Power Quality Distributed Compensation and Quality Improvement Method for Crystal Growth Furnace

Abstract

The invention discloses a power quality distributed compensation and quality improvement method for crystal growth furnace. The method comprises the following steps: a distributed local compensation system is formed by connecting an active filter to the inlet of each crystal growth furnace in parallel and connecting the communication terminal of the active filter to the centralized management andcontrol platform of crystal growth furnace power quality through a 485 communication bus; the distributed local compensation system is formed by connecting the communication terminal of the active filter to the centralized management and control platform of crystal growth furnace power quality. The centralized management and control platform of crystal furnace power quality collects the detectiondata and compensation data of each active filter, and completes the coordinated control. Each of the active filters monitors and adaptively switches each crystal growth furnace; In addition, the distributed local compensation system eliminates the interference signals between active filters by monitoring the bus and real-time compensation by active filters. The invention discloses a method for distributing compensation and quality promotion of crystal growth furnace power quality, wherein, an active filter connected in parallel with the growth furnace is used for local compensation, and the overall compensation is carried out through an active filter of a switch cabinet, so as to improve the production quality.

Description

technical field [0001] The invention relates to a power supply compensation system for a crystal growth furnace, in particular to a distributed compensation and quality improvement method for power quality of a crystal growth furnace, and belongs to the technical field of power supply compensation systems for a crystal growth furnace. Background technique [0002] For crystal growth furnaces, high-quality power quality is very important. The current harmonics on the bus will eventually conduct into the transformer. In addition to increasing the loss of the transformer, excessive harmonic currents will cause voltage fluctuations in the transformer and affect the control of the crystal furnace. Effect; distorted voltage and current will reduce the rectification efficiency and quality, and affect the quality of the crystal all the time; there are many uncontrollable rectification devices on the crystal growth furnace site, and the external input 380V / 50Hz power frequency power s...

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Problems solved by technology

[0002] For crystal growth furnaces, high-quality power quality is very important. The current harmonics on the bus will eventually conduct into the transformer. In addition to increasing the loss of the transformer, excessive harmonic currents will cause voltage fluctuations in the transformer and affect the control of the crystal furnace. Effect; distorted voltage and current will reduce the rectification efficiency and quality, and affect the quality of the crystal all the time; there are many uncontrollable rectification devices on the crystal growth furnace site, and the external input 380V / 50Hz power frequency power supply is uncontrollable through the three-phase bridge. It is rectified into a DC voltage, which is converted into a frequency-variable AC voltage through capacitor filtering and high-power transistor switching elements; in the rectification circuit, the waveform of the input current is an irregular rectangular wave, and the waveform is decomposed into fundamental waves and For each harmonic, the harmonic order is usually 6n±1 high-order harmonics, and the high-order harmonics will interfere with the input power supply system; due to voltage distortion caused by harmonics, current amplification exceeds the rated operating voltage and current of components, Therefore, the anti-harmonic is mainly to improve the anti-harmonic interference ability of compensation equipment by improving the withstand voltage and current parameters of components such as capacitors and switches. However, the physical parameters of components have certain limits. It will amplify the harmonic current and send it back to the power grid, resulting in frequent damage to components, so this method cannot fundamentally solve the problem of harmonic pollution; harmonic suppression is mainly achieved by matching it in series in the capacitance compensation circuit The reactor simultaneously improves the physical parameters of the capacitor and the switch, thereby effectively filtering out part of the harmonic current in the power grid, generally about 30%. In addition, when the capacitor is switched on, the harmonic current will not be amplified, and it will be sent back to the power grid to increase pollution. This method can not only effectively suppress harmonics, but also ensure the normal operation of compensation equipment; this method of harmonic control is currently the most economical and most commonly used effective method, but in the case of serious harmonic pollution, this method cannot be used from To completely solve the harmonic pollution situation at the root, it is necessary to tailor-made passive filters or active filters; passive filters refer to filters composed of passive components such as resistor R / inductor L / capacitor C, to A low-impedance path is formed for a certain harmonic or higher harmonics to achieve the effect of filtering harmonics; passive filtering devices are currently a widely used harmonic control method, which is specially designed according to the desired harmonic order Tailor-made, using the tuning principle of inductance and capacitance, the harmonics are trapped in the filter to reduce the injection into the power grid; features: simple structure, relatively mature technology, wide application fields, lower cost than active filter Low, compared with the harmonic suppression method, the cost is higher, but the harmonic filtering effect is greatly affected by the grid impedance and component quality parameters, the filtering parameters are prone to drift, the self-adaptation is poor, and the filtering is not thorough enough, so frequent system Correction of parameters, or redesign; the active filter scheme is a new type of special equipment for power harmonic control made of modern power electronics technology and digital signal processing technology based on high-speed DSP devices

By detecting the current and other signals in the system, a compensation current equal to the amplitude of the harmonic current of the grid and opposite in polarity is generated and injected into the grid to compensate or offset the harmonic current and actively eliminate power harmonics; the characteristic is that in principle, It can basically completely filter out the harmonics in the system, and has the advantages of no inductor, small size, and light weight: but the technology is relatively immature, the price is too high, limited by hardware, the capacity is small, and the application occasions are limited; based on active power The harmonic compensation principle of the filter is that the active power filter is connected in parallel in the low-voltage power distribution system with harmonic loads, which can quickly and real-time track and compensate the dynamically changing harmonic current. The principle is: APF series active The power filter collects the harmonic current of the system through CT, quickly calculates and extracts the content of each harmonic current through the controller, generates a harmonic current command, and generates a compensation current that is equal to the amplitude of the harmonic current and opposite to the direction of the harmonic current through the power actuator. And inject it into the power system, so as to offset the harmonic current generated by the nonlinear load; in the prior art, the centralized compensation scheme of the crystal growth furnace in the APF is currently the most common APF compensation installation method, and its basic principle is shown in the figure below. In the power distribution main transformer room, centrally configure the APF power distribution cabinet and install the APF in a unified manner; the advantage of centralized compensation is that the project volume is small, the installation and management are convenient, and the installation location is close to the transformer, which has a better compensation effect on the transformer and is easier to meet the needs of the power grid. Assessment requirements; therefore, centralized compensation is the first choice of many enterprises; but it cannot improve product quality. Since the on-site crystal furnaces are installed in series, each crystal furnace will generate harmonics, and centralized compensation in the power distribution room cannot effectively reduce Harmonics on the bus, especially the crystal furnace far away from the transformer; so parallel compensation is not suitable for this system

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