双级式有功备用光伏虚拟同步机控制策略

大规模光伏并网发电导致电力系统面临惯性下降与调频能力不足的问题,迫切需要光伏系统主动参与电网频率调节。以双级式光伏拓扑结构为基础,提出有功备用跟踪的光伏虚拟同步机控制策略。DC\DC侧根据光伏单元运行的最大功率点确定系统的有功备用点,使系统运行在有功备用模式;当电网频率扰动时可调节光伏单元的有功输出来参与一次调频。逆变侧采用与同步机等效的下垂控制方案,将高压直流侧电容模拟为虚拟转子响应功率动态调节,并通过PI控制维持直流电容电压恒定。建立光伏有功调频的小信号模型,运用传递函数分析了直流电容参数对动态性能的影响。在辐照度突降、电网频率突变以及不同系统参数下进行仿真分析,证明了所提方案的有效性。

Two-stage active standby photovoltaic virtual synchronous machine control strategy

Large-scale photovoltaic grid-connected power generation causes a power system to face the problem of inertia decline and insufficient frequency modulation capability. It is urgent to actively participate in the grid frequency adjustment of the photovoltaic system. This paper adopts a two-stage photovoltaic topology and proposes a photovoltaic virtual synchronous machine control strategy for active standby tracking. The DC\DC side determines the active standby point of the system according to the maximum power point of the photovoltaic unit operation, so that the system operates in the active standby mode. When the grid frequency is disturbed, the active output of the photovoltaic unit can be adjusted to participate in the primary frequency modulation. The inverter side adopts the droop control scheme equivalent to the synchronous machine, and simulates the high-voltage DC side capacitor as the dynamic response of the virtual rotor response power, and maintains the DC capacitor voltage constant through PI control. A small-signal model of photovoltaic active frequency modulation is established, and the transfer function is used to analyze the influence of DC capacitance parameters on dynamic performance. The simulation analysis under sudden irradiance drop, grid frequency sudden change and different system parameters proves the effectiveness of the proposed scheme. This work is supported by Natural Science Foundation of Hebei Province (No. E2018502134) and Science and Technology Project of State Grid Liaoning Electric Power Co., Ltd. (No. SGLNDK00DWJS1800091).