Modeling diesel generators for weak and strong grid conditions: Emphasis on LVRT compliance

Diesel generator is a prime mover based distributed energy resource (DER) popular in generation deficient regions. This paper deals with the analysis of critical requirements of diesel generator connection requirements for selected grid codes, namely German Grid code and Western Power Australia, as they characterized as imposing most stringent requirements for generator grid interconnection. Among all the requirements, low voltage ride through (LVRT) capability requires that the grid connected generator has to maintain its connection during the fault conditions in compliance with the defined LVRT profile. LVRT capability for a prolonged time duration leads to rotor heating. This is one of the most demanding requirements and it is important to analyze the LVRT characteristics during the modeling phase of a diesel generator system. To study strong and weak grid conditions, a single machine connected to an infinite bus model has been developed along with a set of test cases pertaining to the grid codes under study. The simulations were performed and effects of transmission line lengths, meshed and radial network configurations on the LVRT capability were assessed for various ratings of generators. The observations of the simulations are presented and discussed.