Effect of constant power load models on the stability of isolated Microgrids

The loads that can be found in microgrids have been changing over the years and the problems they cause have grown in complexity. For example, some of the loads present in this type of networks behave like Constant Power Loads (CPL), among which are the tightly regulated electronic converters, which have a quick response and a low output fluctuation. The problem with this type of load is its negative incremental impedance characteristic, which may cause instabilities in the power network with multiple power electronic converters. This work presents a study about the influence of both a dynamic and a static CPL in an isolated microgrid. To achieve this, the DIgSILENT Power Factory software is used to simulate the Huatacondo microgrid located in northern Chile. The results show that, when the load is modeled as constant power, both the voltage and frequency response to disturbances is worsened with the use of constant-impedance type loads. We conclude that electronic type loads, which have CPL behavior, could bring stability issues in isolated microgrids.