Research On The Integrated Conrol System Of Microturbine Power Generation

Micro-turbine generator (MTG) is a novel power generation system, whose main advantages are clean, reliable and multipurpose. MTG is applied in the fields such as distributed power generation systems, combined cooling-heating systems. Furthermore, this system can be taken as backup power supply, mobile power supply or special military high performance mini-station. MTG has great potential in application and important worth in research.Relying on national "863" project "100kW-level micro-turbine development (2002AA503020)" and "research of energy-saving technology based on electric drive and control system (2006AA04Z183)", the whole process including MTG start-up, running and power conversion is studied in this thesis. The integrated control system is constructed. The nonlinear dynamic mathematical model of MTG is formulated. The adaptive fuzzy Hx control of speed is proposed. In order to improve the quality of MTG power conversion and quality of power supply, the adaptive control strategy of high-frequency PWM rectifiers and the decoupling control strategy of three-phase four-leg inverters based on impedance transformation are proposed. Finally, we developed a control system of gas turbine and an electric power converter system.With respect to the integrated control system, we integrate start-up control, speed control, fuel pressure control, rectifier control and inverter control into the gas turbine control system by analyzing the MTG structure and control goal. Finally, overall subsystems are coordinated into the central control unit and the integrated micro-turbine control system is constructed. According to the principle of energy conservation, quality conservation, gas turbine thermodynamic theory and the control objective of the national "863" project, the system relationship equations for the variables such as gas turbine speed, exhaust temperature, turbine inlet pressure, turbine inlet temperature and compressor exit pressure are derived through the mechanism analysis of gas turbine. Then, a nonlinear state space equation for turbine speed, turbine inlet pressure and exhaust temperature is described. Meanwhile, the voltage equation, flux linkage equation, current equation, electromagnetic torque equation, motion equation and power equation is established in the dqO frame for integrated permanent magnet synchronous generator in the micro-gas turbine.In the control of gas turbines, the tracking differentiator is embedded in speed reference channel and feedback channel for suppress electromagnetic disturbance due to integrated control. Since the electromagnetic interference frequency is measurable and its amplitude is bounded, the non-linear saturation function in the tracking differentiator is replaced by a linear function. A fast-tracking differentiator is re-constructed to reduce the tracking delay. As the gas turbine dynamic model is very complex and has large uncertainty, the adaptive fuzzy control strategy of speed with H∞performance is proposed via linear matrix inequality technique for MTG based on Lyapunov stability theory. At the same time, a robust adaptive compensator is derived to eliminate the effect of the approximation error and external disturbance and guarantee the closed-loop system stability and good tracking performance. Simulation results show that the proposed hybrid control strategy can satisfy the requirement of the real-time control, speed tracking and suppression of electromagnetic disturbance. It is easy to be implemented in engineering.In the control of PWM rectifier, a PWM rectifier model is formulated and a power control scheme is applied by analyzing the principle of PWM rectifier and the permanent magnet synchronous generator model. Considering the features including the small capacity of MTG system, the load fluctuation and the uncertain load condition in AC-DC power conversion process, an adaptive control H∞strategy in the sense of Lyapunov stability is proposed for DC link voltage based on the power control method. Through automatic compensation for load changing, a stable DC link voltage and high power factor can be achieved. The simulation results show that the proposed scheme is effective and practicable.In the control of three-phase four-leg inverters, decoupling control strategy of three-phase four-leg is proposed based on the internal impedance transformation. The inverter and its output filter are regarded as an integrated inverter power supply to modeling and control as a whole unit. After equivalent transformation, the impedance of zero-leg is transform into zero and the others are reduced to a lower equivalent impedance value. The three-phase four-leg inverter is decoupled into three independent single-phase inverters which can be controlled by single-phase inverter control method. In this scheme, an amplitude-phase multi-loop system is applied. Therefore, it will not only enable the inverter operate independently, but also connect to grid by tracking the frequency. Advantages of the four-leg inverter structure are exerted particularly for unbalanced and non-linear load. The simulation results show that the control method is correct and effective.Finally, the prototypes of MTG control system, PWM rectifier and three-phase four-leg inverter are developed respectively. In the 100kW MTG experimental platform, experiments are carried out in the whole process of power generation including start-up, ignition, accelerating, off-line and generating. The experimental data and experimental waveforms show that MTG integrated control system and its control strategy have achieved the expected goals.