Original scientific paper
https://doi.org/10.37798/2026752745
Individual Phase Current Control Algorithm for Load Unbalance Compensation in Grid-Connected Three-Level Inverters Operating in Islanding Mode
Mohammed Moyed Ahmed
; JNTUH, Hyderabad, India
*
* Corresponding author.
Abstract
Grid-connected inverters must maintain a stable power supply to critical loads during islanding operation when grid faults occur. Unbalanced loads, however, make it difficult to sustain balanced three-phase voltages and can seriously impair sensitive three-phase equipment. This paper proposes a novel individual phase current control algorithm for load unbalance compensation in grid-connected three-level inverters operating in islanding mode. The method uses a dual-loop control architecture: a D--Q frame voltage controller handles overall voltage regulation, while an ABC frame current controller provides individual phase current management. A key feature is feedforward compensation using real-time load current measurements together with a static switch that enables flexible switching between three-wire and four-wire configurations. When a power-based detection algorithm identifies significant load unbalance, the system automatically transitions to four-wire mode, where independent control of each phase current is possible without the zero-sum constraint. The voltage controller operates at 5--6 Hz bandwidth in the D--Q frame to maintain balanced three-phase voltages for critical loads; the current controller operates at 1 kHz bandwidth in the ABC frame for fast individual phase current tracking. Simulation results show accurate current tracking -- a 1.76 A increase under a 100 % load step and a 1.02 A decrease under a 50 % load reduction -- while maintaining balanced voltages and reducing THD from 13.18 % to 3.64 % relative to a conventional approach.
Keywords
Grid-connected inverter; individual phase current control; load unbalance compensation; three-level inverter; islanding mode; dual-loop control
Hrčak ID:
350062
URI
Publication date:
15.6.2026.
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