负荷虚拟同步机及其低电压故障穿越控制

负荷虚拟同步机(LVSM)是一种电网友好型负荷并网接口,但其本身不具备低电压穿越能力。为此,文中提出一种适应电网对称与不对称故障的LVSM低电压穿越控制方法。首先,提出LVSM的统一拓扑及其基本控制策略。在基本控制策略的基础上增加电网电压正序分量提取、低电压穿越检测、功率指令变更策略、故障期间使能的负序电流抑制、故障期间电流环输入限幅5个环节,实现电网故障短时间内LVSM不脱网、负荷稳定运行,并最大限度地为电网提供无功支撑。由于LVSM在故障期间保持惯性功率控制,故障结束后功率振荡平滑且有惯性,可有效减轻对电网的暂态冲击。硬件在环实验验证了所提低电压穿越控制方法的有效性。

Load Virtual Synchronous Machine and Its Low Voltage Ride-through Control

The load virtual synchronous machine(LVSM)is a kind of grid-friendly grid-connected interface for loads. However, it does not have the low voltage ride-through(LVRT)capability. For this reason, this paper proposes a LVRT control method for the LVSM to adapt the symmetrical and unsymmetrical faults in the power grid. Firstly, the unified topology of LVSM and its corresponding control strategy are proposed. The extraction of positive sequence component of grid voltage, the detection of LVRT, the change of power setting values, the suppression of negative sequence current and the limitation of input of current loop during a fault are introduced into the basic LVSM controller. It can achieve a short time of grid-connected operation during power failure, the steady operation of loads and the maximal supply of reactive power. Since the LVSM maintains the inertia power control during the fault, the power oscillation is smooth and has inertia after the fault, which can effectively reduce the transient impact on the power grid. The hardware-in-loop experiments are carried out to verify the effectiveness of the proposed LVRT control method.