| The operating control is the core technology of microgrid research. It provides theoryreference and technical support for the microgrid applied in practical and large-scalemicrogrid access the power grid. Generally，the installed voltage level of microgrid is indistribution network. It deployed in the end of the distribution network, commonly in theremote area. It belongs to the low voltage category. The working environment istremendously bad. Therefore, the research of low voltage level of microgrid has practicalsignificance. This dissertation is finished by financial support of The National Basic ResearchProgram of China (973Program). The research covers three aspects: control of singlemicrosource, the coordinate control of multiple microsource in low voltage microgrid,thestudy of photovoltaic system on microgrid experimental platform. The major work andachievements in this dissertation are listed below.（1）The background and the study significance of the distributed power generationtechnology study is introduced.This paper summarized the microgrid concept, type, operationcharacteristics and control method, and the significance of low voltage microgrid study wereanalyzed and explained.（2）The problem of voltage ripple when photovoltaic supply is connected to power gridis considered. The structure of single-phase photovoltaic supply is carefully analysed. Underthis voltage ripple influence, the harmonic spectrum distribution rule of AC voltage side isanalysed. The direct switch state control method is proposed in the end. Because it is notaffected by the dc side capacitor voltages, the stability of the system and the control accuracyis greatly improved and has good effect.（3）To solve the problems of power couple because of difference between low voltagemicrogrid line and traditional high voltage transmission line impedance ratios, a virtual powerV/f droop control method of coordinate rotational transformation is proposed.The methodachieved the decoupled real and reactive power control through orthogonal transformationmatrix, improved voltage-frequency droop control,propsed the drooping restriction controlalgorithm、5Hz low pass filter. Furthermore，the low pass filter is designed specially，itreduce the harmonic effect and increase control accuracy effectively. The simulation andexperimental results indicated that this method can achieve the load power sharing effectivelyin the low microgrid，and the frequency and amplitude are relatively stable, the dynamiceffect is good，the project is simple，the accuracy and stability of system is enhanced.(4) A low voltage microgrid simulation platform of multiple microsource is built. This paper introduces the realization and operation principle of constant power control andconstant frequency and voltage control. Using the proposed a virtual power V/f droop controlmethod of coordinate rotational transformation and constant power control. And expounds theusing control strategy of microsource. Builds photovoltaic simulation model. Studyscoordination control effect between the multiple microsource. The simulation prove theeffectiveness of the photovoltaic simulation, the correctness of the PQ control, thecoordination between multiple microsource in various operation mode.（5）The photovoltaic system on microgrid experimental platform is developed. First,introduced the basic working principles of photovoltaic system, the DSP control systemstructure and resource allocation at the hardware circuit, peripheral sampling circuit and zerocapture circuit in detail. Then given the main program, the software interrupt service programand liquid crystal display program. Finally the experimental results prove the correctness ofthe theory research and design method.This paper discusses the control strategy of single microsource and multiple microsourceunder the environment of low voltage microgrid.Mainly because of the voltage’s secondaryripple, the direct switch state control method is proposed. According to the existing couplingproblem of the active and reactive power in low voltage microgrid, a virtual power V/f droopcontrol method of coordinate rotational transformation is proposed. The transient simulationof microgrid and experimental platform is developed. From theory to method, from method tosimulation, from simulation to experiment, The research achievements can be applied to thePV power station, intelligent distribution network, agriculture, new energy source and othersespecially occasions that the multiple group inverter is paralleled... |
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