適用於低壓直流配電系統之固態式斷路器設計與實現

Design and Implementation of Solid-State Circuit Breakers for Low Voltage DC Distribution Systems

賴俊傑(Chun-Chieh Lai)

指導教授 ： 鄭博泰

國立清華大學/電機資訊學院/電機工程學系/碩士(2009年)

摘要

隨著科技進步與經濟發展，能源與石油的需求愈來愈大，我們正面臨如何將有限的化石燃料，致力於更有效的效率，因此運用直流配電系統搭配電力電子的技術便可達到開源節流的目標。雖然現今仍以交流配電系統為多數，但直流配電系統可行性與場合有探討的必要，以資料中心對電力品質的要求為例子，為了提昇能源效率，嘗試使用直流配電系統可提昇14％ 相對於傳統的交流配電系統。直流電主要特色：高壓或是短程距離的傳輸效率高，且相同電壓程級可輕易的併入電網、沒有虛功補償的問題。此外各式各樣低壓直流的3C產品日漸成長，例如：數位電子產品、變頻驅動器，與太陽能和燃料電池等再生能源的運用，相較於交流配電系統可減少AC/DC的轉換層級。
直流系統中，斷路器主要功能可在發生接地故障時，將故障電流切除避免危害敏感性負載；若在分散式電源中可運用斷路器屏除故障的發電機，避免影響整個系統。斷路器主要可分為機械式與固態式開關：機械式斷路器的導通損失低但因為輔助控制慢所需截止的時間長，因此故障電流大，往往需要額定大或是具有消弧功能的斷路器；固態式斷路器則有動作時間快無電弧的優點，但主線路上以串聯的半導體元件當作開關，時間拉長導通損失就大，散熱問題就必須考量。
一般常見的交流斷路器，多屬於機械式的，可在零電壓或是零電流使斷路器截止；但在直流系統發展中，因為直流電壓與電流沒有自然的零交越點，導致斷路器無法啟斷故障電流或是因而產生損失。在本文中，除了介紹直流配電系統的可行性外，並探討各種直流斷路器的架構與設計準則，最後經過電腦模擬與電路實驗結果加以驗證。

關鍵字

直流配電系統 ； 固態式斷路器 ； 機械式斷路器

並列摘要

The application of DC distribution system combined with power electronic techniques is the way to solve energy issues. In addition, the amount of energy consumption in data centers is always an issue worthy to be considered. The advantage in DC power system lies on the features of transmission efficiency within low distance or high voltage. Higher transmission efficiency can be achieved due to the absence of reactive power. There are kinds of products which adopt digital electronic loads or variable-frequency motors in order to enhance the performance. Since most renewable energy generators like solar cell and fuel cell, AC/DC conversions stages can be saved while applying to DC system.
In the DC distribution grid, when grounded fault is detected at load side or distributed generation side, the DC circuit breakers should provide a fast interruption capability for the fault current and prevent the local grid from collapses. DC circuit breakers can be categorized into mechanical and solid-state types. The mechanical types have the advantages of low conduction losses, but the mechanical turn-off time is long so that the fault current is larger. For this reason the devices should be chosen at higher rating and have the capability to extinguish the occurring arc. The solid-state types have shorter turn-off time and no occurring arc. However, while a semiconductor device is used as main switch, the conduction loss is large which leads to thermal problems. The AC mechanical circuit breakers are available on the market. However, the design of circuit breakers for DC distribution system is a challenge compared with AC circuit breakers due to the absence of natural zero crossing. Therefore, in this thesis, except that the feasibility of DC distribution systems will be discussed, some topologies of DC circuit breakers in DC environment are proposed with the verification by simulation and experiment results.

並列關鍵字

DC distribution system ； Solid-state circuit breakers ； Mechanical circuit breakers

參考文獻

[1] W. Tschudi, "DC Power for Improved Data Center Efficiency," Lawrence Berkeley National Laboratory, March 2008.

[2] C. Meyer, R.W. De Doncker “Solid-state circuit breaker based on active thyristor topologies” IEEE Transactions on Power Electronics, vol.21,issue 2, pp. 450-458, March 2006.

[5] A. Pratt, P. Kumar, T. V. Aldridge, “Evaluation of 400V DC Distribution in Telco and Data Centers to Improve Energy Efficiency” , Telecommunications Energy Conference, pp. 32-39, Oct. 2007.

[6] F. Bodi, “Large-scale modeling of critical telecommunications facilities and data centers” Telecommunications Energy Conference, pp. 1-8, Sept. 2008.

[7] M. Ton et al., High Performance Buildings: DC Power for Improved Data Center Efficiency, Lawrence Berkeley National Laboratory, Dec. 2006