Abstract
Due to the lack of inertial support of the physical rotor of reliable power, the problem of weak inertia of the system is prominent when large-scale grid connection. Aiming at the weak inertia problem of new energy power systems, this paper takes the photovoltaic power generation system with generalized droop control as the research object. Firstly, the paper introduces the structure of the photovoltaic power generation system and the mathematical principle of generalized droop control At the same time, the electrical torque model of the system is established in order to reveal the inertia characteristics of the grid-tied inverter under the generalized droop control, moreover, the influencing factors of the system’s inertia characteristics and the influence rules of parameters are analyzed and studied. Finally, simulation analysis verifies the correctness of the analysis. The research results show that the photovoltaic inverter system under the generalized droop control has obvious inertia characteristics, the change of inertia size is affected by the dominant zero pole of the controller, and the equivalent inertia coefficient has frequency domain characteristics.
Highlights
In recent years, the large-scale grid-connection of electric vehicles and flexible transmission and distribution equipment and application of renewable energy have caused tremendous changes in the composition of structure in the traditional power system[1,2,3,4], and profoundly changed the dynamic behavior of the power system [5,6,7]
In order to solve the problem of weak inertia caused by the injection of renewable energy sources, the virtual synchronous generator (VSG) control strategy has emerged [12,13] based on the frequency operation characteristics of synchronous generators
It is noted that the VSG strategy equips the inverter system with inertia characteristics, it can cause system instability in the grid-connected mode. [17] pointed out that while the VSG strategy provides the SG inertia, it inherits the risk that the SG is prone to oscillations, namely, when the system is disturbed, the system frequency will observe continuous oscillations. [18] and [19] analyzed the virtual torque characteristics and instability mechanism of the VSG
Summary
The large-scale grid-connection of electric vehicles and flexible transmission and distribution equipment and application of renewable energy have caused tremendous changes in the composition of structure in the traditional power system[1,2,3,4], and profoundly changed the dynamic behavior of the power system [5,6,7]. In order to solve the problem of weak inertia caused by the injection of renewable energy sources, the virtual synchronous generator (VSG) control strategy has emerged [12,13] based on the frequency operation characteristics of synchronous generators. Through the additional compensation control of the frequency-active power loop in the droop control, the inertia characteristics of the inverter are realized, the operation under different working conditions is well realized. [23] summarized the stability analysis methods of grid-connected inverter systems, and pointed out that the equivalent characteristic coefficients of gridconnected inverters under the electric torque analysis have frequency-dependent characteristics, yet the conclusion was not verified in a specific system. The simulation analysis verifies the effectiveness of the inertia characteristic analysis in this paper
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