Implementing a finite-state off-normal and fault response system for disruption avoidance in tokamaks
Implementing a finite-state off-normal and fault response system for disruption avoidance in tokamaks
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实施有限状态非正常和故障响应系统以避免托卡马克中断
DOI：
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发表时间：
2018
期刊：
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通讯作者：
M. Walker
中科院分区：
文献类型：
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作者：
N. Eidietis;W. Choi;S. Hahn;D. Humphreys;B. Sammuli;M. Walker
提出了一种有限状态异常和故障响应（ONFR）系统，该系统为托卡马克中的全面中断避免和机器保护提供了监控逻辑。鲁棒的事件处理对于ITER和未来的大型托卡马克至关重要，其中等离子体参数将必然接近稳定极限，许多系统将在其工程极限附近运行。事件可以被分类为非正常等离子体事件，例如新古典撕裂模式或垂直位移事件，或故障，例如线圈电源故障。ONFR系统提供了一个强大的事件处理系统的四个关键功能：级联事件的顺序响应，事件恢复，同时处理多个事件和执行器优先级。有限状态逻辑在Matlab®/Stateflow®中实现，以便在自动导出到实时等离子体控制系统代码之前，以易于理解的图形格式进行快速开发和测试。给出了ONFR算法在DIII-D和KSTAR托卡马克上的实验演示。在最复杂的演示中，ONFR算法异步应用“捕获和抑制”电子回旋电流驱动（ECCD）注入方案来抑制致命的2/1新古典撕裂模式，随后在等离子体变得过密时关闭ECCD以保护机器，并使旋转3D场夹带随后的锁定模式以允许安全的斜降，所有这些都在同一放电中，无需用户干预。当多个ONFR状态同时激活并请求相同的致动器（例如中性束注入或回旋管）时，通过对每个激活的ONFR状态的预先分配的优先级值进行排序并将致动器的完全控制给予具有最高优先级的状态来实现致动器优先级排序。这种早期的经验表明，需要额外的研究来开发一种改进的致动器共享协议，以及一种方法，以尽量减少状态的数量和拓扑复杂性的有限状态ONFR系统扩展到一个大的，高度受限的设备，如ITER。
A finite-state off-normal and fault response (ONFR) system is presented that provides the supervisory logic for comprehensive disruption avoidance and machine protection in tokamaks. Robust event handling is critical for ITER and future large tokamaks, where plasma parameters will necessarily approach stability limits and many systems will operate near their engineering limits. Events can be classified as off-normal plasmas events, e.g. neoclassical tearing modes or vertical displacements events, or faults, e.g. coil power supply failures. The ONFR system presented provides four critical features of a robust event handling system: sequential responses to cascading events, event recovery, simultaneous handling of multiple events and actuator prioritization. The finite-state logic is implemented in Matlab®/Stateflow® to allow rapid development and testing in an easily understood graphical format before automated export to the real-time plasma control system code. Experimental demonstrations of the ONFR algorithm on the DIII-D and KSTAR tokamaks are presented. In the most complex demonstration, the ONFR algorithm asynchronously applies ‘catch and subdue’ electron cyclotron current drive (ECCD) injection scheme to suppress a virulent 2/1 neoclassical tearing mode, subsequently shuts down ECCD for machine protection when the plasma becomes over-dense, and enables rotating 3D field entrainment of the ensuing locked mode to allow a safe rampdown, all in the same discharge without user intervention. When multiple ONFR states are active simultaneously and requesting the same actuator (e.g. neutral beam injection or gyrotrons), actuator prioritization is accomplished by sorting the pre-assigned priority values of each active ONFR state and giving complete control of the actuator to the state with highest priority. This early experience makes evident that additional research is required to develop an improved actuator sharing protocol, as well as a methodology to minimize the number and topological complexity of states as the finite-state ONFR system is scaled to a large, highly constrained device like ITER.