Page1 Electrical Energy Transmission（电能输送）起飞英文
From reference 1
Growing populations and industrializing countries create huge needs for electrical energy. Unfortunately, electricity is not always ud in the same place that it is produced, meaning long-distance transmission lines and distribution systems are necessary. But transmitting electricity over distance and via networks involves energy loss.
So, with growing demand comes the need to minimize this loss to achieve two main goals: reduce resource consumption while delivering more power to urs. Reducing consumption can be done in at least two ways: deliver electrical energy more efficiently and change consumer habits.
Transmission and distribution of electrical energy require cables and power transformers, which create three types of energy loss:
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the Joule effect, where energy is lost as heat in the conductor (a copper wire, for example);
magnetic loss, where energy dissipates into a magnetic field;
the dielectric effect, where energy is absorbed in the insulating material.
The Joule effect in transmission cables accounts for loss of about 2.5 % while the loss in transformers range between 1 % and 2 % (depending on the type and ratings of the transformer). So, saving just 1 % on the electrical energy produced by a power plant of 1 000 megawatts means transmitting 10 MW more to consumers, which is far from negligible: with the same energy we can supply 1 000 - 2 000 more homes.network technology
Changing consumer habits involves awareness-raising programmers, often undertaken by governments or activist groups. Simple things, such as turning off lights in unoccupied rooms, or switching off the television at night (not just putting it into standby mode), or tting tasks such as laundry for non-peak hours are but a few examples among the myriad of possibilities.
On the energy production side, building more efficient transmission and distribution syste
ms is another way to go about it. High efficiency transformers, superconducting transformers and high temperature superconductors are new technologies which promi much in terms of electrical energy efficiency and at the same time, new techniques are being studied.ize The include direct current and ultra high voltage transmission in both alternating current and direct current modes.
出自文献 1：
人口增长和工业化国家导致电力能源的庞大需求量. 不幸的是, 电力的使用和生产常常不是在相同的地方，意味着长距离传输线路配电系统是必需的. 然而长距离输电以及通过网络这就涉及到能量损耗的问题。.
所以，随着需求的增长，就要使得这个损耗最小化，以达到两个主要目标: 在减少资源消耗，同时为用户传送更多电能。至少有两种方式可以实现减少消耗量：更有效地传送电能以及改变用户的习惯。
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出国留学利弊电能的传输和分配需要电缆和电力变压器, 他们产生三种类型的能量损失：焦耳效应, 那些长沙平面设计公司
在导体发热过程中损失的能量(例如铜金属线)；电磁损耗, 这部分能量被转化为电磁场；电介质效应, 这部分能量在绝缘材料中被吸收。
传输电缆中的焦耳效应导致大约2.5 % 的损耗，电力变压器中这个损耗大约在 1 %到 2 %之间 (取决与变压器的类型和电压等级). 所以在1000兆瓦的发电厂产出的电能中节省仅仅1%就意味着向用户传输了10 MW 能量，这是远不可忽视的：和它相同的能量，我们可以提供给1 000 - 2 000个家庭。
改变消费习惯涉及到宣传计划，这常常由政府或积极团体进行。这仅是些简单的小事，例如关掉无人房间的灯，或在晚上关掉电视（不只是把它进入待机模式），或把洗衣服安排在非高峰时段，这仅仅是无数的可行性中的几个例子。
在能源生产方面，建立更有效的传输和分配系统是减少损耗的另一种方式。高效变压器、超导变压器、高温超导体是能够保证电能效率的新技术，同时我们要研究新的工艺。这包括交直流切换模式下的直流和特高压输电。
From reference 2
心得体会网
Disturbing loads like arc furnaces and thyristor rectifiers draw fluctuating and harmonic currents from the utility grid. The non sinusoidal currents cau a voltage drop across the finite internal grid impedance, and the voltage waveform in the vicinity becomes distorted. Hence, the normal operation of nsitive consumers is jeopardized.
topActive filters are a means to improve the power quality in distribution networks. In order to reduce the injection of non sinusoidal load currents shunt active filters are connnected in parallel to disturbing loads (Fig. 1). The active filter investigated in this project consists of a PWM controlled three-level VSI with a DC link capacitor.The VSI is connected to the point of common coupling via a transformer. The configuration is identical with an advanced static var compensator.
The purpo of the active filter is to compensate transient and harmonic components of the load current so that only fundamental frequency components remain in the grid current. Additionally, the active filter may provide the reactive powerfurious consumed by the load. The control principle for the active filter is rather straightforward: The load current is
measured, the fundamental active component is removed from the measurement, and the result is ud as the reference for the VSI output current.
In the low voltage grid, active filters may u inverters bad on IGBTs with switching frequencies of 10 kHz or more. The harmonics produced by tho inverters are easily suppresd with small passive filters. The VSI can be regarded nearly as an ideally controllable voltage source. Inmedium voltage applications with power ratings of veral MVA, however, the switching frequency of today’s VSIs is limited to some hundred Hertz. Modern high power IGCTs can operate at around 1 kHz. Therefore, large passive filters are needed in order to remove the current ripple generated by the VSI. Furthermore, in fast control schemes the VSI no longer reprents an ideal voltage source becau the PWM modulator produces a considerable dead-time. In this project a fast dead-beat algorithm for PWM operated VSIs is developed [1].This algorithm improves the load current tracking performance and the stability of the active filter. Normally, for a harmonics free current measurement the VSI current
