【摘要】：摘要：隨著分布式發(fā)電的發(fā)展,小功率光伏并網(wǎng)逆變器有著廣泛的應(yīng)用。為了起到電氣隔離,電壓變換等作用,傳統(tǒng)的光伏并網(wǎng)逆變器通常帶有工頻變壓器或高頻變壓器。但是工頻變壓器的存在使得系統(tǒng)體積增大,損耗增加,同時提高了系統(tǒng)的安裝難度；高頻變壓器的存在使得系統(tǒng)發(fā)電效率降低。去掉變壓器可以彌補(bǔ)上述缺點,因此無隔離變壓器光伏并網(wǎng)逆變器成為了當(dāng)前的研究熱點。由于光伏池板對地等效寄生電容的存在,將導(dǎo)致無隔離變壓器光伏并網(wǎng)逆變系統(tǒng)產(chǎn)生對地漏電流,危及人身安全,因此研究如何抑制甚至消除對地漏電流對其發(fā)展與應(yīng)用具有重要意義。 本文從以下五個方面對無隔離變壓器光伏并網(wǎng)逆變器展開研究： (1)介紹了無隔離變壓器光伏并網(wǎng)發(fā)電系統(tǒng)的工作原理,分析了無隔離變壓器光伏并網(wǎng)發(fā)電系統(tǒng)中對地漏電流產(chǎn)生的機(jī)理。 (2)從器件數(shù)量、濾波效果、以及系統(tǒng)損耗三個方面分析對比了多種能夠抑制系統(tǒng)對地漏電流的單相全橋無隔離變壓器光伏并網(wǎng)逆變器,并進(jìn)行仿真驗證,得出H5拓?fù)涓m合在實踐中發(fā)展。 (3)由于傳統(tǒng)雙級無隔離變壓器NPC型拓?fù)浯嬖谥悬c電位的低頻脈動,仍有對地漏電流問題。本文采用了一種新型雙級無隔離變壓器NPC型拓?fù)?相對于傳統(tǒng)NPC型拓?fù)?該拓?fù)淠軌蛲耆龑Φ芈╇娏?抑制中點電位脈動以及降低直流側(cè)電容值,通過仿真驗證了理論分析的正確性。 (4)對新型雙級無隔離變壓器NPC型拓?fù)涞目刂撇呗赃M(jìn)行了研究,前級采用單電流環(huán)控制以實現(xiàn)光伏池板的最大功率點跟蹤；后級采用直流電壓外環(huán),并網(wǎng)電流內(nèi)環(huán)的雙閉環(huán)控制,比較分析了電流內(nèi)環(huán)采用PI、PR、準(zhǔn)PR三種控制器時的優(yōu)缺點,指出了準(zhǔn)PR控制器更適合單相光伏并網(wǎng)逆變器的控制,通過仿真驗證了理論分析的正確性。 (5)搭建了5kW新型雙級無隔離變壓器NPC型光伏并網(wǎng)逆變器的實驗樣機(jī),對傳統(tǒng)NPC型拓?fù)渑c新型NPC型拓?fù)溥M(jìn)行實驗對比,對比結(jié)果驗證了新型拓?fù)涞目尚行耘c優(yōu)越性。
[Abstract]:Abstract: with the development of distributed generation, low-power photovoltaic grid-connected inverter has been widely used. Traditional photovoltaic grid-connected inverters usually have power frequency transformers or high frequency transformers for the purpose of electrical isolation and voltage conversion. However, the existence of power frequency transformer increases the volume and loss of the system, and increases the installation difficulty of the system. The existence of high-frequency transformer reduces the efficiency of power generation. Removing the transformer can make up for the above shortcomings, so the photovoltaic grid-connected inverter without isolating transformer has become a hot research topic. Because of the existence of equivalent parasitic capacitance of photovoltaic cell plate to the ground, it will lead to the generation of leakage current in the photovoltaic grid-connected inverter system without isolating transformer, which endangers the personal safety. Therefore, it is of great significance to study how to suppress or even eliminate the current of floor drain for its development and application. In this paper, the following five aspects of the photovoltaic grid-connected inverter without isolation transformer are studied: (1) the working principle of the photovoltaic grid-connected generation system without isolating transformer is introduced. The generation mechanism of floor drain current in photovoltaic grid-connected generation system without isolation transformer is analyzed. (2) from the number of devices, filtering effect, And three aspects of system loss are analyzed and compared, and the simulation results show that many single-phase full-bridge photovoltaic grid-connected inverters without isolating transformers can suppress the floor drain current. It is concluded that H5 topology is more suitable for development in practice. (3) due to the low frequency pulsation of midpoint potential in the traditional NPC topology of two-stage non-isolating transformer, there is still the problem of floor drain current. In this paper, a new two-stage unisolating transformer NPC topology is used. Compared with the traditional NPC topology, this topology can completely eliminate the floor drain current, suppress the pulsation of the midpoint potential and reduce the DC side capacitance. The correctness of the theoretical analysis is verified by simulation. (4) the control strategy of the NPC topology of a new two-stage unisolating transformer is studied. The single current loop control is used in the front stage to realize the maximum power point tracking of the photovoltaic cell plate; The back stage adopts the double closed loop control of the DC voltage outer loop and the grid-connected current inner loop. The advantages and disadvantages of the three kinds of controllers are compared and analyzed. It is pointed out that the quasi-PR controller is more suitable for single-phase photovoltaic grid-connected inverter control. The correctness of the theoretical analysis is verified by simulation. (5) the experimental prototype of NPC photovoltaic grid-connected inverter with 5kW two-stage non-isolating transformer is built, and the experimental comparison between the traditional NPC topology and the new NPC topology is carried out. The results verify the feasibility and superiority of the new topology.
【學(xué)位授予單位】：北京交通大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TM464;TM615

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