Dual converter active filter and balance compensation on electric railway systems using the open delta transformer connection

This work presents a filtering and unbalance compensation scheme for electric traction systems with open delta transformers using dual converters. The proposed method uses an active filter controlled with the instantaneous active and reactive power, to reduce the harmonic current distortion and the negative sequence present in the railway system under unbalanced operation in steady state. The dual converter controls the voltage level in each sub converter. The modulation method used is commonly known from literature and the option of clamping one of the sub converters is exploited to minimize the switching. The use of dual-converters in active filters and balance compensation reduces the voltage level across the power devices. The dual converter is implemented using conventional two level three phase converters. The method has been experimentally validated, and the results prove the proposed controller advantages.