Research On Essential Technology Of High Efficiency Synchronous Rectification Of Motor

To effectively improve the alternator efficiency of automobile and satisfy the high-power demand brought by the increasing overall reform of vehicle automation and intellectualization,it is of great significance to carry out in-depth and comprehensive research on the technology of automotive power generation.Synchronous rectification technology utilizes the power MOSFET with lower on voltage drop and on resistance to replace the traditional diode,which effectively reduces the conduction loss and greatly improves the rectification efficiency.It has been widely used in consumer and industrial power generation and power supply systems.It has become a research hotspot so far to implement synchronous rectification technology to automotive alternator system,which can effectively improve alternator efficiency,improve fuel economy and reduce exhaust emissions.However,affected by speed fluctuation,commutation overlap,parasitic parameters and load mutation,the conventional synchronous rectification control technology cannot meet the requirements,so it is necessary to carry out research from the aspects of motor model,control algorithm and miniaturization.Taking the traditional generator configuration and the belt driven starter generator（BSG）configuration under the hybrid architecture as the application scenario,this dissertation focuses on the research goal of high efficient synchronous rectification of motor.The synchronous rectifier control algorithms in both configurations need to emphasize the setting of speed sampling and safe conduction time,and the BSG configuration needs to consider the influence of load response on synchronous rectifier.Firstly,the theoretical model and numerical model of automotive excitation generator rectifier system are analyzed.Accordingly,the design idea of synchronous rectifier control algorithm under two configurations is given.At the same time,the influence of excitation circuit on synchronous rectification of BSG configuration is analyzed,and the auxiliary strategy of synchronous rectification is given.Then,based on model-based development（MBD）,the development and iteration of two control algorithms and auxiliary strategies are realized with the help of joint simulation platform.Based on the drain-source source voltage sampling,the specified driver chip for motor synchronous rectification of sensorless self-driven is designed and verified.Based on phase voltage sampling,design of experiments and neural network training,the development and verification of BSG synchronous rectifier controller are completed.The main work and innovations of this dissertation are as follows:1.Direct frequency tracking（DFT）synchronous rectification control technology is proposed.The relationship model between the v _DS of switch and the safe conduction time of synchronous rectification is established.The speed signal is real-timely analyzed,and the gate driving signal with safe conduction time which changes smoothly with the speed is generated,realizing the direct frequency following and real-time synchronous rectification control.This technology does not need additional speed detection circuit or angle sensor,which ensures the normal operation of synchronous rectification in the case of oscillation and spikes in the circuit.Based on this model,the cross domain joint simulation of mechanical/electrical/control is completed in the Simulink/System Generator development environment,and the DFT algorithm is developed.Based on this algorithm,a synchronous rectification drive chip is designed and trial manufactured for six phase traditional generator.The DFT controlled synchronous rectification function in the range of 0～150 A output current and 1600-10000 r·min^-1 speed is performed on the alternator test bench.Compared with the traditional diode rectifier,the Verband der automotive industry（VDA）standard alternator efficiency this technology is improved by8%.2.Adaptive conduction time（ACT）synchronous rectification control technology is proposed.The idea of ACT is to establish the mapping relationship between conduction time,current and speed.Based on this,taking BSG motor as the research object,with the help of design of experiments method,a large number of data of current,speed and conduction time are obtained.Based on the experimental data,the optimal conduction time prediction model under the whole load current and speed range is obtained through back propagation（BP）neural network training,and the synchronous rectification control of adaptive conduction time is realized.This technology ensures the normal function of synchronous rectification during commutation overlap.Based on this model,the ACT algorithm is developed on the joint simulation platform,the design and development of six phase BSG motor controller are completed,and the ACT synchronous rectification function in the range of 20～180 A output current and 1400～6000 r·min^-1 speed is realized on the bench.The peak alternator efficiency of this technology can reach 84.47%.3.Multi state identification（MSI）load response control technology is proposed.The idea of MSI is to establish the relationship between output voltage state and excitation loop control.Taking BSG as the research object,the load response control of multi state identification is realized by identifying the output voltage state,calculating the steady-state duty cycle in real time,judging the type of load change condition,and determining the entry and exit time of load response control.This technology can avoid triggering load response control when entering synchronous rectification,and prevent synchronous rectification oscillation before and after load mutation.Based on this technology,a six phase BSG motor controller is built.The test bench results show that MSI load response control realizes the above functions.Through the above two control technologies and one auxiliary technology,high alternator efficiency can be obtained in two application scenarios,which is helpful to promote the application of synchronous rectification in automotive alternators and realize energy conservation and emission reduction.