Abstract
A de-loaded real power control strategy is proposed to decrease the real power output and increase the reactive power output of a grid-connected offshore wind farm in order to improve the voltage profile when the wind farm is subject to a grid fault. A simplified linear model of the wind farm is first derived and a fixed-gain proportional-integral (PI) real power controller is designed based on the pole-zero cancellation method. To improve the dynamic voltage response when the system is subject to a major disturbance such as a three-phase fault in the grid, a self-tuning controller based on particle swarm optimization (PSO) is proposed to adapt the PI controller gains based on the on-line measured system variables. Digital simulations using MATLAB/SIMULINK were performed on an offshore wind farm connected to the power grid in central Taiwan in order to validate the effectiveness of the proposed PSO controller. It is concluded from the simulation results that a better dynamic voltage response can be achieved by the proposed PSO self-tuning controller than the fixed-gain controller when the grid is subject to a three-phase fault. In addition, low voltage ride through (LVRT) requirements of the local utility can be met by the wind farm with the proposed power controller.
Highlights
According to the nuclear-free energy policy in Taiwan, more than 20% of the electrical energy will come from renewable energy by 2025
The aforementioned works are effective in protecting the Doubly fed induction generators (DFIGs) and the associated power electronic devices under grid fault conditions, additional hardware components are required in order to implement these fault ride through techniques
A self-tuning controller based on particle swarm optimization (PSO) [26,27,28] is presented to adapt the real power controller gains K p and Ki in real-time
Summary
According to the nuclear-free energy policy in Taiwan, more than 20% of the electrical energy will come from renewable energy by 2025. A novel de-loaded power control algorithm without additional hardware components is proposed to improve the terminal voltage and to increase the reactive power output of a DFIG subject to grid faults. Based on the simulation results, it is concluded that a better voltage profile can be achieved by the proposed PSO self-tuning power controller than the fixed-gain PI controller. It is observed from the simulation results that the wind farm with the proposed controller meets the low voltage ride through (LVRT) requirements of the local utility in Taiwan
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