Comparative Design and Analysis of Dc-Link-Voltage Controllers for Grid-Connected Voltage-Source Converter

Electric power conversion is used when loads require a voltage with a different magnitude and frequency than the supplying grid. In most cases the power conversion is made in two steps: one rectifier and one converter. The design and operation of the rectifier is of great importance for the interaction with the utility grid. By using a Voltage-Source Converter with a controllable DC-link voltage, a higher power quality can be obtained than using a simple diode rectifier. In this paper, two designs of a DC-link-voltage controller are analyzed and tested. The parameter sensitivity, frequency response and load-disturbance rejection are investigated and compared. The response of the voltage controllers are also improved by utilizing feed forward. Both the measured DC- load current and a calculated DC-load current, obtained with an observer, are used. The performance of the controllers is evaluated through simulations and laboratory tests.