Stability Assessment of Isolated Micro-grids Powered by Distributed Combined Heat and Power Micro-units

It is expected that combined heat and power (CHP) micro-units will soon play a significant role in the energy supply of private households. To increase the reliability of the system the isolated operation of this micro-grid should be possible. It is assumed that the electrical load is the reference input variable of the local grid to reduce the necessity of electrical energy storages. The produced thermal energy will be stored. The paper presents a study of the voltage and frequency stability in micro-grids powered by CHP micro-units. The simulation model of the micro-co-generation plant is based on a combustion engine and brush-less synchronous generator. The example network represents an urban residential neighbourhood. The electrical household loads are based on probabilistic modelling, with high time resolution. Several scenarios for normal and disturbed operation are defined, which vary in electrical load, number and size of the CHP units and the generation schedule. For these scenarios the stability and voltage limits during normal operation and for selected three phase faults are investigated. The voltage and frequency stability of the micro-grid is determined by dynamic simulations.