Solid state circuit breaker bidirectional multi-stage reset protection circuit based on multi-diode modulation

Abstract

The application belongs to the field of new energy vehicle electronic control, and particularly relates to a solid-state circuit breaker bidirectional multistage desaturation protection circuit based on multiple diode modulation, which comprises multiple parallelly connected and identically structured grading detection branches, at least a first grading detection branch and a second grading detection branch; the bidirectional multistage desaturation protection circuit realizes grading of protection delay time under different fault currents. For an overcurrent fault with a fast rising speed of fault current, a higher fault detection threshold current and a very short protection delay time are set, so that the fault can be quickly identified and the solid-state circuit breaker can quickly cut off the fault current. For an overload fault with a longer duration but a smaller fault current, multiple lower fault detection threshold currents and longer protection delay times can be set according to the overload bearing capacity of the specific solid-state circuit breaker and the protected load, so as to improve the ability of the solid-state circuit breaker to pass through the overload current under the premise of ensuring safe operation of the solid-state circuit breaker.

Description

Technical Field

[0001] This invention belongs to the field of electronic control for new energy vehicles, specifically relating to a bidirectional multi-stage desaturation protection circuit for a solid-state circuit breaker based on multi-diode modulation. Background Technology

[0002] In modern military equipment, armored vehicles serve as crucial combat platforms, and their combat performance and reliability directly impact the success or failure of a war. With technological advancements and the increasing complexity of battlefield environments, the demands on the electrical systems of armored vehicles are constantly rising. They are typically equipped with high-power electrical equipment and sophisticated electronic systems, requiring robust power distribution protection mechanisms to ensure their stable operation.

[0003] Solid-state circuit breakers (SSDs) offer advantages such as fast switching speed and long switching life, playing a crucial role in ensuring the safety of armored vehicle power distribution systems. Overcurrent detection technology, a key technology for SSDs, is required to quickly and accurately identify overcurrent faults in the power distribution system and promptly control the SSD to trip, preventing system overcurrent failure. This not only ensures the safe operation of the SSDs but also provides crucial support for the stability of the entire power distribution system and the combat capability of the armored vehicles.

[0004] Commonly used overcurrent detection techniques include four methods: sampling resistor detection, current sensor detection, current mirror detection, and desaturation detection. The sampling resistor method requires a sampling resistor to be connected in series with the power distribution system, increasing system losses and making it unsuitable for high-power power distribution systems. The current mirror method is a further extension of the sampling resistor method, where an auxiliary power device is connected in parallel inside the chip being tested. After the solid-state circuit breaker is turned on, a portion of the current flows through this auxiliary device at a certain ratio (e.g., 1 / 1000). The required current information can be obtained by measuring the on-state voltage of the sampling resistor connected in series with this auxiliary device. This method avoids the additional losses associated with the traditional sampling resistor method, but its reliance on special manufacturing processes for power devices leads to higher costs and greater implementation difficulty. The current sensor method requires the use of current sensors such as Hall effect sensors and giant magnetoresistive sensors to collect system current and process it through processing circuits for fault detection and protection. This method is both bulky and costly, and similarly unsuitable for collecting large currents.

[0005] Traditional desaturation detection technology originated from overcurrent detection in IGBTs of power converters and has gradually been extended to other power devices (such as SiC MOSFETs). This technology reflects the on-state current of a power device by detecting its on-state voltage. When the on-state voltage exceeds a certain set threshold, it indicates an overcurrent fault, and the power device is then turned off via gate drive to ensure the system is not damaged by the overcurrent fault. Since solid-state circuit breakers use power semiconductor devices as the main switches, overcurrent fault detection in solid-state circuit breakers can also be achieved using this technology.Figure 1 This describes the application principle of traditional desaturation detection technology in solid-state circuit breakers. The core switch of this solid-state circuit breaker is a single IGBT, therefore it can only interrupt unidirectional current, and the desaturation detection circuit can only detect unidirectional fault current.

[0006] In battery power distribution and DC microgrid systems, solid-state circuit breakers (SSDs) are typically required to enable bidirectional current flow and interruption; these are generally referred to as bidirectional SSDs. Taking IGBT-based SSDs as an example, to achieve this, the main switch often employs an IGBT series-connected configuration. Simultaneously, the associated overcurrent detection technology also needs to enable bidirectional overcurrent fault detection. Furthermore, in power distribution systems, different overcurrent protection delay times need to be configured for fault currents of varying amplitudes to prevent false protection triggered by normal instantaneous overloads and improve system reliability.

[0007] To achieve bidirectional, multi-threshold, and time-delay overcurrent fault detection, this invention proposes a bidirectional multi-stage desaturation detection technology for bidirectional solid-state circuit breakers. This technology, by sharing key components such as comparators and high-voltage diodes, effectively reduces the size and cost of the detection system while meeting the aforementioned overcurrent detection requirements. Summary of the Invention

[0008] (a) Technical problems to be solved The technical problem to be solved by this invention is: how to provide a bidirectional multi-level desaturation protection circuit and its protection method to overcome the defects of traditional desaturation detection such as unidirectional, single-level and inflexible protection strategy, so as to achieve: (1) overcurrent detection and fault disconnection of current in both positive and negative directions; (2) multi-level overcurrent levels correspond to different protection delays, improving the system's anti-interference and adaptability; (3) reducing system hardware cost and volume, improving integration, and adapting to the needs of various protection strategies in complex environments.

[0009] (II) Technical Solution To solve the above technical problems, the present invention provides a bidirectional multi-stage desaturation protection circuit for a solid-state circuit breaker based on multi-diode modulation. The front end of the bidirectional multi-stage desaturation protection circuit is connected to the bidirectional solid-state circuit breaker body. The bidirectional solid-state circuit breaker body includes a gate driver, a first solid-state circuit breaker IGBT1, and a second solid-state circuit breaker IGBT2, which are used to send an enable signal and an on-state voltage characterizing the original fault information to the bidirectional multi-stage desaturation protection circuit. The bidirectional multi-level desaturation protection circuit includes two symmetrically parallel on-state voltage detection circuits, namely a first on-state voltage detection circuit and a second on-state voltage detection circuit. The first on-state voltage detection circuit includes a first high-voltage blocking diode. D s1 First current-limiting resistorR s1 A constant current source and a second on-state voltage detection circuit including a second high-voltage blocking diode. D s2 Second current-limiting resistor R s2 With a constant current source, this structure is used to detect the on-state voltage of power devices connected in reverse series and to prevent high voltage damage to the bidirectional multi-stage desaturation protection circuit; The bidirectional multi-level desaturation protection circuit further includes: multiple parallel-connected and structurally identical graded detection branches, including at least a first graded detection branch and a second graded detection branch; The first graded detection branch includes a first parameter adjustment circuit and a second parameter adjustment circuit; The first parameter adjustment circuit includes: a first adjustable resistor. R th1 First blanking capacitor C blk1 First input low-voltage blocking diode D blo1_1 First output low-voltage blocking diode D blo1 The second parameter adjustment circuit includes: a second adjustable resistor. R th2 Second blanking capacitor C blk2 Second input low-voltage blocking diode D blo2_1 Second output low-voltage blocking diode D blo2 ; The second graded detection branch includes a third parameter adjustment circuit and a fourth parameter adjustment circuit; The third parameter adjustment circuit includes: a third adjustable resistor. R th3 Third blanking capacitor C blk3 Third input low-voltage blocking diode D blo3_1 Third output low-voltage blocking diode D blo3 The fourth parameter adjustment circuit includes: a fourth adjustable resistor. R th4 Fourth blanking capacitor C blk4 Fourth input low-voltage blocking diode D blo4_1 Fourth output low-voltage blocking diode D blo4 ; Wherein, the first adjustable resistor Rth1 Second adjustable resistor R th2 Used to adjust the branch detection threshold of the first-level detection branch; third adjustable resistor R th3 and the fourth adjustable resistor R th4 Used to adjust the branch detection threshold of the second-level detection branch; First blanking capacitor C blk1 Second blanking capacitor C blk2 The third blanking capacitor is used to adjust the delay time of the first stage detection branch, i.e., the blanking time. C blk3 and the fourth blanking capacitor C blk4 Used to adjust the delay time of the second-level detection branch, i.e., the blanking time; First output low-voltage blocking diode D blo1 The second output low-voltage blocking diode is placed on the line output of the first parameter adjustment circuit. D blo2 The third output low-voltage blocking diode is placed on the line output of the second parameter adjustment circuit. D blo3 The fourth output low-voltage blocking diode is placed on the line output of the third parameter adjustment circuit. D blo4 It is placed on the line output of the fourth parameter adjustment circuit to avoid mutual interference between on-state voltage detection circuits, thereby realizing the shared back-end fault judgment circuit and the setting of multi-level desaturation detection parameters; The fault detection circuit includes a clamping diode. D blk The above symmetrical parallel design uses a shared fault determination circuit structure, which can ensure the consistency of overcurrent detection in both directions and reduce the difficulty of circuit debugging while reducing the hardware size and cost of the protection circuit. First input low-voltage blocking diode D blo1_1 The second input low-voltage blocking diode is placed on the line input of the first parameter adjustment circuit. D blo2_1 The third input low-voltage blocking diode is placed on the line input of the second parameter adjustment circuit. D blo3_1 The fourth input low-voltage blocking diode is placed on the line input of the third parameter adjustment circuit. D blo4_1It is placed on the line input of the fourth parameter adjustment circuit to avoid mutual interference between on-state voltage detection circuits, thereby enabling multiple graded detection branches, including the first graded detection branch and the second graded detection branch, to share the first on-state voltage detection circuit and the second on-state voltage detection circuit.

[0010] (III) Beneficial Effects Compared with the prior art, the present invention has the following beneficial effects: This invention is based on Figure 2 The schematic diagram shown shows the construction of Figure 3 The hardware circuit for bidirectional multi-stage desaturation protection is shown on the right. This hardware circuit is designed with three levels of fault current detection, corresponding to... Figure 2 The circuit consists of three graded detection branches. Therefore, this hardware circuit can be configured with three different overcurrent detection thresholds and their corresponding protection action delay times. To verify the effectiveness of this circuit, according to... Figure 3 The schematic diagram shown on the left illustrates fault detection experiments under different fault currents. Figure 3 The high-voltage DC power supply shown in the schematic diagram on the left. V DC ,switch S and energy storage capacitors C The bus power supply section for simulating a DC system; the bidirectional solid-state circuit breaker body consists of IGBT1 and IGBT2 (model IGW15N120H3) connected in reverse series, the gate drive system, and a bidirectional multi-stage desaturation protection circuit; line inductance. L 1 and load R L The transmission lines and loads of a DC system were simulated; fault switches were also included. S f and fault resistor R f Used to simulate overcurrent faults in DC systems, where S f Controlling the occurrence of faults, R f Used to control the magnitude of fault current.

[0011] Table 1 Key parameters of the hardware test circuit parameter numerical values Bus voltage / V 100 Busbar energy storage capacity / μF 200 Line inductance / μH 10 Load resistance / Ω 50 IGBT rated current / A 15 Adjustable resistors Rth1 and Rth2 / kΩ 2.9 Adjustable resistors Rth3 and Rth4 / kΩ 6 Adjustable resistors Rth5 and Rth6 / kΩ 17.5 Comparator operating threshold voltage Vth / V 4.3 Blanking capacitors Cblk1 and Cblk2 / pF 100 When the detection circuit is activated, the voltage / V of Cblk1 or Cblk2 4.8 Blanking capacitors Cblk3 and Cblk4 / nF 100 When detection circuit two operates, the voltage / V of Cblk3 or Cblk4 3.7 Blanking capacitors Cblk5 and Cblk6 / nF 22 When the detection circuit operates in three stages, the voltage / V of Cblk5 or Cblk6 is measured. 3 The key parameters of the test circuit and fault detection circuit are shown in Table 1. To ensure experimental safety, Figure 3 The left-hand diagram uses a high-voltage power supply first. V DC Energy storage capacitor C Charge to bus voltage, then pass through switch S A solution is to disconnect the power supply and use an energy storage capacitor as the power supply for the overcurrent fault simulation system.

[0012] Experimental results To verify the effectiveness of the bidirectional multi-stage desaturation protection circuit, the fault resistor was adjusted. R f Three overcurrent fault detection experiments were conducted under different fault currents, and the magnitude of the overload current and the fault protection action delay time were measured respectively. Figure 4 and Figure 5 The results are from the first overcurrent fault detection experiment. Before the experiment, the fault resistance was set to 1 Ω, so the fault current rose rapidly, thus simulating a relatively extreme overcurrent fault in the system. Figure 4 The system bus current was measured during the fault. i L On-state voltage of IGBT1 v CE1 The forward blanking capacitor of detection circuit one C blk1 voltage v Cblk1 The input voltage at the negative terminal of the comparator v com Waveform. In Figure 4 In t An overcurrent fault was triggered at time 1, and the fault current was... i L The forward voltage of the IGBT1 increases rapidly over time. v CE1 It also rises accordingly. Therefore, the blanking capacitor voltage increases through... Figure 2 Branch ② in the circuit begins charging, and the voltage across its terminals is... v Cblk1 It started to rise. v com And it rose accordingly. t At time 2, v Cblk1 The voltage rises to 4.8 V, while the input voltage at the negative terminal of the comparator... v com The comparator's operating threshold voltage of 4.3 V was reached, thus triggering the overcurrent protection. After a propagation delay of approximately 1.5 μs, the solid-state circuit breaker began to turn off, and the current... i L It gradually decreased to zero.

[0013] Figure 5 Simultaneously, the blanking capacitor voltages in detection circuits one, two, and three were measured during the overcurrent fault process. v Cblk1 , v Cblk3 and v Cblk5This shows that although all three voltages show an upward trend, the increase is due to the blanking capacitor. C blk3 and C blk5 The capacitance values ​​are relatively large (as shown in Table 1), so the rise rate of the two voltages is relatively slow. Therefore, in t At time 2, only v Cblk1 When the detection circuit is activated, as shown in Table 1, C blk1 or C blk2 The voltage / V”4.8 V, which in turn caused the detection circuit to activate. In summary, under the condition of low fault impedance and rapid rise of fault current, only the detection circuit with a small blanking capacitor value triggered the overcurrent protection.

[0014] Figure 6 and Figure 7 This presents the results of the second overcurrent fault detection experiment. This overcurrent experiment simulated the operation of the detection circuit under a relatively small and constant overload current. Similarly... Figure 6 The system bus current was measured during the fault. i L On-state voltage of IGBT1 v CE1 The forward blanking capacitor of detection circuit two C blk3 voltage v Cblk3 The input voltage at the negative terminal of the comparator v com This shows that in the fault current i L With a constant current of 42 A, the forward voltage of the forward-conducting IGBT1 is... v CE1 It also remained relatively constant at 3.2 V. However, as the failure time increased, v Cblk3 and v com It continues to rise. At approximately 500 μs (this time is determined by the blanking capacitor) C blk3 After the protection action is delayed (determined by the capacitance value), v Cblk3 When the voltage rises to 3.7 V, the input voltage at the negative terminal of the comparator is... v com The comparator's operating threshold voltage of 4.3 V was reached, thus triggering the overcurrent protection.

[0015] Similarly, Figure 7 Simultaneously, the blanking capacitor voltages in detection circuits one, two, and three were measured during the overcurrent fault process.v Cblk1 , v Cblk3 and v Cblk5 This shows that although the voltages of all three capacitors are increasing, the increase is due to the blanking capacitor. C blk5 The capacitance value is greater than C blk3 (As shown in Table 1), therefore C blk3 The voltage rises relatively quickly. When v Cblk3 When the detection circuit 2 operates as shown in Table 1, C blk3 or C blk4 When the voltage reached 3.7 V, detection circuit two triggered the overcurrent fault protection. Furthermore, although in the initial stage of the fault... v Cblk1 The rate of increase is faster than v Cblk3 However, due to the small fault current, v CE1 It is also smaller, which in turn makes v Cblk1 The voltage eventually stabilized at 3.9 V, failing to reach the trigger voltage of 4.8 V for detection circuit one. In summary, under the aforementioned relatively small and constant overload current conditions, only detection circuit two triggered the overcurrent protection.

[0016] Figure 8 and Figure 9 This is the result of the third overcurrent fault detection experiment. The difference between this experiment and Experiment 2 is that it uses a constant overload current. i L It was further reduced to 32 A. Similarly, from Figure 8 It can be seen that after a delay of 1.6 ms, the blanking capacitor voltage in detection circuit three... v Cblk5 The input voltage at the negative terminal of the comparator rises to 3V. v com The comparator's operating threshold voltage of 4.3 V was reached, thus triggering the overcurrent protection. Similarly, Figure 9 Simultaneously, the blanking capacitor voltages in detection circuits one, two, and three were measured during the overcurrent fault process. v Cblk1 , v Cblk3 and v Cblk5 This shows that, although C blk1 and C blk3All less than C blk5 (It has a faster voltage rise rate), but due to the smaller overload fault current, it results in... v Cblk1 and v Cblk3 The voltage remained at 3.4 V and 3.3 V respectively, failing to trigger the protection. Therefore, only the third detection circuit triggered the overcurrent protection.

[0017] The waveform analysis of Experiments 1, 2, and 3 shows that the proposed bidirectional multi-level desaturation protection circuit achieves graded protection delay times under different fault currents. For overcurrent faults with a rapid rise in fault current, a higher fault detection threshold current and an extremely short protection delay time are set, enabling rapid fault identification and quick disconnection of the fault current by the solid-state circuit breaker. Meanwhile, for overload faults with a longer duration but smaller fault current, multiple lower fault detection threshold currents and longer protection delay times can be set according to the overload capacity of the specific solid-state circuit breaker and the protected load, thereby improving the solid-state circuit breaker's ability to withstand overload currents while ensuring its safe operation. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the traditional unidirectional desaturation detection principle.

[0019] Figure 2 This is a schematic diagram of the bidirectional multi-level desaturation detection principle.

[0020] Figure 3 The left side shows the test schematic of the bidirectional multi-level desaturation protection circuit, and the right side shows the hardware circuit diagram of the bidirectional multi-level desaturation protection circuit.

[0021] Figure 4 This is a waveform diagram of the overcurrent detection circuit when a rapid overcurrent fault occurs.

[0022] Figure 5 This is a schematic diagram of the blanking capacitor voltage waveforms in detection circuits one, two, and three when a rapid overcurrent fault occurs.

[0023] Figure 6 The waveform diagram of the overcurrent detection circuit under the condition of constant overload current (42 A).

[0024] Figure 7 This is a schematic diagram of the blanking capacitor voltage waveforms in detection circuits one, two, and three under the condition of constant overload current (42 A).

[0025] Figure 8 The waveform diagram of the overcurrent detection circuit under the condition of constant overload current (32 A).

[0026] Figure 9 This is a schematic diagram of the blanking capacitor voltage waveforms in detection circuits one, two, and three under the condition of constant overload current (32 A). Detailed Implementation

[0027] To make the objectives, contents, and advantages of the present invention clearer, the specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples.

[0028] To address the problems of existing technologies, this invention provides a bidirectional multi-stage desaturation protection circuit for a solid-state circuit breaker based on multi-diode modulation. The front end of the bidirectional multi-stage desaturation protection circuit is connected to the bidirectional solid-state circuit breaker body. The bidirectional solid-state circuit breaker body includes a gate driver, a first solid-state circuit breaker IGBT1, and a second solid-state circuit breaker IGBT2, which are used to send an enable signal and an on-state voltage characterizing the original fault information to the bidirectional multi-stage desaturation protection circuit. like Figure 2 As shown, the bidirectional multi-level desaturation protection circuit includes two symmetrically parallel on-state voltage detection circuits, namely a first on-state voltage detection circuit and a second on-state voltage detection circuit. The first on-state voltage detection circuit includes a first high-voltage blocking diode. D s1 First current-limiting resistor R s1 A constant current source and a second on-state voltage detection circuit including a second high-voltage blocking diode. D s2 Second current-limiting resistor R s2 With a constant current source, this structure is used to detect the on-state voltage of power devices connected in reverse series and to prevent high voltage damage to the bidirectional multi-stage desaturation protection circuit; The bidirectional multi-level desaturation protection circuit further includes: multiple parallel-connected and structurally identical graded detection branches, including at least a first graded detection branch and a second graded detection branch; The first graded detection branch includes a first parameter adjustment circuit and a second parameter adjustment circuit; The first parameter adjustment circuit includes: a first adjustable resistor. R th1 First blanking capacitor C blk1 First input low-voltage blocking diode D blo1_1 First output low-voltage blocking diode D blo1 The second parameter adjustment circuit includes: a second adjustable resistor. R th2 Second blanking capacitor C blk2 Second input low-voltage blocking diodeD blo2_1 Second output low-voltage blocking diode D blo2 ; The second graded detection branch includes a third parameter adjustment circuit and a fourth parameter adjustment circuit; The third parameter adjustment circuit includes: a third adjustable resistor. R th3 Third blanking capacitor C blk3 Third input low-voltage blocking diode D blo3_1 Third output low-voltage blocking diode D blo3 The fourth parameter adjustment circuit includes: a fourth adjustable resistor. R th4 Fourth blanking capacitor C blk4 Fourth input low-voltage blocking diode D blo4_1 Fourth output low-voltage blocking diode D blo4 ; Wherein, the first adjustable resistor R th1 Second adjustable resistor R th2 Used to adjust the branch detection threshold of the first-level detection branch; third adjustable resistor R th3 and the fourth adjustable resistor R th4 Used to adjust the branch detection threshold of the second-level detection branch; First blanking capacitor C blk1 Second blanking capacitor C blk2 The third blanking capacitor is used to adjust the delay time of the first stage detection branch, i.e., the blanking time. C blk3 and the fourth blanking capacitor C blk4 Used to adjust the delay time of the second-level detection branch, i.e., the blanking time; First output low-voltage blocking diode D blo1 The second output low-voltage blocking diode is placed on the line output of the first parameter adjustment circuit. D blo2 The third output low-voltage blocking diode is placed on the line output of the second parameter adjustment circuit. D blo3The fourth output low-voltage blocking diode is placed on the line output of the third parameter adjustment circuit. D blo4 It is placed on the line output of the fourth parameter adjustment circuit to avoid mutual interference between on-state voltage detection circuits, thereby realizing the shared back-end fault judgment circuit and the setting of multi-level desaturation detection parameters; The fault detection circuit includes a clamping diode. D blk The above symmetrical parallel design uses a shared fault determination circuit structure, which can ensure the consistency of overcurrent detection in both directions and reduce the difficulty of circuit debugging while reducing the hardware size and cost of the protection circuit. First input low-voltage blocking diode D blo1_1 The second input low-voltage blocking diode is placed on the line input of the first parameter adjustment circuit. D blo2_1 The third input low-voltage blocking diode is placed on the line input of the second parameter adjustment circuit. D blo3_1 The fourth input low-voltage blocking diode is placed on the line input of the third parameter adjustment circuit. D blo4_1 It is placed on the line input of the fourth parameter adjustment circuit to avoid mutual interference between on-state voltage detection circuits, thereby enabling multiple graded detection branches, including the first graded detection branch and the second graded detection branch, to share the first on-state voltage detection circuit and the second on-state voltage detection circuit.

[0029] The working principle of the bidirectional multi-level desaturation protection circuit for bidirectional desaturation detection is as follows: When the output voltage of the gate drive is positive, the first solid-state circuit breaker IGBT1 and the second solid-state circuit breaker IGBT2 will be turned on simultaneously. At this time, the bus voltage forms a path through the first solid-state circuit breaker IGBT1, the second solid-state circuit breaker IGBT2 and the load, and the power distribution system starts to work normally. Then, in the first stage detection branch, the output voltage of the gate drive V GS Send an enable signal to cause the constant current source to output a constant current. I s1 , I s2 constant current I s1 Potential distribution channels include: Figure 2 Branch ① and branch ② in the circuit; constant current I s2 Potential distribution channels include: Figure 2 Branch road ⑤ and branch road ⑥ in the middle; The branch circuit ① includes: a constant current source and a first adjustable resistor.R th1 First input low-voltage blocking diode D blo1_1 First current-limiting resistor R s1 First high-voltage blocking diode D s1 First solid-state circuit breaker IGBT1; The branch ② includes: a constant current source and a first adjustable resistor. R th1 First blanking capacitor C blk1 ; The branch circuit ⑤ includes: a constant current source and a second adjustable resistor. R th2 Second input low-voltage blocking diode D blo2_1 Second current-limiting resistor R s2 Second high-voltage blocking diode D s2 The second solid-state circuit breaker, IGBT2; The branch circuit ⑥ includes: a constant current source and a second adjustable resistor. R th2 Second blanking capacitor C blk2 ; Through branch ② or branch ⑥, the constant current source will supply power to the first blanking capacitor. C blk1 Or the second blanking capacitor C blk2 During charging, the voltages of the two blanking capacitors are respectively: (1) (2) in, V Ds1 , V Ds2 These are the first high-voltage blocking diodes. D s1 Second high-voltage blocking diode D s2 The on-state pressure drop is a constant. V Rs1 , V Rs2 The first current-limiting resistor is respectively R s1 Second current-limiting resistor R s2 The voltage across the two ends is a constant. V CE1 , VCE2 These are the on-state voltages of the first solid-state circuit breaker IGBT1 and the second solid-state circuit breaker IGBT2, respectively. V Dblo1_1 , V Dblo2_1 These are the first input low-voltage blocking diodes. D blo1_1 Second input low-voltage blocking diode D blo2_1 The on-state pressure drop is a constant. , These represent the first blanking capacitors. C blk1 Second blanking capacitor C blk2 Their respective voltages; Then, in the second stage detection branch, the output voltage of the gate drive V GS Send an enable signal to cause the constant current source to output a constant current. I s3 , I s4 constant current I s3 Potential distribution channels include: Figure 2 Branches ③ and ④ in the circuit; constant current I s4 Potential distribution channels include: Figure 2 Branch road ⑦ and branch road ⑧ in the middle; The branch circuit ③ includes: a constant current source and a third adjustable resistor. R th3 Third input low-voltage blocking diode D blo3_1 First current-limiting resistor R s1 First high-voltage blocking diode D s1 First solid-state circuit breaker IGBT1; The branch circuit ④ includes: a constant current source and a third adjustable resistor. R th3 Third blanking capacitor C blk3 ; The branch ⑦ includes: a constant current source and a fourth adjustable resistor. R th4 Fourth input low-voltage blocking diode D blo4_1 Second current-limiting resistor R s2 Second high-voltage blocking diode D s2 The second solid-state circuit breaker, IGBT2; The branch circuit ⑧ includes: a constant current source and a fourth adjustable resistor. R th4 Fourth blanking capacitor C blk4 ; Through branch ④ or branch ⑧, the constant current source will supply power to the third blanking capacitor. C blk3 Or the fourth blanking capacitor C blk4 During charging, the voltages of the two blanking capacitors are respectively: V Cblk3 = V Rs1 + V Ds1 + V CE1 + V Dblo3_1 (3) V Cblk4 = V Rs1 + V Ds1 + V CE2 + V Dblo4_1 (4) in, V Ds1 , V Ds2 These are the first high-voltage blocking diodes. D s1 Second high-voltage blocking diode D s2 The on-state pressure drop is a constant. V Rs1 , V Rs2 The first current-limiting resistor is respectively R s1 Second current-limiting resistor R s2 The voltage across the two ends is a constant. V CE1 , V CE2 These are the on-state voltages of the first solid-state circuit breaker IGBT1 and the second solid-state circuit breaker IGBT2, respectively. V Dblo3_1 , V Dblo4_1 These are the third input low-voltage blocking diodes. D blo3_1 Fourth input low-voltage blocking diode D blo4_1The on-state pressure drop is a constant. V Cblk3 , V Cblk4 These represent the third blanking capacitor. C blk3 and the fourth blanking capacitor C blk4 Their respective voltages.

[0030] Among them, if the current of the power distribution system I L The direction is from the first solid-state circuit breaker IGBT1 to the second solid-state circuit breaker IGBT2, that is... Figure 2 The diagram, arranged from top to bottom, defines this as the first operating condition, i.e., when the power current flows in the forward direction. V CE1 The voltage is a positive voltage. V CE2 The voltage is negative; according to the above formulas (1), (2), (3), and (4), it can be seen that... V Cblk1 Greater than V Cblk2 , V Cblk3 Greater than V Cblk4 Therefore, the second input low-voltage blocking diode D blo2_1 Fourth input low-voltage blocking diode D blo4_1 The circuit is blocked, with only branch ①, branch ②, branch ③, and branch ④ in a valid state. Under the above conditions, the first blanking capacitor C blk1 voltage V Cblk1 Satisfying formula (1), the third blanking capacitor C blk3 It satisfies formula (3); it can be seen from this formula that the voltage of the first blanking capacitor is... V Cblk1 On-state voltage of forward-conducting IGBT1 V CE1 The phase difference is a constant, therefore the voltage of the first blanking capacitor is... V Cblk1 This can reflect the on-state voltage of IGBT1. V CE1 The size; simultaneously, the voltage of the third blanking capacitor. V Cblk3 On-state voltage of forward-conducting IGBT1 V CE1 The voltages of the third blanking capacitor also differ by a constant, therefore the voltage of the third blanking capacitor... VCblk3 It can also reflect the on-state voltage of IGBT1. V CE1 Size.

[0031] Among them, if the current of the power distribution system I L The direction is from the second solid-state circuit breaker IGBT2 to the first solid-state circuit breaker IGBT1, that is... Figure 2 The diagram, arranged from bottom to top, defines this as the second operating condition, i.e., when the power current flows in reverse. V CE2 The voltage is a positive voltage. V CE1 The voltage is negative; according to the above formulas (1), (2), (3), and (4), it can be seen that... V Cblk1 Less than V Cblk2 , V Cblk3 Less than V Cblk4 Therefore, the first input low-voltage blocking diode D blo1_1 Third input low-voltage blocking diode D blo3_1 The circuit is blocked, with only branch ⑤, branch ⑥, branch ⑦, and branch ⑧ in a valid state. Under the above conditions, the second blanking capacitor C blk2 voltage V Cblk2 Satisfying formula (2), the fourth blanking capacitor C blk4 voltage V Cblk4 It satisfies formula (4); it can be seen from this formula that the voltage of the second blanking capacitor is... V Cblk2 On-state voltage of forward-conducting IGBT2 V CE2 The phase difference is a constant, therefore the voltage of the second blanking capacitor is... V Cblk2 This can reflect the on-state voltage of IGBT2. V CE2 The size; simultaneously, the voltage of the fourth blanking capacitor. V Cblk4 On-state voltage of forward-conducting IGBT2 V CE2 The voltages of the fourth blanking capacitor also differ by a constant, therefore the voltage of the blanking capacitor... V Cblk4 It can also reflect the on-state voltage of IGBT2. VCE2 Size.

[0032] Each blanking capacitor is connected to the negative input terminal of the comparator through a corresponding adjustable resistor and an output low-voltage blocking diode, while a constant comparison voltage is connected to the positive input terminal of the comparator. V th ; When an overcurrent fault occurs in the first operating condition, as the current flowing through IGBT1 increases, V CE1 , V Cblk1 , V Cblk3 Simultaneously increase; when V Cblk1 and V Rth1 The sum equals V th and V Dblo1 When and when, or V Cblk3 and V Rth3 The sum equals V th and V Dblo3 When the sum is equal, the comparator sends a turn-off signal to turn off both IGBT1 and IGBT2 simultaneously; at this time, the on-state voltage of IGBT1... V CE1 With threshold voltage V Rth1 , V Rth3 The relationships are represented as follows: (5) (6) When an overcurrent fault occurs in the second operating condition, as the current flowing through IGBT2 increases, V CE2 , V Cblk2 , V Cblk4 Simultaneously increase; when V Cblk2 and V Rth2 The sum equals V th and V Dblo2 When the sum of, or when V Cblk4 and V Rth4 The sum equals V th andV Dblo4 When the sum is equal, the comparator sends a turn-off signal to turn off both IGBT1 and IGBT2 simultaneously; at this time, the on-state voltage of IGBT2... V CE2 With threshold voltage V Rth2 , V Rth4 The relationships are represented as follows: (7) (8).

[0033] In practical applications, the threshold voltage V Rth1 and V Rth2 Able to be controlled by adjustable resistors R th1 and R th2 Adjustment, threshold voltage V Rth3 and V Rth4 Able to be controlled by adjustable resistors R th3 and R th4 Adjustment allows for the adjustment of the overcurrent protection operating current value according to actual needs.

[0034] Among them, the first high-voltage blocking diode D s1 Second high voltage blocking diode D s2 It is a high-voltage diode, and its function is to prevent the high voltage at the emitter from damaging the detection circuit after the IGBT is turned off. Wherein, the first current-limiting resistor R s1 Second current-limiting resistor R s2 Its function is to prevent high interference from IGBT switching transients (through high voltage change rate d). v / d t (Characteristics) The parasitic capacitance of the detection circuit generates a large instantaneous current, which in turn damages the detection circuit; Wherein, the blanking capacitor C blk Its function is to reduce the voltage rise rate at the negative terminal of the comparator, thereby preventing false protection from occurring when the voltage across the IGBT fails to immediately drop to the on-state voltage upon turn-on; simultaneously, this capacitor is also used to set the delay time of the overcurrent detection circuit, i.e., the blanking time. t blk The calculation formula is as follows: (9) Where, Δ V This represents the change in blanking capacitor voltage. It's important to note that for desaturation detection of power devices in traditional converters, to ensure the detection speed of the detection circuit and the reliability of the converter system, the blanking time should be ensured. t blk The smaller the delay time, the better, provided it is greater than the turn-on time of the power device. However, unlike converters, solid-state circuit breakers, as devices for power system protection, should have a certain delay overcurrent protection function to avoid malfunctions when transient overloads occur in the power supply system. Therefore, for desaturation detection of power devices in solid-state circuit breakers, under the premise of ensuring that the power devices are in the safe operating area, it is necessary to adjust the overcurrent fault action delay time, i.e., the blanking time, by adjusting the size of the blanking capacitor. Among them, the clamping diode D blk It is a Zener diode, whose function is to limit the maximum voltage of the blanking capacitor and ensure that the comparator is not damaged by overvoltage; D blk The regulated voltage should be greater than the threshold voltage. V th It is less than the withstand voltage of the comparator input.

[0035] In summary, the above scheme, in addition to the forward conduction condition of the first operating condition, also considers the operation of the overcurrent detection circuit when the current flows in reverse under the second operating condition, thus realizing overcurrent detection under the reverse conduction condition; in conclusion, the overcurrent fault detection scheme realizes bidirectional overcurrent fault detection of solid-state circuit breakers.

[0036] The bidirectional multi-level desaturation protection circuit, based on bidirectional desaturation detection, further enables the setting of different protection action delay times for different fault currents, defined as bidirectional multi-level desaturation detection, to reduce the risk of protection maloperation under different operating conditions. In traditional solutions, multiple detection circuits are often used in parallel, and different action thresholds are set. Therefore, traditional solutions require the use of multiple expensive components (comparators, high-voltage diodes, etc.), which greatly increases the cost and size of solid-state circuit breakers. To address this, the bidirectional desaturation detection scheme has been further optimized to achieve independent adjustment of the protection delay time under different fault currents. The working principle of bidirectional multi-stage desaturation detection is as follows: when the power current... I L The direction is the first operating condition from the first solid-state circuit breaker IGBT1 to the second solid-state circuit breaker IGBT2, that is... Figure 2As shown from top to bottom, based on the working principle of bidirectional desaturation detection, only the first on-state voltage detection circuit of IGBT1 is working. In the implementation of bidirectional multi-level desaturation detection, only two levels are set, namely the first-level detection circuit and the second-level detection circuit. Then, the first-level detection circuit and the second-level detection circuit will form branches ①, ②, ③, ④, ⑤, ⑥, ⑦, and ⑧. In the first operating condition, branches ⑤, ⑥, ⑦, and ⑧ do not participate in the operation, and only branches ①, ②, ③, and ④ are working. Therefore, in steady state, the first adjustable resistor R th1 and the third adjustable resistor R th3 Right node to ground voltage V 1 and V The expression for 3 is as follows: (10) (11) when V 1 or V 3. The threshold voltage of the comparator V th The fault protection will activate when one of the following relationships is met: (12) (13) When the first-level detection branch triggers the fault protection action, it can be seen from formulas (10) and (12) that the on-state voltage of IGBT1 at this time is... V CE1 With threshold voltage V th The relationship is represented as: (14) Similarly, when the second-level detection branch triggers the fault protection action, it can be seen from formulas (11) and (13) that the on-state voltage of IGBT1 at this time is... V CE1 With threshold voltage V th The relationship can be represented as: (15) From formulas (14) and (15), it can be seen that the voltage at the positive input terminal of the comparator is... V th Without changing the first adjustable resistor R th1 and the third adjustable resistor R th3The resistance value changes the on-state voltage of the first solid-state circuit breaker IGBT1 corresponding to the first and second level detection branches when the overcurrent fault detection is activated. V CE1 Furthermore, according to formula (9), the protection action delay time of the first-level detection branch and the second-level detection branch can be adjusted by changing the first blanking capacitor. C blk1 and the third blanking capacitor C blk3 The value changes; Based on the above analysis, it can be seen that the bidirectional multi-stage desaturation protection circuit of the solid-state circuit breaker based on multi-diode modulation achieves the multi-stage desaturation detection required by the solid-state circuit breaker under the first operating condition; in the actual setting of the multi-stage desaturation detection parameters, the first adjustable resistor in the first stage detection branch is... R th1 The resistance value is set relatively large, and the first blanking capacitor is... C blk1 The value is also set to a relatively large value, and the third adjustable resistor in the second stage detection branch is also set to a relatively large value. R th3 The resistance value is set relatively small, and the third blanking capacitor is used. C blk3 The value is also set relatively small; in the event of a minor overcurrent fault, i.e., the on-state voltage of the first solid-state circuit breaker IGBT1... V EC1 At lower levels, according to formula (15), due to the third adjustable resistor in the second-stage detection branch... R th3 The resistance value is set too small, so the second-level detection branch does not activate its protection. Meanwhile, according to formulas (14) and (9), the first adjustable resistor in the first-level detection branch... R th1 The resistance value is set relatively large, and the first blanking capacitor is... C blk1 The value is also set to be relatively large, so that the first-level detection branch will take a long time to activate the protection, thus realizing the "long delay" fault protection of the solid-state circuit breaker under slight overcurrent. When a high overcurrent fault occurs, i.e. V EC1 At higher levels, both the first and second level detection branches will perform overcurrent fault detection simultaneously, but due to the blanking capacitor of the second level detection branch... C blk3 The smaller value allows the second-level detection branch to operate under protection after a shorter delay, thus achieving "short-delay" fault protection under high overcurrent faults of solid-state circuit breakers.

[0037] Among them, when the power current I LThe direction is the second operating condition from the second solid-state circuit breaker IGBT2 to the first solid-state circuit breaker IGBT1, that is... Figure 2 As shown from bottom to top, based on the working principle of bidirectional desaturation detection, only the second on-state voltage detection circuit of IGBT2 is working; under the second operating condition, branches ①, ②, ③, and ④ do not participate in the operation, only branches ⑤, ⑥, ⑦, and ⑧ are working. Therefore, in steady state, the second adjustable resistor R th2 and the fourth adjustable resistor R th4 Right node to ground voltage V 2 and V The expression for 4 is as follows: (16) (17) when V 2 or V 4. The threshold voltage of the comparator V th The fault protection will activate when one of the following relationships is met: (18) (19) When the first-level detection branch triggers the fault protection action, it can be seen from formulas (16) and (18) that the on-state voltage of IGBT2 at this time is... V CE2 With threshold voltage V th The relationship is represented as: (20) Similarly, when the second-level detection branch triggers the fault protection action, it can be seen from formulas (17) and (19) that the on-state voltage of IGBT2 at this time is... V CE2 With threshold voltage V th The relationship can be represented as: (twenty one) From formulas (20) and (21), it can be seen that the voltage at the positive input terminal of the comparator is... V th Without changing the second adjustable resistor R th2 and the fourth adjustable resistor R th4 The resistance value changes the on-state voltage of the second solid-state circuit breaker IGBT2 corresponding to the first and second level detection branches when the overcurrent fault detection is activated.V CE2 Furthermore, according to formula (9), the protection action delay time of the first-level detection branch and the second-level detection branch can be adjusted by changing the second blanking capacitor. C blk2 and the fourth blanking capacitor C blk4 The value changes; Based on the above analysis, it can be seen that the bidirectional multi-stage desaturation protection circuit of the solid-state circuit breaker based on multi-diode modulation realizes the multi-stage desaturation detection required by the solid-state circuit breaker under the second operating condition; in the actual setting of the multi-stage desaturation detection parameters, the second adjustable resistor in the first stage detection branch is... R th2 The resistance value is set relatively large, and the second blanking capacitor is... C blk2 The value is also set relatively large, and the fourth adjustable resistor in the second stage detection branch is also set relatively large. R th4 The resistance value is set relatively small, and the fourth blanking capacitor is used. C blk4 The value is also set relatively small; in the event of a minor overcurrent fault, i.e., the on-state voltage of the second solid-state circuit breaker IGBT2... V EC2 At lower levels, according to formula (21), the fourth adjustable resistor in the second-level detection branch... R th4 The resistance value is set too small, causing the second-level detection branch to fail to activate its protection. Furthermore, according to formulas (20) and (9), the second adjustable resistor in the first-level detection branch... R th2 The resistance value is set relatively large, and the second blanking capacitor is... C blk2 The value is also set to be relatively large, so that the first-level detection branch will take a long time to activate the protection, thus realizing the "long delay" fault protection of the solid-state circuit breaker under slight overcurrent. When a high overcurrent fault occurs, i.e. V EC2 At higher levels, both the first and second level detection branches will perform overcurrent fault detection simultaneously, but due to the blanking capacitor of the second level detection branch... C blk4 The smaller value allows the second-level detection branch to operate under protection after a shorter delay, thus achieving "short-delay" fault protection under high overcurrent faults of solid-state circuit breakers.

[0038] In the bidirectional multi-stage desaturation protection circuit of the solid-state circuit breaker, a first input low-voltage blocking diode is provided. D blo1_1 First output low-voltage blocking diode Dblo1 Second input low-voltage blocking diode D blo2_1 Second output low-voltage blocking diode D blo2 Third input low-voltage blocking diode D blo3_1 Third output low-voltage blocking diode D blo3 Fourth input low-voltage blocking diode D blo4_1 Fourth output low-voltage blocking diode D blo4 Therefore, there is no interference between multiple detection circuits; Furthermore, based on the first and second level detection branches, more level detection branches can be added in parallel to form a more multi-level bidirectional desaturation protection system.

[0039] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A bidirectional multi-stage desaturation protection circuit for a solid-state circuit breaker based on multi-diode modulation, characterized in that, The bidirectional multi-level desaturation protection circuit is connected to the bidirectional solid-state circuit breaker body at the front end; the bidirectional solid-state circuit breaker body includes a gate driver, a first solid-state circuit breaker IGBT1 and a second solid-state circuit breaker IGBT2, which are used to send an enable signal and an on-state voltage characterizing the original fault information to the bidirectional multi-level desaturation protection circuit. The bidirectional multi-level desaturation protection circuit includes two symmetrically parallel on-state voltage detection circuits, namely a first on-state voltage detection circuit and a second on-state voltage detection circuit. The first on-state voltage detection circuit includes a first high-voltage blocking diode. D s1 First current-limiting resistor R s1 A constant current source and a second on-state voltage detection circuit including a second high-voltage blocking diode. D s2 Second current-limiting resistor R s2 With a constant current source, this structure is used to detect the on-state voltage of power devices connected in reverse series and to prevent high voltage damage to the bidirectional multi-stage desaturation protection circuit; The bidirectional multi-level desaturation protection circuit further includes: multiple parallel-connected and structurally identical graded detection branches, including at least a first graded detection branch and a second graded detection branch; The first graded detection branch includes a first parameter adjustment circuit and a second parameter adjustment circuit; The first parameter adjustment circuit includes: a first adjustable resistor. R th1 First blanking capacitor C blk1 First input low-voltage blocking diode D blo1_1 First output low-voltage blocking diode D blo1 The second parameter adjustment circuit includes: a second adjustable resistor. R th2 Second blanking capacitor C blk2 Second input low-voltage blocking diode D blo2_1 Second output low-voltage blocking diode D blo2 ; The second graded detection branch includes a third parameter adjustment circuit and a fourth parameter adjustment circuit; The third parameter adjustment circuit includes: a third adjustable resistor. R th3 Third blanking capacitor C blk3 Third input low-voltage blocking diode D blo3_1 Third output low-voltage blocking diode D blo3 The fourth parameter adjustment circuit includes: a fourth adjustable resistor. R th4 Fourth blanking capacitor C blk4 Fourth input low-voltage blocking diode D blo4_1 Fourth output low-voltage blocking diode D blo4 ; Wherein, the first adjustable resistor R th1 Second adjustable resistor R th2 Used to adjust the branch detection threshold of the first-level detection branch; third adjustable resistor R th3 and the fourth adjustable resistor R th4 Used to adjust the branch detection threshold of the second-level detection branch; First blanking capacitor C blk1 Second blanking capacitor C blk2 The third blanking capacitor is used to adjust the delay time of the first stage detection branch, i.e., the blanking time. C blk3 and the fourth blanking capacitor C blk4 Used to adjust the delay time of the second-level detection branch, i.e., the blanking time; First output low-voltage blocking diode D blo1 The second output low-voltage blocking diode is placed on the line output of the first parameter adjustment circuit. D blo2 The third output low-voltage blocking diode is placed on the line output of the second parameter adjustment circuit. D blo3 The fourth output low-voltage blocking diode is placed on the line output of the third parameter adjustment circuit. D blo4 It is placed on the line output of the fourth parameter adjustment circuit to avoid mutual interference between on-state voltage detection circuits, thereby realizing the shared back-end fault judgment circuit and the setting of multi-level desaturation detection parameters; The fault detection circuit includes a clamping diode. D blk The above symmetrical parallel design uses a shared fault determination circuit structure, which can ensure the consistency of overcurrent detection in both directions and reduce the difficulty of circuit debugging while reducing the hardware size and cost of the protection circuit. First input low-voltage blocking diode D blo1_1 The second input low-voltage blocking diode is placed on the line input of the first parameter adjustment circuit. D blo2_1 The third input low-voltage blocking diode is placed on the line input of the second parameter adjustment circuit. D blo3_1 The fourth input low-voltage blocking diode is placed on the line input of the third parameter adjustment circuit. D blo4_1 It is placed on the line input of the fourth parameter adjustment circuit to avoid mutual interference between on-state voltage detection circuits, thereby enabling multiple graded detection branches, including the first graded detection branch and the second graded detection branch, to share the first on-state voltage detection circuit and the second on-state voltage detection circuit.

2. The bidirectional multi-stage desaturation protection circuit for a solid-state circuit breaker based on multi-diode modulation as described in claim 1, characterized in that, The working principle of the bidirectional multi-level desaturation protection circuit for bidirectional desaturation detection is as follows: When the output voltage of the gate drive is positive, the first solid-state circuit breaker IGBT1 and the second solid-state circuit breaker IGBT2 will be turned on at the same time. At this time, the bus voltage forms a path through the first solid-state circuit breaker IGBT1, the second solid-state circuit breaker IGBT2 and the load, and the power distribution system starts to work normally. Then, in the first stage detection branch, the output voltage of the gate drive V GS Send an enable signal to cause the constant current source to output a constant current. I s1 , I s2 constant current I s1 Potential current-carrying branches include: branch ①, branch ②; constant current. I s2 Potential circulation routes include: branch route ⑤ and branch route ⑥; The branch circuit ① includes: a constant current source and a first adjustable resistor. R th1 First input low-voltage blocking diode D blo1_1 First current-limiting resistor R s1 First high-voltage blocking diode D s1 First solid-state circuit breaker IGBT1; The branch ② includes: a constant current source and a first adjustable resistor. R th1 First blanking capacitor C blk1 ; The branch circuit ⑤ includes: a constant current source and a second adjustable resistor. R th2 Second input low-voltage blocking diode D blo2_1 Second current-limiting resistor R s2 Second high-voltage blocking diode D s2 The second solid-state circuit breaker, IGBT2; The branch circuit ⑥ includes: a constant current source and a second adjustable resistor. R th2 Second blanking capacitor C blk2 ; Through branch ② or branch ⑥, the constant current source will supply power to the first blanking capacitor. C blk1 Or the second blanking capacitor C blk2 During charging, the voltages of the two blanking capacitors are respectively: （1） （2） in, V Ds1 , V Ds2 These are the first high-voltage blocking diodes. D s1 Second high-voltage blocking diode D s2 The on-state pressure drop is a constant. V Rs1 , V Rs2 The first current-limiting resistor is respectively R s1 Second current-limiting resistor R s2 The voltage across the two ends is a constant. V CE1 , V CE2 These are the on-state voltages of the first solid-state circuit breaker IGBT1 and the second solid-state circuit breaker IGBT2, respectively. V Dblo1_1 , V Dblo2_1 These are the first input low-voltage blocking diodes. D blo1_1 Second input low-voltage blocking diode D blo2_1 The on-state pressure drop is a constant. , These represent the first blanking capacitors. C blk1 Second blanking capacitor C blk2 Their respective voltages; Then, in the second stage detection branch, the output voltage of the gate drive V GS Send an enable signal to cause the constant current source to output a constant current. I s3 , I s4 constant current I s3 Potential current-carrying branches include: branch ③, branch ④; constant current I s4 Potential circulation routes include: branch route ⑦ and branch route ⑧; The branch circuit ③ includes: a constant current source and a third adjustable resistor. R th3 Third input low-voltage blocking diode D blo3_1 First current-limiting resistor R s1 First high-voltage blocking diode D s1 First solid-state circuit breaker IGBT1; The branch circuit ④ includes: a constant current source and a third adjustable resistor. R th3 Third blanking capacitor C blk3 ; The branch ⑦ includes: a constant current source and a fourth adjustable resistor. R th4 Fourth input low-voltage blocking diode D blo4_1 Second current-limiting resistor R s2 Second high-voltage blocking diode D s2 The second solid-state circuit breaker, IGBT2; The branch circuit ⑧ includes: a constant current source and a fourth adjustable resistor. R th4 Fourth blanking capacitor C blk4 ; Through branch ④ or branch ⑧, the constant current source will supply power to the third blanking capacitor. C blk3 Or the fourth blanking capacitor C blk4 During charging, the voltages of the two blanking capacitors are respectively: V Cblk3 = V Rs1 + V Ds1 + V CE1 + V Dblo3_1 （3） V Cblk4 = V Rs1 + V Ds1 + V CE2 + V Dblo4_1 （4） in, V Ds1 , V Ds2 These are the first high-voltage blocking diodes. D s1 Second high-voltage blocking diode D s2 The on-state pressure drop is a constant. V Rs1 , V Rs2 The first current-limiting resistor is respectively R s1 Second current-limiting resistor R s2 The voltage across the two ends is a constant. V CE1 , V CE2 These are the on-state voltages of the first solid-state circuit breaker IGBT1 and the second solid-state circuit breaker IGBT2, respectively. V Dblo3_1 , V Dblo4_1 These are the third input low-voltage blocking diodes. D blo3_1 Fourth input low-voltage blocking diode D blo4_1 The on-state pressure drop is a constant. V Cblk3 , V Cblk4 These represent the third blanking capacitor. C blk3 and the fourth blanking capacitor C blk4 Their respective voltages.

3. The bidirectional multi-stage desaturation protection circuit for a solid-state circuit breaker based on multi-diode modulation as described in claim 2, characterized in that, If the power distribution system current I L The direction is from the first solid-state circuit breaker IGBT1 to the second solid-state circuit breaker IGBT2. This is defined as the first operating condition, i.e., when the power current flows in the forward direction. V CE1 The voltage is a positive voltage. V CE2 The voltage is negative; according to the above formulas (1), (2), (3), and (4), it can be seen that... V Cblk1 Greater than V Cblk2 , V Cblk3 Greater than V Cblk4 Therefore, the second input low-voltage blocking diode D blo2_1 Fourth input low-voltage blocking diode D blo4_1 The circuit is blocked, with only branch ①, branch ②, branch ③, and branch ④ in a valid state. Under the above conditions, the first blanking capacitor C blk1 voltage V Cblk1 Satisfying formula (1), the third blanking capacitor C blk3 It satisfies formula (3); it can be seen from this formula that the voltage of the first blanking capacitor is... V Cblk1 On-state voltage of forward-conducting IGBT1 V CE1 The phase difference is a constant, therefore the voltage of the first blanking capacitor is... V Cblk1 This can reflect the on-state voltage of IGBT1. V CE1 The size; simultaneously, the voltage of the third blanking capacitor. V Cblk3 On-state voltage of forward-conducting IGBT1 V CE1 The voltages of the third blanking capacitor also differ by a constant, therefore the voltage of the third blanking capacitor... V Cblk3 It can also reflect the on-state voltage of IGBT1. V CE1 Size.

4. The bidirectional multi-stage desaturation protection circuit for a solid-state circuit breaker based on multi-diode modulation as described in claim 3, characterized in that, If the power distribution system current I L The direction is from the second solid-state circuit breaker IGBT2 to the first solid-state circuit breaker IGBT1. This is defined as the second operating condition, i.e., when the power current flows in reverse. V CE2 The voltage is a positive voltage. V CE1 The voltage is negative; according to the above formulas (1), (2), (3), and (4), it can be seen that... V Cblk1 Less than V Cblk2 , V Cblk3 Less than V Cblk4 Therefore, the first input low-voltage blocking diode D blo1_1 Third input low-voltage blocking diode D blo3_1 The circuit is blocked, with only branch ⑤, branch ⑥, branch ⑦, and branch ⑧ in a valid state. Under the above conditions, the second blanking capacitor C blk2 voltage V Cblk2 Satisfying formula (2), the fourth blanking capacitor C blk4 voltage V Cblk4 It satisfies formula (4); it can be seen from this formula that the voltage of the second blanking capacitor is... V Cblk2 On-state voltage of forward-conducting IGBT2 V CE2 The phase difference is a constant, therefore the voltage of the second blanking capacitor is... V Cblk2 This can reflect the on-state voltage of IGBT2. V CE2 The size; simultaneously, the voltage of the fourth blanking capacitor. V Cblk4 On-state voltage of forward-conducting IGBT2 V CE2 The voltages of the fourth blanking capacitor also differ by a constant, therefore the voltage of the blanking capacitor... V Cblk4 It can also reflect the on-state voltage of IGBT2. V CE2 Size.

5. The bidirectional multi-stage desaturation protection circuit for a solid-state circuit breaker based on multi-diode modulation as described in claim 4, characterized in that, Each blanking capacitor is connected to the negative input of the comparator via a corresponding adjustable resistor and an output low-voltage blocking diode. A constant comparison voltage is connected to the positive input of the comparator. V th ; When an overcurrent fault occurs in the first operating condition, as the current flowing through IGBT1 increases, V CE1 , V Cblk1 , V Cblk3 Simultaneously increase; when V Cblk1 and V Rth1 The sum equals V th and V Dblo1 When and when, or V Cblk3 and V Rth3 The sum equals V th and V Dblo3 When the sum is equal, the comparator sends a turn-off signal to turn off both IGBT1 and IGBT2 simultaneously; at this time, the on-state voltage of IGBT1... V CE1 With threshold voltage V Rth1 , V Rth3 The relationships are represented as follows: （5） （6） When an overcurrent fault occurs in the second operating condition, as the current flowing through IGBT2 increases, V CE2 , V Cblk2 , V Cblk4 Simultaneously increase; when V Cblk2 and V Rth2 The sum equals V th and V Dblo2 When the sum of, or when V Cblk4 and V Rth4 The sum equals V th and V Dblo4 When the sum is equal, the comparator sends a turn-off signal to turn off both IGBT1 and IGBT2 simultaneously; at this time, the on-state voltage of IGBT2... V CE2 With threshold voltage V Rth2 , V Rth4 The relationships are represented as follows: （7） （8）。 6. The bidirectional multi-stage desaturation protection circuit for a solid-state circuit breaker based on multi-diode modulation as described in claim 5, characterized in that, In practical applications, threshold voltage V Rth1 and V Rth2 Able to be controlled by adjustable resistors R th1 and R th2 Adjustment, threshold voltage V Rth3 and V Rth4 Able to be controlled by adjustable resistors R th3 and R th4 Adjustment allows for the adjustment of the overcurrent protection operating current value according to actual needs.

7. The bidirectional multi-stage desaturation protection circuit for a solid-state circuit breaker based on multi-diode modulation as described in claim 5, characterized in that, The first high voltage blocking diode D s1 Second high voltage blocking diode D s2 It is a high-voltage diode, and its function is to prevent the high voltage at the emitter from damaging the detection circuit after the IGBT is turned off. Wherein, the first current-limiting resistor R s1 Second current-limiting resistor R s2 Its function is to prevent the high interference from IGBT switching transients from generating a large instantaneous current through the parasitic capacitance of the detection circuit, thereby damaging the detection circuit; Wherein, the blanking capacitor C blk Its function is to reduce the voltage rise rate at the negative terminal of the comparator, thereby preventing false protection from occurring when the voltage across the IGBT fails to immediately drop to the on-state voltage upon turn-on; simultaneously, this capacitor is also used to set the delay time of the overcurrent detection circuit, i.e., the blanking time. t blk The calculation formula is as follows: （9） Where, Δ V This represents the change in blanking capacitor voltage. It's important to note that for desaturation detection of power devices in traditional converters, to ensure the detection speed of the detection circuit and the reliability of the converter system, the blanking time should be ensured. t blk The smaller the delay time, the better, provided it is greater than the turn-on time of the power device. However, unlike converters, solid-state circuit breakers, as devices for power system protection, should have a certain delay overcurrent protection function to avoid malfunctions when transient overloads occur in the power supply system. Therefore, for desaturation detection of power devices in solid-state circuit breakers, under the premise of ensuring that the power devices are in the safe operating area, it is necessary to adjust the overcurrent fault action delay time, i.e., the blanking time, by adjusting the size of the blanking capacitor. Among them, the clamping diode D blk It is a Zener diode, whose function is to limit the maximum voltage of the blanking capacitor and ensure that the comparator is not damaged by overvoltage; D blk The regulated voltage should be greater than the threshold voltage. V th It is less than the withstand voltage of the comparator input.

8. The bidirectional multi-stage desaturation protection circuit for a solid-state circuit breaker based on multi-diode modulation as described in claim 5, characterized in that, The bidirectional multi-level desaturation protection circuit, based on bidirectional desaturation detection, further enables the setting of different protection action delay times for different fault currents, which is defined as bidirectional multi-level desaturation detection, in order to reduce the risk of protection maloperation under different operating conditions. The working principle of bidirectional multi-stage desaturation detection is as follows: when the power current... I L The direction is from the first solid-state circuit breaker IGBT1 to the second solid-state circuit breaker IGBT2 in the first operating condition. As can be seen from the working principle of bidirectional desaturation detection, only the first on-state voltage detection circuit of IGBT1 is working. In the implementation of bidirectional multi-level desaturation detection, only two levels are set, namely the first level detection circuit and the second level detection circuit. Then the first level detection circuit and the second level detection circuit will form branches ①, ②, ③, ④, ⑤, ⑥, ⑦ and ⑧. In the first operating condition, branches ⑤, ⑥, ⑦ and ⑧ do not participate in the operation, and only branches ①, ②, ③ and ④ are working. Therefore, in steady state, the first adjustable resistor R th1 and the third adjustable resistor R th3 Right node to ground voltage V 1 and V The expression for 3 is as follows: （10） （11） when V 1 or V 3. The threshold voltage of the comparator V th The fault protection will activate when one of the following relationships is met: （12） （13） When the first-level detection branch triggers the fault protection action, it can be seen from formulas (10) and (12) that the on-state voltage of IGBT1 at this time is... V CE1 With threshold voltage V th The relationship is represented as: （14） Similarly, when the second-level detection branch triggers the fault protection action, it can be seen from formulas (11) and (13) that the on-state voltage of IGBT1 at this time is... V CE1 With threshold voltage V th The relationship can be represented as: （15） From formulas (14) and (15), it can be seen that the voltage at the positive input terminal of the comparator is... V th Without changing the first adjustable resistor R th1 and the third adjustable resistor R th3 The resistance value changes the on-state voltage of the first solid-state circuit breaker IGBT1 corresponding to the first and second level detection branches when the overcurrent fault detection is activated. V CE1 Furthermore, according to formula (9), the protection action delay time of the first-level detection branch and the second-level detection branch can be adjusted by changing the first blanking capacitor. C blk1 and the third blanking capacitor C blk3 The value changes; Based on the above analysis, it can be seen that the bidirectional multi-stage desaturation protection circuit of the solid-state circuit breaker based on multi-diode modulation achieves the multi-stage desaturation detection required by the solid-state circuit breaker under the first operating condition; in the actual setting of the multi-stage desaturation detection parameters, the first adjustable resistor in the first stage detection branch is... R th1 The resistance value is set relatively large, and the first blanking capacitor is... C blk1 The value is also set to a relatively large value, and the third adjustable resistor in the second stage detection branch is also set to a relatively large value. R th3 The resistance value is set relatively small, and the third blanking capacitor is used. C blk3 The value is also set relatively small; in the event of a minor overcurrent fault, i.e., the on-state voltage of the first solid-state circuit breaker IGBT1... V EC1 At lower levels, according to formula (15), due to the third adjustable resistor in the second-stage detection branch... R th3 The resistance value is set too small, so the second-level detection branch does not activate its protection. Meanwhile, according to formulas (14) and (9), the first adjustable resistor in the first-level detection branch... R th1 The resistance value is set relatively large, and the first blanking capacitor is... C blk1 The value is also set to be relatively large, so that the first-level detection branch will take a long time to activate the protection, thus realizing the "long delay" fault protection of the solid-state circuit breaker under slight overcurrent. When a high overcurrent fault occurs, i.e. V EC1 At higher levels, both the first and second level detection branches will perform overcurrent fault detection simultaneously, but due to the blanking capacitor of the second level detection branch... C blk3 The smaller value allows the second-level detection branch to operate under protection after a shorter delay time, thus achieving "short-delay" fault protection under high overcurrent faults of solid-state circuit breakers.

9. The bidirectional multi-stage desaturation protection circuit for a solid-state circuit breaker based on multi-diode modulation as described in claim 8, characterized in that, When power current I L The direction is the second working condition from the second solid-state circuit breaker IGBT2 to the first solid-state circuit breaker IGBT1. As can be seen from the working principle of bidirectional desaturation detection, only the second on-state voltage detection circuit of IGBT2 works. In the second working condition, branches ①, ②, ③, and ④ do not participate in the work, and only branches ⑤, ⑥, ⑦, and ⑧ work. Therefore, in steady state, the second adjustable resistor R th2 and the fourth adjustable resistor R th4 Right node to ground voltage V 2 and V The expression for 4 is as follows: （16） （17） when V 2 or V 4. The threshold voltage of the comparator V th The fault protection will activate when one of the following relationships is met: （18） （19） When the first-level detection branch triggers the fault protection action, it can be seen from formulas (16) and (18) that the on-state voltage of IGBT2 at this time is... V CE2 With threshold voltage V th The relationship is represented as: （20） Similarly, when the second-level detection branch triggers the fault protection action, it can be seen from formulas (17) and (19) that the on-state voltage of IGBT2 at this time is... V CE2 With threshold voltage V th The relationship can be represented as: （21） From formulas (20) and (21), it can be seen that the voltage at the positive input terminal of the comparator is... V th Without changing the second adjustable resistor R th2 and the fourth adjustable resistor R th4 The resistance value changes the on-state voltage of the second solid-state circuit breaker IGBT2 corresponding to the first and second level detection branches when the overcurrent fault detection is activated. V CE2 Furthermore, according to formula (9), the protection action delay time of the first-level detection branch and the second-level detection branch can be adjusted by changing the second blanking capacitor. C blk2 and the fourth blanking capacitor C blk4 The value changes; Based on the above analysis, it can be seen that the bidirectional multi-stage desaturation protection circuit of the solid-state circuit breaker based on multi-diode modulation realizes the multi-stage desaturation detection required by the solid-state circuit breaker under the second operating condition; in the actual setting of the multi-stage desaturation detection parameters, the second adjustable resistor in the first stage detection branch is... R th2 The resistance value is set relatively large, and the second blanking capacitor is... C blk2 The value is also set relatively large, and the fourth adjustable resistor in the second stage detection branch is also set relatively large. R th4 The resistance value is set relatively small, and the fourth blanking capacitor is used. C blk4 The value is also set relatively small; in the event of a minor overcurrent fault, i.e., the on-state voltage of the second solid-state circuit breaker IGBT2... V EC2 At lower levels, according to formula (21), the fourth adjustable resistor in the second-level detection branch... R th4 The resistance value is set too small, causing the second-level detection branch to fail to activate its protection. Furthermore, according to formulas (20) and (9), the second adjustable resistor in the first-level detection branch... R th2 The resistance value is set relatively large, and the second blanking capacitor is... C blk2 The value is also set to be relatively large, so that the first-level detection branch will take a long time to activate the protection, thus realizing the "long delay" fault protection of the solid-state circuit breaker under slight overcurrent. When a high overcurrent fault occurs, i.e. V EC2 At higher levels, both the first and second level detection branches will perform overcurrent fault detection simultaneously, but due to the blanking capacitor of the second level detection branch... C blk4 The smaller value allows the second-level detection branch to operate under protection after a shorter delay time, thus achieving "short-delay" fault protection under high overcurrent faults of solid-state circuit breakers.

10. The bidirectional multi-stage desaturation protection circuit for a solid-state circuit breaker based on multi-diode modulation as described in claim 9, characterized in that, In the bidirectional multi-stage desaturation protection circuit of the solid-state circuit breaker, a first input low-voltage blocking diode is provided. D blo1_1 First output low-voltage blocking diode D blo1 Second input low-voltage blocking diode D blo2_1 Second output low-voltage blocking diode D blo2 Third input low-voltage blocking diode D blo3_1 Third output low-voltage blocking diode D blo3 Fourth input low-voltage blocking diode D blo4_1 Fourth output low-voltage blocking diode D blo4 Therefore, there is no interference between multiple detection circuits; Furthermore, based on the first and second level detection branches, more level detection branches can be added in parallel to form a more multi-level bidirectional desaturation protection system.

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