VFD-Based Frequency Regulation and Surplus Utilization Framework for Standalone Micro-Hydro Power Plants

Standalone micro-hydro power plants commonly regulate excess generation through electronic load controllers, which dissipate surplus energy in ballast loads. This study evaluates a dual-inverter variable-frequency-drive framework that prioritizes domestic demand and directs the remaining DC-link power to a motor-pump system. The controller applies 6/4 kW hysteresis and a 0.7 kW/s pump-power ramp limit. A 24-hour energy-management analysis was combined with a short-duration switched-inverter assessment of DC-link and load-side power quality. For a 30kW generator, the system served 423.69 of 424.00 kWh/day of domestic demand and supplied 181.08 kWh/day to the pump drive, recovering 95.95% of the available DC-side surplus. Relative to a conventional electronic load controller, useful end-use utilization increased from 65.75% to 84.66%. The regulated output had a mean phase voltage of 225.85 V, a mean frequency of 49.982 Hz, a maximum frequency deviation of 0.0346 Hz, and a voltage total harmonic distortion of 3.996%. The results indicate that the proposed configuration can reduce dissipative surplus handling while maintaining domestic energy service and acceptable load-side power quality.