gain
and phase stability margins of discrete system in Z-domain is
shown in Fig. 2. Gain margin is used to measure the absolute
stability in frequency domain and the degree to which the
system will oscillate without limit given any disturbance.
Phase margin is measures of stability in closed loop dynamic
control systems and indicates how far from instability region
or relative stability, the tendency to oscillate during its
damped response to an input, load or grid system change.