Tolerance band controller for a three-level four-quadrant converter including DC link balancing

Tolerance band or hysteresis control is usually applied only for simple converters with one switching element The paper shows how to generalize the approach for more complex converter systems like a three-level four-quadrant converter and to benefit from the high effective loop gain of the control approach. State graphs are used for the design of the controller. For the three-level converter, the state graph is able to manage both tasks of current control and DC link balancing. The controller can be realized using a FPGA. A processor or a microcontroller is obsolete.