ALGORITHM FOR ESTIMATION OF SHIPREFRIGERATION UNITENERGY EFFICIENCY USING FULL ORDER OBSERVERS

Abstract

The article considers the construction of an algorithm for estimation the energy efficiency of a ship refrigeration unit using the minimum required number of sensors. It is established that the existing methods for diagnosing and monitoring the technical condition of ship refrigeration units are imperfect due to the presence of a large number of sensors and the necessity to suspend the unit. The choice of the refrigeration coefficient as an indicator of energy efficiency is justified. A method that allows determining the refrigeration coefficient in real time without the necessity to stop the operation of the ship's refrigeration unit and use pressure sensors is proposed. For this, the method supposes the calculation of the specific cooling capacity and compressor compression work, the mechanical power on the shaft and the mass flow rate of the refrigerant. The algorithm for determining the cooling capacity and compression work using only four temperature sensors is considered. This algorithm supposes the determination of enthalpies at characteristic points of the refrigeration cycle using the equations of the refrigerant state. A method for evaluating the mechanical power on the compressor shaft using full order adaptive state observers is proposed. A decision of using the electromagnetic torque of the compressor motor as a measured quantity is substantiated. A state observer is synthesized using a modal method based on a linearized model of the electric motor. An expression for calculating the geometric mean root and elements of the observer matrix is proposed. The resulting observer structure allows constructing it on the basis of a complete mathematical model of the electric motor and evaluating not only the speed, but also the load torque on the compressor shaft. In the environment of Matlab / Simulink, a simulation model of the compressor motor state observer is built. The obtained simulation results confirm the efficiency of the proposed method. An algorithm for determining the electromechanical parameters of a compressor for a given period of time using three voltage and current sensors is considered. A general algorithm for estimation energy efficiency, which can be the basis for creating a system for diagnosing and monitoring the technical condition of a ship refrigeration unit, is constructed.