This article proposes a power-smoothing scheme for a variable-speed wind turbine generator (WTG) that can maintain the frequency within a narrow range under normal operations. The proposed scheme uses an additional control loop based on the frequency deviation that operates in conjunction with maximum power point tracking (MPPT). To improve the energy-absorbing capability in the overfrequency section (OFS) and energy-releasing capability in the underfrequency section (UFS), the scheme suggests separate control gains, which are determined based on the ratio of the output of the additional loop to that of the MPPT loop. The ratio in the OFS is set to decrease with respect to the rotor speed whereas the ratio in the UFS is set to increase with respect to the rotor speed. The simulation results demonstrate that the proposed scheme can significantly lessen the WTG output power fluctuations by adjusting the control gains of the UFS and the OFS even though the WTG output power is severely fluctuating, thereby mitigating the frequency fluctuations. The scheme effectively uses the heavy rotating masses of a WTG as an energy storage system for enhancing the power grid flexibility in terms of frequency, particularly in high penetration levels of variable renewable energy.

中文翻译：

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基于二值控制增益的变速风力发电机的功率平滑

本文提出了一种用于变速风力涡轮发电机（WTG）的功率平滑方案，该方案可以在正常运行下将频率保持在狭窄范围内。所提出的方案使用基于频率偏差的附加控制回路，该控制回路与最大功率点跟踪（MPPT）结合使用。为了提高超频部分（OFS）的能量吸收能力和欠频部分（UFS）的能量释放能力，该方案建议使用单独的控制增益，该增益取决于附加回路的输出与该回路的输出之比。 MPPT循环的 OFS中的比率设置为相对于转子速度减小，而UFS中的比率设置为相对于转子速度增大。仿真结果表明，即使WTG输出功率剧烈波动，该方案仍可以通过调整UFS和OFS的控制增益来显着减小WTG输出功率波动，从而减轻频率波动。该方案有效地利用了WTG的沉重旋转质量作为能量存储系统，以提高电网在频率方面的灵活性，特别是在可变可再生能源的高渗透率方面。