A Novel State-of-Charge-Based Droop Control for Battery Energy Storage Systems to Support Coordinated Operation of DC Microgrids

Abstract

A modern DC microgrid often comprises renewable energy sources (RESs) such as Photovoltaic (PV) generation units, battery energy storage systems (BESSs), and local load, and it is also connected to the utility grid through a point of common coupling (PCC). While most existing approaches have to rely on communication links to achieve desirable control performance, this paper proposes a novel control strategy without resorting to the communication links. This is achieved by assigning BESSs as master units and regulating the DC bus voltage with a novel state-of-charge (SoC)-based droop control, where the BESSs coordinate the slave units (e.g. RES, utility grid) with the aid of the DC bus signaling (DBS) technique to avoid overcharging and over-discharging of these BESSs. In the proposed droop control, the reference voltage for these BESSs is designed for coordinated operation between BESSs and utility grid, it is maintained constant in normal SoC range, which can reduce DC voltage variation. Droop coefficients designed for SoC balance of BESS are dynamically adjusted based on their own SoC values. Furthermore, the preset maximum deviation between the reference voltage and DC bus voltage ensures reliable coordinated operation. Real-time hardware-in-loop (HIL) experiments considering three different scenarios are conducted to validate the effectiveness of the propose method.

A Decentralized Power Allocation Strategy for Dynamically Forming Multiple Hybrid Energy Storage Systems Aided With Power Buffer

“…Thus, the power allocation among the batteries are based on their respective SoCs and SoCs of multiple batteries can gradually balance. A detailed discussion on SoC balance process was given in our previous publication [31]. Also, according to our previous study, a greater n leads to a faster SoC balance speed, and a satisfactory SoC balance speed and R b variation range have been achieved when n = 2, thus this value is adopted in the study.…”

A Novel Voltage-Current Dual-Drop Control Method for Shipboard DC Micro-Grid With Energy Storage Systems

“…The active current command is obtained from the intermediate DC bus voltage closed-loop PI controller link, and the reactive current command is tapered to 0. Specifically as shown in (10).…”

Distributed Secondary Control of Battery Storage Systems in DC Microgrids with A Virtual State Variable

“…where N c i denotes the set of nodes that have a communication links with i-th node, the communication weight value is set to a if j ∈ N c i in this paper. Further, the incoming cyber information matrix can be denoted by Z in = diag{d i }, This section will present a distributed secondary control to achieve objectives in Eq (5) to Eq (7). By adding a secondary control signal u i to the droop expression Eq (3), it yields…”