Optimal current calculation for a PMSG based wind energy system integrated into an unbalanced weak grid

Abstract

Grid connection is an important consideration when it comes to integrating an energy source. A common problem with the existing wind energy conversion systems is that they are often located far from energy consumption centres. Owing to their remote location these systems are sometimes forced to connect with weak distribution networks which are usually designed for small linear loads. When the nature of these loads is changed, the voltage level at the point of common coupling may go above or below the nominal value which may result in power system instability. To improve the voltage variation, this study discusses an optimal current calculation technique based on Thevenin equivalent parameters of an electrical network. The functional capability of the technique is demonstrated with the help of a traditional converter topology utilised as a power conditioning system for a permanent magnet synchronous generator connected to a weak grid. The system in particular monitors a medium voltage distribution line, measures line load impedance and redistributes the currents in a way that provides maximised power transfer into a network with least incurred losses. A real-time controller with built-in data acquisition/field-programmable gate array modules is used for the execution of experimental investigations.