Liu Youbo

The study of micro-grid control strategy contained unbalanced load based on sliding-mode variable structure

Unbalanced load increases imbalance and harmonic distortion of system operating voltage, which results in the influence of power quality in micro-grid. Sliding-mode variable structure control is proved to be robust and has plenty of remarkable dynamic response characteristics, so that it could be applied to the micro-grid operation with unbalanced load control. The mathematical model of the system is established, and an appropriate control strategies is designed to aim at achieving a smooth mode-switch among diverse micro-grid operating modes. The experimental results of PSCAD/EMTDC show the feasibility and effectiveness of the proposed approach.

The unit commitment model with wind power connection based on bad operation scenario set

Based on the study of uncertainty and fluctuation of wind power, a novel algorithm including bad operation scenarios set and robust optimization method was proposed in the paper trying to solve probabilistic unit commitment problem of power system which has wind power generation. According to the power system probabilistic dispatch theory, the conservative indicator to evaluate the value of deterioration for bad scenarios set is established, and the variance is added in the optimization target to suppress some individual bad scenarios which may lead to deterioration of the overall optimization results. Furthermore, energy storage system, which has an inherent ability to mitigate active power fluctuation, was taken into account to contribute to the presented unit commitment models. Finally, the numerical example which includes cost, storage capacity, robustness metric and conservatism degree analysis verifies the effectiveness and practicality of the proposed methods.

An identification method for critical low frequency oscillation mode based on inter-area oscillation relevant generator contribution factor

A novel identification method for critical oscillation mode is presented, which makes use of inter-area oscillation and relevant generator contribution factor. Firstly, the relevance between oscillation mode and electric parameters is analyzed. A state equation method is introduced to describe strongly relevant generator sets in multi-machine power system. Secondly, the oscillation assessing index is designed to calculate the risk of the rotor angle instability. And then, oscillation contribution factor, which concerns risk of inter-area oscillation relevant generators, is raised by means of synthesizing parameters like amplitude, damping ratio and attenuation obtained by Prony algorithm. The specified procedures of identifying critical oscillation mode are proposed based on the risk factor. Finally, simulation results of IEEE 10-machine 39-bus system and Sichuan power grid show that: the proposed method is able to identify critical oscillation mode and assess oscillation risk of the strongly relevant generators under different disturbance. Comparing the obtained result with that from energy class of oscillation modes verifies the feasibility and effectiveness of the proposed method.