Multi-voltage level operation of DC loads in 3-pole PV-based DC microgrid

This paper proposes the concept of operating approximately equal distributed dc loads and flexible dc load respectively on low and high voltage levels without the employment of dc-dc converter in 3-Pole PV-based DC Microgrid (3-PPDM). The concept leverages on the two-equal centre-tapped capacitors on the dc link of PV generation system embedded to the grid via single-stage dc link and three-level Voltage Source Converter (3L-VSC), where three connecting poles (+P,gP,-P) are obtained for load connections. The essence of the concept is to reduce implementation cost by eliminating the use of dc-dc converters and still achieve desirable performance of the dc loads. The challenge of this concept during zero insolation which leads to violation of the set conditions for desirable operation of the microgrid was mitigated with the employment of modified Perturb & Observe Maximum Power Point Tracking (P & O MPPT) technique where zero output current of the PV is considered. Evaluation of the concept and modified P & O MPPT algorithm were carried out in MATLAB/Simulink and simulation results showed that the system performance is comparable to alternative approach, but with reduced number of components required for the microgrid implementation and significant reduction in complexity of the microgrid operation.