Modeling and Control of Fluid Flow Networks with Application to a Nuclear-Solar Hybrid Plant

Zhe Dong,Yifei Pan,Xiaojin Huang,Yujie Dong,Zuoyi Zhang

doi:10.3390/en10111912

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.

Highlights

Distributed energy systems can be built by electrical interconnection of power plants through the grid [1] and can be built by thermal interconnection [2] of homogeneous or heterogeneous once-through heat supply system (OTHSS) modules based on fluid flow networks (FFNs)
Multimodular and hybrid energy systems can be built by integrating multiple homogeneous or heterogeneous OTHSS modules based on renewable, nuclear or fossil energy sources, where the module integration can be realized through FFNs
In the aspect of dynamical modeling, a simple control-design-oriented nonlinear differential-algebraic model for the FFNs with multiple pump branches is first proposed based on branch dynamics and network graph property

Summary

Introduction

Distributed energy systems can be built by electrical interconnection of power plants through the grid [1] and can be built by thermal interconnection [2] of homogeneous or heterogeneous once-through heat supply system (OTHSS) modules based on fluid flow networks (FFNs). OTHSS refers to a thermodynamic system composed of a heat source, primary coolant circuit(s) and once-through steam generator(s) (OTSG) or once-through heat exchanger(s) (OTHX), whose heat source can be fired-coal, nuclear fission reaction, solar and etc. The coolant inside the primary circuits is used to absorb the heat from the source and transfers it to the secondary coolant through OTSGs or OTHXs. The secondary coolant is injected to the secondary side of the OTSGs or OTHXs and is changed to be the satisfactory working fluid for driving different thermal loads such as a steam turbine. A thermally interconnected distributed energy system is called a hybrid energy system (HES) [16,17,18] if the heat sources of OTHSS modules are of different types, otherwise it is called a multimodular energy system

Methods

Results

Conclusion