A voltage balancing control based on average power flow management for the delta-connected cascaded H-bridges converter

The electric arc furnaces (EAFs) are the major disturbances in the medium-voltage level of power system for the low frequency voltage variations, which lead to incandescent lamp flickering. In order to alleviate these voltage variations, the modular multilevel cascaded converter with the topology of single-delta bridge-cell (MMCC-SDBC) is used to the medium-voltage level flicker compensator application. The voltage balancing control of MMCC-SDBC is a fundamental issue to maintain the system operation. This paper presents a voltage balancing control by zero sequence current injection based on the average power flow management. Besides, the proposed method has ability to operate at unbalanced grid voltages since both the positive and negative sequence voltages are considered. The laboratory test results show the verifications of proposed method, which are tested at a down-scaled 220V and 1kVA converter.