大规模海上风电场经HVDC并网引发轴系扭振分析与抑制

大规模海上风电场经HVDC输电可提高其输电效率，但当风机轴系考虑为两质块模型时，直流整流侧的控制方式有可能向附近的风机引入负阻尼，将导致风机轴系扭振，影响系统的安全稳定运行。本文首先分析风机轴系扭振产生机理，通过复转矩系数法得到系统的电气阻尼系数，以判断固有扭振频率下的系统稳定性；然后计算出待补偿的电磁转矩和风机转子转速的相角差；最后通过设计附加阻尼控制器抑制风机轴系扭振。在PSCAD程序中搭建风电场经HVDC并网模型进行仿真分析，分析结果表明系统加入阻尼控制器后，风机轴系扭振迅速衰减，控制器的加入有效增大了系统阻尼比。此研究分析为大规模海上风电场通过HVDC并网提供了理论基础。

Analysis and Damping of Subsynchronous Torsional Interaction in Large Scale Offshore Wind Farm Supply Power by HVDC

In order to improve the grid-connected efficiency of the large scale offshore wind farm, HVDC was used widely. However, when the wind turbines and wind generators are two-mass or multi-mass shaft model, the control mode of power electronic equipment at rectifier may introduce negative damping to nearby generators and cause torsional vibration named subsynchronous torsional interaction. This phenomenon may lead to system instability. This paper gets electrical damping coefficient curve base on complex torque coefficient approach firstly, and works out the phase lag between the electromagnetic torque and the rotate speed at nature frequency of the shaft. Then a supplementary subsynchronous damping controller is designed to damping the oscillation between shaft masses. The effectiveness of the controller can be verified through time domain simulation and eigenvalue analysis. The simulation results showed that the oscillation amplitude could decreased quickly when the controller was added to the system, which provides a theoretical basis when the offshore wind farms are connected to the onshore grid through a HVDC transmission line.