准Z源光伏并网逆变器新型PWM调制策略

New PWM Modulation Strategy for Quasi Z-source Photovoltaic Grid Connected Inverter

准Z源逆变器同一组逆变桥臂上下功率管可同时开通,此时,其工作于直通状态,这是传统电压型逆变器不允许的工作状态,准Z源逆变器就是利用该直通来实现其升压功能,为不影响正弦脉宽调制(SPWM)输出电流,都是将直通状态插入在传统SPWM零状态中,故其调制方式与一般逆变系统不同。当前数字SPWM波产生通常利用自然采样法原理,采用数字或模拟方法产生三角波和正弦波,再使用比较器对产生的三角波和正弦波进行比较得到SPWM波。此种方式实现简单但耗费太多硬件资源且不能快速及时响应系统动态变化。在此提出一种变采样周期的新型数字SPWM实现方式。实验结果表明,此种调制方式在节约硬件资源的同时能快速及时的响应系统动态变化,改善逆变器并网电流的波形质量,提高系统的逆变效率。

The same group of quasi Z-source inverter bridge arm on power tube can be opened at the same time in direct working state, which is not permitted by the state in the traditional voltage type inverter, quasi Z-source inverter is to use this to achieve its function through boost.In order not to affect the sinusoidal pulse width modulation （SP- WM） output current,it is to be inserted into the zero state of the traditional SPWM modulation, so the modulation mo- de is different from the general inverter system.The current digital SPWM wave generated usually by use of the prin- ciple of natural sampling, using digital or analog method to generate triangle wave and sine wave, and then use the comparator to carry on the triangle and sine wave and SPWM wave.This method is simple but consumes too much hardware resources and can not respond to the dynamic changes of the system in time.This paper presents a new dig- ital SPWM implementation method for variable sampling period.The experimental results show that,this modulation method can quickly respond to dynamic changes in the system can save hardware resources and improve the quality of grid connected inverter current waveform, improve the system efficiency.