Multivariable control for regulating high pressure centrifugal compressor with variable speed and IGV

Abstract

The objective of this paper is to develop a multivariable control system for a class of centrifugal compressors, which exploit as control signals both the rotational speed and the Inlet Guide Vane (IGV). Linear Quadratic Gaussian control with Integral action (LQGI) and Model Predictive Control (MPC) are investigated. The LQGI and MPC controllers are compared to a standard proportional integral (PI) controller, to regulate the discharge pressure of the compressor. The control algorithms are simulated and compared in different operating scenarios. Results demonstrate that the proposed multivariabe control schemes provide better performance than the single-loop PI controller, thus motivating the use of IGV for control purposes

Improved Modeling of a Multi-Level Inverter for TACS to Reduce Computational Time and Improve Accuracy

“…The turbo air compressor can be modeled using compressor maps derived through the computational fluid dynamics (CFD) analysis. The mechanical model of the turbo air compressor can be expressed by the corrected air flow rate m corr , pressure ratio PR, and corrected rotational speed N corr as follows [9]:…”

“…In particular, the multi-level inverter can operate medium voltage and high voltage induction motors, and is applied to large air compressor systems such as screw compressors and centrifugal turbo compressors. Centrifugal turbo air compressors have high operating efficiency, but have a narrow operating range of 70% to 100% [9].…”

“…A turbo air compressor system (TACS) consists of a centrifugal turbo compressor for air compression and an electric motor drive system (EMDS) for power transmission to the compressor. In order to improve the efficiency of TACS and expand the operating range, the variable speed drive (VSD) of the motor driven by the multi-level inverter and an inlet guide valve (IGV) control to modulate the operating range are applied [9,10]. The combination of VSD and IGV control should be verified by dynamic characteristics simulation as it may cause system instability due to control variable error, and surge and choke phenomenon [11].…”

Model Predictive Approaches for Active Surge Control in Centrifugal Compressors

“…The distance of the operating point, displayed as a red dot, from the SL and the SCL defines, respectively, the SD and surge control distance (SCD) [18], [22], [39]. The choke line (CL) is a maximum mass flow rate limit that, in contrast to the surge related lines, cannot be physically reached by the machine, and hence is not considered in the control problem.…”

“…The benefits to the industrial implementation are shown experimentally in [17], where it is observed that tuning the standard PI control for surge avoidance becomes extremely difficult in the presence of external disturbances, since a specific tuning for one scenario can be ineffective for all others. In [18], a linearized MPC is employed for a compression system, driven by a gas turbine, which controls the rotor speed and the inlet guide vane positioning. A configuration with a recycle valve is used in [19].…”