Distributed Control of Islanded Series PV-Battery-Hybrid Systems With Low Communication Burden

Abstract

The series photovoltaic-battery-hybrid (PVBH) system is considered as a promising solution to better integrating distributed energy sources. However, the state-of-the-art controls are either highly dependent on the communication, by which real-time control variables should be transmitted among all converters, or only suitable for PVBH systems with unity power factor. Accordingly, a novel distributed control is proposed for islanded PVBH systems in this paper. Firstly, a PQ decoupling control is introduced, enabling the control of individual converters with only local measurements. Then, a droop controller is implemented in the battery converter, allowing the system to participate in regulating the islanded grid (voltage and frequency). A reactive power distribution method is subsequently introduced to equalize power sharing among the converters. Additionally, two anti-over-modulation loops are developed to address the over-modulation issue of both PV converters and the battery converter. With the proposed method, only a few variables with very slow dynamics should be transmitted, and the communication burden can be significantly reduced, leading to higher reliability to some extent. Experimental results have validated the effectiveness of the proposal.

Flexible Active Power Control of Distributed Photovoltaic Systems With Integrated Battery Using Series Converter Configurations

“…However, the control methods in [17], [18], [29]- [32] are not applicable for series systems when the power factors (PFs) of individual voltage controlled converters are different, while real-time communication or additional grid-voltage sensors are still required for current-controlled converters [31]. To overcome this, a distributed control scheme was recently proposed in [33], where distributed PV converters can be selfsynchronized without the grid phase angle information, even if they have different PFs, significantly reducing the communication dependency. The anti-over-modulation (AOM) control and the reactive power distribution among all converters have also been addressed in [33].…”

“…To overcome this, a distributed control scheme was recently proposed in [33], where distributed PV converters can be selfsynchronized without the grid phase angle information, even if they have different PFs, significantly reducing the communication dependency. The anti-over-modulation (AOM) control and the reactive power distribution among all converters have also been addressed in [33]. Nevertheless, the solution in [33] is only for islanded applications, where the overall control objective for the entire series-PV-battery system is to maintain the islanded grid voltage and frequency.…”

“…The anti-over-modulation (AOM) control and the reactive power distribution among all converters have also been addressed in [33]. Nevertheless, the solution in [33] is only for islanded applications, where the overall control objective for the entire series-PV-battery system is to maintain the islanded grid voltage and frequency.…”

“…With the above concerns, FAPC strategies are proposed for grid-connected series-PV-battery systems, which is an extension of [39]. The proposed control methods are realized through the distributed control architecture of the series-PVbattery systems [33]. Compared to [33], various active power control schemes (e.g., PRRC, PLC, and PRC) for gridconnected series-PV-battery systems have been developed in this paper.…”

“…The proposed control methods are realized through the distributed control architecture of the series-PVbattery systems [33]. Compared to [33], various active power control schemes (e.g., PRRC, PLC, and PRC) for gridconnected series-PV-battery systems have been developed in this paper. With the proposed strategies, the active power of series-PV-battery systems can be flexibly controlled following the power ramp-rate/limiting/reserve constraints.…”