Active Converter Injection-Based Protection for a Photovoltaic DC Distribution System

Due to the complex structure of flexible dc distribution systems with distributed photovoltaic power, single-ended measurement based protection cannot work well. The dc line-to-line faults are also difficult to locate due to a short time span with fault characteristics that is affected by various converter structures and control algorithms. To resolve these issues, a new fault detection and location method based on active converter injection is presented. The proposed method modifies the converter to become a frequency-controllable injection source by actively utilizing the coordinated control between local protection and the converters, which can build a clear protection boundary. Moreover, this method can locate the faulted area accurately by selecting the appropriate injected harmonic frequency, which is affected by the outlet capacitance of the dc/dc converter and the cable-distributed capacitance. Compared with current dc protection techniques, this method does not require additional injection equipment and high data sampling frequency. Hardware tests and simulation results are carried out, illustrating that the proposed mechanism is effective to achieve both control and protection through the controllability of power electronics.

Automated summary

Due to the complex structure of flexible dc distribution systems with distributed photovoltaic power, the existing protection methods are not effective. This paper proposes a fault detection and location method based on active converter injection, which utilizes coordinated control between local protection and converters. The method can accurately locate the faulted area by selecting appropriate injected harmonic frequency.