Nonlinear Optimal Control for a Gas Compressor Actuated by a Five-Phase Induction Motor
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1
Unit of Industrial Automation, Industrial Systems Institute, Rion Patras 26504, Greece
2
Department of ECS Engineering, Rensselaer Polytechnic Institute, New York 12065, USA
3
Department of Electrical Engineering, University of Setif I, Setif 19000, Algeria
4
Department of Innovation Systems, University of Salerno, Fisciano 84084, Italy
Power Electronics and Drives 2023;8(Special Section - Advanced Control Methods of Electrical Machines and Drives ):196-218
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ABSTRACT
The article proposes a nonlinear optimal control method for the dynamic model of a gas centrifugal compressor being actuated by a
five-phase induction motor (5-phase IM). To achieve high torque and high power in the functioning of gas compressors, 5-phase IM
appear to be advantageous in comparison to three-phase synchronous or asynchronous electric machines. The dynamic model of the
integrated compression system, which comprises the gas compressor and the 5-phase IM, is first written in a nonlinear and multivariable
state-space form. It is proven that the electrically driven gas-compression system is differentially flat. Next, this system is approximately
linearised around a temporary operating point that is recomputed at each sampling interval. The linearisation is based on first-order
Taylor series expansion and uses the computation of the Jacobian matrices of the state-space model of the integrated system. For the
linearised state-space description of the compressor and 5-phase IM, a stabilising optimal (H-infinity) feedback controller is designed.
This controller achieves a solution to the nonlinear optimal control problem of the compressor and 5-phase IM system under model
uncertainty and external perturbations. The feedback gains of the controller are computed by solving an algebraic Riccati equation at
each iteration of the control method. Lyapunov analysis is used to demonstrate global stability for the control loop. Additionally, the
H-infinity Kalman filter is used as a robust state estimator, which allows for implementing sensorless control for the gas compression
system.