基于柔性直流联网的风力发电系统的协调控制研究

发布时间：2018-01-05 04:03

本文关键词：基于柔性直流联网的风力发电系统的协调控制研究　出处：《华北电力大学》2014年博士论文　论文类型：学位论文

【摘要】：多端柔性直流输电技术更适合风电联网系统的潮流优化控制,然而直流系统内不具备交流同步电网的机械惯性支持,因此风电机组和换流站需具备快速的有功协同调节能力,以提高其稳定性。本文首先提出变速风电机组的虚拟惯性和一次调频综合控制策略,使风电机组具有较完备的动态有功-频率调节能力。然后建立风电端换流站的交流侧频率与直流侧电压的联动调节关系,进而提出含风电的多端直流系统的有功协调控制策略,充分利用各端电网间的相互支持能力及风电机组的机械储能,确保风电直流联网系统稳定运行及增强其故障穿越能力。本文的主要研究内容如下： 1.研究了变速风电机组及直流输电系统的动态模型及控制方法,分析了直流电网的组网方式,提出一种适用于风电联网的多端直流系统拓扑结构及其运行模式,搭建了基于直流联网的风力发电系统的仿真平台,为风电直流联网系统的功率协调控制策略研究奠定了基础。 2.分析了变速风电机组虚拟惯性控制及调频控制方法,提出了风电机组虚拟惯性与一次调频相结合的综合频率控制策略。通过引入减载水平和桨距静调差系数的定义,并利用变桨技术,改进了风电机组的减载运行方法和可整定静调差系数的一次调频控制策略,并最终实现了与虚拟惯性控制的有机结合,使风电场不仅具备惯性频率响应,并可满足系统的一次调频要求,进而对电网有功扰动具有较为完备的快速有功调节能力。 3.分析了交流电网故障扰动对两端柔性高压直流输电系统稳定运行的影响,提出了变速风电机组及换流站协同控制的两端柔性直流输电系统的故障穿越方法。在网侧换流站因电网故障而限流期间,改变风电侧换流站的恒频控制方式,将直流侧电压波动与交流侧频率调节建立有效联系,从而可通过变速风电机组的虚拟惯性控制快速调节电磁功率,利用风电机组的机械储能为直流系统的故障穿越提供有效支持。该方法成本低,不依赖于通讯,可拓展到多端直流系统之中。 4.含风电的直流系统内惯性小、功率波动大,为提高其稳定性,本文提出了多端系统之间的分散协同控制及源网协调控制策略,使互联系统具备了快速的有功协同调节能力。首先,设计了各端换流站的分散协同控制特性,确保直流电网在不同运行模式下均可对直流电压进行有效控制。然后分别设计了受端换流站的直流电压-有功功率控制和风电端换流站的变频控制环节,使分散在各端电网内的常规电源以及在综合频率控制下的风电均可充分发挥其有功调节能力,实现源网协调控制。本文所提出的风电直流联网系统的协调控制策略,充分利用各端电网间的相互支持能力及风电机组的机械储能,从而增强了高风电渗透率下直流互联电网的稳定运行能力,并且该控制策略无需通讯,易于扩展。
[Abstract]:Multi-terminal flexible DC transmission technology is more suitable for wind power network power flow optimization control, but the DC system does not have the mechanical inertia support of AC synchronous power grid. Therefore, wind turbine and converter station need to have rapid active power co-regulation ability to improve its stability. Firstly, this paper puts forward the virtual inertia and primary frequency modulation integrated control strategy of variable speed wind turbine. The wind turbine has more complete dynamic active power and frequency regulation ability. Then, the relationship between AC side frequency and DC side voltage of wind power terminal converter station is established. Furthermore, the active power coordination control strategy of multi-terminal DC system with wind power is put forward, which makes full use of the mutual support ability of each terminal network and the mechanical energy storage of wind turbine. The main contents of this paper are as follows: (1) to ensure the steady operation of wind power DC interconnection system and to enhance its fault traversing capability. 1. The dynamic model and control method of variable speed wind turbine and HVDC transmission system are studied, and the networking mode of DC network is analyzed. A multi-terminal DC system topology structure and its operation mode are proposed, and the simulation platform of wind power generation system based on DC interconnection is built. It lays a foundation for the study of coordinated power control strategy of wind power DC interconnection system. 2. The virtual inertial control and frequency modulation control method of variable speed wind turbine are analyzed. A comprehensive frequency control strategy combining virtual inertia and primary frequency modulation of wind turbine is proposed. By introducing the definitions of load reduction level and pitch static adjustment coefficient, and using the technology of variable propeller. The paper improves the load reduction operation method of wind turbine and the primary frequency modulation control strategy which can adjust the coefficient of static adjustment difference, and finally realizes the organic combination with virtual inertial control, which makes the wind farm not only have the inertial frequency response. The system can meet the requirement of primary frequency modulation, and then has a relatively complete ability of fast active power regulation for the active power disturbance of the power network. 3. The influence of the fault disturbance on the stable operation of the flexible HVDC transmission system is analyzed. This paper presents a fault crossing method for the flexible HVDC transmission system controlled by a variable-speed wind turbine and a converter station. The constant frequency control mode of the wind power converter station is changed during the period when the grid side converter station is limited due to the power network fault. The DC side voltage fluctuation and the AC side frequency regulation can be established effectively so that the electromagnetic power can be adjusted quickly by the virtual inertial control of the variable speed wind turbine. The mechanical energy storage of wind turbine is used to provide effective support for fault passage of DC system. This method is low cost independent of communication and can be extended to multi-terminal DC system. 4. The DC system with wind power has small inertia and large power fluctuation. In order to improve its stability, the decentralized cooperative control and source-network coordination control strategy between multi-terminal systems are proposed in this paper. The interconnected system has the ability of fast active power co-regulation. Firstly, the decentralized cooperative control characteristics of each terminal converter station are designed. It is ensured that DC voltage can be controlled effectively in different operation modes of DC network. Then the DC voltage-active power control of terminal converter station and frequency conversion control link of wind power converter station are designed respectively. The conventional power supply scattered in each terminal network and the wind power under the integrated frequency control can give full play to its active power regulation ability. In this paper, the coordinated control strategy of wind power DC interconnection system is proposed to make full use of the mutual support ability of each terminal network and the mechanical energy storage of wind turbine. Therefore, the stable operation ability of DC interconnected power network under high wind power permeability is enhanced, and the control strategy is easy to be extended without communication.
【学位授予单位】：华北电力大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TM614

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