A two-level hierarchical discrete-device control method for power networks with integrated wind farms

Fengda Xu,Boming Zhang,Qinglai Guo,Hongbin Sun,Lin Jia

doi:10.1007/s40565-018-0417-1

Abstract

Power systems depend on discrete devices, such as shunt capacitors/reactors and on-load tap changers, for their long-term reliability. In transmission systems that contain large wind farms, we must take into account the uncertainties in wind power generation when deciding when to operate these devices. In this paper, we describe a method to schedule the operation of these devices over the course of the following day. These schedules are designed to minimize wind-power generation curtailment, bus voltage violations, and dynamic reactive-power deviations, even under the worst possible conditions. Daily voltage-control decisions are initiated every 15 min using a dynamic optimization algorithm that predicts the state of the system over the next 4-hour period. For this, forecasts updated in real-time are employed, because they are more precise than forecasts for the day ahead. Day-ahead schedules are calculated using a two-stage robust mixed-integer optimization algorithm. The proposed control strategies were tested on a Chinese power network with wind power sources; the control performance was also validated numerically.

Highlights

Hierarchical architectures are used to solve problems with different time scales in power-frequency and varvoltage control systems
We could improve the control performance using information updated in real time and a rolling optimization procedure; these approaches are costly and take much longer to evaluate individually in within-day control scenarios
We have presented a two-level hierarchical discrete-device control (THDDC) method

Summary

Introduction

Hierarchical architectures are used to solve problems with different time scales in power-frequency and varvoltage control systems. The schedules are updated approximately every 15 min according to a tertiary frequency control (TFC) algorithm that solves real-time ED problems for ultra-short-term load forecasts. As multi-timescale coupling is considered insignificant in var-voltage control, longer time scales, such as those relevant to scheduling an entire day, have been considered in only a few studies. This rarely causes problems because, in general, these systems have an abundance of reactive power, and the state of the system is not dominated by time-coupled behaviors

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