单相光伏微网逆变器的建模与电流跟踪数值模拟

Modeling and Current Tracking Numerical Simulation of Single-phase Photovoltaic Micro-grid Inverter

摘要:

以光伏微网逆变器的输出电压为控制信号,输出电流为输出信号,并考虑线路等效电阻,先对单相光伏微网逆变器电路进行简化并分析其工作原理,然后根据电压回路方程,建立单相光伏微网逆变器的微分方程,接着建立求解方程的四阶龙格-库塔法的迭代模型,再从微分方程的解析解中进行简化和离散化后,利用线性预测控制方法得到逆变器输出控制信号表达式,最后进行数值模拟和分析。通过数值模拟,对逆变器的输出电压、电流的时域波形和频域波形进行分析,并对输出电流的误差信号进行测量,结果表明：所建立的单相光伏微网逆变器模型及求解迭代模型是有效的,在耦合电感为1mH、开关频率为10KHz条件下,逆变器输出电流、电压总谐波失真度分别为1.76%、3.99%,逆变器输出电压的纹波峰值达50V,但其输出信号总谐波失真度满足国家并网的标准(≤5%)。

Abstract:

Selecting the output voltage of the photovoltaic micro-grid inverter as the control signal and the output current as the output one, and considering the equivalent resistance of the circuit, the circuit of the single-phase photovoltaic micro-grid inverter is simplified and its working principle is analyzed. Then, its differential equation is created based on the voltage loop equation. Then the fourth-order Runge-Kutta iterative model for the solve equation is created. After simplifying and discretizing the analytic solutions of the differential equation, the expression of the output control signal of the inverter is obtained through the linear predictive control method and finally the numerical simulation and analysis are conducted. Through numerical simulation, the output voltage and current waveforms in both time and frequency domain which belong to the inverter are analyzed, and the error signals of output current are measured. The results show that: The model of single-phase photovoltaic micro-grid inverters and the iterative model for the solve equation are effective. Under the condition of 1 mH coupling inductance and 10 KHz switching frequency, the voltage of and the total harmonic distortion of the output current of the inverters are 1.76% and 3.99% respectively. The peak ripple of its output voltage is 50V, but the total harmonic distortion of its output signal meets the requirements of the standard of national grid connection (≤5%).