Coordinated control of multiple voltage balancers in a Bipolar DC microgrid

For the neutral-point voltage balancing control in a bipolar dc microgrid, a coordinated control strategy which is composed of droop method and disturbance observer based current feed-forward has been proposed for parallel operation of multiple voltage balancers. With the observer and only the local measurements, the output current of the voltage balancer can be quickly tracked without any additional current sensors. Through the estimated value, dc voltage droop control and current feedforward can be well designed, with the purpose to realize unbalanced current sharing and plug-play feature with no communications, and to improve the dynamic and stability of neutral-point voltage balancing control respectively. The performance of the presented control has been verified in a prototype bipolar dc microgrid including a dc simulated voltage source, two voltage balancers, resistive dc loads and a dc-dc converter based constant power load.