發(fā)布時間：2018-05-25 16:30

  本文選題：直流配電網 + 運行方式��； 參考：《西安理工大學》2017年碩士論文

【摘要】：中壓直流配電網具有很大的應用前景,既能為高壓輸電向配電的發(fā)展提供并網接口,或通過AC/DC變換隔離交流輸配電系統(tǒng)的電壓跌落、為交流電網補償無功功率;又能為大容量儲能系統(tǒng)、光伏系統(tǒng)和低壓直流配電網提供并網接口,減少電壓變換環(huán)節(jié),提高系統(tǒng)可靠性。但中壓直流配電網結構復雜,存在多個端口、多個電壓等級和多種運行方式,給其電壓控制帶來了困難。如何確定合適的電壓控制策略,在中壓直流配電網多種運行方式下,保證直流母線電壓的穩(wěn)定是亟需解決的問題。本文對柔性中壓直流配電網的電壓控制進行研究,以兩端型直流配電網為研究對象,中壓直流母線通過兩側電壓源換流器(voltage source converter,VSC)與交流電網相連,通過3個基于輸入串聯(lián)輸出并聯(lián)(input-series-output-parallel,ISOP)高頻隔離雙主動全橋(dual active bridge,DAB)變換器的直流固態(tài)變壓器(DC solid state transformer,DCSST)分別為光伏系統(tǒng)、儲能系統(tǒng)和低壓直流配電網提供并網接口。首先分析了兩端直流配電網的運行方式及各接口設備在不同運行方式下的控制模式,分別設計了 VSC的功率、電壓控制器、光伏系統(tǒng)的MPPT控制器、儲能系統(tǒng)的恒功率充放電控制、定電壓控制器和DCSST的電壓電流雙閉環(huán)控制、高壓串聯(lián)側均壓控制器。其次,針對傳統(tǒng)借鑒多端直流輸電的柔性中壓直流配電網的電壓控制,無法適應柔性中壓直流配電網多種運行方式的變化,提出了改進的電壓裕度控制策略,該策略包括對主站VSC、從站VSC和次從站DCSST的控制。主站VSC采用定直流電壓控制,從站VSC作為備用站采用電壓裕度控制,正常情況下工作在定功率控制模式下,主站VSC退出運行時,具有接替主站控制系統(tǒng)中壓側電壓的能力。次從站DCSST作為備用站采用電壓裕度控制,正常情況下工作在定低壓直流電壓控制模式,電壓失控時,具有穩(wěn)定中壓直流電壓3能力,動作優(yōu)先級低于從站VSC。最后,在PSCAD/EMTDC下搭建了采用該控制策略的兩端柔性中壓直流配電網在雙端供電、單端供電、雙端隔離和孤島運行四種運行方式下的仿真模型,仿真結果表明該電壓裕度控制下的直流配電網在運行方式切換過程中,電壓能很好地保持穩(wěn)定,并降低了系統(tǒng)對于通信的依賴。
[Abstract]:The medium voltage DC distribution network has a great application prospect. It can provide grid-connected interface for the development of high voltage transmission and distribution, or isolate voltage drop of AC transmission and distribution system by AC/DC transform, and compensate reactive power for AC power network. It can also provide grid-connected interface for large capacity energy storage system, photovoltaic system and low-voltage DC distribution network, reduce voltage conversion link and improve system reliability. However, the structure of medium voltage DC distribution network is complex, there are many ports, multiple voltage levels and various operation modes, which brings difficulties to voltage control. How to determine the appropriate voltage control strategy and how to ensure the stability of DC bus voltage is an urgent problem under the operation mode of medium voltage DC distribution network. In this paper, the voltage control of the flexible medium voltage DC distribution network is studied. The middle voltage DC bus is connected to the AC network by voltage source converter. Three DC solid-state transformer DC solid state transformers-DCSSTs based on three input series output parallel series parallel active converters are used for photovoltaic system, energy storage system and low-voltage direct current distribution network respectively to provide grid-connected interface. Firstly, the operation mode of DC distribution network at both ends and the control mode of each interface device under different operation modes are analyzed. The power and voltage controllers of VSC and the MPPT controller of photovoltaic system are designed, respectively. The constant power charge and discharge control, the constant voltage controller, the voltage and current double closed loop control of DCSST, and the voltage sharing controller of the high voltage series side are presented in this paper. Secondly, in view of the traditional voltage control of flexible medium voltage DC distribution network based on multi-terminal DC transmission, which can not adapt to the variety of operation mode of flexible medium voltage DC distribution network, an improved voltage margin control strategy is proposed. The strategy includes the control of master station VSC, slave station VSC and secondary station DCSST. The main station VSC adopts the constant DC voltage control, the slave station VSC uses the voltage margin control as the backup station. Under the normal condition, the master station VSC can replace the voltage side voltage of the master station control system when it exits operation in the fixed power control mode. The secondary slave station (DCSST) uses voltage margin control as the backup station, and normally works in the constant low voltage DC voltage control mode. When the voltage is out of control, the secondary slave station has the ability of stabilizing the middle voltage DC voltage, and the priority of operation is lower than that of the slave station. Finally, the simulation model of the flexible medium voltage DC distribution network with this control strategy is built under the four operation modes of double end power supply, single end power supply, double end isolation and island operation. The simulation results show that the voltage of the DC distribution network controlled by the voltage margin can be kept stable in the switching mode and the dependence of the system on communication is reduced.
【學位授予單位】：西安理工大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TM721.1;TM714.2

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相關期刊論文 前10條

1 孫鵬飛;賀春光;邵華;劉雪飛;安佳坤;;直流配電網研究現(xiàn)狀與發(fā)展[J];電力自動化設備;2016年06期

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本文編號：1933895