A grid-connected DFIG for wind power generation can affect power system small-signal angular stability in two ways: by changing the system load flow condition and dynamically interacting with synchronous generators (SGs). This paper presents the application of conventional method of damping torque analysis (DTA) to examine the effect of DFIG’s dynamic interactions with SGs on the small-signal angular stability. It shows that the effect is due to the dynamic variation of power exchange between the DFIG and power system and can be estimated approximately by the DTA. Consequently, if the DFIG is modelled as a constant power source when the effect of zero dynamic interactions is assumed, the impact of change of load flow brought about by the DFIG can be determined. Thus the total effect of DFIG can be estimated from the result of DTA added on that of constant power source model. Applications of the DTA method proposed in the paper are discussed. An example of multi-machine power systems with grid-connected DFIGs are presented to demonstrate and validate the DTA method proposed and conclusions obtained in the paper.
Bibliographical noteElectric energy sector growth requires considerable investment in sustainable generation. Infrastructure must accommodate diverse and renewable energy sources, including DFIG technology, which poses problems for system stability. This paper proposes a method which prevents unnecessary disconnection of DFIG wind turbines during system faults thereby minimising impact on stability while reducing CO2 emission. The work benefits a power system operator by ensuring preservation of dynamic stability throughout grid disturbances with DFIG connection. Sponsored by EPSRC UK-China joint-research consortium (EP/F061242/1) and Science Bridge (EP/G042594/1), the work has strengthened collaboration with China (NCEPU) and will contribute to subsequent EPSRC UK-China Innovative Bridge funding.
- power system
- small-signal angular stability
- Heffron-Phillips model
- damping torque analysis