  This paper studies control interactions between grid-forming (GFM) converters
exhibited by power and frequency oscillations in a weakly connected offshore
wind power plant (WPP). Two GFM controls are considered, namely virtual
synchronous machine (VSM) and virtual admittance (VAdm) based GFM. The GFM
control methods are implemented in wind turbine generators (WTGs) of a verified
aggregated model of a WPP and the control interaction between these GFM WTGs is
studied for several cases: cases with the same GFM control methods, and cases
with different GFM control methods. A sensitivity analysis is performed for the
observed oscillations to understand which system parameter affects the
oscillations the most. Several solution methods are proposed and the
inapplicability of some of the conventional solution methods are elaborated in
this paper.
