The Comprehensive Study Of Monitoring And Controlling In Grid-connected Photovoltaic System

With the developing of grid-connected PV system, the problems that exist in the photovoltaic power generation system are running more and more attention. In the light of research status at home and abroad, the paper studies three aspects that are the comprehensive monitoring of the photovoltaic grid power generation, the inverter control in the process of interconnection with the grid and low voltage riding through the problem under the power grid failure.Firstly, the paper develops a set of complete comprehensive monitoring system of PV grid power generation based on virtual instrument technology. The hardware of the monitoring system is supported by the advanced PXI measurement platform and CompactRIO system which are introduced by the national instrument company, then complete the corresponding software design using LabVIEW. This system mainly can complete the following three basic functions through the cooperation of the hardware and software:monitoring of the environment parameters and the running status of the PV grid power station at real-time, detecting the power quality of the common coupling point(PCC) and managing the raw data and the analysis data for secondary using. Moreover, the monitoring system adopts the man-machine interface which is suitable for operation, it’s easy to operate and observe.Secondary, this paper studies the problem of inverter controlling for interconnection with PV grid. Through the analysis of the modeling of inverter, this control strategy can guarantee the output current of the inverter is stable and high quality of the sine wave which provides an important guarantee for PV grid. It also further introduces a power grid voltage feed-forward control method in the double loop control system, it has proven that it can make a good effect in the elimination of the influence of the power grid voltage through the modeling and simulation analysis, at the same time, it can reduce the THD of the grid-connected current effectively.Lastly, this paper studies the problem of low voltage riding through for PV grid power generation system. In this paper we focus on the problem of low voltage riding through in single-phase inverter without transformer, analyzes the ability of the three mainstream of single-phase inverter without transformer in low voltage riding through. We do a comparative analysis through a1KW grid photovoltaic power station, the results shows that the three inverters each have advantages and disadvantages, such test results also provide a certain technical support for the chosen of inverters in engineering application.