Energy saving control system of frequency conversion in use for central air condition

Abstract

The invention is a variable-frequency energy-saving control system of central air-conditioner, composed of main controller and temperature sampling controller, where the input end of the main controller is connected with 485 communication circuit, memory, analogue quantity input circuit and switching quantity input circuit, and the output end of the main controller is connected with relay output circuit and frequency inverter output control circuit; the input end of the temperature sampling controller is connected with three sampling chips and the output end of he temperature sampling controller is connected with the 485 communication interface of the main controller through 485 communication port. The main controller implements a compound control according to the temperature signal and the pressure signal of evaporator and condenser of the central air-conditioner, and controls a three-phase AC machine by the output of the frequency inverter and the relay to realize the speed change, able to realize the variable frequency switching of two frequency inverters controlling three electric machines, providing the optimum working state for variable-frequency control system and achieving the best energy-saving effect.

Description

technical field [0001] The invention relates to a frequency conversion energy-saving controller of a central air-conditioning system. Background technique [0002] According to the annual and daily changes in the efficiency of the central air-conditioning system, the central air-conditioning operates at a low efficiency most of the time. The best conversion efficiency of the heat exchanger is when the design temperature difference of the chilled water is 5-7°C, and the design temperature difference of the cooling water is 4-6°C. At present, under the condition that the system flow rate is fixed, the temperature difference during most of the year's operation time is only 1 ~ 3 ℃, that is, working under the condition of low temperature difference and large flow, not only increases the energy loss of the pipeline system, but also greatly reduces the heat exchange rate. [0003] The traditional energy-saving control is to control the cooling water pump or chilled water pump for...

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Problems solved by technology

The best conversion efficiency of the heat exchanger is when the design temperature difference of the chilled water is 5-7°C, and the design temperature difference of the cooling water is 4-6°C. At present, under the condition that the system flow rate is fixed, the temperature difference during most of the year's operation time is only 1 ~ 3 ℃, that is, working under the condition of low temperature difference and large flow, not only increases the energy loss of the pipeline system, but also greatly reduces the heat exchange rate

[0003] The traditional energy-saving control is to control the cooling water pump or chilled water pump for energy-saving control, but because the output power of the centrifugal pump has the characteristics of the optimal operating point, the independent frequency conversion debugging makes the operating point of the pump often far away from the optimal operating point of efficiency, and the waste is quite serious , the power consumption of the air-conditioning water pump accounts for 20-30% of the power consumption of the air-conditioning system, so it is of great significance to save the water supply output energy of the water pump system at low load

CN01107645.3 proposes a central air-conditioning intelligent energy-saving system, which adopts programmable logic controller PLC, controlled by expert experience knowledge base, only detects the change of water temperature and air temperature, the deviation of analog quantity setting and independent frequency conversion debugging make the working point of the pump far away from the Optimum state, etc. affect energy saving effect

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