基于自适应控制参数整定的虚拟同步发电机控制策略

Control strategy of virtual synchronous generators based on adaptive control parameter setting

以新能源为主体的新型电力系统呈现“低惯量,低阻尼”特性,而虚拟同步发电机(VSG)控制策略可以通过模拟同步发电机机械运动方程和电磁特性,使得分布式逆变电源具备同步发电机的惯性与阻尼特性来增强系统的稳定性,但是也会牺牲一定的动态调节性能。提出了一种基于自适应控制参数整定的虚拟同步发电机控制策略,通过建立的虚拟同步发电机小信号模型,分析转动惯量与阻尼系数对暂态过程中系统频率与输出功率的影响;通过同步发电机功角和频率振荡曲线分析自适应转动惯量和角速度变化率以及角速度偏移量、自适应阻尼系数和角速度偏移量之间的关联性,得到不同区间内转动惯量与阻尼系数的选定原则,基于此设计了自适应转动惯量与阻尼系数的计算式以及触发阈值,进一步,加入基于调频功率上下限的自适应下垂系数,提出了一种基于自适应控制参数整定的VSG控制策略;通过在Matlab/Simulink搭建的离网情况下VSG仿真模型中进行仿真与分析,验证了所提控制策略能减小频率的偏移量,提高系统的频率稳定性和动态调节能力。

The new power system with new energy as the main body presents the characteristics of"low inertia and low damping".Since the virtual synchronous generator(VSG)control strategy can simulate the mechanical motion equation and electromagnetic characteristics of the synchronous generator,the strategy can enhance the stability of the power system by making the distributed inverters possess the inertia and damping characteristics of the synchronous generator.However,the strategy will compromise their dynamic regulation performances.Thus,a VSG control strategy based on adaptive control parameter setting is proposed.Firstly,the effects of inertia moment and damping coefficient on system frequency and output in transient process are analyzed by establishing a small signal model of VSGs.Then,the correlation between the adaptive moment of inertia,angular velocity variation ratio and angular velocity offset,and the correlation between the adaptive damping coefficient and the angular velocity offset are analyzed by the power angle-frequency oscillation curve of a synchronous generator.The selection principle for the inertia moment and damping coefficient in different intervals is obtained,and their calculation formula and the trigger thresholds are designed.Furthermore,by adding adaptive droop coefficient considering the upper and lower limits of frequency modulation power,a control strategy of VSGs based on adaptive control parameter setting is proposed.Finally,the simulation analysis on the off-grid VSG model is built by Matlab/Simulink,and the simulation results verify that the proposed control strategy can reduce the frequency offset,and improve the frequency stability and dynamic regulation ability of the system.