海上风电经混合直流输电送出的特性研究

发布时间：2018-03-25 01:11

本文选题：混合　切入点：高压直流　出处：《华北电力大学》2014年硕士论文

【摘要】：传统高压直流输电(LCC-HVDC)方式因其具有大功率远距离输电的特点已获得广泛应用,然而由于采用的是半控电力电子器件,系统在运行中会吸收大量的无功功率,且易发生换相失败。随着电力电子器件的发展,轻型直流输电(VSC-HVDC)显示出了功率可以独立调控的特点,可以向弱系统或无源网络供电,但换流器造价较高。将传统高压直流输电和轻型直流输电结合起来的混合直流输电,具有电压源换流器的独立控制有功和无功功率等优点,也能保证相对轻型直流输电更好的经济性。混合直流输电适用于新能源并网领域中,本文针对风力发电,首先提出了基于直驱风机(direct-drive permanent magnet synchronous generators)的海上风电经混合直流输电送出的拓扑结构：风电场侧换流器为电网换相换流器(Line-Commutated-Converter,LCC),网侧换流器为电压源换流器(Voltage Source Converter,VSC),并对此模型在PSCAD仿真软件中进行了故障分析,在所有的故障情况下系统皆能在故障消失后恢复正常运行。针对双馈风机,提出了基于双馈风机(double fed induction generator,DFIG)的海上风电经混合直流输电送出的拓扑结构：风电场侧换流器为电压源换流器,网侧换流器为电网换相换流器。基于上述拓扑提出了输电系统能够最大程度将风能送到电网的协调控制策略,由于逆变侧为LCC,易发生换相失败,提出逆变侧为弱系统时发生接地故障时减少换相失败次数的改进控制策略。最后在PSCAD仿真软件中模拟了基于DFIG的海上风电利用混合直流送出电能,仿真结果验证了网侧换流站控制系统的良好的功率跟踪能力以及在交流侧故障时改进控制策略能够抑制换相失败的次数。这两种风电送出的结构,能够很好的综合传统直流和轻型直流的优点,对于海上风电的直流送出有很好的应用前景。
[Abstract]:Traditional high voltage direct current transmission (HVDC) LCC-HVDCmode has been widely used because of its characteristics of high power long-distance transmission. However, because of the use of semi-controlled power electronic devices, the system will absorb a large amount of reactive power in operation. With the development of power electronic devices, VSC-HVDCA shows that the power can be controlled independently, and can supply power to weak system or passive network. But the cost of converter is high. The hybrid DC transmission which combines traditional HVDC transmission and light HVDC transmission has the advantages of independent control of active power and reactive power of voltage source converter. Hybrid DC transmission can be used in the field of new energy grid connection, this paper aims at wind power generation. Firstly, the topology of offshore wind power through hybrid DC transmission based on direct-drive permanent magnet synchronous generators is proposed: the wind farm side converter is the power grid commutated-converter LCCs, the net-side converter is the voltage source converter voltage Source converter VSCS, and for this purpose, the wind farm side converter is the power grid commutated-converter and the grid side converter is the voltage source converter. The fault analysis of the model is carried out in the PSCAD simulation software. In all cases of failure, the system can resume normal operation after the fault has disappeared. For doubly-fed fan, The topology of offshore wind power through hybrid DC transmission based on doubly-fed fan double fed induction generator is presented. The wind farm side converter is a voltage source converter. The grid-side commutator is the commutator of the power grid. Based on the above topology, a coordinated control strategy for the transmission system to maximize wind power to the power grid is proposed. Because the inverter side is LCC-prone to commutation failure, An improved control strategy is proposed to reduce the frequency of commutation failure when the inverter side is a weak system. Finally, the hybrid DC power generation from offshore wind power based on DFIG is simulated in PSCAD simulation software. The simulation results show that the good power tracking ability of the control system and the improvement of control strategy in AC side fault can restrain the frequency of commutation failure. It can integrate the advantages of traditional DC and light DC, and has a good application prospect for offshore wind power supply.
【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】：TM721.1

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