| The system of control and power conversion for micro-turbine is one of the critical subsystems of 100kW-level micro-turbine project supported by the national high technology research and development of China (863 Programme-2002AA503020,2004AA503020, 2007AA050501). The micro-turbine control and power conversion system with modular structure is a whole set composed of several parts which have special functions and interrelate to each other. The whole system is composed of the gas turbine control system, variable frequency soft start system, DC-DC power conversion system, the four-leg inverter with an electrical filter and so on. In this dissertation, intensive studies have been carried out around the above systems and engineering experiments for whole machine. Based on the SVPWM, the design methods for three-leg inverter and four-leg inverter are proposed. On the basis of fuzzy control theory, the control method for DC-DC buck chopper is studied. The power filter is presented according to circuit calculation and analysis. The turbine control and power conversion system are combined together as one system. Experimental results show that the system is stable and reliable and has excellent performance. The research results are meaningful for theory and engineering application. At present, five patents have obtained about this achievement. The main research contents are given as follows:1. For a nonlinear system with uncertainties as 100kW-level micro-turbines, the speed tracking control strategy is studied deeply using fuzzy adaptive control methods. Because the precise mathematical model of gas turbine system is hard to be established and the running processes are complicated under the varying load conditions, the system is a real-time system with the features of multi-parameters, strong coupling and complex lag characteristics, which would cause serious uncertainty for the practical system model. The approaches for nonlinear mathematical modeling are studied systematically in this work. First, some assumptions for modeling are presented through mechanism analysis based on turbine thermodynamical principles, and therefore the static relations among system variables are proposed. Then, concerning with the static relations among variables, nonlinear state space equations are derived. At last, the verification of the developed model system is performed by step response simulation experiments using the Matlab/Simulink. The results of model verification show that the responses correspond to the engineering expectations according to the parametric characteristics of the model system. The simulation results illustrate the correctness and effectiveness of the established model system.2. In view of the established model system of the micro gas turbine, that is, quasi-polynomial ordinary differential equations-QP-ODEs, the system stability at balance point is studied by using differential geometry theory. A new design method for control system of micro-turbine is proposed by analyzing the part stability or global stability of the system.3. On the basis of theoretical analysis about the 100kW-level high-speed permanent magnet motor/generator, practicable SVPWM is studied, a design method is proposed for micro-turbine soft start control system. In the proposed method, based on two reaction theory and SVPWM, the inductance in synchronous motor differential equations is not the function of rotor position any more, and therefore mathematical model for synchronous motor described by constant coefficients differential equations is established. The established mathematical model is simple and beneficial to the research on control method.100 kW-level high-speed permanent magnet motor variable frequency soft start engineering tests are had been done. The experimental results verify the correctness of the proposed soft start control system effectively.4. The fuzzy control system for DC-DC converter is studied intensively by using fuzzy control technology. A fuzzy control method for DC-DC conversion system is proposed based on the structure of controller, fuzzy control rules, the domain of variables, radio factors, the subject functions of the status, the fuzzy inference matrix, fuzzy judgments or decision. Comparing with PID control method, the proposed fuzzy control method raises system response speed greatly, realizes electrical energy bidirectional transmission. The engineering experiments had been done.5. In order to enhance reliability, a new method for DC-DC conversion system with online-multiple-hot-standby function is developed. Compared with the traditional method, the reliability of the system is increased more than three times. The correlation study is not mentioned in references.6. The four-leg SVPWM inverter is studied intensively in this dissertation. First, a control method for neutral point is presented by analyzing the switch status of four-leg inverter, and therefore the decoupling control strategy for four-leg inverter is proposed. As same time, the power filter for output of four-leg inverter is presented according to circuit calculation and analysis. Then, considering the reliability of the system, a four-leg inverter with function of online-hot-standby-redundancy is developed, and the correlation study is not reported yet. Last, the simulation study and the engineering experiments had been finished. The simulation and experimental results prove that the inverter can maintain symmetrical sinusoidal output voltages under unbalanced loads. The proposed control strategy has important value both for theory and in practical application.7. Engineering test research has been completed. Micro-turbine control and power conversion system is one of the most important subsystems of the micro-turbine project supported by the national high technology research and development of China (863 Programme). To ensure the project to be carried out, the micro-turbine control and power conversion system has finished the laboratory experiments in advance, and then some engineering experiments cooperating with micro-turbine had been done. These works not only include the determination of control parameters and analysis of practical test data for the micro-turbine control and power conversion system, but also include verifications for micro-turbine operating processes under variable load conditions... |
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