Power coupling analysis and improved decoupling control for the VSC connected to a weak AC grid

Conventional vector control (VC) is widely used in the voltage source converter (VSC) due to its simplicity and power decoupling ability. However, this paper reveals that the VC may result in strong active and reactive power coupling under weak AC grid conditions. The linearized relationship between the power and dq-axis currents is built. On this basis, the power coupling mechanism is revealed, and the power coupling process is presented. Finally, an improved decoupled power control is accordingly proposed based on the feedforward compensation method. The improved decoupling control method can realize more accurate decoupled active and reactive power regulation. Moreover, its design is simple, and thus is easy to be implemented in practice. The power coupling characteristics analysis and the improved power decoupling control are verified through PSCAD/EMTDC simulations and experiments.