本文關鍵詞：光伏并網(wǎng)系統(tǒng)低電壓穿越控制方法的研究　出處：《東北電力大學》2017年碩士論文　論文類型：學位論文

  更多相關文章： 低電壓穿越 并網(wǎng)逆變器 降階諧振調節(jié)器 UHCM模塊 最大電流幅值

【摘要】：近些年隨著化石能源的大量消耗,環(huán)境污染問題日益嚴重,為了解決資源枯竭和環(huán)境污染問題需要大量開發(fā)和利用可再生能源。在諸多類型的新能源中光伏發(fā)電具有利用成本低、效率高、無污染等優(yōu)點,是目前最重要的新能源之一。但是對太陽能的開發(fā)利用的研究目前還存在很多問題,這些問題制約著光伏并網(wǎng)發(fā)電的大規(guī)模應用。低電壓穿越技術不僅要求在系統(tǒng)正常運行時保證光伏系統(tǒng)輸出的電能質量,同時在系統(tǒng)出現(xiàn)一定程度的故障時保持光伏組件持續(xù)向電網(wǎng)輸出,同時充分利用光伏逆變器的快速無功輸出能力,在故障穿越期間為系統(tǒng)提供一定的無功,協(xié)助電網(wǎng)電壓恢復正常。本文是從光伏系統(tǒng)的網(wǎng)端角度進行了故障穿越控制策略的研究,目前光伏系統(tǒng)在故障穿越過程中在進行正負序分離控制時會有一定的誤差,針對這一問題本文研究了一種降階的諧振調節(jié)器(ReducedResonanceOrder,ROR),該控制器的功能就是將控制過程中的二階諧振環(huán)節(jié)降階為兩個不同極性的一階濾波器環(huán)節(jié),一階復數(shù)濾波器可以克服二階諧振環(huán)節(jié)對正負序分量無選擇的缺點。為了使控制器在光伏并網(wǎng)系統(tǒng)軟件和硬件固有誤差范圍內發(fā)揮更好的效果,本文引入了截止頻率來增大ROR控制器的頻帶寬度。并應用博德圖(Bode)來分析所研究的控制器中截止頻率效果及系統(tǒng)的最優(yōu)性能。搭建光伏并網(wǎng)系統(tǒng)的仿真模型,以此來驗證本文應用的ROR調節(jié)器可提高光伏系統(tǒng)在故障穿越過程中基波的正負序分離的速度。在分析傳統(tǒng)PLL-SRF(同步參考坐標系鎖相環(huán))工作原理和小信號模型的基礎上,根據(jù)系統(tǒng)穩(wěn)態(tài)及動態(tài)響應設計了合適的鎖相環(huán)參數(shù);針對電網(wǎng)電壓不平衡且諧波畸變下PLL-SRF檢測的基波正序分量中含有負序和諧波分量而致使其不能工作的問題,提出了基于不平衡諧波補償機制(Mechanismon Compensati Harmonic Unbalanced,UHCM)模塊的三相鎖相環(huán),并擴展研究了通過濾波結構并聯(lián)的方式消除低次諧波對鎖相環(huán)的影響。在光伏并網(wǎng)系統(tǒng)數(shù)學模型建立的基礎上,對并網(wǎng)故障穿越特別是不對稱故障下的并網(wǎng)控制原理給出了合理的數(shù)學分析,并計算得出了傳統(tǒng)故障穿越電流控制目標。通過仿真驗證發(fā)現(xiàn)傳統(tǒng)的控制策略存在算法復雜、控制目標對平衡短路電流和短路功率的能力有限以及直流側母線電壓控制不合理等缺點。針對傳統(tǒng)故障穿越控制策略的缺陷本文提出了最大電流幅值控制策略,并結合所研究的正負序分量分離技術,通過仿真驗證所提控制方法可以在電壓跌落期間能夠穩(wěn)定光伏系統(tǒng)交流以及直流側的電壓水平,在故障期間為電網(wǎng)提供一定量的無功支撐,幫助系統(tǒng)電壓逐步恢復正常。
[Abstract]:In recent years, with the consumption of fossil energy, the problem of environmental pollution is becoming more and more serious. In order to solve the problem of resource depletion and environmental pollution, a large number of renewable energy sources need to be developed and utilized. Photovoltaic power generation has the advantages of low cost, high efficiency and no pollution in many kinds of new energy sources. It is one of the most important new energy sources, but there are still many problems in the research of solar energy development and utilization. These problems restrict the large-scale application of grid-connected photovoltaic power generation. Low-voltage traversing technology not only requires to ensure the power quality of photovoltaic system output in the normal operation of the system. At the same time, keep the photovoltaic module out to the power grid continuously when there is a certain degree of fault, and make full use of the fast reactive power output ability of the photovoltaic inverter, and provide a certain reactive power for the system during the period of fault passing. In this paper, the fault crossing control strategy is studied from the point of view of the grid end of the photovoltaic system. At present, there will be some errors in the control of positive and negative sequence separation in the fault passing process of photovoltaic system. In this paper, we study a reduced order resonant regulator called reduced Resonance order order (ROR). The function of the controller is to reduce the order of the second order resonance in the control process to the first order filter with two different polarities. The first-order complex filter can overcome the disadvantage that the second-order resonant link has no choice for the positive and negative sequence components. In order to make the controller play a better effect in the inherent error range of the software and hardware of the photovoltaic grid-connected system. In this paper, cutoff frequency is introduced to increase the bandwidth of ROR controller. To analyze the cutoff frequency effect of the controller and the optimal performance of the system. Build the photovoltaic grid-connected system simulation model. It is verified that the ROR regulator in this paper can improve the speed of the positive and negative sequence separation of the fundamental wave in the process of fault passing through the photovoltaic system. In the analysis of the traditional PLL-SRF (synchronous reference coordinate system phase-locked loop). Working principle and small signal model based on. Appropriate PLL parameters are designed according to the steady and dynamic responses of the system. In order to solve the problem that the fundamental sequence component of PLL-SRF detected under unbalanced voltage and harmonic distortion has negative sequence and harmonic component, it can not work. Based on unbalanced harmonic compensation mechanism, mechanismon Compensati Harmonic Unbalanced is proposed. The three-phase phase-locked loop of UHCM module is studied. The influence of low-order harmonics on phase-locked loop is eliminated by parallel filter structure. The mathematical model of photovoltaic grid-connected system is established. Reasonable mathematical analysis of grid-connected control principle for grid-connected fault traversing, especially under asymmetric fault is given. The traditional fault traversing current control target is calculated and the simulation results show that the traditional control strategy has complex algorithm. The control target has limited ability to balance short circuit current and short circuit power, and the DC bus voltage control is unreasonable. Aiming at the defects of traditional fault crossing control strategy, a maximum current amplitude control strategy is proposed in this paper. Combined with the research on the separation of positive and negative sequence components, the simulation results show that the proposed control method can stabilize the voltage level of AC and DC side of PV system during voltage sag. It provides a certain amount of reactive power support to the power network during the fault period, and helps the system voltage to return to normal step by step.
【學位授予單位】：東北電力大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TM615

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