Application of harmonic state estimation to a distribution system

Abstract

The harmonic levels in a distribution system are becoming more important as many new power electronic based devices are being deployed. In order to manage the harmonic levels, it is important to know them. Direct measurement of harmonics at all locations is too costly, yet obtaining a system-wide view is important. Harmonic State Estimation (HSE) is a cost-effective alternative to direct monitoring of all the harmonics. To date, it has been applied mostly to transmission systems but in this paper, it is applied to a model of an actual distribution system. An actual distribution feeder, which is typical of many other feeders in the system is modelled in Open Distribution System Simulator (OpenDSS) and harmonic penetration study performed. Voltage and current harmonics at selected locations are then used as the measurements. Using these measurements and electrical network data, HSE is performed based on a robust mathematical technique, Singular Value Decomposition (SVD). The estimated results are compared with those obtained from harmonic penetration simulations performed in OpenDSS to assess the accuracy of the estimation. Locations and number of measurements that can give maximum observability with reasonable accuracy are also identified.