DS-Based 2-DOF PID Controller of a Regasification System for LNG-Fueled Marine Engine

Abstract

As international regulations on greenhouse gas emissions are becoming stricter, the development of eco-friendly main engines is required for ocean-going ships. To use cryogenic LNG as a fuel for marine engines, it has to be converted to gas. This processing device is called an LNG regasification system. This paper presents a DS-based PID controller for glycol temperature control of a regasification system for LNG-fueled marine engines. In controller design, linear PID controllers have something of a catch-22 relationship: Fast response requires a large gain, which results in a large overshoot. To solve this problem, a DS-based 2-DOF PID controller is considered, which consists of a PID controller to reject disturbances in regulatory response and a set-point filter to reduce overshoot in servo response. The controller design focuses on improving disturbance rejection performance. The DS method is based on comparing the desired closed-loop characteristic equation with the closed-loop characteristic equation consisting of a control object and PID controller. The proposed controller is applied to the glycol temperature control of the regasification system for LNG-fuel marine engines, and its performance is compared with existing methods to show its effectiveness and applicability.