LINEARISATION OF NON-LINEAR LOADS BY PHASE DEPENDENT FREQUENCY COUPLING ADMITTANCE MATRICES

Abstract- Harmonic modelling of small, low power non-linear devices is traditionally ignored due to their complexity, decentralised nature and insignificant current draw on the power system. However with widespread use of such power electronic based non-linear loads, the combined effect is having considerable impact on system harmonic voltage levels. This paper develops frequency coupling admittance matrices for non-linear loads, incorporating phase dependency for accurate linearised models in the harmonic domain. The proposed technique determines the equivalent Norton admittance matrix by sequentially applying small harmonic voltage distortions to the load terminals. Since the actual non-linear device is tested no knowledge of load circuit design or operation is required. Computational efficiency is gained when the matrices are used to simulate large numbers of non-linear loads distributed throughout electrical power systems