本文關鍵詞：三相非隔離三電平并網逆變器的研究　出處：《揚州大學》2014年碩士論文　論文類型：學位論文

  更多相關文章： 非隔離 三相三電平 光伏并網發(fā)電 空間矢量調制 漏電流

【摘要】：隨著社會的發(fā)展、科技的進步、能源需求量的增大和化石能源的日益短缺,開發(fā)使用新能源已成為當今社會的主題。太陽能以其獨特的優(yōu)勢,扮演著越來越重要的角色,而光伏并網發(fā)電作為太陽能利用的一種形式,已成為研究和應用的熱點。光伏并網發(fā)電系統(tǒng)中能量轉換的核心裝置是逆變器,它的成本和效率是整個光伏發(fā)電系統(tǒng)的關鍵。因此,開發(fā)低成本、高效率的光伏并網逆變器是各國研究人員追求的目標。 本文對NPC-I型三相三電平并網逆變器和NPC-T型三相三電平并網逆變器的原理進行了詳細分析,并給出了中點鉗位(Neutral Point Clamped, NPC)T型三相三電平主電路的控制方法。論文詳細研究了空間矢量調制策略(Space Vector Pulse Width Modulation, SVPWM),給出了SVPWM算法的實施步驟。通過仿真研究了改進型三平SVPWM與傳統(tǒng)三電平SVPWM算法下主電路的共模特性,仿真結果表明改進型SVPWM調制策略能有效抑制電路的共模漏電流。但在軟起動實驗中,改進型SVPWM算法會導致橋臂中點電壓畸變,主要原因是為了抑制電路的共模漏電流,該調制方法沒有采用冗余小矢量,故在起動過程中,當調制比較小時,小矢量的作用導致了橋臂中點的電壓畸變,針對這種情況本文提出了一種基于十二扇區(qū)的SVPWM調制策略,由于這種調制方法沒有使用小矢量,故解決了軟起動過程中橋臂中點電壓出現(xiàn)的畸變問題,同時本文提出的十二扇區(qū)SVPWM調制策略可有效的抑制共模漏電流。 本文針對NPC-I型和NPC-T型三相三電平電路拓撲,詳細分析了這兩種電路拓撲的動態(tài)換流過程,在此基礎上歸納總結了各種換流模態(tài)下開關器件的損耗情況,然后在NPC-I型和NPC-T型三相三電平電路中通過采用相同的開關器件,對NPC-I型和NPC-T型三相三電平電路進行了損耗分析,結果表明對于本文設計的功率等級和選用的開關頻率而言,NPC-T型三相三電平電路的效率優(yōu)于NPC-I型三相三電平電路。 本文在仿真的基礎上研制了一臺17KW非隔離NPC-T型三相三電平并網逆變器樣機。對NPC-T型三相三電平并網逆變器的硬件進行了設計并給出了主要參數的計算方法,給出了輸出濾波器的詳細設計過程,開關器件的選型依據和直流側電容的選取方法。最后給出了NPC-T型三相三電平并網逆變器的實驗和仿真波形,繪制并對比了NPC-I型和NPC-T型三相三電平并網逆變器的效率曲線。仿真和實驗驗證了本文提出的調制策略和設計方法的有效性。
[Abstract]:With the development of society, the progress of science and technology, the increase of energy demand and the increasing shortage of fossil energy, the development and use of new energy has become the theme of today's society. Solar energy has its unique advantages. Photovoltaic grid-connected generation, as a form of solar energy utilization, has become a research and application hotspot. Inverter is the core device of energy conversion in photovoltaic grid-connected generation system. Its cost and efficiency are the key of the whole photovoltaic power generation system. Therefore, developing low-cost and high-efficiency photovoltaic grid-connected inverter is the goal pursued by researchers all over the world. In this paper, the principle of NPC-I three-level grid-connected inverter and NPC-T three-level grid-connected inverter are analyzed in detail. Neutral Point Clamped is given. The control method of NPC)T three-phase three-level main circuit. The space vector modulation strategy is studied in detail in this paper. Space Vector Pulse Width Modulation. The implementation steps of the SVPWM algorithm are given. The common mode characteristics of the main circuit under the improved three-level SVPWM algorithm and the traditional three-level SVPWM algorithm are studied by simulation. Simulation results show that the improved SVPWM modulation strategy can effectively suppress the common mode leakage current of the circuit, but in the soft start experiment, the improved SVPWM algorithm will lead to the midpoint voltage distortion of the bridge arm. The main reason is that in order to suppress the common mode leakage current of the circuit, the modulation method does not use redundant small vectors, so in the starting process, when the modulation comparison is small, the effect of the small vector leads to the voltage distortion in the midpoint of the bridge arm. In this paper, a SVPWM modulation strategy based on sector 12 is proposed. Because this modulation method does not use small vectors, it solves the distortion of the midpoint voltage of the bridge arm during soft start. At the same time, the 12 sector SVPWM modulation strategy proposed in this paper can effectively suppress the common mode leakage current. In this paper, the dynamic commutation process of NPC-I and NPC-T three-phase three-level circuit topologies is analyzed in detail. On this basis, the losses of switching devices in various commutation modes are summarized, and then the same switching devices are used in NPC-I and NPC-T three-phase three-level circuits. The loss analysis of NPC-I and NPC-T three-phase three-level circuits is carried out. The results show that the power level and switching frequency of the designed circuit are discussed in this paper. The efficiency of NPC-T type three-phase three-level circuit is better than that of NPC-I three-phase three-level circuit. In this paper, a 17KW unisolated NPC-T three-phase three-level grid-connected inverter prototype is developed on the basis of simulation. The hardware design of NPC-T three-level three-level grid-connected inverter is presented. The calculation method of main parameters. The detailed design process of output filter, the selection basis of switching device and the selection method of DC side capacitance are given. Finally, the experimental and simulation waveforms of NPC-T three-phase three-level grid-connected inverter are given. The efficiency curves of NPC-I and NPC-T three-phase three-level grid-connected inverters are drawn and compared. The effectiveness of the proposed modulation strategy and design method is verified by simulation and experiments.
【學位授予單位】：揚州大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：TM464

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