Presenting a new structure for interlinking converter in hybrid AC-DC microgrids to improve voltage quality

Abstract

In this paper, a new structure is presented for interlinking converter (IC) to improve voltage in hybrid AC-DC microgrids. This structure consists of series IC (SIC) and a parallel IC (PIC) parts. The PIC is responsible for exchanging the power between sub-grids and decreasing voltage unbalance indices. Based on the free capacity of PIC, voltage unbalance compensation reference is calculated on the AC subgrid side. In the series part of IC, any kind of voltage disturbance is compensated for the sensitive load. In order to increase the speed of dynamic response and to decrease the loss in SIC, the resistor of output filter is removed and then, fluctuations are damped in an active way in the control system. This is carried out through feeding back the current of the capacitor of the output filter and applying it to the control system, and using the current mode control in inner loop which improves the stability. Proportional-resonant and proportional-differential controllers are used in the control part of SIC. Therefore, proper tracking of the reference signal is guaranteed. Results obtained from the simulation of the case study system in MATLAB software verify the capabilities of the proposed approach.