Abstract:It is an effective solution to utilize the energy storage unit (ESU) configured inside each wind turbine of the wind farm to absorb the unbalanced power during the DC fault of the wind power integration through a bipolar MMC-HVDC. However, the existing literature only equates the wind farm to a single wind generator (WG) and does not consider the residual capacity difference of each ESU. It is easy to cause the ESU with small residual capacity to be overloaded, while the ESU with large residual capacity still has a large energy storage capacity that is not utilized, resulting in power imbalance during the fault. To address the above problems, this paper proposes a coordinated control strategy for DC fault ride-through based on optimization control of ESUs inside WGs. In this strategy, the variance of state of charge (SOC) is used as an index to quantitatively describe the difference of residual capacity of ESUs, and the maximum decrease rate of SOC variance is taken as the objective function. The residual unbalanced power after the conversion of non-fault pole converter station is optimally allocated to the ESUs within each WG, so as to reduce the difference of residual capacity while ensuring the power balance of the system during the fault period. A model is developed and carried out on the PSCAD/EMTDC simulation platform to compare the proposed power optimization allocation scheme with the traditional average allocation scheme. The results show that the optimal allocation scheme fully developed the power consumption ability of the energy storage system and improves the DC fault ride-through ability of the system.