Bypass system and method for ac voltage regulator based on bidirectional asymmetric hardware delay

Abstract

The application relates to the technical field of power safety, in particular to an AC voltage stabilizer bypass system and method based on bidirectional asymmetric hardware delay. The system comprises a main bypass, a protection array, a secondary bypass and a bidirectional asymmetric delay control circuit. The main bypass comprises a mechanical bypass relay K1 connected in parallel to both ends of a primary winding of an AC voltage stabilizer. The protection array comprises a plurality of bidirectional transient voltage suppression diodes TVS connected in parallel to both ends of the mechanical bypass relay K1. The secondary bypass comprises a solid-state switch connected in parallel to both ends of a secondary winding of the AC voltage stabilizer. The bidirectional asymmetric delay control circuit comprises a solid-state switch control circuit and a relay control circuit. The input ends of the solid-state switch control circuit and the relay control circuit are connected with a command end. The output end of the solid-state switch control circuit is connected with a solid-state switch control end. The output end of the relay control circuit is connected with a mechanical bypass relay K1 coil power supply end. A high-level signal of the command end has a lower delay in the solid-state switch control circuit, and a low-level signal has a lower delay in the relay control circuit.

Description

Technical Field

[0001] This application relates to the field of power safety technology, specifically to an AC voltage regulator bypass system and method based on bidirectional asymmetric hardware delay. Background Technology

[0002] In high-power AC voltage regulation systems, to balance low loss and fast response, a hybrid bypass architecture is often used, consisting of a primary-side mechanical relay (near-zero on-resistance, but slow operation) and a secondary-side solid-state switch (microsecond-level response, but with internal resistance). During normal operation, the solid-state switch quickly establishes the bypass, and then the mechanical relay takes over steady-state conduction to reduce power consumption; when exiting the bypass, the switching is reversed. However, this approach has the following inherent drawbacks:

[0003] The timing of the operation is entirely dependent on software, posing a risk of system-level crashes. The coordination timing between the relay and the solid-state switch is controlled by the MCU software timer. Under harsh conditions such as strong electromagnetic interference, the MCU is prone to program crashes, watchdog timer resets, or interrupt blockages, leading to the failure of the software handshake protocol, resulting in a loss of synchronization between the two and causing the relay to disconnect or close under load.

[0004] Secondly, the large current interruption in the out-of-step state generates a devastating arc. When the relay disconnects before the solid-state switch has completed its switching, tens of amperes of current are forcibly interrupted, generating a high-temperature arc between the contacts, instantly burning the contacts, causing permanent damage to the relay or welding and sticking together, and drastically reducing its electrical life to a few hundred cycles.

[0005] Furthermore, parasitic inductance triggers transient energy backflow when the contacts break. The energy stored in the main circuit inductance generates thousands of volts of back electromotive force when the relay disconnects, exacerbating the arc and potentially damaging semiconductor devices. Existing protection circuits mostly rely on software-driven active absorption, which fails to operate within the control blind zone of software failure.

[0006] Therefore, it is necessary to continue researching bypass technology for voltage regulation systems. Summary of the Invention

[0007] This specification describes an AC voltage regulator bypass system and method based on bidirectional asymmetric hardware delay through several embodiments.

[0008] In a first aspect, embodiments of this specification provide an AC voltage regulator bypass system based on bidirectional asymmetric hardware delay, comprising:

[0009] The main bypass includes a mechanical bypass relay K1 connected in parallel across the primary winding of the AC voltage regulator;

[0010] The protection array includes several bidirectional transient suppression diodes (TVS) connected in parallel across the two ends of the mechanical bypass relay K1;

[0011] Secondary bypass, including solid-state switches connected in parallel across the secondary winding of the AC voltage regulator;

[0012] A bidirectional asymmetric delay control circuit includes a solid-state switch control circuit and a relay control circuit. The input terminals of both the solid-state switch control circuit and the relay control circuit are connected to the command terminal BYPASS_CMD. The output terminal of the solid-state switch control circuit is connected to the solid-state switch control terminal, and the output terminal of the relay control circuit is connected to the power supply terminal of the mechanical bypass relay K1 coil. The high-level signal of the command terminal BYPASS_CMD has a lower delay in the solid-state switch control circuit, and the low-level signal has a lower delay in the relay control circuit.

[0013] Secondly, embodiments of this specification provide an AC voltage regulator bypass method based on bidirectional asymmetric hardware delay, including the following steps:

[0014] The BYPASS_CMD command generates a high-level bypass command.

[0015] The solid-state switch control circuit outputs a conduction signal to the solid-state switch with a first delay through the first direction conduction path. When the solid-state switch is turned on, the secondary winding of the AC regulator is short-circuited, causing the voltage across the primary winding to return to zero.

[0016] The relay control circuit outputs a closing signal to the mechanical bypass relay K1 through the second direction delay path with a second delay. The second delay is greater than the first delay. The mechanical bypass relay K1 closes after the voltage across the primary winding returns to zero.

[0017] The BYPASS_CMD command generates a low-level shutdown instruction.

[0018] The relay control circuit outputs a disconnect signal to the mechanical bypass relay K1 through a third-direction delay path with a third delay, and the mechanical bypass relay K1 disconnects.

[0019] The solid-state switch control circuit outputs a turn-off signal to the solid-state switch with a fourth delay through a fourth direction delay path. The fourth delay is greater than the third delay. The solid-state switch turns off after the mechanical bypass relay K1 is disconnected.

[0020] The beneficial effects of the technical solutions provided in some embodiments of this specification include at least the following:

[0021] In several embodiments of this specification, the provided AC regulator bypass system and method eliminate reliance on microprocessor software timing instructions. Utilizing the physical irreversibility of diode unidirectional conductivity and combining the asymmetric delay characteristics of the RC charging and discharging network on the charging and discharging paths, a fully physicalized bidirectional asymmetric handshake protocol is constructed. The timing logic of "solid-state first, relay second; relay first, solid-state third" is solidified in hardware parameters. Even if the microprocessor experiences program crashes or interruptions, the bidirectional asymmetric delay control circuit can still independently execute the preset timing sequence, physically eliminating device conflict conditions caused by software failures. The bypass system constructed with passive devices can achieve reliable and safe bypass state switching under various operating conditions.

[0022] A multi-stage high-energy bidirectional TVS array is connected in parallel across the relay contacts, combined with the delayed turn-off protection of a solid-state switch, forming a dual energy firewall. At the instant the relay is disconnected, the TVS array avalanche conduction rigidly clamps the contact voltage below the safety threshold, depriving the voltage conditions for arc formation; the solid-state switch delays and maintains conduction, providing a follow current discharge path for residual energy.

[0023] Other features and advantages of various embodiments of this specification will be further revealed in the following detailed description and accompanying drawings. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of this specification, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this specification. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of the AC voltage regulator circuit provided in this manual.

[0026] Figure 2 This is a schematic diagram of the bidirectional asymmetric delay control circuit provided in this manual.

[0027] Figure 3 This is a schematic diagram of the bypass method for an AC voltage regulator. Detailed Implementation

[0028] The technical solutions of the embodiments of this specification will be explained and described below with reference to the accompanying drawings. However, the following embodiments are only preferred embodiments of this specification and not all of them. Other embodiments obtained by those skilled in the art based on the embodiments in the implementation methods without creative effort are all within the protection scope of this specification.

[0029] The terms "first," "second," "third," etc., in the description, claims, and accompanying drawings are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to such processes, methods, products, or apparatus.

[0030] In the following description, terms such as “inner,” “outer,” “upper,” “lower,” “left,” and “right” are used only to facilitate the description of the embodiments and to simplify the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this specification.

[0031] All data involved in this application are information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of the relevant data comply with the relevant laws, regulations and standards of the relevant countries and regions.

[0032] Before introducing the technical solutions described in this manual, the application scenarios and related technologies of the technical solutions will be introduced.

[0033] High-power AC voltage regulators are widely used in industrial production lines, large-scale electromechanical equipment, medical imaging systems, broadcast television transmission stations, and other scenarios with stringent power quality requirements. In these applications, fluctuations, drops, or surges in the mains voltage can directly affect the normal operation of the equipment or even cause damage. Therefore, voltage regulators are required to maintain a stable output voltage over a wide input range.

[0034] Series-compensated AC voltage regulators are a mainstream topology. They achieve high-precision regulated output by connecting a compensation transformer in series with the power line, and then using an inverter system to generate a compensation voltage to offset input voltage deviations. Figure 1 As shown in the image.

[0035] Given that this application involves some technical terms, these terms will be introduced below.

[0036] Series-compensated AC voltage regulator: A voltage regulator topology that uses a series compensation transformer to generate a compensation voltage to offset the input voltage deviation, offering high compensation accuracy and fast response.

[0037] Primary winding / secondary winding: The primary winding (primary winding) and secondary winding (secondary winding) of a transformer. (In this invention, a mechanical bypass relay K1 is connected in parallel with the primary winding, and a solid-state switch is connected in parallel with the secondary winding.)

[0038] Mechanical bypass relay: A switching device that uses electromagnetic force to drive mechanical contacts. Its on-resistance is almost zero, but its action delay is on the order of milliseconds, and it has the problem of contact arcing.

[0039] Solid-state switches: Contactless switches made of power electronic semiconductor devices (such as back-to-back MOSFETs) with microsecond-level response, but with on-resistance.

[0040] Hybrid bypass architecture: A bypass scheme that combines mechanical relays and solid-state switches in parallel, taking into account the advantages of both (low loss of mechanical switches and fast response of solid-state switches).

[0041] BYPASS_CMD: Bypass control command signal terminal, which receives bypass on / off commands issued externally.

[0042] High-speed diode: A high-speed switching diode used to provide a signal transmission path with extremely low delay in a specific direction.

[0043] Bidirectional transient voltage suppressor diode (TVS): A high-energy surge protection device that rapidly avalanche conducts when subjected to transient high voltage, clamping the voltage to a safe level and absorbing the back electromotive force energy when the relay contacts open.

[0044] Zero-voltage closing (ZVS): refers to the relay contacts closing when the voltage across them is zero, which can completely avoid contact arcing at the moment of closing.

[0045] Program crash: An abnormal state in which the microprocessor deviates from the normal program execution flow due to electromagnetic interference or other reasons, resulting in the inability to issue timing control instructions as expected.

[0046] In applications, in order to reduce the power consumption of the system in standby or uncompensated conditions, a "hybrid bypass" architecture is often used in engineering: a mechanical bypass relay (with close to zero on-resistance and extremely low power consumption but slow operation) is connected in parallel on the primary side of the transformer, while a solid-state switch (with microsecond-level response speed but certain on-resistance) is connected in parallel on the secondary side, and the two work together to complete the bypass on-off control.

[0047] However, existing hybrid bypass solutions have serious reliability vulnerabilities. The timing of the coordinated operation of the mechanical relay and the solid-state switch relies entirely on the software timer of the microprocessor (MCU). In high-power industrial environments, severe conditions such as strong electromagnetic interference and power grid surges can easily cause the MCU program to crash, the watchdog timer to reset, or the interrupt thread to block. Once the software timing instructions fail, the operation of the two switches will lose synchronization. If the mechanical relay disconnects under load before the solid-state switch has completed switching, tens of amperes of current will generate a high-temperature arc between the contacts, instantly burning the contacts and even causing permanent damage. At the same time, the energy accumulated by the parasitic inductance of the main circuit at the moment of contact disconnection will generate a back electromotive force of several thousand volts, further intensifying the arc and potentially damaging nearby semiconductor devices.

[0048] Therefore, this specification provides an AC regulator bypass system and method based on bidirectional asymmetric hardware delay, which implements the timing logic of "solid-state first turns on and relay then closes when switching into bypass; relay first turns off and solid-state then turns off when switching out of bypass" at the pure hardware level.

[0049] The timing sequence is fixed in the hardware parameters and does not depend on the microprocessor's software timer. Even if the MCU experiences abnormalities such as program crashes, watchdog resets, or interrupt blocking, the delay control circuit can still independently and reliably execute the preset handshake timing sequence.

[0050] This eliminates the catastrophic conflict of solid-state switches and mechanical relays simultaneously turning on or off due to software failure at the physical level.

[0051] Specifically, this embodiment first provides an AC voltage regulator bypass system based on bidirectional asymmetric hardware delay, including:

[0052] The main bypass includes a mechanical bypass relay K1 connected in parallel across the primary winding of the AC voltage regulator;

[0053] The protection array includes several bidirectional transient suppression diodes (TVS) connected in parallel across the two ends of the mechanical bypass relay K1.

[0054] The protection array includes a multi-level high-energy bidirectional TVS array, which is connected in parallel across the contacts of the mechanical bypass relay K1.

[0055] The main bypass circuit consists of a high-capacity mechanical bypass relay K1, whose normally open contacts are connected to both ends of the primary winding of the AC voltage regulator. Mechanical relays have the significant advantage of extremely low on-resistance (typically in the milliohm or even microohm range), allowing them to carry the main circuit current (e.g., 50A power frequency current) with near-zero loss under long-term steady-state bypass conditions, thus significantly reducing system heat dissipation. However, their contact operation relies on the engagement of the electromagnetic coil and spring reset, resulting in an inherent operating delay of several milliseconds to tens of milliseconds, and there is also the problem of arcing at the physical contact points.

[0056] To suppress the destructive arc generated by the mechanical bypass relay K1 during high-current interruption, this embodiment directly connects a multi-stage high-energy bidirectional transient voltage suppressor (TVS) array in parallel across the contacts of K1. This TVS array consists of multiple high-surge-capacity bidirectional TVS diodes connected in series or parallel to match the potential for thousands of volts of transient back electromotive force energy in the system. Its working principle is as follows: when the K1 contact opens first due to a control command while carrying a high current, the magnetic field energy stored in the parasitic inductance of the main circuit (energy value E = 0.5 × L × I) is released. 2 (where L is the parasitic inductance and I is the current value before the break) will generate a high voltage at the break point. Once the voltage exceeds the breakdown threshold of the TVS (for example, set to 600V), the TVS array will instantly avalanche conduction, rigidly clamping the voltage across the contacts below the safe value, and dissipating the inductance energy as heat, thereby depriving the voltage conditions required for arc formation.

[0057] The secondary bypass includes a solid-state switch connected in parallel across the secondary winding of the AC regulator. The secondary bypass also includes a bidirectional switch consisting of back-to-back MOSFETs connected in series, the bidirectional switch being connected across the secondary winding of the AC regulator.

[0058] Solid-state switches employ two power MOSFETs connected in series back-to-back (common-source or common-drain) to form a bidirectional switching structure, enabling controllable turn-on and turn-off under both forward and reverse voltage conditions. MOSFET devices have microsecond (or even sub-microsecond) switching speeds, allowing them to rapidly establish a low-impedance path upon receiving a control signal, short-circuiting the secondary winding. This utilizes the electromagnetic coupling between the primary and secondary windings of the transformer to bring the primary equivalent impedance close to zero, creating the preconditions for zero-voltage closure of relay K1. However, MOSFETs have a certain on-resistance (typically in the milliohm range), which can lead to significant conduction losses under high current and prolonged conduction. Therefore, their role is positioned as transient switching assistance and safety protection, rather than long-term main circuit current carrying.

[0059] A bidirectional asymmetric delay control circuit includes a solid-state switch control circuit and a relay control circuit. The input terminals of both the solid-state switch control circuit and the relay control circuit are connected to the command terminal BYPASS_CMD. The output terminal of the solid-state switch control circuit is connected to the solid-state switch control terminal, and the output terminal of the relay control circuit is connected to the power supply terminal of the mechanical bypass relay K1 coil. The high-level signal of the command terminal BYPASS_CMD has a lower delay in the solid-state switch control circuit, and the low-level signal has a lower delay in the relay control circuit.

[0060] Please participate in the attached document. Figure 2 The solid-state switch control circuit includes a high-speed diode D1. The anode of the high-speed diode D1 is connected to the command terminal BYPASS_CMD. A resistor R11 is connected in parallel across the high-speed diode D1. A capacitor C11 and a resistor R12 are both connected between the cathode of the high-speed diode D1 and the ground terminal. The solid-state switch control terminal is connected at the common node of the cathode of the high-speed diode D1, capacitor C11, and resistor R12.

[0061] The relay control circuit includes a high-speed diode D2, with the cathode of the high-speed diode D2 connected to the command terminal BYPASS_CMD. A resistor R21 is connected in parallel across the high-speed diode D2. A capacitor C21 and a resistor R22 are both connected between the anode of the high-speed diode D2 and the ground terminal. The power supply terminal of the mechanical bypass relay K1 coil is connected to the common node of the anode of the high-speed diode D2, the capacitor C21, and the resistor R22.

[0062] The delay of the BYPASS_CMD low-level signal in the solid-state switch control circuit is set by the capacitance of capacitor C11 and the resistance of resistor R12. Similarly, the delay of the BYPASS_CMD high-level signal in the relay control circuit is set by the capacitance of capacitor C21 and the resistance of resistor R21. This ensures that when the BYPASS_CMD signal is high, the solid-state switch turns on before the mechanical bypass relay K1, and when the BYPASS_CMD signal is low, the solid-state switch turns off after the mechanical bypass relay K1.

[0063] The bidirectional asymmetric delay control circuit consists of two branches with similar structures but different delay responses, which are used to control the solid-state switch and the mechanical bypass relay K1, respectively.

[0064] In the solid-state switch control circuit, the anode of the high-speed diode D1 is connected to the command terminal BYPASS_CMD, and the resistor R11 is connected in parallel across D1. The cathode of D1 is connected to one end of the capacitor C11, one end of the resistor R12, and the control input terminal of the solid-state switch. The other end of C11 and the other end of R12 are grounded together. The resulting RC network exhibits distinct delay characteristics for the rising and falling edges of the BYPASS_CMD signal: when BYPASS_CMD transitions from low to high, D1 is forward-biased, providing a very low-impedance charging path for capacitor C11. The voltage on C11 rises almost synchronously with the rising edge of BYPASS_CMD, resulting in minimal delay. However, when BYPASS_CMD transitions from high to low, D1 is reverse-biased and cut off. The charge stored in C11 can only be slowly discharged to ground through the parallel resistor R12. The discharge time constant is determined by the product of resistor R12 and capacitor C11 (τ=R12×C11), thus achieving a larger turn-off delay.

[0065] In the relay control circuit, the cathode of the high-speed diode D2 is connected to the command terminal BYPASS_CMD, and resistor R21 is connected in parallel across D2. The anode of D2 is simultaneously connected to one end of capacitor C21, one end of resistor R22, and the coil power supply terminal of relay K1. The other end of C21 and the other end of R22 are grounded together. The asymmetric delay characteristic of this branch is complementary to that of the solid-state switch branch: when BYPASS_CMD transitions from high to low, D2 is forward biased, capacitor C21 discharges rapidly through D2, the K1 coil is quickly de-energized, and the relay contacts open rapidly; when BYPASS_CMD transitions from low to high, D2 is reverse biased and cut off, C21 is slowly charged through R21 to the coil pull-in threshold voltage, and K1 thus obtains a significant conduction delay, which is determined by the product of resistor R21 and capacitor C21 (τ=R21×C21).

[0066] The asymmetric delay characteristics of solid-state switch control circuits and relay control circuits enable differentiated timing scheduling with "high priority for entry and low priority for exit".

[0067] Specifically, when switching to bypass, BYPASS_CMD issues a high-level command, and the solid-state switch control branch is rapidly forward-biased through the ultra-fast diode D1. Within microseconds, the solid-state switch is triggered to close, short-circuiting the secondary winding of the transformer. The equivalent impedance of the primary winding instantly returns to zero, and the voltage across the primary winding drops to near zero volts. Subsequently, after a slow charging delay of R21-C21 (approximately 15ms), the relay control branch waits for the voltage of capacitor C21 to rise to the coil pull-in threshold before the mechanical bypass relay K1 closes under zero-voltage conditions, achieving a smooth, arc-free switching.

[0068] When the bypass is switched off, BYPASS_CMD issues a low-level command, and the relay control branch is rapidly forward-biased through the fast diode D2. Capacitor C21 discharges rapidly (less than 0.5ms), the coil of the mechanical bypass relay K1 is de-energized, and the relay contacts are physically disconnected first. At this time, the main circuit current has not been completely cut off, but because a TVS protection array is connected in parallel across the relay contacts, the transient high voltage generated by the contact disconnection is immediately clamped and absorbed, and an arc cannot be formed. During the entire period when the relay has been disconnected, capacitor C11 in the solid-state switch control branch continues to discharge slowly through R12 (about 30ms), keeping the solid-state switch on and providing a low-impedance freewheeling path for the residual inductance energy in the main circuit. Until the voltage of C11 drops below the MOSFET gate turn-off threshold, the solid-state switch is finally safely turned off, and the entire switching-off process is completed.

[0069] On the other hand, in another embodiment, a bypass control bus is also included, with the command terminal BYPASS_CMD connected to the bypass control bus. The bypass on / off state is directly controlled by this system, rather than being determined by an external system.

[0070] For example, in a typical 50A / 220V AC voltage regulator application, if a traditional pure software timing scheme is used, when the MCU is interrupted or blocked due to electromagnetic interference, the relay may close under load before the solid-state switch has fully established conduction, or it may forcibly disconnect before the solid-state switch has turned off, resulting in severe contact erosion. However, with the pure hardware delay control circuit of this embodiment, the above switching timing is fixed in the charging and discharging time constant of the RC network and is completely unaffected by the MCU's operating state. Even in extreme cases where the MCU experiences program crashes, watchdog resets, or even a complete power failure, as long as the level state of the BYPASS_CMD instruction terminal is stable, the two control branches can still independently complete their actions according to the preset asymmetric delay sequence, completely eliminating the possibility of timing conflicts at the physical level.

[0071] On the other hand, this embodiment provides an AC regulator bypass method based on bidirectional asymmetric hardware delay. Please refer to the appendix. Figure 3 The steps include:

[0072] Step S1: The BYPASS_CMD terminal generates a high-level bypass instruction;

[0073] Step S2: The solid-state switch control circuit outputs a conduction signal to the solid-state switch through the first direction conduction path with a first delay. The solid-state switch is turned on, the secondary winding of the AC regulator is short-circuited, and the voltage across the primary winding returns to zero.

[0074] Step S3: The relay control circuit outputs a closing signal to the mechanical bypass relay K1 through the second direction delay path with a second delay. The second delay is greater than the first delay. The mechanical bypass relay K1 closes after the voltage across the primary winding returns to zero.

[0075] Step S4: The BYPASS_CMD terminal generates a low-level shutdown instruction;

[0076] Step S5: The relay control circuit outputs a disconnect signal to the mechanical bypass relay K1 through a third-direction delay path with a third delay, and the mechanical bypass relay K1 disconnects.

[0077] Step S6: The solid-state switch control circuit outputs a turn-off signal to the solid-state switch through the fourth direction delay path with a fourth delay. The fourth delay is greater than the third delay. The solid-state switch turns off after the mechanical bypass relay K1 is disconnected.

[0078] The solid-state switch control circuit and the relay control circuit both use passive charging and discharging networks to achieve delay, and the delay time constant of the high-level signal and the delay time constant of the low-level signal are set independently by different passive charging and discharging paths.

[0079] On the other hand, a protection array is connected in parallel across the mechanical bypass relay K1. The protection array includes several bidirectional transient suppression diodes (TVS). After the mechanical bypass relay K1 is disconnected, the protection array absorbs the transient high voltage energy generated at the moment the contacts of the mechanical bypass relay K1 are disconnected.

[0080] During the initiation phase (bypass establishment):

[0081] When the system needs to switch from compensation mode to bypass mode, the BYPASS_CMD command terminal generates a high-level bypass activation command.

[0082] The solid-state switch control circuit outputs a turn-on trigger signal to the solid-state switch via a first-direction conduction path with a first delay. Specifically, the high-level signal of the command terminal BYPASS_CMD is rapidly turned on in the forward direction via the high-speed diode D1. The cathode potential of D1 rises almost instantaneously, and this potential is directly applied to the gate control terminal of the solid-state switch (back-to-back MOSFET), driving the MOSFET to establish a conduction channel within microseconds (first delay < 1μs). After the solid-state switch is turned on, it short-circuits the two ends of the secondary winding of the AC regulator. According to the working principle of the transformer, when the secondary side is short-circuited, the equivalent impedance of the primary side approaches zero, and the voltage across the primary winding drops rapidly to near zero volts. This state creates a zero-voltage condition for the subsequent closing of the mechanical bypass relay K1 of the main bypass.

[0083] The relay control circuit outputs a closing trigger signal to the mechanical bypass relay K1 via a second directional delay path with a second delay, and this second delay is designed to be much longer than the first delay. Because the high-level signal is blocked by the reverse cutoff of diode D2 in the relay control branch, it cannot pass directly through D2 and must instead integrally charge capacitor C21 through resistor R21. This charging time constant is determined by the product of R21 and C21, and in this embodiment, it is preferably set to approximately 15ms. When the voltage on capacitor C21 gradually rises to the coil pull-in threshold of relay K1, the coil of the mechanical bypass relay K1 is energized, and the contacts close. At this moment, because the solid-state switch has already been turned on and pulled the primary winding voltage to near zero volts, the voltage difference across the contacts of the mechanical bypass relay K1 is almost zero, achieving zero-voltage closing (ZVS) in an absolute sense, and no closing arc is generated between the contacts.

[0084] During the cut-out phase (bypass exit):

[0085] When the system needs to return from bypass mode to compensation mode, the BYPASS_CMD command terminal generates a low-level shutdown command.

[0086] The relay control circuit outputs a disconnect trigger signal to the mechanical bypass relay K1 via a third-direction delay path with a third delay. In the relay control branch, the low-level signal at the command terminal BYPASS_CMD causes diode D2 to turn forward biased, and the charge stored in capacitor C21 is rapidly discharged through D2 (third delay < 0.5ms). The coil voltage of the mechanical bypass relay K1 quickly drops below the release threshold, and the relay contacts are physically disconnected first by the reset spring.

[0087] The solid-state switch control circuit outputs a turn-off trigger signal to the solid-state switch via a fourth-direction delay path with a fourth delay, and this fourth delay is designed to be much longer than the third delay. In the solid-state switch control branch, the low-level signal at the command terminal BYPASS_CMD causes diode D1 to be reverse-biased and cut off. The charge stored in capacitor C11 can only be slowly discharged to ground through resistor R12, and its discharge time constant is determined by the product of R12 and C11, which is preferably set to about 30ms in this embodiment. During this period, although relay K1 has been turned off, the gate voltage of the solid-state switch remains above the MOSFET turn-on threshold, so the solid-state switch continues to be in the on state.

[0088] The resulting effects are as follows: At the moment the mechanical bypass relay K1 disconnects, the inductive loads in the main circuit (such as transformer windings and line parasitic inductance) store a large amount of magnetic field energy, which tends to generate a high-voltage arc at the break point. However, in this method, the solid-state switch remains conducting for a 30ms delay after the mechanical bypass relay K1 disconnects, providing a low-impedance freewheeling path for the inductive load. This allows the residual current in the inductor to form a circuit through the solid-state switch and gradually decay. Simultaneously, the TVS protection array connected in parallel across the contacts of the mechanical bypass relay K1 avalanche conduction instantaneously when the break voltage exceeds its clamping threshold, rigidly clamping and absorbing the remaining energy. These two protection mechanisms work synergistically, doubly suppressing the conditions for arc generation.

[0089] The solution provided in this embodiment transfers the control of the switching timing from the vulnerable software system to a pure hardware delay network. With a minimalist circuit structure, it achieves a safe switching timing of "solid-state first conduction to protect the relay from zero-voltage closure during switching in, and relay first conduction to protect the solid-state delay and provide a freewheeling channel during switching out". Combined with the transient energy clamping of the TVS array, it completely eliminates the problem of relay arcing under high current conditions from a physical perspective, significantly improving the system's reliability, anti-interference ability and service life.

[0090] The embodiments described above are merely preferred embodiments of this specification and are not intended to limit the scope of this specification. Any modifications and improvements made by those skilled in the art to the technical solutions of this specification without departing from the spirit of this specification should fall within the protection scope defined by the claims of this specification.

Claims

1. An AC voltage regulator bypass system based on bidirectional asymmetric hardware delay, characterized in that, include: The main bypass includes a mechanical bypass relay K1 connected in parallel across the primary winding of the AC voltage regulator; The protection array includes several bidirectional transient suppression diodes (TVS) connected in parallel across the two ends of the mechanical bypass relay K1; Secondary bypass, including solid-state switches connected in parallel across the secondary winding of the AC voltage regulator; A bidirectional asymmetric delay control circuit includes a solid-state switch control circuit and a relay control circuit. The input terminals of both the solid-state switch control circuit and the relay control circuit are connected to the command terminal BYPASS_CMD. The output terminal of the solid-state switch control circuit is connected to the solid-state switch control terminal, and the output terminal of the relay control circuit is connected to the power supply terminal of the mechanical bypass relay K1 coil. The high-level signal of the command terminal BYPASS_CMD has a lower delay in the solid-state switch control circuit, and the low-level signal has a lower delay in the relay control circuit.

2. The AC voltage regulator bypass system based on bidirectional asymmetric hardware delay according to claim 1, characterized in that, The solid-state switch control circuit includes a high-speed diode D1. The anode of the high-speed diode D1 is connected to the command terminal BYPASS_CMD. A resistor R11 is connected in parallel across the high-speed diode D1. A capacitor C11 and a resistor R12 are both connected between the cathode of the high-speed diode D1 and the ground terminal. The solid-state switch control terminal is connected at the common node of the cathode of the high-speed diode D1, capacitor C11, and resistor R12. The relay control circuit includes a high-speed diode D2, with the cathode of the high-speed diode D2 connected to the command terminal BYPASS_CMD. A resistor R21 is connected in parallel across the high-speed diode D2. A capacitor C21 and a resistor R22 are both connected between the anode of the high-speed diode D2 and the ground terminal. The power supply terminal of the mechanical bypass relay K1 coil is connected to the common node of the anode of the high-speed diode D2, the capacitor C21, and the resistor R22.

3. The AC voltage regulator bypass system based on bidirectional asymmetric hardware delay according to claim 2, characterized in that, The delay of the low-level signal BYPASS_CMD at the command terminal by the solid-state switch control circuit is set by the capacitance of capacitor C11 and the resistance value of resistor R12, and the delay of the high-level signal BYPASS_CMD at the command terminal by the relay control circuit is set by the capacitance of capacitor C21 and the resistance value of resistor R21.

4. The AC voltage regulator bypass system based on bidirectional asymmetric hardware delay according to claim 3, characterized in that, When the BYPASS_CMD command terminal is high, the solid-state switch turns on before the mechanical bypass relay K1; when the BYPASS_CMD command terminal is low, the solid-state switch turns off after the mechanical bypass relay K1.

5. The AC voltage regulator bypass system based on bidirectional asymmetric hardware delay according to claim 1, characterized in that, The protection array includes a multi-level high-energy bidirectional TVS array, which is connected in parallel across the contacts of the mechanical bypass relay K1.

6. The AC voltage regulator bypass system based on bidirectional asymmetric hardware delay according to claim 1, characterized in that, The secondary bypass includes a bidirectional switch consisting of MOSFETs connected in series back-to-back, and the bidirectional switch is connected to both ends of the secondary winding of the AC regulator.

7. The AC voltage regulator bypass system based on bidirectional asymmetric hardware delay according to claim 1, characterized in that, It also includes a bypass control bus, and the command terminal BYPASS_CMD is connected to the bypass control bus.

8. A bypass method for AC voltage regulators based on bidirectional asymmetric hardware delay, characterized in that, Including the following steps: The BYPASS_CMD command generates a high-level bypass command. The solid-state switch control circuit outputs a conduction signal to the solid-state switch with a first delay through the first direction conduction path. When the solid-state switch is turned on, the secondary winding of the AC regulator is short-circuited, causing the voltage across the primary winding to return to zero. The relay control circuit outputs a closing signal to the mechanical bypass relay K1 through the second direction delay path with a second delay. The second delay is greater than the first delay. The mechanical bypass relay K1 closes after the voltage across the primary winding returns to zero. The BYPASS_CMD command generates a low-level shutdown instruction. The relay control circuit outputs a disconnect signal to the mechanical bypass relay K1 through a third-direction delay path with a third delay, and the mechanical bypass relay K1 disconnects. The solid-state switch control circuit outputs a turn-off signal to the solid-state switch via a fourth direction delay path with a fourth delay. The fourth delay is greater than the third delay. The solid-state switch turns off after the mechanical bypass relay K1 is disconnected.

9. The AC regulator bypass method based on bidirectional asymmetric hardware delay according to claim 8, characterized in that, Both the solid-state switch control circuit and the relay control circuit use passive charging and discharging networks to achieve delay, wherein the delay time constant of the high-level signal and the delay time constant of the low-level signal are independently set by different passive charging and discharging paths.

10. The AC regulator bypass method based on bidirectional asymmetric hardware delay according to claim 8, characterized in that, A protection array is connected in parallel across the mechanical bypass relay K1. The protection array includes several bidirectional transient voltage suppressor diodes (TVS). After the mechanical bypass relay K1 is disconnected, the protection array absorbs the transient high voltage energy generated at the moment the contacts of the mechanical bypass relay K1 are disconnected.

Images