Tidal currents are being recognized as a resource for sustainable electrical power generation. However, the main challenge for marine current energy development is to minimize the operation costs and maintenance operations in the marine harsh environment. These worries are justified by the incident high rates on offshore wind turbine systems. Marine current turbines are characterized by a very difficult access for regular or emergency maintenance operations. This is why the development of fault tolerant system is a key feature. This paper deals with the use of a PM multiphase marine current turbine generator. With this kind of system, it is possible to maintain the power production even if an electrical fault appears in the power converter. This system is associated with an optimal strategy of torque/speed control using a high-order sliding mode control which is particularly adapted to the healthy or faulty operation mode.