Design And Research Of Three-phase Synchronous Phase-locked Inverter

As an AC power supply, three-phase inverter is widely used in electric power equipment, electric vehicles, large uninterrupted power supply (UPS), and new energy conversion, etc. Along with the more and more applications of three-phase inverter, requirement for the inverter is getting higher and higher. Although the traditional off-line three-phase inverter has a breakthrough in waveform quality, power density, reliability, etc, but it still cannot meet demand in three-phase inverter connecting to grid, redundant power supply, parallel operation of three-phase inverter and so on. In such circumstances, it needs that three-phase inverter has synchronous phase-locked function.In allusion to three-phase inverter used in redundant power supply, parallel operation, distributed power generation, and other special applications, three-phase synchronous phase-locked inverter is designed by using digital signal controller (DSC) as main controller in this thesis. The output voltage, current, frequency, phase and other parameters can be controlled effectively, and synchronous operation is realized. In synchronous operation, The phase of three-phase inverter is kept same with load or grid.At first, design schemes are compared and expatiated from the three-phase inverter circuit topology structure, modulation mode, phase lock mode to control strategies, and the overall system design scheme is determined. And then the inverter hardware circuit designs are expatiated in detail. These designs mainly include: inverter power circuit design, the selection of power circuit switching device, output filter circuit design; Control circuit hardware design, DSC minimum system design, data acquisition circuit design and protection circuit design; Auxiliary power supply design. Based on the hardware circuit designs and the depth knowledge of three-phase inverter modulation technique, phase lock technology and control technology, the system software is designed, including the main program design, interrupt service routine design and the main control software design. In the main program design, the main program flow chart is drawn, and the optimization methods of data computing are introduced; Interrupt service routine design focuses on introducing the ADC interrupt service routine, and the program flow chart is drawn and analyzed; In the main control software design, the inverter software design based on SVPWM modulation and digital PI control software design are introduced in detail.Finally, the simulation and experiment results are given. The research is based on Matlab simulation platform of the three-phase grid-connected inverter and the system experiment platform. The results show that:the three-phase synchronous phase-locked inverter can realize synchronous phase-locked function; in the grid-connected inverter, inverter output three-phase AC phase is consistent with the grid phase, and the active power and reactive power input to the grid can be controlled effectively.