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. 2024 May 2;14(1):10118.
doi: 10.1038/s41598-024-60244-x.

Control strategy for current limitation and maximum capacity utilization of grid connected PV inverter under unbalanced grid conditions

Jyoti Joshi  1 , Vibhu Jately  2 , Peeyush Kala  3 , Abhishek Sharma  4 , Wei Hong Lim  5 , Brian Azzopardi  6   7
Affiliations

Control strategy for current limitation and maximum capacity utilization of grid connected PV inverter under unbalanced grid conditions

Jyoti Joshi et al. Sci Rep. .

Abstract

Under grid voltage sags, over current protection and exploiting the maximum capacity of the inverter are the two main goals of grid-connected PV inverters. To facilitate low-voltage ride-through (LVRT), it is imperative to ensure that inverter currents are sinusoidal and remain within permissible limits throughout the inverter operation. An improved LVRT control strategy for a two-stage three-phase grid-connected PV system is presented here to address these challenges. To provide over current limitation as well as to ensure maximum exploitation of the inverter capacity, a control strategy is proposed, and performance the strategy is evaluated based on the three generation scenarios on a 2-kW grid connected PV system. An active power curtailment (APC) loop is activated only in high power generation scenario to limit the current's amplitude below the inverter's rated current. The superior performance of the proposed strategy is established by comparison with two recent LVRT control strategies. The proposed method not only injects necessary active and reactive power but also minimizes overcurrent with increased exploitation of the inverter's capacity under unbalanced grid voltage sag.

Keywords: Active and reactive power control; Active power curtailment; Grid connected PV system; Inverter current limitation; Voltage stability.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1
Figure 1
Block diagram of a two-stage grid-connected PV system.
Figure 2
Figure 2
Conventional current control strategies (a) Grid voltage during a single-phase dip (b) Instantaneous active reactive control (IARC) (c) Positive negative sequence control (PNSC) (d) Average active reactive control (AARC) (e) Balanced positive sequence control.
Figure 3
Figure 3
Block diagram of the proposed control strategy.
Figure 4
Figure 4
Non-MPPT mode of operation: (a) point of operation on power curve and (b) control block.
Figure 5
Figure 5
Results of the TL-VSS under high power generation scenario at G = 1000 W/m2 (a) grid voltage, (b) injected active power, (c) injected reactive power, (d) inverter current and (e) dc-link voltage.
Figure 6
Figure 6
Results of the proposed control strategy under high power generation scenario at G = 1000 W/m2 (a) grid voltage, (b) injected active power, (c) injected reactive power and (d) inverter current.
Figure 7
Figure 7
Results of the MR-CLS under medium power generation scenario at G = 700 W/m2 (a) grid voltage, (b) injected active power, (c) injected reactive power and (d) inverter current.
Figure 8
Figure 8
Results of the proposed control strategy under medium power generation scenario at G = 700 W/m2 (a) grid voltage, (b) injected active power, (c) injected reactive power and (d) inverter current.
Figure 9
Figure 9
Results of the MR-CLS under low power generation scenario at G = 300 W/m2 (a) grid voltage, (b) injected active power, (c) injected reactive power and (d) inverter current.
Figure 10
Figure 10
Results of the proposed control strategy under low power generation scenario at G = 300 W/m2 (a) grid voltage, (b) injected active power, (c) injected reactive power and (d) inverter current.
Figure 11
Figure 11
Results of the proposed control strategy for a two-phase grid voltage sag (a) grid voltage, (b) injected active power, (c) injected reactive power and (d) inverter current.
Figure 12
Figure 12
Results of the proposed control strategy for a three-phase grid voltage sag (a) grid voltage, (b) injected active power, (c) injected reactive power and (d) inverter current (e) Phase-A grid voltage and inverter current before and after fault.
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