双级式光伏发电主动参与电网频率调节

为解决大规模光伏发电并网带来系统调频能力不足的问题,提出了双级式光伏发电有功功率-频率下垂控制和虚拟惯量控制,通过修改Boost变换器或网侧逆变器原有的控制结构来实现光伏发电主动参与电网频率调节。并分析虚拟惯性时间常数、锁相环控制带宽对虚拟惯量控制的影响。基于光伏发电的有功功率-相位运动模型、同步发电机组的频率响应模型来分析光伏发电的虚拟惯量特性及其对系统频率动态特性的影响。仿真结果表明:Boost变换器和网侧逆变器均可按照设定的下垂曲线来控制光伏阵列增发或减少一定量的有功功率,抑制电网频率跌落或升高;虚拟惯性时间常数越大或锁相环控制带宽越小,光伏发电的虚拟惯量越大,频率动态过程中可提供支撑的功率越多。

Double-stage grid-connected photovoltaic generation taking part in grid frequency regulation actively

In order to solve the problem of insufficient frequency regulation capacity caused by the large-scale grid-connected photovoltaic generation, the active power-frequency droop control strategy and virtual inertial control strategy are proposed for double-stage grid-connected photovoltaic generation, the original control structure of the Boost converter or the grid-side inverter is changed, so that the photovoltaic generation can actively participate in the grid frequency regulation. The influence of the virtual inertial time constant and the Phase-Locked Loop (PLL) bandwidth on the virtual inertial control is analyzed. The virtual inertial characteristics of photovoltaic generation are analyzed based on the active power-phase motion model of photovoltaic generation and the frequency response model of the synchronous generator, and their influence on the dynamic characteristics of the system frequency is also analyzed. Simulation results indicate that both the Boost converter and the grid-side inverter can control the photovoltaic array to increase or decrease the active power generated according to the set droop curve, so as to suppress the drop or rise of the grid frequency; larger virtual inertial time constant or smaller PLL bandwidth can lead to larger virtual inertia of photovoltaic generation and more power in the frequency dynamic process. This work is supported by National Natural Science Foundation of China (No.51277024) and Science and Technology Project of the Headquarter of State Grid Corporation of China (No. 5229DK17000W).