Improved parallel operation mode control of parallel connected 12-pulse thyristor dual converter for urban railway power substations

摘要

Parallel-connected 12-pulse thyristor dual converters are connected to the up/down trolley line in urban power substations. When there are high-traffic trains on the up trolley line or the down trolley line, the electric energy, i.e., energy consumed and regenerative energy, increases. During this time, two converters are connected in parallel to supply power or feed energy back to the distribution grid. A parallel operation control scheme has two operating modes depending on the energy flow of trains. When the energy is less than the rated power of a converter, only one converter operates in a single operation mode. If the energy exceeds the rated power of a converter, the other converter is operated in parallel mode operation to distribute the excess energy. During the switching from the single operation mode to the parallel operation mode, overshoots and undershoots occur in the DC trolley voltage and current of each converter due to the large error in the PI controller. To solve these problems, this study proposes improved control method to prevent large overshoots and undershoots. The effectiveness of this proposed control is verified by simulation and experiment based on the comparison of the performance of conventional and proposed control method.