Method for controlling three-phase bridge type full-control silicon controlled rectifier based on digital phase-locked loop

Abstract

The invention relates to the technical field of control circuits, in particular to a control method for three-phase bridge type full-control silicon controlled rectifier rectification based on a digital phase-locked loop, which comprises a thyristor full-bridge rectification circuit, a voltage sampling module, a digital controller and a thyristor trigger circuit which are connected in sequence, the digital controller collects the voltage of a three-phase line through the voltage sampling module and obtains a trigger signal through calculation of the digital controller, and the trigger signal triggers conduction of the thyristor full-bridge rectification circuit by controlling the thyristor trigger circuit. According to the method, phase locking is carried out on the trigger pulse according to the equal interval characteristic of the synchronization pulse, the accurate pulse trigger time is ensured, and therefore the accurate alpha control angle is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of control circuits, and in particular to a control method for a three-phase bridge-type fully-controlled silicon-controlled rectifier based on a digital phase-locked loop. Background Art

[0002] The thyristor rectifier circuit utilizes the forward blocking effect of the thyristor. When the thyristor is subjected to a forward voltage, it has the triggering condition to conduct. When the grid voltage is constant, the output voltage is determined by the control angle α. The stability of the control angle α determines the stability of the output voltage of the thyristor rectifier circuit. During the operation of the thyristor rectifier, the waveform distortion caused by the voltage harmonics of the actual grid and the various interference signals in the detection circuit cause the voltage zero-crossing point to jitter, which in turn causes the zero-crossing pulse signal output by the hardware detection to jitter, and finally causes the trigger pulse based on the zero-crossing point to jitter, resulting in unstable output voltage.

[0003] Traditional trigger pulse control: filter and shape the synchronous voltage, output synchronous pulse (voltage zero point), as the time base for generating the α control angle. The time base is required to be stable and strictly synchronized with the zero point of the power grid. The following problems exist:

[0004] 1. The control angle α of traditional pulse control is calculated based on the known voltage cycle. When the grid frequency fluctuates, the control angle α cannot be adjusted in real time with the grid frequency, resulting in inaccurate control.

[0005] 2. When the voltage is distorted or the hardware is disturbed, the synchronization time of the zero-crossing signal is inaccurate and triggered incorrectly, which ultimately affects the α control angle and causes unstable output voltage;

[0006] 3. The zero-crossing detection circuit requires additional filtering and shaping, has a large phase lag, and is more complicated to produce and debug.

[0007] Therefore, a new technical solution is urgently needed to solve this technical problem. Summary of the invention

[0008] The purpose of the present invention is to overcome the above-mentioned problems of the prior art and provide a control method for a three-phase bridge fully-controlled thyristor rectifier based on a digital phase-locked loop, which is used to solve the technical problem in the prior art that the voltage signal waveform is distorted due to grid frequency jitter and grid harmonic interference, resulting in inaccurate voltage zero-crossing position detection or burrs, and ultimately affecting the α control angle, resulting in unstable output voltage.

[0009] The above objectives are achieved through the following technical solutions:

[0010] A control method for a three-phase bridge fully controlled thyristor rectifier based on a digital phase-locked loop, comprising a thyristor full-bridge rectifier circuit, a voltage sampling module, a digital controller and a thyristor trigger circuit connected in sequence, wherein the digital controller collects the voltage of a three-phase line through the voltage sampling module, and calculates a trigger signal through the digital controller, and the trigger signal triggers the conduction of the thyristor full-bridge rectifier circuit by controlling the thyristor trigger circuit;

[0011] The digital controller calculates the trigger signal, specifically:

[0012] The digital controller includes a Clark converter module, a Park converter module, a PLL controller module and a thyristor trigger controller module. The Clark conversion module uses Clark coordinate transformation to obtain voltages Uα and Uβ in a two-phase stationary coordinate system from the voltages Uab, Uac and Ubc of the three-phase line acquired by the voltage sampling module.

[0013] The Park converter module converts the voltages Uα and Uβ in the two-phase stationary coordinate system and the electrical angle θ calculated by the PLL controller module into voltages Ud and Uq in the two-phase rotating coordinate system through Park conversion;

[0014] The PLL controller module calculates the voltages Ud and Uq in the two-phase rotating coordinate system through a digital phase-locked loop technology to obtain the angular velocity ω of the synthesized voltage vector at this time;

[0015] The thyristor trigger controller module obtains the thyristor control trigger signal by using the electrical angle θ, the angular velocity ω and the thyristor conduction angle α.

[0016] Furthermore, the PLL controller module includes a PID controller and an integrator.

[0017] Furthermore, the thyristor conduction angle α is defined as the time when the voltage Uab can trigger the output start, and the range is 0 to 120°.

[0018] Furthermore, the voltage sampling module is an analog-to-digital converter.

[0019] Furthermore, the digital controller is a device with program processing function.

[0020] The control method of a three-phase bridge type fully controlled silicon controlled rectifier based on a digital phase-locked loop provided by the present invention phase-locks the trigger pulse according to the equal interval characteristics of the synchronous pulse, ensuring the accuracy of the pulse triggering timing, thereby ensuring the accuracy of the α control angle. In terms of hardware, only an ADC conversion circuit needs to be added, and the judgment of the voltage angle is directly realized through software, without the need to detect the physical zero-crossing point and the phase-locked loop circuit that tracks the zero-crossing point, which is more cost-effective; the software program processing is more flexible, and the Clark zero-sequence detection, as well as the judgment of the phase angle and angular velocity, are easier to realize abnormal detection such as phase loss, overvoltage and frequency fluctuation. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A flowchart of a control method for a three-phase bridge-type fully-controlled silicon-controlled rectifier based on a digital phase-locked loop according to the present invention;

[0022] Figure 2 It is a flow chart of a digital controller processing a trigger signal in a control method of a three-phase bridge type fully controlled silicon controlled rectifier based on a digital phase-locked loop according to the present invention;

[0023] Figure 3 It is a schematic diagram of the electrical angle θ calculated by the PLL controller module in the control method of the three-phase bridge fully controlled silicon controlled rectifier based on the digital phase locked loop of the present invention;

[0024] Figure 4 A schematic diagram of positive sequence rectification in a control method of a three-phase bridge type fully controlled silicon controlled rectifier based on a digital phase locked loop according to the present invention;

[0025] Figure 5 A circuit diagram of a thyristor rectifier bridge of a thyristor full-bridge rectifier circuit in a control method of a three-phase bridge-type fully-controlled thyristor rectifier based on a digital phase-locked loop according to the present invention;

[0026] Figure 6 for Figure 5 6 output states of the thyristor rectifier bridge;

[0027] Figure 7 The relationship between the phase angle and the conduction angle of the voltage Uab during positive sequence rectification in the control method of the three-phase bridge fully controlled thyristor rectification based on the digital phase-locked loop described in the present invention;

[0028] Figure 8 The relationship between the phase angle and the conduction angle of the voltage Uab during negative sequence rectification in the control method of the three-phase bridge fully controlled thyristor rectification based on the digital phase-locked loop described in the present invention;

[0029] Fig. 9 The present invention provides a flow chart of calculating a thyristor control trigger signal by a thyristor trigger controller module in a control method for a three-phase bridge fully-controlled thyristor rectifier based on a digital phase-locked loop. DETAILED DESCRIPTION

[0030] The present invention is further described in detail below based on the accompanying drawings and embodiments. The described embodiments are only a part of the embodiments of the present invention, rather than all 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.

[0031] like Figure 1 and 5 As shown in the figure, compared with the inconvenience of direct control design of AC signals, this scheme designs a control method for three-phase bridge fully controlled thyristor rectifier based on digital phase-locked loop, directly converts analog voltage signals into digital signals, periodically clacks the data through software, and then calculates the real-time phase angle and angular velocity through the digital phase-locked loop. The program determines the positive and negative phase sequence according to the direction of the angular velocity, adds a 60° offset to the phase angle and calculates the trigger angle, searches for the corresponding trigger state, adjusts the trigger pulse, controls the thyristor, and controls the output voltage by modifying the conduction angle α.

[0032] Specifically, it comprises a thyristor full-bridge rectifier circuit, a voltage sampling module, a digital controller and a thyristor trigger circuit connected in sequence, wherein the digital controller collects the voltage of the three-phase line through the voltage sampling module, and calculates a trigger signal through the digital controller, and the trigger signal triggers the conduction of the thyristor full-bridge rectifier circuit by controlling the thyristor trigger circuit;

[0033] like Fig. 9 As shown, in the digital controller, the angle θ is calculated by a digital phase-locked loop, and a periodic program judgment is performed (the period can be less than 0.1ms) to determine which switch state it belongs to, and trigger the thyristor in the corresponding state, thereby controlling the output voltage of the rectifier bridge.

[0034] The digital controller in this embodiment calculates the trigger signal, specifically:

[0035] The digital controller includes a Clark converter module, a Park converter module, a PLL controller module and a thyristor trigger controller module. The Clark conversion module uses Clark coordinate transformation to obtain voltages Uα and Uβ in a two-phase stationary coordinate system from the voltages Uab, Uac and Ubc of the three-phase line acquired by the voltage sampling module.

[0036] The Park converter module converts the voltages Uα and Uβ in the two-phase stationary coordinate system and the electrical angle θ calculated by the PLL controller module into voltages Ud and Uq in the two-phase rotating coordinate system through Park conversion;

[0037] The PLL controller module calculates the voltages Ud and Uq in the two-phase rotating coordinate system through a digital phase-locked loop technology to obtain the angular velocity ω of the synthesized voltage vector at this time;

[0038] The thyristor trigger controller module obtains the thyristor control trigger signal using the electrical angle θ, the angular velocity ω and the thyristor conduction angle α. Specifically, the thyristor conduction angle α is defined as the time when the voltage Uab can trigger the output start, and the range can be set to 0 to 120°.

[0039] When the input voltage is positive sequence, the thyristor conduction angle α is controlled to be 0°, then the phase angle θ of the corresponding voltage Uab is 60°, and then the voltages Uab, Uac, Ubc, Uba, Uca and Ucb are output in sequence at intervals of 60°, in a cycle.

[0040] like Figures 3 to 8 As shown, the PLL controller module in this embodiment includes a PID controller and an integrator.

[0041] Specifically, the control target of the PLL controller module is to make Uq calculated by the Park converter module = 0, at which time the angle δ between Ud and Uab is 0 (infinitely close to zero), that is, Ud coincides with Uab, and the PLL controller outputs an angular velocity ω; the integral can obtain the angle θ as the real-time phase angle of the Uab line voltage, the angular velocity ω is equal to the input voltage frequency radian, and the sign of the angular velocity ω represents the phase relationship among Uab, Ubc and Uca;

[0042] If it is greater than 0, it means that Uab, Ubc and Uca are in positive order, otherwise they are in reverse order.

[0043] The positive sequence can be based on the real-time angle of Uab as a reference. One counterclockwise circle is 0° to 360°, which is recorded as the electrical angle θ.

[0044] As an optimization of this embodiment, the voltage sampling module may be in the form of, but not limited to, an analog-to-digital converter, etc.

[0045] The digital controller is a device with program processing function, which includes but is not limited to a single-chip microcomputer, a DSP, a FPGA, a Soc, etc.

[0046] The above description is only for illustrating the implementation mode of the present invention and is not intended to limit the present invention. For those skilled in the art, any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A control method for a three-phase bridge fully controlled silicon controlled rectifier based on a digital phase locked loop, characterized in that: It comprises a thyristor full-bridge rectifier circuit, a voltage sampling module, a digital controller and a thyristor trigger circuit connected in sequence, wherein the digital controller collects the voltage of the three-phase line through the voltage sampling module, and calculates a trigger signal through the digital controller, and the trigger signal triggers the conduction of the thyristor full-bridge rectifier circuit by controlling the thyristor trigger circuit; The digital controller calculates the trigger signal, specifically: The digital controller includes a Clark converter module, a Park converter module, a PLL controller module and a thyristor trigger controller module. The Clark conversion module uses Clark coordinate transformation to obtain voltages Uα and Uβ in a two-phase stationary coordinate system from the voltages Uab, Uac and Ubc of the three-phase line acquired by the voltage sampling module. The Park converter module converts the voltages Uα and Uβ in the two-phase stationary coordinate system and the electrical angle θ calculated by the PLL controller module into voltages Ud and Uq in the two-phase rotating coordinate system through Park conversion; The PLL controller module calculates the voltages Ud and Uq in the two-phase rotating coordinate system through a digital phase-locked loop technology to obtain the angular velocity ω of the synthesized voltage vector at this time; The thyristor trigger controller module obtains the thyristor control trigger signal by using the electrical angle θ, the angular velocity ω and the thyristor conduction angle α.

2. A control method for a three-phase bridge fully controlled silicon controlled rectifier based on a digital phase locked loop according to claim 1, characterized in that: The PLL controller module includes a PID controller and an integrator.

3. A control method for a three-phase bridge fully controlled silicon controlled rectifier based on a digital phase locked loop according to claim 2, characterized in that: The thyristor conduction angle α is defined as the time when the voltage Uab can trigger the output start, and the range is 0 to 120°.

4. The control method of a three-phase bridge fully controlled silicon controlled rectifier based on a digital phase locked loop according to claim 1, characterized in that: The voltage sampling module is an analog-to-digital converter.

5. The control method of a three-phase bridge fully controlled silicon controlled rectifier based on a digital phase locked loop according to claim 1, characterized in that: The digital controller is a device with program processing function.

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