Modeling And Control Research For Molten Carbonate Fuel Cell Gas Turbine Hybrid Power-Generation System

Fuel cell and gas turbine (FC/GT) hybrid power-generation system with high efficiency and low emissions has been focused and developed all over the world. In the world, the demonstration hybrid power plant has been developed. In China, fuel cell gas turbine hybrid system is still in the early research stages.The work is supported by the national 863 scientific project item"Analysis and control strategy for 50 kW-scale molten carbonate fuel cells power generation system"and"Molten carbonate fuel cells–gas turbine hybrid system". According to some experiences on hybrid system in China and foreign countries, this dissertation realizes a molten carbonate fuel cell and gas turbine (MCFC/GT) hybrid power-generation system with good performances by simulation design, and makes it operate steadily by the integrated control, providing valuable instructions for developments and applications of hybrid power-generation technologies. The main achievements and contributions are summarized as follows:1. A dynamic model of MCFC/GT hybrid generation system is established. The topological structure of hybrid system based on bottoming mode is used by comparing with variable configurations. Firstly, the reduced lumped parameter DIR-MCFC mode is established. Then, based least square method and nonlinear least square method, the compressor module and turbine module are established respectively. The heat exchanger, catalytic oxidizer and bypass valve are modeled in several simulation modules according to the conservation law of mass and energy, and ideal gas law. At last, these separate modules are connected to build up the total MCFC/GT hybrid system dynamic model according to the designed topological structure. Simulation results show that, the model is able to and also enough to reflect all operating parameters and power output can be used in the simulation design, performance analysis and control research of the system. That lay a solid foundation for dynamic optimization and control research.2. The dynamic optimization problem is introduced in detail, and novel iterative genetic algorithm (NIGA) is proposed to solve the optimal operating trajectories for MCFC/GT hybrid generation system. The proposed algorithm is combined the iteration method and the novel genetic algorithm together. The algorithm is especially practical when the system's gradient information is unavailable. For the algorithm, the control variables are discretized firstly and the novel genetic algorithm is used to search for the best solution of the discretized control variables. Next, the benchmark is moved to the acquired optimal values in the subsequent iterations and the searching space contracted at the same time, hence the optimization performance index and control profile could achieve the best value gradually through iterations.The algorithm is simple,feasible and efficient. It avoided the problem solving large-scale differential equation group. That will help workers on the spot manipulate the hybrid system in practical application or act as the set points and the feed forward control inputs in order to closed loop optimized control.3. The hierarchical control design is proposed and tested for molten carbonate fuel cell gas turbine hybrid generation system to operate steadily. In this dissertation, for the heavy structure, many performance parameters and complex characteristics, the hierarchical control scheme of MCFC/GT hybrid system based on Multi-output Support Vector Machine Regression (MSVR) supervisor is proposed. Advanced compound control method is the basical control. The setpoints and the values of feedforward control are obtained from MSVR. That is hierarchical control proposed in this dissertation. Optimal control results were successfully modeled and predicted by means of MSVR supervisor. This facilitates optimal feed forward control moves and set points under varying process conditions. The experiment is implemented to illustrate the superiority of the MSVR compared to neural network and SVR. The system operation is separated to some basic processes including system power, fuel utilization, combustion temperature and MCFC temperature to design and test local control strategies (AZNPI feed back power controller, fuel flow controller based on the voltage feed back and QDRNN-PID decoupling temperature controller )firstly. Then, these controlled processes are integrated to realize the ideal steady operation of MCFC/GT hybrid system under the step power loads. The simulation results illustrate the effectiveness of controllers. The hybrid system can track the desired power with high system efficiency and main system parameters are all satisfied with the real online control of the system.