Abstract
In a power system with wind farms, the point of common coupling (PCC) usually suffers from voltage instability under large wind speed variations and the load impact. Using the internal converter of a doubly fed induction generator (DFIG)-based wind turbine to provide voltage support auxiliary service is an effective scheme to suppress the voltage fluctuation at PCC. To satisfy the reactive power demand of the connected grid, an active voltage coordinate control strategy with the hybrid energy storage system of the wind farm is proposed. The dynamic reactive power balance model is established to show the interaction between the reactive power limitation of the wind farm and the reactive power compensation demand of the grid. This indicates the initial conditions of the active voltage coordinate control strategy. According to the critical operating point and the operation state of the DFIG, the active and reactive power coordinate control strategy composed of active ω-β coordinate control and active β control is proposed to enhance the reactive power support capability and stabilize the grid voltage. To compensate the active power shortage, an auxiliary control strategy based on the hybrid energy storage system is introduced. The simulation results show that the proposed strategy can suppress the voltage fluctuation effectively and make full use of primary energy.
Highlights
The doubly fed induction generator (DFIG)-based wind turbine, as the main model in the current wind power industry [1], has been widely used because of the excellent control performance of the active and reactive power [2,3]
Long-distance and large-capacity high voltage transmission technology is generally adopted for wind farms which are located at the ends of the grid with an insufficient support capacity of the voltage [6,7]
The random fluctuation of wind speed and the impact load may lead to the voltage change at the point of common coupling (PCC) of the wind farm, the decrease in power quality, and the increase in equipment operation risk, which seriously threaten the voltage stability of the grid [8]
Summary
The doubly fed induction generator (DFIG)-based wind turbine, as the main model in the current wind power industry [1], has been widely used because of the excellent control performance of the active and reactive power [2,3]. Considering the requirements of real-time reactive power compensation, using the internal converter of DFIG to provide voltage support auxiliary service is an effective scheme to reduce the adverse effects of wind speed variation and load impact. The voltage problem of the wind farm caused by the rapid fluctuation of wind speed and the impact load cannot be solved by voltage control without considering the reactive power demand of the connected grid. In the case of wind speed variation and load impact, it is necessary to propose a wind farm voltage control strategy considering voltage stability and energy utilization. In [30], a distributed consensus control method for output power of DFIG and energy storage was proposed, which could realize energy management under different wind speeds. The rotor speed can be further adjusted by modifying the reference value of DFIG output active power
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