RETRACTED ARTICLE: An improved under frequency load shedding strategy based on dynamic power flow tracing

Shun Li,Qingfen Liao,Dichen Liu,Bingcheng Cen

doi:10.1186/s41601-016-0031-z

Shun Li, Qingfen Liao + Show 2 more

Open Access

https://doi.org/10.1186/s41601-016-0031-z

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Abstract

Under frequency load shedding is an effective approach to maintain or restore the steady-state operation of the power system when frequency accidents occur. An improved under frequency load shedding strategy based on dynamic power flow tracking is proposed. The expression of the kinetic energy theorem in power system is derived and combined with the power flow tracing method to analyze the relation between system energy distribution and its frequency. The power system frequency influencing factors are then constructed and applied to find the reasons of frequency decline and to quantify the contributions of the mechanical power of the generators, the load power and the transmission losses for the frequency deviation. Finally, considering a variety of unbalanced power scenarios in the system, the modified load shedding strategy is designed. Based on the results of dynamic power flow tracing, the strategy can choose the suitable load node to control, and the defined load frequency contribution indicator is utilized to determine the load shedding amount which each control object undertakes. The proposed methodology is verified by the fault scenarios when the generator sets mistakenly cut off and the trip of important tie-lines in the IEEE 39-bus system. Compared with the conventional strategies, the proposed strategy is more selective, can reduce the blackout range, and improve the effect of stable frequency recovery.

Highlights

L Abstract C Under frequency load shedding is an effective approach to maintain or restore the steady-state operation of the I power system when frequency accidents occur
This paper proposes a methodology to analyze the fre
The paper derives the expression of the kinetic energy theorem in power systems, which is combined with the power flow tracing method to analyze the relationship between dynamic distribution of energy and frequency variation in a power system

Summary

T Methods

E For a power system with n generators, the motion equation [13] for the rotor of generator i is given as. 1/2Miωi*2 is defined as the kinetic energy of generator i and (4) is the expression of the kinetic energy theorem in power systems It indicates that the kinetic energy difference of one generator equals the difference of the work of its mechanical power and electromagnetic power during this period. C Besides, it can calculate the contribution quota of I the input power on line i-j to its downstream load k and power transmission loss, shown in (7) and (8) respectively as RT Pij;Lk. D method takes the steady state power flow into account. E obtained between the load power and generator power through the dynamic power flow tracing method in each moment This is because that the input and output power. T of the load node is always equal at any time

C The analysis of the frequency influencing factor

So the load at bus k needed to shed can be calculated as

E Results and Discussions T Digital simulation

E Funding