性进行了分析和比较。仿真结果不仅证明了所用系统模型是合理的,控制策略是有效可行的,而且还表明加装直流保护的直驱风电机组具备较为优越的低电压穿越特性。     

风电机组的低压穿越改造

摘要：随着风电的快速发展及近年来频繁出现的风机脱网事故,要求并网风电机组具备低电压穿越功能：本文对不同机型的低压穿越技术方案进行分析,阐述风电场低压穿越改造的具体措施。     

含不同风电机组的风电电网仿真研究

为了研究包含恒速异步风力发电机和双馈异步风力发电机的风电场对电网的影响,应用Matlab 7.0建立了含不同风电机组的风电场动态模型。分析了风电场对电网暂态稳定性的影响,风电机组电压恢复情况,有功、无功变化情况,以及不同风电机组的低电压穿越能力。仿真结果表明：双馈异步风力发电机变速平稳、低电压穿越能力较强,有利于优化电能质量;当电网发生故障时,应针对不同的风电机组采取不同的控制策略以提高电力系统稳定性。     

基于转子串联动态电阻的自适应双馈风电机组低电压穿越方案

针对基于转子串联电阻实现双馈风电机组低电压穿越的保护方式,在阻值选择时转子电流的限制效果与故障期间功率可控性之间存在矛盾的问题,通过对转子串电阻保护的理论分析,提出一种结合故障期间自适应选择转子串联电阻阻值和切换转子变换器控制模式的低电压穿越方案,能够实现根据电压跌落深度选择串联阻值且于不同故障区间内自适应切换阻值的串联动态电阻,使整个故障过程中风机处于受控状态,故障穿越更平稳,具有更好的暂态特性。PSCAD仿真结果表明,该方案具有较好的性能。     

双馈风电场群LVRT研究及与低电压保护配合仿真

针对目前缺少研究风电场容量不断扩大和数量日益增多下风电场低电压穿越（LVRT）的问题,以双馈风电场群为例,基于DIgSILENT/PowerFactory软件,采用与电压跌落幅度相关的无功控制策略,研究风电场运行方式、拓扑结构对风机LVRT能力的影响及不同风机对相同点故障的LVRT能力,为考虑LVRT的风电场群输电组网的拓扑优化研究奠定了基础。同时,提出与风电场LVRT要求相配合的分段式低电压保护判据,运用独特的DSL编程语言嵌入风机转子侧保护模块中,实现该保护逻辑和动作功能,最后进行仿真验证。结果证明该保护能很好地满足LVRT的要求。     

基于压力反馈的液压型风机低电压穿越控制方法

结合液压型风力发电机组低电压穿越的控制要求,以实现低电压穿越过程中的功率快速调整为控制目标,提出了一种基于压力控制的低电压穿越控制方法,即在原有低电压穿越控制环的基础上加入压力控制环。通过AMESim和MATLAB/Simulink软件搭建仿真平台进行联合仿真,并依托30kV·A液压型风力发电机组半物理仿真实验平台进行实验验证。结果表明,所提出的控制方法既可实现功率的快速调整,也能有效地抑制并网转速的瞬态冲击。     

风力发电机两种主要机型的对比

双馈异步发电机和直驱型永磁同步发电机是变速恒频发电机组的主要机型。本文从发电成本、低电压穿越能力、可靠性等方面对双馈异步发电机和直驱式永磁同步发电机在风力发电中的应用做了比较,指出直驱式永磁同步发电机在大部分方面都具有较为明显的优势,但是也存在体积偏大的缺点。     

Improved fault ride through capability of DFIG based wind turbines using synchronous reference frame control based dynamic voltage restorer

Fault ride through (FRT) capability in wind turbines to maintain the grid stability during faults has become mandatory with the increasing grid penetration of wind energy. Doubly fed induction generator based wind turbine (DFIG-WT) is the most popularly utilized type of generator but highly susceptible to the voltage disturbances in grid. Dynamic voltage restorer (DVR) based external FRT capability improvement is considered. Since DVR is capable of providing fast voltage sag mitigation during faults and can maintain the nominal operating conditions for DFIG-WT. The effectiveness of the DVR using Synchronous reference frame (SRF) control is investigated for FRT capability in DFIG-WT during both balanced and unbalanced fault conditions. The operation of DVR is confirmed using time-domain simulation in MATLAB/Simulink using 1.5 MW DFIG-WT.     

An effective control solution for doubly-fed induction generator under harsh balanced and unbalanced voltage sags

This paper presents a novel control algorithm for the rotor-side converter of Doubly-Fed Induction Generators. The main goal is to endow the system with effective Low Voltage Ride Through capability, under harsh balanced and unbalanced grid voltage sags, without relying on dedicated auxiliary hardware, which is commonly adopted to sustain severe line faults. In this respect, nonlinear control theory arguments are applied to design a controller capable of mitigating oscillations (particularly on rotor currents and voltages) arising during line faults, therefore preventing the system from disconnecting for protection. The proposed solution adopts both feedforward and feedback terms. The former stems from a thoughtful analysis of the system internal dynamics, taking into account the effects of line voltage perturbations, which is exploited to design feasible state trajectories for the generator electromagnetic variables. Specifically, such references do not contain poorly-damped oscillatory modes of the machine natural dynamics, expressed in synchronously rotating frames (such components turn into slowly varying DC ones in a stationary frames). Then, a state feedback unit is designed according to modern saturated control techniques, accounting for constraints on rotor voltage, and steering real variables toward references, where priority given to rotor currents, to avoid rotor-side converter tripping due to overcurrent. In addition, a non standard line voltage reconstruction and dip detection scheme, based on adaptive state observers, is designed, to reliably cope with challenging faulty conditions. Detailed numerical simulations validate the proposed method benefits under severe symmetric and asymmetric dip scenarios.     

基于DBR的双馈风力机组低电压穿越方案设计

讨论了电网电压跌落下当前双馈风力发电机组各种LVRT技术拓扑方案及控制策略的优缺点,提出一种不同于常用Crowbar技术的低电压穿越技术方案。在基于DBR（Dynamic Brake Resistance）双馈风电机组新型LVRT拓扑结构及功能分析基础上,建立双馈风电机组在电网正常运行和发生低电压故障情况下发电系统的数学模型进行理论分析,提出了风电机组发生LVRT的控制策略。最后在此技术方案下进行20%电网故障下LVRT试验,试验实验数据充分证实了技术方案的正确性。