Coordinated Control for Islanded DC Microgrid Considering Power Sharing of Multiple Energy Storages

doi:10.12204/j.issn.1000-7229.2021.04.010

Abstract

Abstract:

A coordinated control for islanded DC microgrid considering power sharing of multiple energy storages is proposed to realize the balance control of the energy utilization maximization and the reasonable power sharing among multiple energy storages. The operation of the DC Microgrid is divided into five working modes according to the DC bus voltage. During mode transition, control structure of each unit keeps unchanged, and its droop curve can be adjusted adaptively according to current operating state. The coordinated operation of source and storage maintains the system power balance and bus voltage stability, which maximize the utilization rate of photovoltaic energy and ensures sufficient output of energy storage. Firstly, an adaptive power control strategy is applied to PV converters, which is based on automatic regulate the output power of PV tracking or off the maximum power point according to the DC bus voltage and realizes the smooth switching between maximum power point tracking (MPPT) mode and off-MPPT mode. Secondly, an adaptive droop control strategy based on the state of charge is designed for energy storages, which realizes the reasonable distribution of system power by multiple energy storage units according to their SOC and avoids excessive discharge or depth charge. Finally, the control strategy is verified by simulation with Matlab/Simulink.

Key words: DC microgrid, DC bus voltage, droop control, state of charge (SOC), power distribution

CLC Number:

TM732

WANG Zipeng, ZHENG Lijun, Lü Shixuan. Coordinated Control for Islanded DC Microgrid Considering Power Sharing of Multiple Energy Storages[J]. ELECTRIC POWER CONSTRUCTION, 2021, 42(4): 89-96.

Figures/Tables 11

Fig.1 Configuration of DC microgrid

Fig.2 Control strategy of DC microgrid underdifferent modes

Fig.3 Control block diagram of PV unit

Fig.4 Off-MPPT operating points

Fig.5 Flow chart of power control

Fig.6 Control block diagram of energy storage

Fig.7 Schematic diagram of power distribution of energy storage units

Table 1 System parameters of the DC microgrid

Fig.8 Simulation results of Case 1

Fig.9 Simulation results of Case 2

Fig.10 Simulation results of Case 3

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