A Simple and Effective Open-Circuit-Fault Diagnosis Method for Grid-Tied Power Convertersu-A New Technique Based on Tellegens Theorem

Grid-tied power converters are widely adopted in renewable energy integration systems. Reliable operation of such power converters is highly desirable, which relies on effective fault diagnosis and ride-through techniques. In this work, we propose a new open-circuit fault diagnosis method for grid-tied power converters based on Tellegen's theorem, which is fast in fault detection and accurate in faulty component location. We first developed a "quasi-power" concept to define the relationship between current and voltage magnitudes for the underlying power converter. The value of the afore-developed quasi-power in this proposal depends solely on the connection state (i.e., the switch position and status) of a power converter, resulting in its good features of robustness to parameter variations and immunity to operation changes. Thereafter, we propose a fault diagnosis method based on the quasi-power of a converter, which is able to identify any faulty component among all the semiconductor switches (i.e., the insulated gate bipolar translators (IGBTs) and freewheeling diodes) at a time-scale of only one sampling period. As a case study, the proposed technique is incorporated into a well-known model predictive control (MPC) framework of a grid-tied two-level (2L) power converter and tested at a lab-constructed test bench. Experimental results confirm its effectiveness.