| Electric power,as the most widely used secondary energy,is the foundation of domestic product and state construction and has the pivotal status.The power's harmonics is an important indicator to measure the power's quality,so it had been concerned very much for whole industry.For decades,more further studies of harmonics control has been done by experts and made a great achievements in theoretical study and device research,that realized the commercial of harmonic treatment device.However,as the development of distributed energy,widely use of PWM technology and the booming development of long-distance high-voltage transmission project,characteristics of power harmonic changes.The harmonic characteristics exhibit some new traits,such as the increasing of medium-high frequency harmonic content,the interactive influence of multi-type harmonics and so on.This paper based on the financial support from The National Natural Science Foundation of China.Aiming at the new view of harmonic's characteristics in grid,the connotation of the wide-band frequency harmonics,researching on harmonic generation mechanism,harmonic degradation mechanism and harmonic control mechanism are explained in detail in this paper.The logic of this paper is rigrous.The wide-band frequency harmonics' s characteristics of typical PV system have been researched.The analysis method for system parameters' s effect on harmonic degradation has been proposed.And then,the elimination method and technology of wide-band frequency harmonics have been presented.The research's fearures,the points of innovation and the useful conclusions of this paper are as follows:Taking the typical photovoltaic power generation system as the analysis object,the two-stage photovoltaic grid connected system has been selected in this article as analysis model for wide-band frequency harmonic's characteristics,and the harmonic output model has been established;Based on this ideal model,some non-ideal factors like dioxide voltage-drop,IGBT(Insulated Gate Bipolar Transistor)voltage-drop ?dead-time effects?impact of control strategy?parameters of output filter and DC side ripple voltage etc have been considered in this paper to modified the wide-band frequency harmonics model.Taking the stray parameters of typical system components into consideration,the deterioration mechanism of wide-band frequency harmonics has been thoroughly studied.The wide-band frequency harmonics model of long-distance high-voltage transmission lines has been derived.Based on that,the deterioration characteristics of current harmonics and voltage harmonics have been analyzed.The harmonic model of traditional power transformer has been presented,and the deterioration characteristics of wide-band frequency harmonics have been shown.Finally,Experimental results have validated the validity of the theoretical analysis.The parallel harmonic control device is the main way to suppress the harmonic currents in power system.A novel parallel hybrid wideband frequency harmonics control device can achieve a good suppression effect on wideband frequency harmonics when reasonable control coefficient has been selected.However,the parallel device can't suppress the harmonic voltages at all.Meanwhile,limited by the device capacity,the parallel device can't compensate the harmonic currents which produced by voltage type harmonic source.The series active power filter has an excellent suppression ability for the harmonic voltages,but it can't suppress the harmonic currents.When series device compensating the harmonic voltages which produced by current type harmonic source will output a super highly harmonic voltage to obtain the treatment effect.Considering the characteristics of the wideband frequency harmonics,such as strong randomness and multi-type interaction coupling,etc.A novel series hybrid active power filter(SHAPF),which aiming at controlling multi-types of wideband frequency harmonics,has been presented in this paper.The topology structure,working principle and compensation characteristics are analyzed.Simulation results show that it can control the wideband frequency harmonics,and suppress the harmonic resonance.Based on the analysis of the SHAPF equivalent circuit model and two types of harmonic control model,a composite control algorithm which based on double hysteresis iterative generalized integrator was proposed has been proposed to get a better tracking speed and control precision for SHAPF control algorithm.By using the classical integral separation control theory,the composite control algorithm avoid the deficiency of double hysteresis control,such as differential regulation,“dead zone”,and eliminating the disadvantage of generalized integrator's long time to get a steady state control.It means that the composite control algorithm own the advantages of the other two methods.In order to verify the advantages of compound control algorithm in tracking speed and control precision,the stability analysis and comparative studyingof the double hysteresis control method,generalized integral iterative control method and compound control method has been shown in this paper.Finally,the parameters design and prototype development of SHAPF have been carried out in this paper.The total design scheme of prototype has been presented,the optimization design methods of SHAPF's every component have been introduced detailly.Based on the design methods shown above,a prototype has been developed.The test of this prototype indicated that,this device has a good suppression result on multi-types wide-band frequency harmonics.Ant it fully meet the design requirements.The simulations,researchs and experiments done in this paper prove that the analysis methods and conclusions about deterioration of wide-band frequency harmonics are right,and prove that the main circuit design,the control strategy,the protection of software and hardware proposed in this paper are effective.The research results can provide a reference for the development and production of that device. |
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