Research on Novel Three-Level DC/DC Converter with Energy Transfer Function and Bipolar DC Voltage Control Strategy

DC microgrids with photovoltaics (PVs) and energy storage (ES) can achieve the maximum utilization of solar power. However, when PVs are connected to a bipolar DC microgrid, the mismatch of PV output power and load will cause the unbalance of the positive and the negative pole voltages. Focusing on such an issue, this paper proposes a control strategy based on a three-level DC/DC converter topology which can transfer energy with an additional inductance from the power surplus pole to the power shortage pole and then control ES to make up the gap. The operational principles under the normal states and the energy transfer states are analyzed in details. Finally, a model of bipolar DC microgrid with PVs and ES is built by PSCAD/EMTDC. The simulation results verify the effectiveness and the applicability of the topology and the control strategy. The transferred power is quantified comparatively from the micro and macro perspectives.