Basic Info.
Model NO.
Thyristor controlled reactor
Working Frequency
Low Frequency
Structure of Winding
Multilayer Coil
Nature of Operation
Choke Coil
Structure of Magnetizer
Iron Core Coil
Range of Application
Choke
Inductor Value
Fixed Inductor
Trademark
Jingcheng electric
Transport Package
Wooden Package
Specification
copper or aluminum
Product Description
Thyristor controlled reactor
Thyristor controlled reactor is also called thyristor phase controlled transformer (TCR). Thyristor controlled thyristor is one of the most important components of thyristor controlled thyristor (TCR) in shunt reactor.
The basic single-phase TCR consists of a pair of thyristor valves T1 and T2 connected in series with a linear air core reactor. A pair of thyristors in reverse parallel is like a two-way switch. The thyristor valve T1 is in the positive half of the supply voltage, while the thyristor valve T2 is in the negative half of the supply voltage. The trigger angle of thyristor is calculated from the zero crossing time of voltage between its two ends, and the delay angle of trigger signal varies from 90 ° to 180 °.
Principle
The controllable range of TCR trigger angle α is 90 ° to 180 °. When the trigger angle is 90 °, the thyristor is fully conducting, and the current in TCR is a continuous sinusoidal waveform. When the trigger angle changes from 90 ° to 180 ° the current in TCR is in the form of discontinuous pulse, which is symmetrically distributed in positive half wave and negative half wave. When the trigger angle is 180 degrees, the current decreases to 0. When the trigger angle is less than 90 degrees, a DC component will be introduced into the current, which will destroy the symmetrical operation of the two anti parallel valve branches. Therefore, it is generally adjusted in the range of 90 ° to 180 °. By controlling the trigger delay angle of the thyristor, the current flowing through the reactor can be continuously adjusted from 0 (thyristor blocking) to the maximum value (thyristor full conduction), which is equivalent to changing the equivalent reactance value of the reactor. Once the thyristor is on, the turn off of the current flowing through the thyristor will occur at its natural zero crossing moment, which is called power grid commutation. The TCR operates in the mode of power grid commutation. Once the grid turns on, the phase change of the thyristor can only result in a change in the phase characteristics of the next thyristor cycle.
Effect
The role of TCR is like a variable susceptance. Changing the trigger angle can change the admittance value. Because the AC voltage applied is constant, changing the admittance value can change the fundamental current, which leads to the change of reactive power absorbed by the reactor. However, when the trigger angle exceeds 90 degrees, the current becomes non sinusoidal, and then harmonics are generated. If two thyristors trigger symmetrically at positive half wave and negative half wave, only odd harmonics will be generated. Harmonics can be obtained by Fourier analysis of higher frequency components.
Since controllable capacitive reactive power is required in power system applications, a capacitor is connected in parallel on TCR. The capacitor can be fixed or switchable by mechanical switch or thyristor switch. The main advantages of TCR are the flexibility of control and easy expansion. Different control strategies can be easily implemented, especially those involving external auxiliary signals to significantly improve system performance. Both the reference voltage and current slope can be controlled in a simple way. Because TCR SVC is modular in nature, the capacity expansion can be achieved by adding more TCR modules, of course, on the premise that the capacity of coupling transformer cannot be exceeded.
TCR does not have large overload capacity because its reactor is air core design. If TCR is expected to withstand transient overvoltage, it is necessary to add short-term overload capacity in TCR design, or install additional thyristor switching reactor for use in case of overload.
The response time of TCR is 1.5-3 cycles. The actual response time is a function of measurement delay, TCR controller parameters and system strength.
Operating characteristics
If voltage control is applied to TCR, the normal operation area is compressed into a characteristic curve. This characteristic curve reflects the hard voltage control characteristic of the compensator, which can stabilize the system voltage accurately at% of the voltage set value. Under normal conditions, the controller maintains the node voltage by controlling the inductive reactive power injected into the node by the reactor. When the voltage increases, the operating point will move to the right, and the controller increases the inductive reactive power of the injected node by increasing the trigger angle of the thyristor valve to maintain the node voltage. When the operating point reaches the rightmost end of the control range, the node voltage will not be compensated by the control system after the further increase of the node voltage. Because the reactor of TCR is already in the fully conducting state, the operation point will move upward along the characteristic curve of the corresponding reactor full conduction (α = 90 °). At this time, the compensator operates in the overload range. When the range is exceeded, the trigger control will set ~ currents Limit to prevent damage to the thyristor valve due to overvoltage. On the left side of the characteristic curve, if the node voltage is too low, the compensator will reach the emission limit and the operating point will fall on the under voltage characteristic.
Three phase TCR
A six pulse three-phase TCR consists of three single-phase TCRs connected in a triangle. If the three-phase voltage is balanced, the three reactors are phase, and all thyristors are symmetrically triggered, that is, each phase has the same trigger angle, then symmetrical current pulses will appear in the positive half wave and negative half wave, so only odd harmonics will be generated.
In fact, the parameters of Three-phase Reactors in practice can not be exactly the same. The three-phase supply voltage is not necessarily completely balanced. This imbalance will lead to the generation of non characteristic harmonics, including the third harmonic, which will spread to the line. Under normal conditions, the value of non characteristic harmonics is very small. However, in the case of serious disturbance, the triggering angles of positive and negative half waves may be different, which will lead to the generation of DC component, which is enough to cause the coupling transformer to saturate, thus producing greater harmonic diffusion. In addition to harmonics, a small fundamental current component (0.5% - 2%) also flows in the TCR, which reflects the resistance loss in the TCR winding.
In normal operation, TCR will generate a large number of characteristic harmonics into the power grid, so measures must be taken to eliminate or weaken these harmonics. The common method is parallel filter. The parallel filter is either series LC structure or series LCR structure. These filters are tuned to the 5th and 7th dominant harmonic frequencies, and sometimes 11 and 13 filters are used, or only one high pass filter is used. If the TCR is expected to be controlled by phase, or the condition of network resonance requires TCR to be controlled by phase, then it is necessary to install the third harmonic filter in parallel with TCR.
Another way to reduce the characteristic harmonics injected into the system by TCR is to divide the main TCR into n (n ≥ 2) parallel connected TCRs, and the capacity of each segment TCR is] / N of the whole TCR. In the R1 segment TCR, the trigger angle of only one segment TCR is controlled, and the other segment TCRs are either fully on or off to absorb the specified amount of reactive power. Because the inductance of each segment of TCR is increased by RL times, the capacity of controlled TCR is reduced by N times, and the harmonic generated by controlled TCR is also reduced by N times relative to the rated fundamental current. When the above-mentioned structure is used to reduce the harmonics, the cost will also increase, because this requires more thyristors. In this way, if the TCR has many segments, the segmented TCR will be much more expensive than the non segmented TCR.
12 pulse TCR
As in HVDC system, the harmonic can be greatly reduced when 12 pulse TCR is used. In this structure, two six pulse TCRs are supplied by two groups of three-phase voltages with a phase difference of 30 °. The 12 pulse TCR either requires a special 3-winding transformer with two secondary windings or two primary side connected to the same power transformer. In both cases, one of the secondary side of the transformer is star connected and the other is delta connected.
It was divided into two 6-pulse TCR for analysis. Taking the primary A-phase fundamental line current as the reference vector, the vector diagram of fundamental, 5th and 7th line currents generated by TCR of a star to satellite connected transformer at its primary side is presented. Similarly, we can also get the vector diagram of fundamental, 5th and 7th line currents generated by TCR of star delta connected transformer on its primary side. As the primary side a phase fundamental current vector is taken as the reference vector, the direct comparison of the two groups of vector diagrams shows that the two groups of 6-pulse TCR generate the same phase fundamental current on the primary side of the transformer. In addition, the valve side current and the primary side line current of the two groups of transformers have been made the same in the design of the transformer, so the amplitude of the fundamental current generated at the primary side is also equal. For the fifth and seventh harmonic currents, and higher order 16 (2n + 1) ± 1, n = 0, 1, 2 In terms of harmonic current, the amplitude of harmonic current generated by two groups of 6-pulse TCR on the primary side of transformer is equal, but the phase is just opposite, and the two cancel each other. Therefore, the line current in the primary side will only contain 12n ± 1 (13 integer) harmonics, which greatly reduces the requirements for harmonic filters.
The reduction of harmonic content in 12 pulse TCR greatly reduces the requirement of filter. As a result, it is not necessary to use the filter with 5 and 7 tuning times as the 6-pulse TCR, but the high pass filter is enough. Similarly, the reduction of harmonics is accompanied by an increase in the cost. In view of the need to increase the number of thyristors, the special double secondary winding transformer and the complicated trigger sequence increase the cost. Another advantage of 12 pulse TCR is the increased reliability. If one of the six pulse TCR units fails, the other TCR unit can continue to operate, although only half of the reactive capacity is available. Moreover, 12 pulse TCR has higher overload capacity than 6-pulse TCR.
TCR with pulse number greater than 12 has not been put into practical use, although it can greatly reduce harmonics. Because the TCR with more than 12 pulses becomes too complex and expensive, for example, a transformer with three secondary windings is needed for a TCR with 18 pulses. In addition, it is difficult to achieve the required precision of trigger control to ensure symmetrical trigger.
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311121, Hangzhou, Zhejiang, China
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Company Introduction:
Hangzhou Jingcheng electric Equipment Co., Ltd. (Brief name: Jingcheng Electric). Was founded in 1998, registered capital is 60 million yuan. We mainly produces 110kV and below series reactor, shunt reactor, magnetic control reactor, current limiting reactor, etc After years of development, we has gradually combined with other reactive power compensation related products: Capacitor, reactive power compensation controller, discharge coil, SVG, vacuum Contactors and other related reactive power compensation equipment for unified sales and production, in the reactor and reactive power compensation industry to create a domestic leading level, and gradually step out of the country to the world. Our company has specialized in the research of reactive power compensation device for more than 20 years, and has accumulated valuable experience in the industry. We are one of the first domestic manufacturers to develop and manufacture magnetic control reactor, and is also one of the advanced manufacturers of large capacity magnetic control shunt reactor in China.
Jingcheng electric has three production bases, which are located in Cangqian science and Technology Park in Hangzhou, Sandun Industrial Zone in Hangzhou and Deqing high tech Industrial Zone in Huzhou. Jingcheng electric covers an area of more than 120 mu, with a construction area of 400000 square meters, and has nearly 240 employees;
The advantages of our company are reliable product quality, preferential price and excellent service quality. We hope you and I can work together to deliver more reliable, high-quality and clean electric energy for the power transmission and distribution system. Each kW of electricity saved by us for the world will make a huge share for environmental protection. I hope you and I can create a better future together!
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