Adaptive Bus-Impedance-Damping Control of Multi-Converter System Applying Bidirectional Converters

Modern dc-power-distribution systems utilizing energy storages are often dependent on the operation of bidirectional power-electronics converters. Such distribution systems typically consist of several feedback-controlled converters prone to experience stability issues due to cross-effects among the different converters. Studies have presented adaptive control-based techniques to prevent such stability issues, but most studies have not fully considered their implementation on a bidirectional converter. The system dynamics may vary significantly depending on the operating point and particularly the direction of the bidirectional power flow. Therefore, specific care should be taken in the design of the adaptive stabilizing control to guarantee that the system’s regular operation is not impeded when the stabilization is implemented on a bidirectional converter. This paper proposes a procedure to implement an adaptive stabilizing control method on a bidirectional converter with minimal changes to the regular controller. We add an adaptive resonance term to the bidirectional converter’s voltage controller that enhances stability and damping around the identified resonance frequency without impeding the converter’s regular operation. The resonance term is adjusted periodically based on online impedance measurements and the chosen design criteria. As a result, the controller can dampen resonances and prevent adverse impedance-based interaction. Experimental measurements based on a multi-converter setup demonstrate the effectiveness of the proposed methods.