  The design of a power buffer to mitigate the negative impact of constant
power loads on voltage stability as well as enhancing ride-through capability
for the loads during upstream voltage disturbances is examined. The power
buffer adjusts its front-end converter control so that the buffer-load
combination would appear as a constant impedance load to the upstream supply
system when depressed voltage occurs. A battery energy-storage back-up source
within the buffer is activated to maintain the load power demand. It is shown
that the buffer performance is affected by the battery state of discharge and
discharge current. Analytical expressions are also derived to relate the
buffer-load ride-through capability with the battery state-of-discharge. The
most onerous buffer-battery condition under which the load-ride through can be
achieved has been identified.
