光伏并网发电系统的虚拟惯量控制策略

Virtual Inertia Control Strategy for Grid-tied Photovoltaic Power Generation System

针对直流电容电压下垂控制(常规虚拟惯量控制)使得其直流母线电压易受负荷波动影响而偏移额定值的问题,提出了2种改进虚拟惯量控制策略,即基于低通滤波器的虚拟惯量控制和基于高通滤波器的虚拟惯量控制。首先,从负荷扰动下直流母线电压Udc和系统虚拟惯量系数Hv变化的角度,分析控制参数对系统惯量的影响规律。其次,通过频率扰动下的直流电压响应规律,对比3种虚拟惯量控制策略的优劣性。然后,建立考虑有限大容量微电网的光伏系统数学模型,作为虚拟惯量控制参数的设计依据。研究结果表明:基于低通滤波器的虚拟惯量控制实质上是在常规虚拟惯量控制的基础上引入了一个延时环节,以减缓频率响应速度,增加Kl或ωl也可提升系统的惯量效应;基于高通滤波器的虚拟惯量控制克服了常规虚拟惯量控制不能恢复高压侧直流母线电压至额定值的问题,增加Kh或减小ωh也可提高系统的惯量支撑。最后,通过仿真和实验验证了控制策略的有效性以及分析结论的正确性。该研究为光伏系统给电网提供惯量支撑奠定了理论基础。

In order to solve the problem that the DC capacitor voltage droop control (conventional virtual inertia control)makes the DC bus voltage susceptible to load fluctuation and shift out of the rated value,we propose two improved virtual inertia control strategies,which are virtual inertia controls based on low-pass filter and high-pass filter.Firstly,from the perspective of DC bus voltage Udc and system virtual inertia coefficient Hv under load disturbance,the influence law of control parameters on system inertia is analyzed.Secondly,the advantages and disadvantages of the three virtual inertia control strategies are compared by the DC voltage response law under frequency disturbance.Then,the mathematical model of the photovoltaic system where the finite large micro-grid is taken into consideration is established,which can be used as the design basis for the virtual inertia control parameters.The research results show that the virtual inertia control based on the low-pass filter is based on the conventional virtual inertia control,which introduces a delay link to slow down the frequency response speed.Increasing Kl orωl can improve the inertia effect of the system.The virtual inertia control based on the high-pass filter overcomes the problem that the conventional virtual inertia control cannot restore the high-voltage DC bus voltage to the rated value.Increasing Kh or decreasing ωh can also improve the system’s inertia support.Finally,the effectiveness of the control strategy and the correctness of the analysis conclusion are verified by simulation and experiments.This study lays the theoretical foundation for photovoltaic systems to provide inertia support for the grid.