Optimal reactive power control in a converter station during low-power operation of HVDC

When the high-voltage DC (HVDC) system is operated in low-power transmission, the overplus of reactive power provided by AC filters may still exist apart from satisfying the need of the converter station, restricted by the minimum number of filter banks. This will lead to a large number of surplus reactive power into AC system, affecting the safe and stable operation of power grid. Here, the impacts of the adjustment of on-load tap changer of converter transformer and the adjustment of control angle of the converter station on reactive power consumption are analysed. Taking effects on the adjustment of control devices and the interchange of reactive power into account, a static reactive power optimisation model based on the actual control strategy of reactive power in a converter station is set up, which provides theoretical basis for an optimal control during low-power operation. Taking Tian-Guang HVDC project as an example, the simulation results verify its effectiveness of the proposed method.