Compensation of low frequency harmonics caused by parallel operating AC converters

Consumer electronics such as TV, PCs, single-phase power converters for motor drives, etc. cause low frequency mains disturbances as a consequence of their uncontrolled rectifier-end DC link capacitor. For this type of VSI power converter, line harmonic reduction can be obtained by installing an inductance under consideration of the line impedance. This reduces the neutral's current and improves power quality. A new and successful method uses half-controlled rectifiers in every second device in order to obtain line harmonic compensation. An estimation of the load limitation of mains transformers burdened by VSI power converters is explained. Next, this estimation is discussed together with line harmonic compensation between single-phase and three-phase power converters and is compared to controlled rectifiers with an inductive load or CSI power converters.