August 01, 2003

Advanced Models for Wind Power Generation

Since the first release of the doubly-fed induction generator model in 11/2000, DIgSILENT has recently completed a number of generic, large scale and high precision wind turbine models for both, doubly-fed as well as full converter driven generation systems. As those models are fully integrated in the PowerFactory software, the full range of application aspects such as load flow, fault analysis, harmonics, protection simulation, stability calculations (RMS) as well as electromagnetic transients (EMT) are supported.

The drastic increase of embedded wind generation has initiated a complete re-consideration of connection conditions. As a result it is expected that in more and more systems the disconnection of wind turbines in cases of system faults will not be accepted any more. As a consequence, simplified models which are valid for a certain operational range are no more applicable. Having such situations in mind, DIgSILENT has developed from the very beginning wind generation models with large-scale validity.

The most complex behaviour in case of faults is observed for the doubly-fed induction generator. The generic wind turbine model for these type of generators is therefore considering the following components:

  • Wound-rotor induction generator (3rd / 5th order)
  • Rotor side converter
  • Grid side converter
  • DC-system with DC capacitance dynamically represented
  • Control systems for rotor-side and grid-side converters
  • Protection systems incl. crow-bar protection
Prime Mover
  • Wind turbine with cp-'lambda' characteristics
  • Blade angle control
  • Multi-mass shaft dynamics

In RMS simulation mode (classical stability analysis) the user will benefit from the superior PowerFactory simulation algorithms allowing for fast and accurate solutions avoiding any compromise in model precision. Simulation step sizes are adaptively controlled and will range from ms to minutes. The RMS simulation mode is preferable used when simulating large interconnected system with hundreds or thousands of buses and machines. Besides the classical positive sequence representation, a full abc-phase system model can be utilised allowing to simulate any kind of unbalanced operation conditions incl. multiple faults.

The provided models can also be used for the EMT simulation mode without any further modification. In this case, the user must initialise the simulation with the 3-phase system representation in EMT mode which will then cover the instantaneous value analysis (comparable to EMTDC, ATP, etc.) featuring the analysis of switching transients, SSR or ferroresonace effects or e.g. to design the PWM digital control and protection systems. Of course, one of the most beneficial effects is that there is no need for duplication of model setups for different programs as PowerFactory can fully cover all dynamic and transient aspects on basis of the same system modelling setup.

In general, the user has full flexibility in modelling his specific control and protection systems using the graphical DSL block diagram approach. Both, analogue as well as digital control systems can be modelled to any required level of detail. Optional, integration of manufacturer specific code (e.g. C++) is supported.

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