Multi-Objective Optimal Control Approach for Static Voltage Stability of Power System Considering Interval Uncertainty of the Wind Farm Output

Yuerong Yang,Mingbo Liu,Shunjiang Lin,Qiong Wang,Yuquan Xie

doi:10.1109/access.2020.3002931

Yuerong Yang, Mingbo Liu + Show 3 more

Open Access

https://doi.org/10.1109/access.2020.3002931

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Abstract

The static voltage stability margin (SVSM) of a power system considering the uncertain fluctuation range of wind farm (WF) output can be described as an interval value called the SVSM interval. A multi-objective optimal control model for SVS of a power system considering the interval uncertainty of WF output is proposed. The objective functions of the model are to increase the central value and reduce the fluctuation range of the SVSM interval, and the decision variables are the active power output and terminal voltage of generators and the switching capacity of shunt capacitors. Thus, it is a multi-layer optimization model. A parametric approximation (PA) method is used to obtain the approximate functional relationship between the optimal objective function values and the decision variables of the inner-layer and mid-layer optimization models and convert the optimization model into a single-layer bi-objective optimization model. A method for obtaining the continuous Pareto frontier of the bi-objective optimization model is proposed based on the normalized normal constraint and PA methods, and the compromise optimal solution calculated from the continuous Pareto frontier is used as the optimal control scheme. Two methods for improving the calculation efficiency of the PA method are also proposed. Finally, results from experimentation on the IEEE 39-bus system and an actual provincial power grid demonstrate the effectiveness of the proposed method.

Highlights

Affected by the uncertain fluctuation of wind speed, the active-power output of wind farms (WFs) has large uncertainty and volatility, which brings great challenges to the secure operation of power systems [1], [2]
The errors between the static voltage stability margin (SVSM) calculated by the parametric approximation (PA) equation and the SVSM calculated by the inner-layer optimization model are calculated
By solving two single-objective optimization models with objective functions (1) and (2) after PA, the optimal control schemes (PG0, UGref, Qc) and the lower and upper bounds of the SVSM interval corresponding to the optimal solutions are obtained

Summary

Introduction

Affected by the uncertain fluctuation of wind speed, the active-power output of wind farms (WFs) has large uncertainty and volatility, which brings great challenges to the secure operation of power systems [1], [2]. When the fluctuation range of WF output is large, the fluctuation range of SVSM may be resulted large. If the values of the SVSM range are small, the lower bound of the SVSM range is very small, and the system is prone to voltage collapse with the increasing of load. When considering the optimal SVS control of a power system with uncertain fluctuation of WF output, it is necessary to increase the central value and reduce the radius of the SVSM interval at the same time, which is a bi-objective optimization problem. Since the calculation of the upper and lower bounds of the SVSM interval is a bi-layer optimization model [5], the optimal SVS control model of a power system considering the uncertain fluctuation of WF output is a bi-objective multi-layer optimization model. How to effectively solve this model is a challenging problem

Methods

Results

Conclusion