Numerical tools and models for Monte Carlo studies of the influence on embedded generation on voltage limits in LV grids

If significant amounts of distributed electricity generation (DG) units are embedded in the low-voltage (LV) distribution networks, a major issue is to keep the voltage between the EN 50160 limits. This technical constraint is often considered to be a major limitation to the admissible level of embedded generation in an LV network. This paper deals with a study of the influence of embedded generation. The starting idea is that considering the worst-case load and generation combinations is too pessimistic. Therefore, a stochastic approach has been chosen. Loads and embedded generation production are modeled as stochastic processes whose characteristics depend on season and peak/low demand periods. Monte Carlo simulations yield the amount of time where the voltages are out of limits at one point in the network. The simulation results can be efficiently interpreted using the concept of critical network length and show how it is affected by the embedded generation. A reference LV radial distribution configuration is taken and different values of specific area load densities (kW/km/sup 2/), cable-loading densities (kilowatts/kilometers), and LV network lengths are considered. For the evaluation of the networks currents and node voltages, a simple current injection method was chosen for its efficiency for studying the radial distribution network operating in the voltage limits (limited voltage regulation). The method was adapted for distributed loads. To conclude, a specific case with a substantial amount of additional DG is considered.