Overview of the Legislation of DC Injection in the Network for Low Voltage Small Grid-Connected PV Systems in Spain and Other Countries

In recent decades there has been an increasing interest in the use of low voltage small grid-connected photovoltaic (PV) systems, conditioned by new incentives from distinct countries. An essential element in those systems is the inverter, that is, the element which converts, in an efficient way, sinusoidal AC current waveform at its output so that it may be connected and synchronized to the utility network. However, that conversion must meet some minimum quality criteria with respect to the harmonics current, DC injection and power factor. Precisely, this work studies the relation of the PV inverter with limits of DC injection in the network, in the AC side. This has been carried out by means of the compilation referring to DC injection for low voltage small grid-connected PV systems exclusively, as well as the international standards and effective legislation in six countries (the USA, Germany, Japan, Spain, Australia and the United Kingdom), where the grid-connected PV industry has experienced remarkable growth in the last 10 years.