One application of high–voltage dc (HVdc) systems is the connection of remotely located offshore wind power plants (WPPs). In these systems, the offshore WPP grid and the synchronous main grid operate in decoupled mode, and the onshore HVdc converter fulfills the grid code requirements of the main grid. Thus, the offshore grid can be operated independently during normal conditions by the offshore HVdc converter and the connected wind turbines. In general, it is well known that optimized reactive power allocation might lower the component loading and power losses. This paper aims to propose and assess a reactive power allocation optimization within HVdc–connected WPPs. For these systems, the offshore converter operates the adjoining grid by imposing frequency and voltage. The reference voltage magnitude is used as additional control variable for the optimization algorithm. The loss function incorporates both the collection grid and the converter losses. The use of the proposed strategy results in an effective reduction of losses compared to conventional reactive power dispatch strategies alongside with improvements of the voltage profile. A case study for a 500 MW–sized WPP demonstrates an additional annual energy production of 6819 MWh or an economical benefit of 886 k€yr-1 when using the proposed strategy.Postprint (author's final draft

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© 2017 John Wiley & Sons, Ltd. Offshore wind power plants (WPPs) built near each other but far from shore usually connect to the main grid by a common high-voltage DC (HVDC) transmission system. In the resulting decoupled offshore grid, the wind turbine converters and the high-voltage DC voltage-source converter share the ability to inject or absorb reactive power. The overall reactive power control dispatch influences the power flows in the grid and hence the associated power losses. This paper evaluates the respective power losses in HVDC-connected WPP clusters when applying 5 different reactive power control strategies. The case study is made for a 1.2-GW-rated cluster comprising 3 WPP and is implemented in a combined load flow and converter loss model. A large set of feasible operating points for the system is analyzed for each strategy. The results show that a selection of simulations with equal wind speeds is sufficient for the annual energy production comparison. It is found that the continuous operation of the WPPs with unity power factor has a superior performance with low communication requirements compared with the other conventional strategies. The optimization-based strategy, which is developed in this article, allows a further reduction of losses mainly because of the higher offshore grid voltage level imposed by the high-voltage DC voltage-source converter. Reactive power control in HVDC-connected WPP clusters change significantly the overall power losses of the system, which depend rather on the total sum of the injected active power than on the variance of wind speeds inside the cluster.Postprint (author's final draft