A novel variable speed constant frequency generation system for steam turbine and boiler feed pump

The steam-driven mode of boiler feed pump usually controls speed by adjusting the opening of the intake valve of the steam turbine. This method will result in valve loss, especially in the condition of light load. In this paper, a new steam-driven BFP system with a motor which is driven by full-power converter is proposed. Steam turbine, pump and motor are coaxially connected. With the valve in a wide-open position, speed is controlled by adjusting the electromagnetic torque of the motor for generating, thus the valve loss can be reduced. Based on flow characteristics of valves and speed-torque characteristics of turbines and pumps, this paper proves that the proposed system can reduce losses, save energy and improve efficiency when compared with traditional driven mode. Then model of this power generation system is established. In view of requirements under specific working condition, control strategy for working mode switching between intake valve and converter is studied, which is capable of maintaining flexibility of this BFP generation system in different conditions. Finally, a practical case is studied to prove the feature of energy saving and feasibility and effectiveness of the system are validated by simulation.