多光伏发电参与电网频率调节的动态协调机理

大规模光伏发电并网挤占了具有转动惯量的同步发电机组容量空间,致使电力系统面临惯量减小与调频能力不足的问题,迫切需要光伏发电主动参与电网频率调节。文中以多光伏发电单元并联系统为研究对象,通过改进各逆变器的控制策略,实现其虚拟惯量控制。基于光伏发电不平衡有功功率激励—相位输出响应关系,分析控制增益系数、时间常数以及锁相环控制带宽对其惯量特性的影响。同时,以两机并联系统为例,分析电网频率动态过程中各光伏发电单元的协调运行机制,揭示电网频率动态过程中不平衡功率的分配机理,并推广至多机并联系统。最后,基于时域仿真算例验证了理论分析的有效性、控制策略的可行性。

Dynamic Coordination Mechanism of Grid Frequency Regulation with Multiple Photovoltaic Generation Units

Large-scale grid-connected photovoltaic(PV)generation occupies the capacity space of synchronous generators with rotational inertia, which causes the power system facing the problem of insufficient inertia and frequency modulation capability. Therefore, there is an urgent need for PV generation to take part in frequency regulation. In this paper, the parallel system of multiple PV generation units is taken as the research object, the virtual inertia control is implemented by modifying the control strategies of each inverter. Based on the response relationship between unbalanced active power excitation and phase output, the influence of control gain coefficient, time constant and phase-locked loop control bandwidth on the inertial characteristics of PV generation is analyzed. Meanwhile, taking two-machine parallel systems as an example, the coordinated operation mechanism of each generation unit in the dynamic process of grid frequency is analyzed, and the distribution mechanism of the unbalanced power in the dynamic process of grid frequency is revealed and applied on a multi-machine parallel system. Finally, the effectiveness of theoretical analysis and the feasibility of the control strategy are verified based on the time-domain simulation examples.