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Abstract:
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Wind turbine power capability is an essential set of
data for both wind turbine manufacturers/operators and transmission
system operators since the power capability determines
whether a wind turbine is able to fulfill transmission system reactive
power requirements and how much it is able to provide
reactive power support as an ancillary service. For multimegawatt
full-scale wind turbines, power capability depends on converter
topology and semiconductor switch technology. As power capability
limiting factors, switch current, semiconductor junction temperature,
and converter output voltage are addressed in this study
for the three-level neutral-point-clamped voltage source converter
(3L-NPC-VSC) and 3L Active NPC VSC (3L-ANPC-VSC) with
press-pack insulated gate bipolar transistors employed as a gridside
converter. In order to investigate these VSCs’ power capabilities
under various operating conditions with respect to these
limiting factors, a power capability generation algorithm based on
the converter electrothermal model is developed. Built considering
the VSCs’ operation principles and physical structure, the model is
validated by a 2MV·A single-phase 3L-ANPC-VSC test setup. The
power capability investigations regarding a sample grid code’s reactive
power requirement showthat 3L-ANPC-VSC results in 32%
better power capability than 3L-NPC-VSC at the switching frequency
of 1050 Hz. Furthermore, 3L-ANPC-VSC with 57% higher
switching frequency (1650 Hz) and 33% smaller switching ripple
filter can yield close power capability compared to 3L-NPC-VSC
with 1050 Hz. |
