Receiving-end Power Grid Black Start Technology and Coordinated Restoration Strategy Based on Wind-storage Combined System

When faults occur in the receiving-end power grid, the sending-end power supply is required to have black-start capability. At present, the existing black-start power sources in China are mainly thermal power plants and hydropower plants. With a high proportion of wind power enormously connected to the main grid, wind turbines are required to have a certain black-start capability. However, due to the uncertainty and volatility of wind energy, it is difficult for wind turbines to participate in black start alone. In order to make wind turbines have better black start ability to participate in power grid restoration, this paper proposed a three-stage coordinated recovery strategy for the receiving-end power grid based on the combined wind-storage system for doubly-fed wind farms. In the initial stage, the AC frequency and voltage were established through the energy storage device so that the wind turbine can smoothly connected to the main grid. Then, in the middle stage, the control mode of the energy storage device was switched and a virtual synchronous control was designed on the rotor side of the wind turbine to provide support of frequency and voltage for the system, and some generator sets and loads can recover. After that, in the later stage, an additional robust controller based on H2/H∞ was designed on the energy storage side, which can suppress the low-frequency oscillation when multiple units connected to the grid, so as to realize the stable recovery of the receiving-end power grid. Finally, a wind-storage combined system model was built based on PSCAD/EMTDC and the black start and restoration of power grid restoration was simulated. The simulation results show that the proposed joint startup of both wind turbine and energy storage can realize the smooth grid connection of wind turbine; In the grid connection process of plant load and generator, switching energy storage control mode of wind turbine can maintain the voltage and frequency of in the stable range; Moreover, in the stage of recovery and later operation of receiving power grid, the designed robust controller designed has a good effect on suppressing low-frequency oscillation; Compared with the conventional control modals, the virtual synchronization control adopted in the process of system startup and recovery has a stronger ability to support the system; Thus, the effectiveness and feasibility of the proposed coordinated restoration strategy of wind and energy storage system participating in the black start of the receiving power grid are fully verified. © 2023 Editorial Department of Journal of Sichuan University. All rights reserved.