Research on the control strategy of cascaded H-bridge SVG under grid fault

In order to deal with the voltage drop caused by grid fault, this paper proposes the control strategy of cascaded H-bridge SVG under balanced and unbalanced voltage drop, respectively. In condition of balanced voltage drop, this paper proposes a control strategy which can rapidly compensate reactive power to the grid so that the voltage can be supported in a certain extent. In condition of unbalanced voltage drop, a grid current balancing control strategy which adopts positive and negative sequence decoupling control to realize the control of reactive power and negative sequence component is proposed. In addition, a dc voltage balancing control strategy which adopts zero sequence voltage injection method is proposed to keep the dc voltage balanced. The simulations verify the efficiency of the proposed control strategies.