Robust state-estimation procedure using a least trimmed squares pre-processor

Based on real-time measurements, Static State Estimation serves as the foundation for monitoring and controlling the power grid. The popular weighted least squares with largest normalized residual removed, gives satisfactory performance when dealing with single or multiple uncorrelated bad data. However, when the bad data are correlated or bounded, this estimator has poor performance in detecting bad data, which leads to erroneous deleting of normal measurements. Similar to the Least Trimmed Squares(LTS) method of robust statistics, this paper considers a state estimator built on random sampling. However, different from previous robust estimators, which stop after estimation, we regard the LTS estimator as a pre-processor to detect bad data. A subsequent post-processor is employed to eliminate bad data and re-estimate the state. The new method has been tested on the IEEE standard power networks with random bad data insertions, showing improved performance over other proposed estimators.