In this paper we present a supervisory strategy for load/frequency control problems in networked multi-area power systems. The scheme consists of modifying the nominal frequency set-points and adjusting offsets on the nominal Automatic Load-Frequency Control (ALFC) laws of each area in order to avoid operative constraints violations in response to unexpected load changes and/or faults/failures. This aim is accomplished via a recent predictive control approach named Parameter Governor, which joins in a general framework Reference and Offset Governors actions. The effectiveness of the strategy is demonstrated on a two-area power system subject to coordination constraints on maximum frequency deviations and generated and distributed inter-area powers.