Simple And Small Multi Connected Air-conditioner Control System

With the development of economic and shortage of energy, people have more and more demands on comfort and energy saving of air-conditioner. Because of the characteristics of comfort and energy saving, DC inverter air-conditioner has become a trend of the market of air-conditioner. For the diversifications of modern architecture, traditional air-conditioning system, huge water cooled air-conditioner system, or unitary and constant frequency(inverted frequency) air-conditioner have no longer fit the demands of modern architecture. Multi connected air-conditioner (heat pump), which has the short name of VRF, appeared in the 1980s in Japan. In our country, it is a new centralized air-conditioning system, which has had many developments in recent years. The system, which integrates the technologies of frequency conversion and capacity changes, has the characteristics of energy saving, comfort and flexible control. By using different kinds of capacity combination, the system can fill the requirements of different buildings. Comparing with traditional centralized air-conditioning system, the new system doesn't have the main engine room, cooling tower, and water transmission and distribution system. As a result, the system only has indoor unit, outdoor unit, thin connecting pipes, power and communication wires, and so on. For these reasons, the complexity of the system is simplified, the maintainability and reliability of the system is increased. So the new air-conditioning system receives favorable comments.This paper makes a summary on control system of HISENSE/HITACHI's simple and small multi connected air-conditioner, in which the refrigerant is R410A. The control system applies technologies as follows:control technology of VRF, PID technology, phase detection technology, sensorless drive technology of permanent-magnet direct current compressor, PWM control technology of DC fan, and so on. This paper elaborates in detail on scheme of control system, communication protocol, control algorithm, heat calculation of basic board, selected calculation of high power devices, compressor drive, disposal of protect alarm, and so on. And the paper makes an emphasis on resistance sampling of permanent-magnet direct current compressor's drive.Research achievements of this paper are as follows: Make an overall design of control scheme of miniature multi connected air-conditioner system, which not only has the characteristics of flexible control and high efficiency of huge commercial control scheme, but also considers the characteristics of the small house and villa. This is a substitute for traditional one indoor and outdoor unit mode, in which outdoor uses main control basic board and variable frequency drive.The max load current and heat transfer situation of PCB is fully considered in the circuit design. So the PCB can pass following all kinds of experiments of reliabilities. This paper finishes controller of indoor and outdoor unit based on H8/36019.The compressor is HITACHI'S DC variable-frequency scroll compressor, and it has the characteristics of good startup performance, low voltage running, and high efficiency. The chip of compressor driving is BL/DC64 of NEC semiconductor and the driving scheme is designed by personnels of HISENSE/HITACHI Company. Now the part of compressor driving has finished the phase of test and has gone into the phase of amount test.Based on the total machine test of performance, the paper makes some work of energy saving. By using different test methods, the whole structure of the machine can fulfill the demands of 10 years of long-time running. Centralized control of the third party is realized and 485 communications can compatible with host agreement of many companies. So it can realize easy centralized control and promote the image of products and fulfill different needs of users.Build an alarm system of simple and small multi connected air-conditioner. The system can detect the process of running. When abnormal phenomenon takes place, the system can make sure that the air-conditioner system is safe, the part of compressor driver don't catch fire or demagnetization of compressor because of over current, and help the inspectors to find the causes of the problems quickly.Simple and small multi connected air-conditioner has been put into use in some parts of our country. The results indicated that the control system is rational, reliable, using advanced control algorithm, high efficient.