New Energy Modulation Strategy to Reduce the Risk of Misoperation and Overcutting of the Third Line of Defense in the Power Grid

In large-scale multi circuit DC transmission power systems, with the high penetration operation of new energy units, short-term and permanent power shock disturbances occur. The traditional high-frequency third line of defense is based on strategy setting to prevent short-term power misoperation; The second is that multiple typical methods share a set of strategies, resulting in the risk of "excessive cutting off of units or exceeding modulation". In this regard, this article considers the use of new energy units with power modulation capabilities that can be utilized in the actual transmission end power grid to improve the configuration of the third line of defense, namely adding a high-frequency new energy unit modulation wheel (50.2Hz≤f≤50.5Hz) and a low-frequency new energy unit modulation wheel (49.8Hz≤f≤50.0Hz), prioritizing the implementation of "switching with modulation" for new energy units, in order to achieve the goal of minimizing the triggering of traditional third line of defense actions in the system. The proposed method can provide important reference for strengthening the third line of defense for other renewable energy rich external transmission power grids.