Backpressure control thermodynamic system of water feed pump turbine and control method of backpressure control thermodynamic system

The invention provides a backpressure control thermodynamic system for a water feed pump turbine. The backpressure control thermodynamic system comprises the water feed pump turbine and a driven device connected with the water feed pump turbine. The first heater is connected with a steam exhaust pipeline of the water feed pump turbine through a first bypass pipe, and an overflow valve is arranged on the first bypass pipe; the condenser is connected with a steam exhaust pipeline of the water feed pump turbine through a second bypass pipe, and a bypass valve is arranged on the second bypass pipe; a steam exhaust port of the pressure cylinder is connected with a steam exhaust pipeline of the water feeding pump turbine through a third bypass pipe, and a steam supplementing valve is arranged on the third bypass pipe; an overflow valve, a bypass valve and a steam supplementing valve which are arranged in the thermodynamic system are controlled through back pressure of the water feeding pump turbine; and in the cont