Reactive power compensation device with zero impact current in operation

Abstract

The utility model discloses a reactive power compensation device with zero impact current during operation, and mainly relates to the field of reactive power compensation. Alternating-current power grid voltage continuously changes, voltage at two ends of a capacitor cannot suddenly change, and when the voltage at two ends of the capacitor is zero and the power grid voltage is at a peak value, great impact current is generated. The device comprises a transformer, a photoelectric coupler, a silicon controlled rectifier and a relay. The device is connected to two sides of a switch through a transformer to detect power grid voltage and capacitor voltage, the switch is controlled to be switched on by utilizing an optocoupler output level when the two voltages are equal, and the capacitor is connected in parallel into a power grid for reactive compensation. In order to ensure the rapidness and accuracy of switching, the silicon controlled rectifier with quick response is adopted for switching, and after the silicon controlled rectifier is closed, the silicon controlled rectifier is bypassed through a relay, so that the problem of heat dissipation during long-term work is solved. The design of the whole system not only improves the switching accuracy and response speed, realizes zero impact current during operation, but also prolongs the service life of the device.

Description

Technical Field

[0001] This utility model relates to the field of reactive power compensation, and in particular to solving the problem of inrush current when a reactive power compensation device is put into operation. Background Technology

[0002] Reactive power compensation devices are crucial equipment in power systems used to improve power quality and increase the power factor. Common types include parallel capacitors and synchronous condensers. Among them, parallel capacitor reactive power compensation is widely used due to its advantages such as economy, low loss, and ease of maintenance. However, the AC grid voltage is constantly changing, while the voltage across the capacitor cannot change abruptly. Therefore, when the voltage across the capacitor is zero and the grid voltage is at its peak, the switching of traditional capacitors will generate a very large charging current, i.e., an inrush current, which will interfere with the grid and reduce the lifespan of switching equipment.

[0003] Traditional circuit breakers and contactors have inconsistent operating times, typically ranging from tens of milliseconds. However, for industrial frequency AC power, a cycle is completed in 20 milliseconds. This means that the relay might close at the point of maximum voltage, and the mechanical vibration of the relay contacts during operation can also cause voltage discontinuities upon closure. Therefore, traditional circuit breakers and contactors suffer from the problem of not being able to quickly engage.

[0004] To reduce switching losses, a reactive power compensation device with accurate voltage detection and rapid switching action is needed to achieve zero inrush current during commissioning. Utility Model Content

[0005] To address the aforementioned problems, this utility model provides a reactive power compensation device with zero inrush current during commissioning. The technical solution of this utility model is as follows:

[0006] A reactive power compensation device with zero inrush current during commissioning is provided. The primary side of the transformer is connected to both sides of the switching switch to detect the voltage at both ends of the power grid and the capacitor. The optocoupler outputs a level based on the high or low voltage of the secondary side of the transformer to control the thyristor switch and determine whether to connect the parallel capacitor. Two relays are added at the thyristor.

[0007] Through the above technical solution, the device can accurately detect voltage, improve the accuracy and response speed of switching, and achieve zero inrush current during commissioning.

[0008] Furthermore, the primary winding of the transformer is connected to both sides of the switching switch to detect the voltage of the power grid and the capacitor, and control the output of the optocoupler.

[0009] By employing the above technical solution, and by finding the moment when the grid voltage and capacitor voltage are equal, excessive inrush current can be avoided.

[0010] Furthermore, when the voltage difference between the power grid and the capacitor detected on the secondary side of the transformer is close to zero, its forward current is insufficient to light up the photodiode. The optocoupler maintains a low output level, thereby triggering the thyristor to close at the moment closest to zero voltage difference. When the voltages of the power grid and the capacitor are inconsistent, the voltage on the secondary side of the transformer also begins to rise or fall. At this time, the photodiode conducts, the optocoupler outputs a high level, and the thyristor switch is not engaged.

[0011] The above technical solution allows for accurate control of switch operation using an optocoupler.

[0012] Furthermore, the thyristor switch is extremely fast, completing its action in approximately 1.7 μs after receiving a signal, and the control circuit is relatively simple.

[0013] Through the above technical solutions, the fast-response thyristor switch can solve the problem that traditional circuit breakers and contactors cannot quickly achieve the desired connection speed.

[0014] Furthermore, the relay bypasses the thyristor after it is closed, and then disconnects the thyristor's path.

[0015] The above technical solution solves the heat dissipation problem of the thyristor during long-term operation.

[0016] In summary, this invention proposes a reactive power compensation device with zero inrush current during commissioning. This device detects the grid voltage and capacitor voltage, and switches on when they are equal, connecting the capacitor in parallel to the grid to initiate reactive power compensation. To ensure rapid and accurate commissioning, a fast-response thyristor is used for switching, and a relay bypasses the thyristor after it closes, solving the heat dissipation problem during long-term operation. The overall system design not only improves the accuracy and response speed of switching, achieving zero inrush current during commissioning, but also extends the service life of the devices, demonstrating promising application prospects and economic benefits. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a reactive power compensation device with zero impact current during commissioning, according to the present invention.

[0018] Figure 2 This is a flowchart illustrating the working process of the reactive power compensation device with zero inrush current during operation of this utility model. Detailed Implementation

[0019] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present utility model. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments.

[0020] like Figure 1 The diagram shown is a schematic diagram of this utility model, which includes a transformer, an optocoupler, a thyristor, and a relay.

[0021] The primary side of the transformer is connected to both sides of the switching switch to detect the voltage across the power grid and the capacitor.

[0022] The optocoupler controls the thyristor switch based on the high or low output level of the transformer secondary voltage, thereby determining whether to connect the parallel capacitor.

[0023] Two relays are added to the thyristor to bypass it after the thyristor has been operating for too long.

[0024] like Figure 2 The diagram shown is a flowchart of the process of this utility model.

[0025] The system measures the voltage across the power grid and the capacitor. The primary winding of the transformer is connected to both sides of a switching switch to detect the voltage across the grid and the capacitor. When the voltages across the primary winding are equal (i.e., the voltage difference across the primary winding is 0), the voltage across the secondary winding is also 0. At this time, the photodiode is not conducting, and the optocoupler outputs a low level. When the voltages across the grid and the capacitor are inconsistent, the voltage across the secondary winding of the transformer begins to rise or fall. When the voltage exceeds a certain value, the photodiode conducts, and the optocoupler outputs a high level. When the voltages across the grid and the capacitor are equal, the thyristor switch is activated, connecting the capacitor in parallel to the AC grid and initiating reactive power compensation.

[0026] Traditional circuit breakers and contactors have inconsistent operating times, typically ranging from tens of milliseconds. However, for industrial frequency AC power, a cycle completes in 20 milliseconds, potentially causing the relay to close at its highest voltage point. Furthermore, mechanical vibrations in the relay contacts during operation can lead to voltage discontinuities upon closure. Therefore, traditional circuit breakers and contactors cannot quickly engage. To address this issue, fast-response, mechanically inert thyristor devices are used for capacitor switching. Thyristors offer extremely fast switching speeds, completing their operation approximately 1.7µs after receiving a signal, and the control circuitry is relatively simple and ready for immediate use.

[0027] Because the voltage drop of the thyristor is relatively large, approximately 1.2V, its power consumption is also high under high current conditions, thus requiring a heat sink for cooling. During reactive power compensation, the capacitor remains connected for a short period after being switched off, causing the thyristor to continuously heat up during operation. This not only increases power consumption but also raises the overall system temperature due to the high installation density in the reactive power compensation cabinet, reducing the lifespan of the components. Therefore, two relays are added to bypass the thyristor after it closes, thus disconnecting its path. This solves the heat dissipation problem of the thyristor during long-term operation.

[0028] In summary, this invention, through precise voltage detection and rapid switching action, not only improves the accuracy and response speed of switching and achieves zero inrush current during commissioning, but also extends the service life of the device.

Claims

1. A reactive power compensation device with zero inrush current during commissioning, characterized in that, include: A thyristor switch and a relay, wherein the thyristor switch is connected between the power grid and the capacitor, and two relays are connected in parallel at the switch; A transformer, wherein the primary side of the transformer is connected to both sides of a thyristor switch, and the secondary side of the transformer is connected in series with a resistor (R1) and in parallel with a resistor (R2); An optocoupler, wherein the input terminal of the optocoupler is connected to the secondary side of the transformer, the optocoupler receives electrical signals, and the output terminal of the optocoupler outputs a level to control the switching of a thyristor switch; A photodiode is connected to the optocoupler via resistors (R3, R4) and the photodiode.

2. The reactive power compensation device with zero inrush current during commissioning as described in claim 1, characterized in that, When the voltage difference between the grid and the capacitor detected on the secondary side of the transformer is close to zero, its forward current is insufficient to light up the photodiode. The optocoupler maintains a low output level, thereby triggering the thyristor to close at the moment closest to zero voltage difference. When the voltages of the power grid and the capacitor are inconsistent, the voltage on the secondary side of the transformer also begins to rise or fall. At this time, the photodiode is turned on, the optocoupler outputs a high level, and the thyristor switch is not engaged.

3. The reactive power compensation device with zero inrush current during commissioning as described in claim 1, characterized in that, The relay closes after the thyristor has been operating for a long time, bypassing the thyristor, and then shuts off the thyristor circuit to prevent the thyristor from overheating.

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