集群风电基地的电网安全稳定特性与连锁故障防御策略研究

发布时间：2018-07-23 16:57

【摘要】：在论述电网连锁故障研究现状的基础上,分析了双馈异步风电机组(DFIG)的模型和控制机理；基于国网电科院研发的大电网分析软件FASTEST以酒泉风电基地电网为对象,研究了电压、频率的安全稳定影响因素,总结了基地的主要连锁故障模式。基于分层分区的控制思想,以及电网的安全稳定控制体系,设计了风电基地连锁故障防御系统的各层功能,提出了阻断连锁故障的防御策略并通过实例验证了策略的有效性。 1)研究了DFIG的数学模型、有功、无功解耦控制技术、低电压穿越机理与风电场建模。在潮流计算中,当风电场采用恒功率因数控制时,将节点处理为PQ节点；当采用恒电压控制时,节点处理为PV节点(Q为有限值)。 2)研究了风电出力水平、DFIG无功特性(含crowbar保护)和无功补偿设备对风电场并网点的电压稳定影响,结论如下：(1)风电场高有功出力会造成并网点电压偏低(不计无功补偿装置)；(2)电网故障期间,DFIG在磁链衰减后将从电网中吸收无功,加重电网电压的跌落程度,可能造成相邻的风电场群低电压穿越失败或机组crowbar保护连锁动作；(3)并联电容器、SVC在电网正常运行时,能够改善风电基地的电压水平,但是故障清除后瞬间可能产生无功过剩导致关键母线高压越限。 3)分析了不同风电有功出力比例与风电机组的频率保护定值对风电基地电网频率稳定性的影响。结论如下：(1)风电有功功率占总出力比例越大,风电基地的频率稳定性越差、故障时频率恶化的越快；(2)风电机组的频率保护定值不当可能恶化电网故障期间的功率失衡,引发安控连锁动作。 4)总结了集群风电基地连锁故障的主要演化模式：(1)因风电基地电压问题导致风电机组低压高压脱网；(2)风电基地外送通道故障引起功率不平衡而导致机组因频率保护连锁故障；(3)故障后因潮流转移引起风电外送通道过载,导致电网侧连锁故障,进而引发风电基地侧电压或频率问题,导致风机连锁跳闸。 5)基于分层分区的控制思想和电网的安全稳定系统体系,设计了风电基地连锁故障防御系统的各层功能,研究了风电基地连锁故障控制的时机与可用措施,提出了在线、离线一体化与预防控制、紧急控制、校正控制相结合的防御策略,考虑研究的稳定影响因素调节控制解决电压、频率、过载等多种问题引起的风电基地连锁故障。通过对连锁故障实例的仿真验证,证明了该策略有效。
[Abstract]:On the basis of discussing the current situation of power network cascading fault research, this paper analyzes the model and control mechanism of doubly-fed asynchronous wind turbine (DFIG), and studies the voltage based on the large power network analysis software FASTEST, which is developed by the National Institute of electricity and Power Technology, and takes Jiuquan wind power base as the object. Frequency of safety and stability factors, summed up the base of the main cascading fault mode. Based on the control idea of stratification and partition and the safety and stability control system of power network, the functions of each layer of cascading fault defense system of wind power base are designed. The defense strategy of blocking cascading faults is put forward and the effectiveness of the strategy is verified by examples. 1) the mathematical model, active and reactive power decoupling control technology, low voltage traversing mechanism and wind farm modeling of DFIG are studied. In power flow calculation, when the wind farm adopts constant power factor control, the node is treated as PQ node, and when the constant voltage control is used, The node is treated as PV node (Q is finite value). 2) the effects of reactive power characteristics (including crowbar protection) and reactive power compensation equipment on voltage stability of wind farm are studied. The conclusions are as follows: (1) the high active power output of wind farm will result in the low voltage of parallel network (excluding the reactive power compensator); (2). During the fault period, the reactive power will be absorbed from the power network after the flux attenuation, and the drop degree of the voltage will be aggravated. It may cause low voltage traversing failure of adjacent wind farm groups or cascading action of unit crowbar protection. (3) shunt capacitor can improve the voltage level of wind power base when the power grid is in normal operation. However, the reactive power surplus may occur immediately after the fault clearing, which leads to the high voltage overrun of the key bus. 3) the influence of the ratio of active power output of wind power and the fixed value of frequency protection of wind turbine on the frequency stability of wind power base network is analyzed. The conclusions are as follows: (1) the greater the proportion of active power to the total output power, the worse the frequency stability of wind power base, and the faster the frequency deterioration during the failure; (2) the improper frequency protection of wind turbine units may aggravate the power imbalance during the fault period of power grid. The main evolution modes of cascading faults in cluster wind power base are summarized as follows: (1) the voltage problem of wind power base leads to the low-voltage and high-voltage decoupling of wind turbine units; (2) the power imbalance caused by the outputting channel fault of the wind power base leads to the cascading fault of frequency protection for the unit; (3) after the fault, the wind power supply channel overloads due to the power flow transfer, which results in the cascading fault on the power grid side. Thus causing voltage or frequency problems in wind power base, leading to cascading tripping of fan. 5) based on the control idea of stratification and partition and the system of safety and stability of power network, the functions of cascading fault defense system of wind power base are designed. This paper studies the timing and available measures of cascading fault control in wind power base, and puts forward a defense strategy combining on-line, off-line integration and preventive control, emergency control and correction control, and adjusts the control solution voltage considering the studied stability influence factors. Frequency, overload and other problems caused by wind power base cascading failures. The simulation results show that the strategy is effective.
【学位授予单位】：南京理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM711

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