主动磁悬浮轴承在余热发电机的应用研究

针对传统余热发电设备存在发电效率低、成本高、体积大等问题，设计了一款装备5自由度（5-DOF）主动磁悬浮轴承的余热发电机，用于余热发电有机朗肯循环系统. 首先，基于电机转子轴径限制和最大承载力要求，确定径向磁悬浮轴承和轴向磁悬浮轴承的结构形式，采用一维磁路模型和二维有限元分析，计算并校核磁悬浮轴承的尺寸和性能参数；其次，为保证磁悬浮轴承的稳定裕度，采用三电平PWM功率放大器降低输出电流纹波，利用不完全微分PID控制器和不平衡补偿算法实现5自由度稳定悬浮；最后，将该磁悬浮余热发电机应用到实际客户现场，从稳定裕度、承载力和轴振峰峰值3个维度验证磁悬浮余热发电机的可靠性. 现场试验结果表明:磁悬浮余热发电机系统运行稳定可靠，实现了满功率发电和长期运行考核；在全工况运行范围，磁悬浮轴承系统的灵敏度函数小于12 dB，余热发电机转子振动峰峰值小于53 μm，满足ISO14839-3规定的长期稳定运行要求；轴向承载力最大达到3 600 N，满足实际工况需求. 

Application of Active Magnetic Bearing in Waste Heat Generator

Aiming at the problems of low efficiency, high cost and large volume of the traditional waste heat power generation equipment, a waste heat generator equipped with the 5-DOF (5-degree of freedom) active magnetic bearing for Organic Rankine waste heat generation system was designed. Firstly, based on the rotor diameter limit and maximum bearing capacity requirements, the structural forms of radial and axial magnetic bearings were determined. Furthermore, the dimensions and performance parameters of magnetic bearings were calculated and checked by one-dimensional magnetic circuit model and two-dimensional finite element analysis. Secondly, in order to ensure the stability margin of the magnetic bearing, a three-level PWM (pulse-width modulation) power amplifier was used to reduce the output current ripple, and an incomplete differential PID controller incorporated with unbalance compensation were used to realize the 5-DOF stable suspension. Finally, the waste heat generator equipped with magnetic bearing was applied to the actual customer site. The reliability of the waste heat generator was verified from three dimensions of stability margin, bearing capacity and shaft peak-to-peak value. The field test results show that the waste heat generator system has operated stably and reliably in all operation conditions, and can achieve full-power generation and long-term operation. The sensitivity function of the magnetic bearing system is less than 12 dB, and the peak-to-peak vibration value of the rotor of the waste heat generator is less than 53 μm, which meet the long-term stable operation requirements of ISO14839. The maximum axial bearing capacity reaches 3 600 N, which meets the requirements of actual working conditions.