不平衡电网下自同步虚拟同步机拓展功率控制策略研究

Extended Power Control Strategy of Self-synchronized Virtual Synchronous Generator Under Unbalanced Power Grid

虚拟同步机控制策略因其能为电网提供惯性和频率支撑的特性被广泛应用于新能源发电系统并网接口,但其在不平衡电网下的运行能力不足。为提高虚拟同步机在不平衡电网下的自同步并网能力和输出功率的电能质量,文章提出一种不平衡电网下基于拓展功率的自同步虚拟同步机控制策略。首先研究拓展功率和传统功率的关系,并提出一种适用于虚拟同步机控制的拓展功率理论。然后分析将拓展功率理论应用于自同步虚拟同步机策略的可行性,并研究一种拓展功率谐振控制方法,使虚拟同步机在不平衡电网中可以实现对传统和拓展功率的精确控制。在此基础上,提出一种基于拓展功率的自同步虚拟同步机控制策略,通过选择不同的功率组合作为控制变量,可实现不平衡电网下虚拟同步机的精准自同步并网和3种不同的功率控制模式。实验结果验证了所提控制策略的有效性。

Virtual synchronous generator(VSG)control strategy is widely used in the grid connection interface of new energy power generation system because of its inertial and frequency support characteristics for the power grid,but its operating capacity under unbalanced power grid is insufficient.In order to improve the self-synchronization capacity of the VSG and the quality of the output power under an unbalanced power grid,this paper proposes an extended power theory based self-synchronized VSG strategy.First,the relationship between the extended and the traditional powers are studied,and an extended power theory for VSG control is proposed.Then the feasibility of applying the extended power theory to the self-synchronized VSG strategy is analyzed,and an extend power resonance control method is studied for VSG to achieve precise control of both the extended and the traditional powers in the unbalanced power grid.Based on the analyses above,an extended power theory based self-synchronized VSG strategy is proposed,which can achieve precise self-synchronization and three different power-control modes by selecting different combinations of powers as the control variables.Experimental results verify the effectiveness of the proposed control strategy.