汽電共生廠系統分析與卸載策略制定

Cogeneration System Analysis and Load Shedding Scheme

鄧為元(Wei-Ynan Deng)

指導教授 ： 李清吟

國立臺北科技大學/電資學院/電機工程系 優質電力產業研發專班/碩士(2008年)

https://doi.org/10.6841/NTUT.2008.00591

摘要

近年來隨著科技與經濟發展，民生用電與工業用電需求量大增，新設立火力電廠常會因為環境影響評估通過困難、土地取得不易及周遭居民抗爭等造成阻礙。因此採用各種分散式電源（Distributed Generation）併聯在配電系統上，可以有效降低線路損失並提升供電品質。常選擇在電力負載集中區域設置汽電共生發電系統（Cogeneration System）解決區域缺電情況，此系統特點係將剩餘熱能再利用，可減少線路損失與降低環境污染。汽電共生系統為保持較佳之供電品質常與原有配電系統併聯，在電力公司故障發生時，汽電共生系統必須維持單獨且適時的提供電力來維持廠內重要負載。此時若廠內電力系統無法達到電能平衡，往往需要透過卸載機制，讓過多的負載由系統切離，使系統回到平衡。
本文採用 Electrical Transient Analysis Program （ETAP）電力系統分析軟體，計算汽電共生廠電力系統的負載潮流、故障電流及進行暫態穩定度分析。在電力公司電力系統發生故障時，汽電共生廠與電力公司需進行解聯排除故障，且解聯前屬於購電模式時，可能造成汽電共生廠電能不平衡，若無正確的卸載策略，將使汽電共生系統頻率與電壓持續下降，將造成發電機組的保護電驛跳脫，會讓整個汽電共生廠區皆為停電的情況，若建立良好的卸載策略可防止此情況發生。
在制定卸載策略上，經由執行暫態穩定度分析，來建立汽電共生廠解聯後的卸載策略，本文使用的卸載策略以固定頻率低頻電驛建構，具有卸載動作簡單、成本低及可靠度高之優點。在考慮汽電共生廠發電機運轉效率，經負載潮流計算各種可能運轉於購電模式之情況，若此時進行解聯將造成多少電量的不足，再配合卸載段數的設定、電驛的頻率與時間設定，經重複進行暫態穩定度分析，並考量各負載的供電優先權順序，制定可靠的卸載策略。在經過各種情況的暫態穩定度模擬後，本文制定的卸載策略皆可讓系統回復至安全運轉頻率。

關鍵字

汽電共生系統 ； 電力潮流分析 ； 故障電流分析 ； 暫態穩定度 ； 卸載策略

並列摘要

Due to the technology and economic increased in recent years, electricity consumption of the general and the industrial had huge increased. But, the impact estimate of environment, hard to get the new plant address and the complaint from the people who live around the thermal plant that cause new thermal plant installed very difficult. For these previous reasons, the various distributed generation are connected to the distribution system that is another way to solve the problem, and the benefit is not only reduce the loss of the line but also increase the power quality. Usually, installed the cogeneration system in the area of collected electricity load can solve the problem of the area of less electricity. The characteristic of the system is reusing remain heat, reduce the loss of the line and reduce the pollution to the environment. For the better power quality is provided from the cogeneration system, it’s usually connected to the distribution system. When the faults occur in the utility, cogeneration system not only should be maintain operation alone but also provide the electricity that maintain the important loads in factory. If the electricity balance can not be provided by the power system in factory in this moment, it usually uses the load shedding scheme to cut the over loads in the system, and then let the system back to the balance condition.
The analysis program used in this thesis is Electrical Transient Analysis Program （ETAP）, and it calculate the power flow and short current in the power system in the cogeneration factory, it also implement the analysis of transient stability. When the faults occur in the utility, the fault eliminated by cogeneration system decouple with the utility. Before decoupling, it’s in the purchase mode and maybe causes the electricity unbalance in the cogeneration factory. The frequency and voltage of cogeneration system will keep decreasing if there use the incorrect load shedding scheme, also cause the protect relay of the generator tripping, and then all the area of the cogeneration factory will in the blackout condition. These conditions can be avoided by the correct load shedding scheme.
When the load shedding scheme is establishing, build the load shedding scheme after decoupling of cogeneration factory that through transient stability implemented. The load shedding scheme is used in this thesis that build by low-frequency relay. The advantages of this relay are motion simply, low cost and high reliability. When considerate the operational efficiency of cogeneration factory, through calculate power flow that various conditions of operating in purchase mode, and get how the not enough value of electricity if decoupling cause in this moment. Also in this condition, handle with the step of the load shedding, frequency of relay and set up of time. And then through analyze of the transient stability again and again. After the step previous, considerate the sequence of the loads and establish the reliable load shedding scheme. After simulating all conditions of the transient stability, the load shedding scheme is established that let system can back to the safety operational frequency in this thesis.

並列關鍵字

cogeneration system ； power flow analysis ； fault current analysis ； transient stability ； load shedding scheme

參考文獻

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