  To investigate the effect and ability of FACTS devices using the Fast and
Flexible Holomorphic Embedding technique (FFHE), it is necessary to develop an
embedded system for these devices. Therefore, this paper presents FFHE based
embedded system for STATCOM and UPFC. The embedded system is also proposed for
their controlling modes. The introduced embedded system for STATCOM and UPFC is
flexible which allows to take any state as an initial guess instead of fixed
state, which leads towards the reduced runtime and decreases the required
number of terms, as compared to the standard Holomorphic Embedded Load-Flow
method (HELM). To demonstrate the effectiveness and practicability, the
proposed models of STATCOM and UPFC have been tested for several cases.
Further, the developed recursive formulas for power balance equations, devices'
physical constraints, and their controlling modes are thoroughly investigated
and examined. From several tests, it is found that the proposed embedded system
requires less execution time and reduces the error at higher rate.
