Overvoltage and harmonic suppression circuit and system of alternating current power supply network

Abstract

The invention discloses an overvoltage and harmonic suppression circuit and system of an alternating current power supply network, relates to the technical field of harmonic and voltage jump suppression of the alternating current power supply network, and is suitable for the technical field of single-phase alternating current power supply and three-phase alternating current power supply. The technical problem that in the prior art, overvoltage of different energy sources cannot be comprehensively protected, and resonance overvoltage occurring at multiple positions in a circuit cannot be comprehensively protected is solved. One end of a first switch is connected with one end of a power supply side overvoltage absorption part Ry, and the other end of the first switch is connected with one end of a load side overvoltage absorption part Rf; the other end of the power supply side overvoltage absorption component Ry is connected with the other end of the load side overvoltage absorption component Rf; the power supply side overvoltage absorption part Ry and the load side overvoltage absorption part Rf are the same in structure, and the nonlinear valve plate B is connected with the silicon carbide valve plate in series and then connected with the nonlinear valve plate A in parallel. The power supply circuit is suitable for being used in alternating current power supply equipment to optimize the power supply circuit.

Description

Technical Field

[0001] This invention relates to the field of harmonic and voltage surge suppression technology in AC power grids, and is applicable to both single-phase and three-phase AC power supply technologies. Background Technology

[0002] In AC power grids, transformers, motors, inductors, capacitors, and switching devices are frequently used on the load side. When a switch is closed or opened, the current in the circuit changes suddenly. Because transformers, motors, and other inductors, as well as lines and cables, have nonlinear characteristics in storing and releasing electrical energy, overvoltages can occur when current and voltage change abruptly during circuit operation. These overvoltages may originate from the following situations: 1. Since the current across an inductor cannot change abruptly, when the windings of transformers, motors, and other devices with ferromagnetic coils suddenly stop flowing, the energy stored within them will inevitably generate a current-cutting overvoltage.

[0003] 2. Since the voltage across a capacitor cannot change abruptly, when capacitive devices and equipment such as lines and cables are switched on or off, their terminal voltage will instantaneously release an overcurrent in the circuit.

[0004] 3. When inductors and capacitors coexist in the same circuit, LC oscillations may occur under certain conditions, resulting in resonant overvoltage. This type of resonant overvoltage can occur on both the power supply side and the load side in AC power grid applications.

[0005] In addition to the situations mentioned above, circuits may also be affected by external overvoltages such as lightning strikes or sudden circuit changes during daily use, which can also cause overvoltage situations. These situations can lead to damage or failure of electronic equipment, or even fire or explosion. Therefore, preventing overvoltage interference and properly handling it are essential for the safe and stable operation of circuits.

[0006] The problems that exist in the operation of the above circuit are not new discoveries, but have always existed and are technical problems that the art has been eager to solve. This technical problem is also an important technical topic that those skilled in the art are committed to studying.

[0007] In existing technologies, the commonly used technical measure is to connect a varistor or a zinc oxide surge arrester into the circuit. These methods all have the following problems: 1. From the principle perspective: When a varistor is placed on the load side, it can function when the switch is closed. However, when the switch is open, the power supply side circuit loses its protection. At this time, the resonant overvoltage on the power supply side or the overvoltage introduced externally loses its protection measures. For AC power grids, the resonant overvoltage on the power supply side can lead to the burnout or even explosion of the transformer, seriously threatening electrical safety. In other words, this existing technology cannot provide comprehensive protection for different energy sources, nor can it effectively prevent resonant overvoltages from occurring in multiple places in the circuit.

[0008] 2. When traditional varistors and zinc oxide surge arresters encounter prolonged overvoltages in the circuit, such as resonant overvoltages (which are continuously replenished by the power frequency power supply, so as long as the resonance condition is not broken, they will continue to exist, and their energy can be said to be "infinite"), or large internal overvoltages, their current carrying capacity is very small and their energy capacity is limited. They will first burn out due to thermal collapse, and thus the circuit will lose protection.

[0009] 3. No matter what kind of overvoltage occurs in the circuit, if it cannot be effectively suppressed, it will spread throughout the entire circuit, causing impact or damage to the insulation of all components.

[0010] 4. Frequent overvoltages in the circuit, if no effective limiting measures are taken, will cause cumulative insulation damage to solid insulating devices under long-term voltage, leading to rapid aging and failure. Summary of the Invention

[0011] This invention solves the technical problems of existing technologies that cannot provide comprehensive protection against overvoltages from different energy sources and resonant overvoltages occurring in multiple locations in a circuit.

[0012] Option 1: Overvoltage and harmonic suppression circuit for AC power grid, the suppression circuit including a first switch and an overvoltage absorption component R on the power supply side. y and load-side overvoltage absorption component R f One end of the first switch is connected to the overvoltage absorption component R on the power supply side. y One end is connected to the load-side overvoltage absorption component R. f One end is connected; the power supply side overvoltage absorption component R y The other end and the load-side overvoltage absorption component R f The other end is connected; The power supply side overvoltage absorption component R y and load-side overvoltage absorption component R f The structures are the same, with the power supply side overvoltage absorption component R... y It includes a nonlinear valve plate A, a nonlinear valve plate B, and a silicon carbide valve plate; the nonlinear valve plate B is connected in series with the silicon carbide valve plate and then in parallel with the nonlinear valve plate A.

[0013] Further optimization scheme: The threshold voltage of the nonlinear valve plate B connected in series with the silicon carbide valve plate is lower than the threshold voltage of the nonlinear valve plate A.

[0014] Further optimization scheme: Both the nonlinear valve A and the nonlinear valve B are voltage-sensitive nonlinear valves, and their maximum current threshold is 500A.

[0015] Further optimization scheme: Both the nonlinear valve plate A and the nonlinear valve plate B are zinc oxide resistance valve plates.

[0016] Option 2: An overvoltage and harmonic suppression system for an AC power grid, the suppression system comprising N overvoltage and harmonic suppression circuits for the AC power grid, and further comprising a first voltage transformer, a second voltage transformer, a controller, a load-side inductor, a load-side capacitor, and 2N switching switches; The N power supply side overvoltage absorption components R in the N suppression circuits y The components are connected in parallel to form a power supply side overvoltage absorption assembly, and each power supply side voltage absorption component R y A switching switch is connected in series; the N load-side overvoltage absorption components R in the N suppression circuits f The load-side overvoltage absorption components are connected in parallel to form an overvoltage absorption assembly, and each load-side overvoltage absorption component R f A switching switch is connected in series; N is an integer between 3 and 8. The first switches in N suppression circuits are combined into a master switch; The first voltage transformer is connected in series between the overvoltage absorption component on the power supply side and the power supply; the second voltage transformer is connected in series between the overvoltage absorption component on the load side and the load; the load-side inductor and the load-side capacitor are connected in parallel to the power supply input terminal of the load. The controller is used to control the operating status of 2N switching switches.

[0017] Further optimization scheme: The parameters of the N suppression circuits are set in binary capacity hierarchy.

[0018] Further optimization: The controller incorporates a control method implemented by a computer program, and the control method is as follows: Real-time acquisition of power supply side voltage U1 and load side voltage U L ; The switching method on the power supply side is as follows: When U1 spike ∈[2U1 ref ,5U1 ref], and when the duration is short (1-5ms), U1 ref U1 is the rated voltage of the power supply. spike The peak voltage of U1; Overvoltage absorption component R from the power supply side with maximum unit capacity y Start switching on and off, gradually decreasing the switching capacity of the power supply-side overvoltage absorption components R. y ; WhenU 1-spike ∈[1.5U 1-ref 2.5U 1-ref [and the duration is long, 5-20ms;] Overvoltage absorption component R from the power supply side with minimum unit capacity y Start switching on and off, gradually increasing the switching on of the overvoltage absorption components R on the power supply side with larger unit capacity. y until ΔU1≤ΔU1 hyst The ΔU1 is the change in U1 obtained from two consecutive samplings. Indicates the actual switching hysteresis threshold; when And when the rate of change of the power supply voltage dv / dt > 2kV / μs, Switching the minimum unit capacity power-side overvoltage absorption component R y until dv / dt ≤ 2kV / μs; The load-side switching method is as follows: when ,and And when the duration is 50-200μs, Overvoltage absorption component R from the large unit capacity load side f The switching process begins with gradually decreasing the switching capacity of the overvoltage absorption components R on the load side, starting with smaller unit capacities. f until The The maximum allowable rate of change of current on the load side. express U L Peak voltage, This indicates the rated voltage of the inductor in the LC filter circuit of the power supply on the load side; WhenU L It exhibits periodic oscillations, the oscillation frequency ,and And when the duration is long, such as 10-50ms, Overvoltage absorption component R on the load side with small unit capacity f Start switching on and off, gradually increasing the switching on of the overvoltage absorption component R on the load side with a larger unit capacity.f until the oscillation ends; L is the inductance value of the load-side inductor, and C is the capacitance value of the load-side capacitor; When the load is connected U L The decrease is greater than U L-ref ×2.7% and duration 1-5ms; Stepwise disconnection of the large unit capacity load-side overvoltage absorption component R f until U L Restore to [ U L-ref Δ U L hyst , U L-ref +Δ U L hyst Within the range; When the load is disconnected, U L rise at least U L-ref ×2.7% and duration 1-5ms; Install a 2-unit capacity load-side overvoltage absorption component R f Then, add the remaining load-side overvoltage absorption components R. f until U L Restore to [ U L-ref Δ U L hyst , U L-ref +Δ U L hyst Within the specified range, and no reverse current is generated.

[0019] Further optimization: The response time of the switching switch is less than or equal to 10μs.

[0020] Further optimization: The switching switch uses a thyristor.

[0021] Further optimization scheme: The sampling error of the controller in acquiring the inductance values ​​of the first voltage transformer and the second voltage transformer is less than or equal to ±0.5%.

[0022] Compared with existing technologies, this invention can more effectively absorb and release sudden changes in electrical current on both the power supply side and the load side of the AC power grid, effectively suppressing harmonic oscillations and overvoltage phenomena, and further enhancing the withstand capability and system resilience of the power supply system circuit. Specific beneficial effects include: The AC power supply network overvoltage and harmonic suppression circuit and system described in this invention includes components for overvoltage absorption on both the power supply side and the load side. These components are the power supply side overvoltage absorption component R. y and load-side overvoltage absorption component R f The two are connected by a switch, which can effectively suppress various overvoltages encountered by the circuit, especially resonant overvoltages that are prone to recurrence and have a long duration. This avoids the cumulative damage to the insulation of the device, accelerated aging, or even failure caused by the long-term action of resonant overvoltages, and significantly improves the system's anti-disturbance capability and operational resilience under complex operating conditions.

[0023] The AC power grid overvoltage and harmonic suppression system described in this invention, through a controller and multiple suppression circuits, controls the switching of corresponding suppression circuits according to the circuit operation, realizing intelligent parallel and zoned protection processing, making the protection more complete and reliable. It can also absorb the arc energy between the contact ports of all switches in the circuit, thereby significantly reducing the contact erosion time and extending the service life of the switches.

[0024] The AC power supply network overvoltage and harmonic suppression circuit of the present invention includes an overvoltage absorption component R on the power supply side. y and load-side overvoltage absorption component R f The circuit structure of all circuits adopts a structure in which a nonlinear valve B is connected in series with the silicon carbide valve and then in parallel with the nonlinear valve A. One branch is equipped with a silicon carbide valve. The resistance-temperature response rate can be flexibly adjusted by controlling the working state of the silicon carbide valve. The reverse current suppression effect is improved by 50%, and the risk of branch overload burnout is reduced by 95%. For load disturbances of different energy levels, the synergistic energy discharge efficiency of silicon carbide valve and nonlinear valve is improved by 40%. Even when subjected to long-term, high-energy overvoltage, the device can still work stably, and the system's shock resistance is significantly enhanced.

[0025] The overvoltage absorption component R on the power supply side of the overvoltage and harmonic suppression circuit of the AC power grid described in this invention y and load-side overvoltage absorption component R f By using a bypass-to-ground discharge scheme, the energy of overvoltage is prevented from entering the main circuit, further improving the stability of system operation.

[0026] The AC power grid overvoltage and harmonic suppression circuit described in this invention has a simple structure, high reliability, can be used for an extended period of time, and is flexible in application.

[0027] The AC power grid overvoltage and harmonic suppression system of the present invention uses a first voltage transformer and a second voltage transformer respectively set on the load side and the power supply side for voltage sampling. This enables the voltage deviation on the power supply side to be controlled within ±1.8%, and the inductor voltage fluctuation range on the load side to be compressed to ±2.7%, thus completely solving the coupling interference problem of "paying attention to one side but losing attention to another" in traditional global regulation.

[0028] The AC power grid overvoltage and harmonic suppression system described in this invention configures the capacity of the voltage absorption components inside the power supply-side and load-side overvoltage absorption components using a binary hierarchical approach. This enables multi-level fine adjustment of the switching mechanism, achieving comprehensive optimization of adjustment flexibility and adaptability. It can cover overvoltage scenarios ranging from microvolt-level voltage fluctuations to several times the rated voltage. For small deviations, fine-tuning is achieved through small unit capacity levels; for large energy disturbances, strong discharge is achieved through combinations of large unit capacity levels. The energy utilization rate of the devices is increased to over 85%, and compared to traditional fixed-capacity solutions, the incidence of over-regulation and under-regulation is reduced by 90%. Combined with voltage sampling from the first and second voltage transformers, the protection against transformer-side current-cutting overvoltage and load-side LC resonant overvoltage is significantly enhanced, reducing the risk of cumulative insulation damage to equipment by over 70%.

[0029] The AC power grid overvoltage and harmonic suppression system described in this invention, in the switching method implemented by the controller, can adaptively adjust according to the disturbance characteristics through the load-side dynamic hysteresis threshold model, reducing the number of frequent switching operations of the switching switch by 60% and extending its service life by 2-3 times; at the same time, the threshold is dynamically matched to scenarios such as inductor freewheeling and load sudden changes, shortening the voltage recovery time to 100-200μs, and reducing the system downtime failure rate caused by voltage fluctuations by 80%.

[0030] The AC power grid overvoltage and harmonic suppression system described in this invention eliminates the need for high-cost continuously adjustable resistive devices or complex filter circuits. High-precision regulation can be achieved through graded resistive absorption branches, thyristor switching, and PWM control, significantly reducing the overall cost. The circuit topology is simple, the controller logic is clear, and it can be directly adapted to the upgrading of existing AC power grids. Construction and maintenance are simple, making it highly practical.

[0031] The overvoltage and harmonic suppression circuit and system for AC power supply networks described in this invention are applicable to AC power supply equipment and optimize the power supply circuit. Attached Figure Description

[0032] Figure 1 This is a simulation circuit diagram of the overvoltage and harmonic suppression circuit of the AC power supply network described in Embodiment 1 during normal operation. Figure 2 for Figure 1The circuit diagram shown is a simulation circuit diagram when a sudden change occurs or when the circuit is subjected to an external overvoltage. Figure 3 for Figure 1 The circuit diagram shown is a simulation of the current-cutting overvoltage generated when the first switch 4 trips under protection or receives a command to close or open. Figure 4 This is a simulation circuit diagram of an AC power supply network overvoltage and harmonic suppression system as described in Embodiment 5; Figure 5 A simulated circuit diagram of the Δ-Y composite wiring for the overvoltage absorption component; Figure 6 A simulated circuit diagram of YOG wiring for an overvoltage absorption component; Figure 7 This is a simulated circuit diagram of a Y-connected overvoltage absorption component; Figure 8 This is a simulated circuit diagram of the Δ connection for the overvoltage absorption component.

[0033] Reference numerals: Nonlinear valve plate A1, Nonlinear valve plate B2, Silicon carbide valve plate 3, First switch 4, Overvoltage absorption component on the power supply side R y 5. Overvoltage absorption component R on the load side f 6. First voltage transformer; 7. Second voltage transformer; 8. Controller; 9. Main switch; 10. Power supply side overvoltage absorption component; 11. Load side overvoltage absorption component; 12. Detailed Implementation

[0034] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0036] Implementation Method 1: Refer to Figure 1 , Figure 2 , Figure 3 , Figure 5 , Figure 6 , Figure 7 ,as well as Figure 8 This embodiment describes an overvoltage and harmonic suppression circuit for an AC power supply network. The suppression circuit includes a first switch 4 and a power supply-side overvoltage absorption component R. y 5 and load-side overvoltage absorption component R f6; One end of the first switch 4 is connected to the overvoltage absorption component R on the power supply side. y One end of 5 is connected, and the other end is connected to the overvoltage absorption component R on the load side. f One end of 6 is connected; the power supply side overvoltage absorption component R y The other end of 5 and the overvoltage absorption component R on the load side f The other end of 6 is connected; The power supply side overvoltage absorption component R y 5 and load-side overvoltage absorption component R f The structure of 6 is the same, except that the power supply side overvoltage absorption component R y 5 includes a nonlinear valve plate A1, a nonlinear valve plate B2, and a silicon carbide valve plate 3; the nonlinear valve plate B2 is connected in series with the silicon carbide valve plate 3 and then connected in parallel with the nonlinear valve plate A1.

[0037] In existing power supply systems, once the main switch between the power supply system and the load is disconnected, the circuit is divided into two independent overvoltage regions. That is, the main switch not only plays a control role in the circuit, but also divides the entire circuit into two regions when and after it is disconnected. One side is the power supply side, including AC power supply, transformer secondary winding, etc.; The other side is the load side, which includes the motor, wiring, cables, and LC filters, among other load components.

[0038] This situation presents a direct challenge: existing technologies typically only install varistors or zinc oxide surge arresters on the load side. Since the main switch operates in two different states—one fully connected and the other partially isolated—when closed, the varistor or surge arrester can suppress overvoltage and harmonic oscillations. However, when open, the power supply side loses protection. Furthermore, when open, the circuit is divided into two different operating states: a power supply side region and a load side region. These two regions differ in their overvoltage generation mechanisms, energy sources, and dynamic characteristics such as harmonic oscillations. Therefore, using traditional varistor devices or surge arresters in both regions is insufficient for providing continuous and comprehensive protection against overvoltages and harmonic oscillations from different sources within each region. Moreover, under prolonged, high-energy overvoltage conditions, these devices are prone to overload failure.

[0039] To solve the above problems, this embodiment provides power supply side overvoltage absorption components R on both sides of the main switch (i.e., the first switch 4). y 5 and load-side overvoltage absorption component R f6. When the main switch is closed, it can provide joint protection for the entire circuit; when the main switch is open, it can provide independent protection for the power supply side and the load side. At the same time, by adopting a composite structure in the overvoltage absorption component, which combines a nonlinear valve A1 with a series branch of a nonlinear valve B2 and a silicon carbide valve 3, and prioritizing the operation of the series branch, and forming a parallel current shunting with another branch during continuous impact, it can balance the rapid initial response to overvoltage and the ability to withstand large energy over long periods. Combined with the bypass to ground discharge method, the sudden energy is absorbed and discharged in time in the corresponding area, preventing it from entering the main circuit and spreading, thereby achieving complete and reliable protection against overvoltages from different energy sources on both sides of the main switch.

[0040] The first switch 4 described in this embodiment can be selected according to the requirements of the power supply system. For example, a relay switch can be used.

[0041] The suppression circuit described in this embodiment is applied to a device with a single-phase AC power supply. It is connected in series between the power supply and the load. The circuit principle is as follows: Figure 1 As shown in the figure, the left side represents the power supply, which includes an AC power source and a transformer. The power output from the secondary coil of the transformer serves as the input power for the suppression circuit described in this embodiment. The right side represents the load side, and the LC filter circuit in the power supply circuit of the load device is directly connected to the suppression circuit described in this embodiment.

[0042] The circuit described above is divided into five functional areas from left to right: AC power supply and transformer area, power supply side overvoltage absorption component R y 5. Access area, first switch 4, load-side overvoltage absorption component R f 6. The connection area and the load area including inductor L and capacitor C.

[0043] In the AC power supply and transformer section of the above circuit, the AC power supply and transformer are connected. The primary coil of the transformer is connected to the AC power supply, and the secondary coil is connected to the main circuit power supply. The secondary coil itself has inductance and distributed capacitance. This is the first area where "energy mutation" can occur and generate overvoltage.

[0044] To the right of the first switch 4 are inductive loads such as motors and capacitive loads such as lines and cables. The load side has inductive load devices and distributed capacitance and capacitive load devices, which is the second area where "energy mutation" can occur and generate overvoltage.

[0045] The power supply side overvoltage absorption component R y 5. Overvoltage absorption components in the access area and on the load side R f The access area 6 is used in the circuit to absorb, discharge, and suppress various overvoltages, such as current-cutting overvoltages, sudden energy surges, resonant overvoltages, and lightning overvoltages. When the electrical equipment is in normal operating condition, see [reference needed]. Figure 1 As shown, the nonlinear valves in each overvoltage absorption component are in a high-resistance state, do not participate in the normal operation of the main circuit, and have no impact on the operation of the circuit system.

[0046] When the circuit system encounters an abnormal state and generates overvoltage, see [reference needed]. Figure 2 As shown, the power supply side overvoltage absorption component R y 5 and load-side overvoltage absorption component R f At the same time, circuit 6 will switch to low resistance and conduct in parallel, as shown by the dotted line in the diagram. In this state, energy is rapidly discharged to ground, thus providing reliable safety protection for the entire circuit system.

[0047] The first switch 4 plays a control and protection role in the circuit and is an essential and important device.

[0048] When the first switch 4 is closed or opened, a sudden current change may occur simultaneously on both sides of the switch in the circuit. On the left side of the first switch 4, the energy stored in the transformer's ferromagnetic coil inductance and capacitance needs to be released instantaneously. Similarly, on the right side of the first switch 4, the inductive and capacitive loads also need to release energy instantaneously. This results in a current-cutting overvoltage occurring simultaneously on both sides of the first switch 4 in the circuit, causing the overvoltage absorption components R connected to the power supply side on both sides of the switch to... y 5. Overvoltage absorption component R on the load side f The terminal voltage of 6 will rise rapidly at the same time, causing them to jump to a low-resistance state and conduct, discharging energy to ground. See [link to documentation]. Figure 2 and Figure 3 The diagram shows the energy discharge path indicated by the dashed line when the first switch 4 is closed and open, respectively, so that the circuits on both sides of the first switch 4 are protected.

[0049] In this embodiment, the power supply side overvoltage absorption component R y 5 and load-side overvoltage absorption component R f 6. A bypass-to-ground discharge method is adopted to absorb and release sudden overvoltages. Although this method may be accompanied by short-term fluctuations in local ground potential caused by instantaneous discharge current and increased heat load on the discharge branch under normal circumstances, this embodiment separates the suppression circuits on both sides of the main switch, so that the overvoltage energy is absorbed locally and discharged to ground in the corresponding area, avoiding its diffusion along the main circuit. At the same time, through the composite structure of nonlinear valve A1 and "nonlinear valve B2 and silicon carbide valve 3 series branch" connected in parallel, the rapid conduction in the initial stage of overvoltage and the parallel current diversion in the continuous impact stage are realized, reducing the risk of single branch overload and thermal collapse. In addition, under normal operating conditions, each overvoltage absorption component maintains a high resistance state and does not participate in the normal operation of the main circuit, thereby effectively suppressing the additional adverse effects that may be caused by ground discharge, and will not have a significant adverse impact on the normal power supply and function of the system.

[0050] After the overvoltage disappears, the overvoltage absorption component R on the power supply side... y 5. Overvoltage absorption component R on the load side f 6. It will automatically return to the high-impedance state without manual intervention; the system will resume operation. See [link / reference]. Figure 1 As shown. Even if the first switch 4 in the circuit is in the open state and the circuit stops operating, the overvoltage absorption component R on the power supply side will still function. y 5. Overvoltage absorption component R on the load side f The presence of 6 can also prevent interference from external overvoltage, thus protecting the relevant parts.

[0051] When the first switch 4 in the circuit is closed or opened, the inductor and capacitor circuits on the load side are prone to oscillation and resonant overvoltage; under certain parameter conditions, resonant overvoltage may also occur in the power supply side region. Load-side overvoltage absorption component R... f 6 is installed on the busbar between the first switch 4 and the load side. When the first switch 4 is disconnected, it plays a role in absorbing, discharging and stabilizing the voltage of various overvoltages encountered in the load area.

[0052] When a sudden change (i.e., internal overvoltage) occurs during circuit operation or when it is subjected to an external overvoltage, the overvoltage absorption component R on the power supply side... y 5. Overvoltage absorption component R on the load side f 6. A discharge current will flow through both devices (e.g.) Figure 2 , Figure 3 (As shown by the dashed line), allowing sudden energy to pass through the power supply side overvoltage absorption component R. y 5. Overvoltage absorption component R on the load side f Six pairs of ground are discharged, thereby ensuring the stability, safety, and reliability of the entire circuit.

[0053] The power supply side overvoltage absorption component R y 5. Overvoltage absorption component R on the load side f 6 in Figure 2 and Figure 3 Role changes in various states

[0054] The power supply side overvoltage absorption component R described in this embodiment y 5. Overvoltage absorption component R on the load side f The left branch of circuit 6 consists of a single nonlinear valve plate A1. This branch exhibits high resistance under normal voltage. When the voltage rises to its set response voltage threshold, its resistance rapidly jumps to a low resistance state. Therefore, it can instantaneously carry extremely large currents, effectively absorbing and discharging massive amounts of energy, reliably preventing overvoltage formation. The right-side branch consists of a nonlinear valve B2 and a silicon carbide valve 3 connected in series, thus introducing the silicon carbide valve 3. This branch exhibits high resistance under normal voltage. Similarly, when the voltage rises to its set response voltage threshold, its resistance rapidly jumps to a low-resistance state. Therefore, it can instantaneously carry extremely large currents, effectively absorbing and discharging massive amounts of energy, reliably preventing overvoltage formation. This branch differs from the left-side branch in that, due to the series connection of the silicon carbide valve 3, its terminal voltage increases with increasing current and prolonged flow time. This further prompts the nonlinear valve A1, connected in parallel, to reach its activation threshold and conduct, thus forming a parallel current shunt state. Through this terminal voltage increase process, a dynamic transition from rapid response of a single branch to coordinated energy dissipation of two branches can be achieved, thereby reducing the risk of overload and thermal collapse caused by long-term current carrying in the first-conducting branch. This solves the technical problems of insufficient withstand capability of the suppression circuit under long-term, high-energy overvoltage conditions and the difficulty in balancing protection sensitivity and withstand capability.

[0055] The suppression circuit described in this embodiment can be applied to various AC power supply networks, including single-phase AC power supply networks and three-phase AC power supply networks.

[0056] For a three-phase AC power supply network, four connection methods are given as examples below: Δ-Y composite wiring method: See Figure 5 As shown, a power supply-side overvoltage absorption component R is connected in parallel between AB, AC, and BC of the three-phase power supply. y 5. Connect a power supply-side overvoltage absorption component R in series between A, B, C and O respectively. y 5. Connect a power supply-side overvoltage absorption component R in series between O and ground. y 5.

[0057] YOG wiring method: See Figure 6 As shown, a power supply-side overvoltage absorption component R is connected in series between the three-phase power supplies A, B, and C and O respectively. y 5. Connect a power supply-side overvoltage absorption component R in series between O and ground. y 5.

[0058] Y-type wiring method: See Figure 7 As shown, a power supply-side overvoltage absorption component R is connected in series between the three-phase power supplies A, B, and C and O. y 5. O is connected to the Earth term.

[0059] Δ wiring method: See Figure 8 As shown, a power supply-side overvoltage absorption component R is connected in parallel between AB, AC, and BC of the three-phase power supply. y 5.

[0060] Implementation Method 2: This implementation method is an optimized design of the overvoltage and harmonic suppression circuit of the AC power supply network described in Implementation Method 1. In this implementation method, the threshold voltage of the nonlinear valve plate B2 connected in series with the silicon carbide valve plate 3 is lower than the threshold voltage of the nonlinear valve plate A1.

[0061] In the circuit structure design: Utilizing the different characteristics of the two branches, the threshold voltage of circuit A, which includes nonlinear valve plate B2 and silicon carbide valve plate 3, is set to be lower than the threshold voltage of circuit B, which includes nonlinear valve plate A1. This allows circuit A to be the first to switch to a low-resistance state and conduct when it encounters an overvoltage and reaches its set threshold, rapidly absorbing and dissipating the overvoltage energy in the circuit. If the overvoltage energy is large and the duration is long, the resistance of silicon carbide valve plate 3 in this branch will increase, causing the terminal voltage of circuit A to rise. When it continues to rise to the threshold voltage of circuit B, circuit B will also quickly switch to a low-resistance state and conduct, forming a parallel working state of the two branches. They share the high current for a long time and can also protect and back up each other, greatly improving the working capability and reliability of the devices themselves and significantly enhancing the resilience of the system.

[0062] Implementation Method 3: This implementation method is an optimized design of the overvoltage and harmonic suppression circuit of the AC power supply network described in Implementation Method 1. In this implementation method, both the nonlinear valve A1 and the nonlinear valve B2 are high-capacitance, low-field-strength voltage-sensitive nonlinear valves.

[0063] In this embodiment, the nonlinear valve plate A1 and the nonlinear valve plate B2 are preferably high-capacitance, low-field-strength voltage-sensitive nonlinear valve plates. Preferably, ceramic nonlinear resistors can be used. Further, ceramic nonlinear resistors with a residual voltage ratio of 3 to 4, an average electric field strength of 25 to 38 V / mm per millimeter thickness, and a maximum current of not less than 5000 A can be selected. When the voltage increases, the resistance of the ceramic nonlinear resistor increases nonlinearly, which can absorb overcurrent or overvoltage, and has the characteristics of high capacity and not being easily damaged by overcurrent.

[0064] Implementation Method 4: This implementation method is an optimized design of the overvoltage and harmonic suppression circuit of the AC power supply network described in Implementation Method 1. In this implementation method, both the nonlinear valve A1 and the nonlinear valve B2 are zinc oxide resistance valves.

[0065] In this embodiment, the maximum flow threshold of the nonlinear valve plate is set to 500A, and the threshold warning line is set to 400A.

[0066] Implementation Method 5: Refer to Figure 4This embodiment describes an overvoltage and harmonic suppression system for an AC power grid. This embodiment includes N suppression circuits as described in any one of embodiments one through four, and further includes a first voltage transformer 7, a second voltage transformer 8, a controller 9, a load-side inductor, a load-side capacitor, and 2N switching switches. The N power supply side overvoltage absorption components R in the N suppression circuits y 5 components are connected in parallel to form a power supply side overvoltage absorption assembly 11, and each power supply side voltage absorption component R y 5. A switching switch is connected in series; the N load-side overvoltage absorption components R in the N suppression circuits f 6 components are connected in parallel to form a load-side overvoltage absorption assembly 12, and each load-side overvoltage absorption component R f A switching switch is connected in series with 6; N is an integer between 3 and 8; The first switch 4 in the N suppression circuits is combined into the master switch 10; The first voltage transformer 7 is connected in series between the overvoltage absorption component 11 on the power supply side and the power supply; the second voltage transformer 8 is connected in series between the overvoltage absorption component 12 on the load side and the load; the load-side inductor and the load-side capacitor are connected in parallel to the power supply input terminal of the load. The controller 9 collects the inductance signals from the first voltage transformer 7 and the second voltage transformer 8, and also outputs 2N switching control signals to 2N switching switches respectively to control the working state of each switching switch.

[0067] In this embodiment, the capacity parameter of the nonlinear valve plate is not simply equivalent to a fixed resistance value, but a comprehensive parameter used to characterize its protection capability. The resistance parameter is one of the specific characterization methods of the capacity parameter, and preferably includes equivalent resistance threshold, dynamic resistance value, current carrying capacity and / or energy dissipation capacity.

[0068] The suppression system described in this embodiment is applied to a device powered by a single-phase AC power supply. It is connected in series between the power supply and the load. The circuit principle is as follows: Figure 4 As shown in the figure, the left side is the power supply, which includes the power supply and the transformer: the voltage output from the secondary winding of the transformer serves as the working power supply for the suppression system described in this embodiment, and the secondary voltage of the transformer is the power supply side voltage U1.

[0069] In the figure, the middle part is the suppression system described in this embodiment, which includes an induction control component, namely a controller 9, a first voltage transformer 7, a second voltage transformer 8; a main switch 10, a switching switch, a power supply side overvoltage absorption component 11, and a load side overvoltage absorption component 12. When working, the controller 9 receives the induced voltage from the first voltage transformer 7 and the second voltage transformer 8 and further outputs a signal to the switching switch to control the power supply side overvoltage absorption component 11 and the load side overvoltage absorption component 12 to connect to the suppression system and control the state of the main switch 10.

[0070] In the diagram, the right side is the load side. Directly connected to the suppression system described in this embodiment is the LC filter circuit in the power supply circuit of the load device. It is connected in series with the second voltage transformer 8 to obtain the sampling inductor voltage, which is the load side voltage U. L .

[0071] In this embodiment, the controller 9 implements the control of the switching on and off using PWM control.

[0072] 1. Switching criteria for transformer side (power supply side overvoltage absorption component 11) based on Figure 1-3 Overvoltage absorption component R on the power supply side y The "double parallel nonlinear branch" structure of 5 refers to the nonlinear valve plate B2 and silicon carbide valve plate 3 being connected in series and then in parallel with the nonlinear valve plate A1, combined with the inductance of the transformer secondary (L). B ), distributed capacitance (C) B The energy storage characteristics and the differences between different overvoltage types (current cut-off, resonance) are analyzed. The criteria are refined from four dimensions: sampling accuracy requirements, dynamic threshold calculation, scenario-specific switching logic, and feedback verification, to ensure the accuracy of switching and the reliability of the devices.

[0073] (1) Preconditions for judgment: voltage sampling and parameter calibration The core basis for switching the power supply side overvoltage absorption component 11 is the power supply side voltage U1, which needs to be sampled with high precision through the first voltage transformer 7 to meet the following requirements: Sampling accuracy: Sampling frequency ≥ 10kHz (covering the 10-100kHz frequency band of resonant overvoltage to avoid missing high-frequency spikes); Signal filtering: The sampled signal needs to be filtered by an RC low-pass filter (R... filt =2.2kΩ, C filt =1.5μF), filtering out electromagnetic interference while ensuring a response time ≤100μs (faster than the rise time of the current-cutting overvoltage, about 200-500μs). Rated value calibration: U1 ref (Transformer secondary rated voltage) needs to be corrected for grid fluctuation coefficient, i.e., U1 ref =U rated ×1.18 (U) rated (Nominal rated voltage).

[0074] According to the transformer secondary L B C B Parameters, pre-calculated basic values ​​required for switching criteria, ensuring that the criteria are adapted to transformer characteristics: Inductance energy storage calculation: Maximum energy storage of the transformer secondary winding (I) 1-max (This is the maximum rated current of the transformer secondary), used to match the energy absorption capacity of the power supply side overvoltage absorption component 11; Resonant frequency calculation: If the oscillation frequency of the sampled voltage is equal to f res This is determined to be a resonant overvoltage, and the switching response needs to be enhanced. Hysteresis threshold benchmark: Initial hysteresis threshold (The allowable range of normal fluctuations takes into account system sensitivity) can be dynamically adjusted according to the type of overvoltage (e.g., increase to 2.7% during resonant overvoltage to avoid frequent switching).

[0075] (2) The controller 9 collects the signal from the first voltage transformer 7, makes further judgments, and outputs a trigger signal to control the on / off state of the switching switch.

[0076] 2. Switching criteria for load-side overvoltage absorption component 12 The load-side overvoltage absorption component 12 is located between the main switch 10 and the load (inductor L + capacitor C in parallel). It needs to address three typical disturbances: inductor freewheeling, LC resonance, and load sudden changes, in conjunction with the load-side voltage U of the second voltage transformer 8. L Sampling, load energy storage characteristics, and the load-side overvoltage absorption component R in the load-side overvoltage absorption assembly 12. f The 6-branch conduction logic refines the criteria from four dimensions: sampling adaptation, dynamic threshold correlation, scenario-based switching, and feedback anti-backflow, to achieve precise control of load-side voltage and energy.

[0077] (1) Preconditions for judgment: load-side sampling and parameter adaptation The switching of the load-side overvoltage absorption component 12 is based on the load-side voltage U. L The sampling requirements are as follows: The sampling needs to be matched to the characteristics of the load side, which include "numerous high-frequency spikes and large current change rate". Sampling accuracy: error ≤ ±0.3%, sampling frequency ≥ 20kHz (covering the 10-50kHz frequency band of inductor freewheeling peaks to avoid missing microsecond-level fluctuations); Signal filtering: A second-order RC low-pass filter (R) is used. filt2 =600Ω, Cfilt2 =0.06μF), which not only filters out load switching noise, but also ensures a response time ≤50μs (faster than the rise time of the inductor freewheeling voltage, about 100μs). Rating value calibration: Inductor rated voltage U L-ref It is necessary to consider the inductor's volt-second characteristics (U) L =L×(di / dt))correction, that is ( (This refers to the maximum allowable rate of change of current for the load).

[0078] The energy disturbance on the load side comes from the magnetic field energy of the inductor L and the electric field energy of the capacitor C. Key parameters need to be pre-calculated to match the absorption capacity of the overvoltage absorption component 12 on the load side. Inductive energy storage: (I) L max (This refers to the maximum rated current of the load). Capacitor energy storage: (U) C max (The maximum allowable voltage of the capacitor). (2) The controller 9 collects the signal from the second voltage transformer 8, makes further judgments, and outputs a trigger signal to control the on / off state of the switching switch.

[0079] Implementation Method Six: This implementation method is an optimized design of the AC power supply network overvoltage and harmonic suppression system described in Implementation Method Five. In this implementation method, the parameters of the N suppression circuits are set in binary capacity levels.

[0080] The binary capacity grading refers to setting the capacity values ​​of multiple components in a binary manner. For example, when N is 3, the capacity ratio of the three suppression circuits is 1:2:4. By controlling the switching switch, seven combinations can be performed to obtain seven capacity values, thereby achieving seven levels of fine adjustment.

[0081] The seven fine-tuning levels are as follows:

[0082] Power supply side: 1. To avoid over- or under-treatment, feedback verification should be performed within 100-200μs after treatment, and the treatment combination should be dynamically adjusted: Over-switching verification: If all overvoltage absorption components 11 on the power supply side are switched on, U1 < -U 1-hyst (U1 is below the lower limit), the following logic applies: Prioritize cutting off the overvoltage absorber with the largest capacity in the large-capacity load-side overvoltage absorption assembly 12 (e.g., first cut off the 4-capacity power-side overvoltage absorption assembly R).y 5. Then cut the power supply side overvoltage absorption component R with a capacity of 2. y 5) Each resection is spaced 60 μs apart (to avoid a sudden increase in U1); if ΔU1 is still < -0.5ΔU after resection 1-hyst Further remove the 1-capacity power-side overvoltage absorption component R. y 5, until U1 returns to [U 1-ref -ΔU1 hyst U 1-ref +ΔU1 hyst ]scope.

[0083] Under-switching check: If, after activating all 11 overvoltage absorption components on the power supply side, ΔU1 still > 1.18ΔU 1-hyst (U1 exceeds the upper limit by 118%), which is judged as under-switching: If the entire group of power supply side overvoltage absorption components 11 is not in operation, supplement the remaining resistors (e.g., power supply side overvoltage absorption components R with a capacity of 2 are already in operation). y 5. Then, install a 4-capacity power supply-side overvoltage absorption unit R. y 5) If all of the overvoltage absorption components 11 on the power supply side are engaged, the backup protection is triggered: the main switch 10 is controlled to trip after a delay (2ms delay to avoid false tripping), and the nonlinear valve A1 branch continues to discharge energy until U1 drops to a safe value.

[0084] 2. Criteria and the power supply side overvoltage absorption component R in the power supply side overvoltage absorption assembly 11 y 5-way dual-branch cooperative logic The switching of the power supply side overvoltage absorption component 11 needs to be coordinated with the conduction characteristics of its internal dual branches to avoid branch overload. Specific coordination rules are as follows: When the total capacity of the power supply side overvoltage absorption component R is ≤3 units, y At 5 o'clock, only the series branch of the nonlinear valve plate B2 and the silicon carbide valve plate 3 is conductive (threshold U). th1 =0.78U th2 The nonlinear valve A1 branch is reserved to avoid frequent operation of the nonlinear valve A1 due to small energy overvoltage. When the total capacity of the power supply side overvoltage absorption component R is ≥4 units, y At 5 o'clock, the voltage at the end of the branch connected in series between the nonlinear valve plate B2 and the silicon carbide valve plate 3 increases to U due to the increased resistance of the silicon carbide valve plate 3. th2 (Nonlinear valve plate A1 threshold) The nonlinear valve plate A1 branch is turned on, and the two branches are connected in parallel to discharge the current, increasing the flow capacity to 2.5 times that of a single branch (to avoid the nonlinear valve plate B2 from burning out due to overcurrent).

[0085] Load side: 1. Feedback verification after application and switching (anti-backflow and dynamic adjustment) There is a risk of reverse current flow due to inductor freewheeling on the load side. This needs to be checked within 100μs after switching to avoid secondary fluctuations. Reverse current verification: Monitor the current direction on the load side: If the current is reversed (flowing from the load to the overvoltage absorption component 12 on the load side), and the reverse current I reverse ≥I L max ×10%, then the overvoltage absorption component R on the high-capacity load side will be cut off. f 6 (e.g., 4 units of load-side overvoltage absorption component R) f 6) At the same time, reduce the dynamic resistance of the silicon carbide valve plate 3 (by adjusting the working state of the silicon carbide valve plate 3 (current, heat dissipation, parallel auxiliary components) by the controller, and indirectly change the rate of change of the dynamic resistance of the silicon carbide valve plate 3) to suppress backflow energy.

[0086] Over / under-throw adjustment: Over-throw cut ( ): Prioritize disconnecting the overvoltage absorption component R on the high-capacity load side. f 6 (4 units → 2 units → 1 unit load-side overvoltage absorption component R) f 6) Each resection should be spaced 30 μs apart to avoid U L A sudden rise; undercut ( ): Replenish the remaining resistors. If the resistors are already fully charged, trigger the "load-side standby damper" (such as the parallel C charging and discharging auxiliary energy discharge).

[0087] 2. The load-side overvoltage absorption component R in the load-side overvoltage absorption assembly 12 f 6-branch cooperative logic The switching of the load-side overvoltage absorption component 12 must be strongly correlated with the conduction characteristics of its internal dual branches to avoid branch overload. When the total capacity of the load-side overvoltage absorption component R is ≤3 units, f 6: Only the nonlinear valve plate B2 and the silicon carbide valve plate 3 are connected in series, while the nonlinear valve plate A1 branch is spared (small energy disturbances do not require dual branches). When the total capacity of the load-side overvoltage absorption component R is ≥4 units, f 6: The voltage at the end of the branch where the nonlinear valve plate B2 and the silicon carbide valve plate 3 are connected in series increases to U due to the increased resistance of the silicon carbide valve plate 3. th2 The nonlinear valve plate A1 branch is open, and the two branches are connected in parallel to discharge current—ensuring the flow capacity while utilizing the dynamic resistance of the silicon carbide valve plate 3 to avoid concentrated energy impact.

[0088] Implementation Method Seven: This implementation method is an optimized design of the AC power supply network overvoltage and harmonic suppression system described in Implementation Method Six. In this implementation method, the controller 9 has a control method implemented by a computer program embedded inside. The control method is as follows: Real-time acquisition of power supply side voltage U1 and load side output voltage U L ; The switching method on the power supply side is as follows: When U1 spike ∈[2U1 ref ,5U1 ref ], and when the duration is short (1-5ms), U1 ref U1 is the rated voltage of the power supply output component. spike This represents the peak voltage of U1. Overvoltage absorption component R from the power supply side with maximum unit capacity y 5. Begin switching on the power supply side overvoltage absorption component R with gradually decreasing switching capacity. y 5; When the amplitude U 1-spike ∈[1.5U 1-ref 2.5U 1-ref [And the duration is long, 5-20ms;] Overvoltage absorption component R from the power supply side with minimum unit capacity y Starting with 5-stage switching, the overvoltage absorption component R on the power supply side with a gradually increasing switching capacity is used to switch on the power supply side. y 5. Until ΔU1≤ΔU1 hyst ; The ΔU1 is the change in U1; when However, the voltage change rate dv / dt > 2kV / μs, which is close to the allowable upper limit. This represents the actual switching hysteresis threshold, where v is the instantaneous voltage value. The numerical change in the secondary voltage of the transformer; Switching the minimum unit capacity power-side overvoltage absorption component R y 5. Until dv / dt ≤ 2kV / μs; The load-side switching method is as follows: when ,and And when the duration is 50-200μs, the The maximum allowable rate of change of current for the load is given by i, where i represents the operating current on the load side. express U LPeak voltage, This indicates the rated voltage of the inductor in the LC filter circuit of the power supply on the load side; Overvoltage absorption component R from the large unit capacity load side f Starting with 6 switches, the overvoltage absorption component R on the load side with gradually decreasing switching capacity is switched on and off in stages. f 6, until ; WhenU L It exhibits periodic oscillations, the oscillation frequency L is the carrier-side inductance, and C is the load-side capacitance; And when the duration is long, such as 10-50ms, Overvoltage absorption component R on the load side with small unit capacity f Starting with 6 switches, the overvoltage absorption components R on the load side with gradually increasing switching capacity are connected in stages. f 6. Until the oscillation ends; L is the inductance value of the load-side inductor, and C is the capacitance value of the load-side capacitor; When the load is connected U L The decrease is greater than U L-ref ×2.7% (i.e., Δ) U L <- U L-ref ×2.7%), and the duration is 1-5ms; Stepwise disconnection of overvoltage absorption component R on the large unit capacity load side f 6, until U L Restore to [ U L-ref Δ U L hyst , U L-ref +Δ U L hyst Rated hysteresis threshold range; When the load is disconnected, U L rise at least U L-ref ×2.7% (i.e., Δ) U L > U L-ref ×2.7%), and the duration is 1-5ms; Install a 2-unit capacity load-side overvoltage absorption component R f 6. Then, add the remaining overvoltage absorption components R on the load side.f 6 until U L Restore to [ U L-ref Δ U L hyst , U L-ref +Δ U L hyst [Rated hysteresis threshold range and no reverse current generated.]

[0089] In this embodiment, the suppression circuit determines the appropriate switching mechanism based on different overvoltage conditions on the load side and the power supply side. This determination process adopts a dynamic hysteresis threshold model.

[0090] In this embodiment, a transformer is used on the power supply side. In this case, U1 ref This is the rated voltage of the transformer's secondary coil.

[0091] The working principle of the dynamic hysteresis threshold model is as follows: 1. When the overvoltage is an external overvoltage, the power supply side: (1) Threshold dynamic calculation formula The actual switching hysteresis threshold is not a fixed value and needs to be considered in conjunction with the overvoltage amplitude. The derivative of the voltage change rate and the real-time adjustment of the state of the power supply side overvoltage absorption component 11 are calculated using the following formulas:

[0092] Coefficient definition: k=0.4 (overvoltage amplitude influence coefficient; the larger the amplitude, the threshold should be appropriately relaxed to avoid excessive switching); k=0.3 (voltage change rate influence coefficient). The maximum allowable voltage rise rate of the transformer secondary winding is set to 5 kV / μs (to avoid insulation breakdown). Physical meaning: The higher the overvoltage amplitude and the faster it rises, the higher the threshold should be to balance "rapid energy dissipation" and "avoiding frequent switching operations".

[0093] (2) Switching logic for different overvoltage types Based on the causes of transformer secondary overvoltage (current throttling, resonance), a differentiated switching strategy is formulated to match R. y The conduction characteristics of the dual-branch system (the branch connected in series with the nonlinear valve plate B2 and the silicon carbide valve plate 3 conducts first, and the nonlinear valve plate A1 is linked with high energy).

[0094] Scenario 1: Overvoltage interruption (triggered by main switch 10 trip) Triggering condition: The moment the main switch is opened to 10 degrees, L B Sudden change in current ( U1 surges U1 spike ∈[2U1 ref ,5U1 ref ], and the duration is short (1-5ms); Throwing and cutting steps: When ΔU1=U1 U1 ref >ΔU1 hyst When the overvoltage absorption component 11 is in operation, priority is given to activating the 4-unit capacity overvoltage absorption component R on the power supply side. y 5. Simultaneously monitor the branch current I of the nonlinear valve plate B2 and the silicon carbide valve plate 3 connected in series. z1 ; If I z1 ≥400A (80% of the upper limit of the nonlinear valve plate current), and U1 still has not decreased, within 30μs, activate 2 units of the power supply side overvoltage absorption component R in the power supply side overvoltage absorption component 11. y 5. At this time, the total capacity of the power supply side overvoltage absorption component 11 is 6 units; If U1 still exceeds the threshold (ΔU1>ΔU1) hyst Then, one unit capacity of the power-side overvoltage absorption component R in the power-side overvoltage absorption component 11 is added. y 5. Triggering the conduction of the branch of nonlinear valve plate A1 (because the voltage at the branch terminals of nonlinear valve plate B2 and silicon carbide valve plate 3 connected in series increases to U as the resistance of silicon carbide valve plate 3 increases). th Rz ), with two branches connected in parallel to discharge and intercept energy; Energy matching: The total capacity of the overvoltage absorption components 11 on the power supply side must meet the W requirement. Ry ≥1.18W L (1.18 is a safety factor to prevent energy overflow from causing thermal collapse of the nonlinear valve plate B2).

[0095] Scenario 2: Resonant overvoltage (L) B -C B Oscillation trigger) Triggering condition: U1 exhibits periodic oscillations with an oscillation frequency f = f res (Pre-calculated resonant frequency), amplitude U1 spike ∈[1.5U1 ref 2.5U1 ref The duration is long (5-20ms); Switching steps: When ΔU1>ΔU 1-hyst When the number of oscillations is ≥3, first activate the power supply side overvoltage absorption component R with a capacity of 1 unit in the power supply side overvoltage absorption component 11. y 5. Damping oscillations using small-capacity resistors; If the oscillation amplitude does not decrease (ΔU1 still > ΔU), 1-hyst Within 50μs, the power-side overvoltage absorption component 11, consisting of 2 units of capacity power-side overvoltage absorption component R, is activated. y 5. Total capacity 3 units, enhanced damping; If the oscillation continues (≥5 times), activate the 4-unit capacity power-side overvoltage absorption component R in the power-side overvoltage absorption component 11. y 5. Forced damped oscillation; Special constraints: Resonant overvoltage requires avoiding the simultaneous deployment of a large-capacity power supply-side overvoltage absorption component R. y 5 (e.g., the power supply side overvoltage absorption component R with a capacity of 4 units in the power supply side overvoltage absorption component 11 is directly connected) y 5) Prevent L B The instantaneous release of energy causes a reverse spike in U1.

[0096] Scenario 3: Normal fluctuations ( ) If U1 is within the threshold range, but the voltage change rate dv / dt > 2kV / μs (close to the allowable upper limit), only one unit capacity of the power supply side overvoltage absorption component R in the power supply side overvoltage absorption component 11 will be activated. y 5. The voltage fluctuation is buffered by the power supply side overvoltage absorption component 11 in a low-resistance state until dv / dt≤2kV / μs, thus preventing it from escalating into an overvoltage. When dv / dt≤2kV / μs, the power supply side overvoltage absorption component R of the power supply side overvoltage absorption component 11 with a capacity of 1 unit can be used. y The nonlinear valve plate B2 and the silicon carbide valve plate 3 are connected in series in the system to achieve high-resistivity standby (leakage current ≤1μA, no power consumption).

[0097] II. On the load side: (1) Core criterion: Threshold dynamic calculation (related to the rate of change of inductor current) Load-side voltage U L The fluctuation is directly related to the rate of change of inductor current di / dt (U L=L×di / dt), therefore the hysteresis threshold ΔU of the load-side overvoltage absorption component 12 L hyst The relationship between di / dt needs to be dynamically correlated, as shown in the following formula:

[0098] Coefficient definitions: k3=0.6 (current change rate influence coefficient; the larger di / dt is, the threshold should be appropriately relaxed for faster response); k4=0.4 (overvoltage amplitude influence coefficient). ΔU L-hyst0 Initial hysteresis threshold, take U L-ref ×2.7% (a wider range of allowable load-side fluctuations); Physical meaning: The faster the inductor current changes and the higher the amplitude, the wider the threshold, which ensures rapid energy dissipation while avoiding frequent switching due to high-frequency fluctuations.

[0099] (2) Scenario-specific switching logic (adapting to typical load disturbances) The core of load-side disturbances is "inductor freewheeling, LC resonance, and sudden load changes," which needs to be addressed in conjunction with the load-side overvoltage absorption component R in the load-side overvoltage absorption assembly 12. f 6. Threshold characteristics of dual-branch (U) th1 =0.78U th2 Develop a differentiation strategy.

[0100] Scenario 1: Inductor freewheeling overvoltage (triggered by load disconnection) Triggering condition: The load (such as a motor) is suddenly disconnected, and the current in inductor L cannot change abruptly, flowing through C or R. f Release magnetic field energy, causing U L sudden rise ( ), The duration is short (50-200μs); Dropping and cutting steps (rapid energy release preferred): when When the load-side overvoltage absorption components 12 are in operation, priority is given to activating the four load-side overvoltage absorption components R. f 6. Utilizing the overvoltage absorption component R on the high-capacity load side f 6. Rapidly absorbs freewheeling energy; at this time, the overvoltage absorption component R on the load side... f The nonlinear valve plate B2 inside 6 is connected in series with the silicon carbide valve plate 3 in the first branch (U) L ≥U th1 ); Monitoring four unit load-side overvoltage absorption components R f Branch current I of 6 f3 : if I f3 ≥I max-f(The overvoltage absorption component R on the load side) f 90% of the maximum current capacity of 6, and U L No decrease; within 20μs, two units of the load-side overvoltage absorption component R were added. f 6. Total capacity reaches 6 units; If U L Still exceeding ΔU L-hyst Invest one unit of load-side overvoltage absorption component R f 6. At this time, due to the increased current to 1.5kΩ, the voltage at the branch terminals of the nonlinear valve plate B2 and the silicon carbide valve plate 3 in the series connection increases. th2 When the nonlinear valve plate A1 branch is turned on, the two branches are connected in parallel to discharge the current, and the flow capacity is increased to 3 times that of a single branch (to avoid the nonlinear valve plate B2 from burning out due to overflow). Energy constraint: The total installed capacity of the load-side overvoltage absorption components 12 must meet the following requirements (W). Rf ≥1.3×W L-load (1.3 is the safety factor, covering the collaborative energy storage of capacitor C).

[0101] Scenario 2: LC resonant overvoltage (triggered by LC parallel oscillation) Triggering condition: Load side L and C form a parallel resonant circuit, U L It exhibits periodic oscillations (frequency) ), amplitude The duration is long (10-50ms); Switching steps (damped oscillations take priority): WhenU L The number of oscillations is ≥3 and ΔU L >ΔU L-hyst At that time, first activate one unit of the load-side overvoltage absorption component R. f 6. Overvoltage absorption component R on the small-capacity load side f 6. Damped resonance (similar to the damping effect of an RC absorber) prevents overvoltage absorption components R on the high-capacity load side. f 6. This results in "instantaneous energy release → reverse spike"; If the oscillation amplitude does not decrease (ΔU) L Still > ΔU L-hyst Within 50μs, two units of the load-side overvoltage absorption component R are deployed. f 6. The total capacity reaches 3 units, enhancing the damping effect; If the oscillation continues for ≥5 cycles, activate 4 units of the load-side overvoltage absorption component R. f 6. The nonlinear valve plate A1 branch is conducting, and the low resistance characteristic of the dual branches forces the damping oscillation. At the same time, the positive temperature coefficient characteristic of the silicon carbide valve plate 3 can avoid the concentrated impact of resonance energy. Special constraint: In resonant scenarios, it is prohibited to simultaneously engage four units of the load-side overvoltage absorption component R. f 6. Otherwise, the magnetic field energy of L will be instantly transferred to C, causing U to... C A sudden increase (exceeding the capacitor's withstand voltage).

[0102] Scenario 3: Sudden load overvoltage (triggered by load increase or decrease) Triggering condition: The load (such as multiple motors connected in parallel) is suddenly connected / disconnected, causing a sudden change in current. ), U L Fluctuation (U during access) L U during temporary descent and disconnection L Temporary rise), duration medium (1-5ms); Switching steps (dynamically adapting to load): If the load is connected to →U L Temporary surrender ( ): Disconnect the load-side overvoltage absorption component R in the already engaged load-side overvoltage absorption assembly 12 f 6 (Prioritize cutting overvoltage absorption components R on the load side with large capacity, i.e., 4 units) f 6) Reduce load-side impedance and improve U L Up to the rated range; If the load is disconnected → U L Temporary promotion ( ): 2 units of load-side overvoltage absorption component R f 6. Energy surplus caused by sudden load changes, if U L The voltage is still fluctuating; add another unit of load-side overvoltage absorption component R. f 6 or 4 units of load-side overvoltage absorption components R f 6; Response constraints: The switching delay in load change scenarios is ≤1ms to avoid triggering undervoltage protection when the load restarts.

[0103] Implementation Method 8: This implementation method is an optimized design of the overvoltage and harmonic suppression system of the AC power supply network described in Implementation Method 5. In this implementation method, the response time of the switching switch does not exceed 10μs.

[0104] In this embodiment, the switching response time of the control circuit is configured to not exceed 10μs. By cooperating with the dynamic hysteresis threshold model, the voltage recovery time can be shortened to 100-200μs.

[0105] Implementation Method Nine: This implementation method is an optimized design of the AC power supply network overvoltage and harmonic suppression system described in Implementation Method Five. In this implementation method, the switching switch adopts a thyristor.

[0106] Implementation Method 10: This implementation method is an optimized design of the overvoltage and harmonic suppression system of the AC power supply network described in Implementation Method 5. In this implementation method, the sampling error between the first voltage transformer 7 and the second voltage transformer 8 does not exceed ±0.5%.

[0107] In this embodiment, the sampling accuracy of the first voltage transformer 7 and the second voltage transformer 8 configured in the control circuit does not exceed ±0.5%. With the help of the dynamic hysteresis threshold model, the voltage deviation on the power supply side can be controlled within ±1.8%, and the voltage fluctuation range on the load side inductor is compressed to ±2.7%, thus completely solving the coupling interference problem of "paying attention to one thing but losing attention to another" in traditional global regulation.

[0108] In this embodiment, the 1 / 2 transformation ratio of the first voltage transformer 7 and the second voltage transformer 8 is matched with the system voltage.

Claims

1. An overvoltage and harmonic suppression circuit for an AC power grid, characterized in that, The suppression circuit includes a first switch (4) and a power supply side overvoltage absorption component R. y (5) and load-side overvoltage absorption component R f (6); One end of the first switch (4) is connected to the overvoltage absorption component R on the power supply side. y (5) One end is connected, and the other end is connected to the overvoltage absorption component R on the load side. f (6) One end is connected; the power supply side overvoltage absorption component R y (5) The other end and the overvoltage absorption component R on the load side f (6) The other end is connected; The power supply side overvoltage absorption component R y (5) and load-side overvoltage absorption component R f (6) has the same structure, wherein the power supply side overvoltage absorption component R y (5) Includes nonlinear valve plate A (1), nonlinear valve plate B (2) and silicon carbide valve plate (3); the nonlinear valve plate B (2) is connected in series with the silicon carbide valve plate (3) and then connected in parallel with the nonlinear valve plate A (1).

2. The overvoltage and harmonic suppression circuit for AC power supply network according to claim 1, characterized in that, The threshold voltage of the nonlinear valve plate B (2) connected in series with the silicon carbide valve plate (3) is lower than the threshold voltage of the nonlinear valve plate A (1).

3. The overvoltage and harmonic suppression circuit for AC power supply network according to claim 1, characterized in that, Both the nonlinear valve A (1) and the nonlinear valve B (2) are voltage-sensitive nonlinear valves, and their maximum current threshold is 500A.

4. The overvoltage and harmonic suppression circuit for AC power supply network according to claim 1, characterized in that, Both the nonlinear valve plate A (1) and the nonlinear valve plate B (2) are zinc oxide resistance valve plates.

5. An overvoltage and harmonic suppression system for an AC power grid, characterized in that, The suppression system includes N suppression circuits as described in any one of claims 1 to 4, and further includes a first voltage transformer (7), a second voltage transformer (8), a controller (9), a load-side inductor, a load-side capacitor, and 2N switching switches; The N power supply side overvoltage absorption components R in the N suppression circuits y (5) Connected in parallel to form a power supply side overvoltage absorption assembly (11), and each power supply side overvoltage absorption component R y (5) Connect a switching switch in series; the N load-side overvoltage absorption components R in the N suppression circuits f (6) Connected in parallel to form a load-side overvoltage absorption assembly (12), and each load-side overvoltage absorption component R f (6) Connect a switching switch in series; N is an integer between 3 and 8; The first switch (4) in the N suppression circuits is combined into the master switch (10); The first voltage transformer (7) is connected in series between the power supply side overvoltage absorption component (11) and the power supply; the second voltage transformer (8) is connected in series between the load side overvoltage absorption component (12) and the load; the load side inductor and the load side capacitor are connected in parallel to the power supply input terminal of the load; The controller (9) is used to control the working status of 2N switching switches.

6. The overvoltage and harmonic suppression system for an AC power supply network according to claim 5, characterized in that, The parameters of the N suppression circuits are set using binary capacity grading.

7. The overvoltage and harmonic suppression system for an AC power supply network according to claim 6, characterized in that, The controller (9) has a control method implemented by a computer program embedded inside it. The control method is as follows: Real-time acquisition of power supply side voltage U1 and load side voltage U L ; The switching method on the power supply side is as follows: When U1 spike ∈[2U1 ref ,5U1 ref ], and when the duration is short (1-5ms), U1 ref U1 is the rated voltage of the power supply. spike The peak voltage of U1; Overvoltage absorption component R from the power supply side with maximum unit capacity y (5) Start switching on and off, gradually decreasing the switching on of the power supply side overvoltage absorption component R with a smaller unit capacity. y (5); WhenU 1-spike ∈[1.5U 1-ref 2.5U 1-ref [and the duration is long, 5-20ms;] Overvoltage absorption component R from the power supply side with minimum unit capacity y (5) Start switching on and off, and gradually increase the switching on of the overvoltage absorption component R on the power supply side with a large unit capacity. y (5) until ΔU1≤ΔU1 hyst The ΔU1 is the change in U1 obtained from two consecutive samplings. Indicates the actual switching hysteresis threshold; when And when the rate of change of the power supply voltage dv / dt > 2kV / μs, Switching the minimum unit capacity power-side overvoltage absorption component R y (5) until dv / dt≤2kV / μs; The load-side switching method is as follows: when ,and And when the duration is 50-200μs, Overvoltage absorption component R from the large unit capacity load side f (6) Start switching on and off, and gradually reduce the switching on and off of the overvoltage absorption components R on the load side with smaller unit capacity. f (6), until The The maximum allowable rate of change of current on the load side. express U L Peak voltage, This indicates the rated voltage of the inductor in the LC filter circuit of the power supply on the load side; WhenU L It exhibits periodic oscillations, the oscillation frequency ,and And when the duration is long, such as 10-50ms, Overvoltage absorption component R on the load side with small unit capacity f (6) Start switching on and off, gradually increasing the switching on of the overvoltage absorption component R on the load side with a large unit capacity. f (6) until the oscillation ends; L is the inductance value of the load-side inductor, and C is the capacitance value of the load-side capacitor; When the load is connected U L The decrease is greater than U L-ref ×2.7% and duration 1-5ms; Stepwise disconnection of the large unit capacity load-side overvoltage absorption component R f (6), until U L Restore to [ U L-ref Δ U L hyst , U L-ref +Δ U L hyst Within the range; When the load is disconnected, U L rise at least U L-ref ×2.7% and duration 1-5ms; Install a 2-unit capacity load-side overvoltage absorption component R f (6) Then, add the remaining load-side overvoltage absorption components R. f (6), until U L Restore to [ U L-ref Δ U L hyst , U L-ref +Δ U L hyst Within the specified range, and no reverse current is generated.

8. The overvoltage and harmonic suppression system for an AC power supply network according to claim 5, characterized in that, The response time of the switching switch is less than or equal to 10 μs.

9. The overvoltage and harmonic suppression system for an AC power supply network according to claim 5, characterized in that, The switching device uses a thyristor.

10. An overvoltage and harmonic suppression system for an AC power supply network according to claim 5, characterized in that, The sampling error of the controller in acquiring the inductance values ​​of the first voltage transformer (7) and the second voltage transformer (8) is less than or equal to ±0.5%.

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