双馈感应风力发电机实现LVRT控制策略研究

根据最新的风电场接入电网规定,在电网发生故障情况下风力发电机组应能保持与电网的连接。电网电压跌落是电网故障常见的形式之一,所以如何提高双馈感应风力发电机组低电压穿越能力成为了当今风电技术的研究热点。本文根据低电压穿越技术的基本原则,通过改进转子侧的控制策略和增加保护电路的方案来实现低电压穿越技术。通过仿真研究表明,改进的控制策略可以有效的抑制转子侧过电流,能够有效的提高双馈感应风力发电机在故障期间的低电压穿越能力。     

双馈感应风力发电系统新型功率控制策略研究

在风力发电功率优化控制问题的研究中,针对双馈感应风力发电系统稳定性问题,推导出双馈感应发电机转子d-q轴电流分量与定子无功功率及转矩之间的数学表达式,提出以定子无功功率和转矩作为参考输入的控制方法,得出系统功率转换的控制策略,建立了风电系统转子侧变换器的矢量控制框图.采用Matlab/Simulink,搭建了1.5MW风力发电系统的仿真模型.运行仿真模型,得到了双馈感应发电机转子电流,双馈风力发电系统的有功功率、无功功率及三相输出电流等信号的波形曲线.仿真结果表明,改进控制策略提高了系统的鲁棒性和输出电能质量,证明了控制策略的有效性和可行性.     

双馈感应风力发电系统低电压穿越转子侧新型控制方法

建立了增加定子励磁电流变化的双馈感应风力发电系统数学模型,分析了电网电压跌落时以及电压恢复后系统的响应特性.针对电网电压大值跌落的情况,提出了一种低电压穿越控制方案:首先在转子侧变换器定子磁链定向的矢量控制方案中引入一个补偿项——定子励磁电流的微分项;在此基础上,在发电机的转子侧串联电阻.仿真结果表明,该方法在电网电压大值跌落时,能够对定、转子侧的过电压过电流有明显的抑制作用.     

不平衡电网电压下双馈风力发电系统强励控制

针对电网电压不平衡造成的双馈风力发电机(DFIG)定子有功和无功功率振荡、电磁转矩脉动、定、转子电流不平衡等问题,提出了一种双馈风力发电系统转子侧变换器强励控制方案。推导了不平衡电网电压下DFIG定子有功、无功功率的二次谐波分量在同步旋转坐标系中的表达式,并以此为依据设计了电压强励补偿环。分析了有功、无功功率,电磁转矩及定、转子电流二次谐波分量之间的关系,采用单一强励补偿控制器对不同控制目标进行切换强励控制。对1.5MWDFIG系统的控制特性研究验证了所提控制策略的可行性和优越性。     

双馈异步风力发电机功率控制扰动法仿真研究

双馈异步风力发电机有功功率、无功功率的解耦控制是变速恒频风力发电系统的关键技术,也是保证风力发电机组安全高效运行的关键.介绍了交流励磁变速恒频风力发电的基本原理,提出了功率控制扰动策略.利用定子磁链定向的矢量控制方法建立了双馈异步发电机在d-q坐标系下的数学模型,实现了定子有功功率、无功功率的解耦控制.推导了双馈异步发电机的线性化模型并分析了其特件.利用MATLAB/Simulink建立了系统的仿真模型,并就主要扰动参数对系统功率控制性能的影响进行了分析.仿真结果验证了功率控制扰动策略的正确性和可行性,为风力发电技术的进一步研究提供了理论依据.     

基于STATCOM的DFIG风电机组低电压穿越策略研究

双馈异步风力发电机在并网时低电压穿越故障是近年来的研究热点,本文为了解决这个问题,开展了双馈异步风力发电机的无功功率分析和控制策略研究,以pcc点的电压稳定作为控制策略的出发点,通过研究pcc点电压的稳定作为低电压穿越的问题,采用RSC正负电流指令算法来控制,此控制策略在尽可能保证RSC电流上下限的情况下,稳定并网要求。     

新颖的双馈风力发电机灭磁控制策略

电网电压突变会引起双馈发电机输出功率波动和电磁转矩振动。造成这些电磁振荡的根本原因是定子绕组中产生的定子磁链暂态直流分量。本文详细分析了定子磁链暂态分量并推导出定子磁链和转子电流之间的数学表达式,在此基础上提出了一种新颖的双馈风力发电机定子磁链定向矢量控制的灭磁控制方法。仿真结果表明,所提出的灭磁控制方法可以在电网电压跌落程度较轻的情况下有效减小双馈发电机定子磁链中暂态直流分量的影响,提高双馈风电控制系统的稳定性,有利于实现风电机组的低电压穿越。     

双馈系统在电网故障下不间断运行的研究

为更好地研究风力发电机在一定的电网电压跌落故障下的动态响应,以单台1.5 MW双馈风力发电机(DFIG)为研究对象,设计了Crowbar电路,通过构建电网电压跌落仿真模型,分别对机端电压、电流、转子电流、输出的有功功率和无功功率、直流侧电压、电磁转矩在故障期间的动态响应进行了仿真。探讨了相应的控制策略,为进一步研究低电压穿越标准下的控制策略提供了依据,同时也为研制兆瓦级变频器打下基础。测量结果表明这种控制方式能使DFIG在电压跌落故障下实现不间断运行,有效提高了DFIG风电机组运行的可靠性。     

新型双馈风力发电机有功功率平滑控制策略研究

针对由于风能的不确定性、风力发电机的大惯性以及风力发电系统的响应延迟性等造成的风力发电机输出有功功率在一定范围内有波动的问题,提出了一种新型双馈风力发电机有功功率平滑控制策略。该控制策略在全风速范围内采用变浆与变速协调控制策略,并在其基础上增加了一个有功功率误差控制环节,将转子电压辅助控制指令值作为反馈量加入原来的转子电压控制指令值,通过控制SPWM脉冲发生器来实现风力发电机定子输出有功功率的平滑控制。Matlab/Simulink仿真结果表明,与传统有功功率控制策略相比,该新型有功功率平滑控制策略有效抑制了双馈风力发电机输出有功功率的波动。     

基于位置估计的双馈风力发电机的控制策略

为了避免由机械传感器所带来的一些控制上的问题,提出了一种基于位置估计的双馈风力发电机的控制方案。在转速控制阶段,根据双馈发电机数学模型,通过采集电网电压电流,转子电压电流,采用定子磁场定向的矢量控制策略,利用转子电流矢量综合位置与定子电压矢量综合位置,对并网前后转子位置进行估算,得到转速及功率变化规律,运用这个规律可以实现对转速的控制。最后对1 MW的风力机模型进行系统仿真实验,结果表明整个转速控制区间对转子位置的估计都满足系统要求,基本上解决了风力发电机的转速和无功功率控制难的问题,验证了方案的正确性与可行性。     

Determination of fault operation dynamical constraints for the design of wind turbine DFIG drives

This paper presents an efficient design tool for the estimation of the transient electromagnetic peak torque and transient rotor over-voltages of wind turbines (WT) doubly-fed induction generators (DFIG) during severe fault conditions on the grid side. This versatile and robust tool is well adapted to the implementation in a DFIG drives CAD environment using iterative optimization procedures. In such an application, it is used to compute the dynamical constraints function during the integrated design process of the whole drive including the generator, the gearbox and the power converters. Results show that it is necessary to take into account the dynamical constraints under fault operation, during the early steps of the system design process. Another application of the tool is also illustrated in the paper: the design of the protection system (i.e. the crowbar resistance) for a given generator, a given gearbox and a given power converter.     

Intelligent Open Switch Fault Detection for Power Converter in Wind Energy System

This paper proposes a simple and fast fuzzy logic-based open switch fault detection method for rotor side converter (RSC) in doubly fed induction generator (DFIG) wind turbine system. In the proposed scheme, only the mean values of the three-phase rotor currents are used to identify the power switch in which the open-circuit fault has occurred.

The wind energy conversion system model developed for the design and evaluation of the proposed fault detection technique including three principal controls. the first control ensure the regulation of the electromagnetic torque and the reactive stator power (named Rotor Side Converter (RSC) control), the second regulates the DC-link voltage at the desired level (named Grid Side Converter (GSC) control) and in order to achieve maximum power at any wind speed condition a maximum power point tracking (MPPT) control strategy has been used. The simulation model was developed in MATLAB/Simulink environment. The results show that the proposed fault detection scheme is able to rapidly and effectively identify open switch faults among other fault types in a time less than one period.     

理想电网条件下双馈风力发电系统低电压穿越技术的控制策略研究

随着风电在电网所占比例的不断增大,提高风机在故障条件下的不间断运行能力越来越重要。通过分析交流励磁变速恒频双馈风机的运行特点,建立双馈风力发电系统的并网数学模型;针对电网电压小幅对称跌落,在不增加硬件成本的基础上,改进传统双馈发电机矢量控制策略,加入前馈补偿项来抑制电压小幅跌落时转子中的过电流,提高双馈风力发电系统的低压穿越能力。在MATLAB/SIMULINK中验证控制策略的合理性,为以后深入研究双馈风力发电系统提供了基础。     

双馈风力发电机无速度传感器控制研究

间接利用定子、转子电流间的比例关系,分析转子电流和转子位置观测之间的关系,提出了一种基于PQ 功率转子位置观测法的DFIG 矢量控制策略,这种控制策略克服了其他速度观测方式在同步速运行时观测不准的缺陷,具有较宽广的运行范围,能够取得与有速度传感器控制相似的稳态性能。最后构建了DFIG 仿真与实验平台,对所述无位置传感器控制策略进行了仿真与实验验证。仿真结果和试验结果证明了这个控制方法的正确性与有效性。     

A novel control solution for improved trajectory tracking and LVRT performance in DFIG-based wind turbines

This paper presents a new control strategy for the rotor side converter of Doubly-Fed Induction Generator based Wind Turbine systems, under severe voltage dips. The main goal is to fulfill the Low Voltage Ride Through performance, required by modern grid codes. In this respect, the key point is to limit oscillations (particularly on rotor currents) triggered by line faults, so that the system keeps operating with graceful behavior. To this aim, a suitable feedforward-feedback control solution is proposed for the DFIG rotor side. The feedforward part exploits oscillation-free reference trajectories, analytically derived for the system internal dynamics. State feedback, designed accounting for control voltage limits, endows the system with robustness and further tame oscillations during faults. Moreover, improved torque and stator reactive power tracking during faults is achieved, proposing an exact mapping between such quantities and rotor-side currents, which are conventionally used as controlled outputs. Numerical simulations are provided to validate the capability of the proposed approach to effectively cope with harsh faults.     

Intelligent-controlled doubly fed induction generator system using PFNN

An intelligent-controlled doubly fed induction generator (DFIG) system using probabilistic fuzzy neural network (PFNN) is proposed in this study. This system can be applied as a stand-alone power supply system or as the emergency power system when the electricity grid fails for all sub-synchronous, synchronous, and super-synchronous conditions. The rotor side converter is controlled using the field-oriented control to produce three-phase stator voltages with constant magnitude and frequency at different rotor speeds. Moreover, the grid side converter, which is also controlled using field-oriented control, is primarily implemented to maintain the magnitude of the DC-link voltage. Furthermore, an intelligent PFNN controller is proposed for both the rotor and grid side converters to improve the transient and steady-state responses of the DFIG system at different operating conditions. The network structure, online learning algorithm, and convergence analyses of the PFNN are introduced in detail. Finally, the feasibility of the proposed control scheme is verified using some experimental results.     

Intelligent control of doubly‐fed induction generator systems using PIDNNs

An intelligent control for a stand‐alone doubly‐fed induction generator (DFIG) system using a proportional‐integral‐derivative neural network (PIDNN) is proposed in this study. This system can be applied as a stand‐alone power supply system or as the emergency power system when the electricity grid fails for all sub‐synchronous, synchronous, and super‐synchronous conditions. The rotor side converter is controlled using field‐oriented control to produce 3‐phase stator voltages with constant magnitude and frequency at different rotor speeds. Moreover, the grid side converter, which is also controlled using field‐oriented control, is primarily implemented to maintain the magnitude of the DC‐link voltage. Furthermore, the intelligent PIDNN controller is proposed for both the rotor and grid side converters to improve the transient and steady‐state responses of the DFIG system for different operating conditions. Both the network structure and online learning algorithm are introduced in detail. Finally, the feasibility of the proposed control scheme is verified through experimentation. Copyright © 2011 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

不平衡电网电压下双馈感应发电机无源控制

本文以抑制电网电压不平衡所带来的定、转子不平衡电流为目标,提出了一种基于无源化方法的双馈感应发电机不平衡控制策略.首先在分析了正转同步旋转坐标系下的双馈感应发电机正序模型及负序模型无源性的基础上,设计了正、负序模型的无源性状态反馈控制器;然后给出了一种期望状态值计算方法,根据不平衡控制目标得到定、转子电流负序分量的指令值,结合定子电压的正序分量和电磁转矩的期望值计算出定、转子电流正序分量的给定值;最后得到电网电压不平衡条件下双馈感应发电机的无源控制器.仿真结果表明:所提出的控制方案有效地抑制了电网电压不平衡故障时定子及转子的不平衡电流,降低了输出电磁转矩的波动,提高了双馈感应发电机系统在电网电压不平衡条件下实现不间断运行的能力.