Dead-time compensation in three-phase grid-tied inverters using LQG multivariable control

Area of Science:

• Electrical Engineering
• Power Electronics
• Control Systems

Background:

• Dead-time is a critical disturbance in voltage-source inverters, causing low-order harmonics.
• These harmonics degrade the quality of power injected into the grid.
• Existing methods struggle to effectively compensate for these dead-time effects.

Purpose of the Study:

• To propose and validate a Linear Quadratic Gaussian (LQG) multivariable control approach.
• To compensate for dead-time effects in three-phase grid-tied inverters.
• To significantly attenuate dead-time introduced harmonics and improve power quality.

Main Methods:

• Developed a nominal multivariable model for a three-phase grid-tied inverter in a synchronous reference frame.
• Designed an LQG controller for robust stability and disturbance attenuation.
• Validated the controller's performance using a detailed MATLAB/Simulink model of an experimental setup.

Main Results:

• The proposed LQG controller demonstrated significant attenuation of dead-time introduced harmonics.
• Achieved a Total Harmonic Distortion (THD) of approximately 5% for grid-injected currents.
• The control approach ensures robust stability and high bandwidth for the closed-loop system.

Conclusions:

• The LQG multivariable control effectively compensates for dead-time effects in three-phase grid-tied inverters.
• The proposed method meets stringent grid interconnection standards like IEEE 1547.
• This approach offers a robust and high-performance solution for improving inverter output quality.