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Modeling and simulation Chapter | 5 149

overvoltage condition. The Volt/Var control used by OpenDSS has proven to
be an effective alternative as long as care is taken with the inverter rating
specifications.
Other methodologies have been presented when the control is not able to
regulate the voltage. The use of the Volt/Watt control, despite being able to
maintain the voltage in the proper range, caused a considerable reduction on
output power of the PV, which in most cases is not desirable. The insertion
of multiple Volt/Var controls was not very satisfactory for local voltage reg-
ulation and would require appropriate coordination and communication
among inverters. In addition, the insertion of energy storage in the PV
system proved to be an interesting alternative, regulating the voltage in the
generation period of the PV and relieving the system in moments of higher
demand.

5.5.2 Case 2: Harmonics

This case study showed how different load models may impact harmonic
analyses. Also, load composition has considerable influence over the magni-
tude and the frequency of the resonant peaks. Capacitors should be modeled
as accurately as possible, including filters of PV inverters, smart grid
devices, and other electronic-based loads.
The induction motor model was proposed for a low or moderate share of
motors in an aggregate linear load. Therefore this model is slightly superior
to the series and parallel models in this study case. But remember that there
is not a unique model fitting for all frequencies.
Incorrect modeling of linear loads may lead to unrealistic harmonics eva-
luations. Most harmonic discrepancies of aggregated linear loads occur near
parallel resonant points. Furthermore, the background harmonics play an
important role in harmonic studies, such as for hosting capacity evaluation
on modern power systems.

5.6 Conclusion

This chapter presented methodologies to address some challenges that may
occur in power distribution networks with the increasing penetration of DG,
using the modeling tools of the open-source software OpenDSS.
Impacts of high penetration levels of DG in distribution systems were
presented, including not only the technical aspects but also socioeconomic
impacts. Smart functions of power inverters were reviewed, since those
devices have a high potential to play a key role in the operation and control
of future power systems. A description of the modeling and analyses tools of
OpenDSS was presented, including the main aspects for modeling loads,
storage units, PV systems, other linear, and nonlinear electrical components.