摘要
随着可耗竭能源的日益枯竭,继水力资源后,风能、太阳能等可再生能源的开发利用再度受到重视。如今,风力发电技术成熟度高、商业化前景广阔,得到大规模发展。风电作为能够部分代替化石燃料的可再生能源,可降低污染物排放,对改善能源结构起到了积极作用。然而,风电的随机波动性,使电网运行与控制难度增加,甚至会影响电网安全运行。因此,在大规模风电并网后如何配置备用,以保证电网运行的安全性和经济性,必然成为研究热点和焦点。
针对电网运行过程中有功功率的平衡,以及运行质量(安全和经济)水平,风电并入电网后,出现两个重要的问题:一是如何尽量准确的把握风电变化的规律;二是如何进行备用的配置以把握电网运行的风险。
在当前形势下,以风电并网为线索,在研究风电变化规律的基础上,以电网运行风险引导下的备用配置为核心,对电网运行条件下如何协调安全性和经济性进行研究,具有重要的理论意义和实际价值。
对此,本文以烟台电网为实际背景,就风电并入对电网运行决策影响进行了深入的理论研究和实际工程软件开发,其主要工作体现如下。
(1)针对地区电网并入多个风电场的状况,论证分析所有风电场总输出功率变化较单一风电场输出功率变化具有更好的规律性,给出风电总量与风电分配因子两个概念,提出短期风电场功率的预测模型和求解方法。其焦点体现在:风电总量、风电分配因子以及他们之间的随机关联规律,最小二乘支持向量机和卡尔曼滤波技术对风电总量和风电分配因子的自适应动态预测算法,基于关联规律间接实现风电场输出功率的短期预测。该研究对探索电网层面上相关节点的风电功率预测问题给出了新的解决思路和方法,对有效把握风电功率规律是有益的。
(2)风电随机规律的特点体现在未来时刻功率分布范围的分散性,仅对期望进行分析难以反映其特征,电网运行风险也难以准确把握。对此,本文基于分位点回归分析理论,对风电功率波动区间通过支持向量机自适应地选取回归函数,建立风电功率分位点回归模型,并基于内点法对该模型进行求解,进而实现分位点预测,以把握未来时刻风电功率的波动区间。该方法的意义在于提供可信的风电功率波动区间分析结果,为调度部门应对风电波动,更加准确地评估电网运行风险提供重要依据。
(3)明确风电并入对电网运行风险的影响,是维持电网运行风险水平、保证电网安全经济运行的关键所在。在对风电波动区间的概率分布进行全面把握基础上,将风电波动分布规律与电网中机组停运容量概率表相结合,建立计及风电影响的电网有功平衡的投运风险模型和分析方法。在此基础上,以投运风险水平为约束条件,将累积停运容量概率(风险约束)嵌入到机组组合决策模型中,予以研究和分析,以烟台等值电网作为算例,对风电并入后电网运行成本、备用容量配置的影响情况进行了详细分析。
(4)当电网接入一定规模的风电时,为追求风电高效利用而使电网调度更加复杂。针对风电接入电网,调度面临煤耗量和风电高效利用间的矛盾问题,将风电能够为电网节约的煤耗量作为风电价值的度量,在经济机制下,对风电价值进行评估,由此构建运行条件下计及接纳风电能力的电网调度数学模型,核心为在与风电波动相关的各种关联约束下,通过数学优化调整调度方案,使其经济性和接纳风电能力得到折中决策。利用该模型能够确定电网允许风电波动的范围,使调度运行过程中的煤耗和电网对风电的接纳能力得到有效协调。符合节能发电调度理念。
(5)以烟台电网为对象,就风电并入对电网运行的影响进行了实际分析和研究,在计及风电的背景下,对其建立潮流分析、短路容量分析、稳定分析、安全可靠经济分析等模型,并给出相应的解决方法,经过对烟台电网给定的条件,进行了全面翔实的计算和分析,给出风电并入对烟台电网运行影响的具体所在,并提出应对这一影响的具体措施,由此在风电对电网影响的实际研究上向前迈进了一步。
With the depletion of non-renewable resources, renewable resources have attracted the attention of the world. As the high maturity of wind power technology, it has been developed on quite a large scale. Wind power is recyclable and non-polluting, so that it can be a substitution of fossil fuels and improve the resource composition of power grid. However, the stochastic volatility of wind power makes power grid operation more difficult and even a threat to power grid security sometimes. How to allocate the reserve capacity with wind power integration has become the focus of research.
After wind power integration, there are two issues for power balance and operation quality. The first is fluctuation regularity of wind power and the other is reserve capacity allocation. In the current situation, the research on coordination of security and economy in power grid operation has important theoretical and practical value.
In this thesis, an exploratory study on optimal operation of power grid with wind power integration is carried out, which is based on mathematical optimization theory. The main works and innovative achievements of the thesis are as follows:
1. Considering the regional grid with several wind farms integrated, the total wind power has a better regularity comparing to single wind farm. A ultra-short term forecasting method of wind farms is proposed in this paper, which is based on the correlation of total power and wind farms. The Least-Square Support Vector Machine and Kalman filter are adopted respectively to forecast total wind power and distribution factors recursively, so that the good regularity of total wind power could be restored to wind farms and the short power forecasting system of wind farms is established indirectly.
2. The stochastic property of wind power leads to great error on forecasting result, and a fluctuation interval analysis of forecasting result is required for security operation. In this paper, an interval analysis model of wind power built based on quantile regression is proposed. After selection of regression function by support vector machine, the model of quantile regression is established for wind power. The interior point is adopted here to solve the model, then the analysis result of wind power fluctuation interval ahead consisting of a series of quantiles is obtained. The case study shows that the methodology proposed in this paper could provide a reliable interval analysis result for the power dispatching center which is beneficial to security operation, risk Assessment and the reserve capacity reduction.
3. Analysis of impact on power grid operation risk by wind power integration is the key issue to maintaining the security level. Based on regularity of wind power fluctuation, the probability distribution of wind power can be combined with capacity outage probability table and the impact of wind power on power grid operation risk is specified. For further study on the influence to power grid scheduling, cumulative capacity outage probability table is introduced into Unit Commitment. The power grid in Yantai is study and the influence on operation cost and reserve capacity allocation is analyzed in detail.
4. As the installed capacity of wind power in power grids reach a certain scale. the dispatching schedule becomes more complex for high efficiency utilization of wind power. In a power grid with wind power, there is a contradiction between fuel cost and effective utilization in the scheduling process. In this paper, the fuel cost saved is taken as the value of wind power. A scheduling method considering wind power receptiveness is proposed so that a fluctuation range can be calculated to coordinate the fuel cost and wind power receptiveness. Case study shows that the method proposed is appropriate for power grid scheduling considering renewable energy with uncertainty and accords with the principle of energy conservation.
5. The project "Study of Impact on Power Grid operation in Shandong by Wind Power Integration" is introduced briefly. With analysis on power flow, Short-circuit capacity, static stability and reliability, the impact on Power Grid operation in Yantai by wind power integration is specified and measures of impact improvement are proposed.
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