Power Injection by Distributed Generation and the Influence of Harmonic Load Conditions

The number of installed distributed generation (DG) in residential areas rapidly increases, specifically in the form of photovoltaics (PV), causing some undesired side effects such as voltage rise. Overvoltage can damage critical loads, but is also disadvantageous for the owner because inverters switch off in case of overvoltage, resulting in output loss. Since grid connected inverters essentially exhibit nonlinear behavior, harmonic interactions between large numbers of DG systems and the distribution network may occur. Also nonlinear loads inject harmonic currents and induce increased voltage drops over both phase and neutral conductors. This extra supply voltage drop can lead to an even more pronounced production loss of grid coupled inverters. This contribution gives some guidelines for the maximum power acceptance in a residential grid and the estimation of PV production losses due to overvoltage and discusses the influence of harmonic voltage drops.