Design of a Multivariable Decoupling Controller for Constant-Temperature Mixing System in Marine Intercooled Cycle Gas Turbines

Abstract This study addresses the challenge of stabilizing cooling seawater temperature and liquid level in a marine intercooled gas turbine seawater heat exchanger by proposing a multivariable decoupling control strategy. A mathematical model of the constant-temperature mixing (CTM) system is developed, and pseudo-control variables are introduced to decouple the strongly correlated multi-input multi-output (MIMO) loops. Incremental proportional-integral-derivative (PID) control algorithms are designed for regulating seawater inlet temperature and mixing tank level. Experimental validation on a marine intercooled gas turbine test platform demonstrates that the proposed controller achieves effective decoupling, with temperature deviations confined within ±1.0 °C and liquid level fluctuations below ±0.1 m under varying operational conditions. The results highlight the controller's robustness and practical applicability in complex marine environments.