Optimisation of reactive power compensation of HVAC cable in off-shore wind power plant

High voltage AC (HVAC) transmission system is preferred to be used in off-shore wind power plant which is located within 40km from the seashore. Capacitance of HVAC cables is naturally higher than that of overhead lines, and it should be properly compensated. P model of three-core XLPE cable which is widely used in off-shore wind power plant was applied in the paper. Based on this model, impacts of reactive power compensation on HVAC transmission system, including capacity and location of compensation equipment, were analyzed and simulated then. Research showed that inductive compensation at off-shore side of the cable is more effective to decrease power loss along the cable and increase its transmission capacity than that at onshore side, while the latter is more appropriate to improve the power factor at onshore access point of the wind power plant to grid. Compensation capacity was optimized to realize the best economy with designated certain parameters of HVAC system by Sequential Quadratic Programming (SQP) method. Finally by SQP costs of 35kV and 220kV HVAC transmission system were compared, critical distance and transmission capacity of these two systems adoption were found. These results can be a reference of HVAC transmission system design of off-shore wind power plant.