Abstract
Abstract The heating pipe network system with such dynamic characteristics as nonlinearity and large time lag may cause hydraulic disorder. To solve this problem, this paper proposes a unit control-based hydraulic equilibrium control strategy, which constructs an equilibrium regulation system for heating pipe networks by optimising the inlet device of each unit and using a novel control theory. By developing a cascade control system to control the return water temperature and the pressure difference between supply and return water of the branches at each unit of the pipe network, we were able to stabilise the pressure and control the temperature. Then, we used the averaging control theory to set the parameters of regulation systems between each unit. The research results indicate that, compared to the traditional single-loop negative-feedback return water temperature control system, the cascade averaging controller has a better control effect than the single-loop PID controller. This is because it has a smaller overshoot and can cope with system interference factors quickly. Therefore, the temperature of return water between each unit can be coordinated and fluctuation is within a smaller range. This effectively eliminates the influence of static and dynamic hydraulic disorder on entire system stability.
Highlights
In an urban heating pipe network, intelligent regulation and equilibrium control are the core of the entire system operation [1], and the control condition will greatly affect the power and heat consumption of the entire heating system [2]
According to the real monitored point number of hydraulic equilibrium regulation system based on unit control, in order to ensure that PLC terminal number accounts for 10–20% margin of total point number, the S7-200 SMART PLC’s CPU module is selected as SR30, the on-off input/output is 18 points/12 points and input/output form is DC 24 V input/AC 220 V relay output
The averaging control idea is adopted to set the parameters of the regulation system between each unit
Summary
In an urban heating pipe network, intelligent regulation and equilibrium control are the core of the entire system operation [1], and the control condition will greatly affect the power and heat consumption of the entire heating system [2]. To improve hydraulic disorder in the heating pipe network, a various types of research have been carried out in the industry, and a lot of hydraulic equilibrium regulation methods have been raised. Common regulation methods include a proportional regulation method, compensational regulation method, return water temperature method etc. The return water temperature method is simpler. It only takes return water temperature as a regulating target. The traditional return water temperature method has the weaknesses of regulating time delay and indoor temperature not fully represented by return water temperature. This paper puts forward an automatic levelling scheme that can remedy the demerits of the traditional return water temperature method
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