Aggregate Model of Parallel Distributed Energy Resources Controlled using Virtual Admittance

The increased number of distributed generation sources in distribution networks in recent years has emphasized the importance of their accurate and computationally efficient modelling. The development of efficient models becomes more difficult and complex with the introduction of novel controllers that aim to support the grid, often emulating the operation of passive circuit elements. One of such controllers has been recently proposed that emulates the operation of an admittance to support the voltage at the point of the converter grid connection. In this paper, an aggregate model of distributed energy resources controlled using virtual admittance approach and connected in parallel is derived. The resemblance of the controller to classical circuit elements is used to obtain an equivalent circuit for each converter including its controller part and the distribution line connecting it to the main grid. Then, circuit analysis techniques are applied to synthesize the aggregate model of all the parallel converters in the network, simplifying the assessment of their combined effect on the rest of the network and reducing the computational burden. Simulation results from Matlab and its SimPowerSystems toolbox are used to validate the accuracy of the proposed model.