Over-frequency Generator Tripping Control of Sending-end System Considering Transient Instability Generating Units

With the high penetration of renewable energy sources participating in the power grid, frequency stability control becomes a significant problem restricting the security and stability operation of a multi-HVDC sending-end system with a small load and large power. HVDC monopolar blocking or bipolar blocking leads to increasing the sending-end system frequency. Over-frequency generator tripping is an important control measure to restraining the sending-end system frequency increasing. This paper proposes the configuration principles of over-frequency generator tripping considering the transient instability generating units, the frequency protection of wind turbines, and the variation of the line power flow. Then, the configuration process and the method of the over-frequency generator tripping scheme is proposed according to the configuration principles and the field operation experience. An example of a provincial power grid is used to verify the effectiveness and the adaptability of the proposed over-frequency generators tripping scheme under different operation modes and HVDC blocking failures.