Innovations on the control of VSC-based dc-links connecting distributed generation to the grid

The fully controlled power electronic devices used in power systems have substantially change the control capabilities of the grid. In this field, voltage source converter (VSC)-based dc-links play a key role in controlling power and operating the electricity grid in an efficient and reliable manner. Since VSCs introduce dominant nonlinearities in the system model, the challenging issue of designing as simple as possible decentralized controllers that meet the desired tasks is considered in this paper. In contrary to the conventional notion where either complex design methods or techniques that cancel the nonlinear terms are applied, in the present work, an advanced nonlinear analysis is deployed with the proposed current controllers to be of simple proportional-integral (PI)- or proportional (P)-type. Incorporating the proposed controllers into the system, a nonlinear model is derived which is then analyzed by applying advanced Lyapunov techniques. The system is examined around any nonzero reference equilibrium by proving that the input-to-state stability (ISS) property holds true and convergence to this equilibrium is guaranteed. The control design is integrated by implementing outer-loop slower PI controllers in cascade and its performance is evaluated by extensive simulations.