Research On Three Phase Grid-Connected Inverter Based On SVPWM Control

The energy crisis and environmental pollution restrict the development of human economy. Finding and developing clean and renewable energy is becoming an effective solution to alleviate energy crisis and control environmental pollution. People are paying more and more attention to the development and utilization of new energy sources such as solar energy or wind energy. Solar energy with its clean, widely distributed and inexhaustible characteristics, is getting more and more attention form people. Photovoltaic power generation is an important form of solar energy utilization, it converts solar energy directly to electrical energy. Grid inverter is an important interface between photovoltaic power generation device and power grid, it plays an important and decisive role in grid power quality.Firstly this paper briefly introduced the background of photovoltaic power generation and the national standard of grid-connected technology, and then summarily introduced the topological structure of three-phase grid-connected inverter, filter, control strategy,modulation mode and island detection methods.According to the characteristics of three-phase grid-connected inverter control, the mathematical model and the design of controller are established under the synchronous rotating reference frame. The design of controller includes current decoupling between d-axis and q-axis, feed-forward decoupling of grid voltage and the design of current regulator. And this paper introduced the principle and digital realization of the prevalent Space Vector Pulse Width Modulation(SVPWM) method, then verified by simulation.With the non-detection zone problem of most island detection methods, this paper introduced low frequency phase perturbation method(ALFD) and described the principle of ALFD, then focused on the island detection method of three-phase grid-connected inverter which use ALFD, and verified the principle by simulation in Matlab/Simulink.At last a three-phase grid-connected inverter prototype controlled by STM32F103VCT6 is designed and completed. This paper presented technical indicators of the prototype, and introduced it from two aspects respectively, which includes hardware circuit design and software implementation method. In the aspect of hardware circuit design, this paper mainly introduced the concrete realization of each function module. In the aspect of software implementation method, this paper focused on the structure ofsystem program and the flow chart of each function module. The paper also introduced the software phase lock technology, off-grid experiment, grid-connected experiment, electric current loop experiment of three-phase grid-connected inverter. The experimental results coincide with theoretical analysis, it validated that theoretical analysis is correct.