Research On High Frequency Link Drivefor Brushless DC Motor

With the increasing global energy consumption, the crisis of energy shortage has became more and more serious. As a result, as energy efficient and environmentally friendly vehicles, electric vehicles will be widely applied. However, the electric drive system of electric vehicle has such disadvantages as big volume, heavy weight, low power and density et al. In order to improve the performance of electric drive system of electric vehicle, in this paper, a high-frequency link drive for drive brushless DC motor(BLDCM) of electric vehicle is proposed, characterized by bi-directional power transmission, high efficiency, small size, light weight, low noise and high power density advantages.In this paper, firstly with the high-frequency link matrix converter driving brushless DC motor as the research object, the working principle and main circuit of high-frequency link with BLDCM in two- two conduction mode is analyzed. According to the character of bidirectional switch in the matrix converter, using the decoupling idea, a novel two-two conduction hybrid pulse wide modulation(HPWM) strategy applicable to BLDCM load is proposed. In addition, the working modes of high-frequency link inverter of pre-transformer in the high-frequency switch cycle are also analyzed in detail.Secondly, the high frequency link matrix converter drive BLDCM in the three-three conduction mode are discussed and studied in this paper, with another three-three conduction HPWM modulation strategy puted forward as well as analysis and simulation of circuit working modes. Based on the large output torque of two-two conduction BLDCM and small three-three conduction torque ripple, a two-two starting and three-three running strategy is proposed. By using Matlab/Simulink software, a detailed simulation and analysis is carried out, the optimal switching time from two-two conduction mode to three-three conduction mode is obtained.Moreover, the direct torque control without flux linkage for high-frequency link matrix converter with BLDCM is studied, followed by the simulation verification of the feasibility of the above theories.Finally, the hardware and software of the entire system are designed in detail, on the basis of the design, the experiment platform for high frequency link matrix converter with BLDCM is established, with DSP and CPLD as control core. Through digital control, the experimental verification of the entire system is completed. In this way, the feasibility and rationality of the experimental design for the control strategy for high frequency link matrix converter with BLDCM are verified.