虚拟同步发电机单机并网小信号模型及其稳定性分析

Small-signal Modelling and Stability Analysis of One Virtual Synchronous Generator Connected To the Utility Grid

目前可再生能源发电设备一般不具备支撑电网运行的能力。随着可再生能源在电网中占比的不断提高,其弱支撑性问题越来越显著。为解决上述问题,有学者提出了虚拟同步发电机技术(Virtual Synchronous Generators,VSG),该技术可以使可再生能源发电设备模拟同步发电机,为电网提供调压和调频支撑。虽然VSG技术可以提高可再生能源对电网的支撑性,但有可能导致可再生能源发电设备在运行时出现振荡,危及电网的安全运行。为分析和解决上述问题,本文对单台VSG并网系统的各个环节进行了详细的建模,得到了系统的小信号模型。在此基础上,分析了VSG不同控制参数对系统稳定性的影响。分析和仿真结果表明,当VSG控制参数设置不合理时,系统会出现振荡,需要合理设置VSG控制参数以保证电网的安全稳定运行。

Currently,the renewable energy equipments have no ability to support the power grid. With the increase of renewable energy in power grid,the lack of support problem by the renewable energy becomes more and more important. To solve this problem, some researchers proposed the virtual synchronous generators technology. This allows renewable energy to simulate traditional synchronous generators to provide frequency and voltage support for power grid. However,this technology would lead to oscillations between the VSG and the power grid which threatens safety operation of the power grid. This paper is to analyze the system of one VSG connected to the utility grid. We first model all the components of the system and obtain the linearized small-signal model of the whole system. Based on this model, we analyze the impacts of different parameters on the system stability. It shows that the system becomes unstable and oscillatory with improper parameters. Therefore,the VSG parameters must be tuned properly to ensure power grid normal operation.