The Design And Resolution Of Control System Based On The Small Water Multi-connected Air-conditioning

Recently, China focuses on constructing the circular economy, realizing scientific development concept, and taking the energy-saving, environmental protection and resource efficiency as the core of constructing economical society in the eleventh five-year plan. The concept "to carry out the scientific concept of development and to build a resource-efficiency society" has became the essential guideline of boosting economy. Calling for developing renewable energy applications, the state council issued the 《PRC renewable energy law》 in2005, and 《The decision to boost energy efficiency》 in2006. The key of researching and developing central air conditioning technology will still remain in energy efficiency. With the increasing requirements of users, the interface, the degree of comfort, and the centralized control of the air conditioning products are to be upgraded to meet greater demands. The central air conditioning products are generally divided into two categories:cold water unit and air cooling split unit. Most of the cold water chillers are from the manufacturers of Europe and the United States, such as York, Carrier, Trane and McQuay. Its main characteristic is highly energy-efficient, stable operation and so on. Air cooled split units are from Japanese manufacturers, such as the Daikin, Hitachi, Mitsubishi, Toshiba and so on. Its characteristics are a freely changeable configuration, a higher degree of comfort, and the control diversification. These two types of products have different features, and currently hold the equal domestic market share. This paper introduces a newly developed project, water VRF air conditioning and its research goal of combining the advantage of water chillers and air cooled splits together.This paper concludes the latest research results of Hisense Hitachi small water multi-connected air-conditioning control system, which uses the water multi-connected control technology, DC frequency conversion control technology, the frozen trinity technology, wide water temperature adapted technology and the HBS bus communication technology. This paper discusses the control system design, communication protocol, control algorithm, electrical structural processing, water application technology, compressors drive and protecting warning processing. The paper especially focuses on the technology of frozen trinity and DC frequency control technology of the compressor driven.The research results are mainly discussed in the following aspects:The overall design scheme of water source for small multi-connected air-conditioning control system is made; the product combines the advantages of flexible load processing, the multi-connected configuration, the energy-effcient water-cooling unit and stable operation.The system adopts the popular bus control, enabling the long distance contact of the compressor units. The system is stable and convenient as it can operate by multi-set or centralized control to manage via network.Multi-control outdoor unit is designed. From its very beginning, its boards are well regulated, the spare parts are carefully selected, and the sample is experimented in every ways to ensure the stability of the control boards and they are aligned with the EMC standards. The experiments also include the electrical specification, thermal design and vibration.The multiple factors of trinity and control logic through the pressure sensor, the temperature sensor, water flow switch, and many other parts of the board to avoid freezing.The newly developed MCU is adopted. It has a greater capacity with multiple ports. It has a better anti-interference ability and its designed lifetime is rather long so that in the numerous experiments, the potential of water VRF air conditioning is fully used.Hitachi DC frequency scroll compressor is adopted as it has a prior starting performance, low voltage operation and a higher efficiency.The small multi-connected system has been partly operated. The results indicate that the system control scheme is a reasonable and reliable operation, which saves the energy notably.