RoCoF下垂控制的直驱式风电系统惯量特性分析

直驱式风电机组大规模接入电网，导致传统电网的惯量减小，电网频率支撑能力相对减弱，在受到扰动时更容易引起电网频率偏移和频率变化率过大。针对此类问题，本文首先提出一种频率变化率(the rate of change of frequency, RoCoF)下垂控制策略，旨在提高直驱式风电系统的惯量作用，抑制频率偏移量和RoCoF。其次，类比传统同步机在机电时间尺度下的动态分析理论和方法，建立了风电系统在直流电压时间尺度(DC-Voltage Timescale, DVT)下的动态模型。基于所建立的DVT动态模型，采用经典的电气转矩分析法研究了风电系统的惯量效应，揭示了主要的控制环节对风电系统惯量特性的影响规律、主导因素与作用机制。最后，对传统的频率偏差下垂控制与本文提出的RoCoF下垂控制策略进行了详细的对比，并通过实验验证了所提出的控制方法和分析结论的正确性。

Inertia Characteristic Analysis of RoCoF Droop Control Based Direct-driven Wind Power System

With the large-scale connection of direct-drive wind turbine (WT) to the power grid, the inertia of traditional power grids has been reduced, and the grid frequency support capacity has been relatively weakened, leadings to the serious issues of the grid frequency deviation and the rate of change of frequency (RoCoF). In this paper, firstly , a RoCoF droop control strategy, is proposed to improve the inertia performance of the wind power system. Secondly, the dynamic model over the DC-voltage timescale (DVT) of the WT is established by analogy to the dynamic analysis theory and method of the traditional power grid over the electromechanical time scale. Based on the DVT dynamic model, the classic electric torque analysis is used to investigate the system inertia effects, the physical mechanism, the dominant factors and the basic principles of the main control links for improving the inertia effect of the direct-drive wind power system. Finally, the comparison between conventional frequency droop control and the proposed RoCoF droop control is carried out in detail, and the correctness of the proposed control mode and the analysis conclusion is verified.