EMS experience of reactive power control for LCC based HVDC system

Line-Commutated Converter (LCC) based HVDC lines are widely used to transmit electric power and interconnect asynchronous AC systems. Due to the characteristic of LCC-based HVDC, large amount of reactive power consumed by HVDC potentially deteriorates system voltage stability. Reactive power control is crucial to alleviate adverse impacts of HVDC reactive power consumption from AC network and secure voltage stability of AC system. In this paper, a special reactive power control (RPC) approach is presented and implemented in EMS at system control center. Reactive power resources at HVDC converter substations are controlled collaboratively to satisfy the reliability criteria and voltage stability constraints. Numerical studies on Alberta power grid at different HVDC MW transfer levels have demonstrated that the RPC approach is effective in controlling reactive power to support the connected HVDC system. The net exchange of reactive power between the HVDC and the AC system can be minimized at levels close to neutral in most real-time operation conditions.