Decentralized Voltage Balancing and Power Sharing in Islanded Bipolar DC Microgrids

This paper presents a decentralized controlscheme for voltage balancing and power sharing in bipolar dcmicrogrids. This relies on utilizing a converter topology whichoffers three levels of output voltage availability with the keyfeatures of boosting the input voltage and balancing the outputvoltages. This converter makes it possible to further improve thestructure of bipolar dc microgrids as it does not require a centralvoltage balancer. Small-signal analysis is done and systemtransfer functions are derived. Based on the RGA concept thehighly coupled input-output pairs are found which helps withreplacing the MIMO control system of the converter by two SISOsystems. The appropriate voltage and current controllers aredesigned based on SISO principles. Moreover, a double droopcontrol method is proposed which fulfills the simultaneous powersharing and voltage regulation of DG units in the host microgrid.The effectiveness of the proposed control strategy isdemonstrated through simulation studies conducted on anislanded bipolar dc microgrid involving unbalanced loads, whilethe voltage balancing of the bipolar dc microgrid and the powersharing accuracy are evaluated.

Keywords:

Bipolar dc microgrid , bipolar boost converter , droop control , voltage balancer