Photovoltaic Fuel Cell Hybrid Power System Control Design And Simulation Research

The research for fuel cell and renewable resources technologies has gained momentum in recent years due to the ever-increasing environmental pollution and fossil energy shortage. Photovoltaic-fuel cell hybrid power systems have shown promising for electrifying remote and rural areas without the utility grid. The complicated power system can not easily supply sustained energy to meet the requirements due to the intermittent nature of photovoltaic energy, electrical load and heat requirement. This problem becomes the most important issue in the research. Although there are some demonstration projects and research results reported in the literature, there is little research on the sizing and control problem. The dissertation focuses on the sizing and control of a household photovoltaic fuel cell hybrid power plant, aiming to achieve a sustainable, highly efficient cogeneration to meet electrical and thermal energy requirements simultaneously. The studied power plant consists of a photovoltaic array, a proton exchange membrane fuel cell (PEMFC), an alkaline electrolyzer and an ultra capacitor. The main contributions and achievements are given below:With developing the model of the whole system for predicting the long term performance, the design methodology based on energy storage dispatching parameter and photovoltaic array size has been proposed. The developed model characterizing all the components and priority energy management is universal and accurate. The energy storage dispatching parameter has been defined, to characterize that the ultra capacitor and hydrogen energy storage (PEMFC and alkaline electrolyzer) balance the mismatch between solar power and user requirements. Given the energy storage dispatching parameter value, the monthly and annual average daily distributions of photovoltaic energy and load requirements are used to size the photovoltaic array and then the system configuration. The test sample has demonstrated the feasibility of the proposed sizing method. The simulations for the three distinguished configurations are compared to explore the configuration impacts on system performance and select the satisfying candidate one. The selected system configuration is used for further research.The control system of the power plant, consisting of the power and heat control layer and planning layer, has been researched. Using the block modeling methodology, its dynamical model is established to describe the characteristics of all the components. This dynamical model can be used for the control research.As the most complicated part of the control layer, the PEMFC control problem has been studied to regulate the process parameters such as oxygen stoichiometry, anodic hydrogen pressure and output current. The sliding mode control method and PID control method are used. The maximum power tracing controller of the PEMFC has also been designed with the sliding mode extremum seeking control method. The kind of adaptive tuning sliding mode control has been developed for the coordination control of output current and oxygen stoichiometry. The coordination control scheme is proposed that derives the reference signal of the oxygen stoichiometry controller from the input signal of the output current controller and tunes the parameters of the sliding mode output current controller according to the dynamical properties of the oxygen stoichiometry control. The simulation tests have demonstrated the satisfying dynamical performance and robustness of these proposed PEMFC controllers.The electrical power and heat control has been researched. The power control has been realized using the decentralized control scheme. The sliding mode controller for every component has been designed with the corresponding control goal derived from the power control of the whole system. And, thus, these component sliding mode controllers have been synthesized to obtain the electric power controller. The simulation tests indicate that the resulted power controller realizes the decouple control of the power plant, and the good dynamical performance and robustness have been achieved. The heat control has been studied after designing and modeling the heat recovery subsystem of the power plant. The temperature control of the alkaline electrolyzer and the PEMFC has designed using the sliding mode control method. The simulation results demonstrate the designed heat controllers meet the plant requirements. So, the power and heat control layer have been realized with the expected dynamical performance.The heat and power planning of the photovoltaic fuel cell hybrid power plant is considered in the end. The model predictive planning method is used for operation optimization of the power plant. Different from the reported optimization methods developed for the power and heat planning in the literature, the complicated optimization for this planning problem has been simplified to one multi-input nonlinear function only with invariable input constraints using the proposed method. Therefore the optimization can be resolved with the normal methods. The simulation results demonstrate that the proposed planning method make the generator stable, sustained with high efficiency.