向弱电网供电的VSC-HVDC系统的模拟惯量控制策略研究

针对采用VSC-HVDC向弱电网供电时，受端弱电网惯量不足而出现扰动下暂态频率偏移较大的问题，提出了一种模拟惯量控制策略，以增大受端弱电网的惯量，从而提高系统的频率质量。为此，在对比换流站直流侧电容和同步发电机转子储能特性的基础上，建立了直流电压与系统频率的映射关系，从而得出了换流站所模拟惯量的具体计算等式。利用PSCAD/EMTDC就三种扰动下对VSC-HVDC逆变侧换流站分别采用传统控制和所提模拟惯量控制时进行了仿真比较。仿真结果表明，所提模拟惯量控制策略能够减小扰动下受端弱电网暂态频率偏移，提高受端弱电网的频率质量。

Emulation inertia control strategy for VSC-HVDC supplying weak network

When the VSC-HVDC transmission system is employed to the weak grid, which is comparatively lower or no inertia, hence the large transient frequency deviation problem is always happened under the disturbances. In order to increase the inertia of the receiving grid, this paper proposes a emulation inertia control strategy, which significantly improves the system frequency quality. Based on the comparisons between the DC capacitance of the converter and the energy storage features of synchronous generator rotor, the relationship between DC voltage and system frequency is built. And then the specified formula for the emulation inertia calculation is given. The inverter station of the VSC-HVDC system with conventional control strategy and the proposed emulation inertia control strategy respectively is tested under different disturbances using PSCAD/EMTDC. Simulation results show that the proposed emulation inertia control strategy can better suppress the fluctuation frequency under the disturbances and improve the system frequency quality.