An optimised state‐of‐charge balance control strategy for distributed energy storage units in islanded DC microgrid

Distributed energy storage technology is used to stabilize the frequency and voltage of the microgrid operating in islanded mode. However, due to the inconsistent state of charge (SoC) of the energy storage unit (ESU), the active power output of the ESU cannot be shared reasonably. On the basis of stabilizing voltage and frequency, this paper presents a power exponential function droop control (PEFDC) strategy considering the SoC. In this control strategy, the ESU is allowed to adjust the output power adaptively according to its own SoC level during discharge and reaches SoC equilibrium. Simulation models are built to compare the PEFDC strategy with conventional droop control (CDC) and power function droop control (PFDC) approaches. The simulation results illustrate the superiority of the proposed control strategy over the other two methods. Finally, the hardware-in-the-loop experiment is conducted to verify the effectiveness of the PEFDC strategy.

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Multiagent-Based Distributed State of Charge Balancing Control for Distributed Energy Storage Units in AC Microgrids

IEEE Transactions on Industry Applications ◽

10.1109/tia.2016.2645888 ◽

2017 ◽

Vol 53 (3) ◽

pp. 2369-2381 ◽

Cited By ~ 51

Author(s):

Chendan Li ◽

Ernane Antonio Alves Coelho ◽

Tomislav Dragicevic ◽

Josep M. Guerrero ◽

Juan C. Vasquez

Keyword(s):

Energy Storage ◽

State Of Charge ◽

Distributed Energy ◽

Distributed Energy Storage ◽

Charge Balancing ◽

Balancing Control ◽

Storage Units

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Bidirectional DC/DC and SOC Drooping Control for DC Microgrid Application

Electronics ◽

10.3390/electronics9020225 ◽

2020 ◽

Vol 9 (2) ◽

pp. 225

Author(s):

Chunjiang Zhang ◽

Pengcheng Li ◽

Yingjun Guo

Keyword(s):

Energy Storage ◽

Power Index ◽

Droop Control ◽

Distributed Energy ◽

Dc Microgrid ◽

Distributed Energy Storage ◽

Dc Bus ◽

Bus Voltage ◽

Communication Lines ◽

Storage Units

In DC microgrids, distributed energy storage plays a key role in stabilizing the DC bus voltage. The bidirectional DC/DC converter in the distributed energy storage system should be designed according to the voltage level and electromagnetic isolation requirements, and multiple energy storage units should be coordinated for load current distribution according to the state of charge (SOC). This paper proposes a SOC power index droop control strategy by communication lines to coordinate the fast and high-precision distribution of load current among multiple energy storage units, and the SOC between energy storage units quickly converges to a consistent state. Considering that communication lines are susceptible to interference, this paper further proposes an improved SOC power index droop control to overcome the effects of communication line failures. Considering the high cost of the energy storage unit, it should be connected to the DC microgrid in layers to achieve a reasonable allocation of resources in practical applications. In order to provide high-quality power to a large power grid, the quantification standards of the DC bus fluctuation range and the working range of each converter are further discussed to maximize the stability of the DC bus voltage and grid-connected power fluctuation.

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