The pulse width modulation inverters are widely applied as interface for connecting renewable energy sources with the utility grid. In order to smooth the current injected into the grid, the switching harmonics generated by the inverter must be properly filtered out to comply with stringent grid standards specified by IEEE519-1992 and IEC61727-2004. The LCL filter shows a great attenuation with high-frequency harmonics and can meet the requirements of harmonics attenuation even at lower switching frequencies. On the other hand, as the price/performance ratio of microcontrollers decrease, there is an increasing trend of implementing high sampling frequency in the digital control. Multisampling as a potential candidate can be used to achieve a robust and smart control for the grid-connected inverter.

In view of current control, as shown in Fig. 1, there will be three aspects of research points. Firstly, optimum value of multisampling factor needs to be presented in order to fully exploit the interests in the control system. Secondly, multisampling technology can reduce control delays and break the bandwidth limitations. It will be used in different active modes in this project so as to extend the range of application. Thirdly, the switching harmonic is also sampled in the process of multisampling, which will trigger dead bands and disturbance in the system. A ripple suppression algorithm will be presented in this project.

In view of smart control, a smart control for the grid-connected inverter will be achieved because we can get more information through multisampling. As the signal-to-noise ratio in the aspect of current measurement noise will be improved based on multisampling, the basic goal is to achieve dead-time compensation and fault diagnosis. Moreover, new applications of multisampling in the grid-connected inverter should be also explored in the project.

Simultaneously, this Ph.D. project aims to build a FPGA-based grid-connected inverter demonstrator along with the multisampling research. Thereby, the scientific findings could be practically validated using the demonstrator.

Funding: China Scholarship Council (CSC).
Effektiv start/slut dato01/01/201930/06/2022


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