双馈风电场VSC-HVDC系统接入弱电网的控制研究

由于大型并网风电场有功功率与无功功率的波动导致风电场并网母线及受端弱电网系统的电压和频率不稳定,提出用电压源换流器高压直流输电(VSC-HVDC)的电压与频率控制模型控制风电场并网母线的电压和频率。建立风电场经VSC-HVDC并入大电网的电力系统数学模型,详细设计VSC-HVDC的变流器WFVSC(风电场侧变流器)和GSVSC(电网侧变流器)控制环节,在电压和功率外环及电流内环双环控制的基础上,加入频率控制,以解决电网频率发生改变时,双馈变速风机无法对电网提供频率响应的问题。建立相同条件下高压交流(HVAC)并网的模型进行比较,仿真分析风电场风速波动和风电场出口端三相短路故障两种情况下的并网点(PCC)电压与频率变化,仿真结果验证了该控制模型的正确性和有效性。     

并网风电场穿透功率极限确定方法探讨

确定风力发电场的穿透功率极限是风电场规划和运行的一项重要内容.文章建立了考虑风电机组的叶片、轮毂、齿轮箱和联轴器的异步风力发电机组数学模型;给出了风电场输出功率计算方法;在此基础上,采用频率约束法求取风电场穿透功率极限,指出了频率波动是影响风电场并网运行的主要因素.     

变速双馈风电机组低电压穿越功能仿真

分析了变速恒频双馈风力发电机组的工作原理,建立了包含变频器的双馈风力发电机组动态数学模型,并利用MATLAB/Simulink软件搭建了并网型双馈风力发电机组的仿真模块,通过仿真试验分析了外部电网故障下变速恒频双馈风力发电机组的低电压穿越功能,为变速恒频双馈风力发电机组在大型并网风电场中的应用提供了可靠的理论依据     

基于储能装置的风火打捆直流输电系统稳定性研究

当电网侧发生故障或负荷突变时,大规模风电并网直流输电系统的可靠性和稳定性受到冲击。针对系统的安全、稳定运行,文章提出在受端配置超导储能装置(SMES)的风火打捆经直流输电并网拓扑结构。基于双馈风力发电机组和VSC-HVDC系统设计了SMES的控制策略。受端电网发生短路故障或负荷突变时,超导储能装置能保证电网受到干扰后快速恢复,在向系统补偿无功功率的同时提供一定有功支撑,克服故障带给系统的不利影响。通过DIg SILENT软件仿真结果表明:该方案能够有效控制电源侧和电网侧母线电压和频率,改善并网风电场暂态稳定能力以及故障穿越能力,能更好地保证并网系统可靠、稳定运行。     

双馈风电场有功频率分层控制

风电场有功频率控制是风电场接入电网运行的关键技术。在分析双馈风力发电机组减载运行控制策略及超速法下双馈风力发电机组的减载运行调节能力的基础上,提出了提高双馈风电场的有功调节能力及接入电网后系统频率稳定性的有功频率分层控制策略。该策略根据不同风速区风电机组的减载运行调节能力差异,设计了风电场层分配策略及风电机组层控制策略,在满足有功控制要求的前提下,尽可能提高风电场对电力系统暂态频率稳定的支持。仿真结果表明,该控制策略在系统稳定运行时尽可能存储转子动能,当出现功率扰动后,能够通过快速释放转子存储的动能响应系统频率变化,从而提高了双馈风电场接入电网后的系统频率稳定性。     

大型风力发电机组的软并网控制系统

本文在介绍桨距失速控制风力发电机组控制系统中软并网部分控制要求与控制策略的基础上,给出了大型风力发电机组软并网系统控制的总体设计思路,分析了大型风力发电机组各种并网方式的特点,同时给出了用单片机设计的硬件电路及软件的设计方案。     

双馈风电机组的建模仿真及其等值方法研究

文章分析了双馈风力发电机组的数学模型及控制模型,基于PSCAD/EMTDC平台搭建了双馈风力发电机组仿真模型,以阵风和渐变风为例,对风力发电机组并网运行端口的稳态特性和故障特性进行仿真,其结果实现定子侧有功、无功解耦控制及电压的恒定,验证了所建模型的正确性。在考虑尾流效应的情况下,研究了不同类型的双馈风电机组等值思路,搭建了等值模型,对其等值前后的稳态、暂态特性进行对比分析,结果表明了该等值方法的有效性,为大规模并网型双馈机组风电场进一步研究提供了有利条件。     

基于VSC-HVDC风电并网系统风电场侧故障下系统低电压穿越能力研究

针对经柔性直流输电(VSC-HVDC)并网的风电场,风电场侧故障易造成风机脱网的问题,提出了一种新型无功控制策略。该策略能充分利用故障两侧的无功源,即双馈风力发电机(DFIG)与VSC-HVDC风电场侧变流器(WFSVSC)来提供无功支持,实现低电压穿越。采用DIgSILENT软件进行仿真,仿真结果表明该控制策略能有效减小故障恢复期间的电压波动,缩短故障恢复时间,具有更好的低电压穿越能力。     

清源风电场首台风力机组投运

在河南省三门峡市陕县,大唐三门峡风力发电有限公司清源风电场10号风力发电机组顺利并网发电,成为河南省第1个风力发电项目的首台并网发电机组。这标志着河南省实现了电力发展史上风力发电项目零的突破。     

海上风电多端柔性直流并网系统频率支持研究

针对海上风电多端柔性直流(VSC-MTDC)并网系统,重点研究风电VSC-MTDC对岸上电网调频功能.通过建立详细风电场、换流站和电网模型,提出一种适用于海上风电VSC-MTDC并网系统动态频率调节方法,即改进斜率控制.整个海上风电场VSC-MTDC加入改进斜率控制后,可使有功功率在若干岸上换流站之间合理分配,从而确保...     

南澳海上风电换流站电气接线方案研究

详细介绍了国内首个多端柔性直流工程——广东南澳大型风电场柔性直流输电示范工程,介绍了柔性直流输电的系统接入方案、运行方式,详细阐述了柔性直流换流站的系统结构以及双换流器的拓扑结构,并提出了需要进一步研究的技术方向。     

HVDC Connection of Offshore Wind Farms to the Transmission System

This paper presents a technical and economic analysis to evaluate the benefits and drawbacks of grid connecting offshore wind farms through a dc link. A first case, concerning a 100-MW wind farm, is thoroughly investigated and cases of larger wind farms (200 and 500 MW) are presented. Three different transmission solutions are compared: 150-kV ac, 400-kV ac, and high-voltage dc based on voltage sourced converters (VSC-HVDC). After a brief overview of the features of these connection solutions, the related operational aspects are evaluated. An economic assessment compares the dc connection option to the ac alternatives, taking into account the investment, operation, and maintenance costs, and the negative valorization of losses and energy not supplied. Economic assessment includes sensitivity analyses of parameters, which could impact the 100-MW wind farm: distance, component costs, dc converter reliability, and dc converter losses     

Dynamic modelling and control of fully rated converter wind turbines

Today, many countries are integrating large amount of wind energy into the grid and many more are expected to follow. The expected increase of wind energy integration is therefore a concern particularly to transmission grid operators. Based on the past experience, some of the relevant concerns when connecting significant amount of wind energy into the existing grid are: fault ride through requirement to keep wind turbines on the grid during faults and wind turbines have to provide ancillary services like voltage and frequency control with particular regard to island operation.While there are still a number of wind turbines based on fixed speed induction generators (FSIG) currently running, majority of wind turbines that are planned to be erected are of variable speed configurations. The reason for this is that FSIG are not capable of addressing the concern mentioned above. Thus, existing researches in wind turbines are now widely directed into variable speed configurations. This is because apart from optimum energy capture and reduction of mechanical stress, preference of these types is also due to the fact that it can support the network such as its reactive power and frequency regulation. Variable wind turbines are doubly fed induction generator wind turbines and full converters wind turbines which are based on synchronous or induction generators.This paper describes the steady state and dynamic models and control strategies of wind turbine generators. The dynamic models are presented in the dq frame of reference. Different control strategies in the generator side converter and in the grid side converter for fault ride through requirement and active power/frequency and reactive/voltage control are presented for variable speed wind turbines.     

Co‐ordinated voltage control of DFIG wind turbines in uninterrupted operation during grid faults

Emphasis in this article is on the design of a co‐ordinated voltage control strategy for doubly fed induction generator (DFIG) wind turbines that enhances their capability to provide grid support during grid faults. In contrast to its very good performance in normal operation, the DFIG wind turbine concept is quite sensitive to grid faults and requires special power converter protection. The fault ride‐through and grid support capabilities of the DFIG address therefore primarily the design of DFIG wind turbine control with special focus on power converter protection and voltage control issues. A voltage control strategy is designed and implemented in this article, based on the idea that both converters of the DFIG (i.e. rotor‐side converter and grid‐side converter) participate in the grid voltage control in a co‐ordinated manner. By default the grid voltage is controlled by the rotor‐side converter as long as it is not blocked by the protection system, otherwise the grid‐side converter takes over the voltage control. Moreover, the article presents a DFIG wind farm model equipped with a grid fault protection system and the described co‐ordinated voltage control. The whole DFIG wind farm model is implemented in the power system simulation toolbox PowerFactory DIgSILENT. The DFIG wind farm ride‐through capability and contribution to voltage control in the power system are assessed and discussed by means of simulations with the use of a transmission power system generic model developed and delivered by the Danish Transmission System Operator Energinet.dk. The simulation results show how a DFIG wind farm equipped with voltage control can help a nearby active stall wind farm to ride through a grid fault, without implementation of any additional ride‐through control strategy in the active stall wind farm. Copyright © 2006 John Wiley &Sons, Ltd.     

双馈风力发电用交直交变流器控制策略的研究

概述了变速恒频双馈风力发电用交直交变流器的工作原理,转子侧变流器采用基于最大功率点跟踪的并网发电解耦控制策略,网侧变流器采用基于固定开关频率与电网电动势前馈相结合的双闭环控制策略,构建了110kW变速恒频双馈风力发电模拟平台,经过实验结果分析验证了上述控制策略的有效性和可行性。     

New management structure of active and reactive power of a large wind farm based on multilevel converter

This paper proposes a system of supervision and operation of a new structure wherein a large wind farm is connected to an electrical grid. The farm is managed in such a manner that it can produce the power needed by the grid system. The supervision algorithm is used to distribute the active and reactive power references to the wind turbines proportionally. Based on the aerodynamic power and wind speed of each turbine, the active and reactive power references are produced individually. By using the vector field oriented control, each doubly fed induction generator is controlled through the rotor, which is connected to the two-level pulse width modulation converter. The close loop control is used to provide a constant DC voltage using a five-level neutral point clamped converter. The five-level neutral point clamped converter allows also the adaptation of the voltage level to the electrical grid with better resolution waveform. The analysis of the simulation results shows the effectiveness of the proposed system.     

Multi-pole permanent magnet synchronous generator wind turbines' grid support capability in uninterrupted operation during grid faults

Emphasis in this paper is on the fault ride-through and grid support capabilities of multi-pole permanent magnet synchronous generator (PMSG) wind turbines with a full-scale frequency converter. These wind turbines are announced to be very attractive, especially for large offshore wind farms. A control strategy is presented, which enhances the fault ride-through and voltage support capability of such wind turbines during grid faults. Its design has special focus on power converters' protection and voltage control aspects. The performance of the presented control strategy is assessed and discussed by means of simulations with the use of a transmission power system generic model developed and delivered by the Danish Transmission System Operator Energinet.dk. The simulation results show how a PMSG wind farm equipped with an additional voltage control can help a nearby active stall wind farm to ride through a grid fault, without implementation of any additional ride-through control strategy in the active stall wind farm.     

Efficiency of three wind energy generator systems

This paper presents a method to calculate the average efficiency from the turbine shaft to the grid in wind energy converters. The average efficiency of three 500 kW systems are compared. The systems are: a conventional grid-connected four-pole induction generator equipped with a gear, a variable-speed synchronous generator equipped with a gear and a frequency converter, and a directly driven variable-speed generator equipped with a frequency converter. In this paper it is shown that a variable-speed generator system can be almost as efficient as one for constant speed, although it has much higher losses at rated load. The increased turbine efficiency that variable speed leads to has not been included in this paper. It is also found that a directly driven generator can be more efficient than a conventional four-pole generator equipped with a gear     

并网双馈风电机组低电压穿越能力研究

详细分析了双馈风电机组LVRT功能的实现原理,并在电力系统仿真分析软件PSASP中建立双馈风电机组的LVRT功能模型,采用地理接线图直观地表示风电场外部系统发生短路故障瞬间对风电机组端电压的影响．并以我国某地区电网为例来分析在风电场接入方式不同的情况下系统短路故障对风电机组的影响。根据仿真结果给出风电机组LVRT能力的最低电压限值要求。最后提出了利用串联制动电阻来提高风电机组的LVRT能力的新方法。分析结果表明,串联制动电阻能够可观地提高风电机组的低电压穿越能力。具有较高LVRT能力的风电机组。可以节省一定的投资费用,在一定程度上降低了风电的上网电价。     

Aggregated dynamic model for wind farms with doubly fed induction generator wind turbines

As a result of increasing wind farms penetration in power systems, the wind farms begin to influence power system, and thus the modelling of wind farms has become an interesting research topic. Nowadays, doubly fed induction generator based on wind turbine is the most widely used technology for wind farms due to its main advantages such as high-energy efficiency and controllability, and improved power quality. When the impact of a wind farm on power systems is studied, the behavior of the wind farm at the point common coupling to grid can be represented by an equivalent model derived from the aggregation of wind turbines into an equivalent wind turbine, instead of the complete model including the modelling of all the wind turbines. In this paper, a new equivalent model of wind farms with doubly fed induction generator wind turbines is proposed to represent the collective response of the wind farm by one single equivalent wind turbine, even although the aggregated wind turbines operate receiving different incoming winds. The effectiveness of the equivalent model to represent the collective response of the wind farm is demonstrated by comparing the simulation results of equivalent and complete models both during normal operation and grid disturbances.