A narrow bandwidth detection method for inter-harmonics in Tokamak power supply

Low-frequency harmonics which are close to the fundamental have characteristics of small amplitude and non-stationary state, and contain complex side-lobe inter-harmonics. To ensure the precise and real-time extraction of the whole spectrum band, the compensation measure is difficult. In order to solve this detection problem, a hybrid detection algorithm is proposed based on elliptic digital bandpass filter with boundary characteristics and single-frequency notch filter with optimal Q-factors, which can effectively extract the according band. Single-frequency notch filter has excellent third-order harmonic suppression ability and dynamic robustness characteristics. Elliptic digital bandpass filter can extract harmonics of target frequency band and ensure the phase offset, so as to achieve effective spectrum separation. Simulation with MATLAB is adopted to improve the design process. The validity of the detection algorithm is verified by experiments with digital analysis system based on DSP.