【作者】 王刚；

【导师】 张哲； 游大海；

【作者基本信息】 华中科技大学 ， 电气工程， 2018， 博士

【摘要】 本文针对含大规模风电且以火电机组为主的电力系统,围绕机组组合问题的优化方法和火电机组灵活性挖掘两个维度开展研究,以解决风电大规模接入引起的机组组合复杂度增长问题和灵活性资源需求扩大问题。优化方法研究维度针对风电出力特性建模引起的机组组合问题的复杂性;火电机组灵活性研究维度以优化方法研究成果为基础,拓展优化方法中的火电机组模型,并评估火电机组灵活性运行对机组组合问题的影响。本文工作主要包括以下4个方面:(1)提出了计及风电随机特性的备用模型,可在保证备用策略的经济性的同时,避免繁重的计算负担,有效解决了当前风电备用优化面临的难题。新提出的备用模型将备用容量成本和效益之间复杂的相关关系转换成更简明且易于建模的物理关联,解耦了备用优化复杂性与随机场景数目之间的关联。备用模型可通过大量风电随机场景构建生成,以准确反映风电随机特性对备用优化的影响,有利于机组组合模型准确评估备用容量的成本和效益,以保证备用策略的经济性。同时,本文论证了备用模型至少具有近似下凸特性,可采用分段累加和形式的分段线性函数进行线性化近似,从而可将复杂非线性的备用模型转化为少量由连续变量构成的线性约束集合,以大幅减少计算负担。(2)提出了一种新的扩展确定性网络约束机组组合方法,通过新提出的备用模型和精简网络约束分别解决了含风电机组组合问题所面临的备用优化问题和网络阻塞分析问题,有效解决了当前机组组合优化方法在实现优化结果经济性和计算效率双重目标上所面临的理论难题。该方法将备用模型融入到确定组组合模型框架中,实现系统备用水平和机组启停计划的协同优化,从而类似典型随机方法能综合权衡备用的成本和效益,并因此具有典型随机方法在经济性方面的优势。同时,由于备用模型所引入的计算负担很小,该方法保留了典型确定性方法在计算效率方面的优势。此外,该方法通过精简的网络约束弥补了典型确定性方法在网络阻塞分析上的劣势,且避免了典型随机方法中大量无效网络约束所带来的巨大计算负担。(3)提出了一种考虑启停出力轨迹的火电机组精确模型,并基于此研究了火电机组启停过程精确建模对于含风电电力系统机组组合在经济性和计算效率方面的影响。本研究论证了火电机组启停过程精确建模的经济价值,提出了火电机组启停过程精确建模可能引入过重计算负担问题的解决方案。新提出的火电机组模型仅针对火电机组启停过程的关键阶段,既能反映启停出力轨迹,又可避免引入繁重的计算负担。此外,本研究表明火电机组启动过程和停机过程的精确建模对于机组组合的影响存在差别,启动过程精确建模更易引起相对更重的计算负担,但是对于优化结果经济性的影响却相对更弱。因此,当机组组合问题面临过重的计算负担时,可通过简化启动过程精确建模来降低计算负担。(4)提出了助燃运行燃料费用模型来反映采用助燃运行煤电机组的运行成本,基于此提出了助燃运行经济性评估方法,并研究了煤电机组助燃运行对于含风电电力系统机组组合在经济性和计算效率方面的影响。该研究弥补了当前煤电机组助燃运行通用化模型和经济性评估方法的理论缺失,论证了煤电机组助燃运行的经济性价值,并提出了煤电机组助燃运行可能引入过重计算负担问题的解决方案。本文将复杂的分段非线性助燃运行燃料费用模型转换为混合整数线性约束集合,以大幅减少模型的计算负担。结合助燃运行燃料费用模型,本文提出了单台机组是否适宜助燃运行的经济性判据和经济性指标,为助燃经济性评估提供了理论依据。本研究表明助燃运行可改善机组组合优化结果的经济性,同时本文提出的扩展确定性方法可有效解决助燃运行燃料费用模型引入的计算负担问题。更多还原

【Abstract】 This dissertation focuses on two dimensions of research on the unit commitment for the power systems mainly constituted by thermal generators and integrated with large-scale wind power,including the optimization approach and thermal generator’s flexibility,so as to solve the two kinds of problems caused by large-scale wind power integration,including increasing complexity of unit commitment and enlarging flexibility requirements.The dimension of optimization approach studies the complexity of unit commitment caused by the modeling of wind power characteristics;based on the research on the optimization approach,the dimension of thermal generator’s flexibility expands the models of the thermal generators and evaluates the impacts of the flexible operation of thermal generators on the unit commitment.This dissertation includes the following four parts:(1)This dissertation proposes the reserve models considering the stochastic characteristics of wind power,which can concurrently ensure the economic efficiency and avoid the huge computational burden,and thus effectively solves the problem faced by the current reserve optimization research on wind power.The newly proposed reserve models convert the complex correlation between both the costs and benefits of reserve capacity into a more concise and easy-to-model physical association and thus decouple the tight relationship between the complexity of reserve optimization and the number of stochastic scenarios.Therefore,the reserve models can be constructed through a large number of wind power scenarios to accurately reflect the impact of the stochastic characteristics of wind power on reserve optimization,which is beneficial to the unit commitment to accurately evaluate the costs and benefits of reserve capacity and thus to ensure the economy of the reserve strategy.Meanwhile,this dissertation has verified that the reserve models have at least an approximately convex characteristic and thus is convenient for piecewise linearization using the piecewise linear functions of the piecewise accumulation form.After the piecewise linearization,these complex and non-linear reserve models can be transformed to a small set of linear constraints constituted by continuous variables,so as to greatly reduce the computational burden.(2)This dissertation proposes a new extended deterministic network-constrained unit commitment approach,which solves the reserve optimization problem and the network congestion problem faced by the unit commitment with wind power through the proposed reserve models and the proposed simplified network constraints,respectively.This approach effectively solves the difficulty faced by the current optimization approaches in concurrently achieving both economic performance and computational efficiency objectives.This approach incorporates the reserve models into the deterministic unit commitment framework to concurrently optimize the system reserve levels and on/off decisions,so as to comprehensively evaluate the costs and benefits of reserve capacity as the typical stochastic approach does,and thus has the economic performance similar to the typical stochastic approach.Meanwhile,this approach preserves the advantage of the deterministic approach in the computational performance because these reserve models just bring in very little computational burden.In addition,the proposed approach compensates the disadvantage of the typical deterministic approach in network congestion analysis through the proposed simplified network constraints and avoids the huge computational burden caused by a large number of inactive network constraints adopted in the typical stochastic approach.(3)This dissertation proposes an accurate thermal generator model considering the startup and shutdown power trajectories and studies the impact of the accurate modeling of the startup and shutdown processes of thermal generators on the unit commitment with wind power regarding both the economy of solution and computational efficiency.This study has verified the economic value of the accurate modeling of the startup and shutdown processes of thermal generators and proposed the solution to overcoming the possible heavy computational burden caused by accurate modeling.The newly proposed thermal generator model just takes into account the critical phases of the startup and shutdown processes so that this accurate model can not only reflect the startup and shutdown trajectories of thermal generators but also avoid the introduction of a heavy calculation burden.In addition,this study reveals that the accurate modeling of startup and shutdown processes has a different impact on the unit commitment.Accurate modeling of the startup process causes a heavier computational burden but has a weaker contribution to economic benefits.Therefore,it is advisable to simplify the accurate modeling of the startup process when the unit commitment problems face the heavy computational burden.(4)This dissertation proposes the fuel cost model considering low-load operation with auxiliary firing(LLOAF)to express the operating costs of coal-fired generators adopting LLOAF mode,proposes the economic evaluation method of LLOAF,and studies the impact of the LLOAF of coal-fired generators on the unit commitment with wind power regarding both the economy of solution and computational efficiency.This study has made up for the lack of the current theory in the universal modeling and economic evaluation method of LLOAF,verified the economic value of LLOAF of coal-fired generators,and proposed the solution to overcoming the possible heavy computational burden caused by the modeling of LLOAF mode of coal-fired generators.This dissertation transforms the complex and piecewise non-linear fuel cost model considering LLOAF into a set of mixed-integer linear constraints,thus greatly reducing the computational burden.Combining with the proposed fuel cost model,this dissertation proposes the economic criterion and economic index to judge whether it is economic for a coal-fired generator to be operated in the LLOAF mode and thus provides a theoretical reference for assessing the economy of LLOAF.This study reveals that LLOAF can improve the economic performance of the solution of unit commitment and the proposed extended deterministic approach can effectively reduce the increasing computational burden caused by the fuel cost model considering LLOAF.更多还原