Coordinated utilisation of wind farm reactive power capability for system loss optimisation

Most wind farms currently being installed are based upon doubly fed induction generator (DFIG) or direct-drive synchronous generator (DDSG) technology. Given that one of the impacts of introducing distributed generation is an alteration of steady-state power flows and voltages, both technologies are capable of providing local voltage support. Wind farms may, therefore, be included in optimal power flow (OPF) calculations to minimise fuel cost and/or network losses. The IEEE 30-bus system is considered as a case study, comparing fixed-speed induction generator (FSIG) requirements with DFIG capability. Results are presented for a range of DFIG capability modes, at varying system load and wind farm penetration levels. A significant reduction in losses can be achieved by suitable co-ordination of DFIG reactive power import/export, operating within typical grid code specifications. It is shown that the dynamic variability of reactive power requirements is readily accommodated by the power system. Finally, implementation options for the scheme and incentivising strategies are considered.