Centrifugal Compressor Anti-Surge Control Using A Closed-Coupled Valve

Centrifugal compressor is a large essential equipment which is widely used in metallurgy, petroleum chemical industry et al. Centrifugal compressor has a lot of merits, such as high pressure rise, suitability for small flow situation and so on; but it also has the drawbacks which are difficult to overcome by itself, such as low efficiency, easiness to surge and so on. Although the traditional anti-surge passive control can guarantee the security of compressor, but actually it seriously influences on the operating region of compressor.Active control has been presented for resolving the problem mentioned above, the shape of compressor characteristic curve or the pipeline characteristic curve are changed by introducing active controller, which makes centrifugal compressor stable under any mass flow. For the reasons of simple structure and conspicuous effect, closed-coupled valve is considered the most prospective active controller at present. But the introduction of the closed-coupled valve also brings the problem of increasing energy consumption at the same time, which influences the application in practical. This paper obtains from several following aspects, attempts to solve the problems mentioned above.First, through the analyzing of energy losses principles in centrifugal compressor, the function expression of compressor characteristic map is established; and a three-order nonlinear model is established by using the mass balance and momentum balance, which makes the foundation for the controller design and the control strategy research.Next, for the problem of increasing energy consumption when using closed-coupled valve, and integrating with the characteristic of nonlinear system, variable-structure control strategy is adopted to achieve the aim of saving energy and consumption, when compressor operates in stable region applying PI control, and when compressor operates in surge region implementing active control by using closed-couple valve. Lyapunov stability theory is used in this paper to establish the stability of the closed-loop system after using closed-coupled valve, and SIMULINK is used to simulate the whole system.In addition, in order to examine the effect of the control strategy, the function of DDE communication between MATLAB and KINGVIEW is also used to establish the simulation platform, which demonstrate the simulation results through visible form, and makes it more directive.