Control and Transient Operation of Grid-Connected Voltage Source Converter under Unbalanced Voltage Conditions

摘要

The use of distributed energy resources is becoming a serious supplement and alternative to large conventional centralized power stations. Distributed energy resources also offer a possible solution to the environmental demands to reduce CO{sub}2 emissions. Several distributed power sources require solid state power converters to convert the locally generated power into a state where their energy can be supplied to the ac supply network. In most existing systems when an inverter is connected to the bulk supply network, the output voltage is controlled in a similar way to that used for a synchronous machine. In such an arrangement, the output current quality depends on the bulk supply system. If, however, the inverter operates as a current source, the current quality is independent of the voltage quality and can be maintained to a high standard. A common drawback of these systems is that high frequency signals are injected into the power system due to the inverter switching. In order to further suppress switching frequency signals from the output current a filter capacitor must be inserted.