Experimental Validation of a Unified and Linear State Estimation Method for Hybrid AC/DC Microgrids

This paper presents the experimental validation of a linear recursive state estimation (SE) process for hybrid AC/DC microgrids proposed in the authors' previous work. The SE uses a unified and linear measurement model that relies on the use of synchronized AC and DC measurements along with the complex modulation index of voltage source converters (VSCs). The validation is performed on the hybrid AC/DC microgrid available at the EPFL. The hybrid network consists of 18 AC nodes, 8 DC nodes and 4 VSCs interfacing the AC and DC parts of the grid at different nodes. The experimental validation of the measurement model is based on the classical noise model verification via the measurement residuals. It is shown that the measurement residuals of the AC system, DC system and VSC model are zero-biased with a standard deviation well below the three-sigma threshold of the expected noise distribution. An estimation of the prediction error covariance is also implemented and analyzed to automatically adopt the accuracy of the SE during dynamic and steady-state conditions. Furthermore, the time latency of each section in the SE process is analysed to validate its applicability in critical real-time applications.