Acausal Modelling and Dynamic Simulation of the Standalone Wind-Solar Plant Using Modelica

In order to design model-based controllers applicable to hybrid renewable energy systems (HRES), it is essential to model the HRES mathematically. In this study, a standalone HRES, consisting of a photovoltaic (PV) array, a lead-acid battery bank, a pitch-controlled wind turbine, and a three-phase permanent magnet synchronous generator (PMSG), supplies a variable DC load demand through two boost- and buck-type DC-DC converters. It is shown that the mathematical model of the HRES can be represented by a system of nonlinear hybrid differential algebraic equations (hybrid DAEs). The developed model in this paper employs the Modelica language that allows object-oriented and acausal modelling of the multimode systems. The OpenModelica environment is utilised to compile the model and simulate the system. It is shown that the simulation provides a sufficiently accurate prediction of all the differential and algebraic states including mode transitions. The results of the simulation show a good match with the information available in the components datasheet.