无交流电容的构网型换流器电压电流比例控制及故障限流

通过引入电压电流比例关系，构建了适用于高压构网型换流器的无电容矢量电压控制，可与传统内环电流控制组成构网型换流器级联控制架构，保留正序电流限幅和负序电流抑制能力，防止换流器在电网故障时发生过流闭锁和损坏。与传统外环电压控制不同，该电压电流比例控制不依赖于交流侧并联容性滤波器的电气关系构建，适用于无交流电容的高压构网型换流器的外环电压控制。通过选取特定的交流电压频率指令值，构网型换流器可实现恒电压运行或虚拟同步机运行。时域仿真结果表明，所提高压构网型换流器控制在电网故障时可自动实现换流器的负序电流抑制和故障穿越功能，避免换流器过流闭锁及损坏，并在故障清除后恢复正常运行。

Voltage and current proportional control for AC capacitor-less grid-forming converter with fault current limitation

By introducing the voltage and current proportional relationship, a capacitor-less vector voltage control is proposed for the high-voltage grid-forming converter. A cascaded control architecture is composed of the proposed outer-loop voltage control and conventional inner-loop current control. The positive-current limitation and negative-sequence current suppression capabilities are retained to prevent the converter from over-current blocking and damage during grid faults. Unlike the conventional outer-loop voltage control, the proposed voltage-current proportional control is developed irrespective of the AC-side shunt filter capacitor, which is suitable for outer-loop voltage control of the high-voltage grid-forming converter. By selecting the specific AC voltage frequency reference, the grid-forming converter can realize either constant voltage operation or virtual synchronous generator(VSG) operation. The time-domain simulative results show that the negative-sequence current suppression and fault ride-through capabilities are automatically realized by the proposed converter control during grid faults. Moreover, the grid-forming converter is prevented from over-current blocking and damage, and can be restored to the normal operation condition when the grid fault is cleared.