Preventing overvoltages in PV grids by integration of small storage capacity

Abstract

The rapidly growing amount of distributed generation in low voltage distribution grids issues some undesired side effects. Simultaneous power injection may cause a serious voltage rise along the feeder. These overvoltages may not only damage critical loads but also switch off PV inverters causing loss of green energy at the most productive moments. This paper discusses the origin and different possibilities to limit this induced voltage rise. The option of introducing local energy buffering is further elaborated. The relation between buffer size and overvoltage reduction is presented for a typical Belgian residential distribution feeder. The influence of buffers along the feeder is calculated by working with synthetic load profiles and solar irradiation data

Evaluation of voltage regulation mitigation methods due to high penetration of PV generation in residential areas

“…With respect to the momentary RMS value of the grid voltage, the national grid operators specify different limits (in Greece for example, a PV inverter should be disconnected from the grid within 0.5s if the momentary grid voltage is larger than +15% or lower than -20% of its nominal value and can be reconnected 180s 3 after the grid voltage returns within these limits). Therefore the important point is that when overvoltage happens, inverters must be disconnected and this means energy generation loss during the most productive hours of a day, while the required switching may cause voltage oscillations by itself and more losses [2], [20]. As a result, a significant amount of possible energy output will be lost in a clear day due to the high grid voltage, particularly under the high concentration of the grid connected PVs [20], [21].…”

“…The grid impedance at the PCC is another important parameter to be calculated and monitored which may exceed the permitted limits of grid codes [16]. When the grid impedance increases, for the same amount of injected current, the voltage will rise [2], [13], [14].…”

“…In such situations the grid impedance, which is observed from PCC, will increased. From the inverter side, which is voltage source and current control, when the impedance increases for same amount of current injection, a rise in voltage occurs [2].…”

“…Having steady and reliable performance in large-scale transmission systems, does not necessarily mean that same performance can be achieved in a geographically small distribution 2 system. Currently few detailed analyses are available on this regards.…”

Test field for LV distribution systems

“…also impose additional stress to the grid. [11] The previous does indicate some of the research topic initiated by the authors. However this paper is also an open invitation to third parties for collaborated research.…”