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This paper presents an open-loop voltage control approach for the offshore voltage source converter (VSC) of a HVDC transmission system, which forms the AC offshore grid with a defined voltage vector. The common multi-loop approach including current controls is avoided, which generates challenges for the dynamic performance of the voltage control regarding overcurrent limitation and disturbance rejection capabilities. Furthermore, the offshore voltage control is used within the context of PSCADTM/EMTDCTM simulation studies on AC meshed offshore grids, where two offshore wind power plants (OWPPs) operating at different HVDC transmission systems are interconnected. The simulations demonstrate how the active and reactive power flow between both interconnected offshore grids for can be controlled for different control objectives. [ABSTRACT FROM AUTHOR]

This paper presents an open-loop voltage control approach for the offshore voltage source converter (VSC) of a HVDC transmission system, which forms the AC offshore grid with a defined voltage vector. The common multi-loop approach including current controls is avoided, which generates challenges for the dynamic performance of the voltage control regarding overcurrent limitation and disturbance rejection capabilities. Furthermore, the offshore voltage control is used within the context of PSCADTM/EMTDCTM simulation studies on AC meshed offshore grids, where two offshore wind power plants (OWPPs) operating at different HVDC transmission systems are interconnected. The simulations demonstrate how the active and reactive power flow between both interconnected offshore grids for can be controlled for different control objectives. [ABSTRACT FROM AUTHOR]

HVDC- transmission is the medium of choice to connect offshore wind power plants to the onshore grid when longer distances have to be overcome. To generate cost savings and hence to push further extension of offshore wind power plants uncontrolled diode rectifier HVDC-systems, instead of VSC-HVDC converters, may be used in the future. Besides the need for a grid forming capability of the wind turbine converters, also the unidirectional power flow of uncontrolled diode rectifiers evokes a challenge during calm wind situations. Hence, solutions for supplying auxiliary power to the offshore wind farm during a lack of wind have to be found. This paper presents one possible option of the auxiliary power supply where a sample offshore wind power plant is connected to the onshore grid via additional umbilical AC cable. Investigations, carried out by simulation using PSCAD™/EMTDC™, show how the wind power plants either can be operated with a fixed reference frame (FixReF) control in the normal case or with conventional PLL based control during calm wind situations. During the transition between both cases, synchronization processes have to be done when connecting and disconnecting the umbilical AC cable. [ABSTRACT FROM AUTHOR]

HVDC- transmission is the medium of choice to connect offshore wind power plants to the onshore grid when longer distances have to be overcome. To generate cost savings and hence to push further extension of offshore wind power plants uncontrolled diode rectifier HVDC-systems, instead of VSC-HVDC converters, may be used in the future. Besides the need for a grid forming capability of the wind turbine converters, also the unidirectional power flow of uncontrolled diode rectifiers evokes a challenge during calm wind situations. Hence, solutions for supplying auxiliary power to the offshore wind farm during a lack of wind have to be found. This paper presents one possible option of the auxiliary power supply where a sample offshore wind power plant is connected to the onshore grid via additional umbilical AC cable. Investigations, carried out by simulation using PSCAD?/EMTDC?, show how the wind power plants either can be operated with a fixed reference frame (FixReF) control in the normal case or with conventional PLL based control during calm wind situations. During the transition between both cases, synchronization processes have to be done when connecting and disconnecting the umbilical AC cable. [ABSTRACT FROM AUTHOR]