Research On Modeling And Direct Power Control Of The Stirling Linear Generator

The world’s energy crisis is highlighted in recent years. As replacement, the development of solar energy and other renewable energy has become the urgent attention. The solar dish-Stirling system has the highest efficiency and facilitate modular deployment in solar thermal utility, with tremendous potential application prospect. This thesis is an interdisciplinary subject of electrical engineering and thermal engineering. It takes the Stirling permanent magnet Linear Generator(SPMLG) as the research object which applied for the solar dish-Stirling system. On the Basis of the SPMLG system’s operating principles, this thesis analyzes the thermoelectric system working characteristic and establishes the generator system mathematical model. Direct power control strategy is used to control the SPMLG system in order to guarantee the stability of the output dc-voltage and generator efficiency. This dissertation is focusing on the following key points of SPMLG control system:(1) The SPLMG system structure is studied. By deducing the working principle of stirling engine and permanent magnet Linear Generator, we get the mathematical model of the whole system.(2) By studied the dynamics equation of SPLMG, observed the system under a normal sunshine day and analyze the factors which influencing the Stirling machine work efficiency. Put forward the pressure control to maintain the optimal efficiency.(3) The highest efficiency conditions of SPLMG is studied in the ideal conditions, Put forward the direct power control strategy to control the generator, in order to achieve unit power factor and the optimal efficiency purpose.(4) The thesis discussed the principle and structure of traditional Direct Power Control(DPC) system. The traditional DPC has the problem of time delay and switching table is not fixed. In order to improve the dynamic response, a fuzzy PI controller is designed in dc-voltage control loop.(5) To improve the drawbacks of the traditional DPC strategy, the paper presented a predictive algorithm scheme and a model predictive scheme which combined with space vector width modulation(SVPWM). Through the predictive of active power and reactive power value in the next moment, the time delay is eliminate in PDPC scheme. Aim to minimum power error, objective function and optimal solution are obtained in MPDPC scheme, the control method is to solve the optimal solution of the objective function. SVPWM used to order a constant frequency.(6) Both traditional DPC and the two predictive DPC methods of SPMLG system developed in this work have been simulated using MATLAB/Simulink, through the comparison of the three methods, the effectiveness of the proposed control strategies are verified by the simulation results of prototype system.