A grid connected microgrid connects to the grid at a point of common coupling. Due to the great inertia of the grid which accelerates and
decelerates the generator when its frequency tends to deviate, the grid connected
microgrid operates at a frequency of the infinity bus. Frequency instability is
one of the major challenges facing the grid connected microgrid during islanding.
The power demand variation causes the variation in rotor speed, resulting to
frequency deviation. Frequency can be brought back to standard by varying the power generation to match with the varying load.
The performance of the frequency stability control system at Mwenga
hydroelectric microgrid has been studied. Through site visitation, the
power demand and generation status data were collected and analysed for model
preparation. The results of the study indicatethat, during islanding, the Mwenga rural
electrification project is observed to be subjected to power imbalance which
leads to frequency instability. Although the frequency control system tries to
keep the system at a nominal frequency by maintaining the continuous balance
between generation and varying load demand, however the system still operates with large magnitude of
overshoot, undershoot and longer settling time.
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