基于VSG控制的并网逆变器故障穿越控制策略
Fault Ride-Through Control Strategy of a VSG-Controlled Grid-Connected Inverter
-
摘要: 随着以新能源为主体的新型电力系统加速演进,变流器的并网控制策略及其故障穿越能力成为系统安全稳定运行的关键。本文首先对比分析了构网型与跟网型变流器在电网故障下的响应特性差异,明确了构网型变流器作为电压源在电压跌落时面临过流挑战的本质原因。在此基础上,针对采用虚拟同步机(Virtual Synchronous Generator, VSG)控制的构网型变流器,提出一种面向对称电压跌落的低电压穿越(Low Voltage Ridethrough, LVRT)控制策略。该策略核心包括:采用虚拟阻抗抑制稳态过流,以及通过功率指令瞬时同向调节抑制暂态冲击电流。仿真与实验结果表明,所提方法能有效将故障电流限制在安全阈值内,并在穿越过程中始终保持构网型变流器的电压源特性,为构网型变流器的安全并网运行提供了可行的解决方案。Abstract: With the accelerated evolution of new power systems dominated by renewable energy, the grid-connection control strategies and fault ride-through capability of converters have become crucial for ensuring secure and stable system operation. This paper first compares and analyzes the difference in response characteristics between grid?forming and grid?following converters under grid faults, clarifying the inherent reason why grid?forming converters, as voltage sources, face overcurrent challenges during voltage sags. On this basis, for a grid?forming converter adopting virtual synchronous generator control, a low?voltage ride?through strategy oriented to symmetrical voltage sags is proposed. The core of the strategy includes: employing virtual resistance to suppress steady?state overcurrent, and instantaneously adjusting active and reactive power commands in the same direction to suppress transient inrush current. Simulation and experimental results show that the proposed method can effectively limit the fault current within a safe threshold and consistently maintain the voltage?source characteristics of the grid?forming converter throughout the ride?through process, providing a feasible solution for the safe grid?connected operation of grid?forming converters.
下载: