发布时间:2024-06-02 11:30:12 人气:
电力电子技术在电力系统中的应用
发电环节、输电环节、配电环节。
1、发电环节:电力电子技术在发电环节中有多种应用。包括静止励磁技术,用于控制和调节发电机的励磁电流,确保发电机的稳定运行。电力电子技术还应用于水利和风力发电机组中的变频调速系统,用于调节发电机的转速和输出频率,适应不同的负载需求。
2、输电环节:电力电子技术在输电环节中也有重要的应用。柔性交流输电(FACTS)是一种利用电力电子设备来控制和优化交流输电系统的技术。可以通过调节电压、电流和相位等参数来实现电力系统的稳定运行和优化功率流动。高压直流输电(HVDC)是一种利用电力电子设备将电能以直流形式输送的技术,有长距离传输、低损耗和稳定性好等优点。
3、配电环节:电力电子技术在配电环节中也有广泛的应用。在用户电力技术方面,电力电子设备如逆变器、变频器等用于控制和调节电能的质量和功率因数,满足用户对电能的不同需求。在智能电网中,电力电子技术被用于实现电力系统的智能化和自动化,包括电能计量、远程监控、电能管理等方面的应用。这些技术可以提高电力系统的效率、可靠性和可持续性。
电力电子技术的应用领域有哪些?
应用1、一般工业:交直流电机、电化学工业、冶金工业。
2、交通运输:电气化铁道、电动汽车、航空、航天、航海。
3、电力系统:高压直流输电、柔性交流输电、无功补偿。
4、电子装置电源:为信息电子装置提供动力。
5、家用电器:“节能灯”、变频空调。
6、其他:UPS、 航天飞行器、新能源、发电装置。
扩展资料:
1、 优化电能使用
通过电力电子技术对电能的处理,使电能的使用达到合理、高效和节约,实现了电能使用最佳化。例如,在节电方面,针对风机水泵、电力牵引、轧机冶炼、轻工造纸、工业窑炉、感应加热、电焊、化工、电解等14个方面的调查,潜在节电总量相当于1990年全国发电量的16%,所以推广应用电力电子技术是节能的一项战略措施,一般节能效果可达10%-40%,我国已将许多装置列入节能的推广应用项目。
2、改造传统产业和发展机电一体化等新兴产业。
据发达国家预测,今后将有95%的电能要经电力电子技术处理后再使用,即工业和民用的各种机电设备中,有95%与电力电子产业有关,特别是,电力电子技术是弱电控制强电的媒体,是机电设备与计算机之间的重要接口,它为传统产业和新兴产业采用微电子技术创造了条件,成为发挥计算机作用的保证和基础。
3、电力电子技术高频化和变频技术的发展,将使机电设备突破工频传统,向高频化方向发展。实现最佳工作效率,将使机电设备的体积减小几倍、几十倍,响应速度达到高速化,并能适应任何基准信号,实现无噪音且具有全新的功能和用途。
4、电力电子智能化的进展,在一定程度上将信息处理与功率处理合一,使微电子技术与电力电子技术一体化,其发展有可能引起电子技术的重大改革。
参考资料:
与逆变器相关的英文文章
Inverter may refer to
Inverter (electrical), a device that converts direct current to alternating current
Inverter (air conditioning), an air conditioner that can continuously regulate its output by altering the compressor speed in response to cooling demand
Uninterruptible power supply, which often are based on an electrical inverter
Inverter (logic gate), a logic gate also called a NOT gate
Inverter (electrical)
An inverter is an electrical device that converts direct current (DC) to alternating current (AC); the converted AC can be at any required voltage and frequency with the use of appropriate transformers, switching, and control circuits.
Static inverters have no moving parts and are used in a wide range of applications, from small switching power supplies in computers, to large electric utility high-voltage direct current applications that transport bulk power. Inverters are commonly used to supply AC power from DC sources such as solar panels or batteries.
The electrical inverter is a high-power electronic oscillator. It is so named because early mechanical AC to DC converters were made to work in reverse, and thus were "inverted", to convert DC to AC.
The inverter performs the opposite function of a rectifier.
Applications
DC power source utilization
An inverter converts the DC electricity from sources such as batteries, solar panels, or fuel cells to AC electricity. The electricity can be at any required voltage; in particular it can operate AC equipment designed for mains operation, or rectified to produce DC at any desired voltage.
Grid tie inverters can feed energy back into the distribution network because they produce alternating current with the same wave shape and frequency as supplied by the distribution system. They can also switch off automatically in the event of a blackout.
Micro-inverters convert direct current from individual solar panels into alternating current for the electric grid.
Uninterruptible power supplies
An uninterruptible power supply (UPS) uses batteries and an inverter to supply AC power when main power is not available. When main power is restored, a rectifier is used to supply DC power to recharge the batteries.
Induction heating
Inverters convert low frequency main AC power to a higher frequency for use in induction heating. To do this, AC power is first rectified to provide DC power. The inverter then changes the DC power to high frequency AC power.
[edit] HVDC power transmission
With HVDC power transmission, AC power is rectified and high voltage DC power is transmitted to another location. At the receiving location, an inverter in a static inverter plant converts the power back to AC.
[edit] Variable-frequency drives
Main article: variable-frequency drive
A variable-frequency drive controls the operating speed of an AC motor by controlling the frequency and voltage of the power supplied to the motor. An inverter provides the controlled power. In most cases, the variable-frequency drive includes a rectifier so that DC power for the inverter can be provided from main AC power. Since an inverter is the key component, variable-frequency drives are sometimes called inverter drives or just inverters.
[edit] Electric vehicle drives
Adjustable speed motor control inverters are currently used to power the traction motors in some electric and diesel-electric rail vehicles as well as some battery electric vehicles and hybrid electric highway vehicles such as the Toyota Prius. Various improvements in inverter technology are being developed specifically for electric vehicle applications.[2] In vehicles with regenerative braking, the inverter also takes power from the motor (now acting as a generator) and stores it in the batteries.
[edit] Air conditioning
Main article: Inverter (air conditioning)
An air conditioner bearing the inverter tag uses a variable-frequency drive to control the speed of the motor and thus the compressor.
[edit] The general case
A transformer allows AC power to be converted to any desired voltage, but at the same frequency. Inverters, plus rectifiers for DC, can be designed to convert from any voltage, AC or DC, to any other voltage, also AC or DC, at any desired frequency. The output power can never exceed the input power, but efficiencies can be high, with a small proportion of the power dissipated as waste heat.
Warnings
Some low power inverters have a warning not to use conventional fluorescent lighting. This is due to the power correction capacitor connected in parallel with the lamp. Removing the capacitor will fix the problem. What may not be known is that in dual lamp fittings the capacitor may be connected in series with the second lamp, thus removing the problem as well as the stroboscopic effect caused by the mains frequency.
Basic designs
In one simple inverter circuit, DC power is connected to a transformer through the centre tap of the primary winding. A switch is rapidly switched back and forth to allow current to flow back to the DC source following two alternate paths through one end of the primary winding and then the other. The alternation of the direction of current in the primary winding of the transformer produces alternating current (AC) in the secondary circuit.
The electromechanical version of the switching device includes two stationary contacts and a spring supported moving contact. The spring holds the movable contact against one of the stationary contacts and an electromagnet pulls the movable contact to the opposite stationary contact. The current in the electromagnet is interrupted by the action of the switch so that the switch continually switches rapidly back and forth. This type of electromechanical inverter switch, called a vibrator or buzzer, was once used in vacuum tube automobile radios. A similar mechanism has been used in door bells, buzzers and tattoo guns.
As they became available with adequate power ratings, transistors and various other types of semiconductor switches have been incorporated into inverter circuit designs.
[edit] Output waveforms
The switch in the simple inverter described above, when not coupled to an output transformer, produces a square voltage waveform due to its simple off and on nature as opposed to the sinusoidal waveform that is the usual waveform of an AC power supply. Using Fourier analysis, periodic waveforms are represented as the sum of an infinite series of sine waves. The sine wave that has the same frequency as the original waveform is called the fundamental component. The other sine waves, called harmonics, that are included in the series have frequencies that are integral multiples of the fundamental frequency.
The quality of the inverter output waveform can be expressed by using the Fourier analysis data to calculate the total harmonic distortion (THD). The total harmonic distortion is the square root of the sum of the squares of the harmonic voltages divided by the fundamental voltage:
The quality of output waveform that is needed from an inverter depends on the characteristics of the connected load. Some loads need a nearly perfect sine wave voltage supply in order to work properly. Other loads may work quite well with a square wave voltage.
[edit] Advanced designs
H-bridge inverter circuit with transistor switches and antiparallel diodesThere are many different power circuit topologies and control strategies used in inverter designs. Different design approaches address various issues that may be more or less important depending on the way that the inverter is intended to be used.
The issue of waveform quality can be addressed in many ways. Capacitors and inductors can be used to filter the waveform. If the design includes a transformer, filtering can be applied to the primary or the secondary side of the transformer or to both sides. Low-pass filters are applied to allow the fundamental component of the waveform to pass to the output while limiting the passage of the harmonic components. If the inverter is designed to provide power at a fixed frequency, a resonant filter can be used. For an adjustable frequency inverter, the filter must be tuned to a frequency that is above the maximum fundamental frequency.
Since most loads contain inductance, feedback rectifiers or antiparallel diodes are often connected across each semiconductor switch to provide a path for the peak inductive load current when the switch is turned off. The antiparallel diodes are somewhat similar to the freewheeling diodes used in AC/DC converter circuits.
Fourier analysis reveals that a waveform, like a square wave, that is antisymmetrical about the 180 degree point contains only odd harmonics, the 3rd, 5th, 7th etc. Waveforms that have steps of certain widths and heights eliminate or “cancel” additional harmonics. For example, by inserting a zero-voltage step between the positive and negative sections of the square-wave, all of the harmonics that are divisible by three can be eliminated. That leaves only the 5th, 7th, 11th, 13th etc. The required width of the steps is one third of the period for each of the positive and negative steps and one sixth of the period for each of the zero-voltage steps.
Changing the square wave as described above is an example of pulse-width modulation (PWM). Modulating, or regulating the width of a square-wave pulse is often used as a method of regulating or adjusting an inverter's output voltage. When voltage control is not required, a fixed pulse width can be selected to reduce or eliminate selected harmonics. Harmonic elimination techniques are generally applied to the lowest harmonics because filtering is more effective at high frequencies than at low frequencies. Multiple pulse-width or carrier based PWM control schemes produce waveforms that are composed of many narrow pulses. The frequency represented by the number of narrow pulses per second is called the switching frequency or carrier frequency. These control schemes are often used in variable-frequency motor control inverters because they allow a wide range of output voltage and frequency adjustment while also improving the quality of the waveform.
Multilevel inverters provide another approach to harmonic cancellation. Multilevel inverters provide an output waveform that exhibits multiple steps at several voltage levels. For example, it is possible to produce a more sinusoidal wave by having split-rail direct current inputs at two voltages, or positive and negative inputs with a central ground. By connecting the inverter output terminals in sequence between the positive rail and ground, the positive rail and the negative rail, the ground rail and the negative rail, then both to the ground rail, a stepped waveform is generated at the inverter output. This is an example of a three level inverter: the two voltages and ground.[3]
[edit] Three phase inverters
3-phase inverter with wye connected loadThree-phase inverters are used for variable-frequency drive applications and for high power applications such as HVDC power transmission. A basic three-phase inverter consists of three single-phase inverter switches each connected to one of the three load terminals. For the most basic control scheme, the operation of the three switches is coordinated so that one switch operates at each 60 degree point of the fundamental output waveform. This creates a line-to-line output waveform that has six steps. The six-step waveform has a zero-voltage step between the positive and negative sections of the square-wave such that the harmonics that are multiples of three are eliminated as described above. When carrier-based PWM techniques are applied to six-step waveforms, the basic overall shape, or envelope, of the waveform is retained so that the 3rd harmonic and its multiples are cancelled.
3-phase inverter switching circuit showing 6-step switching sequence and waveform of voltage between terminals A and CTo construct inverters with higher power ratings, two six-step three-phase inverters can be connected in parallel for a higher current rating or in series for a higher voltage rating. In either case, the output waveforms are phase shifted to obtain a 12-step waveform. If additional inverters are combined, an 18-step inverter is obtained with three inverters etc. Although inverters are usually combined for the purpose of achieving increased voltage or current ratings, the quality of the waveform is improved as well.
传统直流输电是指什么?
直流输电是指将发电厂发出的交流电,经整流器变换成直流电输送至受电端,再用逆变器将直流电变换成交流电送到受端交流电网的一种输电方式。主要应用于远距离大功率输电和非同步交流系统的联网,具有线路投资少、不存在系统稳定问题、调节快速、运行可靠等优点。
电力电子在电力系统中的应用与新能源发电与智能电网什么关系
可以说目前的电力系统中电力电子无处不在,不管是新能源领域还是传统电网领域。在传统电网中的SVC,STACOM,以及HVDC等都是电力电子技术的典型应用。
新能源领域主要是指新能源发电的一些控制以及并网逆变器这块。就拿光伏发电来说,光伏出来的电势直流电,电压一般较低,需要先用DC变换器将电压升高而且保证电压稳定,还需要实时跟踪光伏的最大功率输出。在得到较高的直流电压下还需要通过逆变器才能与大电网相连,逆变器就是典型的电力电子设备。同样,在风力发电中的双馈电机,它需要用AC/DC/AC变化器进行能量的转换。当然里边的无功补偿一类的设备也都是电力电子技术的应用。所以说以后的电网,也就是智能电网,必须要建立在电力电子技术基础之上。
高压直流输电中如何将高压直流电变为高压交流电?与UPS的原理相同吗?
直流变为交流叫逆变,交流到直流叫整流,无论高压低压,原理是一样的。UPS里面是包含了整流和逆变两个过程,原理一样,但具体的过程以及数值和设定的参数有关。整流,全波整流电路就是利用二极管单向导通的特性,用4个二极管连成一个桥式整流电路,使输入端电是交流电流,其波形是正弦波,电流方向是交变的,而输出端波形电流变为同一方向,再经过滤波电路将波形滤掉之后可得到直流电。逆变是整流的逆过程,是通过晶闸管实现的,把直流电逆变成交流电的电路称为逆变电路。在特定场合下,同一套晶闸管变流电路既可作整流,又能作逆变。
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