Non-isolated DC-DC converter solid-state protection device and method

Abstract

The invention belongs to the technical field of non-isolated DC-DC converters, and discloses a non-isolated DC-DC converter solid-state protection device and method.The non-isolated DC-DC converter solid-state protection device is composed of a main protection module, a backup protection module, a buffer circuit and a controller, and the main protection module is connected between a converter bridge and a high-voltage-side direct-current filter capacitor and used for rapidly disconnecting the converter bridge and the high-voltage-side direct-current filter capacitor when a fault occurs; the backup protection module is connected in series with the main protection module and provides redundancy protection; the buffer circuit is connected in parallel to two ends of the series module to suppress turn-off overvoltage; and the controller coordinates the main protection process, the backup protection process and the conduction state control of the low-voltage side switch tube. By adopting the device, the fault response speed and protection comprehensiveness can be remarkably improved, reliable active isolation is realized, high-voltage capacitor discharge and low-voltage power supply feed current paths are blocked, the safety of power devices is effectively guaranteed, and cost optimization is considered.

Description

Technical Field

[0001] This invention belongs to the technical field of non-isolated DC-DC converters, and particularly relates to a solid-state protection device and method for non-isolated DC-DC converters. Background Technology

[0002] In the rapid development of emerging fields such as new energy vehicles, energy storage systems, and DC microgrids, the efficiency and reliability of energy conversion equipment have become core industry requirements. Non-isolated DC-DC converters, especially bidirectional DC-DC converters, are widely used in energy exchange scenarios between DC buses of different voltage levels due to their significant advantages of simple structure and high energy conversion efficiency, playing a crucial role in ensuring efficient energy transmission. However, in actual operation, due to various factors such as sudden load changes, component aging, external environmental interference, or improper operation, short-circuit faults are prone to occur outside the converter. Among them, short circuits on the high-voltage side DC bus generate huge instantaneous fault currents. If this fault current cannot be effectively cut off in a very short time, it will directly lead to permanent damage to core power electronic devices such as IGBTs and diodes inside the converter, and may even cause systemic safety accidents. Therefore, it is crucial to implement fast and reliable fault protection for DC-DC converters.

[0003] Current protection measures for DC-DC converters still have many shortcomings and deficiencies that need to be addressed, making it difficult to meet the reliable protection requirements in practical applications. On the one hand, passive protection methods have a significant shortcoming in response speed. Traditional protection methods mostly use fuses or DC circuit breakers. Although fuses are inexpensive, their fusing time is usually on the order of milliseconds, which cannot match the fault current of the freewheeling diode, which reaches its peak value on the order of microseconds. This makes it difficult to achieve effective fault isolation before the power devices are damaged. On the other hand, solid-state DC circuit breakers, which can achieve fault isolation on the order of microseconds, are too expensive, which is not conducive to large-scale application. On the other hand, conventional gate blocking strategies have significant protection blind spots. When a short-circuit fault is detected on the high-voltage side, the conventional strategy of immediately shutting off the gate drive signals of all switching transistors cannot prevent the continuous feeding of subsequent fault current. After the high-voltage side filter capacitor discharges, the low-voltage side power supply will feed current to the fault point through the filter inductor and freewheeling diode. Furthermore, when the voltage of the high-voltage side capacitor drops to 0, the relevant diodes will conduct simultaneously and carry a huge fault current, which will still burn out the power devices. Furthermore, existing technologies lack reliable active isolation mechanisms and have not yet developed a solid-state protection scheme that can actively and quickly isolate the commutator bridge from the fault circuit, especially the discharging DC filter capacitor and the DC power supply, before the power devices reach their limits.

[0004] It is evident that existing DC-DC converter protection measures suffer from slow response speed, incomplete protection, and a lack of reliable active isolation mechanisms, failing to achieve rapid and effective isolation of short-circuit faults to ensure the safety of power devices. Summary of the Invention

[0005] This invention provides a non-isolated solid-state protection device and method for DC-DC converters. This device can solve the problems of slow response speed, incomplete protection and lack of reliable active isolation mechanism in existing DC-DC converter protection measures. It can achieve rapid and effective isolation of short-circuit faults to ensure the safety of power devices.

[0006] To achieve the above objectives, the present invention employs the following technical content: A non-isolated DC-DC converter solid-state protection device includes: The main protection module is connected between the converter bridge and the high-voltage side DC filter capacitor. It is used to disconnect the converter bridge from the high-voltage side DC filter capacitor when a converter failure occurs. The backup protection module is connected in series with the main protection module and is used to disconnect the converter bridge from the DC filter capacitor on the high-voltage side after the main protection module fails. A buffer circuit, connected in parallel with the main protection module and the backup protection module after being connected in series, is used to suppress the overvoltage generated at the moment of turn-off of the main protection module and the converter bridge. The controller is connected to the main protection module, the backup protection module and the converter bridge respectively. It is used to control the main protection module to execute the main protection process, control the conduction state of the low-voltage side switching tube of the converter bridge and control the backup protection module to execute the backup protection process.

[0007] Furthermore, the specific steps of the main protection process are as follows: If a converter failure is confirmed, the low-voltage side switch of the control converter bridge is forcibly turned on so that the gate signal of the low-voltage side switch remains at a high level. Set the gate signal of the main protection module to zero; After a preset shutdown delay time, the main protection module automatically shuts down to disconnect the converter bridge from the high-voltage side DC filter capacitor.

[0008] Furthermore, after the preset shutdown delay time, the main protection module automatically shuts down to disconnect the converter bridge from the high-voltage side DC filter capacitor, and then the following is also included: The low-voltage side switch of the converter bridge is turned off to set the gate signal of the low-voltage side switch to zero, thus protecting all power devices in the converter bridge.

[0009] Furthermore, before the step of forcibly turning on the low-voltage side switch of the converter bridge to keep the gate signal of the low-voltage side switch high if a converter fault is confirmed, the method further includes: The output voltage and output current are monitored to determine whether a short-circuit fault has occurred in the converter.

[0010] Furthermore, the specific steps of the backup protection process are as follows: If the current judgment main protection module is confirmed to be faulty, the low-voltage side switch transistor will be turned off. Based on the freewheeling effect of the filter inductor, the inductor current flows through the backup protection module, and the backup protection module is blown after a preset time to disconnect the connection between the converter bridge and the DC filter capacitor on the high-voltage side.

[0011] Furthermore, after the inductor current flows through the backup protection module based on the freewheeling effect of the filter inductor, and the backup protection module is blown after a preset time to disconnect the connection between the converter bridge and the high-voltage side DC filter capacitor, the method further includes: After the backup protection module blows, the remaining energy of the filter inductor is released through the buffer circuit to suppress overvoltage.

[0012] Furthermore, before controlling the low-voltage side switch to turn off if the current judgment main protection module is confirmed to have failed, the following steps are also included: With the low-voltage side switch of the control converter bridge forcibly turned on to keep the gate signal of the low-voltage side switch high, the main protection module is judged to determine whether it has failed by monitoring the current flowing through the low-voltage side switch. The specific judgment logic is as follows: If the current flowing through the low-voltage side switch has risen and exceeded the maximum current that the low-voltage side switch can withstand before the main protection module is successfully turned off, then the main protection module is judged to have failed; otherwise, the main protection module is judged to be normal.

[0013] A solid-state protection method for a non-isolated DC-DC converter, implemented based on the aforementioned solid-state protection device for a non-isolated DC-DC converter, includes: The controller determines that a fault has occurred in the converter and controls the main protection module to execute the main protection process, disconnecting the converter bridge from the high-voltage side DC filter capacitor through the main protection module. The controller determines that a converter fault has occurred and that the main protection module has failed. It then controls the backup protection module to execute the backup protection procedure and disconnects the converter bridge from the DC filter capacitor on the high-voltage side through the backup protection module. The buffer circuit suppresses the overvoltage generated during the turn-off of the main protection module and the converter bridge.

[0014] Furthermore, the specific steps of the main protection process are as follows: If a converter failure is confirmed, the low-voltage side switch of the control converter bridge is forcibly turned on so that the gate signal of the low-voltage side switch remains at a high level. Set the gate signal of the main protection module to zero; After a preset shutdown delay time, the main protection module automatically shuts down to disconnect the converter bridge from the high-voltage side DC filter capacitor.

[0015] Furthermore, the specific steps of the backup protection process are as follows: If the current judgment main protection module is confirmed to be faulty, the low-voltage side switch transistor will be turned off. Based on the freewheeling effect of the filter inductor, the inductor current flows through the backup protection module, and the backup protection module is blown after a preset time to disconnect the connection between the converter bridge and the DC filter capacitor on the high-voltage side.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a non-isolated solid-state protection device for a DC-DC converter, comprising a main protection module, a backup protection module, a buffer circuit, and a controller. The main protection module is connected between the converter bridge and the high-voltage side DC filter capacitor to quickly disconnect them in case of a fault. The backup protection module is connected in series with the main protection module to provide redundant protection. The buffer circuit is connected in parallel across the series module to suppress turn-off overvoltage. The controller coordinates the main protection process, the backup protection process, and the conduction state control of the low-voltage side switch. The main protection module achieves active and rapid isolation, matching the peak fault current response requirements. The backup module operates to ensure redundancy and reliability when the main protection fails. The buffer circuit absorbs turn-off energy to prevent voltage spikes from damaging devices. Simultaneously, the controller prevents low-voltage power supply from feeding back to the fault point through the inductor and freewheeling diode by turning off the low-voltage side switch, eliminating the blind spots of traditional strategies. Using this device significantly improves fault response speed and protection comprehensiveness, achieves reliable active isolation, blocks high-voltage capacitor discharge and low-voltage power supply feed paths, effectively protects power devices, and optimizes cost.

[0017] This invention also provides a non-isolated DC-DC converter solid-state protection method. Based on the aforementioned non-isolated DC-DC converter solid-state protection device, this method includes the controller prioritizing the main protection module to disconnect the converter bridge from the high-voltage side DC filter capacitor when a converter fault is detected. If the main protection fails, the backup protection module is controlled to perform a disconnection operation, while a buffer circuit suppresses turn-off overvoltage. The main protection module provides microsecond-level fast active isolation, matching the peak fault current requirements of the freewheeling diode, overcoming the shortcomings of slow response of traditional fuses and high cost of solid-state circuit breakers. The controller synchronously turns off the low-voltage side switch, blocking the feed path of low-voltage power supply to the fault point through the inductor and freewheeling diode, eliminating the blind zone of conventional gate blocking strategies, and preventing the diode from conducting and burning out the device when the high-voltage capacitor voltage drops to zero. The buffer circuit absorbs turn-off energy and suppresses voltage spikes, and the backup protection ensures redundant and reliable isolation when the main protection fails. This method can achieve fast response, comprehensive protection, and active and reliable fault isolation, cutting off high-voltage capacitor discharge and low-voltage power supply feed, ensuring the safety of power devices, while also taking cost-effectiveness into account. Attached Figure Description

[0018] Figure 1This is a schematic diagram of a typical bidirectional non-isolated DC-DC converter circuit structure in the prior art provided by the embodiments of the present invention; Figure 2 This is a schematic diagram of the structure of a non-isolated DC-DC converter solid-state protection device provided in an embodiment of the present invention; Figure 3 A flowchart of a solid-state protection method for a non-isolated DC-DC converter provided in an embodiment of the present invention; Figure 4 A schematic diagram of the Boost simulation system for verifying the solid-state protection device on the MATLAB / Simulink platform is provided for embodiments of the present invention. Figure 5 The short-time window fault transient process provided by the embodiments of the present invention under normal main protection conditions; Figure 6 The transient process of long-term fault under normal main protection conditions provided in the embodiments of the present invention; Figure 7 The short-time window fault transient process provided by the embodiments of the present invention in the event of main protection failure; Figure 8 This invention provides a long-term fault transient process in the event of main protection failure, as provided in an embodiment of the invention. Detailed Implementation

[0019] To make the technical problems solved by the present invention, the technical solutions, and the beneficial effects clearer, the following specific embodiments provide a further detailed description of the present invention. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of the invention.

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0021] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0022] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0023] As mentioned in the background section, such as Figure 1 As shown, a typical bidirectional non-isolated DC-DC converter topology mainly consists of a high-voltage side switch S2, a low-voltage side switch S1 and its anti-parallel diodes D1 and D2, and a filter inductor. L f and filter capacitor C 1. C Composed of 2 grades.

[0024] Currently, existing protection measures for DC-DC converters mainly have the following problems: First, passive protection methods have slow response speeds: Traditional protection methods mostly use fuses or DC circuit breakers. Although fuses are inexpensive, their fusing time is typically on the order of milliseconds. For the fault current of the freewheeling diode, which reaches its peak value within microseconds, the response speed is too slow to effectively isolate the fault before the power device fails. Solid-state circuit breakers in DC circuit breakers can achieve fault isolation at the microsecond level, but their cost is extremely high.

[0025] Second, conventional gate interlocking strategies have a protection blind spot: when a high-voltage side short-circuit fault is detected, a conventional protection strategy is to immediately shut down all switching transistors ( S 1 and S 2) Gate drive signal. However, this method has serious drawbacks. For example... Figure 1 As shown, when a short circuit fault occurs on the high-voltage side, even if S 1 and S Both are off, high-voltage side filter capacitor C 2 will first discharge through the fault point. When C 2. The voltage drops below the low-voltage side supply voltage. v in At that time, the low-voltage side power supply v in The filter inductor will pass through L f and freewheeling diode D 2. Continuously feed current to the fault point. And when the voltage of the high-voltage side capacitor drops to 0, D 1. D 2 will simultaneously conduct, and within a short time, a huge fault current sustained by the line freewheeling inductance will flow through it, which will also burn out the diode. D 2. And related power devices. Therefore, simple gate blocking cannot effectively isolate faults.

[0026] Third, there is a lack of reliable active isolation mechanisms: existing technologies lack a solid-state protection scheme that can actively and quickly isolate the commutator bridge from the fault circuit, especially the discharging DC filter capacitor and the DC power supply, before the power devices reach their limits.

[0027] To address the aforementioned issues, this embodiment provides a solid-state protection device for a non-isolated DC-DC converter. This device offers a solid-state protection scheme with fast response, reliable isolation, and effective protection of the internal power devices of the non-isolated DC-DC converter, incorporating both primary and backup mechanisms. The core idea of ​​this device is that upon detecting a short-circuit fault on the high-voltage side, it does not immediately shut down all switching transistors. Instead, it actively controls the low-voltage side switching transistor (S1) to force it to conduct, creating a zero-current turn-off condition for the thyristor (SCR) connected in series in the main circuit. This allows for microsecond-level fault isolation by utilizing the thyristor's fast turn-off characteristics.

[0028] For example, this embodiment provides a non-isolated DC-DC converter solid-state protection device, including a main protection module connected between the converter bridge and the high-voltage side DC filter capacitor. The main protection module is used to disconnect the connection between the converter bridge and the high-voltage side DC filter capacitor when a converter failure occurs. A backup protection module is connected in series with the main protection module. The backup protection module is used to disconnect the converter bridge from the DC filter capacitor on the high-voltage side after the main protection module fails. The main protection module and the backup protection module are connected in series, and then connected in parallel to form a buffer circuit. The buffer circuit is used to suppress the overvoltage generated at the moment of turn-off of the main protection module and the converter bridge. The system also includes controllers connected to the main protection module, the backup protection module, and the converter bridge, respectively. The controllers are used to control the main protection module to execute the main protection process, control the conduction state of the low-voltage side switching transistors of the converter bridge, and control the backup protection module to execute the backup protection process.

[0029] The testing machine provided in this embodiment will be further described in detail below with reference to the accompanying drawings: like Figure 2 As shown, this embodiment provides a non-isolated DC-DC converter solid-state protection device, including the following core modules: Main protection module: in the converter bridge (by...) S 1. S 2. D 1. D 2 components) and high-voltage side DC filter capacitor C A thyristor (SCR) is connected in series between the components as the main isolation element. In this embodiment, the main protection module uses a thyristor.

[0030] Backup protection module: Consists of a fuse connected in series next to the thyristor. In this embodiment, the backup protection module uses a fuse.

[0031] Buffer circuit: consisting of buffer resistors R S and buffer capacitor C S An RC buffer circuit is formed and connected in parallel across the thyristor and the fuse.

[0032] The controller is used to control the main protection module to execute the main protection process, control the conduction status of the low-voltage side switching transistors of the converter bridge, and control the backup protection module to execute the backup protection process.

[0033] For example, this embodiment provides a non-isolated DC-DC converter solid-state protection device, and the functions of each module are as follows: Thyristor (main protection module): As a solid-state switch, it is used to quickly disconnect the commutator bridge and DC filter capacitor in the event of a fault. C The connection enables fault isolation. Thyristors have unidirectional conduction and self-turn-off characteristics, meaning they can turn on and off when their gate signal is set to zero and the current flowing through them is less than their holding current. i H It will automatically shut off when needed.

[0034] Buffer circuit (Rs, Cs): used to suppress the effect of the filter inductor L f Freewheeling in thyristors and S 1. Overvoltage generated during turn-off protects the internal power devices of the converter bridge.

[0035] Fuse (backup protection module): As a final backup protection measure, in case the main protection fails, S 1. After shutting down, utilize S 1. The inductor driven by the conduction is used to achieve fuse breaking, thus realizing physical isolation from the power supply.

[0036] Low-voltage side switching transistor S 1: In addition to its switching function during normal operation of the converter, it is given a new active control function during the protection process, namely, to create zero-current turn-off conditions for the series thyristors by forced conduction.

[0037] Based on the non-isolated DC-DC converter solid-state protection device provided above, this embodiment also provides a non-isolated DC-DC converter solid-state protection method, specifically divided into a main protection process and a backup protection process, wherein: Main protection process: Step 1: Fault Detection: The converter controller monitors parameters such as output voltage and current to determine in real time whether a short-circuit fault has occurred. Once a fault is detected (for example, a sudden increase in current exceeding a threshold), the protection program is immediately activated.

[0038] Step 2, Actively Create Shutdown Conditions: The controller immediately performs two key actions: switching the transistor on the low-voltage side. S 1. Issue a forced conduction signal to keep its gate signal at a high level; set the gate signal of the main protection thyristor connected in series in the main circuit to zero.

[0039] Principle analysis: In the initial stage of a fault, the voltage of the high-voltage side capacitor... v C Still relatively high (greater than the low-voltage side power supply voltage) v in Forced conduction at this time. S 1. It will be a filter inductor. L f current i L This provides a path with extremely low impedance. According to Kirchhoff's Current Law (KCL), current preferentially chooses the lowest impedance path; therefore, the current that would normally flow to the high-voltage side, i.e., through the thyristor, is instead diverted. i D2 It will decrease rapidly and be entirely transferred to the low-voltage side switching transistor. S Branch 1, i.e. i S1 ≈ i L , i D2 ≈ 0. This actively creates a positive turn-off condition for the thyristor where the current flowing through it is less than the holding current.

[0040] Step 3, Thyristor turn-off and isolation: Since the gate signal of the thyristor has been set to zero, and the current flowing through it... i D2 It is close to zero or much smaller than its holding current. i H After a certain shutdown delay time T off After that, the thyristor will automatically and reliably turn off.

[0041] Step 4: Complete Isolation: After the thyristor is turned off, the commutator bridge is successfully connected to the discharging high-voltage capacitor. C And the fault point is isolated. At this time, the controller sends a signal to the switching transistor. S 1. A shutdown signal is issued, setting its gate signal to zero. At this point, the main protection process is complete, and all power devices within the converter bridge are effectively protected.

[0042] Step 5, Overvoltage Suppression: Turn offS After 1, the filter inductor L f The energy stored in it will be passed through S The anti-parallel diode 2 charges the snubber circuit, and the low-voltage side switching transistor... S The voltage spikes at both ends were effectively suppressed. The system successfully achieved fault isolation.

[0043] Backup protection process: Backup protection is designed to address extreme situations where the main protection may fail, such as when a fault develops too quickly or when components malfunction.

[0044] Step 1, Failure Judgment: During Step 2 of the main protection process, the controller will continuously monitor the flow through the switching transistor. S 1 current i S1 .because S 1. After conduction, the inductor current i L It will be on the low-voltage side power supply v in Under the stimulation, it continues to rise. If the current i S1 Before the thyristor successfully turned off, the voltage had already risen and exceeded that of the switching transistor. S 1. The maximum current it can withstand i S1max If so, the main protection is deemed to have failed.

[0045] Step 2: Activate backup protection: Once the main protection is determined to have failed, the controller immediately performs the following actions: sends a shutdown signal to switch S1 (gate signal is set to zero) to protect against... S 1. It is not damaged by overcurrent.

[0046] Step 3: The fuse blows. S 1. After being turned off, due to the filter inductor L f The freewheeling effect exceeds the rated inductor current. i L The current will be forced to flow through the anti-parallel diode of S2 to the backup protection branch, i.e., through the fuse. Since this current is much greater than the rated fusing current of the fuse, the fuse will blow in a short time, thereby achieving physical isolation between the converter bridge and the fault point.

[0047] Step 4, Overvoltage Suppression: After the fuse blows, the inductor... L f The remaining energy will also be released through the buffer circuit to avoid generating destructive overvoltage.

[0048] By combining the main protection and backup protection described above, the protection method provided in this embodiment can provide fast and reliable protection against high-voltage side short-circuit faults in non-isolated DC-DC converters.

[0049] For example, a specific implementation of the above-mentioned solid-state protection device and method for non-isolated DC-DC converters is described below: Example 1, under normal main protection conditions: The non-isolated DC-DC converter solid-state protection device and method provided in this embodiment are used to illustrate the fault isolation process under normal operating conditions of the main protection.

[0050] The protection scheme in this embodiment is applied to a Boost converter system, such as Figure 4 As shown. The system includes a low-voltage side power supply (400V), a high-voltage side load, and a filter inductor. L f Low-voltage side switching transistor S 1. High-voltage side switch tube S 2 (and its anti-parallel diode), high-voltage side filter capacitor C According to the protection scheme of the present invention, a protection circuit consisting of a main protection module (thyristor) and a backup protection module (fuse) is connected in series between the switching transistor S2 and the filter capacitor C, and a buffer circuit is connected in parallel across the two ends of the protection circuit.

[0051] In this embodiment, the specific parameter settings are as follows: high-voltage side voltage level is 750V, low-voltage side power supply voltage is 400V, rated resistive load is 37.5Ω, and the switching transistor... S 1. Maximum withstand current i S1max The thyristor has a forward turn-off delay of 80A. T off The duration is 30ms, and the fuse breaking current is 75A.

[0052] based on Figure 4 The simulation system shown, under normal main protection conditions, produces the following simulation results: Figure 5 , Figure 6 As shown. The simulation results, from top to bottom, are the filter inductor currents. i L Current of switch S1 i S1 (Collector to emitter current), current in switch S2 i S2 thyristor current i SCR Buffer circuit current i snu Voltage of switching transistor S1 v S1(Collector-emitter voltage), voltage across switch S2 v S2 Buffer the voltage of this circuit v snu , gate signal of switching transistor S1 G 1. Thyristor gate signal G SCR .

[0053] Under normal operating conditions of the main protection system, the thyristor will turn off forward shortly after S1 is turned on. Figure 5 , Figure 6 It can be seen that the fault occurs at 0.3 seconds of simulation time. After a fault detection delay of about ten microseconds, the controller will immediately send a turn-off signal to the thyristor and set the gate signal. G SCR Low level, while maintaining the gate signal of switch S1 G 1. High level, at this time the current of switch S1 is... i S1 The current gradually increases under the excitation of the low-voltage side DC power supply. At this time, the current flowing through S2... i S2 This refers to the current flowing through the thyristor. When this current is less than the holding current... i H And continued T off If the time is specified, the thyristor will be turned off in the forward direction, which is approximately 0.300041s in the simulation, or 41 ms after the fault occurs.

[0054] After the thyristor is turned off, the controller sends a turn-off signal to the switching transistor S1, and the gate signal of S1... G 1. Set to low level. At this time, the inductor current... i L The voltage surge flows into the snubber circuit through the reverse parallel diode of switch S2, immediately causing a voltage spike across switch S1. However, this spike is effectively suppressed by the snubber circuit. Subsequently, as the fault process progresses, at a simulation time of 0.300875s... i L A current flows into the snubber circuit through the anti-parallel diode connected to the switching transistor S2 to establish the reverse voltage of the snubber circuit. After this process is completed, the commutation bridge and the DC filter capacitor are isolated.

[0055] Example 2, under the condition of main protection failure: The non-isolated DC-DC converter solid-state protection device and method provided in this embodiment are used to illustrate how backup protection is activated and completes fault isolation in the event of main protection failure. The system structure and parameter settings are the same as in Embodiment 1.

[0056] To demonstrate the backup protection process, this embodiment simulates a scenario where the main protection fails. Specifically, after the fault occurs, although the controller executes the command to forcibly turn on S1, the gate signal of the thyristor is maintained. G SCR It is at a high level (or assumes the thyristor is damaged and cannot be turned off).

[0057] based on Figure 4 The simulation results for the system shown are as follows, assuming the main protection fails: Figure 7 , Figure 8 As shown. The simulation results, from top to bottom, are the filter inductor currents. i L Current of switch S1 i S1 (Collector to emitter current), current in switch S2 i S2 thyristor current i SCR Buffer circuit current i snu Voltage of switching transistor S1 v S1 (Collector-emitter voltage), voltage across switch S2 v S2 Buffer the voltage of this circuit v snu , gate signal of switching transistor S1 G 1. Thyristor gate signal G SCR .

[0058] When the current flowing through the switching transistor S1 i S1 Greater than or equal to its maximum withstand current i S1max When this occurs, the main protection is deemed to have failed, and backup protection operation begins. (Combined with...) Figure 7 and Figure 8 The fault occurred at 0.3 seconds of simulation time, and approximately 220 microseconds later... i S1 Greater than or equal to its maximum withstand current i S1max At this time, the controller sends a turn-off signal to switch S1, while maintaining the gate signal of switch S1. G 1. Low level, and sends a turn-on signal to the bypass thyristor, setting the gate signal. G BSCR High level. Inductor current. i L The path flows from the reverse parallel diode of switch S1 to switch S2, and then through the fuse. This is due to the current in the filter inductor. i LIf the current exceeds the fuse's breaking current, the fuse will blow within a short time to isolate the commutator bridge from the DC filter capacitor. After the fuse blows, the filter inductor current... i L The voltage surges through the reverse parallel diode of switch S2 into the buffer circuit, causing an immediate voltage spike across switch S1. However, this spike is effectively suppressed by the buffer circuit.

[0059] Subsequently, as the fault process progressed, at a simulation time of 0.301112s, i L A current flows into the buffer circuit through the anti-parallel diode connected to the switching transistor S2 to establish the reverse voltage of the buffer circuit.

[0060] In summary, this invention provides a non-isolated solid-state protection device and method for DC-DC converters, which has the following advantages compared to existing protection measures: First, it has an extremely fast response speed and good protection effect: This invention uses all-solid-state devices (thyristors, IGBTs) to perform protection actions, with a response speed in the microsecond range, which is much faster than the millisecond range of fuses and mechanical circuit breakers. It can complete isolation before semiconductor power devices are damaged by huge fault currents, and the protection effect is significant.

[0061] Secondly, it solves the protection blind zone problem of the freewheeling diode: This invention creates a zero-current turn-off condition for the series thyristor by actively controlling the switching transistor S1, which cleverly solves the fundamental problem in the prior art that "after simply blocking the switching transistor, the power supply will still feed a large current to the fault point through the freewheeling diode".

[0062] Third, active isolation ensures high reliability: Unlike passively waiting for the current to cross zero or relying on a fuse to blow, this invention is a protection method that actively creates isolation conditions. Through intelligent control, the isolation element (thyristor) is forcibly turned off, making the isolation action more certain and reliable.

[0063] Fourth, the protection scheme is comprehensive and the security is strong: This invention designs a dual insurance mechanism of "main protection + backup protection". The main protection is fast and proactive, while the backup protection ensures that core components and system safety can still be protected by fuse blowing in extreme cases. The overall scheme is comprehensive and greatly improves the robustness and security of the converter.

[0064] Fifth, it is highly feasible and cost-effective: This invention adds a limited number of solid-state devices and corresponding control logic to the existing converter topology. The modification cost is relatively low, but the resulting improvement in safety and reliability is huge, which has high cost-effectiveness and engineering application value.

[0065] The above embodiments are merely one of the implementation methods for achieving the technical solution of the present invention. The scope of protection claimed by the present invention is not limited to this embodiment, but also includes any variations, substitutions and other implementation methods that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention.

Claims

1. A non-isolated solid-state protection device for a DC-DC converter, characterized in that, include: The main protection module is connected between the converter bridge and the high-voltage side DC filter capacitor. It is used to disconnect the converter bridge from the high-voltage side DC filter capacitor when a converter failure occurs. The backup protection module is connected in series with the main protection module and is used to disconnect the converter bridge from the DC filter capacitor on the high-voltage side after the main protection module fails. A buffer circuit, connected in parallel with the main protection module and the backup protection module after being connected in series, is used to suppress the overvoltage generated at the moment of turn-off of the main protection module and the converter bridge. The controller is connected to the main protection module, the backup protection module and the converter bridge respectively. It is used to control the main protection module to execute the main protection process, control the conduction state of the low-voltage side switching tube of the converter bridge and control the backup protection module to execute the backup protection process.

2. The non-isolated DC-DC converter solid-state protection device according to claim 1, characterized in that, The specific steps of the main protection process are as follows: If a converter failure is confirmed, the low-voltage side switch of the control converter bridge is forcibly turned on so that the gate signal of the low-voltage side switch remains at a high level. Set the gate signal of the main protection module to zero; After a preset shutdown delay time, the main protection module automatically shuts down to disconnect the converter bridge from the high-voltage side DC filter capacitor.

3. A non-isolated DC-DC converter solid-state protection device according to claim 2, characterized in that, After a preset shutdown delay time, the main protection module automatically shuts down to disconnect the converter bridge from the high-voltage side DC filter capacitor. This process also includes: The low-voltage side switch of the converter bridge is turned off to set the gate signal of the low-voltage side switch to zero, thus protecting all power devices in the converter bridge.

4. A non-isolated DC-DC converter solid-state protection device according to claim 2, characterized in that, Before the step of forcibly turning on the low-voltage side switch of the converter bridge to keep the gate signal of the low-voltage side switch high, if a converter fault is confirmed, the method further includes: The output voltage and output current are monitored to determine whether a short-circuit fault has occurred in the converter.

5. A non-isolated DC-DC converter solid-state protection device according to claim 2, characterized in that, The specific steps of the backup protection process are as follows: If the current judgment main protection module is confirmed to be faulty, the low-voltage side switch transistor will be turned off. Based on the freewheeling effect of the filter inductor, the inductor current flows through the backup protection module, and the backup protection module is blown after a preset time to disconnect the connection between the converter bridge and the DC filter capacitor on the high-voltage side.

6. A non-isolated DC-DC converter solid-state protection device according to claim 5, characterized in that, The method, based on the freewheeling effect of the filter inductor, involves the inductor current flowing through the backup protection module. After a preset time, the backup protection module is blown to disconnect the connection between the converter bridge and the high-voltage side DC filter capacitor. The method further includes: After the backup protection module blows, the remaining energy of the filter inductor is released through the buffer circuit to suppress overvoltage.

7. A non-isolated DC-DC converter solid-state protection device according to claim 5, characterized in that, Before controlling the low-voltage side switch to turn off the circuit breaker if the current judgment main protection module is confirmed to have failed, the following steps are also included: With the low-voltage side switch of the control converter bridge forcibly turned on to keep the gate signal of the low-voltage side switch high, the main protection module is judged to determine whether it has failed by monitoring the current flowing through the low-voltage side switch. The specific judgment logic is as follows: If the current flowing through the low-voltage side switch has risen and exceeded the maximum current that the low-voltage side switch can withstand before the main protection module is successfully turned off, then the main protection module is judged to have failed; otherwise, the main protection module is judged to be normal.

8. A solid-state protection method for a non-isolated DC-DC converter, implemented based on the solid-state protection device for a non-isolated DC-DC converter as described in any one of claims 1-7, characterized in that, include: The controller determines that a fault has occurred in the converter and controls the main protection module to execute the main protection process, disconnecting the converter bridge from the high-voltage side DC filter capacitor through the main protection module. The controller determines that a converter fault has occurred and that the main protection module has failed. It then controls the backup protection module to execute the backup protection procedure and disconnects the converter bridge from the DC filter capacitor on the high-voltage side through the backup protection module. The buffer circuit suppresses the overvoltage generated during the turn-off of the main protection module and the converter bridge.

9. A solid-state protection method for a non-isolated DC-DC converter according to claim 8, characterized in that, The specific steps of the main protection process are as follows: If a converter failure is confirmed, the low-voltage side switch of the control converter bridge is forcibly turned on so that the gate signal of the low-voltage side switch remains at a high level. Set the gate signal of the main protection module to zero; After a preset shutdown delay time, the main protection module automatically shuts down to disconnect the converter bridge from the high-voltage side DC filter capacitor.

10. A solid-state protection method for a non-isolated DC-DC converter according to claim 8, characterized in that, The specific steps of the backup protection process are as follows: If the current judgment main protection module is confirmed to be faulty, the low-voltage side switch transistor will be turned off. Based on the freewheeling effect of the filter inductor, the inductor current flows through the backup protection module, and the backup protection module is blown after a preset time to disconnect the connection between the converter bridge and the DC filter capacitor on the high-voltage side.

Images