风火打捆传统直流外送系统中控制环节对轴系-控制交互模式的影响机理研究

Research on the Influence Mechanism of Control Loops on Shaft-control Interactive Mode for Wind-thermal-bundled Power Transmission Through LCC-HVDC System

风火打捆直流外送系统中风电场和电网换相换流器高压直流输电(line commutated converter based high voltage direct current,LCC-HVDC)控制系统可能会激发火电机组的轴系扭振。文章首先采用复转矩系数法和特征值分析法识别出LCC-HVDC定电流、风机直流电压外环控制是影响轴系-控制交互模式的关键控制环节。然后,通过推导系统传递函数,提取出反映LCC-HVDC定电流和风机直流电压外环控制对轴系-控制交互模式影响的多条关键控制路径,包括HVDC定电流控制路径、风机直流电压外环控制路径和两者间交互控制路径。进一步,定量计算每条作用路径在轴系-控制交互模式处的阻尼系数,并通过相位补偿在关键控制路径上分别设计附加阻尼控制来提高对应阻尼系数,从而抑制火电机组轴系扭振。最后,基于PSCAD/EMTDC的详细电磁暂态仿真,验证了理论分析的正确性及振荡抑制策略的有效性。

Torsional vibration of thermal power unit may be induced by the control system of wind farm and line commutated converter based high voltage direct current(LCC-HVDC)for wind-thermal-bundled power transmission through HVDC system.First,by using complex torque coefficient and eigenvalue analysis methods,it is identified that LCC-HVDC constant current and wind turbine DC voltage outer loop controllers are the key control loops affecting the shaft-control interactive mode.Then,based on the system transfer function,multiple key control paths which reflect the influence of LCC-HVDC constant current and wind turbine DC voltage outer loop controllers on shaft-control interactive mode are extracted,including HVDC constant current control path,wind turbine DC voltage control path and interactive control path.Then,the damping coefficients of shaft-control interactive mode provided by different paths are calculated quantitatively.The supplementary damping control is designed to improve path damping coefficients via phase compensation on key control paths,thereby suppressing torsional vibration.Finally,the PSCAD/EMTDC simulation results verify the correctness of theoretical analysis and the effectiveness of the oscillation suppression strategy.