【作者】 张志荣；

【导师】 邱晓燕；

【作者基本信息】 四川大学 ， 电气工程（专业学位）， 2021， 硕士

【摘要】 能源发展是事关国家发展的重大战略问题,非化石能源的比例在飞速增长,未来将成为能源消费的主体。在交流配电网中,大规模分布式电源通过电力电子设备接入,负荷侧逐渐呈现直流化特征,大量变换器投入运行增加了网络损耗。相比之下,直流配电网可以节省变换器数量,具备经济可靠等特点,更符合源—荷直流化发展要求,配电网也将逐渐形成交直流混合拓扑状态,因此交直流混合配电网的优化运行技术成为热门研究课题。首先,为了奠定构建经济调度和电压优化模型的基础,分别建立了配电网中分布式电源的数学模型,阐述了柔性负荷的分类及其特点,建立了详细的电压源型换流站的潮流模型,并介绍了换流站的各种控制方式。由于潮流模型将导致优化调度模型属于非凸规划问题,分别介绍了基于线性规划理论和二阶锥规划理论将原模型转化为线性潮流模型和二阶锥松弛潮流模型的方法,并且阐述了交替方向乘子法分布式优化的基本原理,为交直流混合配电网优化问题求解奠定理论基础。然后,为了求得交直流配电网经济调度方案,促进可再生能源消纳,优化交直流两侧运行状态,将柔性负荷分为可转移负荷和可削减负荷,同时考虑储能参与优化调度的影响,计及交/直流线路损耗、储能和换流站损耗,通过调度分布式电源、储能系统以及电压源型换流器的输出功率,以购电费用、弃风弃光惩罚费用、网损惩罚费用、柔性负荷调度成本之和最小为优化目标,基于二阶锥松弛、分段近似线性化等技术,建立交直流配电网经济调度模型。在一个50节点算例系统上仿真分析,结果验证了所提优化调度方案的有效性和合理性。最后,提出一种分区分布式电压优化的方法,依据电压源型换流器连接情况,对交直流混合配电网使用耦合支路法,分成交流子区域和直流子区域。基于交替方向乘子分布式方法,以网络损耗最小、电压偏差最小和柔性负荷利用率最低为目标,构建分布式电压优化模型,并采用二阶锥松弛等技术转化为凸优化模型,在修改的IEEE 33节点算例系统中进行仿真计算,分析了交流侧功率和分布式电源对直流侧电压的影响,比较了换流器采用不同控制方式时优化结果,验证了所提分布式优化模型的合理有效性。更多还原

【Abstract】 Energy development is a major strategic issue related to national development.The proportion of non-fossil energy sources is increasing rapidly and will become the main energy consumption in the future.Large scale distributed generations are connected to the AC distribution network through power electronic equipment,and the load side gradually shows the characteristics of direct current,thus a large number of converters are put into operation,which increases the network loss.In contrast,the DC distribution network can save the number of converters and has the characteristics of economy and reliability,so it is more in line with the development requirements of DC source-load.The distribution network will gradually form an AC/DC hybrid topology.Therefore,the optimal operation technology of AC/DC hybrid distribution network has become a hot research topic.Firstly,in order to lay the foundation for the construction of economic dispatch and voltage optimization models,the mathematical models of distributed generations in the distribution network are established,the classification and characteristics of flexible loads are described,the detailed power flow model of the voltage source converter station is established,and various control methods of the converter station are introduced.Because the power flow model will cause the optimization dispatching model to be a non-convex programming problem,the methods of converting the original model into a linear power flow model and a second-order cone relaxation power flow model based on linear programming theory and second order cone programming theory respectively are introduced,then the basic principle of the distributed optimization of the alternative direction multiplier method is described,all the theories lay the foundation for the solution of the AC/DC hybrid distribution network optimization problems.Secondly,in order to obtain the economic dispatching scheme of AC/DC distribution network,promote the consumption of renewable energy,optimize the operating status of both sides of the AC and DC,the flexible load is divided into transferable load and reducible load,and consider the impact of energy storage participation in optimal dispatching,take into account AC/DC line losses,energy storage losses and converter station losses,by dispatching the output power of distribution generation,energy storage systems and voltage source converter,the economic dispatching model based on second order conic relaxation,segmental approximate linearization and other technologies is proposed that aimed to minimize all cost of purchasing electricity,abandoning wind and solar power,losses and dispatching flexible load.The effectiveness and rationality of the proposed optimal dispatching scheme is verified through the simulation analysis on a50-node system.Finally,a partitioned distributed voltage optimization method is proposed,the AC/DC hybrid distribution network is divided into AC and DC sub-regions using the coupled branch method based on the connection of voltage source converters.Based on the distributed optimization method of alternating direction multiplier method,a distributed optimization model is constructed with the goal of minimum power loss,minimum voltage deviation and minimum flexible load utilization,and the second order conic relaxation technology and others are used to transform it into a convex optimization model.Simulation calculations are carried out in the modified IEEE 33-node example system,and the influence of the AC side power and distributed generations on the DC voltage is analyzed,the optimization results when the converter adopts different control methods are compared,the rationality and validity of the proposed distributed optimization model is verified.更多还原