The Design and Implementation of a PLC Based Gas Turbine Controller for a Shipboard Application

A paper will be presented describing the design and development of the Gas Turbine Local Controller replacement used on the Magnetic Minesweeping Gas Turbine Generator (MMGTG) on the US Navy MCM-1 Class of ships. The advent of processor based controllers including PLCs has provided a low cost alternative for control system upgrades when faced with increasing maintenance costs and obsolescence issues of analog and hard relay logic control systems. The replacement controller is a Programmable Logic Controller (PLC) based system linked to a flat panel display and a supervisory control system. A MMGTG during pulsing operations applies a severe load transient cycle to the gas turbine for the fuel control to meet in a stable and safe manner. The algorithms which employ an adaptive Proportional Integral Derivative (PID) loop control structure with internal limiting constraints based on engine state are used to manage these transients, power turbine entry temperature and a wide range of steady state operation. The controller includes logic for alarming, start/stop and automatic shutdown. The design of the hardwired automatic shutdown logic integrated to the PLC will be presented. The control system design will be described in terms of its integration to a supervisory network, local control functionality and shipboard considerations. The Human Machine Interface screens of the flat panel display and their design are also considered.