含双馈机组的风电系统网损优化与动态潮流研究

发布时间：2018-08-12 20:13

【摘要】：风电并网影响系统经济性和安全性。为提高风电系统经济性,有必要量化分析并网风电对网损的影响。考虑双馈感应风电机组(Double-Fed Induction Generator,DFIG)内部损耗时,受风速变化影响的机组有功出力在潮流求解前未知,传统网损灵敏度模型不能直接反应风速波动的影响,无法直接用于含DFIG的风电系统。同时随着风电并网容量增加,需要风电机组参与系统调频以维持频率安全性。动态潮流算法将功率扰动分担给调频机组,可量化系统频率,在稳态分析中常用于计算功率扰动后系统潮流分布与频率偏移。现有动态潮流文献针对同步机组,未考虑风电机组参与系统调频。针对上述问题,本文基于DFIG详细潮流模型,对含DFIG风电系统的网损优化和动态潮流算法进行了研究,论文主要内容和创新点如下:(1)基于最大功率点跟踪方式,扩展传统网损灵敏度模型,提出系统有功网损对风速灵敏度,以量化风速对有功网损的影响程度和趋势。算例结果表明负的灵敏度指标反映系统有功网损随风速上升而减小,反之随风速上升而增大;灵敏度指标绝对值越大,风速对有功网损影响越明显。所提灵敏度指标可作为风电机组无功控制方式和风电场并网位置选择的辅助参考依据。(2)引入DFIG内部约束,基于DFIG具体调频策略在动态潮流计算中修正其相关参数,使其参与系统一次调频;量化DFIG机组惯性使其参与加速功率分担,提出考虑DFIG参与系统一次调频的动态潮流模型。结合算例发现DFIG惯性受风速和减载水平影响;系统加速功率为负时,在相同减载水平下,输入风速越高,DFIG机组有功备用越大,对系统频率支持能力越强。(3)现有经济调度研究虽有涉及系统频率和SG调频能力,但忽略风电或以风电功率代替具体风电机组。为在经济调度中考虑DFIG的一次调频能力,将上节所述考虑DFIG参与调频的动态潮流算法引入经济调度,提出计及DFIG参与一次调频的概率最优潮流模型。模型计及风速预测误差概率特性,通过权重系数在优化目标中引入预测误差引起的频率偏移。结合算例验证了所提模型的有效性,发现通过选择适合的目标函数权重系数,可兼顾发电成本和预测误差引起的频率偏移,以获得较好的经济性和安全性。
[Abstract]:Wind power grid connection affects system economy and safety. In order to improve the economy of wind power system, it is necessary to quantitatively analyze the influence of grid-connected wind power on network loss. Considering the internal loss of Double-Fed Induction induction wind turbine (Double-Fed Induction generator), the active power output of the unit affected by the wind speed change is unknown before the power flow is solved, and the traditional network loss sensitivity model can not directly reflect the influence of wind speed fluctuation. Cannot be directly used in wind power systems with DFIG. At the same time, with the increase of wind power grid capacity, wind turbines are required to participate in frequency regulation to maintain frequency safety. The dynamic power flow algorithm shares the power disturbance to the frequency modulation unit and quantifies the frequency of the system. It is often used to calculate the power flow distribution and frequency offset of the system after the power disturbance in the steady-state analysis. The existing dynamic power flow literature is aimed at synchronous units and does not consider the wind turbine participating in the frequency modulation of the system. Aiming at the above problems, based on the detailed power flow model of DFIG, this paper studies the power loss optimization and dynamic power flow algorithm of wind power system with DFIG. The main contents and innovations of this paper are as follows: (1) based on the maximum power point tracking method, Based on the traditional sensitivity model of network loss, the sensitivity of active power network loss to wind speed is proposed to quantify the influence degree and trend of wind speed on active power network loss. The results show that the negative sensitivity index reflects that the active power network loss decreases with the increase of the wind speed, whereas increases with the increase of the wind speed, and the greater the absolute value of the sensitivity index, the more obvious the influence of the wind speed on the loss of the active power network. The proposed sensitivity index can be used as an auxiliary reference for wind turbine reactive power control mode and wind farm grid connection location selection. (2) introducing DFIG internal constraints and modifying its parameters in dynamic power flow calculation based on specific frequency modulation strategy of DFIG. The dynamic power flow model considering the participation of DFIG in the primary frequency modulation of the system is put forward by quantifying the inertia of the DFIG unit to make it participate in the acceleration power sharing. Combined with an example, it is found that the inertia of DFIG is affected by wind speed and load reduction level, and when the acceleration power of the system is negative, under the same load reduction level, the higher the input wind speed is, the greater the active power reserve of the unit is. The stronger the system frequency support ability is. (3) although the current economic dispatch research involves the system frequency and SG frequency modulation capability, it ignores the wind power or replaces the specific wind turbine with wind power. In order to consider the primary frequency modulation capability of DFIG in economic scheduling, the dynamic power flow algorithm considering the participation of DFIG in frequency modulation is introduced into economic scheduling, and a probabilistic optimal power flow model considering DFIG participation in primary frequency modulation is proposed. Considering the probability characteristic of wind speed prediction error, the frequency offset caused by prediction error is introduced into the optimization target by weight coefficient. The validity of the proposed model is verified by an example. It is found that by selecting the appropriate weight coefficient of the objective function, the generation cost and the frequency offset caused by the prediction error can be taken into account in order to obtain better economy and security.
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM614

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