Frequency converting control system and control method suitable for central cooling system of ship

Abstract

The invention relates to a frequency converting control system and control method suitable for a central cooling system of a ship. Energy is saved. Three sea water pumps with 50% flow and the frequency conversion technology are adopted, only one sea water pump is used for frequency conversion operating under medium-low thermal loads, and two sea water pumps are used for frequency conversion operating under high thermal loads. Under the low thermal loads, the temperature of fresh water is controlled by adjusting the bypass amount of a temperature control valve. Under medium-high thermal loads, the temperature of the fresh water is controlled by adjusting the rotating speeds of the sea water pumps. Control precision on the temperature of the fresh water is high, and the response speed is high. Operation is easy, an operator only needs to start one sea water pump, and starting and stopping of the second sea water pump and adjustment of the bypass amount of the temperature control valve and the rotating speeds of the sea water pumps are all automatically completed through an electric cabinet. High reliability is achieved, adjustment of the bypass amount of the temperature control valve and adjustment of the rotating speeds of the sea water pumps are separately carried out, and no conflict is generated. When a frequency converter breaks down, the temperature control valve can be independently used for controlling the temperature of the fresh water. When the temperature control valve breaks down, the frequency converter can be independently used for controlling the temperature of the fresh water, and the temperature of the fresh water cannot be out of control.

Description

technical field [0001] The invention relates to a cooling control system, in particular to a frequency conversion control system and control method suitable for the central cooling system of a ship. Background technique [0002] Traditional ship central cooling system such as figure 1 shown. The system mainly includes three cooling water circuits: seawater, low-temperature fresh water, and high-temperature fresh water. It is composed of seawater pumps, central coolers, low-temperature fresh water temperature control valves, fresh water coolers, high-temperature fresh water temperature control valves and other major equipment. The seawater pump sucks seawater from the outboard and sends it into the central cooler, and the seawater is directly discharged outboard after cooling the low-temperature fresh water in the central cooler. The low-temperature fresh water is cooled by seawater in the central cooler, and then enters the cooled equipment and the fresh water cooler throu...

AI Technical Summary

Problems solved by technology

Although this method can achieve effective control of fresh water temperature, there is a lot of energy loss in the throttling loss of the bypass pipeline and the temperature control valve after the opening is reduced, and the economy is poor.

In the design of the central cooling system, in order to ensure that the ship can sail in all sea areas, it is usually assumed that the seawater temperature is 32°C, and the seawater pump must also meet the seawater flow required by all the cooled equipment to operate at full load, but the ship sails at low temperature most of the time. At the same time, the heat load of the cooling system will not be in a high state for a long time. Therefore, the cooling capacity of the sea water pump is in a long-term surplus state, wasting a lot of electric energy

[0004] In view of the problems existing in the central cooling system of traditional ships, patent CN202642088U discloses a method of replacing two seawater pumps with 100% flow rate with three seawater pumps with 50% flow rate, and the seawater pumps are still operating at power frequency; patent CN103448899A discloses a fresh water The pump operates with frequency conversion, and the seawater side adopts the method of adjusting the flow of seawater by valves in stages; the above two methods can achieve the purpose of energy saving, but the energy saving effect is limited

Patent CN201916173U discloses the use of permanent magnet synchronous motor plus variable frequency drive technology to control the seawater pump; patent CN203127133U discloses the method of controlling the displacement of the seawater pump through the temperature signal fed back by the temperature sensor installed at the freshwater outlet of the heat exchanger to control the temperature of the freshwater at the outlet of the heat exchanger method; patent CN201330716Y discloses a circuit for controlling the displacement of seawater pumps by frequency conversion; this kind of method relying on frequency conversion speed regulation of seawater pumps has a certain energy-saving effect, but is limited by the outlet pressure of seawater pumps and the efficiency of seawater pumps. The speed adjustment range of the pump is narrow, so the energy saving effect is limited. At the same time, after the sea water pump reaches the minimum speed, the cooling water temperature control when the heat load is low cannot be realized.

Patent CN203358863U discloses a method for simultaneously adjusting seawater pumps, freshwater pumps, and temperature control valves to jointly control the cooling water temperature. This method has many actuators, the system is relatively complicated, and parameter setting is difficult, which is likely to cause cooling water temperature oscillations. At the same time, the patent Using two 100% flow seawater pumps, the speed adjustment range of seawater pumps is limited by pressure and efficiency, and the energy saving effect is limited

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