Optimal configuration method of capacitor isolation device against DC bias on improved niche GA algorithm

The capacitance isolation device is a kind of effective suppression of DC bias in transformers caused by HVDC monopolar operation. However, according to the actual operation of the system, the capacitive isolation device at the neutral point of a transformer will probably cause more serious DC bias in other adjacent transformers while inhibiting its internal bias current at the same time. Since autotransformers are applied widely in the high-voltage network, in this paper, we considered the structural characteristics of it and introduced the concept of effective bias current to describe the influence of magnetic bias current on the transformer more accurately. Then, the authors choose the bias current at any substations in the target grid less than the limit value as the constraint condition. Aiming at the minimum number of installed capacitors, the genetic algorithm based on improved niche is used to solve the optimal configuration problem. Taking the Ethiopia power grid as a test case, the authors work out the optimal quantity and installed location of capacitance isolation devices which satisfy the constraint condition. Compared with the traditional method, the cost is greatly reduced.