本文選題：光伏并網(wǎng) + 有限控制集模型預(yù)測控制�。� 參考：《山東大學(xué)》2017年碩士論文

【摘要】：隨著傳統(tǒng)能源的短缺以及環(huán)境污染日漸嚴(yán)重,可再生能源的發(fā)展和利用成為人們研究的熱點(diǎn),太陽能光伏發(fā)電即為其中最具潛力、發(fā)展迅速的清潔能源之一。隨著光伏滲透率的提高,其對電網(wǎng)造成的影響也越來越大,其中在電網(wǎng)擾動或者發(fā)生故障時,光伏系統(tǒng)突然脫網(wǎng)會給電網(wǎng)帶來嚴(yán)重后果,而低電壓穿越(low voltage ride through,LVRT)技術(shù)作為電網(wǎng)故障恢復(fù)的有力支撐也成為光伏發(fā)電發(fā)展所需解決的關(guān)鍵問題。為了保證發(fā)生電壓暫降時光伏發(fā)電仍能保持并網(wǎng),國內(nèi)外的并網(wǎng)標(biāo)準(zhǔn)中都要求大中型的光伏電站需要具有一定的低電壓穿越能力。本文首先介紹和建立了光伏電池、最大功率跟蹤(maximum power point tracking,MPPT)控制模塊、并網(wǎng)逆變器的數(shù)學(xué)模型,并在Matlab/Simulink軟件中搭建了相關(guān)部分的仿真模型。通過仿真得出了光伏電池的特征曲線以及光伏電池的最大功率跟蹤仿真結(jié)果圖,驗(yàn)證了所建模型的有效性和正確性,為光伏并網(wǎng)系統(tǒng)LVRT技術(shù)的研究提供了基礎(chǔ)。其次,研究了逆變器的有限控制集模型預(yù)測控制(finite control set-model predictive control,FCS-MPC)。通過分析FCS-MPC算法的基本原理,建立三相并網(wǎng)逆變器FCS-MPC的模型。該算法在每個采樣周期,由逆變器的數(shù)學(xué)模型和系統(tǒng)的狀態(tài)信息,預(yù)測將來一段時間所有開關(guān)狀態(tài)所對應(yīng)的控制變量以及系統(tǒng)輸出,并由價值函數(shù)選出讓系統(tǒng)性能最佳的開關(guān)狀態(tài)作用到逆變器,預(yù)先對系統(tǒng)誤差進(jìn)行修正以取得期望的性能。此控制方法具有簡單易理解、無需調(diào)制器、內(nèi)部完全解耦和動態(tài)響應(yīng)快等優(yōu)點(diǎn)。通過仿真驗(yàn)證,該控制可以實(shí)現(xiàn)單位功率因數(shù)運(yùn)行,使得輸出電流跟電網(wǎng)電壓頻率相位均相同,能夠滿足并網(wǎng)要求。最后,針對光伏并網(wǎng)的低電壓穿越問題,本文提出了基于FCS-MPC的LVRT控制策略。介紹了國內(nèi)外的低電壓穿越標(biāo)準(zhǔn);分析了電網(wǎng)故障期間并網(wǎng)逆變器的運(yùn)行特性,闡述了電網(wǎng)故障對光伏并網(wǎng)發(fā)電系統(tǒng)的影響,為低電壓穿越控制提供了理論基礎(chǔ);并通過仿真驗(yàn)證了采用的dq鎖相環(huán)電壓暫降檢測方法可以準(zhǔn)確、迅速地檢測到三相對稱電壓暫降,為低電壓穿越控制的動作提供依據(jù)。當(dāng)電網(wǎng)故障引起并網(wǎng)點(diǎn)電壓暫降時,光伏電池不再使用MPPT控制,轉(zhuǎn)換為一種參考功率跟蹤控制模式,減小光伏電池輸送到逆變器的有功功率;逆變器在有限控制集模型預(yù)測控制的基礎(chǔ)上采取一種擁有無功補(bǔ)償?shù)目刂撇呗?通過重新調(diào)整有功電流和無功電流參考值,限制逆變器過電流,且給電網(wǎng)輸出定量的無功支撐并網(wǎng)點(diǎn)電壓的恢復(fù)。仿真結(jié)果表明,當(dāng)并網(wǎng)點(diǎn)發(fā)生電壓暫降時,所采用的LVRT控制策略,可以抑制直流側(cè)母線電壓的升高,限制逆變器輸出電流的增大,為電網(wǎng)電壓的恢復(fù)輸出一定的無功功率,實(shí)現(xiàn)了低電壓穿越。
[Abstract]:With the shortage of traditional energy and the increasingly serious environmental pollution, the development and utilization of renewable energy has become a hot topic. Solar photovoltaic power generation is one of the most potential and rapidly developing clean energy. With the increase of photovoltaic permeability, the influence of photovoltaic system on the power network is becoming more and more serious. When the grid is disturbed or broken, the photovoltaic system will bring serious consequences to the power network. Low voltage traversing voltage ride through LVRTT technology as a powerful support for power grid fault recovery has become a key problem for the development of photovoltaic power generation. In order to ensure that photovoltaic generation can still be connected to the grid when voltage sag occurs large and medium-sized photovoltaic power plants are required to have a certain low voltage traversing capacity in the grid-connected standards at home and abroad. This paper first introduces and establishes the control module of photovoltaic cell, maximum power point tracking module, and the mathematical model of grid-connected inverter, and builds the simulation model of related parts in Matlab/Simulink software. The characteristic curve of photovoltaic cell and the simulation diagram of maximum power tracking of photovoltaic cell are obtained by simulation, which verify the validity and correctness of the model, and provide the foundation for the research of LVRT technology in photovoltaic grid-connected system. Secondly, finite control set-model predictive control (FCS-MPC) is studied. By analyzing the basic principle of FCS-MPC algorithm, the FCS-MPC model of three-phase grid-connected inverter is established. In each sampling period, the control variables corresponding to all switching states and the system output are predicted by the mathematical model of the inverter and the system state information. According to the value function, the switching state with the best system performance is selected for the inverter, and the system error is corrected in advance to obtain the desired performance. This control method has the advantages of simple and easy to understand, no modulator, complete internal decoupling and fast dynamic response. The simulation results show that the control can realize the operation of unit power factor and make the output current equal to the frequency phase of the grid voltage and can meet the requirements of grid connection. Finally, a LVRT control strategy based on FCS-MPC is proposed to solve the low voltage traversing problem of photovoltaic grid-connected system. This paper introduces the low voltage traversing standards at home and abroad, analyzes the operation characteristics of grid-connected inverters during power grid failure, and expounds the influence of grid faults on photovoltaic grid-connected generation system, which provides a theoretical basis for low-voltage traversing control. The simulation results show that the DQ phase-locked loop voltage sag detection method can accurately and rapidly detect the three-phase symmetrical voltage sag, which provides the basis for the low-voltage traversing control. When the grid fault is caused and the node voltage is temporarily dropped, the photovoltaic cell is no longer controlled by MPPT and converted into a reference power tracking control mode to reduce the active power of the photovoltaic cell to the inverter. Based on the finite control set model predictive control, the inverter adopts a control strategy with reactive power compensation. By adjusting the reference value of active current and reactive current, the inverter overcurrent is limited. And to the grid output quantitative reactive power support and network voltage recovery. The simulation results show that the LVRT control strategy can restrain the rise of DC bus voltage, limit the increase of inverter output current, and output a certain reactive power for the restoration of grid voltage. Low voltage traversing is realized.
【學(xué)位授予單位】：山東大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TM615

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