电能质量翻译

四川大学电气信息学院电能质量报告第二章王飞鹏1143031228108班2014/6/1在此处键入文档摘要。摘要通常为文档内容的简短概括。在此处键入文档摘要。摘要通常为文档内容的简短 概括。ORIGIN OF POWER QUALITY VARIATIONS电能质量变化的来源This chapter describes the origin and some of the basic analysis tools of power quality variatio nsORIGIN电能质量变化这章介绍了电能质量变化的基本分析工具的起源The con secutive sect ions of the chapter discuss (voltage) freque ncy variati ons, voltage (magnitude) variations, voltage unbalanee, voltage fluctuations (and the result ing light flicker), and waveform distortio n.本章的连续的章节讨论(电压)频率变化，电压(幅度)的变化，电压不平衡度，电 压波动(和由此产生的光线闪烁)，和波形失真。A summary and con clusi ons for each of the secti ons will be give n at the end of this chapter.一种用于每个部分的摘要和结论将在本章的最后给出。2.1 VOLTAGE FREQUENCY VARIATIONS2.1电压频率变化Variati ons in the freque ncy of the voltage are the first power quality disturba nee tobe discussed here. After a discussion on the origin of frequency variations (the power bala nee) the method for limit ing the freque ncy variati ons (powerreque ncy con trol)isdiscussed. The section closes with an overview of consequencesof frequencyvariations and measurements of frequency variations in a number of interconnected systems.在该电压的频率变化是第一个电源质量扰动在这里讨论。后讨论在频率变化(功率平衡)的来源用于限制频率的变化(功率 -频率控制)。本节用的频率变化，和许多相互连接的系统 的频率变化的测量结果相近。2.1.1 Power Bala nee2.1.1功率平衡Storage of electrical en ergy in large amounts for long periods of time is notpossible, therefore the generation and consumption of electrical energy should be in bala nee. Any un bala nee in gen erati on and product ion results in a cha nge in the amount of en ergy prese nt in the system. The en ergy in the system is domin ated by the rotat ing电能的大量用于长时间储存是不可能的，因此，电能的产生和消耗应该是平衡的。任何不平 衡的产生和消耗在能量的系统中存在的量的变化。在系统中的能量以转动为主energy Erot of all generators and motors:所有的发电机和电动机的能量 Erot：Eg With J the total mome nt ofin ertia of all rotat ing mach ines and v the an gularvelocity at which these machi nes are rotati ng. An un bala nee betwee n gen erated power Pg and the total con sumptio n and lossesPc causes a cha nge in the amount ofrotational energy and thus in angular velocity:令J为所有旋转电机的转动惯量和 V为角速度在这些机器都旋转的总力矩。发电电力Pg和总消耗量和损失的PC之间的不平衡导致的旋转能量的量，从而在角速度的变化：dw _ Pg Petil Jti)The amount of inertia is normally quantified through theinertia constant H , which isdefi ned as the ratio of the rotati onal en ergy at nominal speed v0 and a base power Sb：转动惯量的值会通过惯性常数H，其定义为旋转能量的额定速度vo和基电源的Sb的比值通常量化The base power is normally taken as the sum of the (apparent) rated powers of all gen erators conn ected to the system, but the mathematics that will follow is in depe ndent of the choice of base power. Typical values for the in ertia con sta nt of large systems are betwee n 4 and 6 s.该基本功率通常取为连接到系统的所有发电机的(明显的)额定功率的总和，但这个数字是独 立于基本功率的。对于大型系统的惯性时间常数典型值是4和6秒之间。In sert ing (2.3) in (2.2), assu ming that the freque ncy remai ns close to the nominalfrequency, and replacingangular velocity by frequency give the following expression:代入(2.3)在(2.2)中，假设频率保持接近标称频率，并置换角速度由频率给下面的表达式:4磊旧-PJWhere Pg a nd Pc are per-unit (up) values on the same base as the in ertia con sta ntH.其中PG和PC为每单位(最多)在同一基地为惯性常数H。值Con sider a 0.01-pu un bala nee betwee n gen erati on and producti on in a system with an in ertia con sta nt of 5 s. This leads to a cha nge in freque ncy equal to 0.05 Hz/s. If there would be a 0.01-pu surplus of gen erati on, the freque ncy would rise to 51 Hz in 20 s; for a 0.01-pu deficit in gen erati on the freque ncy would drop to 49 Hz in 20 s. It is very difficult to predict the load with a 1% accuracy. To keep the freque ncy con sta nt some kind of con trol is n eeded.考虑发电和生产之间的0.01pu不平衡在一个系统中的5秒的惯性时间常数。这导致了在 频率0.05赫兹/秒的变化。如果将有0.01普盈余，频率将上升到51赫兹在20秒中;对于0.01-PU 缺额产生的频率将降低到49赫兹在20秒中。这是用1 %的精度非常难于预测的负载。为了保 持频率恒定的某种控制是必要的。The sudden loss ofa large power station of 0.15 pu will result in a frequency drop of1 Hz /s. In 1 s the freque ncy has dropped to 49 Hz. As the sudde n un expected loss of a large gen erator un it cannot be ruled out, there is obviously the n eed for an auto-matic con trol of the freque ncy and of the bala nee betwee n gen erati on and con sumpti on.大电站突然丧失0.15 PU将导致1赫兹/秒的频率下降。在1 s中频率已经下降到49赫兹。 作为一家大型发电机组的突然意外损失无法排除，显然需要对生产和消费之间的平衡的频率和 自动控制。For comparison we calculate the amount of electrical and magnetic energy prese ntin 500 km of a 400-kV three-phase overhead line whe ntran sport ing 1000 MWof active power at unity power factor. Assu ming1 mH /km and12 nF /km as inductanee and capacitanee,respectively, gives for the1electrical energy - CU2 =320 kJ and for the magnetic energy2 ?= 1040kJ.For unity power factor the peaks in magnetic and electricalen ergy(curre nt and voltage) occur at the same time, so that the maximum totalelectromagnetic energy equals 1360 kJ. As beforewe can express this as a time constant by dividing with the rated power. For a 1000-MVA base, we find a time constant of 1.4 ms. This is significantly less than the 4- to 6-s time constant for the rotational energy. This example confirms the statement at the start of this section that the energy present in a power system is dominated by the rotational energy of generators and motors.为了便于比较，我们计算传输时的电和磁的存在于 400 千伏三相架空线路 500 公里的架空线中单位功率因数中 1000 兆瓦的有功功率在。假设使用 1 mH/ 公里 12 NF / 公里的电感和电容，分别给出了电能 320 千焦和磁能 1040 千焦。为了统一， 功率因数在磁性能和电能的峰值（电流和电压） 发生在同一时间，以使最大总电磁 能量等于 1360 千焦。和以前一样，我们可以通过与额定功率相除表示这是一个时间 常数。对于一个 1000 兆伏安的 基站，我们发现有 1.4 毫秒的时间常数。这是小于 4 - 至6 - S 的时间常数对于旋转能量。这个例子证实了在本节中的陈述即电力系统中 的能量由发电机和电动机的转动能量占主导地位。Power -Frequency Control电能频率的控制To maintain the balance between generation and consumption of electrical energy most large generator units are equipped with power-frequencycontrol. Maintaining the frequency close to its nominal value is a natural consequence of maintaining the balance between generation and consumption. The principle of power-frequency controlis rather simple. The measured frequency is compared with a frequency setting (the nominal frequency, 50 or60 Hz, in almost all cases). When the measured frequency is higher than the nominal frequency, this indicates a surplus of rotational energy in the system. To mitigate this, the generator reduces its active power output. More correctly, the mechanical input to the turbine generator is reduced. This leads after a transient to a new steady state with a lower amount of electrical energy supplied to the system.为了发电和消耗之间的平衡， 大型发电机组都配备了功率 - 频率控制。 维护频 率接近其标称值是保持生产和消费之间的平衡的结果。电源 -变频调速的原理是相当单的。所测量的频率与设置的(标称频率， 50 或 60 赫兹，在几乎所有的情况下)相比 较。当所测量的频率比标称频率更高，这表明在系统中的旋转能量过剩。为了减轻这 种情况，发电机降低其有功的功率输出。更准确地涡轮机发电机，机械输入被降低。 此导致了新的供给系统较少能量的稳定状态。The prin ciple of powerreque ncy con trol is show n in Figure 2.1. Thebetween a change in the powerinput to the speed governor is a corrected power setting (corrected for the deviation of the frequency from its setting). We will come back to the choice of the power setting below. The speed governor is a control system that delivers a signal to the steam valves with a thermal power station to regulate the amount of steam that reaches the turbine. The turbine reacts to this, with a certain delay, by changing the amount of mechanical power. Much more detailed models can be found in the literature e.g, 6, Chapter 10; 26, Chapter 3. For the purpose of this chapter, it is sufficient to know that there is a time delay of several seconds (10 s and more for large units)sig nal at the in put of the gover nor and an in crease in the mecha ni cal power produced by the turb ine.电源的原理-频率控制如图2.1所示。输入到调速器的是一个校正后的功率（是 频率对于设定值的修正）。我们回来到下面的电源的选择设置。限速器是一个控制系 统，它提供了一个信号，蒸汽阀与热电站来调节蒸汽到达涡轮机的量。涡轮对这个结 果给予反应，具有一定的延迟，通过改变机械动力的量。更详细的模型可以在文献例 如, 6,第10章找到;26，第3章。本章的目的是必须要知道，有几秒钟的延迟时间（10秒多为大户型）在速度调节器的输入功率信号的变化和由涡轮机产生的机械功率 增加了之间SpM 一九恤mGovernorPower frecjuencv rontrol.AliFrequeicyIf we con sider the system in steady state, where the product ion of thegen erator equals the in put sig nal to the speed gover nor, the mecha nical power is as follows:如果我们考虑到系统的稳定状态中由发电机产生的量等于输入调速信号需要卩=set 才丿 一的量，机械功率为：where R is referred to as the drop setting . This relation is shown in Figure2.2. Whe n the system freque ncy drops, the power product ion in creases. This compe nsates for the cause of the freque ncy drop (a deficit of gen erati on). Thefrequency setting is equal to the nominal frequency of the system and thesame for all generators connected to the system. In the Nordic system the freque ncy should not only be with in a certa in band but also on average be equal to 50 Hz to ensure that clocks indicate a correct time. When the integrated frequency error （the time differenee for a clock） exceeds a certain value, the frequency setting of the generators is slightly changed. But the sett ing rema ins the same for all gen erators.其中R被称为下降设置。此关系示于图2.2。当系统频率下降，电力生产的增加。这可以补偿的频率下降（代赤字）。频率设置为系统中最重要的频率并连接到系统的 所有发电机的额定频率。在北欧的系统中频率不应该只在一定的范围内，而且平均等于50赫兹，确保钟表指示正确的时间。当集成的频率误差（为一个时钟的时间差）超过一定值时，发电机的频率设定稍有改变。但所有发电机的设置保持相同。Spinning Reserve旋转备用To allow for an in crease in gen erated power whe n there is a deficit ofgen erati on, for example, because a large unit has bee n disc onn ected from thesystem, the power produced by a gen erator should be less tha n itsmaximumcapacity. The amount of extra power which can be produced in a matter of sec onds is called spinning reserve为了在发电能力在缺额时能增加发电，例如，因为一个大的单元已经断开从 系统连接，由一台发电机产生的功率应小于其最大容量。额外的电能，可以在几 秒钟内就可以产生的量称为旋转备用。Figure 2.3 Daily load curve (thick solid curve) for a power system, with thesum of generator power settings (thin solid lines) and the spinning reserve (dashed lin es).图2.3日负荷曲线（粗实线）的动力系统，与发电机电源设置（细实线）之和为旋转备用（虚线）。interconnected system should at least be equal to the largest unit connected to the system. For smaller systems during low load, the spinning reserve should be relatively high. However, in large interconnected systems like the Nordic system or the European interconnected system, a spinning reserve of a few percent is acceptable.互联系统应该至少等于连接到系统的最大单元。对于低负载时更小的系统， 旋转备用应该是相对较高的。然而，在大型互联系统，如北欧系统或欧洲的互联 系统，百分之几的一个旋转备用是可以接受的。Choice of Power Set PointFigure 2.3 shows a hypothetical daily loadcurve for a system. Such a curve is used to schedule the amount of generation capacity needed. The day is divided into a number of time intervals, typically of 15 to 30 min duration. For each interval the expected load is determined. This required generation is then spread over a number of generator stations. For each time interval the sum of the power settings is chosen equal to the expected load. The actual scheduling is in most countries done by a free-market principle where each generator can place bids. When such a bid is accepted for a certain time block, it will become the power setting of the generator for that block. Even the load is in principle market based, but the distribution companies typically place bids based on the expected consumption of their customers. For example, see 25 for a description of the various market principles.2.32.1.2.2 选择显示了一个系统假想的日负荷曲线。 这样的曲线被用来安排对于每个时间间隔的预期由负载来确定。这些分散至被需要的发电机数。每个时间间隔的功率设置的总和等于预期的负载。在实际用电计划中，大多数国家是有一个自由市场的原则，每个发电机可以出价来完成发电计划。当这样的出价在一定时间段可接受，它将成为产生该块的电能设置。即使负载在原则上是市场化， 但发行公司通常根据其客户预期消耗来出价。 例如，见25 对各种市场原则的描述。Also for each time interval a spinning reserve can be decided, but this istypically kept at a fixed percentage of the total power. Even for the spinningreserve and the droop setting market principles can be applied (as discussed,e.g., in 335).另外每次间隔的旋转备用是可以确定的，而这通常保持在总功率的一个固定 百分比。即使对旋转备用和固定偏差设置，市场原则仍然可以应用(如讨论，例 如，在 335 )Sharing of LoadA change in load, or a change in generation setting, results in a change ingen erated power for all gen erator un its equipped with power-reque ncy con trol.Consider a system with n generators with power setting = 1, . ; n; droop setting Ri; and frequency setting fset Note that the power setting and the droop setting are different for each unit whereas the frequency setting is the same. The produced power for each generator at a system2.1.2.3 负载分担负载的变化，或产生背景的变化，将导致所有配带功率 - 频率控制机组的出力变化。考虑有n个发电机，Pi, set, i = 1，；N;暂降和频率设定Fset。需要注意的是电源设置和偏差的设置是不同的每个单位，而频率设置是一样的。每个发电机在系统中产生的电能是IL6)右 V -/an)The sum of all power sett ings is equal to the total predicted load:所有的电源设置的总和等于总预测负荷:J1工尸lsit = /Y(2J)4*1Assume that the actual load deviates from the predicted load by an amount D Pc, so that in steady state假定实际负载从预测的负载偏离 APc,因此，在稳定状态J1X = PcCombi ning (2.6), (2.7), and (2.8) gives结合（2.6）,（ 2.7 ）和（2.8）给出(2-1which gives for the steady-state freque ncy这给出了稳态频率The in crease in con sumpti on causes the system freque ncy to drop by anamount determ ined by the power-reque ncy con trol sett ings of all thegen erators that con tribute. Each gen erator con tributes to the in crease inconsumption by ratio of the inverse of its droop setting:消费的增加导致系统频率下降到由所有的电能的频率控制发电机所决定的一个 值。每台发电机有助于通过其偏差设置的增加：illhThe droop setting is normally a constant value in per unit with thegen erator rati ng as a base. For a gen erator of rated powerS and per- un it droopsetting Rpu, the droop setting in hertz per megawatt is偏差的设置通常是在每单元与发电机的评估作为基础的恒定值。对于额定功率S 和单位下降的发电机设置 Rpu上，在每兆瓦赫兹偏差设置with typically f set = fo, the nominal frequency. The new steady-state frequency is obtained from inserting (2.12) in (2.10) under the assumption that the per-unit droop sett ing is the same for all un its:与通常Fset=F0，标称频率。新的稳态频率是从假设每单位偏差的设置是相同的对于 所有单位代入（2.12 ）在（2.10）得到:5J 二上iLT 一The relative drop in frequency is equal to the relative deficit in generation times the per-unit droop sett ing:在频率的相对降等于在产生时间每单位设置的相对缺额:U 14）* _ */sct*Each gen erator con tributes by the ratio of its rated power to any deficit ingen erati on:每个发电机有助于其额定功率在任何生产电能中的比例：sk几=严LSET +芒生迅（2.15）Thus large gen erators con tribute more tha n small gen erators. This callsfor a spin- ning reserve which is a fixed perce ntage of the rated power of thegen erator un it.因此，大型发电机贡献超过小型发电机。这需要一个旋转储备，是发电机组的 额定功率的固定百分比。2.1.3 Consequences of Frequency VariationsAs far as the authors are aware, no equipme nt problems are being reporteddue to frequencyvariations. Still some of the consequences andpotentialproblems are mentioned below.2.1.3频率的变化后果据笔者所知，没有任何设备问题被报道出来是由于频率变化。还是一些后果和潜在的 问题如下2.131 Time Deviation of Clocks2.131时间偏差Clocks still often synchronize to the voltage frequency (typically by counting zero cross in gs). Aeon seque nee of freque ncy variati ons is therefore that clocks will show an erroneous time. The size of the error depends on the deviatio n of the freque ncy from the nominal freque ncy.Consider a system with nominal frequency fOand actual frequency f (t). The nu mber of zero cross ings in a small timeAt isNote that there are two zero cross ings per cycle. In a long periodT (e.g., oneday), the nu mber of zero cross ings is时间偏差还是经常同步到电压频率(通常通过计算过零点)。因此，频率变 化的后果是，时钟将显示一个错误的时间。该误差的大小依赖于频率的标称频率 的偏差。考虑标称频率fO和实际频率f (t)的一个系统。过零点在一个小时间At是多少需要注意的，每个周期有两个零交叉点。在很长的周期T (例如，一天)，过零点的数目是(2.17)JBecause the clock assumes a freque ncy fO, the appare nt elapsed time is 因为时钟假定一个频率为fO，经过的时间是T + 直T =导(2.18)From (2.17) and (2.18) the time errorAT is obtained as从（2.17 ）和（2.18 ）的时间误差AT可得AT= dt(2J 9Jq JqA freque ncy of 50.05 Hz in stead of 50 Hz will cause clocks to run 0.1%faster. This may not appear much, but after one day the deviati on in clocks is0.001360024?86.4 s. Thus 0.05 Hz freque ncy deviation causes clocks to have an error of over 1 min per day. A frequency equal to 50.5 Hz (1% deviation)wouldcause clocks to be 15 min ahead after one day50.05赫兹，而不是50赫兹的频率将导致时钟运行速度更快的 0.1 %。这可能不会出 现太大，但有一天，在后时钟偏差 0.001 *3600*24=86.4秒。因此，0.05赫兹的频率 偏差导致时钟每天有超过1分钟的误差。一个频率等于50.5赫兹(1 %的偏差)会导 致时钟一天后超前15分钟。2.1.3.2 Variations in Motor Speed2.1.3.2Variati ons in Motor SpeedAlso the speed of in ducti on motors andsynchronous motors is affected whe n the voltage freque ncy cha nges. But as the freque ncy does not vary more tha n a few perce nt, these speed variati ons are hardly ever a problem. Very fast fluctuati ons in freque ncy could cause mecha ni cal problems, but in large in terc onn ected systems the rate of cha nge of freque ncy remai ns moderate eve n for large disturba nces. Variati ons in voltage magnitude will have a bigger influence.异步电机速度变化也反应电机和同步电机的转速，电压频率变化时的影响。 但是，由于频率变化不超过百分之几，这些速度变化几乎不是问题。在频率非常 快的波动可能会造成机械故障，但在大型互联系统频率的变化率保持适中甚至对 大扰动。电压幅度的变化会有更大的影响。2.1.3.3 Variations in Flux Lower2.1.3.3 磁通下限的变化frequency implies a higher flux for rotating machines and transformers. This leads to higher magnetizing currents. The design of rotating machines and transformers is such that the transition from the linear to the nonlinear behavior (the “ knee” in the magnetic flu-xfield, B-H, curve) is near the maximum normal operating flux. An increase of a few percent in flux may lead to10% or more increase in magnetizing current. But the frequency variation is very rarely more than 1%, whereas several percent variations in voltage magnitude occur daily at almost any location in the system. One percent drop in frequency will give the same increase in flux as 1% rise in voltage magnitude. Where saturation due to flux increase is a concern, voltage variations are more likely to be the limiting factor than frequency variations.频率意味着对旋转较高的机器和变压器的通量。这导致较高的磁化电流。 旋转电机和变压器设计是从直线的过渡到非线性行为(在磁通量场的“拐点”， BH曲线）靠近最大正常工作磁通。 百分之几的磁通的增加可能会导致 10以上的磁化电流增加。但频率的变化是很少超过 1，而几个百分点的电压变化每天在系统几乎任何地方都会发生。在频率的百分之一降将给予1电压上升。饱和度导致磁通量增加是值得考虑，电压的变化更可能成为比频率变化更重要的限制因素。2.1.3.4 Risk of Underfrequency Tripping2.1.3.4 低频跳闸的风险Larger frequency deviations increase the risk of load or generator tripping on over frequency or on under frequency. Over frequency and under frequency relays are set at a fixed frequency to save the power system during very severe disturbances like the loss of a number of large generating units. The most sensitive settings are normally for the under frequency relays. In some systems the first level of under frequency load shedding occurs already for 49.5 Hz, although 49 Hz is a more common setting. The loss of a large generator unit causes a fast drop in frequency due to the sudden deficit in generation followed by a recovery when the power -reque ncy con trol in creases the producti on of the rema ining un its. The maximum frequency deviation during such an event is rather independent of the preevent frequency. Thus when the preevent frequency is lower, the risk of an unnecessary under frequency trip increases.较大的频率偏差增加了负荷或发电机上的过频或欠频跳闸的风险。过频和欠频 继电器被设置在一个固定的频率，以在非常严重的波动像大量的大型发电机组单元缺 失中保护电力系统。最敏感的设置是正常的低频率继电器。在某些系统中的低频减载 的第一级已经发生为在 49.5赫兹，虽然 49 赫兹是一种较为常用的设置。大型发电机组缺失导致频率快速下降，由于突然发电缺额，紧接着电源频率控制增加剩下机组的生产。期间的最大频率偏差是相当独立于事先的频率。因此，当事先的频率较低，不 必要低频跳闸的危险增加。Generally speaking large frequency variations point to unbalance between generation and (predicted) consumption. As long as this unbalance is equally spread over the system, it is of limited concern for the operation of the system. As shown in Section 2.1.2 the daily load variations are spread equally between all gen erator un its that con tribute to powerfreque ncy con trol. However, fastfluctuations in frequency (time scales below 1 min) point to a shorter term unbalance that is associated with large power flows through the system. These fluctuating power flows cause a higher risk of a large-scale blackout.一般来说大的频率变化意味着发电和(预测)消费之间的不平衡。只要这个不 平衡被平均地分布在 系统，基本上关于系统的稳定是不需要过度关心的。如第 2.1.2 节的日负荷变化也同样遍布发电机之后总， 这有助于功率 - 频率控制。 然而，在快速 频率波动(时间尺度小于 1 分钟)这就意味着短期不平衡与大电流流过系统。这些变 化的功率流导致大规模停电的风险提高。Distributed generation has also become a concern with frequency variations. Most units are equipped with under frequency and over frequency protection. The Under frequency protection is the main concern as this is due to lack of generation. Tripping of distributed generation units will aggravate the situatio