The Research And Design Of The Single Phase Photovoltaic Grid-connected Inverter System Based On DSP

Energy shortage and environment pollution because of using of traditional fossil energy have become double burden, which is seriously restricting the sustainable development of our economic social. In order to improve the energy structure and protect the environment, and increase people’s material and cultrual demand, it is urgent to study new renewable energy to replace traditional fossil fuels. Compared with fossil fuels, solar energy is rich in natural resources and widely distributed. With the continuous improvement of related technology and the cost cuts of photovoltaic power generation lowered, photovoltaic power generation becomes a key direction of new energy researches. As the core component of photovoltaic power generation systems, grid-connect inverter is very important for the performance of the whole system.Based on this background, this paper selects a complete single-phase photovoltaic grid-connect inverter as the research object, its topology structure, operational principle, control strategy, circuit design of hardware and sofeware code and so on are studied.Firstly, the research background and significance are introduced, through comparing all kinds of topology structure performance, the boost+signle phase full bridge has been chosed as the two levels of the isolation structure. The circuit working principle is analyzed in detail.The control strategy that the system uses is analyzed. Boost voltage increment circuit and signle phase full bridge are designed independently. Inverter part adopts the control mode of DC voltage outer loop and the inductance current inner ring.This paper uses the compound control strategy of PI+repetitive control based on grid voltage feed forward to adjust the current loop by analysing and comparing the advantages and disadvantages of PI control and repetitive control. The model of the compound control is established in simulink. Simulation shows that the compound control can quickly realize the current tracking, and the waveform distortion rate is lower.The paper also analyses the photovoltaic cell model and its working principle. Based on the output characteristic curve, the three kinds of commonly used Maximum Power Point Tracking algorithm is compared. The paper proposes an improved method which is Variational Step Perturbation and Observation. A model has been established in the simulink to validate at the alaorithm’s effectiveness.Based on the system performance requirements, we design the hardware circuit and software of grid inverter circuit. Hardware circuit includes the main inverter circuit, the minimum system of DSP, signal sampling modulate circuit, the drive amplifying circuit of the Insulated Gate Biploar Transistor and so on. Software employs the combination of main program and interruption. The interrupt consists of Timer interrupt subroutine, AD sampling subroutine, Capture interrupt subroutine and so on.Finally, based on overall research, a single-phase photovoltaic grid inverter prototype whose capacity is 1KW with the TMS320F2812 as its main controller was developed. Part of the test waveform is given.