DC bus voltage harmonics reduction

Abstract

In one aspect, in general, the invention features a control system configured for use with a three-phase PWM converter. The control system receives an input signal from a three-phase power supply and provides an output signal at a DC link. A voltage-separating module generates on the basis of the input signal a positive sequence voltage component and a negative sequence voltage component in a rotating reference frame. A reference current computation module uses at least the positive sequence voltage component and the negative sequence voltage component to compute a first reference current and a second reference current. A current regulating module uses at least the first reference current and the second reference current to generate a command signal. The command signal is provided to a driving circuit of the three-phase PWM converter for generating a regulated DC bus voltage at the DC link.

Description

Cross References to Related Applications This application claims the benefit of US Application Serial No. 12 / 057,856, filed March 28, 2008, the contents of which are hereby incorporated in their entirety. Background technique The present invention relates to a power conversion system for generating a regulated direct current (DC) bus voltage from an alternating current (AC) power source. Electricity generated by the power plant is transmitted to consumers through the utility grid in the form of three-phase AC power. However, AC power is not always suitable for an end use and sometimes needs to be converted to a usable form (eg, DC) before being connected to a load. In this case, use an AC / DC converter. Generally, an AC / DC converter receives alternating current at its input and outputs direct current at its DC link. To produce a satisfactory output, the AC / DC converter is often operated with a controller that regulates the shape and amplitude of the DC bus voltage to a de...

AI Technical Summary

Problems solved by technology

Negative sequence components cause even harmonics in the DC link voltage and odd harmonics in the converter current, which can significantly deteriorate the quality of the DC power supplied to the load

In extreme conditions, this may even cause the system to trip if the maximum DC bus voltage is exceeded

In large power conversion systems, these problems can become worse as the number of converters connected to a common AC chain increases

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