Direct power control of grid connected voltage source converters

This paper proposes a new direct power control (DPC) strategy for grid connected voltage source converters (VSC). Similar to an electrical machine, source and converter flux are defined as the integration of the source and converter voltage respectively. Based on the defined flux, the proposed DPC scheme directly calculates the required converter voltage to eliminate the active and reactive power errors within each fixed time period. Thus, no extra power or current control loops are required, thereby simplifying the system design and improving transient performance. Constant converter switching frequency is achieved using space vector modulation which eases the design of the power converter and the AC harmonic filter. Simulation results for a 2 MW VSC system are provided to demonstrate the effectiveness and robustness of the proposed control strategy during variations of active and reactive power and AC voltage dip.