基 于 直 流 电 压 同 步 的 构 网 型 直 驱 风 电 机 组 暂 态 控 制 方 法

The power system with high proportion of renewable energy and high proportion of power electric equipment presents the characteristics of weak inertia and low short-circuit ratio, and the grid-following renewable energy cannot independently provide the transient frequency and voltage support required by the system. The adoption of grid-forming control is regarded as the key to solving this problem. Grid-forming converters manifest voltage source characteristics. However, due to the limited overcurrent capability of power devices, controlling transient currents during faults poses a challenge. Full-power direct-drive wind turbine units can employ DC voltage synchronization to achieve grid-forming, and an additional current controller is applied to suppress transient currents for fault ride-through. Nevertheless, this method still experiences impact currents during fault occurrence and recovery moments, risking the loss of transient support capability due to protection control strategy for converters. In response to this issue, by analyzing the short-circuit current generation mechanism and power response mechanism of grid-forming full-power wind turbine units using DC voltage synchronization during grid faults, an improved transient control method is proposed. The method employs a voltage vector limiter to achieve rapid matching of internal potential with fault voltage to limit the steady-state component of short-circuit current. Additionally, a nonlinear virtual resistor is introduced to achieve fast control of internal potential compensation to suppress the transient component of short-circuit current. Furthermore, during faults, the synchronization loop and reactive power loop are blocked to maintain the voltage source characteristics of the unit and achieve autonomous power response. The effectiveness and feasibility of the proposed method are verified through simulation and experimental validation.