One, overview
With the development of social economy, industrial production in large investment in advanced equipment to create a rich value, at the same time the equipment load nonlinear characteristics ofits own, causing all kinds of pollution and disturbance, especially the pollution to the grid, causinghuge waste of power resources.
1 of users, the waste of electric energy is mainly in four aspects:
(1) is occupying the system reactive power.
Electrical equipment in the active power consumption at the same time, for the inductive load was also accompanied by a large number of reactive power from the power supply to the load, power factor is reflected by the percentage of the total active power consumption of electrical equipmentpower, low power factor, increasing the line losses of power supply. The reactive power compensation to reduce the reactive power to occupy, improve the power factor of system, which can save energy, reduce the loss.
(2) is a mass of harmonic system
Provided the ideal utility grid voltage should be a single, fixed frequency and voltage amplitude specified. Appearance of harmonic current and harmonic voltage, the utility grid is a kind of"pollution", it is the use of electric equipment of the deterioration of the environment, cause all kinds of fault. In the past thirty years, the rapid use of various power electronic devices harmonics pollution is becoming more and more serious, all kinds of fault, fires and accidents caused by harmonics also continue to occur, the severity of the harm of harmonics to attract attention.
(3) the system voltage fluctuation
The fluctuation of the system voltage can not only make the system energy consumption to increase, at the same time, affect the service life of the equipment, can solve the problem of energy consumption and the service life of the equipment through the voltage regulation and stability of the system.
(4) is the electrical equipment load utilization is not reasonable
Reasonable adjustment of power distribution lines, improve the load utilization rate, reduce the power loss.
The 2 harmonic harm on the public power grid and other systems generally have the following aspects:
(1) the utility grid harmonic components in the additional harmonic losses, reduce the generation,transmission and efficiency of electrical equipment, a large number of effects of 3 harmonic normal work of electrical equipment;
Influence of harmonic on the motor (2) in addition to cause additional loss, will produce mechanicalvibration, noise and over voltage transformer, the severe local overheating. Harmonic to capacitor,cable and other equipment overheating, insulation aging, shorten life, and even damage;
(3) harmonics can cause the utility grid parallel resonance and series resonant part, so that theharmonic amplification, which makes the (1) and (2) the harm is greatly increased, and even lead to serious accidents, such as fire explosion;
(4) harmonic will lead to malfunction of relay protection and automatic device, and inaccurate measurement of electrical measuring instruments;
(5) the harmonic interference on the communication system of adjacent light, noise, reduce the communication quality; or cause loss of data, the communication system can not work properly.
Two, the purpose and significance
With the scientific attitude and the principle of seek truth from facts, through the diagnosis and evaluation of precision, to help users analyze the source of electrical energy waste in the system,the user understand the energy waste problem, through scientific management, reduce theoccupied system reactive power, the power factor reaches the national standard or higher; reduce the harmonic content in the system, so that the it is far better than the national standard; thevoltage regulation and stability of the system to solve the problem of energy consumption and the service life of the equipment; power allocation and reasonable adjustment of line load, improve theutilization rate, reduce the power loss, for the user to save the production cost, improve the competitive advantage, but also make a positive contribution to promoting the development of social economy, sustainable development environmental protection, human.
Four, solutions
The commonly used methods for harmonic control integrated solutions outside notting have two kinds, passive filtering and active filtering. On the advantages and disadvantages of the two methods and the analysis of market prospects and economic benefits.
1 passive harmonic filter
The main structure of the passive filter is connected in series with the reactor and capacitor,consisting of LC series circuit, parallel to the system, the resonant frequency of LC circuit is set in the harmonic frequency to filter, such as 5 times, 7 times, 11 times the resonance point, to filter theharmonic 3 purposes. Its low cost, but the filtering effect is not very good, if the resonant frequency is set properly, will produce resonance with the system. Now, the market circulation filtering methodsis more a, mainly because of low cost, easy to accept the user. Although poor filtering effect, as long as it meets the national standard limit of harmonic and reactive power sector to therequirements on the line. Because of its low cost, market demand is big, in general, low pressure 0.4KV system used by most of passive filter, high pressure 10KV is almost always used in this wayto manage harmonic. Since the majority of small and medium-sized enterprises of our country are private owners, the harm of harmonic are lack of knowledge of the general, do not want to come up with a lot of money to control harmonic, and some enterprises because of the harmonic content is too high, the reactive power compensation can not work routine, the electricity sector is very strictto the reactive power requirements, not up to be fine. Therefore, the owner had to request filtering.Therefore, the market prospects, economic benefits is considerable.
2 active harmonic filtering device
Active harmonic filtering device is developed based on passive filter on the filtering effect, it is good,in the range of reactive power at their rated, the filtering effect is one hundred percent. It is mainly composed of power electronic components circuit with frequency, amplitude, harmonic with which asystem, but the harmonic current and harmonic current offset system in opposite phase. But because of the influence of power electronic components development pressure, limit, the rated current of the high cost, the production is also compared with the passive filter is much more complex, the cost is much higher. The scope of its application is the main power supply system ofthe computer control system, especially the power supply system of office building, plant computer control system. Device for single station, the profit is considerable, but users are generally reluctant to use active filter, the harmonic content, need not be too clean filter, as long as it doesn't harm other appliances will be.
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