DC Voltage Stabilization Of On-line UPS Based On Multivariable H∞PI Control

Power electronics is vigorously developing and becomes a discipline that combines various technologies. It is especially meaningful to research the dynamic quality, stability, robustness in power electronic system by the control theory. It is attractive and promising to model the topologies of the power electronic circuit and consider them as a whole control system for our research. This thesis is mainly about the problem of the modeling and controlling of DC-DC converter in the on-line UPS. The following are the main contributions of this thesis. 1.The thesis summarizes the main closed-loop control methods and the modeling methods of PWM DC-DC converters and presents the prospect of their future development. For the typical boost converter of the on-line UPS, we establish the small signal model of the main circuit containing the parasitical parameter by the state average method. This is the basis of our further design of the closed-loop control circuit. 2. The problem of PI controller design for the multi-input and multi-output system is transformed to that of static output feedback controller design via the new state variable. As to the problem of the static output feedback, a new LMI-based sufficient condition of the controller is presented in this thesis. We can gain the multivariable PI controllers just solving one LMI inequality. The numerical example is provided to illustrate the proposed design approach. 3.The H_∞ robust control is able to solve the multivariable problem, also the control problem characteristic of the modeling error, parameters uncertainties and unknown perturbation, Its application research in the power electronics is beginning now. Considering the characteristics of the PWM DC-DC converters, a multivariable PI controllers which is based on H_∞ Performance Index is designed. The controller sampled the inductance current and the capacitance voltage meantime to control the duty-ratio of the PWM Boost converter, the simulating result proves that the new control strategy is effective to regulate the output voltage under the input voltage and load perturbation.