单相光伏逆变器输出滤波电感非线性分析及改进

Nonlinear analysis and improvement of output filtering inductance for single-phase photovoltaic inverter

在单相光伏并网逆变器中,为了降低逆变器输出电流的总谐波失真(THD)值及提高整机效率,需要滤波电感在轻载电流下有足够高的电感值,同时又能在重载电流下保持一定感量。为了解决这个问题,在单相光伏并网逆变器输出滤波电感中采用非线性电感方案。基于工程电磁场理论,运用有限元分析软件深入研究了台阶气隙非线性电感特性的产生机理,发现台阶气隙存在主磁芯局部饱和问题,且切割困难,在工程上难以实现。基于此对非线性电感结构进行改进,提出了一种新的非线性电感结构,与台阶气隙方案相比,改进型的非线性电感结构简单,便于工程实现。从理论上分析该方案的效果,最后仿真和实验验证了所提非线性电感的有效性。

In the single-phase photovoltaic grid-connected inverter,in order to reduce the THD value of the inverter output current and improve the efficiency of the whole machine,the filter inductor needs to have a sufficiently high inductance value under light load current,and at the same time,it can maintain a certain sensitivity requirement under heavy load current.In order to solve this problem,a nonlinear inductance scheme is adopted in the output filter inductor for single-phase photovoltaic grid-connected inverter.Based on the theory of engineering electromagnetic field,this paper uses finite element analysis software to deeply study the mechanism of the nonlinear inductance characteristics of the ladder gap.It is found that the stepped air gap has local saturation problem of the main core,and the cutting is difficult,which is difficult to achieve in engineering.So,a new nonlinear inductance structure is proposed.Compared with the ladder gap scheme,the improved nonlinear inductance structure is simple and easy to implement.The effect of the scheme is theoretically analyzed.Finally,the simulation and experiments verify the effectiveness of the proposed nonlinear inductor.