PROJECT TITLE :

Power-Capacity-Based Bus-Voltage Region Partition and Online Droop Coefficient Tuning for Real-Time Operation of DC Microgrids

ABSTRACT:

Multiple-voltage-region management, in that the bus-voltage vary is divided into several regions, is sometimes implemented for dc microgrid operation in distributed manner. Voltage/power droop relationships are imposed for active power sharing among slack terminals. Conventionally, threshold voltages for voltage region partition are determined with fastened proportion of variation round the nominal price, that might result in unevenness of droop coefficients in different regions. If system droop coefficient is just too high, significant bus-voltage step change thanks to load variation can occur. On the other hand, significant power sharing error among slack terminals can be induced if the droop coefficient is too low. In this paper, a compromised solution with power-capability-based bus-voltage region partition is proposed to equalize the droop coefficients in different regions. However, the droop coefficients are determined based on the rated power capability of system units. Bus-voltage discontinuity appears when the power capability reduces in actual implementation. To eliminate the voltage discontinuity, online droop coefficient tuning in keeping with the real-time power capacity is implemented. Algorithms for local power capacity estimation of solar photovoltaic (PV) and battery energy storage are proposed. A lab-scale dc microgrid has been developed for verification of the proposed strategies.