Instantaneous power-based current control scheme for VAR compensation in hybrid AC/DC networks for smart grid applications

An important feature of grid-connected DC microgrids is the ability to inject or suck power from the grid based on the generation and loading conditions. Power flow from the AC to DC grid is important to cover any deficiency in the demand in DC grid. Power flow from the DC to AC grid is needed when there is an excess power from renewable energy sources on the DC bus. To allow this bidirectional power flow, a pulse-width modulation controlled voltage source converter is used as an interface between the DC microgrid and the AC main grid. The bidirectional converter controls the active power transferred in both directions while operating at unity power factor. In this study, a current control approach based on the instantaneous synchronous detection theory has been used to control the power flow in both directions. The proposed current control scheme is verified through MATLAB simulation and the simulated results are also validated experimentally using a prototype controlled by dSPACE digital signal processor. The simulated and the experimental results show that the proposed scheme offers regulated DC grid voltage and nearly unity power factor for wide load variations. Results have proven excellent performance in steady and transient states.