Power systems wide-area voltage stability assessment considering dissimilar load variations and credible contingencies

Bahram SHAKERIGHADI,Saeed AFSHARNIA,Farrokh AMINIFAR

doi:10.1007/s40565-018-0420-6

Bahram SHAKERIGHADI, Saeed AFSHARNIA + Show 1 more

Open Access

https://doi.org/10.1007/s40565-018-0420-6

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Abstract

This paper reveals that the existing techniques have some deficiencies in the proper estimation of voltage stability margin (VSM) when applied to a power system with different load change scenarios. The problem gets worse when credible contingencies occur. This paper proposes a real-time wide-area approach to estimate VSM of power systems with different possible load change scenarios under normal and contingency operating conditions. The new method is based on an artificial neural network (ANN) whose inputs are bus voltage phasors captured by phasor measurement units (PMUs) and rates of change of active power loads. A new input feature is also accommodated to overcome the inability of trained ANN in prediction of VSM under N−1 and N−2 contingencies. With a new algorithm, the number of contingencies is reduced for the effective training of ANN. Robustness of the proposed technique is assured through adding a random noise to input variables. To deal with systems with a limited number of PMUs, a search algorithm is accomplished to identify the optimal placement of PMUs. The proposed method is examined on the IEEE 6-bus and the New England 39-bus test system. Results show that the VSM could be predicted with less than 1% error.

Highlights

Voltage stability is defined as the ability of the power system to maintain steady voltages when it is subjected to perturbations [1]
Typical measures applied for the performance evaluation of artificial neural network (ANN) are residual squared error (R2) and mean square error (MSE) [23, 26]
Where xi is the input parameters of ANN; yi is the value of voltage stability margin (VSM) determined by continuation power flow (CPF) method; yp is the predicted value of VSM estimated by ANN; ym is the mean value of VSM determined by CPF method, and S ANN samples set

Summary

Introduction

Voltage stability is defined as the ability of the power system to maintain steady voltages when it is subjected to perturbations [1]. A power system is designed to operate under various conditions; it is inevitable that complex power systems will experience difficulties in the operation process some of which lead to the voltage collapse. Among several methods developed so far to calculate voltage stability limit [8,9,10,11], continuation power flow (CPF) is one of the most efficient methods. In CPF method, new forms of power flow equations are introduced to overcome the convergence problem of conventional power flow algorithms near the stability limit point [11]. In [12], a modified coupled single-port model was proposed to monitor voltage stability of the system. Results show improvement in monitoring voltage stability in comparison with the conventional CPF method. What is missing in these methods is considering systems different conditions like contingencies

Methods

Results

Conclusion