Control of cascaded H-bridges STATCOM based on the power flow management

As smart grid techniques are getting more positive perspective and expected to grow in the future, the STATic synchronous COMpensator (STATCOM) has become one of the most important roles to manage the power flow and regulate the grid voltage. The Modular Multilevel Cascaded Converter (MMCC) based on single star bridge cell (SSBC) is very suitable for STATCOM application at the medium-voltage level in the power system. The dc capacitors voltage balancing control is a critical issue to secure the stable operation of MMCC-SSBC converter. Four different control methods based on power flow analysis have been considered. The performance of each controller is evaluated under steady state or even Low Voltage Ride Through (LVRT) operation. Each controller has its power flow management and its feature. Experimental test results are given to verify these control methods can well regulated the dc bus voltages under the unbalanced grid voltages.