Analysis of Inertia Mechanism of Grid-tied Photovoltaic Power Generation System With Virtual Inertia Control

In the absence of energy storage, photovoltaics (PV) also need to provide inertia support to the power electronic power system. Based on the DC bus voltage droop control to provide the inertia of the converter, two improved virtual inertia control strategies are proposed. From the perspective of DC bus voltage Udc and system virtual inertia coefficient Hv under load disturbance, the advantages and disadvantages of three virtual inertia control strategies and the influence of control parameters on system inertia are analyzed. The conventional droop control is a full-band response load disturbance, and the inertia coefficient Hdpincreases with the droop coefficient $K$dp increases, but the DC bus voltage cannot be restored to the initial set value. The improved low-pass filter control (ILPFC) only responds to the load disturbance in the low frequency band. In fact, a delay link is introduced on the basis of the conventional droop control to slow down the frequency response speed, and increasing the K1 or ω1 can also increase the system inertia effect. The improved high-pass filter control (IHPFC) only responds to load disturbances in the high frequency band, overcomes the problem that the conventional droop control cannot restore the DC bus voltage to the initial set value. Meanwhile, increasing Kh or decreasing ω$h$ can also improve the system inertia support. Finally, the effectiveness of the control strategy and the correctness of the analysis conclusion are verified by simulation.