Power converters for the grid integration of PV systems

Abstract

In most applications of grid-connected PV systems, buck converter is usually used with Maximum Power Point Tracker (MPPT) controller to achieve maximum power transfer by controlling the duty ratio of its switch. However, it is important for buck converter to operate in continuous conduction mode (CCM) because it makes the control and regulation of the output voltage easy. It can be shown that by varying the inductance value of the inductor in the buck converter, one can control the operation to be in continuous or discontinuous region. So far, there has been some research going on for variable inductor to achieve maximum power point tracking, and using magnetic control to change the inductance in the variable inductor.

The student has proposed to replace the inductor in the buck converter by a variable inductor so that magnetic control can be used to vary the inductance of this variable inductor. Matlab software simulation has been completed to show expected waveforms and values before actual hardware part is realized. Results from hardware experiment showed that CCM can be achieved through proper adjustment of magnetic control, and values that are measured are well within the calculated range, similar to what has been achieved from the simulation results. Upon implementing this topology on upscale basis, it can reduce much energy losses from the converter side, enhancing its efficiency to deliver greater output power. At the same time, the controller can extend its operation to low insolation locations, and the overall inductor size can be reduced without affecting the operation at CCM through minimum inductance.