Research On The Propeller Load Simulation System Based On Brushless DC Motor

With the development of ship propulsion technology, the electric propulsion systems will be widely used. In order to reduce the cost and risk, it is important to establish a simulation system in the laboratory, which test the electrical performance of propulsion motor, and the controller of the converter in the simulation environment repeatedly. Brushless dc motor(BLDCM) uses electronic commutation to replace the mechanical commutation. It Makes up for the deficiency of the dc motor, and absorbs the advantages of ac motor. Combined with its small size, and low cost, it has important research value to select BLDCM as a load motor to design load simulation system.For this purpose, this paper selects BLDCM as the load motor, and designs two sets of propeller load simulation systems. This paper makes detailed analysis and research of the two simulation systems.First of all, according to the propeller characteristics and the mutual influence between ship and propeller, the model of ship-propeller is established. This model lay the foundation for establishing the propeller load simulation system.Then, this paper analyzes the structure and principle of BLDCM, and completes its mathematical model and simulation model. This paper analyzes the Direct Torque Control(DTC) scheme, which used in BLDCM. Because of the conduction characteristics of BLDCM which only use two windings, this paper proposes a DTC scheme which omit flux hysteresis loop, and explain the reason. The traditional zero vector causes big torque ripple and can't control torque in the power state. Because of these shortcomings, this paper puts forward a new kind of zero vector. Through the simulation model, the new zero vector in the DTC is proved effective. This paper analyzes the working principle of PWM inverter, and adopt SVPWM modulation method to realize the function of the energy recycled. The double PWM back-to-back load simulation system is seted up.In order to reduce the size of system, and simplify the control method, another load simulation system, which based on matrix converter is proposed. This paper analyzes the basic principle and structure of the matrix converter, and completes its mathematical model.According to the characteristics of the BLDCM. this paper proposes a method based on indirect vector modulation, achieved the combination of matrix converter and direct torque control. The load simulation system which based on matrix converter is seted up.Finally, combining with the ship-propeller model, two sets of the propeller load simulation systems are established. The simulation results show that the two systems can be successfully completed the propeller load task with energy recycled. The rationality of the design of the two systems, and the effectiveness of the proposed control schemes are proved.