Grid-Connected Control Strategy of VSG under Complex Grid Voltage Conditions

Under complex grid conditions, the voltage usually has an imbalance, low order harmonics, and a small of DC bias. When contains harmonics amount bias component, inverter's output current cannot meet connection requirements, there is three-phase imbalance in control strategy common VSG under unbalanced voltage. A theoretical analysis non-ideal power grids carried out, operating conditions proposed. Firstly, third-order generalized integrator (TOGI) used to eliminate influence component An improved delay signal cancellation (DSC) method proposed balance fluctuation based on positive negative sequence separation, It also eliminates harmonic command current. Then, quasi proportional resonant controller (QPR) cascaded PI suppress further so that content grid-connected can requirements achieve balance. Finally, verified by simulation objectives balance, active power, reactive constant.