基于多端柔性直流的海上风电场并网控制策略研究

发布时间：2018-05-14 02:05

本文选题：多端直流输电系统VSC-MTDC + 海上风电　；参考：《华北电力大学》2014年硕士论文

【摘要】：海上风力发电技术作为我国大力发展风力发电的新方向，使用多端柔性直流输电技术(Voltage-Sourced Converter Multi-Terminal HVDC，VSC-MTDC)来进行海上风电场并网，风电功率集中向岸上大电网系统远距离输送。柔性直流输电系统(Voltage-Sourced Converter High Voltage Direct Current，VSC-HVDC)被认为是解决这一瓶颈问题的最佳方案。本文重点研究了用于两个海上风电场与两个交流电网系统互联的VSC-MTDC并网控制策略以及针对交流电网故障或直流输电线路故障时多端直流系统故障穿越技术的研究。 1.首先针对多端直流输电网络的模型进行分析，建立了VSC-HVDC的数学模型，讨论了直流电压控制、有功/无功功率控制、交流电压控制、频率控制等，实现控制环节中的有功/无功功率的解耦控制。然后对适用于海上直流输电系统的风电场侧换流站(Wind Farm Voltage-Sourced Converter，WFVSC)和网侧换流站(Grid SideVoltage-Sourced Converter，GSVSC)的控制器进行了设计，实现了风场侧的交流母线电压和频率的恒定以及海上风电功率的自动汇集。最后针对双馈风力发电机组组成的海上风电场控制系统进行了分析，同时确定了大容量海上风电场的模型。 2.提出了一种用于两个海上风电场与两个交流电网互联的VSC-MTDC系统的并网控制策略。GSVSC采用了一种上下级式直流电压控制。该并网控制策略不仅可以在系统正常工作期间满足不同的市场调度机制的要求；还可以在一个严重的干扰之后（如岸上交流电网电压暂降或者换流站从系统中退出运行，尤其是处于直流电压控制的换流站退出运行时），系统仍能够在一定的时间内维持相对稳定；同时避免了通信延迟或失败时导致系统的非正常运行或者系统故障脱网。针对于海上直流输电系统可能接入一个海岛电网系统，设计了一个辅助频率控制器。对海岛电网系统进行风电功率输送，同时还提高了该海岛电网系统的频率快速稳定。 3.针对于多端直流输电系统的故障穿越技术。基于电压源型换流器的电压-电流特性和故障时减少风电功率注入的思想，提出了一种多端直流输电系统的协调控制策略。系统故障运行时，以VSC-MTDC直流电压所反映的功率不平衡信息，通过风电场侧的换流站转化为频率信息，协调风场间各风电机组出力。直流系统故障期间，风场侧换流站承担系统直流电压的稳定。该协调控制策略避免多端直流输电系统对各换流站之间高速通信的要求，实现各换流站间的自主协调控制。最后，搭建了Matlab/Simulink仿真模型，针对所提出控制策略的动态性能进行了仿真验证，结果表明所提控制策略能够保持直流电压在交直流故障等大扰动下相对稳定，维持系统正常运行。 4.通过VSC-MTDC实验系统，编写相应的控制程序，对VSC-MTDC的运行特性以及本文提出的并网控制策略进行了实验验证。实验结果显示，本文所研究的换流站并网控制策略能够实现VSC-MTDC的稳态运行。对VSC-MTDC接入弱交流电网系统时能够提供快速的有功支持，提高受端系统的频率快速稳定。模拟海上风电场通过VSC-MTDC系统进行并网，，可以实现多种功率调度机制。
[Abstract]:As a new direction for the development of wind power generation in our country, the offshore wind power generation technology uses Voltage-Sourced Converter Multi-Terminal HVDC (VSC-MTDC) to connect the offshore wind farm to the grid, and the wind power is concentrated in the long distance away from the large power grid system on the shore. The flexible direct current transmission system (Voltage-Sourced Conv) is used. Erter High Voltage Direct Current, VSC-HVDC) is considered to be the best solution to this bottleneck problem. This paper focuses on the study of the VSC-MTDC grid control strategy for the interconnection of two offshore wind farms and two AC power grid systems, as well as the multi terminal DC system fault crossing technique for AC network failure or DC transmission line fault. The study of surgery.
1. firstly, the model of multi terminal DC transmission network is analyzed, and the mathematical model of VSC-HVDC is established. The DC voltage control, active / reactive power control, AC voltage control and frequency control are discussed, and the decoupling control of active / reactive power in the control link is realized. Then, the wind farm side applicable to the HVDC power transmission system is applied to the wind farm side. The controller of the converter station (Wind Farm Voltage-Sourced Converter, WFVSC) and the net side converter station (Grid SideVoltage-Sourced Converter, GSVSC) has been designed to realize the constant voltage and frequency of the AC busbar on the wind field and the automatic collection of the wind power at sea. The control system is analyzed, and the model of large capacity offshore wind farm is determined.
2. a parallel control strategy for the VSC-MTDC system, which is used for the interconnection of two offshore wind farms with two AC power grids, is proposed..GSVSC uses an upper and lower DC voltage control. The grid control strategy can not only meet the requirements of different market scheduling mechanisms during the normal work of the system, but also can be used in a serious interference. The system is still able to maintain relative stability in a certain period of time, such as the voltage sags on the AC power grid or the converter station exit from the system, especially when the DC voltage controlled converter station is out of operation. At the same time, it avoids the abnormal operation of the system or the system fault removal when the communication delays or failures. A HVDC system may be connected to an island power grid system, and an auxiliary frequency controller is designed. The wind power transmission is carried out to the island power grid system, and the frequency and stability of the island power grid system is also improved.
3. for multi terminal DC transmission system fault crossing technology. Based on the voltage current characteristics of voltage source converter and the idea of reducing wind power injection when failure, a coordinated control strategy for multiterminal HVDC system is proposed. The power imbalance information reflected by VSC-MTDC direct current voltage is passed when the system fails to run. The converter station on the side of the wind farm is converted into frequency information to coordinate the output of each wind turbine in the wind field. During the fault of the DC system, the wind field side converter station assumes the stability of the DC voltage of the system. The coordinated control strategy avoids the demand for the high-speed communication between the various converter stations and realizes the autonomous coordination control between the converter stations. Finally, the Matlab/Simulink simulation model is built to simulate the dynamic performance of the proposed control strategy. The results show that the proposed control strategy can keep the DC voltage relatively stable under the large disturbances such as AC and DC fault, and maintain the normal operation of the system.
4. through the VSC-MTDC experimental system, the corresponding control program is written, and the operation characteristics of VSC-MTDC and the proposed grid control strategy are verified experimentally. The experimental results show that the control strategy of the converter station in this paper can realize the steady operation of the VSC-MTDC. It can provide the VSC-MTDC access to the weak AC power grid system. The rapid and active support can improve the frequency and stability of the end-to-end system. The simulation of offshore wind farms through the VSC-MTDC system can achieve a variety of power scheduling mechanisms.

【学位授予单位】：华北电力大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM614

【参考文献】