Abstract:
The parallel ac and dc nature of most the distributed energy sources and loads, enforces the idea of forming hybrid ac/dc distributed generation (DG) systems. Such a hybr...Show MoreMetadata
Abstract:
The parallel ac and dc nature of most the distributed energy sources and loads, enforces the idea of forming hybrid ac/dc distributed generation (DG) systems. Such a hybrid structure demonstrates the main advantages of ac and dc distribution networks, such as easier renewable energy integration and less power conversion losses. A typical hybrid ac/dc DG system consists of: a dc-side, an ac-side and an interlinking voltage source inverter (VSI) as power interface between the two sides. Dc and ac resistive and constant power loads, as well dc and ac distributed energy resources (DERs) are incorporated. To enhance system reliability and dynamic performance, energy storage devices are connected to the dc link, allowing the power to flow in both directions, via a bidirectional boost converter. A challenging issue in the design of a hybrid ac/dc DG system is to apply effective, reliable and robust control in order to ensure stable operation at the desired conditions and to avoid adverse impacts between the different parts. In this frame, opposite to the small signal analysis, existing in the literature, in this paper, a nonlinear control design and analysis of the complete hybrid system is deployed. Based on the accurate system model, cascaded-mode proportional-integral (PI) controllers are designed and suitably implemented to the power electronic interfaces in order to regulate both the ac and dc voltages as well as the ac-side frequency. The stability analysis conducted on the nonlinear system model with the inner-loop current controllers involved, is based on advanced Lyapunov techniques and as proven in the paper guarantees closed-loop stability and convergence to the desired nonzero equilibrium. The entire hybrid system is simulated under DER and load rapid changes with the results to verify the smooth and robust behavior.
Date of Conference: 03-06 July 2017
Date Added to IEEE Xplore: 20 July 2017
ISBN Information:
Electronic ISSN: 2473-3504