Improved control strategy of virtual synchronous generator considering unbalanced load

The unbalanced load connected to the microgrid leads to the loss of symmetry in the three-phase voltage of the virtual synchronous generator, which reduces the voltage quality and operational stability of the microgrid. In order to solve the problem of three-phase voltage imbalance in virtual synchronous generators caused by load imbalance, an improved virtual synchronous generator control strategy considering voltage compensation for unbalanced loads is proposed. Using a second-order generalized integrator to decompose the three-phase voltage into positive sequence, negative sequence, and zero sequence. By introducing the positive sequence voltage into the excitation voltage regulation loop, the excitation voltage is corrected, reducing the component of the second harmonic generated by the negative sequence component of the unbalanced load and suppressing the low-frequency fluctuations caused by asymmetric loads. To eliminate the three-phase voltage asymmetry caused by load imbalance, negative sequence voltage is introduced into the voltage current control loop. When the load is unbalanced, - θ is used for α β transformation to correct the voltage offset of the voltage current control loop and reduce the voltage imbalance caused by unbalanced loads. Simulation and experimental results have confirmed that the proposed improvement strategy solves the problems of three-phase voltage imbalance caused by unbalanced loads and low-frequency harmonics caused by negative sequence components in virtual synchronous generators, improving the power supply quality and operational stability of microgrids.