Harmonic distortion assessment in power distribution networks considering DC component injection from PV inverters

•This paper reinforces that PV inverters inject higher harmonic content when working with power of up to 20% of their nominal capacity.•Extensive simulations show that the DC current can alter the operational characteristics of distribution transformers.•Simulation results show that three of four el...

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Bibliographic Details
Published in:Electric power systems research 2020-11, Vol.188, p.106521, Article 106521
Main Authors: Fortes, Rárison R.A., Buzo, Ricardo F., de Oliveira, Luís C.O.
Format: Article
Language:English
Subjects:
Capacitors
Coils (windings)
Current injection
Direct current
Distributed generation
Electric power distribution
Electricity distribution
Electricity generation
Harmonic analysis
Harmonic current
Harmonic distortion
Inverters
Network reliability
Photovoltaic cells
Power transformer
Resonance
Studies
Transformers
Utilities
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Summary:•This paper reinforces that PV inverters inject higher harmonic content when working with power of up to 20% of their nominal capacity.•Extensive simulations show that the DC current can alter the operational characteristics of distribution transformers.•Simulation results show that three of four electrical parameters of the capacitors bank exceeded their allowable limits due to the critical operational condition. The large-scale connection of distributed generation (DG) units imposes on utilities a series of technical, economic, and regulatory challenges required to ensure the reliability and the power quality in the distribution networks. One of the technical problems refers to the harmonic current levels caused by inverters employed in photovoltaic distributed generation (PV), increasing the possibility of resonance in systems with capacitors. In addition, inverters without isolation transformer can also inject a certain amount of DC current which, being present in power transformer secondary windings, favor the generation and propagation of additional harmonics in the primary side. Thus, this paper shows that DC currents injected by PV inverters create one more condition that may cause system-capacitor resonance. For this, laboratory analyses are presented showing the conditions under which different models of PV inverters inject a higher DC current level. As a result, it is verified that higher DC current level is injected in conditions different from those in which there is higher harmonic current injection, concluding that the inverter may affect the power quality for whatever the power injected by the PV system.
ISSN:0378-7796
1873-2046
DOI:10.1016/j.epsr.2020.106521