Optimal Voltage Unbalance Suppression Control Using PV Inverter in Distribution Network

• Published in: IEEE transactions on power electronics Vol. 40; no. 10; pp. 14985 - 15002
• Main Authors: Feng, Qifan, Yang, Pengcheng, Xia, Yanghong, Wei, Wei, Han, Yukai
• Format: Journal Article
• Language: English
• Published: IEEE 01.10.2025
• Subjects: Current limiting; Distribution networks; Impedance; Inverters; Limiting; Optimal control; Oscillators; photovoltaic (PV); power oscillation; Power quality; Power system stability; Voltage control; Voltage fluctuations; voltage unbalance (VU)
• ISSN: 0885-8993; 1941-0107
• DOI: 10.1109/TPEL.2025.3576144

Distribution networks exhibit unbalance issues due to arbitrarily connected devices. This article advances the control strategy of optimal voltage unbalance (VU) suppression using photovoltaic (PV) inverters. This matter is formulated as an optimization problem to minimize the negative sequence voltage at the point of common coupling (PCC), subject to current limiting, power oscillation, power balance, and circuit theorems. To solve this problem, the underlying geometry properties of constraints are explored. Then, the boundaries of trajectory of compensating current are obtained under different VU conditions, which proves the availability of the optimal solution acquired by P&O method. Next, by accurately calculating the injected negative sequence currents of the PV inverter, the minimum unbalanced voltage at PCC is obtained by proposed control strategy, which can be implemented without the information of grid impedance and ensuring maximum output power of PV array. Finally, the applicability of gird fault and multiple inverters are investigated. The effectiveness is valid by hardware-in-loop tests and experiments based on actual scale-down microgrid. This article is accompanied by a video file demonstrating the proposed control in real scale-down microgrid.