CN2533603Y - Electric power filtering and dynamic reactive compensation device - Google Patents

Abstract

The utility model discloses a power filtering and dynamic reactive compensation device and consists of a current transformer, a voltage transformer, a controller, a filter, a thyristor switching reactor group and a reducing transformer, wherein, the filter is formed by the parallel connection of a plurality of filtering branch circuits which are formed by the serial connection of a filtering reactor and a filtering capacitor; the thyristor switching reactor group is formed by the parallel connection of a plurality of branch circuits of thyristor reactors formed by the serial connection of a reactor and a thyristor alternative current switch formed by the reverse parallel connection of two thyristors; the thyristor switching reactor group is in parallel connection with the filter through the reducing transformer; a control pole of the thyristor is connected with the controller; the current transformer and the voltage transformer are connected between a power net bus and the controller. The power filtering and dynamic reactive compensation device of the utility model has the advantages of good filtering effect, being able to avoid the economic loss of railway and power departments and eliminating the harms or disturbances caused to power users by high harmonics and voltage fluctuation and is suitable for electrified railways and other power distribution networks with harmonics and fluctuating wavy load.

Description

A power filter and dynamic reactive power compensation device

technical field

The utility model relates to a filter and power compensation device. Specifically, it is a power filter and dynamic reactive power compensation device for electrified railways. It is also suitable for power distribution systems with harmonic or fluctuating loads in power supply departments, industrial and mining enterprises and institutions.

Background technique

As we all know, the traction load of electrified railway fluctuates greatly, that is, when the train passes, the traction load is large; when no train passes, the traction load is small. The high-power rectifying device on the locomotive is another great harmonic source. At present, the shunt capacitor reactive power compensation devices on the electrified railway traction network are almost all static, that is, they are all fixed-capacity shunt capacitor compensation devices. They cannot automatically and dynamically adjust according to the reactive power load of the power grid, especially when the railway traffic volume is small, light load or no load, the overcompensation of reactive power is very prominent, which will seriously affect the power quality. According to reports, just taking China's electrified railways as an example, the power department is fined about 300 million yuan every year. It can be seen that due to the imbalance of reactive power, it will cause huge economic losses to the railway sector. In addition, since this static shunt capacitor compensation device can only absorb part of the third harmonic in the traction grid, there are still some third harmonics and higher harmonics such as the fifth and seventh in the traction grid that cannot be filtered out. not good. Therefore, in the traction power grid and related power grids, there will be serious voltage fluctuations, which will not only affect the normal operation of locomotives and other electrical equipment, but also cause some third harmonics and fifth, seventh and other higher harmonics in the traction power grid. Diffusion through the grid.

In addition, in the power distribution system of industrial and mining enterprises and institutions, the start and stop of large loads, electric arc furnace smelting and the operation of power electronic equipment will cause voltage fluctuations, reactive power changes or transmit high-order harmonics to the distribution network. Hazard or disturbance to electrical equipment, instrumentation, communication systems and many other electricity users.

Contents of the invention

The purpose of the utility model is to provide a power filtering and dynamic reactive power compensation device. Using this device, the filter effect is good, can ensure the normal operation of locomotives and other electrical equipment, and can avoid economic losses in railway and other electrical departments, and can eliminate the impact of high-order harmonics and voltage fluctuations on electrical equipment, instruments, communication Hazards or disturbances to the system and other power users.

Above-mentioned purpose of the utility model is realized by following technical solutions:

The power filter and dynamic reactive power compensation device of the utility model is composed of a current transformer, a voltage transformer, a controller, a filter, a thyristor switching reactor group and a step-down transformer. Said filter is formed by parallel connection of several filter branches, wherein the filter branch is formed by series connection of filter reactor and filter capacitor. The thyristor switching reactor group is composed of several thyristor-reactor branches connected in parallel. The thyristor-reactor branch is composed of a thyristor AC switch and a reactor in series, and the thyristor AC switch is composed of two thyristors. formed in parallel. The thyristor switching reactor group is connected in parallel with the filter through the step-down transformer. The control pole of the thyristor is connected with the controller to control the on and off of the thyristor AC switch. The secondary coils of current transformers and voltage transformers are connected to the controller, while the primary coils of the other gates are connected to the grid bus.

In the power filter and dynamic reactive power compensation device of the present invention, the filter is formed by parallel connection of several filter branches, and the filter branch is formed by series connection of filter reactors and filter capacitors. , Its impedance is very small, so it can filter out harmonics, and the filtering effect is good, eliminating the harm or interference caused by high-order harmonics and voltage fluctuations to power equipment, instruments, communication systems and other power users. As for the fundamental wave, they all exhibit capacitance, which is a capacitive compensation device. When the load of the traction network or distribution network increases, the voltage drops, and the power factor tends to decrease, the filter is equivalent to a shunt capacitor compensation device for the fundamental wave, which can compensate the reactive power required by the grid and increase the voltage, so that The power factor is improved.

Since the power filtering and dynamic reactive power compensation device of the present invention is provided with a thyristor switching reactor group, when the traction network and the distribution network have no load or the load is very small, the filter is still a parallel capacitor compensation device, which will make Overvoltage occurs due to the increase of grid voltage, and too much capacitive reactive power is sent back to the grid. At this time, the redundant reactive power can be absorbed by the thyristor switching reactor group, so that the voltage is basically stable, the reactive power is balanced, and the power factor is kept within the set range. It can ensure the normal operation of locomotives and other electrical equipment, and avoid economic losses in railway and other electrical departments.

Because the utility model adopts the thyristor switching reactor group for control, the control is relatively simple, the failure rate is small, and the cost is low.

Due to the use of thyristor AC switches, it can be switched frequently and has a fast response speed, which is suitable for adjusting fluctuating loads.

Description of drawings

The accompanying drawing is a schematic diagram of the power filtering and dynamic reactive power compensation device of the present invention.

Detailed ways

As shown in the accompanying drawings, the power filtering and dynamic reactive power compensation device of the present invention is composed of a current transformer CT, a voltage transformer VT, a controller 1, a filter 4, a thyristor switching reactor group 3 and a step-down transformer T constitute. in:

The controller 1 is composed of an analog-to-digital conversion circuit, a computer, a signal output circuit and a man-machine dialogue device, and a current transformer CT and a voltage transformer VT are connected between the controller and the grid.

The filter 4 is composed of three (or several) filter branches connected in parallel, which are connected to the bus supplying power to the load in the running state. Wherein, each filter branch is formed by a filter reactor FL and a filter capacitor C connected in series.

The thyristor switched reactor group 3 is formed by parallel connection of multiple thyristor-reactor branches, and each thyristor-reactor branch is formed by a thyristor AC switch 2 and a reactor SR connected in series. The thyristor AC switch 2 is composed of two thyristors THY connected in antiphase and parallel.

Thyristor switching reactor group 3 is connected in parallel with filter 4 through step-down transformer T. The control pole of the thyristor THY in the thyristor AC switch 2 is connected to the controller 1 so as to control the on and off of the thyristor AC switch 2 .

The power filtering and dynamic reactive power compensation device of the utility model is in the running state, the current and voltage of the power grid are respectively detected by the current transformer CT and the voltage transformer VT, and provided to the controller 1, and the reactive power is calculated by the controller 1 And power factor, and judge the level of grid voltage.

The filter 4 is used to filter out high-order harmonics generated by electric locomotives or high-power electric power and electronic equipment in the traction network or distribution network. At the same time, it can also filter out the harmonics generated by the operation of the thyristor-reactor branch.

Thyristor switched reactor group 3 plays the role of an adjustable inductance, and the thyristor AC switch 2 quickly switches the reactor SR to adjust the inductance stepwise, thereby changing the size of its output inductive reactive power. The step-down transformer T is used to reduce the voltage of the thyristor AC switch 2 and the reactor SR, thereby reducing the manufacturing cost.

After the controller 1 calculates the current and voltage of the traction grid or distribution grid sent by the current transformer CT and voltage transformer VT, it sends a signal to the thyristor AC switch 2 to control 1 to 8 reactors SR Switching, so that the grid quickly returns to the preset voltage and power factor range.

The impedance of each branch of the filter 4 is very small relative to each higher harmonic, so the harmonic can be filtered out. As for the fundamental wave, all of them exhibit capacitance, which is a capacitive compensation device. When the load of the traction network or distribution network increases, the voltage drops, and the power factor tends to decrease, the filter 4 is equivalent to a shunt capacitor compensation device for the fundamental wave, which can compensate the reactive power required by the grid and increase the voltage. Improve the power factor. When the traction network and distribution network have no load or a small load, the filter is still a shunt capacitor compensation device, which will increase the grid voltage and cause overvoltage, and excessive capacitive reactive power will be sent back to the grid. At this time, the redundant reactive power can be absorbed by the thyristor switching reactor group, so that the voltage is basically stable, the reactive power is balanced, and the power factor is kept within the set range.

The reactor group is composed of reactors SR with different capacities, and the capacity difference can be designed as proportional series. For example, for a reactor group with a total reactive capacity Q _L of 3000kvar, the capacity of each reactor is divided into 200, 400, 800, and 1600kvar, and the combined total is 0, 200, 400, 600, 800, 1000, 1200, 1400, 1600 , 1 800, 2000, 2200, 2400, 2600, 2800 and 3000kvar sixteen grades, the difference δ _L is only 200kvar, that is δ _L /Q _L ≈6.67%. The controller 1 can find out the most appropriate combination according to the status of the reactive power of the grid, and put in several reactors SR at one time, so as to more accurately meet the requirement of absorbing capacitive reactive power and realizing the basic balance of inductive reactive power and capacitive reactive power. Thereby eliminating reactive power transfer, maintaining voltage stability, and effectively reducing grid loss.

Claims (1)

1. electric filtering and dynamic reactive compensation device is characterized in that being made of current transformer (CT), voltage transformer (VT), controller (1), filter (4), thuristor throw-in and throw-off reactor group (3) and step-down transformer (T); Said filter (4) is formed in parallel by some filter branch, and filter branch wherein is in series by filter reactor (FL) and filtering capacitor (C); Thuristor throw-in and throw-off reactor group (3) is formed in parallel by some thyristor reactor branch roads, thyristor reactor wherein props up route one thyristor interchange switch (2) and reactor (SR) is in series, and it then is to be formed by two thyristors (THY) reverse parallel connection that thyristor exchanges switch (2); Thuristor throw-in and throw-off reactor group (3) is in parallel by step-down transformer (T) and filter (4); The control utmost point of thyristor (THY) and controller (1) join; The secondary coil of current transformer (CT) and voltage transformer (VT) is connected with controller (1), and their primary winding then is connected on the electrical network bus.

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