A scheme on adaption detection of large-capacity wind turbines to the power grid

It was presented that a design scheme on adaption detection device for large-capacity wind turbines to the power grid, based on back-to-back voltage source converter parallel system. The voltage-current dual closed loop control strategy was used in converter modules connecting to power grid, to maintain the voltage of DC capacitor at a predetermined value, and make the detection device run with the unity power factor. In converters connected to a wind turbine, it was designed that master-slave control strategy including feedward control segment. Voltage control was used in the master module to maintain the output voltage of the detection device at the expected value, and simulate the interconnected voltage of wind turbines. Besides, voltage disturbances, such as frequency disturbances, voltage fluctuation disturbances, negative sequence voltage disturbances, etc., were also simulated in the master module. In slave modules, current control was used to ensure the module output current can match its own capacity, and meet the bidirectional power transmission requirements further. According to design requirements, using actual parameters of AC / DC and DC / AC converters made by the Infineon Technologies, parameters of key components in the detection device were designed and calculated in detail. Simulation of designed adaptive detection device was carried out by using PSCAD/EMTDC, in accordance with the above proposed control strategy and designed parameters of components. The device can work in 35kV rated voltage; output voltage frequency disturbance from 45Hz to 60Hz; output negative sequence voltage disturbance with variable amplitude and phase, imbalance less than 10%; output voltage fluctuation disturbances, amplitude fluctuations between -10% and +10%, frequency from 0.5Hz to 25Hz. The output voltage imbalance of the detection device ranges from 0 to 4%, and the total harmonic distortion is between 0 and 5%.