Estimating the Harmonic Impacts of Multiple Harmonic-Producing Loads Considering Network Impedance Variations

The existing methods for evaluating harmonic impacts of multiple harmonic-producing loads (HLs) usually assume that all the network impedances are constant in the concerned whole-time interval. While considering the actual situations in power grids, the network impedances may have continuous or sudden variations due to grid operation changes, such as power line maintenance, filter switching, and capacitor switching, which causes the unreliable estimation of harmonic impacts by the existing methods. In view of this shortcoming, a novel multi-point model considering the variations of multiple network impedances is proposed. Furthermore, two weight matrices are formulated to fit the abrupt changes in network impedances. Based on the model and the matrices, the continuous and sudden variations of multiple network impedances can be tracked simultaneously according to the proposed minimum weighted variation constraint. Finally, more realistic and accurate harmonic impacts can be obtained. The performed simulation and experiment have demonstrated the validity of this method.