High-power variable-frequency power supply device with overvoltage protection
By designing a high-power variable frequency power supply device with overvoltage protection in the variable frequency resonant high voltage test system, and utilizing the protection control board to promptly discharge the bridge arm, the problem of IGBT damage caused by resonant reactor failure was solved, thus enhancing circuit safety.
Patent Information
- Application Number
- CN202423300257.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-31
- Publication Date
- 2025-12-09
- Estimated Expiration
- 2034-12-31
AI Technical Summary
In existing variable frequency resonant high voltage test systems, when the resonant reactor fails and breaks down, the voltage at the output port of the variable frequency power supply rises, causing damage to the IGBTs in the inverter bridge and posing a circuit safety hazard.
Design a high-power frequency converter with overvoltage protection, comprising a frequency converter module, an IGBT-based discharge bridge arm, a protection circuit, a protection control board, an excitation transformer, and a reactor. The protection control board collects voltage changes and controls the discharge bridge arm to discharge in a timely manner, protecting the IGBT and the circuit safety.
When the resonant reactor fails, it effectively prevents the voltage at the output terminal of the frequency converter from continuously rising, protects the inverter bridge IGBT, enhances circuit safety, and avoids damage.
Smart Images
Figure CN223652146U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to a variable frequency resonant high voltage test device, specifically to a high-power variable frequency power supply device with overvoltage protection. Background Technology
[0002] The variable frequency resonant high voltage test system is a specialized device for testing the insulation performance of power equipment. It is mainly used to evaluate the withstand voltage and stability of high voltage electrical equipment such as transformers, cables, and switchgear under high voltage conditions. It achieves resonance with the capacitor of the test object by adjusting the frequency, thereby effectively generating the required high voltage.
[0003] like Figure 1 The diagram shows a schematic of a variable frequency resonant high-voltage test system, mainly including a transformer T, a high-power variable frequency power supply VF, a resonant reactor L, and a capacitive voltage divider. In this system, the capacitive voltage divider is the test object (DUT), which can consist of a capacitor Cx and series capacitors C1 and C2 connected in parallel across Cx. The DUT is grounded, which is also the system ground. The variable frequency power supply VF receives the power input, performs voltage frequency conversion, and simultaneously provides protective grounding. The converted output is then sent to terminals a and x on the high-voltage side of transformer T, and further output through terminals A and X on the low-voltage side. A MOAI overvoltage protection surge arrester can also be connected in parallel on the low-voltage side for lightning protection. Terminals a and A are the starting terminals, and terminals x and X are the ending terminals. The resonant reactor L and the DUT form an LC circuit. The DUT is excited by the variable frequency power supply VF via transformer T. After frequency modulation, the LC circuit reaches resonance, generating a high voltage on the DUT. In the resonant state, the LC circuit is equivalent to an energy storage system. When the resonant reactor L fails and breaks down, the energy stored in the capacitor of the test object will backflush to the frequency converter VF through the excitation transformer, causing the output port voltage of the frequency converter VF to rise and damaging various circuit devices set between the frequency converter and the excitation transformer, such as IGBTs in the inverter bridge, with serious consequences. Utility Model Content
[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a high-power frequency converter with overvoltage protection. When the reactor fails and breaks down, it can provide overvoltage protection, ensuring that the IGBTs in the inverter bridge at the output of the frequency converter module are not damaged, while also enhancing circuit safety.
[0005] The technical solution adopted in this utility model is as follows:
[0006] A high-power frequency converter with overvoltage protection includes a frequency converter module, an IGBT-based bleeder arm, a protection circuit, a protection control board, an excitation transformer, a reactor, and a test capacitor. The two output terminals of the frequency converter module are respectively connected to the two ends of the high-voltage winding of the excitation transformer. The two ends of the low-voltage winding of the excitation transformer form a low-voltage side circuit through a series reactor and a test capacitor. The protection control board is connected to the bleeder arm and also connected to the two output terminals of the frequency converter module through the two ends of a built-in isolation transformer. The protection circuit is located between the two ends of the isolation transformer and includes two surge protectors connected in series. The bleeder arm is located between the two output terminals of the frequency converter module.
[0007] The protection circuit can safely and reliably acquire the voltage changes at the two output terminals of the inverter module. When the voltage rises, this voltage change is transmitted to the protection control board for judgment. When it is determined that voltage needs to be discharged, the discharge bridge arm is activated, thereby reducing the voltage at the two output terminals of the inverter module and protecting the IGBTs in the discharge bridge arm.
[0008] Preferably, the discharge arm is an inverter IGBT arm, including IGBT1 and IGBT2. Corresponding anti-parallel diodes are connected between the collector and emitter of both IGBT1 and IGBT2, and the gates of both IGBT1 and IGBT2 are connected to a protection control board. The inverter IGBT arm can quickly turn on and off, thus promptly handling overvoltage situations.
[0009] Preferably, the two surge protectors connected in series in the protection circuit are grounded, and both ends of the two surge protectors are connected to the two ends of the isolation transformer. This connection method of the two surge protectors facilitates the acquisition of voltage fluctuation values, which are then transmitted to the protection control board 3 to determine whether to use the discharge bridge arm for discharge.
[0010] Preferably, the protection control board includes a drive control circuit, an isolation transformer, a judgment circuit, a feedback circuit, and a power supply module. The input of the judgment circuit is connected to the isolation transformer, and its output is connected to the drive control circuit via the feedback circuit. The drive control circuit is connected to the discharge bridge arm, and the power supply module is connected to both the drive control circuit and the feedback circuit. In the protection control board, the feedback circuit can effectively obtain the judgment result from the judgment circuit, thus enabling the drive control circuit to promptly activate the discharge bridge arm for discharge in the event of overvoltage.
[0011] Preferably, the drive control circuit includes at least a drive chip U1; the drive chip U1 is connected in sequence to the collector, gate, and emitter of any IGBT in the discharge bridge arm through diode D1, resistor R1, and resistor R2, respectively. The drive chip U1 allows for effective and rapid control of the discharge bridge arm.
[0012] Preferably, the judgment circuit includes a resistor R6, a sliding rheostat PR1, a diode D3, a bidirectional trigger diode DW1, a capacitor C4, and a transistor Q1. The base of transistor Q1 is connected to the inverting input terminal of diode D3 through the bidirectional trigger diode DW1. The non-inverting input terminal of diode D3 is connected to resistor R6. The sliding terminal and fixed terminal 1 of the sliding rheostat PR1 are connected in parallel between resistor R6 and diode D3. The fixed terminal 2 of the sliding rheostat PR1 is connected in parallel between the bidirectional trigger diode DW1 and the base of transistor Q1 through capacitor C4. The collector and emitter of transistor Q1 are connected to the feedback circuit. The judgment circuit can quickly determine the voltage fluctuations caused by changes in the voltage at the two output terminals of the frequency converter module, and then pass the feedback to transistor Q1.
[0013] Preferably, the feedback circuit includes a first feedback unit based on an optocoupler and a second feedback unit for forming a feedback loop; wherein, the first feedback unit includes a resistor R3, a resistor R4, an optocoupler OP1, an optocoupler OP2, an LED1, and an LED2; the first end of the optocoupler OP1 is connected to the collector of the transistor Q1 through the resistor R4, and the second end of the optocoupler OP1 is connected to the power supply module through the LED2; the first end of the optocoupler OP2 is connected to the drive control circuit through the resistor R3, and the second end of the optocoupler OP2 is connected to the power supply module through the LED1; the second feedback unit includes a silicon controlled rectifier (SCR1), a resistor R5, and a first RC voltage regulator circuit; the anode of the SCR1 is connected to the emitter of the transistor Q1, the cathode of the SCR1 is connected in parallel to the anode through the first RC voltage regulator circuit, the gate of the SCR1 is connected to the power supply module through the resistor R5, and the drive control circuit is also connected in parallel between the cathode of the SCR1 and the resistor R5. The first feedback unit can quickly provide light prompts based on optocouplers, while the second feedback unit uses a silicon controlled rectifier (SCR1) to complete signal transmission with the drive control circuit, providing a stable start signal for the drive control circuit.
[0014] Preferably, the power supply module includes at least two voltage pins and two current pins. The power supply module utilizes multiple pins to efficiently operate various circuits.
[0015] Beneficial effects: After installing this utility model module in a large-capacity frequency converter power supply, when the voltage at the output port of the frequency converter power supply rises due to a fault in the resonant reactor, the module is turned on to prevent the voltage at the output port of the frequency converter power supply from continuing to rise and causing the inverter bridge IGBT to be damaged by overvoltage. Attached Figure Description
[0016] Figure 1 This is a schematic diagram of a variable frequency resonant high voltage test system;
[0017] Figure 2This is a system schematic diagram of a high-power frequency converter with overvoltage protection.
[0018] Figure 3 This is a control principle diagram of the protection control board in a high-power frequency converter with overvoltage protection. Detailed Implementation
[0019] The present invention will be further explained below with reference to the accompanying drawings and specific embodiments. These embodiments are implemented under the premise of the technical solution of the present invention. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention.
[0020] like Figure 2 The diagram shown is a system schematic of a high-power frequency converter with overvoltage protection. This is a high-voltage frequency converter with discharge protection capability, including a frequency converter module, an IGBT-based discharge bridge arm, a surge protector-based protection circuit, a protection control board, an excitation transformer, a reactor, and a test capacitor. Under the protection of the protection circuit, the protection control board can collect the voltage change at the output terminal of the frequency converter module, and then control the discharge bridge arm to discharge when a specific threshold is met, thereby effectively protecting each component.
[0021] In this embodiment, the two output terminals of the frequency converter module are respectively connected to the two ends of the high-voltage side winding of the excitation transformer, forming a high-voltage side circuit. The two ends of the low-voltage side winding of the excitation transformer form a low-voltage side circuit through a series reactor and a test capacitor, with the test capacitor grounded. The excitation transformer can convert the voltage output by the frequency converter module into a low voltage for the low-voltage side circuit. However, when the reactor experiences a breakdown or other fault, the voltage at the output terminal of the frequency converter module will still rise, which may damage the IGBT in the bleeder arm and may also cause safety hazards in the high-voltage side circuit. Therefore, the bleeder arm is placed between the two output terminals of the frequency converter module, and a protection control board is used to connect the bleeder arm for timely bleed control. At the same time, the two ends of the built-in isolation transformer are connected to the two output terminals of the frequency converter module to collect voltage fluctuation signals. The protection circuit is set between the two ends of the isolation transformer for protection. When the voltage at the two output terminals of the frequency converter module rises, and the signal collected by the control protection board meets a specific threshold, the two output terminals of the frequency converter module can be short-circuited in time through the discharge bridge arm to discharge the excess energy, thereby protecting the safety of the entire device and the IGBT.
[0022] In this embodiment, the discharge arm is an inverter IGBT arm, meaning two IGBTs are connected in reverse to improve voltage withstand capability. The two IGBTs are IGBT1 and IGBT2. Corresponding anti-parallel diodes are connected between the collector and emitter of both IGBT1 and IGBT2. The gates of both IGBT1 and IGBT2 are connected to the protection control board, thus receiving control from the protection control board. The inverter IGBT arm can quickly turn on and off, thereby promptly handling overvoltage situations and dissipating excess energy. The rated voltage and rated current of the discharge arm can be 1200V and 600A, respectively, and the rated voltage of each surge protector can be 820V.
[0023] In this embodiment, the protection circuit includes two surge protectors connected in series, grounded between them. Both ends of the two surge protectors are connected to the two input terminals of an isolation transformer. Both surge protectors can be SP100 surge protectors. Their connection method facilitates safe voltage transformation by the isolation transformer, allowing the judgment circuit to safely collect voltage fluctuation values.
[0024] like Figure 3 The diagram shown is a control principle diagram of the protection control board in a high-power frequency converter with overvoltage protection. Figure 3 The diagram shows the circuit for connecting any one of the IGBTs in the discharge bridge arm. Besides using the aforementioned method of connecting the gates of two IGBTs respectively with the driver chip U1, the protection control board can also use... Figure 3 The circuit shown connects the driver chip U1 to each IGBT.
[0025] The protection control board includes a drive control circuit using a driver chip U1, an isolation transformer, a judgment circuit, a feedback circuit, and a power supply module JP1. The driver chip U1 can be a QP12W08S-37 chip, the isolation transformer can be a MARCUS transformer 3083 series, and the power supply module JP1 can be a PWR8300 programmable DC power supply.
[0026] The input of the judgment circuit receives the output after the isolation transformer has transformed the voltage, which means it collects the voltage fluctuation signals at the two output terminals of the frequency converter module. This allows the diode D3 in the judgment circuit to provide sufficient base voltage to transistor Q1 for rapid conduction when the voltage fluctuation reaches a specific threshold built into diode D3. This enables transistor Q1 to provide the turn-on status signal to optocoupler OP1 and SCR1 in a timely manner. Transistor Q1 can be a 2SC2383 model. The output of the judgment circuit is connected to the drive control circuit through a feedback circuit. The drive chip U1 in the drive control circuit is connected to each IGBT in the bleeder bridge arm in the same sampling manner. The power supply module JP1 is connected to both the drive control circuit and the feedback circuit.
[0027] The driver chip U1 has a 100uF capacitor C7 with a rated voltage of 35V between the drain (D) and emitter (E) terminals of the IGBT power semiconductor device in the discharge bridge arm, which can better protect the IGBT operation. The drain (D) of the IGBT is the collector, the emitter (E) is the emitter, and the gate (G) is the gate. The driver chip U1 receives DC +15V power from the power supply module JP1. The driver chip U1 is grounded, and a polarized capacitor C1 is also set between the ground terminal and the power supply terminal for voltage regulation and filtering. The specifications of the polarized capacitor C1 are not limited and can be selected at will, but the polarity must be correct, with the negative terminal grounded.
[0028] In this embodiment, the drive control circuit includes at least a drive chip U1. The drive chip U1 is connected sequentially to the collector, gate, and emitter of any IGBT in the discharge bridge arm via diode D1, resistor R1, and resistor R2, respectively, enabling effective rapid start-stop control of the discharge bridge arm. The drive chip U1 is also connected in parallel with a 30V Zener diode D2 at the forward input terminal of diode D1 to provide a stable reference voltage. Simultaneously, a polarized capacitor C3 is connected between the forward input terminal of Zener diode D2 and resistor R2 and the drive chip U1, also to provide a stable reference voltage. The polarized capacitor C3 is 100uF with a rated voltage of 35V. In addition, a polarized capacitor C2 is connected in parallel between resistor R2 and driver chip U1 through resistor R3 and driver chip U1 to provide a stable reference voltage. The polarized capacitors C2 and C3 have the same specifications. Resistor R1 has a rated power of 4.7KΩ and 2W, resistor R2 has a rated power of 0.5KΩ and 2W, and resistor R3 has a rated power of 4.7KΩ and 2W.
[0029] In this embodiment, the judgment circuit essentially samples the voltage signal transmitted by the protection circuit. When the sampled signal reaches a specific threshold for diode D3 to conduct, the feedback circuit triggers the drive control circuit to open the discharge. Specifically, the judgment circuit includes resistor R6, variable resistor PR1, diode D3, bidirectional trigger diode DW1, capacitor C4, and transistor Q1. Resistor R6 is 100KΩ with a rated power of 5W. The variable resistor PR1 has a rated resistance of 100KΩ and a rated power of 5W. Diode D3 is an IN4148. The bidirectional trigger diode DW1 has a forward voltage of 5.1V. Capacitor C4 is 104uF. Transistor Q1 is a 2SC2383. The base of transistor Q1 is connected to the inverting input of diode D3 via bidirectional trigger diode DW1. The non-inverting input of diode D3 is connected to resistor R6. A sliding rheostat PR1 is connected in parallel between the sliding terminal and fixed terminal 1 between resistor R6 and diode D3. The fixed terminal 2 of rheostat PR1 is connected in parallel between bidirectional trigger diode DW1 and the base of transistor Q1 via capacitor C4. The collector and emitter of transistor Q1 are both connected to the feedback circuit. The judgment circuit can quickly determine the voltage fluctuation caused by the voltage change at the two output terminals of the frequency converter module, and then pass the feedback to transistor Q1.
[0030] A second RC voltage regulator circuit is connected in parallel at the forward output terminal of the bidirectional trigger diode DW1, including a capacitor C5 and a resistor R8. Capacitor C5 has a rated voltage of 220uF and 25V, while resistor R8 has a rated power of 1KΩ and 0.5W. This second RC voltage regulator circuit is used to protect the signal stability of the judgment circuit. Simultaneously, a resistor R7 is connected in parallel at the forward input terminal of diode D3 to suppress transient currents, thereby protecting the circuit. Resistor R7 has a rated power of 1KΩ and 0.5W.
[0031] In this embodiment, the feedback circuit includes a first feedback unit based on an optocoupler and a second feedback unit for forming a feedback loop. The first feedback unit includes resistors R3 and R4, optocoupler OP1, optocoupler OP2, LED1, and LED2. The first terminal of optocoupler OP1 is connected to the collector of transistor Q1 via resistor R4 (1kΩ for current limiting protection). The second terminal of optocoupler OP1 is connected to the power supply module JP1 via LED2. The first terminal of optocoupler OP2 is connected to the drive control circuit via resistor R3. The second terminal is connected to the power supply module JP1 via LED1. The second feedback unit includes a silicon controlled rectifier (SCR1), a resistor R5, and a first RC voltage regulator circuit. The anode of the SCR1 is connected to the emitter of transistor Q1, the cathode of the SCR1 is connected in parallel to the anode through the first RC voltage regulator circuit, and the gate of the SCR1 is connected to the power supply module JP1 through resistor R5. The cathode of the SCR1 and resistor R5 are also connected in parallel to the drive control circuit through a KQ-M14 node for control. Resistor R5 is 2KΩ. The first feedback unit can quickly provide light prompts based on the optocoupler, while the second feedback unit uses the SCR1 to complete signal transmission with the drive control circuit, providing a stable start signal for the drive control circuit. The specific model of the SCR1 can be a 2N5060 SCR or a BT169G SCR. Specifically, both optocouplers can be PL-521 type optocouplers. The first RC circuit includes a resistor R9 and a capacitor C6 connected in parallel. The resistor R9 has a rated power of 1KΩ and 0.5W, and the capacitor C6 has a rated power of 0.01F.
[0032] It should be noted that an optocoupler is a device for achieving electrical isolation. Optocouplers OP1 and OP2 have the same internal structure, each consisting of an LED and a photodiode. The LED and photodiode use standard dual-in-line packages. In optocoupler OP1, the LED's positive input receives a DC +15V power supply from power module JP1, and its positive output is connected to the collector of transistor Q1 via resistor R4. The photodiode in OP1 is connected to the current pin of power module JP1 via LED2, thus converting the light signal between LED2 and the LED in OP1. Optocoupler OP2 works similarly. The two ends of the LED in OP2 are connected to driver chip U1, receiving control from U1. When driver chip U1 needs to control the discharge bridge arm for discharge, the LED in OP2 emits light, the photodiode in OP2 receives this light signal, and then LED1 emits as feedback.
[0033] In this embodiment, the power supply module JP1 includes at least two voltage pins and two current pins. The two voltage pins are both DC+15V, used to power the optocoupler OP1 and the driver chip U1, respectively. The two current pins are I-EER+ and I-EER-, both used to connect the light-emitting diodes LED1 and LED2, thereby forming a complete circuit for the light-emitting indication.
[0034] The above description is merely a preferred embodiment of this utility model. It should be noted that for those skilled in the art, other parts not specifically described are existing technology or common knowledge. Several improvements and modifications can be made without departing from the principle of this utility model, and these improvements and modifications should also be considered within the protection scope of this utility model.
Claims
1. A high-power frequency converter with overvoltage protection, characterized in that, The system includes a frequency converter module, an IGBT-based bleeder arm, a protection circuit, a protection control board, an excitation transformer, a reactor, and a test capacitor. The two output terminals of the frequency converter module are connected to the two ends of the high-voltage winding of the excitation transformer, and the two ends of the low-voltage winding of the excitation transformer form a low-voltage side circuit through a series reactor and a test capacitor. The protection control board is connected to the bleeder arm and also connects to the two output terminals of the frequency converter module through the two ends of a built-in isolation transformer. The protection circuit is located between the two ends of the isolation transformer and includes two surge protectors connected in series. The bleeder arm is located between the two output terminals of the frequency converter module.
2. The high-power frequency converter with overvoltage protection according to claim 1, characterized in that, The discharge arm is an inverter IGBT arm, including IGBT1 and IGBT2. Corresponding anti-parallel diodes are connected between the collector and emitter of IGBT1 and IGBT2 respectively. The gates of IGBT1 and IGBT2 are connected to the protection control board respectively.
3. A high-power frequency converter with overvoltage protection according to claim 1, characterized in that, In the protection circuit, the two surge protectors connected in series are grounded, and both ends of the two surge protectors connected in series are connected to the two ends of the isolation transformer.
4. A high-power frequency converter with overvoltage protection according to claim 1, characterized in that, The protection control board includes a drive control circuit, an isolation transformer, a judgment circuit, a feedback circuit, and a power supply module. The input of the judgment circuit is connected to the isolation transformer, and the output of the judgment circuit is connected to the drive control circuit through the feedback circuit. The drive control circuit is connected to the discharge bridge arm, and the power supply module is connected to both the drive control circuit and the feedback circuit.
5. A high-power frequency converter with overvoltage protection according to claim 4, characterized in that, The drive control circuit includes at least a drive chip U1; the drive chip U1 is connected in sequence to the collector, gate and emitter of any IGBT in the discharge bridge arm through diode D1, resistor R1 and resistor R2 respectively.
6. A high-power frequency converter with overvoltage protection according to claim 4, characterized in that, The judgment circuit includes resistor R6, variable resistor PR1, diode D3, bidirectional trigger diode DW1, capacitor C4, and transistor Q1. The base of transistor Q1 is connected to the inverting input terminal of diode D3 through bidirectional trigger diode DW1. The non-inverting input terminal of diode D3 is connected to resistor R6. The sliding terminal and fixed terminal 1 of variable resistor PR1 are connected in parallel between resistor R6 and diode D3. The fixed terminal 2 of variable resistor PR1 is connected in parallel between bidirectional trigger diode DW1 and the base of transistor Q1 through capacitor C4. The collector and emitter of transistor Q1 are connected to the feedback circuit respectively.
7. A high-power frequency converter with overvoltage protection according to claim 6, characterized in that, The feedback circuit includes a first feedback unit based on an optocoupler and a second feedback unit for forming a feedback loop; The first feedback unit includes resistors R3 and R4, optocoupler OP1, optocoupler OP2, LED1, and LED2; the first end of optocoupler OP1 is connected to the collector of transistor Q1 through resistor R4, and the second end of optocoupler OP1 is connected to the power supply module through LED2; the first end of optocoupler OP2 is connected to the drive control circuit through resistor R3, and the second end of optocoupler OP2 is connected to the power supply module through LED1. The second feedback unit includes a silicon controlled rectifier (SCR1), a resistor R5, and a first RC voltage regulator circuit. The anode of the SCR1 is connected to the emitter of the transistor Q1, the cathode of the SCR1 is connected in parallel to the anode through the first RC voltage regulator circuit, and the gate of the SCR1 is connected to the power supply module through the resistor R5. A drive control circuit is also connected in parallel between the cathode of the SCR1 and the resistor R5.
8. A high-power frequency converter with overvoltage protection according to claim 4, characterized in that, The power supply module includes at least two voltage pins and two current pins.