Research and Application in drive cabinet project of anti-interference design in Absorption Sphere Shutdown System of HTR-PM

[Background] Stepper motor driver is the main equipment of the cabinet of Absorption Sphere Shutdown System of HTR-PM, which can control the stepper motor to act according to the preset value, if it works abnormally due to the influence of interference, it will cause the stepper motor to run unexpectedly, which may cause the risk of the absorption sphere falling or refusing to fall by mistake and affect normal operation or nuclear safety of Nuclear Power Plant. [Purpose]The stepper motor driver adopts pulse width modulation(PWM) technology, accepts the weak current pulse instruction, converts the input 220VAC rectification into direct current（DC）, and then inverts and modulates it into a high-voltage pulse signal to control the rotation angle and running speed of the stepper motor, and the output of pulse width modulation contains a large number of high-order harmonic components, which causes pollution and impact to the power grid and grounding system, and causes interference to the weak current control signal in the system and causes abnormal operation of the stepper motor. In this project, the stepper motor driver is not only the source of interference, but also the object of interference, and there are inherent difficulties in the anti-interference design, through research and analysis, a scientific and reasonable anti-interference scheme is formulated, which effectively reduces the pollution and impact of the power grid and grounding system caused by the PWM mechanism, and avoids the abnormal operation of the stepper motor driver. [Methods] Through theoretical calculations and practical tests, this study thoroughly studied the transmission path, mechanism and influence degree of interference caused by PWM, and designed customized optoelectronic isolation equipment. Dedicated reactor and filter are arranged on the corresponding interference source transmission path, which effectively blocks the interference propagation and suppresses the influence of interference, which conforms to the unique working environment of the cabinet of the absorption sphere shutdown drive mechanism. [Results] The anti-interference design scheme of the cabinet project of the absorption sphere shutdown drive mechanism effectively suppresses the impact of interference on the system, ensures the accurate and stable operation of the stepper motor driver, and realizes the angle deviation of the stepper motor within 1°for every 20*360° operation, which effectively prevents the risk of malfunction of the stepper motor and improves the reliability of the system operation. [Conclusions]This research scheme has a good guiding significance for the anti-interference design of various control systems of the same type, and has certain promotion significance.

[背景] 步进电机驱动器是高温气冷堆核电站示范工程（HTR-PM）吸收球停堆系统（Absorption Sphere Shutdown System）机柜的核心设备，可依据预设值控制步进电机动作。若受干扰影响导致其工作异常，将引发步进电机意外运行，可能造成吸收球误落或误拒落风险，进而影响核电站正常运行或核安全。

[目的] 步进电机驱动器采用脉冲宽度调制（PWM）技术，接收弱电脉冲指令，将输入的220伏交流电整流为直流电（DC），再经逆变调制生成高压脉冲信号，以控制步进电机的旋转角度与运行速度。然而，脉冲宽度调制输出含大量高次谐波分量，会对电网及接地系统造成污染与冲击，同时干扰系统内弱电控制信号，导致步进电机异常运行。本项目中，步进电机驱动器既是干扰源又是被干扰对象，抗干扰设计存在固有难点。通过研究分析，制定科学合理的抗干扰方案，可有效降低PWM机制对电网及接地系统的污染与冲击，避免步进电机驱动器异常运行。

[方法] 本研究通过理论计算与实际测试，深入探究PWM引发干扰的传输路径、机理及影响程度，并设计定制化光电隔离设备。在对应干扰源传输路径上配置专用电抗器与滤波器，有效阻断干扰传播并抑制干扰影响，以适配吸收球停堆驱动机构机柜的独特工作环境。

[结果] 吸收球停堆驱动机构机柜工程的抗干扰设计方案有效抑制了干扰对系统的影响，保障步进电机驱动器精准稳定运行。步进电机每运行20×360°，角度偏差控制在1°以内，有效防范了步进电机误动作风险，提升了系统运行可靠性。

[结论] 本研究方案对同类各控制系统的抗干扰设计具有良好指导意义，且具备一定推广价值。