Design Of 2 KW Single-phase Grid-connected PV Generation System

With the development of society and economy, humanity's demand for electricity is increasing while the energy crisis and environmental pollution are aggravating day by day, so it promotes the humanity to the new power generation technology research. Photovoltaic technology has the advantages to become one of the dominant ways of the future power generation. And its development prospect is so large that it has been a research hotspot in recent years. Focused on a single-phase photovoltaic inverter, embarking in the view of engineering realization, an in-depth study on the single-phase grid-connected PV system topology, the main circuit working principle and parameter design, grid-connected control method andcontroller system design are carried on, based on which, a 2 kW single-phase photovoltaic inverter is developed.Firstly the DC/DC/AC circuit structure of the non-isolated high-frequency grid-connected PV system and the working principle of the Boost step-up circuit and the single-phase full-bridge inverter circuit in steady state are analized respectively. Then designed for the capacity and the operating frequency of the system, the values of energy-storage inductor and capacitor in Boost circuit and the filter inductor and capacitor in the LC output filter for the single-phase full-bridge inverter are analyzed and calculated, providing a theoretical basis for selecting circuit parameters of grid-connected PV system.After confirmation of main circuit scheme, holistic control method of single-phase grid-connected photovoltaic power generating system is put forward. Firstly, the electric model of current inner-loop for inverter is established. Then, simulation is adopted to analyze system stability and the influence of current closed-loop tracking ability when chosen with different PI parameters. When PI parameters are finally determined, simulation verification are carried out on the basis of the above parameters, which proves the rationality of the selection. When developing the prototype, variation of PI parameters are liable to give rise to resonance that brings in difficulty at debugging process. Thus, current inner-loop control with power feed-forward combined with dead-beat control method is proposed in the paper. Mathematics model for dead-beat control system is set up, and he simulation result proves its good effect. Eventually, the advantages and disadvantages of two control mode, PI control and dead-beat control, are taken into account synthetically. From the perspective of equipment realization, dead-beat control is chosen in the paper.Maximum power point tracking control and the islanding detection are indispensable for the grid-connected PV generation system.The paper makes a preliminary study on them by contrasting and analyzing the present commonly used control modes and the detection methods and proposing relevant detailed process of realization. Finally the methods suitable for the system are determined.The design and implementation of the hardware and software for controller system is one of the key studies in this paper. Firstly, the main hardware circuit including peripheral sampling circuit, zero capture circuit, dead zone produce circuit and IPM module drive circuit is introduced in detail in this paper and proved effective through experiment. Then the detailed processes of the main program, each interrupt service routines and the liquid crystal display program are proposed.Finally the developed prototype is tested in this paper. The grid current control performance, MPPT control performance and the islanding detection performance are observed. Test result says the prototype reaches the national standard and proves the correctness of the above research and design.