無功補(bǔ)償畢業(yè)設(shè)計外文翻譯.docx

文獻(xiàn)翻譯英文原文：Issues for reactive power and voltage control pricing in aderegulated environmentAbstractIssues related to reactive power, voltage support and transmission losses as dictated from a certain class of electric loads are addressed. Specifically, the impact of predominantly induction motor loads on voltage support, reactive power requirements, and transmission losses is examined. These issues are examined with a model, which explicitly models the induction motor mechanical load. Simulation results on a simplified electric power system are presented. Based on these results, a pricing structure for voltage and reactive power support is proposed. The basic assumption of the paper is that, in a deregulated environment, the expense of the incremental requirements for voltage control should be charged to the member causing the additional requirements. The results of this work can also be used to justify long-term pricing agreements between suppliers and customers. Keywords: Reactive power; Induction motor loads; Voltage support; Reactive power pricing1. IntroductionVoltage control in an electric power system is important for many reasons: _a. all end-use equipmentneed near-nominal voltage for their proper operation, _b. near-nominal voltage results in near-minimum transmission losses, and _c. near-nominal voltages increase the ability of the system to with-stand disturbances _security. A reasonable voltage profile throughout an electric power system is associated with the ability of the system to transfer power from one location to another. When the voltage sags to low values, this ability of the system is compromised. The onset of power transfer inability can be detected with sensitivity analysis of reactive power requirements vs. real power load increases. This sensitivity is dependent on the characteristics of the electric load. Such sensitivity analyses have been performed using various electric load models, i.e. constant power load, constant impedance load, or combination of the two _voltage-dependent load. The majority of electric loads are induction motors. These loads do not fit into any of the load model categories mentioned. Yet, they drastically affect the stability of the electric power system. In this paper, we assert the need to model induction motor loads within the power flow formulation and directly evaluate the effects of such loads on reactive power requirements. It is shown that the power flow formulation can be augmented to include the specific induction motor loads. Interesting nonlinear phenomena occur when the voltage at induction motor loads sags to low values. These phenomena affect the performance of the transmission system. In a deregulated environment, it makes sense to examine these phenomena and design a pricing model based on the economic impact of these phenomena. The paper is organized as follows: first, a formulation is proposed, which explicitly models the induction motors. This formulation is introduced as an extension to the usual power flow problem. Then, a sensitivity analysis procedure is introduced. This sensitivity is based on an extension of the co-state method. The proposed methods are applied to a simplified system comprising induction motor loads. The results of this system are discussed. A pricing approach for voltage support and reactive power requirements is presented.4. Example resultsThe application of the model presented in this paper is demonstrated on a simple electric power system, consisting of a generating substation, step-up transformer, a transmission line, step-down transformerand several induction motors. The system is illustrated in Fig. 2. The parameters of the system have been selected to represent typical systems and they are shown in Table 1. It is important to realize that the motors may or may not be controlled by variable voltage-variable frequency drives. For this system, we performed parametric studies of the voltage level, the reactive power requirement, and the transmission losses. The variable parameter is the total induction motor load. This parameter is denotedwith the variable y in Table 1. Also note that the model requires the mechanical load torque, T m . The assumed mechanical torque is listed in Table 1.Fig. 3 illustrates the variation of the voltage magnitude and the generating unit reactive power outputas the total induction motor load increases. Note that, when the induction motor load increases beyond the value of 0.90 p.u., the reactive power requirement increase and the voltage magnitude decreases below 0.9 p.u. When the load increases beyond the value of 1.2 p.u., the voltage collapses. What happens in this case is that the induction motor moves to an operating point of very high slip, in this case, ss0.27, absorbs higher reactive power and causes the termi-nal voltage to dip _voltage collapse. Note that the voltage collapse is abrupt and unexpected. It is important to observe that this behavior of the proposed Fig. 4. model is realistic and quite different from simplified models such as constant power or constant impedance load models. The performance of the system in the presence of induction motor loads can be better understood by studying the sensitivity of voltage magnitude, reactive power requirements and transmission losses vs. induction motor load. Figs. 46 illustrate these sensitivities as functions of total induction motor rated load. In Fig. 4, it is apparent that the sensitivity of the voltage magnitude becomes very high as the electric motor load approaches 1.2 p.u. It would be expedient to impose operating limits using the sensitivity of voltage magnitude. For example, if one is to apply limits to this sensitivity, i.e. 20%, then it is apparent that for this system, the induction motor load should not be more than 0.8 p.u. of the system rated power. Similarly, one can observe in Figs. 5 and 6 that the sensitivity of reactive power requirements and transmission losses increase drastically as the induction motor load increases. It is important to note that when the induction motor load is 0.8 p.u., the sensitivity of reactive power to rated load is 1.0, i.e. any additional 1 MW of load will require 1 MVA of generated reactive power. When the induction motor load becomes 1.0 p.u., the sensitivity becomes 1.58 MVA /MW. Similarly, the transmission loss sensitivity with respect to load increases drastically as the induction motor load reaches 1.0 p.u. For example, when the load is 1.0 p.u., the incremental losses become 4%, a relatively high value.Figs. 46 illustrate that at the point before the voltage collapse, the sensitivities become very high. Specifically, the voltage sensitivity is y1.0, the reactive power sensitivity is 3.8 MVA rMW and the transmission loss sensitivity is 0.094. This data can be used in two ways. First, application of limits onsystem sensitivities will ensure that the system never operates near the point of voltage collapse. Second, the sensitivities can provide the basis for setting tariffs for voltage support and reactive power of predominantly induction motor loads. The basis of the tariff structure and its implementation is discussed in Section 5. One can argue that these tariffs may be applied to all loads for simplicity.The results in Figs. 36 were obtained for a specific system. The same information can be obtained for any system using the proposed model. Then this information can be utilized to impose tariffs for loads that are predominantly induction motors. 5. Tariff structureThe basis of the tariff structure is the cost of providing voltage and reactive power support subject to acceptable system performance. Acceptable system performance can be established by imposing limits to the sensitivities of voltage magnitude and reactive power requirements. These limits are system dependent and should be decided upon extensive studies of the system. The same studies will providethe range of sensitivities of voltage magnitude, reactive power requirements and transmission losses. Adirect cost can be associated with the transmission losses. An investment cost can also be associatedwith reactive power requirements. Let x be the average transmission loss sensitivity and z be the maximum reactive power sensitivity. Then the cost of providing these services is:C=p1 x+p2 z，where p1 is the price of electric energy, and p2 is the investment cost of reactive power sources.Note that the investment cost must be computed on the basis of the maximum requirements throughoutthe study period. The cost C provides the basis for establishing the actual tariffs. It is also important to note that, today, technology exists to monitor the impact of a specific load on the system resources. Using this technology, one can monitor the voltage magnitude, reactive power and most importantly the sensitivities of voltage magnitude, reactive power requirements, and transmission losses. It is conceivable that pricing can be performed in real time on a use-of-resources basis.6. Summary and conclusionsThis paper has addressed the impact of predominantly induction motor loads on voltage magnitudes, reactive power requirements, and transmission losses. A model has been proposed to evaluate this impact on large-scale power systems. The proposed model incorporates the physical model of induction motors into the power flow formulation. As such, it is a realistic model and captures the true behavior of these loads. Example calculations were carried out on a simplified power system. For this system, the voltage level, the active and reactive power requirements, and the transmission losses were computed vs. the total induction motor load. The model provides sensitivities of these quantities with respect to the inductionmotor loads and can be used to predict the total amount of load, which can be supported by the system _voltage stability limit.It was shown that there is a critical value of the load and when the load increased beyond this value,the reactive power requirements and the transmission losses increase in a highly nonlinear fashion. Theonset of this condition is system dependent and can be determined with a series of simulations. A practical approach will be to use probabilistic simulation techniques, similar to those described in Ref., to obtain a statistical distribution of the critical induction motor loads.The results provide the basis for deriving aggregate electric load models and the designing of a pricing schedule for voltage support and reactive power requirements. Specifically, the pricing is based on the cost function of the actual incremental losses and the cost of reactive power source requirements. Incremental loss cost is computed from the price of electric energy. The cost of reactive power sources is computed from the maximum required reactive power over a specified period of operation.譯文：在解除管制的環(huán)境下功率和電壓控制的定價問題摘要對由于處理某一類電負(fù)載而引起的功率、電壓、傳輸損耗的相關(guān)問題的研究。具體來說，主要是感應(yīng)電機(jī)負(fù)載上的電壓影響，功率要求和傳輸損耗的研究。這些問題的研究都與明確模型的感應(yīng)電動機(jī)機(jī)械負(fù)荷有關(guān)。進(jìn)而提出了一個簡化的電力系統(tǒng)的仿真結(jié)果?；谶@些結(jié)果，提出了一種電壓和功率價格結(jié)構(gòu)。本文的基本假設(shè)是，在解除管制的市場環(huán)境下，對電壓控制增量要求的費用應(yīng)計入引起的附加要求。這項工作的結(jié)果可以用來證明供應(yīng)商和客戶之間的長期定價協(xié)議。關(guān)鍵詞：功率；感應(yīng)電動機(jī)負(fù)荷；電壓；無功功率價格1. 引言電壓控制在電力系統(tǒng)中很重要的原因有許多：a.所有的終端設(shè)備都需要在額定電壓下正常工作。b.額定電壓下傳輸損耗最小。c.額定電壓能夠提高系統(tǒng)在站的干擾下的安全能力。系統(tǒng)將功率從一處傳到另一處的能力使電壓在系統(tǒng)中合理分配。當(dāng)電壓降到一個較低值時，系統(tǒng)的這種能力會受到損害。分析功率要求的靈敏度和實際電力負(fù)荷的增加可以檢測電力不能傳遞的問題。這種敏感性依賴于電力負(fù)荷的特點。這種敏感性分析使用了不同的電力負(fù)荷模型，即恒功率負(fù)載，恒阻抗負(fù)載，或兩者的結(jié)合壓敏負(fù)載。主要的負(fù)載大部分是感應(yīng)電動機(jī)。這些負(fù)載不符合以上提到的任何一種。但是，他們嚴(yán)重影響電力系統(tǒng)的穩(wěn)定性。在本文中，我們認(rèn)為在潮流制定和直接評估這種負(fù)載對功率的影響需要感應(yīng)電動機(jī)負(fù)載模型。結(jié)果表明，潮流的制定可以增強(qiáng)包括特定的感應(yīng)電動機(jī)負(fù)荷。在出現(xiàn)有趣的非線性現(xiàn)象時，感應(yīng)電動機(jī)的電壓值較低。在解除管制的市場環(huán)境中，這些現(xiàn)象時很有意義的研究，我們設(shè)計了一個基于這些現(xiàn)象的經(jīng)濟(jì)影響定價模型。本文結(jié)構(gòu)安排如下：首先，提出一種解決方案，并明確模型的感應(yīng)電動機(jī)。這一提法引入到通常的功率流問題的一個推廣。然后，介紹一種靈敏度分析程序。這種敏感性是基于對有限狀態(tài)的擴(kuò)展方法。所提出的方法應(yīng)用于一個簡化的系統(tǒng)包括感應(yīng)電動機(jī)負(fù)荷。對該系統(tǒng)的結(jié)果進(jìn)行了討論，并提出了一種電壓和功率定價方法。4. 算例結(jié)果 本文提出的模型應(yīng)用在一個簡單的電力系統(tǒng)顯示，由發(fā)電站，輸電線路，升壓變壓器，降壓變壓器和幾個異步電動機(jī)。該系統(tǒng)如圖2所示。系統(tǒng)的參數(shù)已被選定為代表的典型系統(tǒng)，如表1所示。重要的是要認(rèn)識到，汽車可能會或可能不會由變頻控制驅(qū)動器。對于這個系統(tǒng)，我們進(jìn)行的電壓水平的參數(shù)研究，功率要求，和傳輸損耗?？勺儏?shù)是總的感應(yīng)電動機(jī)負(fù)荷。此參數(shù)表示表1中的變量y。還注意到，該模型需要機(jī)械的負(fù)載轉(zhuǎn)矩，TM。的假設(shè)機(jī)械轉(zhuǎn)矩是表1中列出的。圖3說明了電壓的大小和發(fā)電機(jī)組功outputas總感應(yīng)電動機(jī)負(fù)荷增加的變化。注意，當(dāng)感應(yīng)電動機(jī)負(fù)荷超過0.90標(biāo)幺值，功需求增加，電壓下降到低于0.9 p.u.當(dāng)負(fù)荷超過1.2標(biāo)幺值，電壓崩潰。在這種情況下，所發(fā)生的是，感應(yīng)電機(jī)移動到很高的滑動操作點，在這種情況下，ss0.27，吸收高功，使終端電壓下降_voltage崩潰請注意，電壓崩潰是突然和意外。它是觀察所提出的圖4這一行為的重要。模型是現(xiàn)實的簡化模型如恒功率和恒阻抗負(fù)荷模型完全不同。在異步電動機(jī)的負(fù)載下系統(tǒng)的性能可以通過研究電壓幅值的靈敏度更好的理解，功率要求和傳輸損耗與感應(yīng)電動機(jī)負(fù)荷。圖46說明這些敏感的總的感應(yīng)電動機(jī)的額定負(fù)載的功能。在圖4中，這是明顯的電壓幅值的靈敏度很高的電機(jī)負(fù)載的方法1.2 p.u