Active and Reactive Power Sharing of Two Parallel Inverters Using Combination of Virtual Synchronous Generator and Droop Control.

The concept of active, reactive, and harmonic distortion powers sharing of two inverters connected in parallel to the main grid becomes a very important problem for security of supply. The first contribution presented in the paper is the combination of a virtual synchronous generator (VSG) and a nonlinear current control technique. The VSG controls the active powers sharing between the two inverters and contributes to the reduction of the frequency deviation at the point common coupling (PCC) during the variation of the load or the injection of solar PV active power to the grid. The VSG improves the inertia and damping of the system and makes the system robust with better frequency stability. The Droop control estimates the active power of the power of the battery energy storage system (BESS), the VSG injects this active power estimated at the PCC point to reduce the frequency deviation. The second contribution concerns the non-linear control making it possible to compensate and to share the current harmonics between the two inverters and allows the reactive power sharing between the two inverters. The concept of combining a VSG and nonlinear control offers several possibilities and makes it possible to decouple the active and reactive powers sharing of the two inverters. The nonlinear control approach guarantees reactive power compensation in the grid side. Finally, the results obtained by simulation show the relevance of the proposed approach of power sharing, reduction of frequency deviations and system stability robustness.