变频多联机系统控制策略及可靠性试验研究

发布时间：2019-05-01 06:47

【摘要】：变频多联机是目前中央空调市场主流的产品之一,近年的发展更是非常迅猛。目前多联机的可靠性方面的研究还属于起步阶段,本文主要是从多联机系统控制策略设计及系统选型方面对多联机可靠性的影响进行研究,主要采用试验的方法,先进行控制及制冷系统设计,通过一些理论计算分析,再配合大量可靠性实验来验证。这个过程虽然很耗时,但从目前的情况来看不失为是一种有效的手段。本文主要从控制、制冷系统、结构等几个方面展开可靠性实验,具体如下：控制策略：对于变频多联机系统的控制是比较复杂的过程,本文主要针对其中对于可靠性影响最重要的几个方面进行研究及试验验证,主要有机组的启动、除霜的运转、对油的控制、相关的系统保护、压缩机的驱动的设计。除此之外控制逻辑决定了系统运行的稳定性和可靠性,它的设定主要是围绕以压缩机为主的制冷系统进行,保证系统没有回液、没有回油,使压缩机能够正常运转,在系统缺少冷媒的时候能够有效进行保护停机,不会使压缩机过热损坏。通过试验证明控制的策略及方案可以保证系统可靠运行选型方面：包括压缩机、换热器、膨胀阀、油分离器、气液分离器、四通阀等主要部件。在这些部件里面,压缩机是设计的核心,系统的回路、控制的方案很大程度上都是围绕着压缩机而展开的。回路中的一些保护是以压缩机的运行范围而设定,压缩机的驱动要保证压缩机最大限度稳定运转,不过流、不退磁,控制逻辑是系统运行的大脑,其设定同样是围绕压缩机进行,保证系统没有回液,使压缩机能够正常运转,在系统缺少冷媒的时候能够有效进行保护停机,不会使压缩机过热损坏。结构设计方面,通过软件进行应力分析,初步设计好结构之后,再进行应力、噪声等方面的测试,通过测试的结果对钣金、铜管等结构部件进行优化。本文主要从控制策略为主的几个方面进行变频多联机系统设计,并通过大量的试验进行确认。在控制策略方面采用了逐级递增的压缩机启动方式,系统能够有效稳定的启动,除霜的过程采用智能控制有效地避免误除霜,提升了除霜运行的可靠性,同时采用定时回油循环,保证系统运转过程中压缩机不会缺油,对于压缩机的保护从温度、压力、电流三大方面进行,采用了先限、后降、再停的方式,最大限度保证系统运转又能有效进行保护,提高可靠性；系统的零部件选型主要是采用不重新发明轮子的方式,选择市场经过大量应用的零部件,以保证可靠性。结构方案主要是从噪声、振动、应力三个方面进行,采用了先建模、测试、改善的方法进行,有效地保证了系统运行的可靠性。
[Abstract]:Frequency conversion multi-on-line is one of the mainstream products in the central air-conditioning market at present, and the development in recent years is very rapid. At present, the research on reliability of multi-on-line is still in the initial stage. This paper mainly studies the influence of control strategy design and system selection of multi-online system on the reliability of multi-on-line, mainly using the method of experiment. The design of control and refrigeration system is carried out firstly, and verified by some theoretical calculation and analysis, and then with a large number of reliability experiments. This process, though time-consuming, is an effective tool in the light of the present situation. This paper mainly from the control, refrigeration system, structure and other aspects of reliability experiments, as follows: control strategy: for the frequency conversion multi-on-line system control is a more complex process, This paper mainly focuses on the most important aspects of reliability, such as the start-up of unit, defrosting operation, oil control, system protection and compressor drive design. In addition, the control logic determines the stability and reliability of the system operation, its setting is mainly around the compressor-based refrigeration system, to ensure that the system does not return fluid, there is no return of oil, so that the compressor can run normally. In the absence of refrigerant in the system can be effectively protected shutdown, will not overheat the compressor damage. It is proved by experiments that the control strategy and scheme can ensure the reliable operation and selection of the system, including compressor, heat exchanger, expansion valve, oil separator, gas-liquid separator, four-way valve and other main components. In these components, the compressor is the core of the design, the loop of the system, the control scheme is developed around the compressor to a large extent. Some of the protection in the circuit is based on the operating range of the compressor, the compressor drive to ensure the maximum stable operation of the compressor, but the flow, not demagnetization, control logic is the brain of the operation of the system. Its setting is also around the compressor to ensure that the system does not return fluid, so that the compressor can run normally, in the absence of refrigerant in the system can effectively protect the shutdown, will not make the compressor overheat damage. In the aspect of structural design, stress analysis is carried out by software, after preliminary design of the structure, stress, noise and other aspects are tested. The structural components such as sheet metal, copper pipe and so on are optimized by the test results. In this paper, the design of frequency conversion multi-on-line system is carried out mainly from several aspects of control strategy, and confirmed by a large number of experiments. In the aspect of control strategy, the compressor start-up mode is adopted step by step increasing step by step, the system can start up effectively and stably, and intelligent control is adopted to effectively avoid misdefrosting and improve the reliability of defrosting operation. At the same time, the timing oil return cycle is adopted to ensure that the compressor will not be short of oil during the operation of the system. The protection of the compressor is carried out from the three aspects of temperature, pressure and current, adopting the way of first limit, then drop, and then stop. Ensure the operation of the system to the maximum extent and can effectively protect and improve the reliability; The selection of parts and components of the system mainly adopts the way of not reinventing the wheel to select the parts which have been widely used in the market in order to ensure the reliability. The structural scheme is mainly carried out from the three aspects of noise, vibration and stress. The method of modeling, testing and improving is adopted to ensure the reliability of the system.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TB657.2

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