On-load voltage regulation method and system for thyristor without circulating current and reverse voltage surge

Abstract

The invention provides an on-load voltage regulation method for thyristors without circulating current and reverse voltage surge, and the method comprises the steps: enabling a processor to indicate a control circuit to give out a first switching-on instruction, so as to switch on a first path of thyristor; after receiving the '0' signal, the processor quickly indicates the control circuit to send out a first blocking instruction to block other paths of thyristors; when gear shifting is judged to be needed, the processor sends a first turn-off instruction to the first thyristor, so that the first thyristor enters a waiting state, and the control circuit is instructed to send a second turn-on instruction to turn on the second thyristor; after preset delay time, backward voltage is applied to the first path of thyristor, and after the processor receives a '1' signal sent by the control circuit, the processor indicates the control circuit to send out a first unlocking control signal; before the control circuit does not send out the first unlocking control signal, the first locking instruction is continuously sent out. According to the method, circulating current short circuit and reverse current and voltage impact can be avoided, and reliable and stable operation of the thyristor is guaranteed.

Description

Technical Field

[0001] This application relates to the field of on-load voltage regulation, and more specifically, to an on-load voltage regulation method and system that eliminates circulating current and reverse voltage surges in thyristors. Background Technology

[0002] The development of arc-free on-load tap changer technology can be summarized as an evolution from mechanical to power electronic methods. Its core objective is to solve the arcing problem in traditional tap changers and improve reliability and response speed. Currently, the development of arc-free on-load tap changer technology has encountered a bottleneck in balancing cost, reliability, and environmental adaptability. It has not gained widespread acceptance from society and the market, resulting in slow development and limited widespread adoption.

[0003] Thyristor on-load tap changer technology is mainly used in power systems, industrial electric furnaces, lighting control, chemical equipment, automobile manufacturing, energy-saving lighting, glass production, electric locomotives, non-ferrous metal smelting, and generator power supplies. It achieves on-load voltage regulation through power electronic components, featuring no electric sparks when switching voltage taps, long service life, and rapid and frequent switching capabilities. It precisely controls voltage, current, and power, improving equipment efficiency and stability. Thyristors have advantages such as low on-state voltage drop, low turn-off loss, high load capacity, and relatively mature domestic device development. Circuit control is achieved through high-power thyristors. High-power thyristors, with their high voltage and current withstand capabilities, fast and efficient operation, high reliability, long service life, and low cost, are now widely used in second- and third-generation high-speed rail, light rail, and subway electric locomotives in my country. A thyristor voltage regulator (TVR) is a type of voltage regulator suitable for medium-voltage power distribution lines. It uses a thyristor-based contactless static on-load tap changer instead of a mechanical on-load tap changer, offering not only faster voltage regulation but also the ability to operate quickly and frequently. However, due to the special operating environment of the regulating transformer and the random fluctuations in the phase of the load voltage and current, existing contactless voltage regulation technologies have shortcomings in their trigger control logic modules and unreasonable current detection and tracking module techniques. This leads to frequent damage and burnout of the thyristor modules in the electrical equipment; moreover, it easily damages the regulating module itself and its windings, or significantly increases the rated current and voltage parameters of the devices, increasing costs.

[0004] To address the problem of thyristor damage caused by circulating current short circuits or reverse current voltage surges in traditional TVRs, it is necessary to improve the current voltage regulation equipment. Summary of the Invention

[0005] In view of this, the embodiments of this application aim to provide an on-load voltage regulation method and system with no circulating current and no reverse voltage surge of the thyristor, so as to solve the problem of easy damage of thyristors in on-load voltage regulation.

[0006] Firstly, this specification provides an on-load voltage regulation method for thyristors without circulating current or reverse voltage surge, the method comprising: The processor instructs the control circuit to issue a first turn-on command to turn on the first thyristor; After receiving the "0" signal from the control circuit, the processor quickly instructs the control circuit to issue the first blocking command to other thyristors to block them. If a gear shift is required, the processor sends a first shutdown command to the first thyristor to put it into a standby state, and instructs the control circuit to send a second turn-on command to turn on the second thyristor. After a predetermined delay time, the processor instructs the control circuit to apply a reverse voltage to the first thyristor, and after the processor receives a "1" signal from the control circuit, it instructs the control circuit to issue a first unlocking control signal. Before the control circuit issues the first unlocking control signal, the control circuit continuously issues the first blocking command; The “0” signal indicates that the voltage across the first thyristor is low and current is flowing through it, while the “1” signal indicates that the voltage across the first thyristor is high and no current is flowing through it. The predetermined delay time is determined based on the performance of the first thyristor and the reverse voltage. The first unblocking control signal indicates that the first thyristor is turned off and allows other thyristors to be turned on.

[0007] According to the first aspect, in one possible implementation, the predetermined delay time is completed on the axis where the current crosses zero, and is determined by the waveform correction circuit and the RC delay timing circuit.

[0008] According to the first aspect, in one possible implementation, the predetermined delay time ranges from tens of microseconds to hundreds of microseconds, and the time from the turn-on of the first thyristor to the issuance of the first blocking command is hundreds of nanoseconds.

[0009] According to the first aspect, in one possible implementation, after the first thyristor is turned on, the method further includes: the first thyristor transmitting current to the power transformer in a full cycle of positive and negative alternation in the order of a sine wave without additional waveform distortion, until a first turn-off command is received.

[0010] According to the first aspect, in one possible implementation, the method further includes: after power-on, setting all thyristors to an instantaneous off state.

[0011] According to the first aspect, in one possible implementation, each thyristor is a bidirectional thyristor or a bidirectional thyristor composed of two unidirectional thyristors connected in reverse.

[0012] According to the first aspect, in one possible implementation, determining that a gear shift is required includes the processor determining the gear shift based on a sampled voltage value.

[0013] Secondly, this specification provides an on-load tap changer system with no circulating current and no reverse voltage surge of the thyristor, the system comprising: The control circuit includes multiple control branches that correspond one-to-one with the multi-channel thyristors; The processor is connected to multiple control branches; Among them, the multi-channel thyristor connects the input AC power supply to the input terminals of different voltage taps of the power transformer, and the control terminal of each thyristor is connected to the output terminal of one of the multiple control branches.

[0014] According to the second aspect, in one possible implementation, each of the plurality of control branches includes a blocking gate trigger working path selection, a trigger control module, a transmission isolation module (outward), a current zero-crossing detection module, a transmission isolation module (inward), a judgment and waiting module, a fast blocking module, and a blocking path selection.

[0015] According to the second aspect, in one possible implementation, the current zero-crossing detection module includes a waveform correction circuit and an RC delay timing circuit.

[0016] Compared with the prior art, the beneficial effects of this application are as follows: Unlike existing technologies, this application uses control circuits at both ends of the thyristor to detect voltage and current, identifying the state of each thyristor. This ensures that at any given time, only one thyristor is turned on. Furthermore, when a turn-off command is received requiring switching, a predetermined delay is waited before applying a reverse voltage, thus avoiding loop current and reverse current / voltage surges and ensuring reliable and stable thyristor operation. This method and system, which uses a natural current zero-crossing and waits for the thyristor's charge carriers to dissipate naturally before triggering the next thyristor, enables the thyristor to switch near the current zero-crossing point in resistive, inductive, and complex loads. This method has extremely strong anti-interference capabilities, eliminating current surges during commutation, overvoltage generation, time interruptions during current / voltage commutation, and interference radiation sources. It does not change the circuit's power factor and avoids damage to the thyristor due to overcurrent and overvoltage. This method of voltage regulation is very stable and reliable, without interference and with accurate judgment, which extends the service life of the equipment and enables the thyristor and other related equipment to work and operate safely, stably and with high reliability. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0018] Figure 1 This is a schematic flowchart illustrating an on-load voltage regulation method for thyristors without circulating current or reverse voltage surge, provided in an embodiment of this application.

[0019] Figure 2 This is a schematic diagram of an on-load voltage regulating system with no circulating current and no reverse voltage surge of the thyristor, provided as an embodiment of this application.

[0020] Figure 3 Provided for the embodiments of this application Figure 2 A schematic diagram of the internal structure of the medium current zero-crossing detection module.

[0021] Figure 4 Provided for the embodiments of this application Figure 2 Circuit diagram of the thyristor trigger drive module.

[0022] Attached label: 1-Route selection command blocking gate and trigger thyristor working route selection (hereinafter referred to as blocking gate trigger working route selection); 2-Thyristor trigger control module (hereinafter referred to as trigger control module); 3-High and low voltage data transmission isolation module (outward) (hereinafter referred to as transmission isolation module (outward)); 4-Thyristor trigger drive module (hereinafter referred to as trigger drive module); 5-Current zero-crossing detection module; 6-High and low voltage data transmission isolation module (inward) (hereinafter referred to as transmission isolation module (inward)); 7-"0", "1" judgment and time waiting module (hereinafter referred to as judgment and waiting module); 8-"0", "1" signal fast blocking module (hereinafter referred to as fast blocking module); 9-Blocking signal number selection (hereinafter referred to as blocking route selection). Detailed Implementation

[0023] Unless otherwise defined, the technical or scientific terms used in the embodiments of this specification shall have the ordinary meaning understood by one of ordinary skill in the art to which this specification pertains. The terms "first," "second," and similar terms used in the embodiments of this specification do not indicate any order, quantity, or importance, but are merely used to avoid confusion of constituent elements.

[0024] Unless the context otherwise requires, throughout this specification, "a plurality of" means "at least two," and "including" is interpreted as open-ended or encompassing, that is, "including, but not limited to." In the description of this specification, terms such as "one embodiment," "some embodiments," "exemplary embodiment," "example," "specific example," or "some examples" are intended to indicate that a particular feature, structure, material, or characteristic associated with that embodiment or example is included in at least one embodiment or example of this specification. The illustrative representations of the above terms do not necessarily refer to the same embodiment or example.

[0025] The technical solutions in the embodiments of this specification will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this specification, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments in this specification without creative effort are within the scope of protection of this specification.

[0026] Previously, there was no accurate, stable, and reliable detection method for the zero-crossing point of thyristor current, and immature control methods often caused circulating current short circuits and reverse current and voltage surges, resulting in frequent damage to thyristors and even transformers.

[0027] To ensure the normal operation of thyristor-triggered control under inductive loads, a common method is to turn the thyristor on and off when the current crosses zero. This requires synchronous tracking of the load current's zero-crossing point. However, during the initial startup phase, the current is small or has not yet reached zero-crossing stability, or there may be severe power supply interference. Furthermore, load changes can cause random shifts in the load current's zero-crossing point. Although many methods for detecting zero-crossing points have been employed, some are inconvenient to install, others have complex circuits, and almost all suffer from poor synchronization reliability, unstable synchronization, synchronization point jitter, or pulse interference. These problems can sometimes lead to synchronization loss and disorder. In thyristor current zero-crossing trigger control, any loss of synchronization, unstable synchronization point, or synchronization interference will cause varying degrees of overcurrent surges or overvoltage back peaks threatening the thyristor, and may even burn out the equipment.

[0028] In the thyristor-based on-load tap changer of this application, voltage and current sensors are connected to the anode and cathode of the thyristor. When the thyristor is on, the voltage across the anode and cathode is low and current flows, resulting in a "0" signal. When the thyristor is off, the voltage across the anode and cathode increases and no current flows, resulting in a "1" signal. Using "0" and "1" signals to determine the on / off state of the thyristor will never result in a misjudgment. Using "0" and "1" signals in conjunction with the control circuit to control blocking, deblocking, the start and end of time delays, and the passage and blocking of controller commands is the most accurate, stable, and reliable control method. During operational testing, no inaccurate judgments or control errors have occurred.

[0029] This method ensures that during gear shifting, the current of the shut-off thyristor has not yet reached zero, and the other thyristor to be turned on prematurely, causing a short-circuit current overcurrent that could damage the circuit.

[0030] After the thyristor is turned off and the sinusoidal current ends, the thyristor has a low-doped, highly injected base region. Due to the characteristics of thyristor devices, the interior is filled with a large number of charge carriers during conduction. A method is used to wait for a period of time after the thyristor current crosses zero, allowing its electron charge to be completely released before applying a reverse voltage for switching. This solves the problem of residual current in the previously turned-on thyristor generating reverse voltage that threatens thyristor safety or even causes breakdown.

[0031] The zero-crossing detection current in this application involves soft-turning off the current at zero crossover. The current pauses for a period of time (e.g., several hundred microseconds) after crossing zero before a reverse voltage is applied. This pause allows the charge carriers in the turned-off thyristor to dissipate naturally, thus avoiding the impact of a high-voltage reverse current when a reverse voltage is applied. The voltage rise or fall during turn-off follows the phase difference applied to the thyristor by the transformer at the time point, representing the total voltage amplitude at that point (the total voltage is the sinusoidal phase angle at which the reverse voltage rises after the thyristor is turned off; the zero-crossing point of the pure resistive load current is also the zero-crossing point of the phase voltage). Then, the next thyristor is turned on after the voltage of the turned-off thyristor rises. This method utilizes the zero-crossing point of a sine wave, followed by a certain waiting time to allow the accumulated charge carriers in the thyristor to completely dissipate before applying a reverse voltage and opening the thyristor to be switched transformer taps. This completely eliminates the problem of a large amount of charge carriers stored inside the thyristor not being fully released when a reverse voltage is applied before it is turned off, which would generate a huge current and induce a very high overvoltage in the circuit inductor, thus breaking down the thyristor. This method prevents the thyristor from being damaged.

[0032] Through the above two key methods, the controller opens and closes the corresponding thyristors based on the output voltage level. Equipped with various transmission, isolation, analysis, enable, block, unlock drive, judgment and analysis functions, the controller controls the thyristors to switch the transformer taps in an environment without loop short-circuit inrush current or reverse inrush voltage, thereby switching the voltage between high and low levels. This achieves high-performance output with continuous and uninterrupted control voltage waveform without additional harmonic effects, ensuring that the thyristors are not damaged and can operate stably and reliably.

[0033] To achieve these effects and gains, a thyristor is connected in series at the transformer's voltage adjustment tap. High-reliability voltage and current sensors are connected across the thyristor to precisely monitor the voltage and current at the cathode and anode when the thyristor is turned off, outputting "0" and "1" signals. These "1" and "0" signals represent the thyristor's on and off states, controlling the opening of thyristors that need to be turned on. Opened thyristors emit a "0" signal to block thyristors that do not need to be turned on. Blocked thyristors remain reliably off unless a commutation adjustment command is received from the processor. The voltage and current sensors monitor the open thyristors, ensuring that they output a stable voltage and waveform according to a sine wave pattern. Unless the processor determines that a transformer tap needs to be switched based on voltage changes, the sine wave continuously alternates between positive and negative waveforms. Only after receiving a turn-off command from the processor, the current flowing through the thyristor decays to zero. Then, a reverse voltage is applied and the circuit is turned off. After the circuit is turned off, the cathode and anode terminals output a high voltage signal of "1", which sends an unblocking signal to unlock each channel, causing the thyristor that needs to be turned on to open. After the newly turned-on thyristor outputs a signal of "0", it blocks all other thyristors, including the previously turned-on thyristor, from being turned on, thus completing one voltage switching process.

[0034] The above conversion process ensures that the thyristor turned on after the conversion is confirmed to have been turned off. It avoids the problem of the current of the turned-off thyristor not being completely terminated, resulting in current overlap with the thyristor turned on later, which could cause short circuit overcurrent and burn out the thyristor.

[0035] The above forms the theoretical basis for implementing the proposed solution.

[0036] like Figure 1 The diagram shown is a schematic flowchart of an on-load voltage regulation method for thyristors without circulating current and reverse voltage surge provided in an embodiment of this application. The method may specifically include the following steps.

[0037] S110: The processor instructs the control circuit to issue the first turn-on command to turn on the first thyristor.

[0038] S120: After receiving the "0" signal from the control circuit, the processor quickly instructs the control circuit to issue the first blocking command to other thyristors to block them.

[0039] S130: If a gear shift is required, the processor sends a first shutdown instruction to the first thyristor to put it into a standby state, and instructs the control circuit to send a second turn-on instruction to turn on the second thyristor.

[0040] S140: After a predetermined delay time, the processor instructs the control circuit to apply a reverse voltage to the first thyristor, and after the processor receives a "1" signal from the control circuit, it instructs the control circuit to issue a first unlocking control signal.

[0041] S150: Before the control circuit issues the first unlocking control signal, the control circuit continuously issues the first blocking command.

[0042] In the above method, the multiple thyristors connect the input AC power supply to the input terminals of different voltage taps on the power transformer. The processor can be an embedded processor, desktop processor, or mobile processor, etc., and is connected to the multiple thyristors through a control circuit. The first turn-on command instructs the first thyristor in the multiple thyristors to be turned on. The first thyristor can be a pre-programmed number; for example, if there are 5 thyristors in the multiple thyristors, numbered 1 to 5, the first thyristor can be any one of 1 to 5. After the first thyristor is turned on, a first blocking command is immediately issued through a detected "0" signal, thereby ensuring that at most one thyristor is turned on at any given time. The "0" signal indicates that the voltage across the first thyristor is low and current is flowing through it, while the "1" signal indicates that the voltage across the first thyristor is high and no current is flowing through it. The predetermined delay time is determined based on the performance of the first thyristor and the reverse voltage. The first unblocking control signal instructs the first thyristor to be turned off and allows the other thyristors to be turned on. "Low voltage" is a relative concept, and a voltage value can be preset according to actual needs. For example, in low-voltage equipment scenarios, low-voltage thresholds can be set to 12V, 5V, 2.4V, etc. Voltages above this threshold are considered high voltage, and those below are considered low voltage. Of course, a high-voltage threshold can also be set to determine low voltage using the low-voltage threshold and high voltage using the high-voltage threshold. Similarly, in high-voltage equipment scenarios, low-voltage thresholds can be set to 220V, 380V, or even thousands of volts. During gear switching, the first thyristor first enters a waiting state for a predetermined delay time. Then, a reverse voltage is applied to the first thyristor, making the voltage across it high and preventing current flow. Upon receiving a "1" signal, the processor instructs the control circuit to issue the first deblocking control signal, thereby turning on the second thyristor. The time from receiving the first turn-off command from the first thyristor to turning on the second thyristor is only a few hundred microseconds. Due to the relatively short time, which is close to a continuous current transition, the voltage does not drop significantly and therefore does not affect normal operation.

[0043] This embodiment detects "0" and "1" signals of voltage and current to ensure that only one thyristor is turned on at any given time. Furthermore, during gear shifting, a predetermined delay is waited before applying reverse voltage. This avoids circulating current short circuits, reverse instantaneous current surges, and reverse voltage spikes, ensuring the safe and reliable operation of the thyristor, preventing damage to other components, extending equipment lifespan, and enabling safe, stable, and highly reliable operation of the thyristor and other related equipment.

[0044] The control circuit, composed of a high-reliability voltage and current detection module and a high-reliability trigger control module, performs voltage and current detection on the thyristor and accurate current zero-crossing trigger control. This completely solves the problem of the lack of reliable and mature current zero-crossing detection technology for complex loads, enabling the thyristor to work safely and reliably in a circuit environment without overcurrent impact or reverse peak breakdown voltage, thus fundamentally solving the key problem of TVR.

[0045] During the natural zero-crossing turn-off of a thyristor, even if the current decays sinusoidally to zero, the stored charge carriers are still rapidly drawn away due to the immediate reversal of the power supply voltage after the current crosses zero, forming a reverse recovery current. This reverse recovery current generates a large instantaneous current and overvoltage when the charge carriers are depleted. If a reverse voltage is applied with a delay after the current naturally crosses zero (e.g., a delay of several hundred μs on the axis at the current zero-crossing point), the charge carriers have more time to dissipate, reducing the reverse recovery charge and thus significantly lowering the peak value and instantaneous current of the reverse recovery current, weakening or eliminating the overvoltage. In actual AC circuits, the power supply voltage changes continuously, requiring additional control to achieve this delay, and the delay time must be greater than the charge carrier lifetime (typically tens to hundreds of microseconds) to be effective. Therefore, in principle, delaying the application of the reverse voltage can suppress spikes and overvoltages, but the performance parameters need to be adjusted according to the actual circuit.

[0046] For example, for thyristors used in medium to high current applications, their carrier lifetime (usually referring to minority carrier lifetime) typically ranges from tens to hundreds of microseconds, with a typical value of approximately 50 to 150 microseconds. Specific values ​​vary depending on device design, materials, and manufacturing processes. For instance, some 300A / 1200V thyristors may have a turn-off time between 30 and 60 microseconds, while their carrier lifetime may be slightly longer. During turn-off, if a reverse voltage is applied after the current naturally crosses zero (e.g., with a delay of 500 μs), this delay is usually much longer than the carrier lifetime, sufficient to allow the stored charge to dissipate fully through recombination. This significantly reduces the peak value and rate of change of the reverse recovery current, suppressing overvoltage. In practical applications, the specific carrier lifetime or turn-off time must be determined according to the device datasheet to design appropriate buffer circuits or control strategies.

[0047] In at least one embodiment of this application, in order to properly design and adjust the predetermined delay time so that the thyristor in the circuit can operate safely and reliably under conditions of no circulating current and no reverse voltage, the predetermined delay time is completed on the axis of zero current crossing and is determined by the waveform correction circuit and the RC delay timing circuit.

[0048] If the delay time is too short, some reverse voltage will be generated. However, if the delay time is too long, it will delay the conduction angle of the next half-wave, resulting in an incomplete voltage waveform and a voltage drop. Furthermore, in non-purely resistive loads, the axis of current zero-crossing is not the same as the axis of voltage zero-crossing. This embodiment avoids overvoltage by completing the predetermined delay time on the axis of current zero-crossing (i.e., timing begins after the current crosses zero) and by using a waveform correction circuit and an RC delay timing circuit. After the predetermined delay time, once all charge has dissipated, the system waits for the arrival of the reverse turn-off voltage.

[0049] In at least one embodiment of this application, in order to determine the predetermined delay time and quickly turn off other thyristors after the first thyristor is turned on, the predetermined delay time is set to a range of tens of microseconds to hundreds of microseconds, and the time from the turn-on of the first thyristor to the issuance of the first blocking command is set to hundreds of nanoseconds. These time settings further ensure rapid switching and continuous output.

[0050] In at least one embodiment of this application, to further improve the quality of the output power supply, after the first thyristor is turned on, the method further includes: the first thyristor transmitting current to the power transformer in a full cycle without additional waveform distortion, alternating between positive and negative sine waves in the order of a sine wave, until a first turn-off command is received. If it is not necessary to switch the transformer tap positions, the thyristor that is turned on will turn on for half a cycle according to the phase sequence of the self-triggered sine wave, and then continuously turn on for the other half cycle, so that the full cycle runs continuously without interruption; until the processor determines whether the output voltage needs to be increased or decreased based on the level of the sampled voltage, and then issues a conversion command. The sampled voltage can be obtained by the processor through an additional component (e.g., a voltage transformer). By transmitting current in a full cycle without additional waveform distortion, alternating between positive and negative sine waves in the order of a sine wave, no harmonic interference or gaps are generated, and continuous operation is possible.

[0051] In at least one embodiment of this application, in order to control the power-on logic and ensure smooth operation of gear switching, the method further includes: after power-on, setting all thyristors to a momentary off state. In the momentary off state, all thyristors wait to receive instructions, and the processor issues an on instruction based on voltage data to turn on a certain thyristor, while the other thyristors are placed in the off state after one thyristor is turned on.

[0052] In at least one embodiment of this application, to facilitate circuit implementation and reduce costs, each thyristor is a bidirectional thyristor or a bidirectional thyristor composed of two unidirectional thyristors connected in reverse. Bidirectional thyristors have bidirectional conduction capability, are easy to trigger, can withstand voltages of several kilovolts and currents of tens to hundreds of amperes, have no mechanical contacts, long lifespan, and low cost. At the same time, this solution overcomes some disadvantages of traditional bidirectional thyristors, such as difficulty in turn-off, lack of self-turn-off capability (this application can achieve automatic tracking, automatic turn-on and turn-off), and electromagnetic interference (this application avoids circulating current short circuits and reverse voltage).

[0053] In at least one embodiment of this application, in order to design shifting logic, determining that a gear shift is required includes the processor determining the gear shift based on a sampled voltage value. For example, the secondary voltage of the transformer is collected and the difference is calculated with the secondary voltage required by the main circuit to determine the direction of change of the transformer output voltage; the primary voltage of the transformer is collected and the actual required primary voltage is calculated; based on the actual required primary voltage and the transformer transmission loss, the transformer voltage regulation ratio is calculated to determine the gear to be switched.

[0054] Furthermore, this application also provides a system for implementing the above method, such as... Figure 2 As shown, the system includes: a control circuit comprising multiple control branches corresponding one-to-one with the multi-thyristor; and a processor connected to each of the multiple control branches. The multi-thyristor connects the input AC power supply to the input terminals of different voltage taps on a power transformer (not shown), and the control terminal of each thyristor is connected to the output terminal of one of the multiple control branches. By switching different thyristors, the input voltage is adjusted to maintain a relatively stable output voltage.

[0055] like Figure 2 As shown, the control circuit includes five control branches: S1-1, S1-2, S1-3, S1-4, and S1-5. Of course, it can also include more or fewer control branches. The +10%, +5%, 0, -5%, and -10% shown in the diagram are preset voltage regulation ratios. TB1 is the power supply transformer; TCA is the tap changer that regulates the voltage and feeds power to the main power supply circuit. TB1 and TCA together form the voltage regulation output of the power supply circuit. Modules 1 to 9 in the five control branches (i.e., branches 1, 2, 3, 4, and 5) have the same function.

[0056] In at least one embodiment of this application, in order to realize the control circuit to control the multiple thyristors, the control circuit is designed as multiple modules: blocking gate trigger working path selection 1, trigger control module 2, transmission isolation module (outward) 3, trigger drive module 4, current zero crossing detection module 5, transmission isolation module (inward) 6, judgment and waiting module 7, fast blocking module 8 and blocking path selection 9.

[0057] In at least one embodiment of this application, in order to control the predetermined delay time, the current zero-crossing detection module 5 is designed to include a waveform correction circuit and an RC delay timing circuit, such as... Figure 3 As shown.

[0058] The blocking gate trigger selection 1 and blocking selection 9 can be implemented using CD4081 AND gate logic modules of different specifications. The trigger control module 2 can be implemented using a ULN2803 driver module. The transmission isolation module (outward) 3 and transmission isolation module (inward) 6 can be implemented using 4N40 optocouplers of different specifications. The judgment and waiting module 7 can be implemented using a voltage comparator connected to an LM258. The fast blocking module 8 can be implemented using an NE555 timer circuit. The structure of the trigger drive module 4 is as follows: Figure 4 As shown, the current zero-crossing detection module 5 is implemented by voltage and current sensors, and its structure is as follows: Figure 3 As shown.

[0059] The following is based on Figure 2 Figure 2 The example system is used as an example to illustrate the on-load voltage regulation method of the above-mentioned thyristor without circulating current and reverse voltage impact.

[0060] (1) When the circuit is powered on, the thyristors S1-1, S1-2, S1-3, S1-4, and S1-5 corresponding to channels 1 to 5 are in an instantaneous off state because they have not received an on command. When the thyristors are off, the current zero-crossing detection module 5 outputs a high potential signal of "1". The "1" signal is sent to the judgment and waiting module 7 through the transmission isolation module (inward) 6, and then sent to the blocking path selector 9 through the fast blocking module 8. The blocking path selector 9 opens all the doors corresponding to channels 1 to 5, so that they are all in the open state of receiving commands.

[0061] (2) Then, the processor issues an on command to open a certain thyristor based on the voltage data (for example, indicating to open 5 channels). The blocking gate of 5 channels triggers the working channel selection 1 to open the command signal "1" of the current zero-crossing detection module 5 (this command signal is different from the "1" signal detected by the current zero-crossing detection module 5. The "1" signal detected by the module 5 indicates that the corresponding thyristor voltage is high and no current flows through it). The high potential "1" signal causes the trigger control module 2 to also output a high potential. This high potential is transmitted through the transmission isolation module (outward) 3 to open the trigger drive module 4. The module 4 causes the corresponding S1-5 thyristors connected in series on the transformer tap to open.

[0062] (3) After the thyristor S1-5 is turned on, the terminals of the corresponding transformer taps are connected, and the current after voltage regulation is transmitted through the S1-5 thyristor in the order of positive and negative alternation of the sine wave, with no additional waveform distortion.

[0063] (4) After the S1-5 thyristor is turned on, the voltage at both ends of its anode and cathode drops to a low voltage, which is determined as a "0" signal.

[0064] (5) After the low voltage of S1-5 is determined to be a “0” signal, it is transmitted sequentially to the transmission isolation module (inward) 6, the judgment and waiting module 7 and the fast block module 8 through the current zero-crossing detection module 5.

[0065] (6) After receiving the “0” signal, the fast blocking module 8 quickly (400ns in this embodiment) blocks all the signal inputs of the thyristors (i.e., channels 1-4) except for channel 5 through the blocking path selector 9, and does not allow any command to be executed on them (e.g., opening). This blocking signal ensures that channel 5 is the only circuit that is open.

[0066] (7) The S1-5 thyristors transmit the full cycle of the sine wave in alternating positive and negative order without additional waveform distortion. If the processor does not send a shutdown command during operation, the thyristors will continue to run in alternating positive and negative order for the full cycle.

[0067] (8) When the voltage of the external circuit changes, the processor issues a command to shut down the 5th channel and at the same time issues a switching command to open a certain channel. At this time, due to the conduction of the thyristor of the 5th channel, the corresponding blocking gate triggering working channel selection 1 of other channels is blocked by the "0" signal issued by S1-5 and cannot pass through. Only the blocking gate triggering working channel selection 1 of the 5th channel is open, and it can transmit the command to close this channel.

[0068] (9) This shutdown command is transmitted through the trigger control module 2 to the transmission isolation module (outward) 3 and sent to the trigger drive module 4, so that the opening command is cancelled.

[0069] (10) Although the turn-on command of S1-5 is cancelled, the thyristor's turn-on characteristic is that either the current passing through it is exhausted or a reverse turn-off voltage is applied, otherwise it will not turn off. Therefore, this turn-off command can only wait for the thyristor current to be exhausted when it crosses the zero point, that is, wait for the current to decay to zero on the zero-crossing axis of the thyristor before applying a reverse voltage to turn it off. For this reason, we set up a waveform correction circuit and an RC delay timing circuit inside the current zero-crossing detection module 5, and used the time constant of the RC delay timing circuit (i.e., the product of R and C) to set the predetermined delay time in order to eliminate loop current and reverse voltage.

[0070] (11) After eliminating the loop current and reverse voltage, the thyristor waits for the reverse voltage after the zero-crossing of the current through the current zero-crossing detection module 5 on the current zero-crossing axis. At this time, since the carrier current in the thyristor has been eliminated, there will be no high reverse overvoltage impact after the reverse voltage arrives, effectively avoiding the thyristor from being impacted by the reverse high voltage. At this time, the thyristor has been cut off, and the reverse voltage will appear between its anode and cathode as a normal sinusoidal voltage rise value after the natural current zero-crossing point. This voltage value is zero on the current axis. If it is a near-purely resistive load, it will coincide with the current axis on the voltage zero axis. If it is an inductive or mixed load, it will be at the starting point after the current axis shows a lag or lead voltage phase α. Its amplitude satisfies the product of the sine value of the phase angle α and the transformer voltage amplitude when all the thyristors on all taps on the thyristor are cut off.

[0071] (12) After the thyristor is turned off, the voltage rises between the anode and cathode and reaches a certain amplitude. The corresponding current zero-crossing detection module 5 will send a signal "1" representing the turn-off. This "1" signal is sent to the transmission isolation module (inward) 6, and then enters the judgment and waiting module 7.

[0072] (13) After being judged as a “1” signal, it passes through the fast blocking module 8 and enters the blocking route selection 9.

[0073] (14) After receiving the signal “1”, the blocking route selector 9 quickly releases the previously issued blocking signal “0”, making it “1”, and releases all blocking gates of each route. The working route selector 1 is then unlocked and opened.

[0074] (15) After receiving the “1” signal and unlocking each blocking gate, the blocking path selector 9 will execute the opening command to open a certain thyristor, so that the trigger drive module 4 will open quickly and the corresponding thyristor to be opened will be turned on immediately.

[0075] (16) After the corresponding thyristor is turned on, the current zero-crossing detection module 5 connected to the cathode and anode of the thyristor determines that its voltage has dropped and sends a “0” signal.

[0076] (17) After the current zero-crossing detection module 5 sends out the "0" signal, it is transmitted to the blocking path selection 9 through modules 6-8 in sequence. It immediately blocks all the channels of the blocking gate trigger working path selection 1 corresponding to all other thyristors except this one. It is not allowed to open the thyristor before the periodic operation shutdown instruction arrives, until the processor issues a new switching instruction based on the collected voltage change.

[0077] (18) After the new processor conversion instruction arrives, the output waveform is continuously output in full cycles, without additional harmonics, and with stable voltage, without short-circuit current impact and reverse voltage impact generated by current, so that the thyristor can work in a safe environment.

[0078] Compared with traditional thyristor voltage zero-crossing synchronous triggering control methods and thyristor current zero-crossing synchronous control methods, the on-load tap regulation method and system provided in this application have the following technical advantages.

[0079] (1) This application can automatically track the thyristor and delay for a period of time after the current accurately crosses zero at the axis position before turning off the previously turned-on thyristor. The purpose of waiting for a period of time is to completely dissipate the charge carriers accumulated in the thyristor after the sine wave of the turned-off thyristor naturally crosses zero. Applying a reverse voltage to the thyristor to be turned off without waiting for a period of time will generate a very large instantaneous current, which will induce a very high overvoltage in the circuit inductor and break down the thyristor. This delay time also avoids the current of the turned-off thyristor never overlapping with the current of the newly turned-on thyristor, which would cause current circulation and form a short circuit.

[0080] This sampling method for trigger control differs from conventional zero-crossing detection methods for voltage and current synchronization. Conventional sampling methods, whether voltage waveform zero-crossing sampling, current transformer current zero-crossing sampling, series resistor or diode sampling, or sampling using optocouplers, inevitably involve sampling in complex inductive loads that are not purely resistive, especially in highly inductive loads and constantly changing loads. Even worse, sampling can occur at the initial power-on moment or under conditions of strong interference, sometimes without any synchronization pulse for the current zero-crossing. In these situations, non-triggering, false triggering, premature triggering, or delayed triggering can easily lead to the simultaneous activation of both thyristors, causing a thyristor short circuit and consequently a transformer short circuit, resulting in a momentary short circuit and system collapse. A more common problem is that the current of the previously turned-on thyristor has not yet completely crossed zero, or the current has crossed zero but the charge carriers inside the tube have not dissipated, or have not dissipated completely, when the next thyristor has already turned on and applied a reverse voltage to the previously turned-on thyristor to force it to turn off. The huge instantaneous current generated by the undissipated charge carriers inside the tube will generate a very high reverse voltage in the strong inductor circuit. When this reverse voltage exceeds the withstand voltage of the thyristor, even if the time is very short, the thyristor will be instantly broken down and burned out.

[0081] To prevent the impact of circulating current short circuits and overvoltages mentioned above, a reliable and stable detection method that accurately detects the zero-crossing point of the thyristor, free from external interference and misjudgment, is crucial. The method involves using a sensor to detect the high voltage ("1") and low voltage ("0") signals at the cathode and anode of the thyristor during turn-off, and using this signal as the sole basis for controlling the thyristor's turn-on and turn-off transitions. This method is clear-cut, accurate, and reliable, and is theoretically considered one of the most reliable methods. This completely avoids the possibility of misjudgment, making it a highly accurate and reliable trigger control method for the thyristor's quasi-current zero-crossing.

[0082] (2) After the current passing through the thyristor is less than the holding current, the time of the holding current of the thyristor after zero crossing is used as the basis for judging the thyristor turn-off "1". Although it is not the theoretical zero crossing point, it is the actual zero crossing turn-off time of the thyristor in actual operation. It is real, accurate, stable and reliable. Theoretically, it will not be affected by other electrical signals and zero crossing voltage jitter. It is the best method for high-stability thyristor zero crossing trigger control at present.

[0083] (3) After the current passing through the thyristor is less than the holding current, the time of the thyristor's holding current after the zero crossing is used as the quasi-current zero crossing of the thyristor to determine the thyristor's turn-off "1" as the thyristor zero crossing trigger control. This quasi-current zero crossing is the real zero current time period flowing through the circuit during operation. This time period changes automatically with the lead or lag of the actual operating current of the circuit. It belongs to the automatic tracking phase zero crossing change. It is always in true synchronization with "current zero crossing". Using it as the thyristor zero crossing trigger will not cause false triggering situations such as "loss of synchronization" and "synchronization instability".

[0084] (4) Using a quasi-current zero-crossing trigger thyristor in conjunction with a self-powered trigger thyristor, the waveform is continuous and smooth when the thyristor is overcurrent commutating at the zero-crossing point, without additional harmonic interference, so that the power supply is kept green.

[0085] (5) When the thyristor is triggered by the zero-crossing of the quasi-current, the crossover distortion time zero-crossing segment that occurs when the thyristor switches between each other varies from tens of microseconds to hundreds of microseconds depending on the voltage applied to the thyristor. This time can be considered to be continuous for the switching of the thyristors.

[0086] (6) The method of automatic tracking thyristor quasi-current zero-crossing trigger control is used. Since the zero-crossing detection control time is accurate, the commutation and mutual conversion of the thyristor when crossing the zero point are both carried out near the current zero point. The thyristor is not subjected to continuous and instantaneous current impacts, and there will be no overvoltage impacts caused by current impacts at its two ends. The commutation and mutual conversion are carried out when the current is zero and there is no current flow. The smooth conversion process without current impacts plays a great role in ensuring the reliable operation and extended service life of the thyristor.

[0087] (7) The thyristor is controlled by the automatic tracking thyristor quasi-current zero-crossing trigger control method. With the various blocking and timely unlocking circuits shown in the attached figure, when the circuit is working, after the first thyristor is opened, the triggering circuits of all other thyristors are immediately blocked, and no other thyristor is allowed to open. This ensures the uniqueness of the thyristor opening and prevents the occurrence of short circuits and overcurrent caused by the false triggering of more than two thyristors at any time.

[0088] (8) When the thyristor to be turned on is turned on, according to the signal given by the sensor, the trigger control signals of other thyristors are blocked while waiting for the change of the control command. If the control command does not issue a command to turn off the thyristor in this circuit and turn on other thyristors, the thyristor will continuously switch to the reverse phase to continue to turn on the thyristor, so that there will be no current discontinuity.

[0089] (9) Once the turned-on thyristor receives a turn-off command, it will prepare a command to turn on a certain thyristor, but this command will not be executed under the control of the blocking signal. The previously turned-on thyristor will not turn off immediately after the current passing through it reaches the quasi-current zero crossing, because there is no turn-on command. Instead, it will wait for a period of time for the charge carriers inside the tube to dissipate before turning off naturally. In this way, both instantaneous current generation and reverse voltage surge can be avoided.

[0090] (10) After one thyristor receives the shutdown command, the other thyristors remain in the off state. After the quasi-current crosses zero, its sensor detects and sends a "1" signal to unlock the blocking circuit. At the same time as the blocking is unlocked, the newly indicated thyristor turns on. After the newly turned-on thyristor turns on, it sends a "0" signal to block all other thyristors from having any turn-on signals or irrelevant signals such as interference or circuit jitter. In this way, the handover of the conversion is completed, and any possible false triggering and the influence of interference near the zero point on the conversion are avoided.

[0091] (11) When one thyristor turns off at the quasi-current zero crossing and another thyristor turns on, the voltage and current sensing must wait for the voltage to rise according to the commutation law of the previous thyristor after the quasi-current crosses zero. During this period, there will be a short current wait at the current zero crossing point. This wait time varies depending on the performance of the thyristor and the power supply voltage applied to the thyristor, and is generally between tens of microseconds and hundreds of microseconds. This wait time occurs when there is no current flowing through any thyristor, so there will be no turn-off back surge current and the reverse peak surge voltage generated by this current, effectively protecting the thyristors for safe and reliable switching. At the same time, since the interruption of tens to hundreds of microseconds on the zero current time axis is relatively short and close to the continuous current switching, there is no significant voltage drop, which will not affect the normal operation of many circuits.

[0092] (12) After the new thyristor is turned on, a "0" signal is quickly sent. This "0" signal immediately blocks the trigger signal path of other thyristors. The locking time from the turn-on of the new thyristor to the issuance of the blocking command is generally several hundred nanoseconds. This fast blocking signal can almost avoid any interference and influence on the turned-on thyristor. It can effectively prevent thyristor switching failure when thyristors working in a severely interfered environment are interchanged.

[0093] Any process or method described in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing custom logic functions or processes, and the scope of the preferred embodiments of this application includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as should be understood by those skilled in the art to which embodiments of this application pertain.

[0094] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus or device (such as a computer-based system, a processor-included system or other system that can fetch and execute instructions from, an instruction execution system, apparatus or device).

[0095] The features described above in the disclosed embodiments can be substituted or combined with each other, enabling those skilled in the art to implement or use this application. The above descriptions are merely preferred embodiments of this application and are not intended to limit this application in any way. Although this application has been disclosed above with reference to preferred embodiments, it is not intended to limit this application. Any person skilled in the art can make many possible variations and modifications to the technical solutions of this application using the disclosed methods and techniques, or modify them into equivalent embodiments with equivalent changes, without departing from the scope of the technical solutions of this application. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of this application without departing from the content of the technical solutions of this application still fall within the protection scope of the technical solutions of this application.

Claims

1. A method for on-load voltage regulation of thyristors without circulating current or reverse voltage surge, characterized in that, include: The processor instructs the control circuit to issue a first turn-on command to turn on the first thyristor; After receiving the "0" signal from the control circuit, the processor quickly instructs the control circuit to issue a first blocking command to other thyristors to block them. If a gear shift is required, the processor sends a first shutdown command to the first thyristor to put the first thyristor into a standby state, and instructs the control circuit to send a second turn-on command to turn on the second thyristor. After a predetermined delay time, the processor instructs the control circuit to apply a reverse voltage to the first thyristor, and after the processor receives a "1" signal from the control circuit, it instructs the control circuit to issue a first deblocking control signal. Before the control circuit issues the first unblocking control signal, the control circuit continuously issues the first blocking command; The "0" signal indicates that the voltage across the first thyristor is low and current is flowing through it, the "1" signal indicates that the voltage across the first thyristor is high and no current is flowing through it, the predetermined delay time is determined based on the performance of the first thyristor and the reverse voltage, and the first unblocking control signal indicates that the first thyristor is turned off and allows the other thyristors to be turned on.

2. The method according to claim 1, characterized in that, The predetermined delay time is completed on the axis where the current crosses zero and is determined by the waveform correction circuit and the RC delay timing circuit.

3. The method according to claim 2, characterized in that, The predetermined delay time ranges from tens of microseconds to hundreds of microseconds, and the time from the first thyristor being turned on to the issuance of the first blocking command is hundreds of nanoseconds.

4. The method according to claim 1, characterized in that, After the first thyristor is turned on, the process further includes: the first thyristor transmitting current to the power transformer in a full cycle of positive and negative alternation in the order of a sine wave without additional waveform distortion, until the first turn-off command is received.

5. The method according to claim 1, characterized in that, Also includes: After power-on, set all thyristors to the momentary off state.

6. The method according to claim 5, characterized in that, The thyristors in each path are bidirectional thyristors or bidirectional thyristors composed of two unidirectional thyristors connected in reverse.

7. The method according to claim 1, characterized in that, The determination requires gear shifting, including the processor determining gear shifting based on the sampled voltage value.

8. A thyristor-based on-load tap changer system with no circulating current and no reverse voltage surge, characterized in that, include: The control circuit includes multiple control branches that correspond one-to-one with the multi-channel thyristors; The processor is connected to each of the plurality of control branches; The multi-channel thyristor connects the input AC power to the input terminals of different voltage taps on the power transformer, and the control terminal of each thyristor is connected to the output terminal of one of the multiple control branches.

9. The system according to claim 8, characterized in that, Each of the multiple control branches includes a blocking door trigger working path selection, a trigger control module, a transmission isolation module (outward), a current zero-crossing detection module, a transmission isolation module (inward), a judgment and waiting module, a fast blocking module, and a blocking path selection.

10. The system according to claim 9, characterized in that, The current zero-crossing detection module includes a waveform correction circuit and an RC delay timing circuit.

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