SiC器件三电平分裂输出高开关频率光伏逆变器及其死区效应研究

The adoption of silicon carbide (SiC) devices in conventional three-level photovoltaic inverters can cause issues of crosstalk effect, deteriorated switching performance with parasitic elements, electromagnetic interference (EMI), etc. And the high-switching-frequency operation can bring serious dead-time effect. In this project, SiC devices are adopted in the three-level split output photovoltaic inverter, to reveal its advantages, disadvantages, and challenges in high-switching-frequency applications. The design of the inverter will be optimized and the dead-time effect at high switching frequencies will be solved.. The modified double pulse test will be applied to the three-level split output inverter with SiC devices for the investigation on crosstalk, switching performance, EMI, loss of split inductors, and synchronous rectification. The SiC MOSFET driver, the power circuit, and the split inductor will be optimized to reduce the crosstalk and EMI, and improve the switching performance and efficiency. A high-switching-frequency dead-time compensation with zero-sequence component injection will be proposed to enhance the linear modulation region; and a closed-loop control strategy for the dead-time elimination half-period modulation with two groups of modulation waves will be proposed, where the current zero-crossing distortion will be suppressed as well; then the modulation without dead-time will be optimized based on the relation of shoot-through time, shoot-through current, split inductance, and loss of split inductors. The operation of 100kHz high switching frequency will be finally achieved with high efficiency, high power density, high DC-link voltage utilization, low output current harmonics, and low EMI.

传统SiC器件光伏逆变器存在串扰效应、开关特性易受寄生元件影响、EMI等问题，并且在高开关频率下存在严重的死区效应。本项目将SiC器件应用于三电平分裂输出光伏逆变器，探究其在高开关频率应用中的优点、缺点及挑战，优化设计并解决高开关频率死区效应问题。. 项目将改进双脉冲测试方法，用于研究SiC器件三电平分裂输出光伏逆变器的串扰效应、开关特性、EMI、分裂电感损耗、同步整流；对分裂电感、驱动和功率电路优化设计，降低串扰效应和EMI、提升开关特性和效率。提出一种高线性调制区的零序分量注入高开关频率死区补偿方法；提出一种兼顾改善电流过零点畸变的双组调制波无死区半周调制闭环控制策略；研究直通时间、直通电流、分裂电感及其损耗之间的关系，提出一种不加死区的优化调制方法。最终实现SiC器件三电平分裂输出光伏逆变器的100kHz高开关频率、高效率、高功率密度、高直流电压利用率、低输出电流谐波、低EMI运行。

在光伏发电系统中，将SiC功率开关器件应用于T型三电平分裂输出逆变器，可使其工作于更高的开关频率，减小无源滤波器的重量和体积，进一步提高光伏逆变器的效率和功率密度。但是，若采用含有死区的传统调制方式，死区效应会随开关频率升高而恶化。传统死区补偿策略会直接或间接增加调制波幅值，使线性调制区下降严重。. 本项目围绕SiC器件T型三电平分裂输出逆变器及其高开关频率死区效应展开研究。首先，研究了三电平分裂输出高开关频率SiC器件逆变器的低谐波控制系统及调制方法，提出三电平无死区效应高开关频率PWM以及基于DSOGI-FLL的无死区半周调制闭环控制策略。其次，兼顾抑制死区效应，对无死区半周PWM的电流过零点畸变现象进行了优化，提出能够生成同步整流减小通态损耗的高频调制策略，提出基于DSOGI-FLL的具有死区补偿功能的低开关损耗组合DPWM。此外，针对控制周期更短的高开关频率SiC器件三电平逆变器提出abc坐标下的解析简化算法，研究了用于T型三电平SiC器件逆变器的分状态脉冲测试方法，获得器件开关特性、分流情况，衡量逆变器性能指标。. 项目研究成果使SiC器件光伏逆变器在高开关频率下可靠运行，提高了输出电能质量和效率，促进了高开关频率SiC器件在新能源发电中的应用，助力“碳达峰、碳中和”目标的实现。

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