A flexible DC high-frequency resonance suppression device

Abstract

The present invention provides a flexible direct current high-frequency resonance suppression device, comprising a fast bypass switch branch, a mechanical bypass switch branch and an LC circuit, wherein the fast bypass switch branch, the mechanical bypass switch branch and the LC circuit are connected in parallel and then connected in series in the main circuit of the flexible direct current transmission, wherein the main circuit of the flexible direct current transmission is connected in series with a suppression circuit, wherein the suppression circuit comprises a frequency comparator, a control signal generator and a voltage-controlled oscillator, and an input signal and an industrial frequency signal are connected in series on the branch of the frequency comparator. The present invention can effectively suppress the flexible direct current high-frequency resonance by connecting the suppression circuit in series with the main circuit of the flexible direct current transmission, and compare the magnitude relationship between the input signal and the industrial frequency signal by the frequency comparator, and send a feedback signal to the magnitude of the input signal, so as to facilitate the adjustment of the value of the input signal at any time, and realize the resonance suppression effect of controlling the flexible direct current high frequency more accurately and finely.

Description

Technical Field

[0001] The invention relates to the technical field of direct current resonance suppression, and in particular to a flexible direct current high-frequency resonance suppression device. Background Art

[0002] In recent years, high-frequency oscillation has occurred many times in actual flexible DC transmission projects. When high-frequency oscillation occurs, the voltage and current of the flexible DC transmission system are distorted, containing high-order harmonics with large amplitudes, which will cause damage to the system equipment and affect the normal operation of the system. In order to improve the stability and reliability of the project, especially to improve the stability of the application scenario of wind farm grid connection, it is urgent to find a method to suppress high-frequency oscillation.

[0003] There are many studies on flexible DC high-frequency resonance suppression devices in the prior art. For example, a flexible DC transmission series high-frequency resonance suppression device with application announcement number CN216290208 U is a passive circuit that does not require control, has a wide range of harmonic suppression, high stability, and is easy to put into operation. It is put into use when it is judged that there is a resonance risk or resonance has occurred during operation, and its power frequency impedance is small when it is put into use, which has no effect on the normal operation of the flexible DC transmission system and only has a suppressive effect on medium and high frequencies. The design ideas of the two topologies of the RLC circuit are that when the current flowing through the resonance suppression device is the power frequency, the resistance in the resonance device does not play a significant role, and when the current flowing through the resonance suppression device is medium and high frequency, the resonance device presents a resistance characteristic, and the fast bypass switch branch is used in conjunction with the mechanical switch branch for easy insertion and withdrawal.

[0004] However, there are still the following deficiencies. From the above statements, it can be seen that the high-frequency resonance suppression device lacks a device for comparing the input signal of the flexible DC frequency with the industrial frequency signal, and lacks a device for issuing negative feedback based on the size relationship between the input signal and the industrial frequency signal, thereby being unable to achieve accurate and fine control over the resonance suppression effect of the flexible DC high frequency. Summary of the invention

[0005] The object of the present invention is to provide a flexible DC high-frequency resonance suppression device to solve the problems raised in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A flexible direct current high-frequency resonance suppression device comprises a fast bypass switch branch, a mechanical bypass switch branch and an LC circuit, wherein the fast bypass switch branch, the mechanical bypass switch branch and the LC circuit are connected in parallel and then connected in series in a main circuit of a flexible direct current transmission, wherein the main circuit of the flexible direct current transmission is connected in series with a suppression circuit, wherein the suppression circuit comprises a frequency comparator, a control signal generator and a voltage-controlled oscillator, wherein an input signal and an industrial frequency signal are connected in series on a branch of the frequency comparator, an output end of the frequency comparator is connected in series with an input end of a first capacitor, an output end of the first capacitor is connected in series with an input end of the control signal generator, an input end of the voltage-controlled oscillator is connected in series with an output end of the first capacitor, the suppression circuit is connected in parallel with a feedback circuit, an input end of the feedback circuit is connected with an output end of the voltage-controlled oscillator, and an output end of the feedback circuit is connected with an input end of the frequency comparator.

[0008] Preferably, the LC circuit includes a second capacitor and a reactor, and the second capacitor and the reactor are connected in series.

[0009] Preferably, the fast bypass switch is a bidirectional thyristor.

[0010] Preferably, the mechanical bypass switch is a contactor or a circuit breaker.

[0011] Preferably, the first capacitor is a high-frequency bypass capacitor.

[0012] Preferably, the second capacitor is a low-frequency bypass capacitor.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] The present invention can effectively suppress the high-frequency resonance of flexible direct current by connecting a suppression circuit in series in the main loop of flexible direct current transmission, specifically, the output end of a frequency comparator is connected in series with the input end of a first capacitor, the output end of the first capacitor is connected in series with the input end of a control signal generator, the input end of a voltage-controlled oscillator is connected in series with the output end of the first capacitor, the input end of a feedback circuit is connected with the output end of the voltage-controlled oscillator, and the output end of the feedback circuit is connected with the input end of the frequency comparator. The frequency comparator compares the magnitude relationship between an input signal and an industrial frequency signal, and sends a feedback signal to the magnitude of the input signal, so as to facilitate the adjustment of the value of the input signal at any time, and realize the resonance suppression effect of controlling the high frequency of flexible direct current more accurately and finely. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the electrical connection of the overall structure of the present invention.

[0016] In the figure: 1 fast bypass switch branch, 2 mechanical bypass switch branch, 3-LC circuit, 31 second capacitor, 32 reactor, 4 suppression circuit, 41 frequency comparator, 42 control signal generator, 43 voltage controlled oscillator, 44 first capacitor, 5 feedback circuit. DETAILED DESCRIPTION

[0017] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] Example:

[0019] See also Figure 1 , the present invention provides a technical solution:

[0020] A flexible DC high frequency resonance suppression device, such as Figure 1 As shown, it includes a fast bypass switch branch 1, a mechanical bypass switch branch 2 and an LC circuit 3. The fast bypass switch branch 1, the mechanical bypass switch branch 2 and the LC circuit 3 are connected in parallel and then connected in series in the main circuit of the flexible DC transmission. The fast bypass switch is a bidirectional thyristor, the mechanical bypass switch is a contactor or a circuit breaker, and the LC circuit 3 includes a second capacitor 31 and a reactor 32. The second capacitor 31 and the reactor 32 are connected in series.

[0021] like Figure 1 As shown, the main circuit of the flexible direct current transmission is connected in series with a suppression circuit 4, which includes a frequency comparator 41, a control signal generator 42 and a voltage-controlled oscillator 43. The branch of the frequency comparator 41 is connected in series with an input signal f1 and an industrial frequency signal f0. The output end of the frequency comparator 41 is connected in series with the input end of the first capacitor 44, the output end of the first capacitor 44 is connected in series with the input end of the control signal generator 42, the input end of the voltage-controlled oscillator 43 is connected in series with the output end of the first capacitor 44, the suppression circuit 4 is connected in parallel with the feedback circuit 5, the input end of the feedback circuit 5 is connected to the output end of the voltage-controlled oscillator 43, the output end of the feedback circuit 5 is connected to the input end of the frequency comparator 41, the first capacitor 44 is a high-frequency bypass capacitor, and the second capacitor 31 is a low-frequency bypass capacitor.

[0022] In this embodiment, by connecting the suppression circuit 4 in series with the main circuit of the flexible direct current transmission, specifically, the output end of the frequency comparator 41 and the input end of the first capacitor 44 are connected in series, the output end of the first capacitor 44 and the input end of the control signal generator 42 are connected in series, the input end of the voltage-controlled oscillator 43 and the output end of the first capacitor 44 are connected in series, the input end of the feedback circuit 5 is connected to the output end of the voltage-controlled oscillator 43, and the output end of the feedback circuit 5 is connected to the input end of the frequency comparator 41. By comparing the input signal f1 with the power frequency signal f0, the magnitude of the input signal f1 and the power frequency signal f0 can be known. When the input signal f1 is less than or equal to the power frequency signal f0, the low-frequency current flows into the output end of the main circuit through the second capacitor 31 and the reactor 32, the second capacitor 31 allows the low-frequency DC current to pass through, and the high-frequency DC current cannot pass through; when the input signal When f1 is greater than the power frequency signal f0, the high-frequency current passes through the first capacitor 44, the first capacitor 44 allows high-frequency DC current to pass through, but low-frequency DC current cannot pass through, and then flows into the control signal generator 42, the control signal generator 42 outputs a voltage control signal, and the voltage controls the voltage-controlled oscillator 43 to output the signal to the feedback circuit 5, and the feedback circuit 5 then outputs the feedback signal f2 to the frequency comparator 41, and the control input signal f1 is reduced, and the reduced input signal f1 is then input to the control signal generator 42 and the voltage-controlled oscillator 43, and this cycle is repeated, which can effectively suppress the flexible DC high-frequency resonance, and compare the magnitude relationship between the input signal f1 and the power frequency signal f0, and send a feedback signal f2 for the magnitude of the input signal f1, so as to facilitate the adjustment of the value of the input signal f1 at any time, and realize the resonance suppression effect of controlling the flexible DC high frequency more accurately and finely.

[0023] In this embodiment, the frequency comparator 41 adopts the LM358 comparator, which has a wide range of applications and high reliability; the control signal generator 42 is LM61-SPT-HDX-801, which can be used for multiple purposes (including voltage, current, and resistance) and has both output and measurement functions; protection circuits are designed for each function to effectively avoid damage to the instrument due to misoperation, and the instrument is reliable and durable; the voltage-controlled oscillator 43 adopts the model KV708C, which has a large frequency range and a voltage control range of ±50 to ±200ppm, a wide range of applications, and reliable operation.

[0024] In this embodiment, when the suppression circuit 4 is put into operation, the reactor 32 is connected in series with the second capacitor 31 and then connected in parallel with the first capacitor 44. When the power frequency signal f0 is in a state of approximate series resonance, its power frequency impedance is small and has no effect on the normal operation of the flexible DC transmission system. When a high-frequency current flows through the system, the equivalent impedance on the reactor 32 is very large, and the high-frequency current mainly flows through the first capacitor 44. The connection between the suppression circuit 4 and the feedback circuit 5 has a suppressive effect on the high frequency.

[0025] In this embodiment, the fast bypass switch K is composed of a bidirectional thyristor group. When the flexible DC high-frequency resonance suppression device needs to be put into operation, the fast bypass switch K is triggered, the mechanical bypass switch Ks is cut off, and after the mechanical bypass switch Ks is in place, the trigger pulse of the fast bypass switch K is turned off, and the suppression circuit 4 and the feedback circuit 5 are put into operation; when the suppression circuit 4 and the feedback circuit 5 need to be cut off, the fast bypass switch K is triggered, the mechanical bypass switch Ks is put into operation, and after the mechanical bypass switch Ks is in place, the trigger pulse of the fast bypass switch K is turned off, and the suppression circuit 4 and the feedback circuit 5 are withdrawn. The fast bypass switch branch 1 and the mechanical bypass switch branch 2 are used together to enable the flexible DC high-frequency resonance suppression device to be conveniently and quickly put into operation and withdrawn.

[0026] The working principle of the flexible DC high-frequency resonance suppression device is as follows:

[0027] When in use, the input signal f1 is compared with the power frequency signal f0 to know the magnitude relationship between the input signal f1 and the power frequency signal f0. When the input signal f1 is less than or equal to the power frequency signal f0, the low frequency current flows into the output end of the main circuit through the second capacitor 31 and the reactor 32, and the second capacitor 31 allows the low frequency DC current to pass through, but the high frequency DC current cannot pass through; when the input signal f1 is greater than the power frequency signal f0, the high frequency current passes through the first capacitor 44, and the first capacitor 44 allows the high frequency DC current to pass through, but the low frequency DC current cannot pass through, and then flows into the control signal generator 42, and the control signal generator 42 outputs a voltage control signal, and outputs the signal to the feedback circuit 5 through the voltage control voltage controlled oscillator 43. , the feedback circuit 5 then outputs the feedback signal f2 to the frequency comparator 41, controls the input signal f1 to be reduced, and compares the reduced input signal f1 with the power frequency signal f0. If the input signal f1 is greater than the power frequency signal f0, it is input to the control signal generator 42 and the voltage controlled oscillator 43. If it is less than or equal to the power frequency signal f0, it flows out of the output end of the main circuit through the first capacitor 44 and the reactor 32. In this way, the flexible DC high-frequency resonance can be effectively suppressed, and the magnitude relationship between the input signal f1 and the power frequency signal f0 can be compared. The feedback signal f2 is sent out for the magnitude of the input signal f1, so as to facilitate the adjustment of the value of the input signal f1 at any time, and realize the resonance suppression effect of controlling the flexible DC high frequency more accurately and finely.

[0028] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A flexible direct current high-frequency resonance suppression device, comprising a fast bypass switch branch (1), a mechanical bypass switch branch (2) and an LC circuit (3), wherein the fast bypass switch branch (1), the mechanical bypass switch branch (2) and the LC circuit (3) are connected in parallel and then in series in a main circuit of a flexible direct current transmission, characterized in that: The main circuit of the flexible direct current power transmission is connected in series with a suppression circuit (4), the suppression circuit (4) comprising a frequency comparator (41), a control signal generator (42) and a voltage-controlled oscillator (43); an input signal and an industrial frequency signal are connected in series on a branch of the frequency comparator (41); an output end of the frequency comparator (41) is connected in series with an input end of a first capacitor (44); an output end of the first capacitor (44) is connected in series with an input end of the control signal generator (42); an input end of the voltage-controlled oscillator (43) is connected in series with an output end of the first capacitor (44); the suppression circuit (4) is connected in parallel with a feedback circuit (5); an input end of the feedback circuit (5) is connected to an output end of the voltage-controlled oscillator (43); and an output end of the feedback circuit (5) is connected to an input end of the frequency comparator (41).

2. A flexible DC high-frequency resonance suppression device according to claim 1, characterized in that: The LC circuit (3) includes a second capacitor (31) and a reactor (32), and the second capacitor (31) and the reactor (32) are connected in series.

3. The flexible DC high-frequency resonance suppression device according to claim 1, characterized in that: The fast bypass switch is a bidirectional thyristor.

4. The flexible DC high-frequency resonance suppression device according to claim 1, characterized in that: The mechanical bypass switch is a contactor or a circuit breaker.

5. The flexible DC high-frequency resonance suppression device according to claim 1, characterized in that: The first capacitor (44) is a high frequency bypass capacitor.

6. The flexible DC high-frequency resonance suppression device according to claim 2, characterized in that: The second capacitor (31) is a low-frequency bypass capacitor.

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