A short circuit protection device for DC high voltage output of PCS

Abstract

The application discloses a DC high-voltage output short-circuit protection device suitable for a PCS, which comprises an input / output interface terminal, a filter circuit, an input / output sampling resistor, a bleeder circuit, a fast protection circuit, a current sampling Hall, a fiber transceiver, an auxiliary power board card and a sampling control board card.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, and in particular to a DC high-voltage output short-circuit protection device suitable for PCS. Background Technology

[0002] This protection device is particularly suitable for high-voltage power supply systems (such as 18kV / 10A conditions) required for expensive, high-power microwave devices such as klystrons, and can also be widely used in DC high-voltage output scenarios of energy storage converters (PCS). As the core hub of an energy storage system, the DC side of the PCS often operates under high-voltage conditions, undertaking the critical responsibility of bidirectional energy conversion between battery energy storage and grid energy. The safe and stable operation of its DC high-voltage output directly determines the reliability and safety of the entire energy storage system.

[0003] As a core component of high-power microwave systems, klystrons are expensive (ranging from hundreds of thousands to millions of yuan). If arcing, breakdown, or output short circuit occurs between electrodes under high voltage, a huge short-circuit surge current will be generated within microseconds, which can easily lead to permanent damage to the klystron or power system failure.

[0004] Traditional protection solutions (such as fuses, mechanical contactors, or thyristor turn-off) typically have response times in the millisecond range, which cannot effectively suppress transient peak currents and cannot meet the stringent requirements of klystrons for rapid fault isolation and energy absorption. They also cannot adapt to the rapid protection requirements of PCS DC high voltage output short circuits, cannot promptly disconnect fault circuits or absorb short-circuit energy, and cannot ensure the safety of equipment and systems.

[0005] Therefore, there is an urgent need for a low-cost, high-response klystron short-circuit rapid protection device to avoid equipment damage and system accidents caused by short-circuit faults. Summary of the Invention

[0006] The purpose of this invention is to solve the above-mentioned problems and provide a low-cost, high-response solution for fast short-circuit protection of klystrons, mainly used in 20kV klystron high-voltage DC power supplies.

[0007] To achieve the above objectives, the technical solution of the present invention is: a DC high-voltage output short-circuit protection device suitable for PCS, comprising:

[0008] The input / output interface terminal is provided with an input interface that connects to a 20kV DC high voltage and a 220V AC auxiliary power supply, and an output interface that outputs a 20kV DC high voltage to provide a stable high voltage power supply for the klystron load.

[0009] The filter circuit is connected to the high-voltage main circuit and is used to filter out high-frequency noise.

[0010] Input / output sampling resistors are connected in parallel to the input and output terminals of the high-voltage main circuit, respectively, to collect input and output voltage signals.

[0011] The discharge circuit, connected to the high-voltage main circuit, is normally closed and open during shutdown to release residual electrical energy;

[0012] A fast protection circuit, connected in series in the high-voltage main circuit, is used to limit the peak current and disconnect the high-voltage switch within microseconds to cut off the power supply to the main circuit when the load is short-circuited.

[0013] A current sampling Hall effect sensor is connected in series in the high-voltage main circuit to collect the circuit current signal in real time.

[0014] Cooling fans are used to dissipate heat from heat-generating components.

[0015] Fiber optic transceivers are used to receive external control signals and provide feedback on status and sampled signals.

[0016] Auxiliary power supply board, used to provide multiple DC and AC power supplies;

[0017] The sampling control board is used to implement overall logic and protection control, including discharge relay on / off control, cooling fan start / stop control, signal acquisition and short-circuit fast protection;

[0018] The chassis structure components adopt a composite design with an inner and outer layer. The inner layer is covered with an insulating epoxy board, and the outer layer is made of a metal shielding plate.

[0019] Preferably, the fast protection circuit includes a current-limiting resistor, a current-limiting inductor, and a protective high-voltage switch; the current-limiting inductor is used to suppress sudden current changes and buy time for the high-voltage switch to cut off the power supply, and the protective high-voltage switch is used to close or open in the event of a short circuit to discharge energy or cut off the circuit.

[0020] Preferably, the current-limiting resistor is composed of multiple high-voltage non-inductive resistors connected in parallel, with an equivalent resistance of 20Ω, used to limit the maximum short-circuit current in the high-voltage circuit; the current-limiting inductor has an inductance of not less than 30mH, a rated current of 10A, and an insulation withstand voltage rating of 30kV.

[0021] Preferably, the sampling control board includes a voltage short-circuit protection circuit. This circuit determines a short-circuit fault by acquiring the voltage signals at the input and output terminals of the high-voltage main circuit, respectively, and using the difference in voltage drop rates between the output and input terminals.

[0022] Preferably, the voltage short-circuit protection circuit further includes a protection circuit to prevent malfunction.

[0023] Preferably, the sampling control board further includes an overcurrent protection circuit, which is set with a conventional overcurrent threshold and a short-circuit overcurrent threshold. When the detected current exceeds the conventional overcurrent threshold, conventional overcurrent protection is performed, and when the detected current exceeds the short-circuit overcurrent threshold, short-circuit protection is performed. It also forms redundant protection with the voltage short-circuit protection.

[0024] Preferably, the discharge circuit includes a high-voltage relay and a discharge resistor. The high-voltage relay is normally closed and open when the high-voltage power supply is shut down, and the discharge resistor is connected to release the residual electrical energy in the energy storage element, so that the circuit voltage drops rapidly to a safe range.

[0025] Preferably, the external control signals received by the fiber optic transceiver include a discharge relay disconnect signal, a high-voltage switch closing signal, and a reset signal; the feedback signals include the discharge relay status, voltage / current acquisition signals, and voltage / current fault protection signals.

[0026] Preferably, the cooling fan is controlled by a sampling control board. The sampling control board controls the start and stop of the cooling fan by detecting temperature signals and / or main circuit current signals through a thermistor. The cooling fan is started when the temperature is higher than 40°C or the current is greater than 1A.

[0027] Preferably, in the chassis structure assembly, the sampling control board adopts an all-metal enclosed shell to resist high electric field interference and strong electromagnetic field impact generated when the load is short-circuited; the input / output interface terminals adopt high-voltage connectors with a rated voltage of not less than 30kV.

[0028] The DC high-voltage output short-circuit protection device for PCS disclosed in this invention has the following advantages compared with existing technologies: 1. Fast response speed: short-circuit protection action can reach the microsecond level, effectively limiting the peak short-circuit current and significantly reducing the impact on the klystron and power supply. 2. Employing a dual redundancy design of voltage drop difference logic and overcurrent protection, improving the reliability and anti-interference capability of the protection. 3. The device structure adopts internal and external composite shielding and a fully enclosed metal control board, which can resist high-voltage and strong electromagnetic interference and is suitable for harsh electrical environments. 4. Achieving high- and low-voltage electrically isolated signal transmission through a fiber optic transceiver further enhances system safety. Attached Figure Description

[0029] Figure 1 This is the overall circuit diagram of the present invention.

[0030] Figure 2 This is a schematic diagram of the interface of the device of the present invention.

[0031] Figure 3 This is a schematic diagram of the interface of the control sampling board of the present invention.

[0032] Figure 4This is a schematic diagram of the auxiliary power supply principle of the present invention.

[0033] Figure 5 This is the circuit diagram for starting and stopping the cooling fan of this invention.

[0034] Figure 6 This is a circuit diagram of the reset signal of the present invention.

[0035] Figure 7 This is a circuit diagram of the discharge relay control circuit of the present invention.

[0036] Figure 8 This is a circuit diagram of the current sampling circuit of the present invention.

[0037] Figure 9 This is the overcurrent protection circuit diagram of the present invention.

[0038] Figure 10 This is a voltage sampling circuit diagram of the present invention.

[0039] Figure 11 This is a short-circuit protection circuit diagram for the present invention.

[0040] Figure 12 Extended schematic diagram of the overall principle of this invention.

[0041] Figure 13 This is a simulation diagram of the 20kV busbar short-circuit protection of the present invention.

[0042] Figure 14 The present invention defines the maximum short-circuit creep current when the current-limiting inductor is 20mH and the time is 50μs, 100μs, 200μs, and 300μs.

[0043] Figure 15 This invention defines the maximum short-circuit creep current when the current-limiting inductor is 30mH and the time intervals are 50μs, 100μs, 200μs, and 300μs.

[0044] Figure 16 This invention defines the maximum short-circuit creep current when the current-limiting inductor is 40mH and the time intervals are 50μs, 100μs, 200μs, and 300μs.

[0045] Figure 17 This invention defines the maximum short-circuit creep current when the current-limiting inductor is 50mH and the time intervals are 50μs, 100μs, 200μs, and 300μs. Detailed Implementation

[0046] The principle of the present invention will be further explained below with reference to the accompanying drawings. The DC high-voltage output short-circuit protection device suitable for PCS includes input / output interface terminals, a filter circuit, input / output sampling resistors, a discharge circuit, a fast protection circuit, a current sampling Hall effect sensor, a cooling fan, a fiber optic transceiver, an auxiliary power board, a sampling control board, and chassis structural components.

[0047] Figure 1 and Figure 12 These are two implementation schemes for DC high voltage output short circuit protection devices suitable for PCS, with the main difference being the different protection action mechanisms. Figure 1 The protection method of directly cutting off the high-voltage main circuit by using a high-voltage switch blocks the transmission of energy from the main circuit to the load side through physical circuit breaking. Figure 12 The energy in the main circuit is quickly released through a high-voltage switch, but the main circuit remains connected, and a small amount of residual energy may still exist on the load side.

[0048] Figure 1 Medium and high voltage switches have a relatively small maximum breaking current, with a peak breaking current of about 200A. Their advantage is that they can be miniaturized; their disadvantage is that the high voltage switch is easily damaged when the protection fails.

[0049] Figure 2 The peak current of the medium- and high-voltage switch is about 3kA, which is greater than the maximum discharge current of 2kA. Its advantages are safety, reliability and low risk of damage; its disadvantages are its large size and poor installation convenience.

[0050] This invention is based on Figure 1 The protection method will be explained.

[0051] Input / output interface terminal design:

[0052] The device's bus voltage is 20kV, classifying it as a high-voltage system. Its input / output interface terminals (CN1, CN2, CN3, CN4) should use high-voltage connectors with a rated voltage of not less than 30kV. This design selects LHZS40IID / LHGP40IID series high-voltage connectors, with a rated voltage of 40kV and a rated current of 10A, which meets the system's withstand voltage and current carrying requirements. The main circuit conductors also use high-voltage conductors with a rated voltage of not less than 30kV and a rated current of 10A, matching the connectors and system operating conditions.

[0053] Filter circuit design:

[0054] The low-pass filter circuit, composed of common-mode filters (L3, C1, C3) and differential-mode filters (L1, C2), can filter out high-frequency noise, with a designed cutoff frequency of 100kHz.

[0055] Calculation formula using cutoff frequency:

[0056] Calculations show that: the differential mode capacitors (C1, C3) have a capacitance of 2nF / 30kV. The differential mode inductor (L3) has an inductance of 630uH, a current carrying capacity of 10A, and a maximum withstand voltage of 30kV. The common mode capacitor (C2) has a capacitance of 100nF / 30kV. The common mode inductor (L1) has an inductance of 25uH, a current carrying capacity of 10A, a maximum withstand voltage of 2kV, and is a floating design.

[0057] Input / output sampling resistors:

[0058] The input / output sampling resistors (RS1, RS2) are high-voltage resistor dividers. Considering the range of output voltage and output sampling value, MTX series thick film non-inductive high-voltage divider resistors are selected, with a resistance ratio of 2000:1, a total resistance of 100MΩ, a voltage divider resistor of 50kΩ, a rated power of 20W, a maximum operating voltage of 50kV, and a relative accuracy of no more than 1%.

[0059] Bleeding circuit design:

[0060] The discharge relay (RLY1) is a high-voltage relay with a rated voltage of not less than 30kV. The specific model is JGC-61 or GT61A series high-voltage ceramic vacuum relay, with a rated operating voltage of DC35kV, a rated contact current of 20A, and a coil resistance of 75Ω±10%.

[0061] The bleeder resistors (R4, R7) are high-voltage resistors, specifically the RIG8B high-power high-voltage glass glaze film non-inductive resistor. This resistor has a rated power of 250W, a nominal resistance of 200kΩ, and a limiting voltage of 80kV. In practical applications, two resistors are used in series.

[0062] The discharge time was calculated and verified as follows:

[0063] Discharge occurs only through the bleed resistor (ignoring the klystron load). Assuming the total capacitance C in the high-voltage power supply and main circuit is 25μF, and neglecting the inductance of the discharge circuit, the total resistance R of the two 200kΩ bleed resistors connected in series is 400kΩ.

[0064] According to the RC discharge formula (Where U0 = 20kV, Ut = 24V, C = 25μF = 25 × 10⁻⁶) 6 F, R=400kΩ=400×10³Ω),

[0065] The calculation is as follows: ≈67s.

[0066] When the high-voltage power supply is shut down normally, the main circuit energy storage capacitor can be discharged through the klystron load. At this time, the discharge relay is not yet closed, and the maximum equivalent resistance of the klystron load is about 10kΩ.

[0067] Substitute into the above RC discharge formula to calculate: ≈2s. Considering the actual working conditions (including minor circuit losses), after the high-voltage power supply is normally shut down for 2s, the main circuit can be ensured to discharge to a safe voltage of 24V.

[0068] Fast protection circuit design

[0069] The fast protection circuit consists of current-limiting resistors (R1, R2, R3, R5, R6), current-limiting inductor (L2), and high-voltage protection switch (U1). These components work together to achieve microsecond-level protection.

[0070] Current-limiting resistors are used to limit the maximum short-circuit current in high-voltage circuits to prevent irreversible damage to the high-voltage circuits caused by large current surges.

[0071] Current-limiting inductors can suppress sudden current changes in high-voltage circuits and clamp the output voltage of high-voltage power supplies to prevent abnormal voltage changes when output short circuits or overcurrent faults occur.

[0072] When a short circuit or overcurrent fault occurs at the load end of the high-voltage power supply, the fast protection circuit can quickly drive the protection high-voltage switch (U1) to close, releasing the electrical energy stored in the high-voltage circuit, thereby achieving microsecond-level fast protection and ensuring the safety of the high-voltage circuit and related devices.

[0073] Current-limiting resistor design:

[0074] The current-limiting resistors (R1, R2, R3, R5, R6) are selected from RYGDL high-power, high-voltage, non-inductive resistors, with a rated power of 500W, a limiting voltage of 60kV, and a resistance of 100Ω. Considering the maximum short-circuit current (the high-voltage power supply can withstand a maximum current of 1kA for a short time) and the heat generated by the current-limiting resistors, five resistors are selected for use in parallel, with an equivalent resistance of 20Ω.

[0075] Current-limiting inductor design

[0076] The current-limiting inductor (L2) limits the rate of current ramp-up, giving the high-voltage switch time to cut off the main circuit power supply in a timely manner.

[0077] A simulation model is established with a maximum bus voltage of 20kV, such as Figure 13 As shown.

[0078] Simulation results are as follows Figure 14 , 15 As shown in Figures 16 and 17, the results are summarized in the following table:

[0079]

[0080] Taking into account the protection circuit's operating time (5–10 μs), the high-voltage switch's operating time (15–50 μs), and the high-voltage switch's maximum breaking current margin (maximum 200A breaking capacity, taken as 50%), the inductance of the current-limiting inductor should be no less than 30 mH. To ensure the safety and reliability of the high-voltage switch and its actual operating conditions, the inductance of the current-limiting inductor is set to 50 mH. The current-limiting inductor (L2) is designed with an inductance of 50 mH, a rated current of 10 A, a maximum voltage of 25 kV, and an insulation withstand voltage class of 30 kV.

[0081] High-voltage switch design:

[0082] Figure 1 The medium-high voltage switch (U1) is a custom-designed switch, powered by 24V, composed of multiple MOSFETs connected in series and parallel, and connected in series in the negative high-voltage loop of the main circuit. The switch's peak on-state current is 10A, peak off-state current is 200A, peak forward off-state voltage is 20kV, peak reverse off-state voltage is 24kV, insulation withstand voltage is 30kV, and both positive and negative pole withstand voltages are 30kV. It is controlled by fiber optic cable. The minimum on-state time (Ton) is 10μs, and the minimum off-state time (Toff) is 10μs.

[0083] The selected MOSFET is a P3M12017K4 with a drain-source voltage (Vdss) of 1.2kV, a continuous drain current (Id) of 154A, a pulsed drain current (Id-pulse) of 270A, and a power dissipation (Pd) of 789W. The turn-on delay (Td-on) is 19ns, the rise time (Tr) is 62ns, the turn-off delay (Td-off) is 78ns, and the fall time (Tf) is 30ns.

[0084] Figure 12 The medium-high voltage switch (U3) is a custom-designed switch, powered by 220V AC, and consists of six IGCTs connected in series. The switch's peak on-state current is 10A, peak off-state current is 3kA, peak forward off-state voltage is 20kV, peak reverse off-state voltage is 24kV, insulation withstand voltage is 30kV, and positive and negative withstand voltage is 24kV. Control is via fiber optic communication. Minimum on-state time (Ton) = 40μs, minimum off-state time (Toff) = 40μs.

[0085] The IGCT device model is CAc4000-45-02, with a rated DC voltage of 4000V, a maximum shutdown current of 3800A, a surge current of 27kA@10ms, a turn-on delay (Tdon) of less than 3μs, and a turn-on feedback delay (TdonSF) of less than 7μs.

[0086] Current sampling Hall effect design:

[0087] The maximum operating current of the 20kV klystron load is 10A. When designing short-circuit protection for the klystron load, the maximum interrupting current should not exceed 200A. A current sampling Hall effect sensor (U2) with a rated current of 100A and a maximum measurement range of 150A is selected. The LEM LT108-S7 current sensor is chosen, with a conversion rate Kn of 1:2000, total accuracy not exceeding 0.6%, linearity less than 0.1%, response time (Tra) less than 500ns, response time (Tr) less than 1μs, and tracking accuracy (di / dt) greater than 100A / 1μs.

[0088] Cooling fan design:

[0089] The cooling fan mainly uses current-limiting resistors and current-limiting inductors for heat dissipation.

[0090] According to the power consumption formula calculate:

[0091] The power consumption of the current-limiting resistor when it is working is P1==10×10×20=2000W.

[0092] The power consumption of the current-limiting inductor is approximately

[0093] The current-limiting inductor operates in a pure DC circuit, carrying only DC current, with no AC ripple or alternating magnetic field, and its iron loss is negligible. Therefore, P2≈PCu=I^2×R=5×5×0.8=20W.

[0094] Ptotal = P1 + P2 = 2020W.

[0095] According to the formula for calculating forced air cooling volume calculate:

[0096] The specific heat capacity of air at constant pressure is approximately 1005 J / (kg×K).

[0097] Air density ρ≈1.2kg / ;

[0098] Remove the air vent; the temperature rise is 15K.

[0099] Q=2020 / (1005×1.2×15)=0.1117 / min≈236.6CFM;

[0100] To ensure a temperature rise of ≤50K under 2020W power loss, a fan with an airflow of not less than 300CFM should be selected.

[0101] Considering other heat-generating components within the device, as well as the device dimensions and airflow, a certain margin needs to be allowed when selecting fan airflow. Two cooling fans, SF1806HA2, are selected, powered by AC 220V, with a rated current of 0.2A, a rated speed of 2850RPM, and an airflow of 400FM.

[0102] Fiber optic transceiver design:

[0103] Considering its application in high-voltage environments, the HFBR series ST threaded port optical receiver was selected. It features strong electrical isolation, high EMI / RFI immunity, making it suitable for scenarios with strong electromagnetic interference. With a data rate of 5MBd and a maximum link length of 2km, it meets the requirements for low-speed, long-distance industrial communication.

[0104] The receiving fiber is selected as HFBR-2412TZ, and the transmitting fiber is selected as HFBR-1412TZ. For example... Figure 2 , Figure 3 As shown, the device has four receiving optical heads for high-voltage switch closing, bleeder relay opening, reset, and fault triggering; and five transmitting optical heads for bleeder relay status feedback, voltage sampling signal, voltage short-circuit feedback, current sampling signal, and overcurrent blocking drive. The sampling control board has three receiving optical heads for bleeder relay opening, fault reset, and fault triggering; and six transmitting optical heads for bleeder relay status feedback, voltage sampling signal, voltage short-circuit triggering, voltage short-circuit feedback, current sampling signal, and overcurrent blocking drive.

[0105] Auxiliary power supply board design:

[0106] like Figure 4 As shown, the input 220V AC voltage is processed by a fuse (F1), a varistor (R16), and an EMI filter circuit (C9, C12, FIL1, C10) to obtain a clean AC input. This AC voltage is output in three ways: one way supplies the cooling fan control relay, and the other two ways are input to two AC / DC power modules respectively, ultimately outputting three working power supplies. The selection of each power module and key component is as follows:

[0107] The coil resistance of the discharge relay is approximately 120Ω. The matching power supply module (U7) is model LD30-26B24R2, with an output specification of 24V / 1.210A, which can meet the working requirements of the discharge relay.

[0108] The control board is designed to have a power of approximately 10W. The matching power module (U8) is model TAD30-15-W, with an output specification of ±15V / 1A, which can meet the power supply requirements of the control board.

[0109] The specifications of a single cooling fan are AC 220V / 0.2A. Combined with the maximum power consumption of power modules (U7) and (U8) calculated at 45W, in order to ensure circuit safety and reserve sufficient margin, the fuse (F1) is selected as model SST1200. This fuse is a slow-blow type with a rated current of 3A and a rated voltage of AC300V, which can effectively protect the entire power input circuit.

[0110] Sampling control board design:

[0111] The sampling control board integrates cooling fan control, reset circuit and discharge relay control, and has current sampling, overcurrent protection, voltage sampling, short circuit protection and external triggering functions.

[0112] Cooling fan start / stop circuit design:

[0113] like Figure 5 As shown, the cooling fan start / stop control circuit includes two redundant control loops. One loop uses a thermistor to collect temperature signals; when the detected temperature exceeds 40℃, the cooling fan starts. The other loop controls the operation through the main circuit current; when the main circuit current exceeds 1A, the cooling fan starts. These two control loops are redundant, ensuring reliable control of the cooling fan.

[0114] The cooling fan is AC 220V / 0.22A. The relay selected is a power relay G6B-2214P-USDC24 with a coil voltage of 24V, a contact capacity (resistive load) of 10A@250VAC, and two sets of normally open contacts.

[0115] Reset circuit design:

[0116] like Figure 6 As shown, the reset circuit includes two reset mechanisms: after the device is powered on, it performs a self-reset to restore the device to normal working state; after the device fails, the reset signal receiving optical head (FC19) receives an external reset signal (optical reset) to achieve reset and recovery.

[0117] Design of the discharge relay control circuit:

[0118] like Figure 7 As shown, when the device is in standby mode, the discharge relay is closed, clamping the circuit voltage within a safe range, and the relay status feedback transmitting optical head (FC20) maintains a light-emitting state. When the device is working, after the relay-controlled receiving optical head (FC21) receives an external light signal, the discharge relay coil is supplied with 24V voltage and disconnected, and its feedback circuit operates synchronously, switching the relay status feedback transmitting optical head (FC20) from a light-emitting state to a light-free state.

[0119] Current sampling circuit design:

[0120] like Figure 8As shown, the IF+ signal acquired by the current sampling Hall effect sensor (U2) is amplified 20 times to obtain signal IFC1. This signal is then filtered and input to a V / F converter, which converts the voltage signal into a frequency signal (conversion ratio of 1A:1kHz), and transmits it externally through the current sampling transmitter (FC22). Simultaneously, signal IFC1 provides a set threshold for the overcurrent protection circuit.

[0121] Overcurrent protection circuit design:

[0122] The maximum operating current of the 20kV klystron load is 10A, and the overcurrent protection circuit is set to an overcurrent threshold of 6A. When the detected current exceeds 10A, it is determined that the klystron load is short-circuited.

[0123] like Figure 9 As shown, the overcurrent protection circuit includes two protection modes: one is conventional overcurrent protection, which is for overcurrent conditions with current exceeding 6A; the other is klystron load short-circuit protection, which is for short-circuit conditions with current exceeding 10A. This short-circuit protection and voltage short-circuit protection form redundant protection, which can effectively improve protection reliability.

[0124] When the device is working normally, the overcurrent transmitting optical head (FC24) maintains the state of transmitting light externally; when the device experiences an overcurrent or klystron load short circuit fault, the overcurrent transmitting optical head (FC24) switches from the light-emitting state to the non-light-emitting state.

[0125] Voltage sampling circuit design:

[0126] like Figure 10 As shown, the negative voltage signal VF1 acquired by the voltage sampling resistor (RS1) at the device's input terminal is converted into a positive voltage signal VFC1 after being inverted by the operational amplifier (U14). This signal is then filtered and input to the V / F converter, which converts the voltage signal into a frequency signal (conversion ratio of 1kV:1kHz), and transmits it externally through the voltage sampling and transmitting optical head (FC23). Simultaneously, the voltage signal VFC1 provides a set threshold for the voltage short-circuit protection circuit.

[0127] The negative voltage signal VF2 collected by the voltage sampling resistor (RS2) at the output terminal of the device is converted into a positive voltage signal VFC2 after being inverted by the operational amplifier (U16). This signal provides a set threshold for the voltage short circuit protection circuit.

[0128] In addition, the negative voltage signal acquired by the device's input / output terminals can also be reversed and converted into a positive voltage signal by the AD8066 chip, serving as a backup reverse processing solution.

[0129] Voltage short-circuit protection circuit design:

[0130] The design principle of voltage short-circuit protection is as follows: During normal operation, the input and output terminals of the device acquire the bus voltage in real time through voltage sampling resistors, achieving real-time monitoring of the bus voltage. When a short-circuit fault occurs at the output of the device, the bus voltage acquired at the output terminal will drop instantaneously to approximately 0V. However, due to the presence of the current-limiting inductor in the main circuit, at the moment of the output short circuit, the current-limiting inductor will clamp the output voltage of the high-voltage power supply, causing the bus voltage acquired at the input terminal to decrease slowly before the current-limiting inductor saturates. Utilizing this characteristic of the difference in the rate of drop of the input / output bus voltage, microsecond-level rapid short-circuit protection can be achieved, promptly cutting off the faulty circuit and ensuring the safety of the device.

[0131] like Figure 11 As shown, after filtering, voltage signal VFC1 is divided by two 5.1kΩ resistors to obtain a signal with half the voltage value of VFC1; after filtering, voltage signal VFC2 is divided by a 1kΩ resistor and a 20kΩ resistor to obtain a signal approximately equal to voltage signal VFC2.

[0132] Voltage signal VFC1 (after voltage division) and voltage signal VFC2 are input to comparator (U23) for processing. The comparator output signal is processed and then sent to latch (K4). The latch outputs two opposite voltage signals, Q and nQ.

[0133] When the device is working normally, the comparator (U23) continuously outputs a high level. At this time, the latch (K4) outputs a low level at the Q terminal and a high level at the nQ terminal. The voltage status feedback transmitting optical head (FC26) maintains the state of transmitting light externally, and the fault-triggered transmitting optical head (FC27) maintains the state of no light.

[0134] When a short circuit fault occurs at the device output, the comparator (U23) output quickly switches from high level to low level. At this time, the latch (K4) outputs a high level at the Q terminal and a low level at the nQ terminal. The voltage status feedback transmitting optical head (FC26) switches to the no-light state, and the fault-triggered transmitting optical head (FC27) switches to the external transmitting light state.

[0135] To prevent malfunction of the voltage short-circuit protection circuit during the operation and voltage boosting phase of the device, and considering the high-voltage switch's withstand capability (rated withstand current of 100A) and the main circuit current-limiting resistor parameters (resistance of 20Ω), a malfunction prevention protection circuit is specifically designed: when the output voltage is less than 2kV, the voltage short-circuit protection circuit will not operate and will not respond to any short-circuit signal. Under this condition, if an output voltage short-circuit fault occurs, the overcurrent protection circuit will perform the protection operation to ensure the safety of the device and related components.

[0136] Fault trigger signal circuit design:

[0137] In addition to the built-in protection functions of the device, an external fault signal receiving and fast protection function needs to be set up to deal with scenarios where high-voltage power supply or other critical parts fail: when high-voltage power supply or other critical parts fail, the fault trigger receiving optical head (FC25) can receive externally sent fault signals in real time.

[0138] like Figure 11 As shown, after the fault-triggered receiving optical head (FC25) receives an external fault signal, it processes the signal and sends it directly to the latch (K4). This protection path is not limited by the anti-maloperation protection circuit, and can directly trigger and execute fast protection operation to cut off the fault circuit in time and ensure the safety of the device.

[0139] Device structural outline design:

[0140] Considering the impact of external electromagnetic interference on the device's operational stability, this invention employs a fully enclosed metal casing. The area inside the casing near the exposed negative high-voltage electrical point requires an epoxy board for insulation protection. Both the auxiliary power board and the sampling control board are installed inside this fully enclosed metal casing, positioned near the edge of the casing on the device side. Ventilation holes are provided at the corresponding board mounting locations on the casing to ensure adequate heat dissipation. External power connections are achieved via wires, while external communication is transmitted via optical fiber. Voltage / current sampling signals are connected via coaxial cables, further enhancing electromagnetic interference immunity.

[0141] The design drawings related to this invention are simplified and can be optimized and adjusted according to different operating conditions. By changing the specifications of related components such as the main circuit filter circuit, voltage sampling resistor, current sampling Hall effect sensor, current limiting resistor, current limiting inductor, and high-voltage switch, the device can be adapted to operate with high-voltage power supplies with bus voltages from 10kV to 40kV.

[0142] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A DC high-voltage output short-circuit protection device suitable for PCS, characterized in that, include: The input / output interface terminal is provided with an input interface that connects to a 20kV DC high voltage and a 220V AC auxiliary power supply, and an output interface that outputs a 20kV DC high voltage. The filter circuit is connected to the high-voltage main circuit and is used to filter out high-frequency noise. Input / output sampling resistors are connected in parallel to the input and output terminals of the high-voltage main circuit, respectively, to collect input and output voltage signals. The discharge circuit, connected to the high-voltage main circuit, is normally closed and open during shutdown to release residual electrical energy; A fast protection circuit, connected in series in the high-voltage main circuit, is used to limit the peak current and disconnect the high-voltage switch within microseconds to cut off the power supply to the main circuit when the load is short-circuited. A current sampling Hall effect sensor is connected in series in the high-voltage main circuit to collect the circuit current signal in real time. Cooling fans are used to dissipate heat from heat-generating components. Fiber optic transceivers are used to receive external control signals and provide feedback on status and sampled signals. Auxiliary power supply board, used to provide multiple DC and AC power supplies; The sampling control board is used to implement overall logic and protection control, including discharge relay on / off control, cooling fan start / stop control, signal acquisition and short-circuit fast protection; The chassis structure components adopt a composite design with an inner and outer layer. The inner layer is covered with an insulating epoxy board, and the outer layer is made of a metal shielding plate.

2. The DC high-voltage output short-circuit protection device for PCS according to claim 1, characterized in that, The fast protection circuit includes a current-limiting resistor, a current-limiting inductor, and a protective high-voltage switch; the current-limiting inductor is used to suppress sudden current changes and buy time for the high-voltage switch to cut off the power supply, and the protective high-voltage switch is used to close or open in the event of a short circuit to discharge energy or cut off the circuit.

3. The DC high-voltage output short-circuit protection device for PCS according to claim 2, characterized in that, The current-limiting resistor is composed of multiple high-voltage non-inductive resistors connected in parallel, with an equivalent resistance of 20Ω, and is used to limit the maximum short-circuit current in the high-voltage circuit; the current-limiting inductor has an inductance of not less than 30mH, a rated current of 10A, and an insulation withstand voltage rating of 30kV.

4. The DC high-voltage output short-circuit protection device for PCS according to claim 1, characterized in that, The sampling control board includes a voltage short-circuit protection circuit. This circuit determines short-circuit faults by acquiring the voltage signals at the input and output terminals of the high-voltage main circuit, respectively, and using the difference in voltage drop rates between the output and input terminals.

5. The DC high-voltage output short-circuit protection device for PCS according to claim 4, characterized in that, The voltage short-circuit protection circuit also includes a protection circuit to prevent malfunctions.

6. The DC high-voltage output short-circuit protection device for PCS according to claim 1, characterized in that, The sampling control board also includes an overcurrent protection circuit, which has a conventional overcurrent threshold and a short-circuit overcurrent threshold. When the detected current exceeds the conventional overcurrent threshold, conventional overcurrent protection is performed, and when the detected current exceeds the short-circuit overcurrent threshold, short-circuit protection is performed. It also forms redundant protection with the voltage short-circuit protection.

7. The DC high-voltage output short-circuit protection device for PCS according to claim 1, characterized in that, The discharge circuit includes a high-voltage relay and a discharge resistor. The high-voltage relay is normally closed and open when the high-voltage power supply is shut down, and the discharge resistor is connected to release the residual electrical energy in the energy storage element, so that the circuit voltage drops rapidly to a safe range.

8. The DC high-voltage output short-circuit protection device for PCS according to claim 1, characterized in that, The external control signals received by the fiber optic transceiver include the discharge relay disconnect signal, the high-voltage switch closing signal, and the reset signal; the feedback signals include the discharge relay status, voltage / current acquisition signals, and voltage / current fault protection signals.

9. The DC high-voltage output short-circuit protection device for PCS according to claim 1, characterized in that, The cooling fan is controlled by a sampling control board. The sampling control board controls the start and stop of the cooling fan by detecting temperature signals and / or main circuit current signals through a thermistor. The cooling fan is started when the temperature is higher than 40°C or the current is greater than 1A.

10. The DC high-voltage output short-circuit protection device for PCS according to claim 1, characterized in that, In the aforementioned chassis structure components, the sampling control board adopts an all-metal enclosed shell to resist high electric field interference and strong electromagnetic field impact generated during load short circuit; the input / output interface terminals adopt high-voltage connectors with a rated voltage of not less than 30kV.

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