Focusing on the typical scenarios of renewable energy HVDC outbound systems，this study clarifies the spatiotemporal distribution characteristics of transient overvoltage at the sending end caused by commutation failure.To overcome the limitations of conventional grid-following static var generator （SVG） in voltage support capability during transients，a grid-forming energy-storage SVG （GFM-ESVG） model with active grid voltage/frequency support capability is constructed by coupling energy storage units to the DC capacitor side of cascaded H-bridge submodules.Simultaneously，a coordinated fault ride-through strategy integrating current limiting and transient voltage support is proposed to maintain its transient voltage source characteristics.Qualitative comparative analysis further reveals the differences in transient overvoltage suppression capabilities between GFM-ESVG and traditional SVG.Finally，PSCAD/EMTDC simulations demonstrate that GFM-ESVG not only effectively suppresses transient overvoltage at the sending end induced by commutation failure but also significantly enhances the transient power transmission capability of wind turbines while partially mitigating system frequency oscillations.