Wind turbine generators (WTGs) are nowadays mainly connected via a widespread
collector-system network of medium-voltage (MV) subsea cables. The voltage is
then stepped up, and the wind power plant (WPP) is connected to the power grid
through long high-voltage (HV) cables, which can be either a high-voltage
alternating current (HVAC) or a high-voltage direct current (HVDC) transmission
system. This grid connection system is still challenging to the industry from a
harmonic generation, propagation and stability perspective.
it is of great importance to investigate how a certain WTG or a group of WTGs
interacts with the various elements of the WPP grid connection system, including
the MV cable network, park transformer, HVAC export cable and shunt components
such as the capacitor banks, shunt reactors, static VAR compensator (SVC),
static synchronous compensators (STATCOMs), etc.
This paper presents
potential harmonic problems and the various sources of such problems in large
WPPs, as well as shows optimised harmonic mitigation methods. The harmonic
problems (see Figure 1), such as harmonic resonances and emission sources as
well as harmonic stability, are identified. Also, modern preventive and remedial
harmonic mitigation methods (see Figure 2), in terms of passive and active
filtering, are described.
It is shown that WPP grid connection system
components, such as long HVAC cables and park transformers, can introduce
low-frequency resonances, which can affect WTG control system operation and
overall WPP stability as well as excitation of resonant circuits within the WPP
grid connection system, causing significant harmonic distortion.
emphasised that there is a potential in terms of active filtering in modern
power converters, eg in WTGs, STATCOMs or HVDC stations utilised in large,
modern WPPs. It is also emphasised that the grid-side converter controller
should be characterised by sufficient harmonic/noise rejection and adjusted
depending on the WPP to which it is connected.