The purpose of central air conditioning control is to convert electrical energy into thermal energy, and to achieve the purpose of controlling the ambient temperature by adjusting the air volume or water flow. Since central air conditioning is not only a room or a small area as a temperature adjustment object, it is usually applied in multiple rooms or large areas, and there are multiple end devices. Therefore, centralized control of the main unit is generally adopted, and the end equipment is dispersed. Control method. As far as the electrical control part is concerned, the host control and the end control of most of the current central air conditioning systems are independent of each other, and the host part cannot understand the working condition of the end, and the end part cannot control the host.
With the development of central air-conditioning, the requirements for centralized decentralized control of central air-conditioning systems are increasing. For example, in many occasions, central air-conditioning billing systems need to be established, so network-based control and detection systems must be established. A network-type central air-conditioning control system should meet the following technical requirements to achieve control of the host unit and fault detection protection to send the working status of the host to all end controllers, such as the operating mode setting temperature of the switch, etc. Some systems also require The real-time clock and the timed on/off time are sent to the end device host controller to query the working state ambient temperature and the fault state of each end device, so that all or a specific end device can be controlled by the host controller. It is also possible to control the switch of the host through the opening of the terminal to connect to the computer through the network to realize functions such as remote control data query and recording.
One of the main contents of the network-based control system introduced in this paper is the networked control of the main unit, which can control a unit composed of the most compressors. The unit controller unit controller is composed of a single-chip microcomputer with an asynchronous communication interface. The input analog quantity has the return water temperature, the water outlet temperature, and the outdoor ambient temperature defrosting sensor temperature. The input switch quantity includes compressor high pressure and low voltage protection fan overload protection water flow switch protection and freezing point protection. The output control object has one or two compressor outdoor fan four-way reversing valve auxiliary electric heater crankcase heater and cold water pump.
Due to the large number of electrical equipment, the power is different. If the power is turned on or off at the same time, it will cause impact on the power grid and easily damage the equipment itself. Therefore, the switching machines of all equipment must be time-division according to the process. Since the compressor cannot be turned on and off frequently, it is necessary to delay the start and stop of the compressor. The process of starting the unit is the water pump, the four-way valve, the heating, the outdoor fan, the compressor, the compressor unit, the shutdown process, the compressor, the compressor, the outdoor fan, the four-way valve, the heating, the water pump, the multi-unit system, the compressor. Running wear balance is a very important issue. If the compressor running time is unbalanced, it will cause long running of the compressor.
In order to solve these problems, you can use the characteristics of the network platform to establish a token model for power-on shutdown. Through the bus hub, each unit controller takes turns to occupy the network and send its own information. This information includes the operating state operating mode set temperature and all temperature sensor temperature output status fault information, as well as the cumulative running time of each compressor. Since all compressor running time is sent to the network, each controller can be sorted from short to long depending on the cumulative running time of the compressor. Take the boot as an example. If a controller finds itself at the forefront and is in the shutdown state, it sends out the information of the snatch token. Once the token is robbed, it starts to boot according to the boot process. At this time, other controllers Is in the state of waiting for a token. After the controller with the token is powered on, the token is released, the token is robbed, and the other units waiting to start continue to snatch.
The defrosting control of the multi-unit is in the heating mode. In order to ensure the effective operation of the system, the defrosting of each unit is carried out independently. Each unit controller determines whether defrosting is required based on the outdoor ambient temperature defrosting sensor temperature and compressor operating time. If a unit determines that defrosting is required, first check through the network whether there are other units currently defrosting, and if so, continue to maintain heating until the defrosting unit exits the defrosting. When the unit enters the defrosting work, the defrosting sign is sent to the network, indicating that the unit is currently entering defrosting. The purpose of this is to prevent multiple units from entering the defrosting at the same time, resulting in insufficient heating.
Operational parameter setting query and fault alarm of the modular host system The central air conditioning control system is an automatic control system, and many parameters need to be set. Multiple unit controllers can be manipulated and set up with one or more operators, which can also be done by a computer. When manipulation and setup are required, the operator sends command data to each unit controller via the network, and is executed or saved by each controller.
Information such as the working status of each unit controller can be queried by an operator or a computer. In fact, each unit controller sends the relevant information to the network in real time, and the operator or computer only needs to receive and save the information to display and display the information. The fault information for each unit controller also needs to be sent to the network with the highest priority. After the unit fails, the fault code is quickly sent to the system network and processed accordingly.
The central air-conditioning main system that uses the network for multi-unit control can achieve a very high degree of centralized control. This kind of control party is ready for the world at present. The imitation method is also applicable to other types of central air conditioning systems, such as water-cooled water piping systems. The application of the bus in the indoor unit control is in the water pipe system, and the indoor end equipment generally uses the fan coil. There are also many types of fan coils. The application process of equipment control is described below. The indoor unit controller of the indoor unit controller is also a single-chip controller, and its control object is a fan coil.
In order to reduce the burden on the network, the indoor controller is passively transmitted on the network, that is, it is sent when it is required to send relevant data, and is usually in the receiving state. The automatic control system that is connected to the unit and the unit should achieve the unattended goal, as is the central air conditioning control system. In the past, central air conditioners needed special personnel to manage and turn them on or off every day. Since there is no connection between the unit and the indoor unit, there is often a phenomenon that the indoor end is turned on and the main unit is not turned on, or the indoor unit is not working and the main unit is lost. In order to achieve a good control effect, it is necessary to realize the linkage between the indoor unit and the host unit.
If the host unit is set to the linked state, the switch of the host unit is controlled by the indoor unit. The unit controller in turn queries the status of all indoor unit controllers in turn through the network. When an indoor unit is turned on, it returns the power-on status to the unit controller, and the unit controllers are connected to start up and enter the working state. If all indoor units are turned off, the unit controller is also turned off to avoid no load.
The application of the communication bus in the central air-conditioning control adopts many different modes from the traditional serial data bus, and overcomes some problems such as complicated installation address setting and the automation degree is greatly improved. At the same time, this method is very convenient for function expansion, such as interface with a computer, or extended telephone line remote control function. Since each controller node sends relevant data to the network, it is very convenient for fault detection and diagnosis. The network type modular air-cooled hot and cold water air conditioner controller and ground energy heat pump controller developed by Wuxi Huawei Refrigeration Co., Ltd. have been successfully adopted by many air conditioner enterprises at home and abroad. This product is not only reliable, powerful, but also easy to install and use.
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