【摘要】：可再生能源在逐年的發(fā)展,其滲透率不斷攀升,多數(shù)分布式可再生能源的利用是借助DC/AC變換器(逆變器)向電網(wǎng)輸能,在電網(wǎng)正常工況下保證其良好的動態(tài)響應及穩(wěn)定性。同步逆變器模擬了同步發(fā)電機的基本原理,設(shè)計了虛擬的轉(zhuǎn)動慣量,在不改變電網(wǎng)運行方式下,使分布式能源能友好并網(wǎng),保證了以逆變器為并網(wǎng)接口的分布式能源系統(tǒng)的可靠性和穩(wěn)定性。當電網(wǎng)電壓不平衡時,同步逆變器并網(wǎng)輸出負序電流導致線路三相電流嚴重不平衡,從而制約了其在分布式電源中的實際應用。因此,在保證逆變器并網(wǎng)輸出功率的同時,減少系統(tǒng)負序電流是同步逆變器亟待解決的問題。研究的具體工作如下:(1)虛擬同步電機在分布式能源領(lǐng)域的發(fā)展狀況以及同步逆變器控制研究現(xiàn)狀概述。對同步逆變器與電網(wǎng)同步原理和過程、并網(wǎng)后功率的調(diào)節(jié)進行了本質(zhì)分析,從而基于Simulink仿真平臺,根據(jù)同步逆變器的基本參數(shù)對其在線電壓380V電網(wǎng)電壓以及不同頻率的并網(wǎng)條件下的可行性做了驗證。提出本文的研究重點:電網(wǎng)不平衡條件下同步逆變器的并網(wǎng)控制。(2)基于二階廣義積分器分量提取的控制改進。針對分量提取控制時出現(xiàn)的頻率波動問題,采用改進的DSOGI-PLL方案對不平衡電壓提取平衡分量�；赟imulink仿真平臺,進行了在電壓幅值、相位、電壓幅值/相位分別不平衡條件下仿真驗證,確定正負序分離方案的可行性。(3)同步逆變器的正/負序控制器設(shè)計。由于傳統(tǒng)的同步逆變器數(shù)學模型在電網(wǎng)不平衡條件下存在的不足,而正負序控制算法具有解耦性,且獨立性和適應性較好。當電網(wǎng)不平衡時,在不改變逆變器正常運行機制的基礎(chǔ)上,闡述了逆變器在正負序控制器的聯(lián)合控制下的同步并網(wǎng)過程、功率的傳遞以及對系統(tǒng)負序電流的抑制策略。并在兩個控制器的聯(lián)合作用下,首先保證逆變器的友好并網(wǎng),然后分別用正序控制器和負序控制器來保持逆變器向電網(wǎng)傳送功率和對系統(tǒng)產(chǎn)生負序電流的抑制。基于Simulink仿真平臺,在不同情況的不平衡條件下進行仿真實驗。(4)150W樣機的實驗平臺搭建以及實驗驗證。利用MATLAB軟件對文中提出的控制算法進行了仿真驗證,同時以DSP控制實物逆變器,設(shè)計了150W的小功率同步逆變器并網(wǎng)系統(tǒng),完成同步逆變器在電網(wǎng)不平衡條件下的并網(wǎng)。利用該樣機對本文所提的控制策略進行了實驗驗證。
[Abstract]:With the development of renewable energy year by year, the permeability of renewable energy is increasing. Most of the distributed renewable energy sources are used to transmit energy to the power grid by means of DC/AC converters (inverters) to ensure its good dynamic response and stability under normal conditions. The synchronous inverter simulates the basic principle of synchronous generator and designs the virtual moment of inertia. The reliability and stability of distributed energy system with inverter as grid-connected interface are guaranteed. When the voltage of the power network is unbalanced, the negative sequence current output from the synchronous inverter leads to the serious imbalance of the three-phase current of the line, which restricts its practical application in the distributed generation. Therefore, while ensuring the output power of the inverter, reducing the negative sequence current of the system is an urgent problem for synchronous inverter. The research work is as follows: (1) the development of virtual synchronous motor in the field of distributed energy and the research status of synchronous inverter control are summarized. In this paper, the principle and process of synchronous inverter and power grid synchronization, and the power regulation after grid connection are analyzed in essence, which is based on Simulink simulation platform. According to the basic parameters of the synchronous inverter, the feasibility of the synchronous inverter is verified under the condition of the line voltage of 380 V grid voltage and the connection of different frequencies. The emphasis of this paper is the grid-connected control of synchronous inverter under unbalanced power system. (2) the control improvement based on the second order generalized integrator component extraction. In order to solve the problem of frequency fluctuation in component extraction control, an improved DSOGI-PLL scheme is used to extract equilibrium components from unbalanced voltages. Based on the Simulink simulation platform, the simulation is carried out under the condition of voltage amplitude, phase, voltage amplitude / phase unbalance, to determine the feasibility of the scheme of positive and negative sequence separation. (3) the design of positive / negative sequence controller for synchronous inverter. Due to the shortcomings of the traditional mathematical model of synchronous inverter under the condition of unbalanced power network, the positive and negative sequence control algorithm is decoupled and has good independence and adaptability. When the power network is unbalanced, on the basis of not changing the normal operation mechanism of the inverter, the synchronous grid-connected process of the inverter under the combined control of the positive and negative sequence controller, the transmission of power and the strategy of restraining the negative sequence current of the system are described. Under the combined action of the two controllers, the inverter can be connected in a friendly way, and then the positive sequence controller and the negative sequence controller are used to maintain the transmission power and restrain the negative sequence current of the inverter to the power grid. Based on the Simulink simulation platform, the simulation experiments are carried out under different unbalanced conditions. (4) the experimental platform of the 150W prototype and the experimental verification. The proposed control algorithm is simulated by using MATLAB software. At the same time, a 150W low power synchronous inverter grid-connected system is designed by using DSP to control the physical inverter. The synchronous inverter is grid-connected under the condition of unbalanced power grid. The proposed control strategy is verified by the prototype.
【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】：TM464

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