Energy Reports (Sep 2023)
Research on control system for improving the grid-connected efficiency of small hydropower
Abstract
Aiming at the problem of low efficiency at low flow in small hydropower stations, a permanent magnet direct-drive hydropower generation control system based on dual PWM converters is proposed to realize wide-range variable-speed constant-frequency hydropower generation of hydraulic turbine units and improve the comprehensive power generation efficiency of small hydropower stations. In this control system, the hydraulic turbine is coaxially connected to the permanent magnet synchronous generator(PMSG) through the flywheel, and the power grid is connected by back-to-back dual PWM converters, and the bidirectional energy flow is realized by the voltage space vector pulse width modulation method. The generator-side converter controls the rotating speed of hydraulic turbine units and tracks the optimal speed point of the hydraulic turbine units in real time to realize the maximum power output of hydraulic turbine units. The grid-side converter adopts active power and reactive power decomposition control method to stabilize the DC bus voltage and provide the reactive power required by the grid. Finally, the effectiveness of the proposed control system was proved by comparative experiments in a 400V/200kW/428rpm small hydropower station.
