Active filter for multi-phase ac power system

Abstract

An active filter (300) generates multi-phase compensating current in an AC power supply system (10) that supplies a load (200). The filter (300) includes a compensating current output device (34) outputting multi-phase compensating current to an AC power line (50); and a controller (310) for controlling the compensating current output (340) such that the multi-phase compensating current compensates for current harmonics and power factor on said AC power line (50). The controller (310) estimates current harmonics and power factor compensating values as a function of multi-phase power measurements.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to power factor and current harmonics compensation in a multi-phase AC power system. 2. Related Art Electrical power distributions systems that deliver AC power are known to be affected by characteristics of the associated load(s). More specifically, non-linear loads, such as motor drives, generate substantial current harmonics in the power supply lines. Furthermore, such loads may cause power factor displacement and imbalance between phases of the current and voltage supplied in the power system. It has been recognized that mitigating the effects of load-generated harmonics can improve the performance of the power system. To this end, one conventional technique for improving quality of the supplied multi-phase power has been to install passive filters inside the loads to suppress the current harmonics being generated by the loads themselves. Although the use of passive filters can effectively remove s...

AI Technical Summary

Benefits of technology

In one aspect, the present invention provides an active filter that suppresses current harmonics and improves power factor in a variable or constant frequency multi-phase power system. In another aspect, the present invention provides a controller of an active filter that generates a multi-phase compensating current that compensates the power factor and current harmonics in a variable or constant frequency multi-phase power system.

Problems solved by technology

Furthermore, such loads may cause power factor displacement and imbalance between phases of the current and voltage supplied in the power system.

Although the use of passive filters can effectively remove some of the major harmonics, such filters are source impedance dependant.

Also, this technique does not address other power quality issues caused by the load(s).

More specifically, the use of passive filters does not compensate for power factor displacement or maintain balance between phases of the supply voltage and supply current.

Thus, conventional techniques offer only an incomplete solution for power quality in a multi-phase AC power system.

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