A Novel Algorithm Based on Polynomial Approximations for an Efficient Error Compensation of Magnetic Analog Encoders in PMSMs for EVs

This paper presents a novel algorithm based on polynomial approximations (PAs) for an efficient error compensation of magnetic analog encoders (MAEs) in permanent-magnet synchronous machines (PMSMs) intended for electric vehicle (EV) propulsion. The proposed PA algorithm requires a negligible memory space compared to a very high-resolution look-up table (LUT). The use of polynomials allows compensating every possible input rotor position without carrying out an interpolation or a rounding to the nearest quantized value. The PA algorithm has been implemented to work in real time on a TM4 EV drive controlling an 80 kW PMSM. The performance of the algorithm has been validated at 6000 and 9000 r/min under +85 and +/-55 Nm of torque, respectively. The electromagnetic interference (EMI) effects have been minimized using a type-2 phase-locked loop (PLL). The proposed PA algorithm assisted with the PLL is capable of reducing the total position error to a range as small as +/-0.2 degrees. The combination of these two algorithms is a promising solution for compensating the position error in quadrature analog encoders. The experimental results obtained with the 80 kW PMSM demonstrate the feasibility of low-cost MAEs for achieving high-performance field-oriented control (FOC) of PMSMs in EV drives.

本文提出了一种基于多项式近似（PAs）的新算法，用于对电动汽车（EV）驱动用永磁同步电机（PMSMs）中的磁性模拟编码器（MAEs）进行高效误差补偿。与超高分辨率查找表（LUT）相比，所提出的多项式近似算法所需的存储空间可忽略不计。利用多项式可以对每一个可能的输入转子位置进行补偿，而无需进行插值或舍入到最接近的量化值。该多项式近似算法已在控制一台80kW永磁同步电机的TM4电动汽车驱动器上实时实现。该算法的性能已分别在转速为6000转/分钟和9000转/分钟以及扭矩为 +85牛米和±55牛米的条件下得到验证。通过使用二阶锁相环（PLL），电磁干扰（EMI）的影响已降至最低。所提出的由锁相环辅助的多项式近似算法能够将总位置误差降低到小至±0.2度的范围。这两种算法的结合是对正交模拟编码器位置误差进行补偿的一种有前景的解决方案。通过80kW永磁同步电机获得的实验结果证明了低成本磁性模拟编码器用于实现电动汽车驱动器中永磁同步电机高性能磁场定向控制（FOC）的可行性。