主动电磁轴承电流型开关功率放大器的调制技术

Modulations of Current-mode Switching Power Amplifier for Active Magnetic Bearings

功率放大器作为主动电磁轴承中的重要环节,其性能的好坏对主动电磁轴承系统有着较大的影响。目前主动电磁轴承系统大多采用电流型开关功率放大器,电流型开关功率放大器的性能除了与电流控制器的参数有关外,与调制技术也有非常大的关系。对目前使用最多的三角波比较法、滞环比较法及采样保持法等3种调制技术进行比较研究。在介绍每种调制技术运行原理的基础上,对其静态性能、动态性能和谐波含量等特性进行重点的分析。利用Simulink建立仿真模型并制作试验样板,仿真与试验的结果表明:与滞环比较法、采样保持法相比,三角波比较法的开关频率恒定、谐波含量少、可靠性高,其综合性能比较好,对主动电磁轴承用功率放大器的设计制作有一定的指导意义。

As an important part in the active magnetic bearing,its performance has great impact on the active magnetic bearing system.Most of the active magnetic bearing systems use current-mode switching power amplifiers.Besides the parameters of current controller,modulation techniques play an important role in the performance of current-mode switching power amplifiers.A comparative study is made among three most widely used modulation techniques,i.e.triangle wave comparison method,hysteresis comparison method and sample-and-hold method.Based on introducing the operating principle of three modulation techniques,their static performance,dynamic performance and harmonic content are analyzed.Simulation models are built by using Simulink and prototypes of the three power amplifiers.The results of simulations and experiments show that the triangle wave comparison method has the best performance due to constant switching frequency,less harmonic content and high reliability.The conclusions have some guiding significance to the design of current-mode switching power amplifiers for active magnetic bearings.