The Development Of A Three-Phase PV Grid-Connected Inverter

With the fast development of market economy and modern industry, the exhaustion of energy resources and the environmental pollution have become two key points restricting the healthy development of human society. Developing and using new energy sources become more and more important, solar energy has been gradually used because of its advantages such as clearness, enrichment etc. In recent years, photovoltaic (PV) inverter power supply as the leading part of power conversion has been well researched.This paper detailedly analyses the process of designing a 30kVA three-phase PV grid-connected inverter power supply, based on actual item. The major works of this paper are summarized as follows:Firstly, the significance of PV generator and the foreground of PV industry are well summarized; the source of this item and its main content are introduced; the mathematic model of three-phase inverter is analyzed; the topology for three-phase inverter is summarized and the topology of three-phase four-leg is chosen as the main circuit; all kinds of control strategies for three-phase four-leg to resist three-phase unbalance are compared; the two-dimension space vector method is explained in detail and simplified in use, considering the limit of hardware and software.Next, based on the actual guideline, a 30kVA three-phase PV inverter power supply is developed; the filter-mode of LC frame for stand-alone and LCL frame for grid-connected is used, and then the process of designing the filter parameter is concluded; TMS320F2812 is made as the core of the main board, the control circuit of LCD-display, protection, sampling, phase-locked loop are discussed, and the notices in making PCB board is summarized.Subsequently, the programming environment of DSP is introduced; the program of display and key, seven-segment space voltage vector PWM, main process and interrupt process are amply analyzed; the attentive points in programming are concluded; the process of grid-connected operation is conceived; the usage of phase-locked loop and the capture unit are concretely illuminated; the effect of islanding and the method of anti-islanding are narrated.Finally, a kind of max-error control method is used in the MATLAB simulating experiment and gets a well effect; based on all of this, a 30kVA three-phase grid-connected PV inverter power supply is produced; the experimental prototype successfully gets across the debugging in the mode of stand-alone, and also gets a series of experimental waveforms.