發(fā)布時(shí)間：2019-04-16 16:54

【摘要】：隨著光伏產(chǎn)業(yè)的不斷升級(jí),現(xiàn)今市場(chǎng)光伏逆變器的容量不斷增大,光伏發(fā)電的占比逐漸增加,其安全性和可靠性受到越來(lái)越多的關(guān)注。其中,光伏逆變器的低電壓穿越(LVRT)能力是考察一臺(tái)機(jī)器好壞的重要性能指標(biāo),三相鎖相環(huán)的精度以及并網(wǎng)和低電壓穿越控制算法的好壞將直接影響到逆變器能否按照要求完成穿越任務(wù)。本文以實(shí)際項(xiàng)目為背景,針對(duì)傳統(tǒng)三相鎖相環(huán)在精度和抗干擾能力方面的不足,提出了一種改進(jìn)的控制方法,并依托有源箝位三電平逆變器拓?fù)浜偷蛪捍┰綄?shí)驗(yàn),驗(yàn)證提出理論的可靠性。論文采用有源箝位三電平電路作為逆變器主拓?fù)?分析了它的換流路徑和調(diào)制策略。針對(duì)三電平逆變器固有的中點(diǎn)電位不平衡問題設(shè)計(jì)了一種控制方法,研究了不同開關(guān)矢量對(duì)中點(diǎn)電位的影響程度,利用注入零序參考電流控制中點(diǎn)電位的波動(dòng),并通過仿真驗(yàn)證算法的有效性。分析了基于同步坐標(biāo)系鎖相環(huán)(SRF-PLL)和基于雙廣義二階積分器鎖相環(huán)(DSOGI-PLL)的結(jié)構(gòu)特點(diǎn)和應(yīng)用環(huán)境,針對(duì)工程中常用的DSOGI-PLL鎖相環(huán)在電網(wǎng)頻率發(fā)生波動(dòng)時(shí)易出現(xiàn)鎖相精度降低的問題提出了一種改進(jìn)方法,通過固定角頻率輸入和輸出幅值補(bǔ)償提升輸出正交信號(hào)精度,減小頻率波動(dòng)。最后通過仿真比較了電網(wǎng)在各類跌落狀態(tài)下三種鎖相環(huán)的輸出特性�；谀孀兤鞯臄�(shù)學(xué)模型分別討論了光伏逆變器在電網(wǎng)穩(wěn)態(tài)和故障狀態(tài)下的并網(wǎng)控制策略。按照逆變器低壓穿越要求設(shè)計(jì)了一種基于無(wú)功功率支撐的穿越策略,在電壓跌落時(shí)根據(jù)跌落深度設(shè)置不同的參考電流,詳細(xì)分析了穿越過程中的控制邏輯,最后通過仿真對(duì)理論分析進(jìn)行驗(yàn)證。搭建了1 MW實(shí)驗(yàn)平臺(tái),設(shè)計(jì)了樣機(jī)主拓?fù)淦骷䥇?shù)、部分硬件電路和軟件流程圖。在不同的工況下對(duì)光伏逆變器的輸入輸出特性和低壓穿越能力進(jìn)行了測(cè)試,分析了實(shí)驗(yàn)結(jié)果,驗(yàn)證了所提理論的有效性。
[Abstract]:With the continuous upgrading of PV industry, the capacity of PV inverter is increasing and the proportion of PV power generation is increasing, so the safety and reliability of PV inverter have been paid more and more attention. Among them, the low voltage traversing (LVRT) capability of photovoltaic inverter is an important performance index to investigate the quality of a machine. The accuracy of the three-phase-locked loop and the grid-connected and low-voltage traversal control algorithms will directly affect whether the inverter can complete the traversing task according to the requirements. In this paper, an improved control method is proposed to improve the accuracy and anti-jamming ability of the traditional three-phase-locked loop, which is based on the active clamp three-level inverter topology and the low-voltage traversal experiment, which is based on the actual project and the traditional three-phase-locked loop. The reliability of the proposed theory is verified. The active clamped three-level circuit is used as the main topology of the inverter, and its commutation path and modulation strategy are analyzed. Aiming at the inherent midpoint potential imbalance problem of three-level inverter, a control method is designed. The influence of different switching vectors on the midpoint potential is studied, and the fluctuation of the midpoint potential is controlled by injecting zero sequence reference current. The validity of the algorithm is verified by simulation. The structure characteristics and application environment of phase-locked loop (SRF-PLL) based on synchronous coordinate system and phase-locked loop (DSOGI-PLL) based on double generalized second-order integrator are analyzed. An improved method is proposed to improve the accuracy of DSOGI-PLL phase locked loop when the frequency fluctuates in the power network. The accuracy of the output orthogonal signal is improved by compensation of the input and output amplitude of the fixed angle frequency, and the accuracy of the output orthogonal signal is improved by using the fixed angle frequency input and output amplitude compensation. Reduce the frequency fluctuation. Finally, the output characteristics of three kinds of PLL under various sags are compared by simulation. Based on the mathematical model of inverter, the grid-connected control strategy of photovoltaic inverter under steady-state and fault-state is discussed respectively. According to the requirements of inverter low voltage traversal, a traversal strategy based on reactive power support is designed. When voltage sags, different reference currents are set according to the depth of sag, and the control logic in the process of traversing is analyzed in detail. Finally, the theoretical analysis is verified by simulation. The experiment platform of 1 MW is built, and the parameters of the main topology device, some hardware circuits and software flowchart of the prototype are designed. The input-output characteristics and low-voltage traversal ability of photovoltaic inverter are tested under different operating conditions, and the experimental results are analyzed to verify the effectiveness of the proposed theory.
【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TM464

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