Method for controlling the thyristor triggering angle of transformer

Abstract

This application relates to the technical field of transformers and discloses a method for controlling the thyristor trigger angle of a transformer. The transformer includes first and second thyristors connected to the first tap and the load, and third and fourth thyristors connected to the second tap and the load. The method includes: obtaining the error current between the target load current and the current load current, and calculating the load error voltage; when the target load voltage is less than or equal to the first threshold voltage, calculating the error trigger angle by #imgabs0# and adjusting the trigger angles of the first and second thyristors; when the target load voltage is greater than the first threshold voltage and less than or equal to the second threshold voltage, calculating the error trigger angle by #imgabs1# and adjusting the trigger angles of the third and fourth thyristors; ΔV is the error voltage, V1 and V2 are the first and second threshold voltages, α1 is the trigger angle of the first and second thyristors, and α2 is the trigger angle of the third and fourth thyristors. This application realizes stable and reliable load current control and reduces the calculation amount.

Description

Technical Field

[0001] The present application relates to the technical field of transformers, and in particular to a method for controlling a thyristor triggering angle of a transformer. Background Art

[0002] A transformer is a static electrical device used to transform AC voltage and current to transmit AC power. It realizes power transmission based on the principle of electromagnetic induction. It is widely used in power transmission, electrical equipment and electronic devices. It is one of the core components of modern power systems. A single-phase transformer is mainly composed of two coil windings (primary winding (or coil) and secondary winding (or coil)) and an iron core. In a single-phase transformer, a thyristor is connected to the secondary circuit of the transformer. The output voltage of the transformer is adjusted according to the trigger angle (or conduction angle) of the thyristor, thereby controlling the power supply to the downstream load. Silicon controlled rectifier (SCR), also known as thyristor, is a power electronic device used to control high-power circuits. It has a three-terminal four-layer structure, which can control the flow of current through an external trigger signal. It is a controllable rectifier device.

[0003] In the application of adjusting the angle of the thyristor of the single-phase transformer to control the load power or load current, in order to reduce harmonics and improve the power factor, the output voltage value of the secondary side is differentiated by increasing the tap on the secondary side of the single-phase transformer. When the load power or load current value is small, the thyristor at the low-voltage tap on the secondary side of the transformer is controlled to work. When the load power or load current value is large, the thyristors at the low-voltage tap and high-voltage tap on the secondary side of the transformer are controlled to work at the same time to reduce harmonics and improve the power factor.

[0004] In the existing control, when the trigger angle of the thyristor is controlled with the load current as the target, the trigger angle of the thyristor is directly adjusted by the difference between the target load current and the current load current. Since the load current value and the trigger angle are not proportional, the adjustment speed and stability vary greatly when the current trigger angle value is different. This algorithm cannot be implemented in situations where the load current is large and the stability of the load current is required to be very high.

[0005] This section is intended to provide a background or context for understanding the embodiments of the present application and is for reference only. The applicant should not be considered to admit that this section belongs to the prior art that has been disclosed before the filing date of the present application. Summary of the invention

[0006] The purpose of the present application is to provide a method for controlling the thyristor trigger angle of a transformer to achieve stable and reliable load current control of the transformer.

[0007] The present application discloses a method for controlling a thyristor triggering angle of a transformer, wherein the transformer comprises a first thyristor and a second thyristor connected in parallel between a first tap and a resistive load, and a third thyristor and a fourth thyristor connected in parallel between the second tap and the resistive load, and the method comprises:

[0008] Obtaining an error current between a target load current and a current load current, and calculating an error voltage of the resistive load according to the error current;

[0009] When the target load voltage is less than or equal to the first threshold voltage, the formula is used Calculating an error trigger angle, where Δθ is the error trigger angle, V1 is the first threshold voltage, α1 is the trigger angle of the first thyristor and the second thyristor, ΔV is the error voltage, and adjusting the trigger angles of the first thyristor and the second thyristor according to the error trigger angle;

[0010] When the target load voltage is greater than the first threshold voltage and less than or equal to the second threshold voltage, the formula is used. The error trigger angle is calculated, where V2 is the second threshold voltage, α2 is the trigger angle of the third thyristor and the fourth thyristor, and the trigger angle of the third thyristor and the fourth thyristor is adjusted according to the error trigger angle.

[0011] In a preferred example, adjusting the trigger angles of the first thyristor and the second thyristor according to the error trigger angle includes: adjusting the trigger angles of the first thyristor and the second thyristor to α1-Δθ.

[0012] In a preferred example, adjusting the trigger angles of the third thyristor and the fourth thyristor according to the error trigger angle includes: adjusting the trigger angles of the third thyristor and the fourth thyristor to α2-Δθ.

[0013] In a preferred example, when the target load voltage is less than or equal to a first threshold voltage, the first thyristor and the second thyristor are turned on, and the third thyristor and the fourth thyristor are turned off.

[0014] In a preferred example, when the target load voltage is greater than the first threshold voltage and less than or equal to the second threshold voltage, the first thyristor and the second thyristor are fully turned on, and the third thyristor and the fourth thyristor are turned on.

[0015] In a preferred example, the trigger angles of the first thyristor and the second thyristor are 0°.

[0016] In a preferred embodiment, a proportional-integral regulation method is used to calculate the error voltage of the resistive load according to the error current, and the error voltage , where Kp is the proportional gain, Ki is the integral gain, and ΔI is the error current.

[0017] In a preferred example, the cathode of the first thyristor is connected to one end of the resistive load, and the anode is connected to the first tap; the anode of the second thyristor is connected to one end of the resistive load, and the cathode is connected to the first tap.

[0018] In a preferred example, the cathode of the third thyristor is connected to one end of the resistive load, and the anode is connected to the second tap; the anode of the fourth thyristor is connected to one end of the resistive load, and the cathode is connected to the second tap.

[0019] In a preferred example, the output voltage at the first tap is smaller than the voltage at the second tap, wherein the first threshold voltage is the output voltage at the first tap, and the second threshold voltage is the output voltage at the second tap.

[0020] In the implementation of the present application, the error voltage ΔV is calculated by the error current ΔI of the target load current and the current load current, and the error trigger angle Δθ to be adjusted is calculated by the error voltage ΔV and according to the current thyristor trigger angle α. Specifically, when the target load voltage is less than or equal to the output voltage at the first tap, the formula is used. Calculate the error trigger angle and adjust the trigger angle of the thyristor connected to the first tap; when the target load voltage is greater than the output voltage at the first tap and less than or equal to the output voltage at the second tap, use the formula The error trigger angle is calculated, and the trigger angle of the thyristor connected to the second tap is adjusted, V1 and V2 are the output voltages at the first and second taps, α1 is the current trigger angle of the thyristor connected to the first tap, and α2 is the current trigger angle of the thyristor connected to the second tap. The present application can achieve stable and reliable load current control and greatly reduce the amount of calculation.

[0021] The various technical features disclosed in the above invention content, the various technical features disclosed in the various embodiments and examples below, and the various technical features disclosed in the drawings can be freely combined with each other to form various new technical solutions (these technical solutions should be deemed to have been recorded in this specification), unless such combination of technical features is technically infeasible. For example, in one example, feature A+B+C is disclosed, and in another example, feature A+B+D+E is disclosed, and features C and D are equivalent technical means that play the same role. Technically, only one of them can be used, and it is impossible to use them at the same time. Feature E can be combined with feature C technically. In this case, the solution of A+B+C+D should not be deemed to have been recorded because it is technically infeasible, while the solution of A+B+C+E should be deemed to have been recorded. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the circuit structure of a transformer according to an embodiment of the present application.

[0023] Figure 2 It is a flow chart of a method for controlling the thyristor triggering angle of a transformer according to an embodiment of the present application.

[0024] Figure 3 It is a waveform diagram of the load voltage and the trigger angle when the target load voltage V0 is less than or equal to the first threshold voltage V1 according to an embodiment of the present application.

[0025] Figure 4 It is a waveform diagram of the load voltage and the trigger angle when the target load voltage V0 is greater than the first threshold voltage V1 and less than or equal to the second threshold voltage V2 according to an embodiment of the present application. DETAILED DESCRIPTION

[0026] In the following description, many technical details are provided to help readers better understand the present application. However, those skilled in the art can understand that the technical solution claimed in the present application can be implemented even without these technical details and various changes and modifications based on the following embodiments.

[0027] Description of some concepts:

[0028] A single-phase double-tapped transformer is a special transformer that has a single-phase power input and has two taps (or more) on its secondary coil, allowing it to output at different voltages. In simple terms, taps are additional connection points on the transformer coil that can change the number of coil turns and thus adjust the output voltage.

[0029] The trigger angle (also called the conduction angle, "Firing Angle" in English) describes the time point when the thyristor or SCR is triggered (turned on) in the AC power cycle, which is used to control the conduction duration and output voltage / current.

[0030] In order to make the objectives, technical solutions and advantages of the present application clearer, the implementation methods of the present application will be further described in detail below in conjunction with the accompanying drawings.

[0031] One embodiment of the present application relates to a method for controlling a thyristor trigger angle of a transformer. Figure 1 FIG. 1 shows a schematic diagram of a circuit structure of a transformer in an embodiment. Figure 2 FIG. 1 is a flow chart showing a method for controlling the thyristor triggering angle of a transformer in an embodiment. Figure 1 As shown, the transformer T1 includes a primary coil and a secondary coil. The input voltage Vin is received between the terminal 1 and the terminal 2 of the primary coil, and the secondary coil has a terminal 3, a terminal 4, and a terminal 5. The terminal 4 and the terminal 5 are respectively the first tap and the second tap. The secondary coil is respectively connected with the first thyristor S1, the second thyristor S2, the third thyristor S3, and the fourth thyristor S4, and the load on the secondary coil is equivalent to Figure 1 The first thyristor S1 and the second thyristor S2 are connected in parallel between the first tap and the resistive load R. The third thyristor S3 and the fourth thyristor S4 are connected in parallel between the second tap and the resistive load R.

[0032] In one embodiment, the connection directions of the first thyristor S1 and the second thyristor S2 are opposite, wherein the cathode of the first thyristor S1 is connected to one end of the resistive load R, the anode of the first thyristor S1 is connected to the first tap, the anode of the second thyristor S2 is connected to one end of the resistive load R, and the cathode of the second thyristor S2 is connected to the first tap. The other end of the resistive load R is connected to the terminal 3 of the secondary coil. The output voltage at the first tap is V1.

[0033] In one embodiment, the third thyristor S3 and the fourth thyristor S4 are connected in opposite directions, the cathode of the third thyristor is connected to one end of the resistive load, the anode is connected to the second tap, the anode of the fourth thyristor is connected to one end of the resistive load, and the cathode is connected to the second tap. The output voltage at the second tap is V2.

[0034] In one embodiment, the output voltage V1 at the first tap is less than the voltage V2 at the second tap.

[0035] refer to Figure 1 and Figure 2 As shown, the method 100 for controlling the thyristor triggering angle of the transformer includes the following steps:

[0036] Step 101 , obtaining an error current ΔI between a target load current I0 and a current load current I, and calculating an error voltage ΔV of a resistive load R according to the error current ΔI.

[0037] In one embodiment, a proportional integral (PI) regulation method is used to calculate the error voltage ΔV of the resistive load according to the error current ΔI. , where Kp is the proportional gain, Ki is the integral gain, and ΔI is the error current.

[0038] Step 102: When the target load voltage V0 is less than or equal to the first threshold voltage V1, the formula The error trigger angle is calculated, where Δθ is the error trigger angle, V1 is the first threshold voltage, α1 is the trigger angle of the first thyristor S1 and the second thyristor S2, ΔV is the error voltage, and the trigger angles of the first thyristor S1 and the second thyristor S2 are adjusted according to the error trigger angle Δθ. The first threshold voltage V1 is the output voltage V1 at the first tap.

[0039] In one embodiment, when the target load voltage V0 is less than or equal to the first threshold voltage V1, the first thyristor S1 and the second thyristor S2 are turned on, and the third thyristor S3 and the fourth thyristor S4 are turned off.

[0040] In one embodiment, adjusting the trigger angles of the first thyristor S1 and the second thyristor S2 according to the error trigger angle Δθ further includes: adjusting the trigger angles of the first thyristor S1 and the second thyristor S2 to α1-Δθ.

[0041] Step 103: When the target load voltage V0 is greater than the first threshold voltage V1 and less than or equal to the second threshold voltage V2, the formula The error trigger angle is calculated, where Δθ is the error trigger angle, V1 is the first threshold voltage, V2 is the second threshold voltage, α2 is the trigger angle of the third thyristor S3 and the fourth thyristor S4, and the trigger angles of the third thyristor S3 and the fourth thyristor S4 are adjusted according to the error trigger angle Δθ. The first threshold voltage V1 is the output voltage V1 of the first tap, and the second threshold voltage V2 is the output voltage V2 at the second tap.

[0042] In one embodiment, when the target load voltage V0 is greater than the first threshold voltage V1 and less than or equal to the second threshold voltage V2, the first thyristor S1 and the second thyristor S2 are fully turned on, that is, the trigger angle of the first thyristor S1 and the second thyristor S2 is 0°, and the third thyristor S3 and the fourth thyristor S4 are turned on.

[0043] In one embodiment, adjusting the trigger angles of the third thyristor S3 and the fourth thyristor S4 according to the error trigger angle Δθ further includes: adjusting the trigger angles of the third thyristor S3 and the fourth thyristor S4 to α2-Δθ.

[0044] In this embodiment, the algorithm for adjusting the SCR trigger angle by load current control of the single-phase double-tap transformer provides a stable load current, greatly reduces the calculation amount of the controller, reduces the harmonics of the power grid, and improves the power factor.

[0045] In order to better understand the technical solution of the present application, a specific example is provided below for illustration. The details listed in the example are mainly for ease of understanding and are not intended to limit the scope of protection of the present application.

[0046] When the trigger angle of the thyristor is controlled with the load current as the target, the trigger angle of the thyristor is directly adjusted by the difference between the target load current and the current load current. Due to the non-proportional relationship between the load current value and the trigger angle, the adjustment speed and stability vary greatly when the current trigger angle value is different.

[0047] For resistive loads, the target load voltage is calculated by the load error current, and the current control angle can be directly calculated by the load voltage. However, the calculation formula is complicated, which greatly increases the burden on the controller.

[0048] The present invention proposes a calculation method for calculating a target load voltage corresponding to a target load current and an error voltage ΔV of a current load voltage through an error current ΔI between a target load current and a current load current, and then calculating an error trigger angle Δθ that needs to be adjusted through the error voltage ΔV and according to a current thyristor trigger angle α.

[0049] The error current ΔI calculates the error voltage ΔV using PI regulation, and the formula is as follows:

[0050]

[0051] Among them, Kp is the proportional gain factor, Ki is the integral gain factor, and different PI adjustment parameters can be selected according to the characteristics of the load.

[0052] The calculation method of error voltage ΔV and error trigger angle Δθ is as follows:

[0053] (1) When 0≤V0≤V1, the third thyristor S3 and the fourth thyristor S4 do not work. At this moment, the trigger angle of the first thyristor S1 and the second thyristor S2 is α (0≤α≤π), and the load voltage is V0.

[0054] The load voltage formula is:

[0055]

[0056] When the error trigger angle Δθ is adjusted, the target load voltage V 01 The formula is:

[0057]

[0058] Where Δθ is the error trigger angle between the first thyristor S1 and the second thyristor S2, and V0 is the load voltage.

[0059] The waveform of the load voltage is as follows: Figure 3 As shown in the figure, because the Δθ adjusted each time is very small, the integral within Δθ can be equivalent to Figure 3 The value of the shadow area of ​​the medium rectangle. Figure 3 The horizontal axis is the trigger angle θ, and the vertical axis is the load voltage V0.

[0060] Then the error voltage ΔV is:

[0061]

[0062] The error trigger angle Δθ is:

[0063]

[0064] Then when 0≤V0≤V1, the trigger angle of the first thyristor S1 and the second thyristor S2 at the next moment is α -Δθ, the third thyristor S3 and the fourth thyristor S4 do not work.

[0065] (2) When V1< V0< V2, the trigger angle of the first thyristor S1 and the second thyristor S2 is 0 degrees, and the trigger angle of the third thyristor S3 and the fourth thyristor S4 is α（0≤α≤π） , the load voltage is V0.

[0066] The load voltage V0 formula is:

[0067]

[0068] When the error trigger angle Δθ is adjusted, the target load voltage V 01 The formula is:

[0069]

[0070] Formula (7) can be further decomposed into:

[0071]

[0072] Where Δθ is the error trigger angle of the third thyristor S3 and the fourth thyristor S4, and V0 is the load voltage.

[0073] The waveform of the load voltage is as Figure 4 shown. Since the Δθ adjusted each time is very small, the integral value within Δθ is equivalent to the Figure 4 value of the rectangular shaded area in Figure 3 where the abscissa is the trigger angle θ and the ordinate is the load voltage V0.

[0074] Then the error voltage ΔV is:

[0075]

[0076] The error trigger angle Δθ is:

[0077]

[0078] Then when V1 < V0 < V2, the trigger angles at which the third thyristor S3 and the fourth thyristor S4 work at the next moment are α -Δθ, and the trigger angles at which the first thyristor S1 and the second thyristor S2 work are 0 degrees.

[0079] Through the above algorithm, the stable and reliable control of the load current of the single-phase double-tapped transformer can be realized, and at the same time, the calculation amount is greatly reduced.

[0080] When the load current value is small, the thyristors at the low-voltage tap of the secondary side of the transformer are controlled to work; when the load current value is large, the thyristors at the low-voltage tap and the high-voltage tap of the secondary side of the transformer work simultaneously, the load current works stably, the calculation amount of the controller is greatly reduced, the harmonics of the power grid are reduced, and the power factor is improved.

[0081] An embodiment of the present application also relates to a device for controlling the trigger angle of the thyristor of a transformer. The transformer includes a first thyristor and a second thyristor connected in parallel between the first tap and the load, and a third thyristor and a fourth thyristor connected in parallel between the second tap and the load. The device includes an acquisition unit and an adjustment unit. The acquisition unit acquires the error current between the target load current and the current load current, and calculates the error voltage of the resistive load according to the error current. When the target load voltage is less than or equal to the first threshold voltage, the adjustment unit uses the formula to calculate the error trigger angle and adjust the trigger angles of the first thyristor and the second thyristor. When the target load voltage is greater than the first threshold voltage and less than or equal to the second threshold voltage, the adjustment unit uses the formula Calculate the error trigger angle and adjust the trigger angles of the third thyristor and the fourth thyristor; Δθ is the error trigger angle, ΔV is the error voltage, V1 and V2 are the first threshold voltage and the second threshold voltage, α1 is the trigger angle of the first thyristor and the second thyristor, and α2 is the trigger angle of the third thyristor and the fourth thyristor.

[0082] The above-mentioned implementation manner is a method implementation manner corresponding to the present implementation manner. The technical details in the above-mentioned implementation manner can be applied to the present implementation manner, and the technical details in the present implementation manner can also be applied to the above-mentioned implementation manner.

[0083] It should be noted that, in the present application, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Moreover, the term "include", "comprise" or any other variant thereof is intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or equipment. In the absence of more restrictions, the elements defined by the sentence "include one" do not exclude the existence of other identical elements in the process, method, article or equipment including the elements. In the present application, if it is mentioned that a certain action is performed according to a certain element, it means at least the meaning of performing the action according to the element, which includes two situations: performing the action only according to the element and performing the action according to the element and other elements. Multiple, multiple, multiple, etc. expressions include 2, 2 times, 2 kinds and more than 2, more than 2 times, more than 2 kinds.

[0084] The serial numbers used in describing the steps of the method do not themselves constitute any limitation on the order of these steps. For example, the step with a larger serial number does not necessarily have to be executed after the step with a smaller serial number. The step with a larger serial number may be executed first and then the step with a smaller serial number. They may also be executed in parallel, as long as the execution order is reasonable to those skilled in the art. For another example, multiple steps with consecutive serial numbers (e.g., step 101, step 102, step 103, etc.) do not limit other steps that can be executed in between. For example, there may be other steps between step 101 and step 102.

[0085] This specification includes combinations of the various embodiments described herein. Individual references to embodiments (e.g., "one embodiment" or "some embodiments" or "preferred embodiments"); however, these embodiments are not mutually exclusive unless indicated as mutually exclusive or clear to those skilled in the art. It should be noted that the word "or" is used in this specification in a non-exclusive sense unless the context clearly indicates or requires otherwise.

[0086] All documents mentioned in this specification are considered to be included in the disclosure of this application as a whole, so that they can be used as a basis for modification when necessary. In addition, it should be understood that the above is only a preferred embodiment of this specification and is not intended to limit the scope of protection of this specification. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of one or more embodiments of this specification should be included in the scope of protection of one or more embodiments of this specification.

[0087] In some cases, the actions or steps described in the claims may be performed in a different order than in the embodiments and still achieve the desired results. In addition, the processes depicted in the drawings do not necessarily require the specific order or sequential order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

Claims

1. A method for controlling the thyristor trigger angle of a transformer, characterized in that: The transformer comprises a first thyristor and a second thyristor connected in parallel between a first tap and a resistive load, and a third thyristor and a fourth thyristor connected in parallel between the second tap and the resistive load, and the method comprises: Obtain the error current between the target load current and the current load current, and use the proportional integral regulation method to calculate the error voltage of the resistive load according to the error current. , where Kp is the proportional gain, Ki is the integral gain, and ΔI is the error current; When the target load voltage is less than or equal to the first threshold voltage, the formula is used Calculating an error trigger angle, where Δθ is the error trigger angle, V1 is the first threshold voltage, α1 is the trigger angle of the first thyristor and the second thyristor, ΔV is the error voltage, and adjusting the trigger angle of the first thyristor and the second thyristor to α1-Δθ according to the error trigger angle; When the target load voltage is greater than the first threshold voltage and less than or equal to the second threshold voltage, the formula is used. The error trigger angle is calculated, where V2 is the second threshold voltage, α2 is the trigger angle of the third thyristor and the fourth thyristor, and the trigger angle of the third thyristor and the fourth thyristor is adjusted to α2-Δθ according to the error trigger angle.

2. The method according to claim 1, characterized in that When the target load voltage is less than or equal to a first threshold voltage, the first thyristor and the second thyristor are turned on, and the third thyristor and the fourth thyristor are turned off.

3. The method according to claim 1, characterized in that When the target load voltage is greater than the first threshold voltage and less than or equal to the second threshold voltage, the first thyristor and the second thyristor are fully turned on, and the third thyristor and the fourth thyristor are turned on.

4. The method according to claim 1, characterized in that The trigger angles of the first thyristor and the second thyristor are 0°.

5. The method according to claim 1, characterized in that The cathode of the first thyristor is connected to one end of the resistive load, and the anode is connected to the first tap; the anode of the second thyristor is connected to one end of the resistive load, and the cathode is connected to the first tap.

6. The method according to claim 1, characterized in that The cathode of the third thyristor is connected to one end of the resistive load, and the anode is connected to the second tap; the anode of the fourth thyristor is connected to one end of the resistive load, and the cathode is connected to the second tap.

7. The method according to claim 1, characterized in that The output voltage at the first tap is less than the voltage at the second tap, wherein the first threshold voltage is the output voltage at the first tap, and the second threshold voltage is the output voltage at the second tap.

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