Modeling and control of fluid flow networks with application to a nuclear-solar hybrid plant

Abstract

Fluid flow networks (FFNs) can be utilized to integrate multiple once-through heat supply system (OTHSS) modules based on either the same or different energy resources such as the renewable, nuclear and fossil for multi-modular and hybrid energy systems. Modeling and control is very important for the safe, stable and efficient operation of the FFNs, whose objective is to maintain both the flowrates and pressure-drops of the network branches within specific bounds. In this paper, a differential-algebraic nonlinear dynamic model for general FFNs with multiple pump branches is proposed based on both the branch hydraulics and network graph properties. Then, an adaptive decentralized FFN flowrate-pressure control law, which takes a proportional-integral (PI) form with saturation on the integral terms, is established. This newly-built control not only guarantees satisfactory closed-loop global stability but also has no need for the values of network hydraulic parameters. This adaptive control is then applied to the flowrate-pressure regulation of the secondary FFN of a two-modular nuclear-solar hybrid energy system and numerical simulation results show the feasibility and high performance of this network control strategy. Due to its concise form, this new flowrate-pressure FFN controller can be easily implemented practically.