Fig 1 - uploaded by Christoph Josef Backi
Content may be subject to copyright.
Schematic representation of a compressor with CCV, ψ indicates non-dimensional pressure and φ denotes non-dimensional flow
Source publication
In this paper we introduce an anti surge controller for a close-coupled valve (CCV) in a compression system. The controller is based upon feedback linearization in combination with linear state feedback. The mentioned CCV modifies the characteristics of the compressor, allowing it to be stably operated beyond the original surge line. It is shown th...
Context in source publication
Similar publications
In this letter, a compressive sampling system, which can acquire chirp signal without the prior information of carrier frequency and chirp rate, is proposed. The system first estimates the chirp rate based on windowed modulated wideband converter (MWC). When chirp rate is derived, the system can de-chirp the target signal. Then, the de-chirped sign...
Citations
... One can distinguish for instance several results on NMPC (nonlinear model predictive control), as well as on MPC which is applied to linearized models of the compressors [16][17][18][19]. Besides, one can note results on the use of global linearization-based control and state estimation-based control [20][21][22]. Additionally one can find results based on linearization around multiple equilibria and subsequent use of LMI techniques [23,24]. Usually the opening or closure of the compressor's inlet, outlet and retrofitting valves are used as control inputs [25][26][27]. ...
The article proposes a nonlinear optimal control approach for the dynamic model of a gas centrifugal compressor being driven by an induction motor (IM). The dynamic model of the integrated compressor-induction motor system, being initially expressed in a nonlinear and multivariable state-space form, undergoes approximate linearization around a temporary operating point that is recomputed at each time-step of the control method. The linearization relies on first-order Taylor series expansion and on the computation of the associated Jacobian matrices. For the linearized state-space model of the compressor-IM a stabilizing optimal (H-infinity) feedback controller is designed. This controller stands for the solution to the nonlinear optimal control problem of the compressor-IM under model uncertainty and external perturbations. To compute the controller’s feedback gains an algebraic Riccati equation is repetitively solved at each iteration of the control algorithm. The global stability properties of the control method are proven through Lyapunov analysis. Finally, to implement state estimation-based control of the compressor-IM, without the need to measure its entire state vector, the H-infinity Kalman Filter is used as a robust state estimator. The differential flatness properties of the compressor-IM system are proven. The article’s method provides one of the few algorithmically simple and computationally efficient solutions for the nonlinear optimal control problem of the compressor-IM system.
... Many researches of anti-surge systems are based on calculations using Greitzer model and similar one-dimensional mathematical models [19][20][21]. Despite the fact that surge is considered to be one dimensional instability, the influence of anti-surge system may lead to developing local two or three dimensional flow structures which cannot be observed in simple mathematical model. ...
In order to reproduce the near-surge operation of centrifugal compressor a series of numerical simulations in ANSYS CFX have been conducted. Different settings of boundary conditions have been investigated in purpose of providing a combination allowing to model surge without non-physical flow constraints. This, in turn, would be a step towards modelling of antisurge system. As the conclusions, it was observed that there is no possibility of simulating near-surge working regime without mass flow rate definition as a boundary condition. However, it is achievable to determine a throttle characteristic, which can be used as a function defining the outlet pressure and indirectly the mass flow rate. In case of transient simulations, it would allow to analyse both steady and unsteady regimes of the flow in a centrifugal compressor.
... A so-called close-coupled valve (CCV) as introduced in [20] can be used directly after the compressor assuming that no mass is stored in between these two units. The result is an 'equivalent' compressor, whose actuation (control) is the pressure drop across the CCV [3], [14]. ...
This paper presents a combined nonlinear model predictive control and moving horizon estimation strategy for active surge control in compression systems. The main advantage
of using model predictive control is the ability to include constraints, particularly on the actuators. The manipulated variables represent the pressure drop across the close-coupled valve (CCV) and the torque applied to the compressor shaft. Both manipulated variables are limited in magnitude and rate of change for real compression systems. Only positive values are feasible for both of them, for example. The performance of the control and estimation strategy is demonstrated in numerical simulations with added measurement and process noises.
