Research On Digital Control For Single-phase Grid-connected Pv System

With global energy crisis growing more and more seriously, solar energy as an inexhaustible renewable energy sources has been widely used in recent years. Photovoltaic grid-connected technology has become a research hotspot as coal, oil, natural gas shortages and environmental pollution issues growing.With digital signal processor emergence and development rapidly, digital control system become a development direction of modern power electronics technology with the advantages of anti-interference ability, control flexibility, versatility, advanced control algorithms can be realized as well as real-time control. This paper designs a grid-connected PV system based on DSP (TMS320F2812).In this paper on analyzing of the current domestic and foreign development status of photovoltaic power system, technical issues are analyzed and studied based on a single-phase grid-connected PV system such as MPPT, islanding detection technology, system topology, control strategy, circuit software and hardware design, etc.Grid-connected inverter is the core design of photovoltaic power system. This system uses two-stage structure: pre-stage DC/DC, to achieve power conversion providing a stable voltage for post-stage convert; post-stage DC/AC, to achieve photovoltaic current alternating convert into grid. To overcome the pre-stage shortcomings of low-level conversion efficiency, DC/DC using LLC resonant converter, this converter can achieve primary side switch ZVS opening and secondary rectifiers ZCS turning off, therefore enhancing the system conversion efficiency and providing a steady energy for post-stage. DC/AC uses SPWM drive control, grid-current control is the core of designing, through detecting grid voltage zero-crossing point to achieve the grid-connected current and grid voltage with the same frequency and phase. In the final designed a 500W photovoltaic power grid-connected system, completed hardware design, debug and some control software, gave system simulation results and some experimental waveforms to achieve the proper of the system.