A robust control and design of generator-side converter for a multi-megawatt hydraulic energy conversion system

This paper focus on an optimal control of a multi pole permanent magnet synchronous generator MP-PMSG direct driven by multi-megawatt hydraulic turbine system connected to the grid. The control strategy is applied to extract the full power output from the hydraulic turbine through a DC/DC boost converter connected to the generator by an uncontrolled three phase rectifier. This control method consists of two cascaded loops, a fast inner loop of DC inductor current, gives the instantaneous duty ratio d to the boost converter switch. The second outer speed loop controls the generator speed to balance well the power flow into the grid. Concerning the control strategy of the DC/AC converter grid side, the three levels NPC inverter controls the DC link voltage and injected active/reactive powers by the (d, q)-axis currents respectively. The reactive power generated by the entire installation is adjusted at zero so that unity power factor is maintained. Simulation results show that the suggested control strategy method and system modeling operate satisfactorily.