An Analysis of Variable-Speed Wind Turbine Power-Control Methods with Fluctuating Wind Speed

Yun-Su Kim,Il-Yop Chung,Seung-Il Moon

doi:10.3390/en6073323

Abstract

Variable-speed wind turbines (VSWTs) typically use a maximum power-point tracking (MPPT) method to optimize wind-energy acquisition. MPPT can be implemented by regulating the rotor speed or by adjusting the active power. The former, termed speed-control mode (SCM), employs a speed controller to regulate the rotor, while the latter, termed power-control mode (PCM), uses an active power controller to optimize the power. They are fundamentally equivalent; however, since they use a different controller at the outer control loop of the machine-side converter (MSC) controller, the time dependence of the control system differs depending on whether SCM or PCM is used. We have compared and analyzed the power quality and the power coefficient when these two different control modes were used in fluctuating wind speeds through computer simulations. The contrast between the two methods was larger when the wind-speed fluctuations were greater. Furthermore, we found that SCM was preferable to PCM in terms of the power coefficient, but PCM was superior in terms of power quality and system stability.

Highlights

Renewable energy sources have attracted growing research interest in recent years, wind power, whose commercial installations in about 80 countries at the end of 2011 totaled about 240 GW [1].Its average cumulative growth rates over 15 years amount to about 28%
This means that if PCM is used as the active power-control mode of a Variable-speed wind turbines (VSWTs), an average active power loss of 0.453% will occur relative to the optimal value, while speed-control mode (SCM) maintains the optimal output power
We concluded that SCM is preferable to PCM in terms of the power coefficient and yields slightly higher power output, whereas PCM is superior in terms of power quality and system stability, yielding a more stable electricity signal

Summary

Introduction

Renewable energy sources have attracted growing research interest in recent years, wind power, whose commercial installations in about 80 countries at the end of 2011 totaled about 240 GW [1].Its average cumulative growth rates over 15 years amount to about 28%. Renewable energy sources have attracted growing research interest in recent years, wind power, whose commercial installations in about 80 countries at the end of 2011 totaled about 240 GW [1]. In the early 1990s, fixed-speed wind turbines (FSWTs) were widely installed; FSWTs have drawbacks, including uncontrollable reactive power, excessive mechanical stress, and limited power-quality control. The variable-speed wind turbine (VSWT), which uses a power converter and is more controllable than a FSWT, has become the dominant type of wind turbine due to the increasingly more strict technical requirements of the grid operation codes [2]. VSWTs typically employ a maximum power-point tracking (MPPT) method to acquire the maximum amount of energy from the wind. The active power fluctuates as the wind speed varies, which may lead to power quality and the power system stability issues

Methods

Results

Discussion

Conclusion