基于阶梯波与瞬时值反馈混合控制的光伏并网级联逆变器

针对传统光伏并网系统结构存在的问题,提出了一种新的阶梯波与电流瞬时值反馈混合控制的光伏并网级联逆变器方案。该方案一部分级联单元采取梯形波控制,一部分级联单元采取带电流瞬时值反馈的倍频正弦脉冲宽度调制,2个部分串联叠加形成输出电压。逆变器输出电压的谐波分析表明:调节正弦脉冲宽度调制波的移相角可以调节输出电压幅值和功率因数;逆变器输出电压低频谐波主要由阶梯波引起,为输出滤波器的设计提供了理论依据。对阶梯波调制逆变器的触发角提出了一种简易算法,该算法适用于电压级差不等模式且可实现触发角在线计算。实验结果表明,该方案结构简单,可靠性高,能有效降低开关损耗。

Photovoltaic Grid-connected Cascaded Inverter Based on Stepped Waveforms and Instantaneous Value Feedback Hybrid Control

Aiming at the problems of traditional photovoltaic grid-connected system structure,a new type of photovoltaic grid-connected cascaded inverter scheme with stepped waveforms and instantaneous value feedback hybrid control.In this method,one part of the cascaded units use stepped waveforms control,the other part use octave sinusoidal pulse width modulation(SPWM) control with instantaneous current feedback.The output voltage comes from the two parts in series.The analysis of the output voltage harmonic shows that the amplitude of the output voltage and the power factor can be adjusted by the SPWM wave phase-shift angles;the low order harmonic of the output voltage is aroused by the stepped waveforms control part,which is the theoretic background for the output filter design.A simple algorithm for the trigger angles of the stepped waveforms modulated inverter is proposed,which is not only fit for the cascaded inverter with different voltage steps,but also fit for online calculation.The experimental results show that this scheme has simple structure,high reliability and low switching loss.