Research On MPPT Algorithm And Implementation Of DSP For PV System Operating Under Complex Conditions

With the situation of energy resource crisis and the problem of circumstance pollutionbecome more and more severity, exploitation and utilization of the green solar energyresource is imperative. And the most widely used is the use of Photovoltaic (PV). However,partially shaded and illumination inequality conditions are common in the use of PVsystems. The resulting mismatch phenomenon of the array not only affects the powergenetated by solar system leading to security and reliability problem, but also makes theregular maximum power point tracking (MPPT) algorithm very difficult to accomplish inthis case. So it greatly reduces the conversion efficiency of PV system. Under thisbackground, the dissertation deeply researches the characteristic curves of PV arrayoperating under complicated conditions, designs and implements a novel MPPT algorithmin order to compensate the defects of traditional MPPT. So the research of the novel MPPTalgorithm has the important realistic and practical engineering application meaning.Firstly, this paper introduces several traditional MPPT control algorithms. By studing,analyzing and comprising these control algorithms, the common shortcomings existing inthese algorithms can be summarized which can’t adapt to the multi-peak P-V curve of PVarrays. It will be seen form this that it is necessary to research a novel MPPT algorithm.Therefore this paper conducts an artificial shading experiment on PV arrays operatingunder complex conditions. By observing the large number of experimental data,5important laws can be found and they are the foundation of the realization of the novelMPPT algorithm. Secondly, according to system design requirements this paper gives theoverall system design scheme and introduces the design solutions of hardware andsoftware in detail. Thirdly, the hardware circuit can be built according to the hardwaredesign scheme. DSP TMS320F28027of TI incorporated is used as the main controller. Itsinput signals are the voltage, current sampling signal from the sampling circuit and thesignal processing circuit. The main controller outputs the PWM pulse wave which runsthrough the isolating circuit, driving circuit to control the power tube on and off in theDC/DC circuit. Constant changing duty cycle of PWM wave dynamically adjustsequivalent load impedance of PV arrays in order to achieve the purpose of tracking themaximum power point. Fourthly, the novel MPPT algorithm is programmed based on CCSdevelopment environment. It mainly consists of main program, AD sampling procedures,improved perturbation&observation subroutine, global peak point tracking subroutine andtimer interrupt subroutine. Finally, it tests each module and the novel MPPT algorithm respectively and gives the necessary test resulting graphs.The test results show that hardware and software algorithm conform fully to thedesign requirements and the novel MPPT algorithm can more quickly track the globalmaximum power point than traditional algorithms. Therefore it has the great technologyreference value to the deeper research on MPPT control algorithm of PV system in thefuture.