Control Scheme for Photovoltaic Three-Phase Inverters to Minimize Peak Currents During Unbalanced Grid-Voltage Sags

Abstract

Nowadays, the majority of the photovoltaic (PV) power sources are connected to the public grid. One of the main connection problems occurs when voltage sags appear in the grid due to short circuits, lightning, etc. International standards regulate the grid connection of PV systems, forcing the source to remain connected during short-time grid-voltage faults. As a consequence, during the voltage sag, the source should operate with increasing converter currents to maintain the injection of the generated power. This abnormal operation may result in nondesired system disconnections due to overcurrents. This paper proposes a controller for a PV three-phase inverter that ensures minimum peak values in the grid-injected currents, as compared with conventional controllers. From the system analysis, a design method is presented in order to set the parameters of the control scheme. Selected experimental results are reported in order to validate the effectiveness of the proposed control.Index Terms-Fault ride-through, grid international standards, photovoltaic (PV) power source, voltage sag.

Control Strategy for Three-Phase Grid-Connected PV Inverters Enabling Current Limitation Under Unbalanced Faults

“…With the fast increase of grid-connected Photovoltaic (PV) generation, PV systems should contribute to the grid stability by providing ancillary services, beyond the basic power delivery [1][2][3][4]. Also, based on the recently revised grid codes, PV inverters are preferred to stay connected during grid voltage faults [5][6][7].…”

Flexible unbalanced control with peak current limitation for virtual synchronous generator under voltage sags

“…In [17], a current reference calculation method is introduced to provide voltage support. Reference [18] aims at reducing active power oscillation to exploit the maximum capability of distributed generation. In [19,20], the selection of a proper current reference is proposed to override grid faults and meet different power quality requirements.…”

Ground-Fault Characteristic Analysis of Grid-Connected Photovoltaic Stations with Neutral Grounding Resistance

“…The majority of PV power sources are connected to the public grid, and because of the geographical distribution of solar resources [1], the centralized connection of large-scale PV power generation to the public grid is an important characteristic of grid-connected PV power stations [2][3][4].…”