【摘要】：在實(shí)現(xiàn)智能電網(wǎng)為核心的低碳能源背景下,微電網(wǎng)被認(rèn)為是降低能耗、提高電力系統(tǒng)可靠性和靈活性的智能電網(wǎng)的重要的組成部分。微電網(wǎng)實(shí)現(xiàn)其技術(shù)性、經(jīng)濟(jì)性優(yōu)勢(shì)的關(guān)鍵就是并網(wǎng)與孤島兩種模式的運(yùn)行能力。兩種運(yùn)行模式間的平滑切換是保證微電網(wǎng)持續(xù)穩(wěn)定運(yùn)行的關(guān)鍵技術(shù)。 本文針對(duì)微電網(wǎng)結(jié)構(gòu)及并網(wǎng)與孤島運(yùn)行方式的特點(diǎn),提出了一種實(shí)現(xiàn)微電網(wǎng)兩種運(yùn)行方式平滑切換的控制策略。在并網(wǎng)運(yùn)行時(shí),微電網(wǎng)內(nèi)的功率波動(dòng)由大電網(wǎng)進(jìn)行平衡,此時(shí)微電源采用PQ控制來(lái)保證輸出功率的恒定,實(shí)現(xiàn)能量管理,而儲(chǔ)能裝置則處于充電備用狀態(tài)；當(dāng)大電網(wǎng)發(fā)生故障或者主動(dòng)與微電網(wǎng)解列時(shí),孤島檢測(cè)裝置檢測(cè)到之后,微電網(wǎng)切換到孤島模式運(yùn)行,儲(chǔ)能裝置中的蓄電池采用改進(jìn)的V／f下垂控制策略,主要用來(lái)彌補(bǔ)功率缺額,實(shí)現(xiàn)能量供需平衡,同時(shí)也為系統(tǒng)提供電壓和頻率支撐,超級(jí)電容則采用恒壓恒頻的V／f控制,主要是在微電網(wǎng)兩種模式切換時(shí)快速為系統(tǒng)提供電壓和頻率支撐。其它的微電源保持PQ控制狀態(tài),用以縮短系統(tǒng)電壓和頻率的過(guò)渡時(shí)間。對(duì)于再并網(wǎng)的情況,因蓄電池有下垂控制環(huán)節(jié),微電網(wǎng)的電壓會(huì)與大電網(wǎng)電壓產(chǎn)生偏離,直接重合閘并網(wǎng)可能引起巨大的沖擊電流,因此設(shè)計(jì)增加了預(yù)同步處理單元,該單元分別采用了兩種方法進(jìn)行控制,包括直接法和間接法,間接法更能有效的較少?zèng)_擊電流,它基于三相軟件鎖相環(huán)(SPLL)來(lái)控制逆變器輸出電壓跟蹤大電網(wǎng)電壓,包括電壓幅值跟蹤和相位(頻率)同步,以降低重合閘過(guò)程的沖擊,最終實(shí)現(xiàn)微電網(wǎng)系統(tǒng)由孤島模式到并網(wǎng)模式的平滑切換。在整個(gè)過(guò)程中,充分考慮了儲(chǔ)能容量的優(yōu)化配置和可靠保護(hù),以較小的容量滿足控制目標(biāo),提高微電源的發(fā)電效率,降低燃料及污染排放水平。利用MATLAB/Simulink仿真軟件進(jìn)行建模和仿真實(shí)驗(yàn)分析,其結(jié)果驗(yàn)證了所提出平滑切換控制策略的有效性。通過(guò)對(duì)儲(chǔ)能和微電源的控制,確保微電網(wǎng)在孤島運(yùn)行、并網(wǎng)運(yùn)行、離網(wǎng)／并網(wǎng)模式切換等過(guò)程中能夠保持良好的電壓和頻率穩(wěn)定性以及微電源輸出功率的穩(wěn)定性,有效減小可再生能源發(fā)電輸出功率間歇性和隨機(jī)性等不足,從而保證了微電網(wǎng)內(nèi)敏感負(fù)荷的供電可靠性,對(duì)未來(lái)智能電網(wǎng)的發(fā)展有巨大的推動(dòng)作用。
[Abstract]:Under the background of low carbon energy with smart grid as the core, microgrid is considered to be an important part of smart grid, which can reduce energy consumption and improve the reliability and flexibility of power system. The key to realize the technicality and economic advantage of microgrid is the operation capability of grid-connected and island-connected modes. The smooth switching between the two operation modes is the key technology to ensure the continuous and stable operation of the microgrid. In this paper, according to the structure of microgrid and the characteristics of grid-connected and island-connected operation mode, a control strategy for smooth switching between two operation modes of microgrid is proposed in this paper. When connected to the grid, the power fluctuation in the micro-grid is balanced by the large power grid. At this time, the micro-power supply adopts PQ control to ensure the constant output power and realize the energy management, while the energy storage device is in the state of charging and standby. When a fault occurs in a large power grid or an active detach from the microgrid occurs, after the isolated island detection device is detected, the microgrid is switched to islanding mode, and the storage battery in the energy storage device adopts an improved control strategy of Vxf droop. It is mainly used to make up the shortage of power, realize the balance of energy supply and demand, at the same time provide voltage and frequency support for the system, and the supercapacitor is controlled by constant voltage and constant frequency. It mainly provides voltage and frequency support for the system when switching between two modes of microgrid. Other micro power supplies maintain PQ control to shorten the transition time of system voltage and frequency. In the case of regrid connection, due to the drooping control of the battery, the voltage of the microgrid will deviate from the voltage of the large grid, and the direct reclosing of the grid may result in a huge impulse current, so the pre-synchronous processing unit is added to the design. The unit adopts two kinds of control methods, including direct method and indirect method. The indirect method can effectively reduce the impact current. It is based on the three-phase software phase-locked loop (SPLL) to control the output voltage of the inverter to track the large power grid voltage. It includes voltage amplitude tracking and phase (frequency) synchronization in order to reduce the impact of reclosing process and finally realize smooth switching from island mode to grid-connected mode in microgrid system. In the whole process, the optimal configuration of energy storage capacity and reliable protection are fully considered to meet the control target with smaller capacity, improve the power generation efficiency of micro-power supply, and reduce the fuel and pollution emission level. Modeling and simulation experiments are carried out with MATLAB/Simulink simulation software, and the results show that the proposed smooth switching control strategy is effective. Through the control of energy storage and micro-power supply, the microgrid can maintain good voltage and frequency stability and output power stability in the process of island operation, grid-connected operation, off-grid / grid-connected mode switching, and so on. By effectively reducing the intermittent and random output power of renewable energy generation, the reliability of sensitive load supply in microgrid is guaranteed, and the development of smart grid in the future will be greatly promoted.
【學(xué)位授予單位】：北京交通大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TM732

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