Flow control system and control method

Abstract

The invention provides a flow control system and a control method. Firstly, a small signal disturbance [delta]F is applied to the pump operating frequency at any relative steady state moment of the flow control system, and the relationship between a corresponding flow change value [delta]q(t) and a relative steady state pressure value P is obtained. A time constant of [delta]q(t) is acquired, andthen the pressure P is obtained. Secondly, a head characteristic curve of each pump passing through a point (Q, P) on a Q-H plane and the point of intersection of the head curve and a corresponding efficient interval boundary are obtained. Thirdly, high-efficiency operating performance parameters are obtained, and then the pump with the best performance parameters is selected to work so as to ensure that the flow control system is operating efficiently. According to the invention, the high-efficiency operation control of the flow control system can be achieved with no pressure detecting sensoror auxiliary circuit, the time and cost required for the installation and debugging of the pressure sensor and the auxiliary processing circuit are saved, so that the system structure is simpler, thesystem cost is lower and the operation efficiency is higher, the service life and reliability of the system are improved, and reliable guarantee is provided for safe and efficient operation of the flow control system.

Description

technical field [0001] The invention belongs to the field of process control, and in particular relates to a flow control system and a control method, which realize efficient operation of the flow control system. Background technique [0002] Flow regulation control is widely used in chemical industry, food, medicine, water supply and other fields. Early flow control mainly adjusts the output flow by adjusting the opening of the control valve, but there are disadvantages such as high energy consumption and small adjustment range. At present, the speed-regulating pump is mainly used to adjust the output flow. The principle is mainly to detect the deviation between the output flow and the set flow, and perform a feedback compensation control algorithm on the deviation, and then adjust the output frequency of the inverter to change the pump. The rotating speed can realize the stable control of the output flow. However, according to Zhang Chenghui et al. published in the Journ...

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Problems solved by technology

[0003] However, the operating state of the flow control system is not constant, and its output flow and head are time-varying in time, which cannot guarantee that the pump will always run in the high-efficiency range

On the one hand, in the fields of chemical industry, food, medicine, water supply, etc., due to the long-term operation of the transported liquid in the pipeline, there may be dirt deposits, resulting in a smaller effective cross-sectional area of ​​the entire pipeline and poor pipe resistance characteristics. In the case of flow rate, the pressure at the pump outlet and the pipe network increases sharply, resulting in changes in the operating state of the pump, which may deviate from the high-efficiency range; As a result, the operating state of the pump changes, which may deviate from the high-efficiency range; on the other hand, the output flow of the flow control system is subject to the actual system working state or different working stages, resulting in changes in the pump operating state, which may deviate from the high-efficiency range; Running in the non-efficient range for a long time will reduce the efficiency of the variable frequency flow control system, and even lead to overload / low frequency operation of the frequency converter and the pump, increasing the risk of failure of the variable frequency flow control system

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