Research On Max-power Point Tracking And Grid-connected Control Of Photovoltaic Generation System

The vast usage of renewable energy sources is to some extent significant, especially forthe situations of energy-short, environmental pollution, and greenhouse effect. Naturally, solarenergy gains widespread application with the rapid development of power electronictechnology in the form of photovoltaic generation. Actually, grid-connected photovoltaicgeneration system is seen as the most effective generation mode in that the ellipsis of batterybank. In this background, some research on this system is done.First, a literature review is done about the development of photovoltaic generation, andthe advantage of this new generate electricity form is analyzed. After the comparison amongdifferent topological structures, the two-stage topological structure is selected as the researchobject, where first-stage DC/DC converter realizes the max-power tracking, and second-stageDC/AC inverter finishes the conversion of electric energy, the selection of main parameters isalso discussed.Then, a mathematic model of photovoltaic battery is established based on the principle ofgenerate electricity, and then the model of photovoltaic array is obtained, based on which theouter output characteristic is analyzed, finally, the maximum power point is obtained undersome temperature and illumination. In this paper, the incorporation of open-circuit voltageand incremental conductance ensures the maximum power tracking; the tracking effect withexternal environment varying is shown in MATLAB simulation.Finally, the control implemented to the converter is divided to two control strategies, thatis, active power control and reactive power control. A dicyclic control strategy, whichcontrains a voltage outer-cycle and a current inner-cycle, is adopted in allusion to the activepower control. The parameters of voltage and current regulator is designed on the basic ofclassical control theory, the THD of grid current is proved to satisfy the GB/T 14549-1993 bysimulation results. The Instantaneous Reactive Power Theory（IRPT）is incorporated intothe study of grid connected photovoltaic generation system aimming at the reactive powercontrol, a harmonic and reactive current real-time detection simulation module is developedbased on pq algorithm, which is put into the simulation experiment of grid connectedphotovoltaic generation system module, the simulation results show that both nonlinear loadreactive and harmonic current obtain effective compensation.