Abstract
To improve the operating performance of electric propulsion ships, the permanent magnet synchronous motor is commonly used as the propulsion motor. Additionally, position estimation without sensors can further improve the application range of the propulsion motor and the estimated results can represent the redundancy of measured values from mechanical sensors. In this paper, the high-frequency (HF) injection algorithm combined with the second-order generalized integrator (SOGI) is presented on the basis of analyzing the structure of the electric propulsion ship and the vector control of the motors. The position and rotor speed were estimated accurately by the approximate calculation of q-axis currents directly related to the rotor position. Moreover, the harmonics in the estimated position were effectively reduced by the introduction of the second-order generalized integrator. Then, the rotor position estimation algorithm was verified in MATLAB/Simulink by choosing different low speeds including speed reversal, increasing speed, and increasing load torque. Finally, the correctness of the proposed improved high-frequency injection algorithm based on the second-order generalized integrator was verified by the experimental propulsion permanent magnet synchronous motor (PMSM) system at low speed.
Highlights
The electric propulsion ship has the advantages of compactness, environmental emission reduction, economic fuel consumption, and superior reliability, which constitute an important developing trend of the green ship in the future
The permanent magnet synchronous motor (PMSM) was used as the prime motor to drive the propeller in the electric propulsion ship system
It can be seen that the propeller input is motor speed and ship velocity, and the load of propulsion is the ship hull driven by the propeller and the load is impacted by the ocean environment [20]
Summary
The electric propulsion ship has the advantages of compactness, environmental emission reduction, economic fuel consumption, and superior reliability, which constitute an important developing trend of the green ship in the future. In the PMSM, the HF injection algorithm is insensitive to motor parameter changes and can obtain accurate rotor position and speed at low and zero speed [13]. At present, the HF injection algorithm can only be used to estimate the rotor position of the PMSM at low and zero speed [15]. We took the three-phase PMSM commonly used in electric propulsion ships as an example and analyzed the HF injection sensorless control method at low speed by combining the structures of the electric propulsion ship system with the basic principle of motor vector control. The improved HF voltage injection algorithm based on the SOGI was adopted to obtain accurate rotor position and speed by estimating q-axis currents. An experimental PMSM setup in an electric propulsion ship system was built to verify the validity of the proposed position sensorless control strategy
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