Reactive power optimisation design and fault ride through of MMC‐PLUS

Abstract

To integrate bulk wind power, a modular multilevel converter (MMC)‐PLUS composed of the series connection of line commutated converter (LCC) and MMC is investigated. The system combines the advantages of LCC and MMC, such as high power, high voltage, self‐commutating and direct current (DC) fault blocking capability. However, due to the coupled control of active power and reactive power, much reactive power should be compensated during the operation of LCC. The study makes a detailed analysis and optimisation of reactive power compensation devices taking into account the PQ operation curve of MMC and making full use of the capacity of MMC. In addition, further studies the control strategy of DC fault isolation and system restart under DC fault. The effectiveness of the reactive power configuration and DC fault strategy is verified by simulations in PSCAD/EMTDC.