A Novel Control Strategy to Achieve SOC Balancing for Batteries in a DC Microgrid Without Droop Control

In a dc microgrid, several batteries with their converters are controlled to share the bus deficient/excessive power among themselves. A battery management system is required to improve the reliability and appropriate power-sharing. A novel control strategy is proposed in this article that ensures power sharing among the various batteries in accordance with their power rating and state of charge (SOC). In the proposed scheme, a common time reference (T-ref) is generated using the conventional dc-bus voltage control loop and SOC information of the batteries with the help of communication. An attractive feature of the proposed scheme is that it does not depend on output current of the converters. Voltage regulation is also maintained within limits in case of wide deviation in the converter output voltage at interfacing point by monitoring and using corrective measures. A low-speed communication is sufficient to convey the reference time to the controllers of the batteries. The batteries are charged or discharged in the same time interval irrespective of the initial SOC, which significantly increases their life and performance. The proposed system is more reliable as it is tolerant to various fault scenarios. All the analytical, simulation and experimental results are presented.