Publish in OALib Journal
APC: Only $99
During the transient period of
large-disturbance of the received power grid, the power features of the
inverter are of great important for the security and stability of the system.
The research before is defective in that the constant control mode assumption
and the rough HVDC simulation model. The paper establishes the PSCAD/EMTDC
model for Yun-Guang EHVDC system, and analysis the transient real power and the
reactive power of the inverter. With the analysis of logic for control mode,
the author also introduces the physical processes of the peak of the reactive
power. At last, the paper puts forward several strategies for suppressing the
peak of the dynamic reactive power and real power recovery acceleration.
A new inductive motors load
equivalence algorithm based on coherence is proposed in this paper. In order to
partite motors load rapidly and accurately, fuzzy c-means clustering along with
particle swarm optimization (PSO-FCM) algorithm is proposed to identify
coherent motors base on its physical essence of fuzziness. The merits of PSO
algorithm are independent to initial value and convergent to optimum value
rapidly, and the validity function is constructed to assess clustering
validity. The test on IEEE 39-Bus System is presented to evaluate the
effectiveness of the new algorithm, the membership matrix definite not only
coherence group of motors but also correlation value of coherence between
motors. The algorithm can be used to partite motor load based on coherency in
dynamic equivalence with power system operating on different modes.
HVDC technology has been widely used in modern power system. On one
hand, HVDC has the advantages of economy, high efficiency and strong controllability.
While on the other hand, it makes the dynamic characteristics of the power
system becoming more and more complex. That puts forward a new challenge to
system stability and raises new questions for power system simulation. This
paper focuses on the interaction between AC and DC systems, especially the
problem of commutation failure caused by AC system fault. Based on the data of
China Southern Power Grid, this paper calculates the fault regions that may
cause commutation failure and calculates the system critical clearance time
under different load models, analyzes the impacts of different load models on
commutation failure and the stability of AC/DC hybrid system.
The paper firstly interprets
the differences between electromechanical transients program BPA and
electromagnetic transients program EMTDC in the field of principle, model and
algorithm. Then the authors carry out the simulation based on single-machine
infinite-bus system and draw some conclusions. The time consumption of the
simulation using EMTDC is much longer than the simulation using BPA under the
same length of time. The results of BPA are close to those of EMTDC under
steady conditions. The fundamental frequency component of the EMTDC results
seems closer to the BPA results than its original value, but they still away
from completely consistent. In this simulation of single-machine infinite-bus
system, the transient stability results of BPA and EMTDC are close, but the
results of BPA are apt to be more conservative. All the conclusions above have
a certain reference value to both hybrid simulation and comprehensive analysis
method in the study of the AC/DC digital simulation of large power grid.