【摘要】：能源緊缺與環(huán)境污染形勢(shì)不容樂觀,大力發(fā)展光伏逆變技術(shù)是緩解危機(jī)的有效途徑之一。目前中小型容量的單相光伏逆變器廣泛使用鎖相環(huán)或鎖頻環(huán)實(shí)現(xiàn)并網(wǎng)同步控制,但在實(shí)際電網(wǎng)中上述方法均存在跟蹤誤差較大導(dǎo)致逆變器功率因數(shù)變低的問題。另外,現(xiàn)有研究發(fā)現(xiàn)光伏逆變器在強(qiáng)電網(wǎng)下易達(dá)到穩(wěn)定狀態(tài),而在弱電網(wǎng)下具有易失穩(wěn)的現(xiàn)象,帶來逆變器退出運(yùn)行的嚴(yán)重后果。為解決光伏逆變器存在的上述問題,在雙閉環(huán)控制的基礎(chǔ)上,提出了使用鎖相環(huán)和鎖頻環(huán)復(fù)合并網(wǎng)同步技術(shù)來提高跟蹤精度改善逆變器功率因數(shù)的方法,理論分析了光伏逆變器獨(dú)立使用鎖相環(huán)或鎖頻環(huán)在同步控制過程中存在的優(yōu)缺點(diǎn),基于Matlab/simulink軟件平臺(tái),分別搭建了在電網(wǎng)電壓幅值跌落、頻率和相角突變及諧波含量突增四種情況下的仿真模型,仿真對(duì)比研究了傳統(tǒng)同步控制與復(fù)合控制方式在電網(wǎng)電壓不穩(wěn)定時(shí)對(duì)光伏逆變器輸出特性的影響。針對(duì)弱電網(wǎng)下光伏逆變器易失穩(wěn)的問題,提出在復(fù)合并網(wǎng)同步技術(shù)的基礎(chǔ)上添加電壓前饋控制策略提高逆變器輸出阻抗的方法,構(gòu)建了逆變器電流內(nèi)環(huán)控制的結(jié)構(gòu)框圖,分析了逆變器輸出阻抗與并網(wǎng)線路阻抗對(duì)逆變器在弱電網(wǎng)下運(yùn)行穩(wěn)定性的影響,研究了逆變器輸出阻抗擾動(dòng)成分的穩(wěn)定性,搭建強(qiáng)弱電網(wǎng)切換下的仿真模型,對(duì)比分析了改變輸出阻抗前后的并網(wǎng)效果,驗(yàn)證了對(duì)弱電網(wǎng)下增強(qiáng)光伏逆變器運(yùn)行的穩(wěn)定性的重要作用。得出了提高逆變器輸出阻抗有利于增強(qiáng)逆變器在弱電網(wǎng)下的穩(wěn)定性的結(jié)論。仿真結(jié)果表明:本文提出的基于復(fù)合并網(wǎng)同步技術(shù)的電壓前饋控制策略,能夠解決實(shí)際電網(wǎng)中跟蹤誤差較大和弱電網(wǎng)下具有易失穩(wěn)的問題,避免逆變器功率因數(shù)變低和被迫退出運(yùn)行的后果。
[Abstract]:The situation of energy shortage and environmental pollution is not optimistic. Developing photovoltaic inverter technology is one of the effective ways to alleviate the crisis. At present phase-locked loop or frequency locked loop is widely used in single-phase photovoltaic inverter with medium and small capacity to realize grid-connected synchronous control. However, in actual power grid, the tracking error is large and the power factor of inverter becomes lower. In addition, it is found that the photovoltaic inverter is easy to achieve stability under the strong grid, but unstable under the weak grid, which leads to the serious consequences of the inverter out of operation. In order to solve the above problems of photovoltaic inverter, based on the double closed loop control, a method of improving the tracking accuracy and improving the power factor of inverter by using PLL and FLOL combined grid-connected synchronization technology is proposed. The advantages and disadvantages of phase-locked loop (PLL) or frequency-locked loop (FL) in the synchronous control process of photovoltaic inverter are analyzed theoretically. Based on the Matlab/simulink software platform, the voltage amplitude drop in the power grid is built separately. The simulation model of frequency and phase angle mutation and harmonic increase is studied. The effects of traditional synchronous control and composite control on the output characteristics of photovoltaic inverter under the condition of voltage instability are compared. Aiming at the instability of photovoltaic inverter under weak grid, this paper proposes a method to increase the output impedance of inverter by adding voltage feedforward control strategy on the basis of combined grid-connected synchronization technology, and constructs the structure block diagram of inverter current inner loop control. The influence of inverter output impedance and grid-connected line impedance on the operation stability of inverter under weak grid is analyzed. The stability of the disturbance component of inverter output impedance is studied, and the simulation model of strong and weak power grid switching is built. The effect of grid connection before and after changing the output impedance is compared and analyzed, which verifies the important role of enhancing the stability of photovoltaic inverter under weak grid. It is concluded that increasing the output impedance of the inverter is beneficial to enhance the stability of the inverter under the weak grid. The simulation results show that the proposed voltage feedforward control strategy based on composite grid-connected synchronization technology can solve the problems of large tracking error and instability under weak electric network. Avoid the consequences of lower power factor and forced exit from operation of the inverter.
【學(xué)位授予單位】：新疆大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TM464;TM615

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本文編號(hào)：2419415