一种直流系统变斜率VDCOL控制策略优化方法

An Optimization Method of Variable Slope VDCOL Control Strategy for DC System

摘要:

在不追加额外的硬件设备投资的前提下,提升直流输电系统的抑制连续换相失败的能力具有重要意义。为此,首先阐述了基于电网换相的直流输电系统换流器换相机理,分析了低压限流启动(voltage dependent current order limiter, VDCOL)的控制方法,并根据实时测量的换流母线电压VDCOL的启动电压替代常规的直流电压测量,得到系统故障期间变化缓慢的启动电压。其次基于正常换相机理分析,改变常规VDCOL直流电压与直流电流之间的线性静态恢复关系,将VDCOL常规控制模型替换为变斜率数学模型,再将计算得到的VDCOL启动电压与变斜率VDCOL相结合。最后基于CIGRE HVDC标准测试模型验证了本文提出的控制策略在抑制连续换相失败方面具有明显的有效性与优越性。

Abstract:

On the premise of no additional investment in hardware equipment, it is of great significance to improve the ability of the DC transmission system to suppress continuous commutation failures. To this end, firstly, the commutation mechanism of HVDC transmission system based on grid commutation is expounded, the control method of VDCOL is analyzed, and the voltage dependent current order limiter (VDCOL) is activated according to the real-time measurement of the commutation bus voltage. The starting voltage of the system replaces the conventional DC voltage measurement to obtain the starting voltage that changes slowly during system faults. Secondly, based on the analysis of the normal switching mechanism, the linear static recovery relationship between the DC voltage and the DC current of the conventional VDCOL is changed, the conventional control model of the VDCOL is replaced with a variable slope mathematical model, and the calculated VDCOL start-up voltage is combined with the variable slope VDCOL. Finally, based on the CIGRE HVDC standard test model, it is verified that the control strategy proposed in this paper has obvious effectiveness and superiority in suppressing continuous commutation failure.