In recent years, the reporting of synchronous resonance events (sub-synchronous and super-synchronous) has become more common due to the rapid penetration of power grids with renewable power sources. The sub-synchronous events have been frequently observed for networks with wind farms connected downstream of the grid by-line compensators. However, new phenomena of multi-mode synchronous resonance have emerged due to the inverter-based resources (IBRs) interpolating range of frequencies in the fundamental frequency. Such events are significantly important to detect for stable operation of the system as the event results in escalating power oscillations in the network that can lead to the disconnection of generation sources and may damage the generators. Detection of such events using PMUs possess significant challenges in terms of their limited reporting rate, spectral leakage and picket fence effect, which intuitively report false amplitude and frequency of the modes of interest while detecting multimode resonance. Therefore, this work leverages novel synchro-waveforms to analyze the complex power sinusoids and initiate early detection of non-fundamental frequency intrusions in the signals leading to unstable operation and oscillation in the network. The proposed method is validated using the IEEE test benchmark and results intimate the potential real-time grid applications
