Reactive compensation and three-phase balance device, and quick response algorithm thereof

Abstract

The invention discloses a reactive compensation and three-phase balancing device, and a quick response algorithm thereof. The device comprises a compensation system comprising a plurality of compensation systems and a control system, the control system comprises an AD sampling module and a switching control module, and the control system comprises a communication module. According to the reactivecompensation and three-phase balance device, and the quick response algorithm thereof, the quick tracking compensation of the reactive power is completed in a low cost to improve the power factor andcomplete the balance of the three-phase current, and therefore, the reactive compensation and three-phase balancing device and the quick response algorithm thereof are suitable for electric energy quality treatment of an industrial device, especially for the scene with frequent reactive demand fluctuation and the unbalance three-phase current.

Description

technical field [0001] The invention belongs to the technical field of power electronics, and in particular relates to a reactive power compensation and three-phase balance device and a fast response algorithm, more specifically a uSVG based on an embedded combined reactive power compensation and three-phase balance device and a fast response algorithm . Background technique [0002] In recent years, the global production and manufacturing industry has been re-arranged, and China's industrial manufacturing industry has a strong momentum. The stamping, welding, spraying and other technological processes in the traditional manufacturing process and the use of robots in the new manufacturing industry will all cause relatively high reactive power demand. Large fluctuations, if there is no fast-tracking reactive power support, will cause large flicker changes in the system voltage, thereby affecting the quality of production products. For example, when many welding machines are ...

AI Technical Summary

Problems solved by technology

[0002]In recent years, the global production and manufacturing industry has been re-arranged, and China's industrial manufacturing industry has a strong momentum. The use of robots in the industry will cause large fluctuations in reactive power demand. If there is no fast-tracking reactive power support, it will cause large flickering changes in system voltage, thereby affecting the quality of production products.

For example, when many welding machines are installed between phases of a three-phase system, because the power levels of the welding machines installed between each phase are different and they work at different times, the magnitude and phase of the three-phase current are very different during the working process, resulting in three-phase imbalance. ;At the same time, the electric welding machine works as an intermittent impact load, and the continuous time of the working process is mostly 0.1-1 second. During this process, the current is very large, and the reactive power demand is also large. If the capacitive reactive power support of the system is insufficient during this period , will cause a serious drop in the system voltage, which will affect the welding temperature of the electric welding machine, resulting in a decline in welding quality and defective products.

Another example is that due to the application of a large number of robots in automated assembly equipment, there are a large number of inverter-driven operating mechanisms in the production process. Most of these inverters are 6-pulse or 12-pulse rectifier bridges, with low power factors and large demand changes.

In short, the demand for reactive power of modern production equipment is huge and fluctuates frequently. If there is no suitable equipment to quickly provide reactive power on site, it will inevitably bring impact to the grid voltage, and the power quality problem of abnormal voltage will affect the equipment. Especially the normal operation of precision equipment

Considering the above problems, in order to meet the needs of the site, a variety of reactive power compensation and three-phase unbalance control devices have been developed. The advanced dynamic reactive power compensation equipment highlights its superiority, but it also has its inherent disadvantages: among them, the cost of thyristor switching capacitive reactor is low, but its switching speed is very slow under the traditional operation mode, especially when it is put into operation. Both are greater than 0.02 seconds, especially when fluctuating reactive power demand cannot be tracked; and the active dynamic reactive power compensation device uses fast IGBT power electronic switches, which can track fluctuating loads very quickly and can output unbalanced current , but the cost of power electronic switches is too high, large-capacity applications are unrealistic, and the on-off process of power electronic switches will bring high-order harmonics to the power grid, so although there are technical advantages, the application is still subject to many restrictions

Due to the cost of hybrid compensation equipment with this structure, the capacity of the active part is usually very small, usually accounting for less than 10% of the capacity of the whole cabinet. The timing difference part has a limited control function on the three-phase unbalance

In a sense, mixed compensation is a measure to deal with large-capacity fluctuations in on-site reactive power demand, and it is also an irresistible move, but it does not improve much in terms of speed and increases the complexity of the system

[0003] On the other hand, in the traditional thyristor switching capacitor products, all rely solely on the hardware circuit to obtain the zero-crossing point of the voltage across the thyristor switch to select the input timing, because the judgment of the zero-crossing point by the hardware circuit is relatively rough, so this method can only be used Ensure that the voltage across the thyristor is as small as possible when switching on, and it is impossible to really avoid the inrush current when switching on. What's more, because of the effect of the internal discharge resistance of the capacitor, the timing of capacitor switching in this way is usually at the moment when the instantaneous value of the system voltage is low. , due to the inherent characteristics of the capacitor current, that is, the input of the capacitor is just at the peak value of the steady-state current of the capacitor. It takes a period of transient process to transition to a stable sinusoidal current. If the input capacity is too large at the same time, this transition process is easy to cause system oscillation, which deviates from the real function of compensation; and the removal of compensation branch, the traditional The equipment does not judge the voltage, that is: as long as the controller gives the IO command to set low, the thyristor drive signal will be set low, and it will be automatically turned off when the next current crosses zero (the peak value of the system voltage at this time), and this point has It may be the positive peak point of the system voltage or the negative peak point of the system voltage, so the phase cannot be determined at the next input

In addition, because there is no dedicated discharge circuit on the capacitor, it is only discharged by the internal safety discharge resistor (with a large resistance value), so it takes a long time for the hardware to regain the zero-crossing point

To sum up, the traditional capacitor switching method can neither realize fast switching nor smooth current input without impact.

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