Cable Overcurrent Control Strategy of Stand-alone Brushless Doubly-Fed Power Generation System

The brushless doubly-fed induction generator (BDFIG) promises advantages such as high reliability and low maintenance costs, and thus is widely used for power generation. In stand-alone applications, the loads are connected to the BDFIG system with long AC cables. In overload conditions, the overcurrent will cause excessive conduction losses and thermal problem on the cable, and thus, the cable overcurrent control is required. However, the cable current consists of the power-winding (PW) current and the load-side-converter (LSC) current, which are varied with rotor speed and impacted by slip power respectively, and make the overcurrent control challenging. This paper proposes a novel strategy to realize the constant cable overcurrent control. Based on the analyzed current relations among cable, control winding (CW), PW and LSC, the CW-current limitation is dynamically regulated according to the rotor speed and the state of LSC, so that the constant cable overcurrent control can be realized directly without extra sensor and close-loop for the cable current. Experiments are also implemented to verify the validity of the proposed strategy.