  This paper presents the design and analysis of a compensation method with
application to a 345 kV 480 MVA three-phase transmission line. The compensator
system includes a series injected voltage source converter that minimizes the
resonance effects of capacitor line reactance. This creates an ability to
compensate for the effects of subsynchronous resonance and thereby increase
line loadability and control real and reactive power flows. The granularity of
power flow control and simultaneous stabilization is achieved by the method of
direct decoupled power control (DPC). The design process is detailed with
respect to optimal response characteristics considering variations of line
parameters, realistic transformer impedances, and maximum ramp response rates.
Line effects are demonstrated in a PLECS model in MATLAB, and compensation
control system functionality is verified. A case study is provided of a 345 kV
transmission line from an EMTP simulation in PSCAD that accounts for
distributed parameter effects that are encountered in physical EHV transmission
lines. This demonstrates the improvement in stability to power system
transients as well as damping of power system oscillations.
