Method for Calculating Electromagnetic Compatibility Indicators of Nonlinear Consumers of Common DC Bus with PWM

Abstract

Based on the general method of differential equations algebraization, the method for the assessment of DC-circuit THD-analogues for voltage and current is offered. This technique is intended for the mono-bus DC system, i.e. a common DC bus, feeding some nonlinear consumers, and it can be simply generalized to the case of any number of consumers. The expression of the DC-circuit n-order integrated signal harmonics factor as a function of the known similar AC-circuit factor is shown. Furthermore, the coefficients of participation of certain individual nonlinear consumers in the overall distortion of power quality (ripples), namely to the total signal harmonic distortion (the individual relative share contributions of nonlinear loads to the AC component), are considered. The authors perform experimental verification of the proposed calculation method on the PSIM computer model, including the feeding pulse-width power DC-DC converter with an output LC-filter and two current sources of different types. The obtained formulas for electromagnetic compatibility indicators allow predicting the quality of power supply at the design stage for the power supply system with known analytical descriptions of any form of currents at non-linear consumers.