In this article, one of the most recent multilevel converter topologies named packed U-cells is developed for three-phase grid-connected inverter mode using photovoltaic input voltage sources. This topology makes a very important research subject in what concerns the adaptation of multilevel inverters with photovoltaic systems. According to the literature, it is well applicable with the string type and suitable for high-voltage applications because the number of switches is less than conventional topology and maximum blocking voltage is U_dc and 2U_dc; however, it is not applicable for multistring type and unsuitable for the central type because it is based on isolated DC source. The packed U-cells topology is highly optimized from the point of view of the number of passive and active components. The output voltages of our converter are composed by seven levels obtained by the auxiliary buses voltages regulation. In order to obtain the DC input voltages of 120 V for the inverter, photovoltaic generators are connected to a boost converters. The maximum power point tracking method based on the Perturb and Observe was used to improve and optimize the performance of the photovoltaic system control in the simulation part. The grid-connected PUC7 inverter operates with a unit power factor and injects active power into the grid. The control is configured to make the current waveform in phase with the AC voltage waveform. Reference angle variations have been made to operate with different power factors to test the performance of the applied control and the influence of these variations on the auxiliary buses voltages regulation. The simulations were done under Matlab/Simulink platform and have been experimentally verified using dSpace 1104 controller board and three-phase packed U-cells inverter composed by nine half-bridge insulated-gate bipolar transistor modules.

在本文中，开发了一种最新的多级转换器拓扑结构，称为打包U单元，该拓扑结构使用光伏输入电压源，用于三相并网逆变器模式。这种拓扑成为涉及光伏系统中多电平逆变器的适应性研究的重要课题。根据文献，由于开关的数量少于常规拓扑，并且最大阻塞电压为U _dc和2 U _dc，因此适用于串型并且适用于高压应用; 但是，由于它基于隔离的DC电源，因此不适用于多字符串类型，也不适合中央类型。从无源和有源组件的数量来看，压缩的U单元拓扑得到了高度优化。我们的转换器的输出电压由通过辅助总线电压调节获得的七个电平组成。为了获得用于逆变器的120 V直流输入电压，光伏发电机连接到升压转换器。仿真部分采用了基于扰动和观测的最大功率点跟踪方法来改善和优化光伏系统控制的性能。并网的PUC7逆变器以单位功率因数运行，并将有功功率注入电网。控制器配置为使电流波形与交流电压波形同相。已使参考角度变化可以在不同的功率因数下运行，以测试所应用控制的性能以及这些变化对辅助总线电压调节的影响。仿真是在Matlab / Simulink平台下完成的，并已使用dSpace 1104控制器板和由九个半桥绝缘栅双极晶体管模块组成的三相U型逆变器进行了实验验证。