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 worstcase 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 km2 ), cableloading 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.Index Terms-Concept of limit radius, current injection power flow, distribution network, embedded generation, Monte Carlo method, radial network, stochastic process.
The flux density harmonics in the air-gap of AC machines have many origins. They generate electromotive forces and current harmonics, Maxwell forces, noise and vibrations. The principle of the presented method is to use a new auxiliary stator winding, connected to capacitors. The induced current harmonics generate flux density components in opposition to the initial ones, creating a damping effect. The study presented in this paper concerns an induction machine and particularly focus on flux density harmonics generated by slotting effects. The method allows to reduce the sound pressure level main lines of about 15dBA. The vibrations are reduced too. Moreover the stator current harmonics are attenuated, and the power factor is significantly improved.
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