With the collaboration of Thiago Farias
In situations where photovoltaic systems are installed near the load and connected to Group A customers, who have both active power (kW) and reactive power (kVAr) measurements of the load, problems may arise related to the charging of “excess reactive power” by the concessionaire due to the measurement of a low power factor of the consumer unit.
This occurs because the photovoltaic plant starts to supply active power to the load and the reactive power continues to be supplied by the distributor's network. This causes the meter at the input substation to “see” a low power factor even without there having been a change in the reactive power supplied.
The idea of this article is to contextualize this subject and present a real case study, where this problem started to occur after the installation of a photovoltaic system in an industry.
Before clarifying important concepts for understanding this article, it is necessary to discuss that current inverters used in photovoltaic systems have the capacity to work with different power factor (PF) levels.
For commercial string inverters, commonly applied in mini-generation systems, the power factor adjustment can generally be adjusted between 0,8 inductive and 0,8 capacitive.
The choice of power factor for equipment operation depends, among other things, on the strategy used by the designer to control the installation's power factor and the technical-financial viability that this strategy will provide; in the case of inverters for centralized application, the power factor adjustment may be indicated by the ONS (National Electric System Operator), according to studies of the basic network and stability requirements.
Typically, inverters for Distributed Generation (DG) are programmed to operate with a unity power factor, for reasons of financial attractiveness, since electrical energy credits are accounted for the injected active energy (PF = 1).
But there are situations where the power factor can be adjusted to provide reactive power to the grid, which will always depend on the type of installation, implemented loads, local needs and financial return.
Below, an explanation of important topics in this article for understanding the power factor will be given, before the practical case is presented.
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