【摘要】：離網(wǎng)運(yùn)行的直流微電網(wǎng)運(yùn)行控制簡單,安裝地點(diǎn)靈活,且在大電網(wǎng)故障時(shí)可保證重要負(fù)荷可靠供電。本文針對離網(wǎng)運(yùn)行的光儲(chǔ)直流微電網(wǎng),采用直流母線電壓(DBS)分層控制策略實(shí)現(xiàn)多源協(xié)調(diào)、能量自主管理以及直流母線電壓穩(wěn)定等目標(biāo)。分析DBS分層控制下直流微電網(wǎng)的小信號(hào)穩(wěn)定性并探討其影響因素,采用無源阻尼法提高直流微電網(wǎng)的穩(wěn)定性。具體內(nèi)容如下:首先,設(shè)計(jì)DBS分層控制策略,根據(jù)母線電壓將光儲(chǔ)直流微電網(wǎng)運(yùn)行狀態(tài)分為3種工作模式:模式1時(shí)輕載,母線電壓較高,光伏單元下垂控制以限制功率輸出并維持母線電壓穩(wěn)定,同時(shí)蓄電池單元限流充電吸收多余功率并防止蓄電池過充;模式2時(shí)負(fù)載增加,母線電壓降低,光伏單元采用最大功率點(diǎn)跟蹤(MPPT)控制實(shí)現(xiàn)最大功率輸出,同時(shí)蓄電池單元下垂充電以補(bǔ)充剩余能量并維持母線電壓穩(wěn)定;模式3時(shí)重載,母線電壓較低,光伏單元MPPT控制輸出最大功率,同時(shí)蓄電池單元下垂放電補(bǔ)充不足的功率需求并維持母線電壓穩(wěn)定。仿真和實(shí)驗(yàn)驗(yàn)證了在DBS分層控制下直流微電網(wǎng)可以實(shí)現(xiàn)在3種工作模式的穩(wěn)定運(yùn)行和模式間平滑切換。其次,多變換器并聯(lián)交互所引起的穩(wěn)定性問題是直流微電網(wǎng)領(lǐng)域的一個(gè)研究熱點(diǎn)。DBS分層控制下的直流微電網(wǎng)是一個(gè)多點(diǎn)平衡系統(tǒng),目前單一控制模式的穩(wěn)定性分析不適用于該控制策略下的直流微電網(wǎng)。本文在確定光儲(chǔ)直流微電網(wǎng)架構(gòu)及DBS分層控制策略的基礎(chǔ)上建立了各單元在不同控制模式下的小信號(hào)模型,推導(dǎo)出各接口變換器的閉環(huán)阻抗表達(dá)式,并得出直流微電網(wǎng)分別運(yùn)行在3種工作模式的等效阻抗模型。利用幅值-相角裕量(GMPM)阻抗比禁止區(qū)判據(jù),判定得出直流微電網(wǎng)在3種工作模式均可保證小信號(hào)穩(wěn)定。最后,針對直流微電網(wǎng)運(yùn)行在模式2時(shí),負(fù)載總阻抗中存在的負(fù)諧振尖峰不利于穩(wěn)定的問題,采用無源阻尼法,通過增加阻尼電路來削減諧振尖峰,改善負(fù)載阻抗特性,使直流微電網(wǎng)穩(wěn)定性得到提高,同時(shí)分析了濾波參數(shù)對穩(wěn)定性的影響以指導(dǎo)濾波器的設(shè)計(jì)。仿真結(jié)果表明無源阻尼法可降低母線電壓、負(fù)載電流紋波,提高直流微電網(wǎng)的穩(wěn)定性及負(fù)載供電質(zhì)量。
[Abstract]:The off-grid DC microgrid has the advantages of simple operation control, flexible installation location and reliable power supply for important loads in the event of large power grid failures. In this paper, the multi-source coordination, independent energy management and DC bus voltage stability are realized by using DC bus voltage (DBS) layered control strategy for off-grid optical storage DC microgrid. The small signal stability of DC microgrid controlled by DBS is analyzed and the influencing factors are discussed. The passive damping method is used to improve the stability of DC microgrid. The main contents are as follows: firstly, the DBS hierarchical control strategy is designed. According to the bus voltage, the operation state of the optical storage DC microgrid is divided into three working modes: mode 1, light load, high bus voltage, Photovoltaic unit droop control to limit power output and maintain bus voltage stability, while battery unit current limiting charge to absorb excess power and prevent battery overcharge; Mode 2 load increases, bus voltage decreases, photovoltaic unit uses maximum power point tracking (MPPT) control to achieve maximum power output, while battery unit sagging charging to replenish residual energy and maintain bus voltage stability; Mode 3 heavy load, low bus voltage, photovoltaic unit MPPT control output maximum power, while battery unit sag discharge to supplement the insufficient power demand and maintain bus voltage stability. Simulation and experiments show that DC microgrid can operate stably in three operation modes and smooth switch between modes under DBS layered control. Secondly, the stability problem caused by the parallel interaction of multi-converters is a hot topic in the field of DC microgrid. The DC microgrid based on DBS hierarchical control is a multi-point balancing system. At present, the stability analysis of single control mode is not suitable for DC microgrid with this control strategy. Based on the structure of optical storage DC microgrid and the layered control strategy of DBS, the small signal model of each unit in different control modes is established, and the closed-loop impedance expression of each interface converter is deduced. The equivalent impedance model of DC microgrid operating in three working modes is obtained. By using the criterion of (GMPM) impedance ratio of amplitude-phase margin, it is determined that the stability of small signal can be guaranteed in three operation modes of DC microgrid. Finally, aiming at the problem that the negative resonance peak in the load total impedance is not stable when the DC microgrid operates in mode 2, the passive damping method is adopted to reduce the resonant peak and improve the load impedance characteristic by adding damping circuit. The stability of DC microgrid is improved and the influence of filter parameters on the stability is analyzed to guide the design of the filter. The simulation results show that the passive damping method can reduce the bus voltage, load current ripple, improve the stability of DC microgrid and the quality of load supply.
【學(xué)位授予單位】：西安理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TM727

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