Extending the reactive compensation range of a direct AC–AC FACTS device for offshore grids

The authors suggest to use hybrid modulation schemes to improve the reactive power compensation capabilities of the direct AC–AC FACTS device composed of a matrix converter and a permanent magnet machine. Because of the intrinsic limitations of the conventional matrix converter modulation schemes, the device has so far displayed a poor reactive power compensation capability when the output power factor is low. Even worse, the direct AC–AC FACTS device could not provide pure reactive power compensation. The paper presents an analysis demonstrating how the hybrid Three-Vector-Scheme extends the reactive compensation range beyond the level that the conventional indirect space vector modulation exhibits. The reactive power compensation capabilities of the FACTS device with both modulations are computed and compared analytically and finally verified by a simulation study.

► A compact FACTS device for offshore applications composed of a matrix converter and a PM machine is suggested.
► The FACTS device cannot provide pure reactive power compensation with conventional modulation schemes.
► The use of hybrid modulation schemes is suggested to increase the reactive power compensation range at low output power factors.
► The reactive compensation range with a hybrid modulation scheme is compared theoretically with the conventional modulation.
► A simulation study is performed and confirms the improvement of reactive power range of the FACTS device.