High ratio penetration of power electronic devices have added many inter-harmonics to the power system. These dynamically changing inter-harmonics raise new security issues, such as sub-synchronous oscillations (SSO) and frequency stability control, which propose new requirements to power system monitoring devices. In this paper, a fast synchronized measurement method with wide frequency bandwidth is proposed by using super-resolution characteristics of spatial spectrum estimation, and a kurtosis based method for estimating the number of signal frequency components is proposed, the stability under low SNR conditions of the method is improved, and the fast and high-precision measurement of the wide frequency bandwidth signal is realized. And then, a prototype of wide frequency bandwidth measurement is developed. The results of simulation test, laboratory device test and field data test verify the validity of the proposed method.

kurtosis,short time window,spatial spectrum estimation,wide frequency bandwidth measurement,synchronized measurement