Towards More Accurate Load Modeling in Calculations of Transients in Energy Grids with Distributed Energy Resources

Abstract

Large-scale adoption of distributed energy resources (DER) in low-and medium-voltage energy grids necessitates calculating the transients for such grids, especially for their islanded operation. Parameters of transients depend both on the properties of generator sets (GS) deployed at distributed generation (DG) facilities; and on the properties of the load, given low mutual impedance and comparable total power. Low mechanical constants of inertia of the GS’s result in a significantly higher rate of change in the operating parameters in electromechanical transients, which may cause the GS, the energy storage, or the load itself to disconnect. In order to make a sound decision on how to organize power system protections, and to configure the automations in DER-enabled power systems correctly, emphasis should be made on more accurate load modeling. This will help avoid significant errors in transient calculations and ensure reliable operation of all types of DERs. This paper further substantiates the need to adjust for electromagnetic transients in rotors when modeling asynchronous motors in the context of their applications. The paper dwells upon the specifics of modeling asynchronous motors (AM) and synchronous motors (SM), and on how to reduce them to equivalents, which simplifies the preparation of calculation models whilst retaining the acceptable accuracy of their output.