Guo Yarong

Modeling and simulation research of large-scale AC/DC hybrid power grid based on ADPSS

With the continuous increasing load and construction of UHV, A plurality of EHV / UHV AC and DC transmission lines centralize in the load center. In order to analyze the interactive effects of AC or DC system when fault occurs, a hybrid simulation model on electromechanical and electromagnetic transient process of AC and DC is established for regional power grid. The electromagnetic transient model covers the EHV / UHV AC and DC transmission lines, EHV / UHV transformer and lots of generators. Various faults are simulated in four network partitions, including all kinds of AC and DC transmission faults. On the basis of simulation, the characteristics and interactive effects of AC and DC system is studied. Research results suggest that for load center with both DC and AC, AC system faults will cause multiple HVDC commutation failure, thereby affecting the performance of AC relay protection. For the power grid closely connected, the DC system blocking will not cause any problem on system stability.

The delay optimization of circuit breaker failure protection based on the CT current tail truncation algorithm

Circuit breaker failure protection (CBFP) is a widely used back-up protection in electrical power system. To avoid maloperation, the CBFP needs a long delay to confirm the status of the circuit breaker, which means the cut off time will be long, sometimes too long to keep the stability of the power system. Therefore, it is very important to propose an optimized method to calculate the CBFP delay time for improving the stability of the system. A CT current tail truncation algorithm based on a CT tailing current-short circuit current criterion plane has been shown in this paper, which can truncate CT tailing current quickly and thereby shorten the delay of CBFP. Without special configuration of P level CT, this algorithm ensures the reliability and rapidity of CBFP, significantly reduces the risk of system operation, and has good economic benefits.