二次调频能使电力系统在一次调频过程中始终满足频率稳定的要求。采用虚拟同步发电机VSG控制策略的并网逆变器在离网运行时仅具备一次调频特性,若VSG的输出频率超出安全工作区间时将会对微电网的稳定运行产生影响,因此,需在有功控制环加入固定积分系数来实现频率无差控制的二次调频,但传统二次调频存在恢复时间与频率振荡的固有矛盾。提出一种根据暂态导数极性分段优化的改进VSG二次调频策略,该策略基于频率恢复特性,将频率恢复过程划分为2个阶段,并分别配置不同的积分系数,使得整个频率恢复时间缩短,且避免了频率的振荡,并给出了所提方法关键参数的设定依据。最后通过仿真与基于HIL的半实物平台验证了所提策略的可靠性。
Abstract
Secondary frequency regulation can ensure that the power system always meets the requirements of frequency stability during the primary frequency regulation process. The grid-connected inverter using the virtual synchronous generator （VSG） control strategy only has the characteristics of primary frequency modulation when operating off the grid. If the output frequency of the VSG exceeds the safe operating range, the stable operation of the microgrid will be affected. Therefore, it is necessary to add a fixed integral coefficient to the active control loop to realize the secondary frequency modulation of frequency deviation-free control. However, traditional secondary frequency modulation has an inherent contradiction between recovery time and frequency oscillation. An improved VSG secondary frequency modulation strategy based on transient derivative polarity subsection optimization is proposed in this paper. This strategy divides the frequency recovery process into two stages based on the response characteristics of frequency recovery, and configures different integration coefficients for the two stages, so that the entire frequency recovery process has a faster recovery time and avoids frequency oscillations. It also provides a basis for setting the key parameters of the proposed method. Finally, the correctness and effectiveness of the improved control strategy proposed in this paper are verified by simulation and the hardware-in-the-loop platform based on HIL.
关键词
并网逆变器 /
二次调频 /
虚拟同步发电机 /
分段优化
Key words
grid-connected inverter /
secondary frequency modulation /
virtual synchronous generator /
segment optimization
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基金
国家自然科学基金（52077191; 62003297）
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