A Study on Single-phase AC-DC Converter using LMI-based Robust Control

Electricity generation and distribution in Cambodia take the form of alternating current, but the electrical loads currently have a direct current supply source. Therefore, the AC/DC converter has been studied and developed, which has two development procedures: Uncontrolled Rectifier and Controlled Rectifier.

This thesis describes the LMI-based robust control procedure in a single-phase AC-DC converter for a receiver as a resistor. The control system used in the AC-DC converter has two parts: inner-loop robust control and outer-loop conventional PI control. For inner-loop robust control, a state feedback controller with integrals is used in the DQ-synchronous frame. The set of stabilizing gain of this subsystem is determined by the LMI based on the improvement of the system transient response time, whether there is a change in the load level or a variation of the L-filter’s parameter value either. The outer-loop conventional PI is used only to improve the steady-state of the voltage, i.e. to reduce its steady-state error.

As a result, it is found that the operation of this single-phase AC-DC converter is optimized, which can convert 220 VAC to 450 VDC, despite variations in load resistance and L-filter parameter values. On the other hand, the transition of the signal from transient response to steady-state response is a short duration.