The power factor correction and harmonic reducing capacitors on switched power supplies and UPS systems (especially better quality ones) have a disturbing tendancy to excite induction motors, allowing them to act as generators until all their kinetic energy is spent. In the case of large chillers, you have to consider the KE of all that water, too, and any KE of the machinery plant motors are connected to...
This generally has a very bad affect on the motors and, well, pretty much everything else connected to the bus. Hopefully the engineer took things like this into account when designing the plant, but it's almost impossible to accurately model and predict things like this.
