Reduction of the voltage distortion with a converter employed as shunt harmonic impedance

The amount of non-linear and unbalanced loads (such as adjustable speed drives and PC´s) connected to the electric power system is steadily growing. The power quality i.e. the reliability of the energy supply and the quality of the voltage waveform, may be severely degraded and may cause many unfavourable effects on both the power system and the connected loads. Especially in the case of resonances, severe voltage distortion may result. Although complete compensation is only possible using true active filters, resistive shunt harmonic impedances (SHI) have been shown to provide a considerable reduction of the harmonic propagation. These impedances can be implemented using active power electronic devices and are controlled to synthesize a resistive load. Benefits: no need to measure the polluting load current, effective for all harmonics and different resonance conditions, simple control strategy, and may be implemented as a secondary control function of an active power supply. In this paper, a practical implementation of a resistive SHI is proposed. A new control strategy for a boost power factor correction (PFC) converter has been implemented in order to achieve a programmable resistive input impedance for harmonics, independent of the input impedance for the fundamental component. Furthermore, the potential to damp a resonance in a power distribution system is demonstrated using an experimental setup