Distributed Control Strategy for Low-Voltage Three-Phase Four-Wire Microgrids: Consensus Power-Based Control

Abstract

Most of the distributed control strategies for gridconnected power converters are droop-based approaches composed of converters driven in voltage-control mode, based on local and shared data with adjacent units. They are usually combined with consensus protocols to deal with the trade-off between power sharing accuracy and voltage/frequency regulation. To achieve the desired results these control systems usually incorporate other techniques and need to take into account details of primary control dynamic. Additionally, power flow control and current unbalance compensation at the PCC are rarely addressed in such approaches. Contrariwise, the centralized control strategy power-based control has been successful in achieving these functionalities. It is oriented to a set point selection to the whole system, considering converters driven in current-control mode and a central converter in voltage-control mode. However, the dependence on centralized communication network in this method still requires improvement. Thereby, the complementary features of both strategies are combined herein in the consensus power-based control, based on a master/slave peerto-peer integration using sparse communication. This model-free approach provides all aforementioned benefits to the grid without any other technique. Implementation complexity and costs are decreased, while the flexibility and reliability are enhanced. All these achievements are demonstrated by simulation results under different operational conditions and compared to previous works.

Distributed Control Strategy of Single-Phase Battery Systems for Compensation of Unbalanced Active Powers in a Three-Phase Four-Wire Microgrid

“…In addition, a distributed control strategy was proposed for single-phase distributed generators (DGs) to alleviate the unbalanced powers at PCC, but without considering variability and fluctuation of RESs [25]. It can be observed from the literature review that few studies focused on using single-phase distributed ESSs with distributed control strategies to mitigate the unbalanced conditions.…”

Consensus-Based Single-Phase Control of Three-Phase Inverter for Current Sharing in Three-Phase Four-Wire Isolated AC Microgrids

“…The autonomous decentralized sharing strategies highlight that the control system is designed so that current sharing occurs without the need for communication between DGs using droop control [4]- [10], and the components sharing techniques of unwanted currents based on communication: (i) centralized approach [11]- [13] where a central node receives and sends information to all DGs; (ii) distributed approach [14]- [25], in which DGs exchange information with each other without the need for a central controller. The characteristics of all approaches were discussed in [24].…”

“…Regardless of the type of MG secondary control, that is, centralized, autonomous or distributed control, several strategies are available for sharing unwanted current components. For example, [9], [20], [23] and [25] only address the sharing of unbalance currents. And for instance, [4]- [6], [10]- [12], [13], [15] and [16] only address the sharing of harmonic currents, while [14], [17], [21] and [22] approach the simultaneous sharing of harmonic and unbalanced currents.…”

“…As evidenced in [6], [9], [11]- [19], [21]- [25], several strategies have successfully demonstrated ways to share harmonic currents and unbalanced currents between DGs. However, as three-phase four-wire MGs contain unbalanced and non-linear loads, to the best of the author's knowledge, no analyzed work has demonstrated an adequate sharing of the RMS value of the total current (in the abc frame) of each phase between the DGs.…”

“…However, [23] does not address scenarios composed of three-phase four-wire networks with the presence of a neutral conductor, nor does it address the operation of the control system when non-linear loads that generate harmonic currents are connected to the isolated microgrid. The equalization of the current of each phase in the abc coordinates is addressed in [25], considering a three-phase four-wire MG (with return conductor). However, reference [25] does not manage the sharing of harmonic currents.…”