一种基于永磁同步电机绕组铜耗功率最大的电动汽车母线电容放电方法

A DC-bus Capacitor Discharge Method Based on Maximum Copper Consumption Power of Permanent Magnet Synchronous Motor Windings in Electric Vehicles

在电动汽车出现紧急情况时,母线电容电压需要迅速降低到安全电压,而传统基于泄放电阻放电的方法不仅体积大、成本高且可靠性低,针对这个问题,该文提出一种基于永磁同步电机绕组铜耗功率最大的电动汽车母线电容放电方法。建立基于永磁同步电机绕组作为能量泄放电阻的母线电容放电能量流动模型,并分析放电过程中稳态和瞬态能量流动过程。通过绘制放电过程中dq坐标系下的电流极限圆、电压极限椭圆和功率极限圆轨迹,在电磁功率小于绕组铜耗功率的约束条件下,获得绕组铜耗功率最大下的d轴和q轴电流轨迹。仿真和实验结果验证该方法可以实现母线电容的快速放电,省去复杂的泄放电路,减小驱动系统的体积;并相较于传统基于弱磁原理的放电方法放电时间更短,且母线电压不会出现浪涌。

In the emergency situation of electric vehicles,the bus capacitor voltage needs to be reduced to a safe voltage as soon as possible. The traditional discharge method of bleeder resistance is large in size, high in cost, and low in reliability. To solve this problem, this paper proposed a method for discharging electric vehicle bus capacitors based on permanent magnet synchronous motor windings with the largest copper power consumption. The DC-bus capacitor discharge energy flow model based on permanent magnet synchronous motor windings as energy discharge resistance was established, and the steady-state and transient energy flow processes in the discharge process were analyzed. Through drawing the current limit circle, voltage limit ellipse and power limit circle trajectory in the dq coordinate system during the discharge process, the d-axis and q-axis currents trajectories at the maximum winding copper power consumption were obtained under the constraint condition that the electromagnetic power was less than the windings copper consumption power.Simulation and experimental results verify that this method can achieve rapid discharge of bus capacitors, eliminate the complex bleeder circuits, and improve the power density of the drive system. Compared with the traditional discharge method based on the principle of magnetic field weakening, the discharge time is shorter without DC-bus voltage surge.