Cycle‐by‐cycle error reduction droop method to improve power sharing in low‐voltage microgrid

摘要

A new cycle-by-cycle error reduction method is presented to permit accurate sharing of active power among unequal capacity distributed generation (DG) units that are connected to the bus through non-negligible line impedances. This new method overcomes limitations of the conventional and widely applied droop methodvoltage active power droop and frequency reactive power boostin low-voltage microgrids (MGs). In each control cycle, the new method implements 2 operations: (1) reducing the error in active power sharing and (2) maintaining the bus voltage. The voltage maintaining operation is necessary because the error reduction operation has the side effect of decreasing DG output voltages. Voltage maintaining is managed by a simple PI controller in a MG central controller based on sampling of the bus (point of common coupling) voltage. The output value of the PI controller is sent to local controllers in each DG unit and added to voltage functions to compensate the decrease of output voltage. Only low-bandwidth 1-way communication is needed from the MG central controller to the DG units, so it is easy to preserve plug and play operation. The effectiveness of the new method is proven through simulation-based analysis.