Unified Control Strategy Of PV Inverter Mixed Power Quality Control

The clean, safe, convenient and eiffcient photovoltaic grid-connected generationhas been focused by countries all around the world under the background that theproblems of global energy shortage and environmental pollution have becomeincreasingly prominent in recent years. However, because of being restricted by a seriesof objective conditions, such as weather change, the alternation of day-night, lowerenergy density of solar energy, poor system stability and so on, the practical andeffective utilization of photovoltaic grid-connected system is very low. At the same time,all kinds of nonlinear, impulse and unbalanced electric equipments are widelyused in all walks of life with the development of industrialization process. These loadsconsume reactive power and produce harmonic, result in very bad pollution to the grid，lower the power quality. But the requirements for power quality of modern highsophisticated loads such as IT, medical, and microelectronic are getting higher andhigher. The traditional passive iflter equipments have already appeared to be inadequate,under the background above, the research on APF is also important.In view of the above problems, this article compares and analyses photovoltaicgrid-connected system and APF respectively from the system structure, control methodand use function three aspects, proves the main technologies related in theories andexperiments, and ifnds that there are many similarities between them. Thereafter, it isfeasible to combine power quality optimization and photovoltaic grid-connectedtechnology together and implement uniifed control to them. Based on these, thegrid-connected photovoltaic system and APF are chosen to be the research object.Several appropriate expansions are taken in the hardware structure and software controlmethod. Make it have the functions of generating electricity, harmonics suppression andreactive power compensation, realize the fusion of grid-connected photovoltaic systemand APF. The system not only extends the functions of the previous system, improvesthe utilization of the external equipments, saves extra hardware investments ofconifguring APF separately, but also provides a bran-new viable idea and a beneifcialattempt to the power quality control of the distributed photovoltaic system.The paper analyzes the current development status of the photovoltaic technologyand shortcomings, points out the purpose and signiifcance of the topic in this article.This article analyzes the basic structures and working principles of grid-connectedphotovoltaic system and APF, and builds a mathematic model. In the current detectionsection, this article uses ip-iq based on instantaneous reactive power to detect andisolate the active> reactive and harmonic these objective factors. For how to implement each of the current component of the integrated control, this paper presentscontrolling-table this novel control ideas which can adjust the proportion of the reactiveand harmonic current compensation dynamically to compensate reactive power andharmonic of the grid effectively, realize automatic selection of the best model. Take fulladvantage of the capacity of grid-connected photovoltaic system, and improve theutilization of the external equipments.Finally, the model and simulation is implemented under the environment ofMATLAB/simulink in this article, and demonstrates the effectiveness of this uniifedcontrol strategy, and the effects are signiifcant.