Gear adjusting method and device for phase-controlled arc suppression coil

Abstract

The invention discloses a gear adjusting method and device of a phase-controlled arc suppression coil, belongs to the technical field of power grid control, and particularly provides a gear adjusting method of an arc suppression coil in a mode of taking three-phase voltage as a reference. The method comprises the following steps: acquiring UA phase-locked output through three-phase voltage phase locking without depending on zero-cross detection at two ends of an arc suppression coil, sampling a cycle wave U0 according to a UA phase-locked output cycle, simultaneously acquiring an initial phase of the UA corresponding to the cycle wave, acquiring the initial phase of the U0 corresponding to the cycle wave through DFT (Discrete Fourier Transform), then acquiring a phase difference between the UA and the U0, and changing a conduction angle position which is originally found through U0 zero-cross detection into a conduction angle position which is not found through U0 zero-cross detection. The position of a conduction angle is found on UA phase-locked output, and gear adjustment can be reliably carried out when harmonic current is large and zero-sequence voltage waveform distortion is serious.

Description

Technical Field

[0001] The invention belongs to the technical field of power grid control, and specifically refers to a gear adjustment method and device for a phase-controlled arc suppression coil. Background Art

[0002] The traditional triggering method of the thyristor conduction angle is to control the compensation current of the arc extinguishing coil by controlling the thyristor conduction angle, obtain the U0 voltage through the voltage transformer (PT), and then obtain the zero crossing point of U0 through zero crossing detection. The delay time of the target conduction angle is calculated according to the zero crossing point, and then the delay triggers the thyristor to conduct at this moment, generating inductive current to achieve the purpose of arc extinguishing. Therefore, the accuracy of zero crossing detection affects the accuracy of thyristor control.

[0003] The current conducted by the thyristor contains a large number of odd harmonics, mainly the third and fifth harmonics. The filter winding forms a harmonic low-impedance circuit to prevent a large amount of harmonic current from entering the power grid. If the third and fifth harmonics generated by the grid grounding capacitor and the primary leakage reactance of the phase-controlled arc suppression coil resonate, a large number of third and fifth harmonics will enter the power grid, causing the U0 voltage waveform sampled by the PT to be severely distorted, resulting in inaccurate zero-crossing detection and inaccurate thyristor control. Summary of the invention

[0004] In view of the above situation, in order to overcome the defects of the prior art, the present invention provides a gear adjustment method and device for a phase-controlled arc suppression coil, which is used to solve the problem of inaccurate control of the phase-controlled arc suppression coil caused by voltage waveform distortion at both ends of the phase-controlled arc suppression coil.

[0005] The technical solutions adopted in this application are as follows:

[0006] The present invention provides a gear adjustment device for a phase-controlled arc extinguishing coil, which comprises an arc extinguishing coil, a driving circuit, and a gear adjustment device composed of a processor, wherein the gear adjustment device is used to select an adjustment mode of the arc extinguishing coil and perform data processing;

[0007] The arc extinguishing coil includes a primary winding and two secondary windings, and the secondary winding includes a filter winding and a control winding;

[0008] The primary winding is connected between the transformer neutral point and ground;

[0009] The first secondary winding is connected to a filter circuit, wherein the filter circuit comprises a third harmonic filter branch and a fifth harmonic filter branch respectively connected in parallel at two ends of the first secondary winding, and the third harmonic filter branch and the fifth harmonic filter branch are respectively a capacitor and an inductor branch connected in series;

[0010] The second secondary winding is connected to a thyristor control loop composed of two reverse-parallel thyristors. The gear adjustment device is independent of the zero-crossing point of the voltage at both ends of the arc extinguishing coil and outputs pulses to the processor through phase-locked output. The processor outputs a control signal to the drive circuit. The drive circuit connects the two thyristors of the thyristor control loop and then controls the conduction state of the thyristor.

[0011] Preferably, the adjustment method of the gear adjustment device specifically comprises the following steps:

[0012] S1: The three-phase voltages UA, UB, and UC of the power grid are sampled through a voltage transformer (PT), and a reference voltage based on the three-phase voltage is set. The stable voltage in the power grid is used as the reference voltage, preferably the positive sequence component of the three-phase voltage. The three-phase voltage is then subjected to PLL phase-locking processing, and the output after phase locking is , get the phase-locked output waveform, and take the phase-locked output as the reference phase;

[0013] S2: The voltage U0 is obtained by sampling the primary voltage of the arc suppression coil through a voltage transformer (PT), and the fundamental wave extraction processing (such as Fourier transform, etc.) of the U0 voltage is performed to obtain the initial phase of the fundamental wave of U0, and the phase difference between the reference voltage and the U0 voltage is calculated. ;

[0014] S3: The controller sends out the target conduction angle θcmd, and after proportional-integral processing, the reference conduction angle θref is obtained. The conduction angle position is found in the phase-locked output waveform: Angle, send pulses to control the thyristor to conduct.

[0015] Preferably, the specific steps of S3 include the following:

[0016] S3.1 takes the phase-locked output as a reference and calculates the reference output angle at the beginning of each cycle. When the processor sends a pulse to control the target conduction angle to be θcmd (the range of θcmd is π / 2~π), the initial value angle is selected to obtain the reference conduction angle θref by proportional integration to the target conduction angle θcmd. The initial value angle range is π / 2~π. It is preferred to use the initial value of π / 2 to integrate the target conduction angle θcmd to obtain the reference conduction angle θref.

[0017] S3.2 makes the vertical coordinate of the phase-locked output in the current cycle A pulse is sent out to control the thyristor output, and then the above process is repeated at the beginning of each cycle (that is, when the vertical coordinate of the phase-locked output is 0), so that the output angle is output from π / 2 to the target conduction angle.

[0018] Preferably, the phase difference is performed at least 3 times in each phase-locked output cycle. Calculation update.

[0019] By adopting the above scheme, the beneficial effects achieved by the present invention are as follows:

[0020] 1. The method using three-phase voltage as reference is not dependent on the zero-crossing point of the voltage at both ends of the arc suppression coil, thus avoiding the control problem caused by inaccurate zero-crossing point detection caused by voltage distortion at both ends of the arc suppression coil.

[0021] 2. The UA phase-locked output is obtained through three voltage phase-locking to obtain a reference reference, and the fundamental wave initial phase of U0 is obtained through fundamental wave extraction processing of U0, and then the phase difference between UA and U0 is obtained, so as to solve the problem that the waveform is easily distorted on U0 and it is difficult to find the target conduction angle. The target conduction angle search on U0 is transferred to the more stable UA phase-locked output for target conduction angle control, avoiding the problems caused by the use of U0 zero-crossing detection in the traditional process; the pulse sending method from 90° to the target conduction angle proportional integral is close to the coil from full conduction to control it, which can effectively avoid the resonance of the coil and the capacitance to the ground.

[0022] 3. This solution can also reliably adjust the gear when the harmonic current is large and the zero-sequence voltage waveform is severely distorted, ensuring the control accuracy and stability of the arc suppression coil. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The overall flow chart of a method for adjusting the gear position of a phase-controlled arc-extinguishing coil provided in this scheme;

[0024] Figure 2 It is the output waveform after the three-phase voltage is phase-locked in this scheme;

[0025] Figure 3 A schematic diagram of a gear adjustment device for a phase-controlled arc suppression coil provided in this scheme. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0027] Embodiment 1:

[0028] Please refer to Figure 1 As shown, this embodiment provides a method for adjusting the gear position of a phase-controlled arc suppression coil, comprising the following steps:

[0029] S1: Obtain the three-phase voltages UA, UB, and UC of the power grid through PT sampling, set a reference voltage based on the three-phase voltage, and then perform PLL phase-locking processing on the three-phase voltage. The output after phase locking is , get the phase-locked output waveform, and take the phase-locked output as the reference phase;

[0030] Among them, the stable voltage in the power grid is used as the reference voltage. In this embodiment, the positive sequence component of the three-phase voltage is preferably used as the reference voltage;

[0031] S2: The voltage U0 is obtained by sampling the primary voltage of the arc suppression coil through the voltage transformer PT, and the fundamental wave of the U0 voltage is extracted to obtain the initial phase of the fundamental wave of U0, and the phase difference between the reference voltage and the U0 voltage is calculated. ;

[0032] S3: The controller sends out the target conduction angle θcmd, and after proportional-integral processing, the reference conduction angle θref is obtained. The conduction angle position is found in the phase-locked output waveform: Angle, send pulses to control the thyristor to conduct.

[0033] Combination Figure 1 As shown, UA, UB, UC are the three-phase voltages of the power grid obtained by PT sampling, and PLL is phase-locked processing. is the output of the three-phase voltage after phase locking, U0 is the voltage sampling value of the PT on the primary side of the arc suppression coil, DFT is discrete Fourier processing, Based on phase locking, the phase difference between U0 and UA is obtained through DFT processing after sampling one cycle. θcmd is the target conduction angle issued by the processor. It is a proportional integral process, the initial value is 90°, and θref is the reference conduction angle after proportional integral process. is to find the angle in the phase-locked output waveform. Send pulses to control the thyristor to conduct.

[0034] Furthermore, the three-phase voltages UA, UB, and UC (or the voltage between two phases) are used for phase-locking processing to obtain the UA phase-locked output as follows: Figure 2 . Figure 2 The output waveform of a three-phase voltage after phase locking is provided. The horizontal axis is time and the vertical axis is radians. The frequency is 50Hz and the amplitude is 2π.

[0035] Figure 2 The period of the sawtooth wave is recorded as Ta, and the amplitude is 2π. Then, based on the phase-locked output waveform as the time axis, a cycle of U0 voltage data (i.e. t~t+Ta) is collected at a certain time t, and the collection time length is Ta; the initial phase of UA corresponding to the cycle is the ordinate value of the phase-locked output at time t , the initial phase of the fundamental wave of the frequency U0 is obtained through fundamental wave extraction processing (such as Fourier transform) , and then obtain the phase difference between the frequency UA and U0 (% is the remainder calculation).

[0036] In this embodiment, theoretically, the phase difference at each sampling point can be updated by the above method. However, considering the processor performance, based on the phase-locked output, the phase difference is calculated at least 3 times in each phase-locked output cycle. Calculation update.

[0037] The phase-locked output waveform and phase difference are obtained by the above method , taking the phase-locked output as the reference, at the beginning of each cycle, that is, when the vertical coordinate of the phase-locked output is 0 (in actual use, at the sampling point when the phase-locked output value changes from 2π to a value close to 0), calculate the reference output angle: when the controller sends a pulse to control the target conduction angle to θcmd, the range of θcmd is π / 2~π, the reference conduction angle θref is obtained by integrating the target conduction angle θcmd with an initial value of π / 2 in a proportional integral manner.

[0038] Make the phase-locked output ordinate in the current cycle A pulse is sent out to control the thyristor output, and then the above process is repeated at the beginning of each cycle (that is, when the vertical coordinate of the phase-locked output is 0), so that the output angle is output from π / 2 to the target conduction angle.

[0039] like Figure 3 As shown, a schematic diagram of a gear adjustment device for a phase-controlled arc extinguishing coil is provided. This embodiment includes an arc extinguishing coil, a drive circuit, and a gear adjustment device composed of a processor, and the gear adjustment device is used to select the adjustment method of the arc extinguishing coil and perform data processing.

[0040] Wherein, the arc extinguishing coil includes a primary winding and two secondary windings, and the secondary winding includes a filter winding and a control winding;

[0041] The primary winding is connected between the transformer neutral point and ground;

[0042] The first secondary winding is connected to a filter circuit, wherein the filter circuit comprises a third harmonic filter branch and a fifth harmonic filter branch respectively connected in parallel at two ends of the first secondary winding, and the third harmonic filter branch and the fifth harmonic filter branch are respectively a capacitor and an inductor branch connected in series;

[0043] The second secondary winding is connected to a thyristor control loop composed of two reverse-parallel thyristors. The gear adjustment device is independent of the zero-crossing point of the voltage at both ends of the arc extinguishing coil and outputs pulses to the processor through phase-locked output. The processor outputs a control signal to the drive circuit. The drive circuit connects the two thyristors of the thyristor control loop and then controls the conduction state of the thyristor.

[0044] As can be seen from the figure, UA, UB, UC are the three-phase voltages of the power grid obtained by PT sampling, CX is the system capacitance to ground, U0 is the voltage sampling value of the PT on the primary side of the arc suppression coil, T1 is the phase-controlled arc suppression coil; SCR is a thyristor; L3, L5 are the 3rd and 5th filter inductors, C3, C5 are the 3rd and 5th filter capacitors.

[0045] Figure 3 In the shown embodiment, L3 is connected in series with C3, L5 is connected in series with C5, the two parts are connected in parallel on the arc suppression coil filter winding, and the thyristor is connected on the coil control winding; the arc suppression coil primary side voltage measurement PT sampling obtains the primary side voltage U0, and the three voltages UA, UB, and UC are obtained through PT, the sampling is input into the processor system D, and the control signal is output to the drive circuit to drive and control the thyristor to turn on.

[0046] It should be noted that although the embodiments of the present invention have been shown and described, for ordinary technicians in this field, without departing from the purpose of the invention, structural methods and embodiments similar to the technical solution are designed without creativity and should all fall within the scope of protection of the present invention.

Claims

1. A gear adjustment device for a phase-controlled arc extinguishing coil, comprising an arc extinguishing coil, a driving circuit and a gear adjustment device composed of a processor, wherein the gear adjustment device is used to select and process data of an adjustment mode of the arc extinguishing coil, wherein the arc extinguishing coil comprises a primary winding and two secondary windings, wherein the secondary winding comprises a filter winding and a control winding, and wherein: The primary winding is connected between the transformer neutral point and ground; The first secondary winding is connected to a filter circuit, wherein the filter circuit comprises a third harmonic filter branch and a fifth harmonic filter branch respectively connected in parallel at two ends of the first secondary winding, and the third harmonic filter branch and the fifth harmonic filter branch are respectively a capacitor and an inductor branch connected in series; The second secondary winding is connected to a thyristor control loop composed of two reverse parallel thyristors. The gear adjustment device does not rely on the zero-crossing point of the voltage at both ends of the arc extinguishing coil, and outputs pulses to the processor through phase locking. The processor outputs a control signal to the drive circuit. The drive circuit is connected to the two thyristors of the thyristor control loop and then controls the conduction state of the thyristor. The adjustment method of the gear adjustment device of the phase-controlled arc-extinguishing coil comprises the following steps: S1: The three-phase voltages UA, UB, and UC of the power grid are obtained by sampling the voltage transformer, a reference voltage based on the three-phase voltage is set, and then the three-phase voltage is subjected to PLL phase-locking processing. The output after phase locking is , get the phase-locked output waveform, and take the phase-locked output as the reference phase; S2: The voltage on the primary side of the arc suppression coil is sampled by the voltage transformer to obtain the U0 voltage, the fundamental wave extraction process of the U0 voltage is performed to obtain the initial phase of the fundamental wave of U0, and the phase difference between the reference voltage and the U0 voltage is calculated. ; S3: The controller sends out the target conduction angle θcmd, and after proportional-integral processing, the reference conduction angle θref is obtained. The conduction angle position is found in the phase-locked output waveform: Angle, send pulses to control the thyristor to conduct; The specific steps of S3 include the following: S3.1 uses the phase-locked output as the reference phase and calculates the reference output angle at the beginning of each cycle. When the processor sends a pulse to control the target conduction angle to be θcmd, the range of θcmd is π / 2~π, and the initial value angle is selected to obtain the reference conduction angle θref by proportional integral processing to the target conduction angle θcmd. The initial value angle range is π / 2~π; S3.2 makes the vertical coordinate of the phase-locked output in the current cycle A pulse is sent out to control the thyristor output, and then the above process is repeated at the beginning of each cycle, so that the output angle is close to the target conduction angle from the initial value angle. The stable voltage in the power grid is used as the reference voltage.

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