【摘要】：級聯(lián)H橋型多電平動態(tài)電壓恢復(fù)器(Dynamic voltage Restorer,DVR)串聯(lián)在電網(wǎng)和負載之間,可以短時間內(nèi)消除電壓跌落、三相電壓不平衡和短暫斷電等電能質(zhì)量問題,是解決電壓質(zhì)量問題公認的最有效措施。然而,級聯(lián)H橋型多電平DVR在實現(xiàn)補償功能時直流側(cè)電壓存在波動,且當級聯(lián)數(shù)較多時,其數(shù)字化實現(xiàn)困難。為此本文以級聯(lián)H橋型多電平DVR為研究對象,對逆變器與電網(wǎng)功率的流動、級聯(lián)H橋逆變器的調(diào)制策略以及DVR的補償策略進行了研究。具體內(nèi)容如下:本文詳細的分析了級聯(lián)H橋型多電平DVR的拓撲結(jié)構(gòu)及原理,建立了DVR的數(shù)學模型;在理論上分析了DVR逆變器與電網(wǎng)功率流動的關(guān)系,分析表明DVR補償電壓時,逆變單元輸出的有功功率和電壓幅度與電網(wǎng)電壓波動程度、負載功率因數(shù)以及DVR輸出電壓、電網(wǎng)電壓、補償負載電壓三者的相位關(guān)系等有直接關(guān)系。本文通過串聯(lián)變壓器實現(xiàn)DVR與電網(wǎng)的耦合,詳細分析了串聯(lián)在線路中變壓器存在勵磁涌流的基本原理,給出了抑制變壓器勵磁涌流的措施。對目前已有的基于瞬時無功功率理論的dq變換法、基于雙dq解耦變換的電壓檢測法以及單相電壓跌落檢測法進行了總結(jié)。詳細分析了同相電壓補償策略、完全電壓補償策略以及最小能力補償策略各補償策略的優(yōu)缺點以及適應(yīng)的應(yīng)用場合�；谪摵呻娏飨嗔糠治龅腄VR補償策略與實際情況不符合、三相不平衡時分析困難、物理意義不清晰的缺點,以負荷電壓向量為基礎(chǔ),對負荷電壓相量與電壓補償?shù)年P(guān)系進行了詳細的分析,提出了基于負荷電壓向量分析的級聯(lián)H橋多電平DVR補償策略。概述了載波垂直移相(CLS-SPWM)和載波水平移相(CPS-SPWM)的基本原理,對比分析了CLS-SPWM以及CPS-SPWM調(diào)制策略,針對CPS-SPWM調(diào)制策略在數(shù)字化實現(xiàn)上的困難并結(jié)合二重化SPWM調(diào)制策略的優(yōu)勢,提出了二重化CPS-SPWM調(diào)制策略,給出了二重化CPS-SPWM調(diào)制策略的具體調(diào)制方式�；诙鼗疌PS-SPWM調(diào)制策略下電平丟失現(xiàn)象,詳細分析了調(diào)制比與電平數(shù)目的關(guān)系,得到了級聯(lián)H橋多電平DVR輸出最大電平數(shù)時調(diào)制比的關(guān)系,更進一步,分析得出了調(diào)制比下電平數(shù)對應(yīng)的關(guān)系。搭建了應(yīng)用于10k V系統(tǒng)的PACAD/EMTDC10k V仿真模型,對DVR補償功能、電平數(shù)與調(diào)制比關(guān)系進行了驗證,仿真結(jié)果驗證了理論分析的正確性。
[Abstract]:Cascaded H-bridge multilevel dynamic voltage restorer (Dynamic voltage Restorer,DVR) is in series between power grid and load, which can eliminate power quality problems such as voltage drop, three-phase voltage imbalance and transient power outage in a short time. It is the most effective measure to solve the voltage quality problem. However, the DC side voltage of cascaded H-bridge multilevel DVR is fluctuating when the compensation function is realized, and when the number of cascades is large, it is difficult to realize digitalization. In this paper, the power flow of cascaded H-bridge multilevel DVR, the modulation strategy of cascaded H-bridge inverter and the compensation strategy of DVR are studied. The main contents are as follows: the topology and principle of cascaded H-bridge multilevel DVR are analyzed in detail, and the mathematical model of DVR is established. The relationship between DVR inverter and power flow is analyzed theoretically, and it is shown that when DVR compensates the voltage, the output active power and voltage amplitude of the inverter unit and the voltage fluctuation degree, load power factor and DVR output voltage of the inverter unit are correlated with the voltage fluctuation degree of the power grid, the load power factor and the output voltage of DVR. The phase relationship of grid voltage and compensating load voltage is directly related. In this paper, the coupling of DVR and power network is realized by series transformer. The basic principle of the inrush current of transformer in series is analyzed in detail, and the measures to restrain the inrush current of transformer are given. The existing dq transform method based on instantaneous reactive power theory, voltage detection method based on double dq decoupling transform and single-phase voltage drop detection method are summarized. In this paper, the advantages and disadvantages of the compensation strategies of in-phase voltage compensation, complete voltage compensation and minimum capacity compensation are analyzed in detail. The DVR compensation strategy based on load current phasor analysis is not in accordance with the actual situation, and it is difficult to analyze when the three-phase unbalance and the physical meaning is not clear. It is based on the load voltage vector. The relationship between load voltage phasor and voltage compensation is analyzed in detail. A cascade H bridge multilevel DVR compensation strategy based on load voltage vector analysis is proposed. The basic principles of carrier vertical phase shift (CLS-SPWM) and carrier horizontal phase shift (CPS-SPWM) are summarized, and the modulation strategies of CLS-SPWM and CPS-SPWM are compared and analyzed. In view of the difficulty of digital implementation of CPS-SPWM modulation strategy and the advantages of dual SPWM modulation strategy, the dual CPS-SPWM modulation strategy is proposed, and the specific modulation mode of double CPS-SPWM modulation strategy is given. Based on the phenomenon of level loss under dual CPS-SPWM modulation strategy, the relationship between modulation ratio and the number of levels is analyzed in detail, and the relation of modulation ratio when the output maximum level number of cascaded H-bridge multilevel DVR is obtained. The relation of the level number at the modulation ratio is obtained. The simulation model of PACAD/EMTDC10k V applied to 10kV system is built. The function of DVR compensation, the relation between the level number and modulation ratio are verified. The simulation results verify the correctness of the theoretical analysis.
【學位授予單位】：湘潭大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TM761.12

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