A novel iterative observer approach for real-time harmonic estimation in power distribution networks

In power distribution networks, the realisation of online harmonic state estimation puts forward a higher demand on the algorithm accuracy, stability as well as simplicity. To meet the requirements above, a novel iterative observer based method for harmonic state estimation is proposed. This method guarantees the stability of the harmonic estimation observer when output time delays are considered in the power distribution network.Meanwhile, signals with different frequencies can be estimated iteratively. System harmonics are regarded as the unknown exogenous disturbance, and each harmonic at multiple measurements is extracted and estimated iteratively. To guarantee the overall estimator stability, multiple transmission time delay is addressed in the system modelling for the design of observer gain. The proposed method achieves high estimation accuracy from multiple measurements while maintaining a low computation commitment. Comparing with traditional harmonic state estimation methods, the iterative observer is capable of estimating the unexpected harmonics. The IEEE 13-bus power distribution system built in the real-time digital simulator demonstrates the validity of the proposed method.