Reactive power management in an offshore AC network having multiple voltage source converters

Many offshore wind power plants are being developed every year at North and Baltic Sea. From the prospective of environment and integrated European power, combined power transmission from several offshore wind power plants using VSC-HVDC transmission system to different onshore grids are suitable instead of connecting each wind power plants individually. Offshore AC hub is beneficial for the wind power plants that are far from shore but close to each other within the vicinity of 20 km. This paper presents a method of controlling reactive power flow in the offshore AC grid to minimize the power losses and voltage deviation. In the proposed scheme, offshore grid frequency and voltage are controlled through more than one converter. Using frequency and voltage droop schemes, the active and reactive power sharing is achieved among converters. Furthermore, the optimization algorithm is developed to acquire the set points for the wind power plants and VSC-HVDC droop gains for the optimum operation of the network.