大电网中虚拟同步发电机惯量支撑与一次调频功能定位辨析

随着可再生能源渗透率的不断提高,同步电网的惯量和一次调频的能力都在不断下降,而如果可再生能源发电采用虚拟同步发电机(VSG)技术,则可以在大功率缺额冲击下对减小系统频率变化率和频率偏差做出应有的贡献。针对VSG研究中惯量支撑与一次调频功能定位不清晰的现状,亟须明确VSG在大电网中应用时此两者的功能定位需求。文中深入分析了VSG的惯量支撑功能及其物理意义,推导了VSG的惯量支撑功率表达式,辨析了VSG惯量支撑功能与一次调频功能的定位区分,仿真分析了VSG在大型同步电网频率事故过程中采用不同控制功能对系统频率变化的作用。最后指出,在大型同步电网中,一次调频能力下降比系统惯量下降所带来的影响更为严重,因此较之于短时的惯量支撑功率,系统更需要VSG发挥一次调频功率的持续支援作用。

Functional Orientation Discrimination of Inertia Support and Primary Frequency Regulation of Virtual Synchronous Generator in Large Power Grid

As the penetration of renewable energy increases continuously, the inertia of synchronous power grid and the ability of primary frequency regulation are declining. If renewable energy power generators adopt the virtual synchronous generator(VSG)technology, they can make due contributions to slow down the rate of system frequency variation and reduce the system frequency deviation under the impact of large power shortage. Aiming at the current situation of unclear functional orientation of inertia support and primary frequency regulation in the research on VSG, it is urgent to define the functional orientation demand of both inertia support and primary frequency regulation of VSG in its application in the large power grid. Firstly, this paper analyzes the inertia support function of VSG and its physical meaning. Then the expression formula of inertia support power of VSG is deduced. Secondly, the distinction between the inertial support function and the primary frequency regulation function of VSG is analyzed in detail. Thirdly, this paper simulates and analyzes the roles of the VSG using different control functions in the dynamic characteristic of system frequency changing caused by power imbalance in the large-scale synchronous grid. Finally, it is pointed out that, in a large synchronous power grid, the impact brought by reduction of primary frequency regulation ability is more serious than that brought by the decrease of system inertia. The power system needs the continuous power support of VSG for the primary frequency regulation more than short-term inertia support power.