Study Of The Single Phase Photovoltaic Grid-Connected Inverter System Based On DSP Control

As a result of the infinitly reserves of solar energy resources in the world and thetrend of sustainable social development, solar energy will certainly become the majoralternatives of traditional energy. The main forms of human use of solar energy is theconstruction of solar photovoltaic power station, it convert the solar energy intoelectricity which is indispensable for the social development. At present, most of thephotovoltaic power station has been achieved interconnected to power grid;photovoltaic (pv) grid-connected inverter is the core of the entire grid-connectedsystem.This thesis has a detailed analysis and comparison of grid-connected invertertopology structure, and selects the single-phase two levels non-isolation type structureas the topology of this paper research object, the control chip is TI Company’s 32 bitDSP chip TMS320LF2812.The key technology of photovoltaic grid-connectedinverter is the maximum power point tracking (MPPT) control technology andgrid-collected strategy.This thesis first sets up the simple mathematical model of photovoltaic cells, andintroduces the principle of the MPPT control, then analyses and compares severalwidely used MPPT control strategies at present in detail.On this basis,it puts forwarda kind of variable-step two-way disturbance observer method. That is,it selects threeequidistant points orderly in the the photovoltaic cells P-U characteristic curve, and inthe middle of the working point as the center, the interval between three points isdisturbance step length，using the power information of the three points to change thedisturbance direction and disturbance step; so that working point quickly achievemaximum power point. This method could overcome the oscillation problem whichbrings by fixed step disturbance observation method. Through establishes algorithmsimulation model in Matlab/Simulink; and the simulation results show that when theexternal environment changes, the photovoltaic cells could achieve the maximumpower point tracking.This thesis illustrates several commonly used current control strategies, focuseson the analysis of based on the grid voltage feed-forward compensation currentclosed-loop control strategy and improved hysteresis current control strategy. And itestablishes the simulation model of the two control strategies in the Matlab/Simulink. The simulation results show that the improved hysteresis current control strategy ongrid current control effect is better than the current closed-loop control strategy, sochooses improved hysteresis current control method as the system current controlstrategy.This thesis makes a detailed analysis of typical software design process based onDSP TMS320LF2812 control, concrete including SPWM software implementation,the design of digital phase-locked loop and digital PI algorithm; and gives thesoftware design flow chart separately. Based on this made a test prototype, theprototype experiment results is well.