Control strategy for microgrid under three-phase unbalance condition

Abstract

Microgrid (MG) is generally developed at utility terminal which contains lots of unbalanced loads and distributed generations (DGs). The interaction between MG and the unbalance loads or DGs will degrades the control performance of interfaced inverter in MG and dramatically leads to MG voltage unbalance. In this paper, a negative-sequence compensation based three-phase voltage unified correction strategy is proposed. While MG operates in islanded mode, a positive virtual impedance control is used to eliminate the negative voltage resulted from the negative-sequence current, and then a positive-sequence voltage control loop and negative-sequence control loop are used to improve the inverter control performance. While MG operates in grid-tied mode, the inverter operates as a negative-sequence current source to compensate the negative-sequence currents of loads to guarantee the point of common coupling (PCC) voltage balance. By using the proposed strategy, the voltage control performance of inverter can be improved; the MG power quality can be enhanced significantly. Simulation and experimental results verify the effectiveness of the proposed method.

Power electronic transformer with adaptive PLL technique for voltage-disturbance ride through

“…Three-phase inverters are made up of three identical modular single-phase full-bridge H4 inverters, which have an excellent inner unbalanced-load correction capability, or other extra control methods should be added to the threephase inverter [23]. The AC output voltage is regulated with double-loop controllers, where the outer loop is set to regulate the RMS value of the voltage, while the inner loop regulates the instantaneous value of the voltage.…”

MAS-Based Distributed Coordinated Control and Optimization in Microgrid and Microgrid Clusters: A Comprehensive Overview

“…1, is controlled by the microgrid central controller (MGCC) or the energy management system (EMS). A basic MG structure integrates RES [9,10], traditional generators, loads and energy storage systems (ESS) [11,12], thus forming a more flexible, self-sufficient and environmental friendly system than the individual DG units [13]. The RES, such as wind turbines or photovoltaic, through local controllers to send energy to the grid or communicate with the MGCC and energy management system (EMS).…”

Novel Filters Based Operational Scheme for Five-Level Diode-Clamped Inverters in Microgrid

“…Thus, this extracted negative-sequence voltage is converted into a voltage reference that is augmented with other voltage references. Another technique for compensating voltage unbalance is realized by the extraction and mitigation of the negative-sequence current (Shi et al, 2016), which is extracted and converted into a current reference that is applied to the current loop of the primary control level in its droop scheme.…”

“…• The mitigation of voltage unbalance is done through the negative-sequence voltage only; meanwhile, the connection of the microgrid to the ground is common (Mohammadi et al, 2019), which yields zero-sequence components in the microgrid. In the most of publications (Savaghebi et al, 2011(Savaghebi et al, , 2012(Savaghebi et al, , 2013Reyes et al, 2012;Liu et al, 2014;Lexuan et al, 2015;Zhao et al, 2015;Han et al, 2016b;Shi et al, 2016;Moghaddam et al, 2018;Ren et al, 2018;Acharya et al, 2019), the zero-sequence voltage is not considered for mitigation in the microgrid.…”