Analysis on inertia and damping mechanism of grid-connected power generation system integrated with photovoltaic and energy storage systems

Abstract

The grid-connected power generation system integrated with photovoltaic (PV) and energy storage systems (ESSs) is taken as the research object, and multiple time scales are used in the modeling ideas. Focusing on the main time scale affecting the dynamic characteristics of system frequency-the DC voltage time scale, this paper develops a dynamic model of DC voltage time scale for the analysis of the system inertia and damping characteristics. On the basis of this model, the electric torque analysis method is used to analyze the main factors and their action laws on the inertia effect, damping capacity and synchronization characteristics from the physical mechanism level. The research results show that the dynamic characteristics of the system are determined by its control parameters, structural parameters and steady-state operation point parameters. The inertia effect and synchronization characteristics of the system are respectively affected by the proportional controller and integral controller in the DC bus voltage control loop. The damping capacity of the system is mainly affected by the frequency droop control in the energy storage device. The system dynamic characteristics will not be affected by the PV converter operating in the maximum power point tracking (MPPT) mode. In addition, the system dynamic characteristics are also affected by the structural parameters (such as line impedance and DC bus capacitance), the steady-state operation point parameters (such as the AC/DC bus voltage level of the system) and the steady-state operation power (power angle). Finally, the correctness of the above analysis is verified by the simulation and experiment results. 以光储一体化并网发电系统为研究对象，利用多时间尺度建模的思想，聚焦于影响系统频率动态特性的主要时间尺度——直流电压时间尺度，建立了用于系统惯量阻尼特性分析的直流电压时间尺度动态模型。在此模型的基础上，利用电气转矩分析法从物理机制层面上分析了影响系统惯量效应、阻尼能力以及同步特性的主要因素及其作用规律。研究结果表明：系统的动态特性由其控制参数、结构参数以及稳态工作点参数共同决定。直流电压母线控制环中的比例控制器、积分控制器分别影响系统的惯性效应和同步特性；储能装置中的频率下垂控制主要影响系统的阻尼能力；工作在最大功率点跟踪模式的光伏变流器则无法影响系统的动态特性。此外，系统的动态特性还受到线路阻抗、直流母线电容等结构参数以及系统交/直流母线电压等级、稳态运行功率（功角）等稳态工作点参数的共同影响。仿真和实验结果验证了上述分析结论的正确性。