基于下垂系数自适应调节的VSG控制策略

An Adaptive Drooping Coefficient Adjustment Strategy for the Virtual Synchronous Generator

虚拟同步发电机技术(VSG)促使电路中无旋转元部件的分布式电源具有了同步发电机的有功频率及无功电压调节特性,但离网运行模式下,VSG的一次调频与一次调压本质上是一种下垂控制,属于有差调节,负载功率的改变,将导致其输出频率和相电压幅值偏离。针对此问题,通过分析VSG有功功率变化与频率变化之间的关系、无功功率变化与电压变化之间的关系及功率调节的动态特性,选取下垂系数作为优化对象,引入参数自适应调节的方法,提出一种下垂系数依据实际情况自行调整的改进型VSG。仿真结果表明,在离网运行模式下,改进后的控制策略与传统VSG相比,不仅能维持微电网功率平衡,而且实现了频率的无差调节和相电压幅值调节的小偏差。

The technology of virtual synchronous generator（VSG） make the distributed generation have active frequency and reactive voltage regulation characteristic without inertia, which like synchronous generator＇s performance in the circuit. While in mode of island operation, the primary frequency modulation and voltage modulation of VSG belong to the droop control, as well as non-difference control. And the change of load power will lead to the deviation of its output frequency and phase voltage amplitude. In view of this problem, it is possible to analyze the features in VSG, including the relationship between active power change and frequency change, reactive power change and voltage change, alone with the dynamic characteristics of power regulation. Taking droop coefficient as an optimization object and introducing parameter self-adaptive adjustment method, an improved VSG is pro- posed to adjust the droop coefficient according to the actual situation. The simulation show that improved control strategy has better performance compared with the traditional VSG, which not only maintains the power balance of microgrid, but also achieves the small deviation of frequency adjustment and phase voltage amplitude adjustment.