The Research Of Control Strategy Of Three-phase Voltage Source Rectifier Under Unbalanced Power Grid

The situation of unbalanced power grid happens frequently when the rectifier is in service. Under this circumstance, using traditional control strategy will produce harmonic wave which makes the wave distorted,equipments may be burned out. Meanwhile DC-side voltage contains harmonic component, this will affect the performance of the three-phase VSR(voltage-source-rectifier).Unbalanced power gird makes the three-phase system unsymmetrical, the traditional power theory can not be used to calculate power component effectively of the three-phase VSR.The paper put forward instantaneous power theory based on dq0 coordinate system, it analysed the meaning of each power component and the influence of zero sequence component to instantaneous reactive power.The paper analysed the reason of how AC-side and DC-side harmonic wave be produced, it focused on two control strategies which is AC-side current balanced control strategy and eliminating DC-side second harmonic control strategy aimed at different applications.The control solutions need to extract the positive and negative component of power grid, double-frequency trap filter and positive,negative filter are been introduced. The paper compared and tested the two filters.The paper system designed the three-phase VSR under unbalanced power grid, it proposed improved method of AC-side inductance design.In the design of current loop and voltage loop, internal control method is used in order to improve the anti-interference property of the system.Finally, the three-phase VSR has been tested, the simulation waves verify the effectiveness of the control strategy and the correctness of the design parameters.