Online Rapid Mimo Frequency Scanning Using Binary Complementary Codes

Small-signal stability assessment and monitoring in converter-dominated grids can be performed using frequencyresponse (FR) data that can be acquired online with minimal perturbation. This paper applies complementary binary codes as excitations for simultaneous multi-input multi-output (MIMO) frequency scanning. These codes are also referred to as Golay- Rudin-Shapiro (GRS) sequences, after their inventors. We exploit their complementary autocorrelation and composite spectral flatness to derive a correlation- and cross-spectral FR estimator, and include a guard interval to capture the impulse-response tail during admittance estimation. Hadamard modulation preserves complementarity and yields orthogonal channels for MIMO identification. A unified simulation framework benchmarks GRS against the more common pseudorandom binary sequences and multisines under identical constraints, such as injection time, signal energy and realistic noise levels. Accuracy and efficiency are compared using the log-integrated normalized mean square error (NMSE) and computation time. The admittance estimation is demonstrated for three systems including different passive networks with background harmonics and a power converter. The proposed GRS approach consistently shows comparable or better metrics with less injected energy. Therefore, these features, combined with its DSP-friendly implementation and short injection time, make GRS a practical and efficient solution for online FR acquisition and system monitoring.