An improved harmonic contribution estimation using nonlinear optimization techniques

Multiple distributed harmonic sources, such as inverter-interfaced distributed generation (DG), in distribution systems have posed new challenges in identifying the cause of harmonic voltages or currents observed at a specific location. This paper proposes a new method to estimate harmonic contribution using nonlinear optimization techniques. First, definitions are provided and the problems are described. Then, existing solutions found in the literature, with focus on the latest method (i.e. linear method), and the details of the proposed nonlinear method are presented. Finally, the linear and the nonlinear methods are simulated and evaluated using a sample 27.6 kV distribution feeder with two large PV generators in CYME and MATLAB software. Results show that while the linear method may be accurate in specific applications, the nonlinear method provides significantly higher accuracy in a broader range of applications.