發(fā)布時間：2017-12-26 19:41

  本文關(guān)鍵詞：混合雙饋入直流輸電系統(tǒng)中電壓源和電流源換流器相互作用規(guī)律研究　出處：《華北電力大學(北京)》2017年博士論文　論文類型：學位論文

  更多相關(guān)文章： 混合雙饋入直流輸電系統(tǒng) 換相失敗 小信號模型 運行阻抗 有效短路比 LCC新型拓撲

【摘要】：隨著基于電網(wǎng)換相換流器型高壓直流輸電(Line comuutated coverter based high voltage direct current,LCC-HVDC)在輸電領(lǐng)域的廣泛應(yīng)用和基于電壓源換流器的高壓直流輸電技術(shù)(Voltage Source Converter based HVDC,VSC-HVDC)的快速發(fā)展,含有LCC和VSC的混合多饋入直流輸電系統(tǒng)近年來受到了廣泛的關(guān)注。研究混合多饋入直流輸電系統(tǒng)中LCC-HVDC和VSC-HVDC的相互作用規(guī)律,具有重要的理論和工程意義。混合雙饋入直流輸電系統(tǒng)作為混合多饋入直流系統(tǒng)的基礎(chǔ),其基本特性和運行規(guī)律對混合多饋入系統(tǒng)的研究具有重要的借鑒意義。論文圍繞混合雙饋入直流輸電系統(tǒng)中VSC-HVDC和LCC-HVDC的相互影響關(guān)系,通過研究系統(tǒng)的穩(wěn)態(tài)和暫態(tài)運行特性,從混合雙饋入直流輸電系統(tǒng)的小信號建模和穩(wěn)定性分析、等值有效短路比的定量評估方法、換相失敗抵御能力和故障后功率恢復特性等三方面對混合雙饋入系統(tǒng)中LCC-HVDC和VSC-HVDC的相互作用規(guī)律開展了相關(guān)研究,并得到了一系列具有工程指導意義的結(jié)論。(1)混合雙饋入直流輸電系統(tǒng)的數(shù)學模型和控制策略為了研究混合雙饋入系統(tǒng)中LCC-HVDC和VSC-HVDC的相互作用規(guī)律,首先分別研究了LCC-HVDC和VSC-HVDC的基本結(jié)構(gòu),推導了包括換流器交直流電壓轉(zhuǎn)換關(guān)系、功率傳輸特性等在內(nèi)的數(shù)學模型,分析了兩種不同類型直流輸電系統(tǒng)的常用控制方式。然后研究了混合多饋入直流輸電系統(tǒng)的典型拓撲結(jié)構(gòu)和控制策略,基于混合雙饋入直流輸電系統(tǒng),研究了LCC-HVDC不同的控制方式組合、VSC-HVDC不同的有功控制方式對LCC-HVDC換相失敗和故障后功率恢復特性的影響規(guī)律。分析結(jié)果表明,LCC-HVDC的控制方式會在一定程度上影響其換相失敗和故障后功率恢復特性,而VSC-HVDC的有功控制方式對LCC-HVDC的換相失敗和故障恢復特性影響很小。最后選取了LCC-HVDC整流側(cè)定直流電流、逆變側(cè)定關(guān)斷角,VSC-HVDC整流側(cè)定直流電壓、逆變側(cè)定直流功率作為后續(xù)研究的基本控制策略。(2)混合雙饋入直流輸電系統(tǒng)的小信號穩(wěn)定性分析小信號穩(wěn)定性分析是揭示混合雙饋入系統(tǒng)中VSC-HVDC和LCC-HVDC相互作用規(guī)律的重要研究手段。首先基于交直流側(cè)功率守恒原理,推導了LCC和VSC換流器在dq坐標系下的線性化模型,結(jié)合換流站中PLL、控制系統(tǒng)、濾波器等主要基本單元的數(shù)學模型,分別推導了LCC換流站和VSC換流站的小信號模型。然后以各個換流站為子系統(tǒng),研究了直流輸電系統(tǒng)直流側(cè)和交流側(cè)接口模型以及不同坐標系下變量的轉(zhuǎn)換模型,提出了混合雙饋入直流輸電系統(tǒng)的小信號模型建立方法。基于混合雙饋入直流輸電系統(tǒng),將建立的小信號模型和PSCAD/EMTDC中的仿真模型進行了對比,驗證了建立的小信號模型的正確性。在此基礎(chǔ)上,基于建立的小信號模型,重點針對交流系統(tǒng)強度、VSC-HVDC傳輸功率、LCC-HVDC傳輸功率等條件變化時系統(tǒng)的小信號穩(wěn)定性問題,通過特征根分析和參與因子分析方法,研究了混合雙饋入系統(tǒng)在交流系統(tǒng)強度變化時的主導振蕩模態(tài)及其主要參與狀態(tài)變量。研究結(jié)果表明上述變化條件下LCC和VSC的狀態(tài)變量在主導振蕩模態(tài)中的參與度相似,說明在系統(tǒng)因交流系統(tǒng)強度減弱而失去穩(wěn)定的過程中VSC-HVDC和LCC-HVDC存在顯著的相互作用關(guān)系。最后,計算了上述變化條件下混合雙饋入系統(tǒng)的有效短路比,結(jié)果表明傳統(tǒng)有效短路比評價指標對混合雙饋入直流輸電系統(tǒng)的強度僅具有定性的指導作用,在定量評價方面,該評價指標有待進一步改進和完善。(3)基于運行阻抗的混合雙饋入系統(tǒng)等值有效短路比定量評估方法為了將傳統(tǒng)有效短路比指標擴展應(yīng)用到混合雙饋入系統(tǒng)的交流系統(tǒng)強度定量評估中,揭示LCC-HVDC和VSC-HVDC交流系統(tǒng)強度的相互作用規(guī)律,提出了換流器運行阻抗和基于運行阻抗的混合雙饋入系統(tǒng)等值有效短路比(impedance based effective short circurt ratio,IESCR)的概念。首先基于建立的小信號模型,通過在系統(tǒng)穩(wěn)態(tài)運行點施加特定小擾動的方法,獲得換流器交流側(cè)的端口特性,通過分析端口電壓電流偏移量的數(shù)學關(guān)系,得到了換流器的基頻等效阻抗計算方法。該等效阻抗與系統(tǒng)的運行點相關(guān),故在論文中稱之為換流器的運行阻抗。在既定運行狀態(tài)下,將目標換流器(LCC或VSC)以外的其他換流器等效為運行阻抗,然后通過與交流網(wǎng)絡(luò)的等值,提出了基于運行阻抗的混合雙饋入直流輸電系統(tǒng)等值有效短路比的定量評估方法,并通過仿真研究驗證了該評估方法的有效性�；贗ESCR,研究了混合雙饋入系統(tǒng)中LCC-HVDC和VSC-HVDC交流系統(tǒng)強度的相互作用規(guī)律,研究發(fā)現(xiàn),LCC-HVDC的交流系統(tǒng)強度受到VSC控制方式、功率等級以及VSC與LCC的電氣距離等因素的影響,LCC-HVDC對VSC-HVDC的交流系統(tǒng)強度也有類似的作用規(guī)律。最后,結(jié)合建立的小信號模型,研究了控制器參數(shù)對直流系統(tǒng)能穩(wěn)定傳輸額定功率所需的最小IESCR的影響規(guī)律,研究發(fā)現(xiàn)混合雙饋入系統(tǒng)中定關(guān)斷角控制器及換流器鎖相環(huán)的控制參數(shù)對該最小IESCR有顯著的影響,在控制參數(shù)相對較小的條件下,系統(tǒng)更容易在接近臨近短路比的條件下傳輸額定有功功率。(4)混合雙饋入直流輸電系統(tǒng)中LCC-HVDC的換相失敗和故障恢復特性為了研究混合雙饋入系統(tǒng)中VSC-HVDC對LCC-HVDC換相失敗和故障恢復特性的作用規(guī)律,首先研究了VSC控制方式、VSC控制器參數(shù)以及VSC和LCC間電氣距離不同對LCC-HVDC的換相失敗抵御能力和故障后有功功率恢復速度的影響。研究結(jié)果表明,當VSC-HVDC采用定交流電壓控制方式時,相比定無功功率控制,能更好地改善LCC-HVDC的換相特性,尤其在LCC和VSC間電氣距離較小、VSC定交流電壓控制器響應(yīng)速度較快的條件下,改善效果更加明顯。然后通過研究換相過程中VSC的無功功率變化規(guī)律以及LCC的換相電壓、換相電流等的變化過程,得到了VSC-HVDC改善LCC-HVDC換相特性的基本原理。同時研究發(fā)現(xiàn),通過這種利用VSC在交流側(cè)和LCC并聯(lián)的方式改變LCC換相電壓的方式受到VSC和LCC間電氣距離、VSC控制器響應(yīng)速度等因素的限制。為了充分發(fā)揮VSC電壓源的特性,提出了一種LCC的新型拓撲,該拓撲采用子模塊與LCC閥臂串聯(lián)的方式直接改變LCC的換相電壓。通過仿真研究發(fā)現(xiàn),所提出的LCC新型拓撲能夠進一步增強混合雙饋入直流輸電系統(tǒng)的換相失敗抵御能力,同時加快其故障后功率恢復速度。
[Abstract]:Based on the power grid with commutation Converter Based HVDC (Line comuutated coverter based high voltage direct current, LCC-HVDC) is widely used in the field of power transmission and voltage source converter based HVDC (Voltage Source Converter based HVDC, VSC-HVDC) the rapid development of hybrid multi infeed HVDC system with LCC and VSC has received extensive attention in recent years. It is of great theoretical and engineering significance to study the interaction between LCC-HVDC and VSC-HVDC in hybrid multi infeed HVDC transmission system. Hybrid dual infeed HVDC transmission system is the foundation of hybrid multi infeed DC system. Its basic characteristics and operation rules are of great significance for the study of hybrid multi infeed system. The interaction of the mixture of VSC-HVDC and LCC-HVDC in dual infeed HVDC systems, through the study of the system steady-state and transient operation characteristics, from analysis, small signal modeling and stability of hybrid dual infeed HVDC system equivalent effective short circuit ratio, quantitative evaluation method of commutation failure resilience and fault recovery characteristics after power three to carry out the research on interaction of mixed LCC-HVDC and VSC-HVDC double feed system, and get a series of useful conclusions. (1) the mathematical model and control strategy of hybrid dual infeed HVDC systems in order to study on the interactions between LCC-HVDC and VSC-HVDC hybrid dual infeed system, we study the basic structure of LCC-HVDC and VSC-HVDC, the mathematical model including the converter DC voltage conversion relationship, power transmission characteristics, the analysis is deduced. The common control mode of two different types of HVDC system. And then study the typical topology structure and control strategy of hybrid multi infeed HVDC systems, hybrid dual infeed HVDC system based on the effects of different combinations of control modes of LCC-HVDC and VSC-HVDC with different active control mode of LCC-HVDC commutation failure and fault recovery characteristics of power. The analysis results show that the control mode of LCC-HVDC will affect the power recovery characteristics of commutation failure and fault after a certain extent, while the active power control mode of VSC-HVDC has little effect on the commutation failure and fault recovery characteristics of LCC-HVDC. Finally, LCC-HVDC rectifier side fixed DC current, inverter side turn off angle, VSC-HVDC rectifier side fixed DC voltage and inverter side DC power are selected as the basic control strategy for subsequent research. (2) small signal stability analysis of hybrid dual infeed HVDC transmission system. Small signal stability analysis is an important research method to reveal the interaction rule between VSC-HVDC and LCC-HVDC in hybrid dual infeed system. Based on the principle of AC and DC power conservation, the linear model of LCC and VSC converter in the DQ coordinates is deduced according to the mathematical model of PLL control system in converter station, and filters the main basic unit, the small signal model of LCC converter and VSC converter are derived respectively. Then, taking the converter stations as subsystems, the DC side and AC side interface models of HVDC transmission system and the transformation models of variables under different coordinate systems are studied, and a small signal modeling method for the hybrid dual infeed HVDC transmission system is proposed. Based on the hybrid dual infeed HVDC transmission system, the small signal model established in this paper is compared with the simulation model in PSCAD/EMTDC, and the correctness of the established small signal model is verified. On this basis, the small signal model is established based on the small signal stability problems and changes in the strength of AC system and VSC-HVDC power transmission, LCC-HVDC transmission power condition is the focus of the system, through the analysis of the characteristic roots and participation factor analysis method of the mixed double fed into the dominant oscillation mode changes in the strength of AC system when the system and its main in the state variable. The results show that the participation of LCC and VSC in the dominant oscillation modes is similar under the above changing conditions, indicating that there is a significant interaction between VSC-HVDC and LCC-HVDC in the process of instability due to the weakening of the strength of the AC system. Finally, the effective short mixed double feed system under the condition of the change ratio was calculated, the results show that the traditional effective short circuit ratio guidance has only qualitative evaluation index of the mixed double infeed HVDC system strength, in the quantitative evaluation, the evaluation index should be further improved and perfected. (3) based on the equivalent effective short-circuit impedance of double infeed system than to the traditional quantitative evaluation method is effective short circuit ratio applied to AC system strength index of quantitative assessment of hybrid dual infeed system, LCC-HVDC and VSC-HVDC reveal the strength of AC system interaction rules, put forward converter operation impedance and equivalent effective short mixed double infeed system operation based on the impedance ratio (impedance based effective short circurt ratio, IESCR) concept. First, based on the small signal model established, the port characteristic of the converter's AC side is obtained by applying a small perturbation method to the steady-state operation point of the system. By analyzing the mathematical relationship between the voltage and current offset of the port, the fundamental frequency equivalent impedance calculation method of the converter is obtained. The equivalent impedance is related to the operating point of the system, so it is called the running impedance of the converter in this paper. In the given operating conditions, the target converter (LCC or VSC) other than the converter equivalent to running resistance, and then with the communication network equivalent, put forward the operating impedance of the hybrid dual infeed HVDC system equivalent effective short-circuit ratio method based on quantitative assessment, and effectiveness of the evaluation method. The simulation results show. Based on IESCR, the interaction law of the intensity of LCC-HVDC and VSC-HVDC AC system in a hybrid double feed system is studied. It is found that the communication system of LCC-HVDC is strong.
【學位授予單位】：華北電力大學(北京)
【學位級別】：博士
【學位授予年份】：2017
【分類號】：TM721.1

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