Three-Leg Voltage Source Converter Integrated with T-connected Transformer as Three-phase Four-wire Distribution Static Compensator for Power Quality Improvement

In this article, a new topology of a distribution static compensator is proposed for power quality improvement in a three-phase four-wire distribution system. A three-leg voltage source converter based distribution static compensator is integrated with a T-connected transformer for the compensation of reactive power for voltage regulation or for power factor correction, along with load balancing, elimination of harmonics currents, and neutral current compensation at the point of common coupling. The T-connected transformer is used for providing a path to the zero-sequence current in a three-phase four-wire distribution system. In order to reduce the voltage rating of the voltage source converter, the T-connected transformer is designed to have secondary windings for integrating the distribution static compensator. This transformer connection provides the selection of an "off-the-shelf" voltage source converter for this application, and it also provides isolation for the voltage source converter system. The kVA rating of the transformers in the T-connected configuration is comparable to that of a similar zig-zag transformer, and there are only two single-phase transformers required in the T-connected configuration. This reduces the complexity and also cost of the distribution static compensator system. The performance of the proposed distribution static compensator system is validated through simulations using MATLAB software with its Simulink and Power System Blockset toolboxes.