Central air-conditioning system and control method thereof

A control method for a central air-conditioning system including a refrigerating unit, a cooling water loop, a cooling water pump arranged on the cooling water loop, a cooling water pump frequency converter, a circulating water loop having a water inlet manifold and a water return manifold, a circulating water pump arranged on the circulating water loop, a circulating water pump frequency converter, a plurality of circulating water branches arranged in parallel on the circulating water loop, each of the plurality of circulating water branches including a water inlet branch pipe and a water return branch pipe, temperature controllers, fan coils, fresh air units and air handling units arranged in rooms, the fan coils and the fresh air units being arranged in parallel on the same respective circulating water branches, a regional flow balancing valve for controlling the flow of each water return branch pipe arranged on each water return branch pipe, an energy balancing valve arranged on a water return pipe of each fan coil that respectively receives signals output by respective ones of the temperature controllers, and a plurality of tail-end return water temperature sensors including a respective tail-end return water temperature sensor arranged on the respective water return pipe of each fan coil, said control method comprising the steps, performed simultaneously or sequentially, of:

• (a) detecting the flow in each water return branch pipe, and adjusting the opening degree of each regional flow balancing valve according to a branch pipe set flow value, so that the flow in the water return branch pipe is smaller than or equal to the branch pipe set flow value;
• and
• (b) detecting return water temperature in a water return pipe of each fan coil, adjusting the opening degree of each energy balancing valve according to a tail-end return water set temperature value, detecting the room temperature when the return water temperature in the water return pipe of each fan coil is greater than or equal to the tail-end return water set temperature value, and adjusting, by each temperature controller, the opening degree of each energy adjusting valve.