Series resonance test system based on SiC power electronic transformer

Abstract

The invention relates to the field of electrical equipment, in particular to a series resonance test system based on a SiC power electronic transformer. The system comprises a power electronic transformer, a resonance reactor and a voltage divider, the power electronic transformer comprises a control module, a driving module, a three-phase rectification module, a high-frequency inversion module, a high-frequency transformer, an output inversion module and an output inversion module. The power electronic transformer is electrically connected with the voltage divider, the voltage divider is electrically connected with the resonance reactor, the resonance reactor is electrically connected with the output inversion module, and the three-phase rectification module, the high-frequency inversion module, the high-frequency transformer, the output inversion module and the output inversion module are in five-stage cascade connection in sequence. The control module is electrically connected with the voltage divider. According to the system, the five-stage power electronic transformer based on the SiC power electronic transformer is adopted, a variable-frequency power source and the transformer are integrally designed, the size and weight of equipment are remarkably reduced, and the system is more convenient to transport and deploy on site.

Description

Technical Field

[0001] The present invention relates to the field of electrical equipment, and in particular to a series resonance test system based on a SiC power electronic transformer. Background Art

[0002] In power systems and industrial applications, accurate evaluation of the insulation performance of high-voltage electrical equipment is the key to ensuring equipment reliability and safety. Traditional series resonance test systems, as important tools for evaluating the insulation performance of high-voltage electrical equipment, are usually composed of variable frequency power supplies, excitation transformers, resonant reactors, and voltage dividers. When these systems are working, by forming a series resonance circuit, the AC power supply only outputs active power at the resonant frequency, thereby significantly reducing the power demand of the required power supply. However, the series resonance test systems existing in the prior art, such as the series resonance withstand voltage test device based on a multi-phase power supply described in patent CN107783014A, and the variable frequency parallel resonance withstand voltage test method based on cascade boost mentioned in patent CN109521338B, all have certain limitations.

[0003] Although the device in patent CN107783014A uses a multi-phase power supply and a current conversion unit to improve working efficiency, it still relies on a traditional excitation transformer to achieve voltage boosting, which limits the further reduction of the volume and weight of the device and also increases the complexity and cost of the system. In addition, the system still faces the challenge of large power supply capacity requirements when conducting withstand voltage tests on high-voltage and large-capacity equipment.

[0004] Patent CN109521338B proposes a variable frequency parallel resonant withstand voltage test method based on series boost, which uses two resonant reactors with different inductances to achieve boost, reducing the reliance on large-capacity power supplies. However, this method may face matching and tuning problems of resonant reactors in practical applications, and may face challenges in efficiency and stability at high frequencies. Therefore, in view of the problems of large volume and high energy loss in the prior art, a series resonant test system based on SiC power electronic transformers is urgently needed. Summary of the invention

[0005] The present invention provides a series resonance test system based on a SiC power electronic transformer, aiming to solve the problems of large volume and high energy loss in the prior art.

[0006] To achieve the above purpose, the following technical solution is adopted.

[0007] A series resonance test system based on SiC power electronic transformer, comprising:

[0008] A power electronic transformer, a resonant inductor and a voltage divider; the power electronic transformer includes a control module, a drive module, a three-phase rectifier module, a high-frequency inverter module, a high-frequency transformer, an output inverter module and an output inverter module;

[0009] The power electronic transformer is electrically connected to the voltage divider, the voltage divider is electrically connected to the resonant inductor, the resonant inductor is electrically connected to the output inverter module, the three-phase rectifier module, the high-frequency inverter module, the high-frequency transformer, the output inverter module and the output inverter module are cascaded in five stages in sequence; the control module is electrically connected to the voltage divider, the control module is used to receive the low-voltage signal fed back by the voltage divider and control the switching device of the power electronic transformer, perform autonomous frequency sweep and select the resonant frequency; the drive module is used to receive the drive signal output by the control module, drive the high-frequency inverter module and the high-voltage devices in the output inverter module, and realize voltage isolation and drive signal amplification; the high-frequency inverter module and the output inverter module are both H-bridge inverters built with SiC devices.

[0010] Optionally, the three-phase rectifier module is used to rectify the input three-phase AC mains power into DC power;

[0011] The high-frequency inverter module is used to receive the direct current output by the three-phase rectifier module, invert the direct current into high-frequency alternating current, and provide input for the high-frequency transformer;

[0012] The high-frequency transformer is used to receive the high-frequency alternating current output by the high-frequency inverter module and boost the high-frequency alternating current to a required peak voltage;

[0013] The high-frequency rectifier module is connected to the high-frequency transformer and is used to convert the boosted high-frequency alternating current into direct current to provide energy for the output inverter module;

[0014] The output inverter module is used to receive the direct current output by the high-frequency rectifier module, and invert the direct current into alternating current matching the resonant frequency of the test product to achieve series resonance.

[0015] Optionally, the control module includes a main control chip and an analog-to-digital conversion circuit, the main control chip has an ARM module and an FPGA module built in, the ARM module is used for logic control, and the FPGA module is used for clock control; the analog-to-digital conversion circuit is electrically connected to the voltage divider, and is used to collect the voltage signal fed back by the voltage divider and input it into the main control chip.

[0016] Optionally, the driving module includes: a high-frequency inverter module driving circuit and an output inverter module driving circuit;

[0017] The high-frequency inverter module driving circuit is used to receive the control signal sent by the control module and drive the switch of the high-frequency inverter module. The high-frequency inverter module driving circuit includes a photoelectric isolation and voltage isolation module, which isolates the control signal from the high-frequency inverter module driving circuit through photoelectric isolation and isolates the power supply from the high-frequency inverter module driving circuit through electromagnetic isolation;

[0018] The output inverter module driving circuit is used to receive four control signals sent from the control module, and expand each control signal into five synchronous driving signals to drive and output multiple switching devices in the inverter module. The output inverter module driving circuit also includes photoelectric isolation and electromagnetic isolation modules, which isolate the control signal from the output inverter module driving circuit through photoelectric isolation, and isolate the power supply from the output inverter module driving circuit through electromagnetic isolation.

[0019] Optionally, the output inverter module adopts an SPWM sinusoidal pulse width modulation method, and the generation of the SPWM modulation signal includes the following steps:

[0020] The modulated signal is composed of three frequency components, namely the fundamental component, carrier harmonics and sideband harmonics;

[0021] Fundamental wave component, the expression is:

[0022] Carrier harmonics, expressed as:

[0023] Sideband harmonics, expressed as:

[0024] m=1, 2,…∞; n=1, 2,…∞

[0025] In the above formula, Q km is the amplitude of the modulated wave, Q kb is the amplitude of the sideband harmonics, Q kc is the amplitude of the carrier harmonic, E is the amplitude of the modulating signal, t is the time, ω m is the angular frequency of the debugging wave, ω c is the angular frequency of the carrier signal, J0 is the 0th order Bessel function;

[0026] The frequency of the modulation wave ranges from 30Hz to 300Hz;

[0027] The carrier frequency ranges from 600Hz to 6000Hz.

[0028] Optionally, the step of the control module performing automatic frequency scanning includes:

[0029] Set the sweep voltage amplitude V max ;

[0030] Using the set V max , initialize the duty cycle of the high-frequency inverter module, and adjust the modulation wave frequency of the output inverter module within a preset frequency range to perform an initial frequency sweep, collect voltage values ​​through a feedback channel, and record multiple frequency points with the maximum voltage values;

[0031] Between the obtained frequency points, frequency sweep is performed with a smaller step size, voltage values ​​are collected through the feedback channel, and multiple second frequency points with the largest voltage values ​​are recorded;

[0032] Between the obtained second frequency points, frequency sweep is performed with a minimum step length, voltage values ​​are collected through a feedback channel, and the frequency point with the maximum voltage value is determined as the resonant frequency point;

[0033] In the above frequency sweep process, when the voltage amplitude exceeds V max When the voltage is lower than V max Then perform frequency sweep to the next frequency point.

[0034] Optionally, the control module further includes an automatic pressurization function, and the operation steps of the automatic pressurization function include:

[0035] Determine the parameters of the pressurization process, including setting the pressurization voltage value and the corresponding pressurization time, and form a pressurization instruction;

[0036] Using the determined pressurization instruction, pressurization is performed based on the resonant frequency point obtained by automatic frequency sweeping, and the voltage value is monitored in real time through the feedback signal channel;

[0037] The duty cycle of the high-frequency inverter module is adjusted according to the monitoring result. During this process, when the voltage value drops suddenly, it is judged as a possible breakdown or resonant circuit detuning, and the control module controls the output inverter module to stop working immediately.

[0038] Optionally, the voltage divider is a capacitive voltage divider.

[0039] Optionally, the three-phase rectifier module includes a plurality of diodes connected to a filter composed of a current limiting inductor and a filter capacitor, wherein the current limiting inductor is used to prevent the diode from being damaged by excessive transient current, and the filter capacitor is used to smooth the DC output;

[0040] The high-frequency inverter module adopts SiC devices, the inverter frequency is set within a predetermined range, and the frequency is changed in the form of PWM. When the load voltage is lower than the preset value, the pulse width of the modulation signal is increased, and when the load voltage value is higher than the preset value, the pulse width of the modulation signal is reduced.

[0041] Optionally, the high-frequency transformer adopts a manganese-zinc ferrite core;

[0042] The high-frequency rectifier module is an H-bridge high-voltage rectifier composed of multiple high-voltage silicon stacks, and the output side of the high-frequency rectifier module is connected to a filter composed of a current-limiting inductor and a filter capacitor;

[0043] The output inverter module is an H-bridge inverter composed of a plurality of high-voltage resistant switching devices, and each of the switching devices is composed of a SiC single-tube MOSFET connected in series.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] The system of the present invention adopts a five-level power electronic transformer based on SiC power electronic transformer, integrates the variable frequency power supply and the transformer into an integrated design, significantly reduces the size and weight of the equipment, and makes the system easier to transport and deploy on site.

[0046] The present invention adopts SiC power electronic transformer, which has higher energy efficiency compared with the traditional variable frequency source transformer combination. The low loss characteristics of SiC devices and the high switching frequency of high-frequency inverter modules reduce energy loss and improve the overall efficiency of the system.

[0047] By adopting an H-bridge inverter built with SiC devices in a high-frequency inverter module and an output inverter module, and a sinusoidal pulse width modulation (SPWM) method, the present invention effectively reduces the harmonic content of the output voltage, reduces potential damage to the tested equipment, and improves the accuracy of the test and the reliability of the insulation performance evaluation of the equipment.

[0048] The FPGA module in the control module is used for clock control, the system clock is 50MHz, the signal period adjustment accuracy is 20ns, and the frequency adjustment accuracy is 0.002Hz. This enables the system to accurately control the test frequency and improve the accuracy of the test results.

[0049] The system design of the present invention takes the user's operating convenience into consideration, simplifies the test process through the automated frequency sweep and pressurization functions, reduces the professional requirements for operators, and improves the efficiency and safety of the test.

[0050] The system performs automatic frequency sweep and automatic pressurization through the control module, realizing automatic control of the test process, reducing manual intervention, and improving the accuracy and repeatability of the test.

[0051] By adding an automatic pressurization function to the control module and immediately stopping the output inverter module when an abnormal voltage drop is detected, the present invention significantly improves the safety of the test process and protects the safety of the tested equipment and test personnel. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 The module schematic diagram of a series resonance test system based on SiC power electronic transformer of the present invention.

[0053] Figure 2 The present invention is a schematic diagram of an output inverter module of a series resonance test system based on a SiC power electronic transformer.

[0054] Figure 3 The figure is a schematic diagram of the SPWM modulation principle of a series resonance test system based on SiC power electronic transformer of the present invention.

[0055] Figure 4 The present invention is a schematic diagram of a control module of a series resonance test system based on a SiC power electronic transformer.

[0056] Figure 5 The present invention is a schematic diagram of a driving module of a series resonance test system based on a SiC power electronic transformer.

[0057] Among them, 1. power electronic transformer; 11. control module; 111. main control chip; 112. analog-to-digital conversion circuit; 12. drive module; 121. high-frequency inverter module drive circuit; 122. output inverter module drive circuit; 13. three-phase rectifier module; 14. high-frequency inverter module; 15. high-frequency transformer; 16. high-frequency rectifier module; 17. output inverter module; 2. resonant inductor; 3. voltage divider. DETAILED DESCRIPTION

[0058] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be noted that the embodiments and features in the embodiments of the present application can be combined with each other without conflict.

[0059] The following detailed description is an exemplary description, which is intended to provide further detailed description of the present invention. Unless otherwise specified, all technical terms used in the present invention have the same meaning as those generally understood by those skilled in the art to which the present application belongs. The terms used in the present invention are only for describing specific embodiments, and are not intended to limit exemplary embodiments according to the present invention.

[0060] Example 1

[0061] like Figure 1 As shown, the present invention is a series resonance test system based on SiC power electronic transformer, using SiC devices as switch elements of the power electronic transformer 1, and adopting a five-stage cascade form to form a series resonance withstand voltage device of a high-voltage device with high controllability.

[0062] The power electronic transformer 1 comprises a power electronic transformer 1 , a resonant reactor 2 and a voltage divider 3 .

[0063] The input of the power electronic transformer 1 is 380V three-phase AC mains power, and the output is AC power with a peak voltage of 10kV and adjustable voltage and frequency. The power electronic transformer 1 is composed of a control module 11, a drive module 12, a three-phase rectifier module 13, a high-frequency inverter module 14, a high-frequency transformer 15, a high-frequency rectifier module 16 and an output inverter module 17. The various modules of the power electronic transformer 1 are integrated into a compact unit, wherein the control module 11 adopts a high-performance microprocessor, such as the ARMCortex-M series, to achieve high-speed data processing and control.

[0064] The driving module 12 is designed to be able to withstand high voltage and provide sufficient driving current to ensure reliable operation of the SiC device.

[0065] A five-stage cascade form is adopted, and the five stages are three-phase AC-DC, DC-AC, high-frequency transformer 15 (AC-AC), AC-DC, and DC-AC, which are respectively implemented by a three-phase rectifier module 13, a high-frequency inverter module 14, a high-frequency transformer 15, a high-frequency rectifier module 16, and an output inverter module 17.

[0066] The control module 11 is the control center of the power electronic transformer 1. It is responsible for receiving the high-voltage signal fed back by the voltage divider 3 to control and adjust the switch device of the power electronic transformer 1. It is mainly responsible for outputting the control signals of the two inverters of the high-frequency inverter module 14 and the output inverter module 17. Under the control of the control module 11, the high-frequency inverter module 14 is responsible for controlling the output voltage value, and the output inverter module 17 is responsible for controlling the output frequency. The control module 11 can control the power electronic transformer 1 to realize autonomous frequency sweeping and select the resonant frequency.

[0067] The driving module 12 drives the high-voltage devices in the high-frequency inverter module 14 and the output inverter module 17. Its main functions are voltage isolation and drive signal amplification. The drive signal is taken from the output of the control module 11. The driving module 12 has a built-in photoelectric isolation module and a voltage isolation module, which can achieve ground potential isolation and efficient drive of the drive signal.

[0068] The high-frequency inverter module 14 and the output inverter module 17 are both H-bridge inverters built with SiC devices, which have lower losses and higher breaking rates than traditional IGBTs. The high-frequency inverter module 14 and the output inverter module 17 solve two important problems: equipment miniaturization and low harmonic components of the output voltage. The volume of the high-frequency transformer 15 will decrease significantly as the frequency increases. The frequency of the output signal of the high-frequency inverter module 14 is selected to be 10kHz, and a pulse width modulation (PWM) method is adopted. The output inverter module 17 adopts a sinusoidal pulse width modulation (SPWM) method, and its switching frequency is 20 times the output voltage frequency. Compared with the traditional PWM method, the harmonic component is significantly reduced.

[0069] The reactance value of resonant reactor 2 is 50H, which can meet the test requirements of load capacitance of 6nF to 560nF. If the load capacitance range is exceeded, the load range can be adjusted by connecting the reactor in series or in parallel.

[0070] The voltage divider 3 adopts capacitive voltage division, and the voltage transformation ratio is 1 million:1, which can meet the voltage division requirement of the maximum output voltage of 1200kV.

[0071] Example 2

[0072] A series resonance test system based on SiC power electronic transformer consists of three parts, namely power electronic transformer 1, resonant reactor 2 and voltage divider 3. Power electronic transformer 1 is the core component of this test system, which consists of 7 parts, namely control module 11, drive module 12, three-phase rectifier module 13, high-frequency inverter module 14, high-frequency transformer 15, high-frequency rectifier module 16 and output inverter module 17. The low-voltage signal collected by the low-voltage arm of the capacitive voltage divider 3 is connected to the control module 11 as a feedback signal, which is used as the basis for adjusting the control signal. The input end of the variable frequency power supply is a three-phase AC mains power supply, the maximum rated output power of the variable frequency power supply is 200kVA, and the rated current of the power supply should exceed 300A. The reactance value of the resonant reactor 2 is 50H, and the voltage divider 3 adopts capacitive voltage division, and the voltage ratio is 1 million:1, which can meet the voltage division requirement of the maximum output voltage of 1200kV.

[0073] The power electronic transformer 1 is in a five-stage cascade form, and the main circuit part consists of five parts: a three-phase rectifier module 13, a high-frequency inverter module 14, a high-frequency transformer 15, a high-frequency rectifier module 16 and an output inverter module 17, which respectively undertake the five-stage functions of three-phase AC-DC, DC-AC, high-frequency transformer 15 (AC-AC), AC-DC, and DC-AC.

[0074] The three-phase rectifier module 13 is the first-stage three-phase AC-DC of the five-stage cascade of the power electronic transformer 1. It rectifies the three-phase mains power into direct current as the energy supply of the entire device. It is composed of six diodes with a rated conduction current of 500A and a rated voltage of 500V. A filter composed of a current limiting inductor and a filter capacitor is connected after the rectifier bridge. The current limiting inductor prevents the instantaneous current from being too large and causing damage to the diodes of the three-phase rectifier bridge. The current limiting inductor value is 10μH and the filter capacitor is 10mF.

[0075] The high-frequency inverter module 14 is the second-stage DC-AC of the five-stage cascade of the power electronic transformer 1, which inverts the DC into a high-frequency AC, and its output is used as the input of the high-frequency transformer 15. The inverter frequency is 10kHz, and the frequency conversion is performed in the form of PWM. It is mainly responsible for controlling the voltage value at the load end. When the load voltage is lower than the preset value, the pulse width of the modulation signal is increased, and when the load voltage value is higher than the preset value, the pulse width of the modulation signal is reduced. The switching device used by the inverter is a SiC device, and the selected model is CAB760M12HM3, with a rated voltage of 1200V and a rated current of 760A.

[0076] The high-frequency transformer 15 is the third-stage high-frequency transformer 15 (AC-AC) of the five-stage cascade of the power electronic transformer 1, which boosts the PWM rectangular wave with a peak value of 400V. The transformer ratio is 10kV:400V. The transformer adopts a manganese-zinc ferrite core and its operating frequency is 10kHz.

[0077] The high-frequency rectifier module 16 is the fourth-stage AC-DC of the five-stage cascade of the power electronic transformer 1. It is composed of four high-voltage silicon stacks to form an H-bridge high-voltage rectifier. The output side is connected to a filter composed of a current-limiting inductor and a filter capacitor. The inductance value is 1μH, the filter capacitor is 1mF, and a high-voltage film capacitor with a withstand voltage of 20kV is used.

[0078] like Figure 2 As shown, the output inverter module 17 is the fifth-level DC-AC of the five-level cascade of the power electronic transformer 1, which is the output stage of the power electronic transformer 1. It is composed of four 10kV high-voltage switches forming an H-bridge inverter, wherein each high-voltage switch is composed of five IMYH200R024M1H SiC single-tube MOSFETs connected in series. Figure 2 As shown, the single tube withstand voltage is 2kV and the rated current is 89A.

[0079] Example 3

[0080] like Figure 3 As shown, in order to reduce the harmonic components of the AC voltage output by the power electronic transformer 1, the output inverter module 17 adopts the SPWM modulation method. The SPWM modulation signal is generated as follows: Figure 3 As shown, the modulated signal is composed of three frequency components, namely the fundamental component, carrier harmonics and sideband harmonics.

[0081] The fundamental component is only related to the angular frequency ω of the debugging wave. m The carrier harmonics are related to the angular frequency ω of the carrier signal. c The sideband harmonics are related to ω c and ω m Are relevant.

[0082] The fundamental component can be described as:

[0083] Where Q km is the amplitude of the modulation wave, and E is the amplitude of the modulation signal.

[0084] The carrier harmonics can be described as:

[0085]

[0086] The sideband harmonics can be described as:

[0087]

[0088] m=1, 2, …∞; n=1, 2, …∞, J0 is a Bessel function of order 0.

[0089] Since the pressure frequency range of the series resonant withstand voltage is 30Hz~300Hz, the modulation wave frequency is also 30Hz~300Hz, and the carrier frequency range is 600Hz~6000Hz.

[0090] Example 4

[0091] like Figure 4 As shown, the control module 11 of the power electronic transformer 1 is composed of two parts, namely the main control chip 111 and the analog-to-digital conversion circuit 112. The main control chip 111 selects the ZYNQ7020 chip, with built-in ARM module and FPGA module. The ARM module is responsible for logic control, and the FPGA is responsible for clock control. The system clock is 50MHz, the signal cycle adjustment accuracy is 20ns, and the frequency adjustment accuracy is 0.002Hz. The analog-to-digital conversion circuit 112 is connected to the feedback signal of the capacitor voltage divider 3, and the voltage signal is collected and input into the main control chip 111 as a voltage reference. The main control chip 111 is provided with 8 I / O output ports, of which four output the control signal of the high-frequency inverter module 14, and four output the control signal of the output inverter module 17, and the output control signal is sent to the drive module 12.

[0092] Example 5

[0093] like Figure 5As shown, the drive module 12 consists of a high-frequency inverter module drive circuit 121 and an output inverter module drive circuit 122. The high-frequency inverter module drive circuit 121 receives the control signal of the high-frequency inverter module 14 sent by the main control chip 111, and outputs the drive signal to drive the four switches of the four high-frequency inverter modules 14 after isolation and amplification. The output inverter module drive circuit 122 receives the control signal of the four output inverter modules 17 sent by the main control chip 111, and expands each output signal to 5 synchronous drive signals, a total of 20 drive signals are expanded to drive 20 switch devices of the output inverter module 17. The high-frequency inverter module drive circuit 121 and the output inverter module drive circuit 122 both isolate the control signal from each drive circuit through photoelectric isolation, and isolate the power supply from each drive circuit through electromagnetic isolation. The voltage isolation of the high-frequency inverter module drive circuit 121 is 2kV, and the voltage isolation of the output inverter module drive circuit 122 is 10kV.

[0094] Example 6

[0095] The control module 111 adds automatic frequency sweeping and automatic pressurization functions, the sweeping frequency is 30Hz to 300Hz, and the frequency sweeping process can be described as:

[0096] Step 1: Set the sweep voltage amplitude V max .

[0097] Step 2: The duty cycle of the high-frequency inverter module 14 is initialized to 10%, and the modulation wave frequency of the output inverter module 17 is adjusted to sweep the frequency within the sweep frequency range with a step length of 0.5 Hz. The voltage value is collected through the feedback channel to obtain the three frequency points with the largest voltage value. During the sweep process, if the voltage amplitude exceeds V max , the duty cycle of the high-frequency inverter module 14 is immediately reduced until the voltage amplitude is lower than V max Then scan the next frequency point.

[0098] Step 3: Sweep again between the three frequency points obtained in step 2 with a sweep step of 0.02Hz, collect voltage values ​​through the feedback channel, and obtain the three frequency points with the largest voltage values. During the sweep process, if the voltage amplitude exceeds V max , the duty cycle of the high-frequency inverter module 14 is immediately reduced until the voltage amplitude is lower than V max Then scan the next frequency point.

[0099] Step 4: Sweep again between the three frequency points obtained in step 3 with a sweep step of 0.002 Hz, collect the voltage value through the feedback channel, and obtain the frequency point with the maximum voltage value. During the sweep process, if the voltage amplitude exceeds V max , the duty cycle of the high-frequency inverter module 14 is immediately reduced until the voltage amplitude is lower than Vmax Then scan the next frequency point.

[0100] After the above four steps, the resonant frequency point can be found with an accuracy of 0.002Hz.

[0101] The automatic pressurization function can be described as:

[0102] Step 1: Set the pressurization process, including the pressurization voltage value and the pressurization time of each voltage.

[0103] Step 2: Apply pressure at the frequency resonance point obtained by frequency sweeping, and at the same time observe the voltage value in real time through the feedback signal channel, and realize voltage regulation by adjusting the duty cycle of the high-frequency inverter module 14. If a sudden voltage drop occurs during the pressurization process, it means that a breakdown or a resonant circuit detuning has occurred, and the output inverter module 17 stops working immediately.

[0104] It is known from common technical knowledge that the present invention can be implemented by other embodiments that do not deviate from its spirit or essential features. Therefore, the above disclosed embodiments are only illustrative in all respects and are not exclusive. All changes within the scope of the present invention or within the scope equivalent to the present invention are included in the present invention.

Claims

1. A series resonance test system based on SiC power electronic transformer, characterized in that: include, A power electronic transformer (1), a resonant reactor (2) and a voltage divider (3); the power electronic transformer (1) comprises a control module (11), a drive module (12), a three-phase rectifier module (13), a high-frequency inverter module (14), a high-frequency transformer (15), a high-frequency rectifier module (16) and an output inverter module (17); The power electronic transformer (1) is electrically connected to the voltage divider (3), the voltage divider (3) is electrically connected to the resonant inductor (2), the resonant inductor (2) is electrically connected to the output inverter module (17), the three-phase rectifier module (13), the high-frequency inverter module (14), the high-frequency transformer (15), the high-frequency rectifier module (16) and the output inverter module (17) are sequentially cascaded in five stages; the control module (11) is electrically connected to the voltage divider (3), the control module (11 ) is used to receive the low-voltage signal fed back by the voltage divider (3) and control the switch device of the power electronic transformer (1) to perform autonomous frequency sweep and select the resonant frequency; the drive module (12) is used to receive the drive signal output by the control module (11) and drive the high-voltage devices in the high-frequency inverter module (14) and the output inverter module (17) to achieve voltage isolation and drive signal amplification; the high-frequency inverter module (14) and the output inverter module (17) are both H-bridge inverters constructed using SiC devices.

2. A series resonance test system based on SiC power electronic transformer according to claim 1, characterized in that: The three-phase rectifier module (13) is used to rectify the input three-phase AC mains power into DC power; The high-frequency inverter module (14) is used to receive the direct current output by the three-phase rectifier module (13), invert the direct current into high-frequency alternating current, and provide input for the high-frequency transformer (15); The high-frequency transformer (15) is used to receive the high-frequency alternating current output by the high-frequency inverter module (14) and boost the high-frequency alternating current to a required peak voltage; The high-frequency rectifier module (16) is connected to the high-frequency transformer (15) and is used to convert the boosted high-frequency alternating current into direct current to provide energy for the output inverter module (17); The output inverter module (17) is used to receive the direct current output by the high-frequency rectifier module (16), and invert the direct current into alternating current matching the resonance frequency of the test object, thereby realizing series resonance.

3. A series resonance test system based on SiC power electronic transformer according to claim 1, characterized in that: The control module (11) comprises a main control chip (111) and an analog-to-digital conversion circuit (112); the main control chip (111) has an ARM module and an FPGA module built in, the ARM module is used for logic control, and the FPGA module is used for clock control; the analog-to-digital conversion circuit (112) is electrically connected to the voltage divider (3) and is used for collecting a voltage signal fed back by the voltage divider (3) and inputting the collected voltage signal into the main control chip (111).

4. A series resonance test system based on SiC power electronic transformer according to claim 1, characterized in that: The driving module (12) comprises: a high-frequency inverter module driving circuit (121) and an output inverter module driving circuit (122); The high-frequency inverter module drive circuit (121) is used to receive a control signal sent by the control module (11) and drive a switch of the high-frequency inverter module (14); the high-frequency inverter module drive circuit (121) comprises a photoelectric isolation and voltage isolation module, which isolates the control signal from the high-frequency inverter module drive circuit (121) through photoelectric isolation, and isolates the power supply from the high-frequency inverter module drive circuit (121) through electromagnetic isolation; The output inverter module drive circuit (122) is used to receive four control signals sent from the control module (11), and expand each control signal into five synchronous drive signals to drive and output multiple switch devices in the inverter module. The output inverter module drive circuit (122) also includes a photoelectric isolation and an electromagnetic isolation module, and the control signal is isolated from the output inverter module drive circuit (122) through photoelectric isolation, and the power supply is isolated from the output inverter module drive circuit (122) through electromagnetic isolation.

5. A series resonance test system based on SiC power electronic transformer according to claim 1, characterized in that: The output inverter module (17) adopts an SPWM sinusoidal pulse width modulation method, and the generation of the SPWM modulation signal comprises the following steps: the modulation signal is composed of signals of three frequency components, namely a fundamental wave component, a carrier harmonic and a sideband harmonic; Fundamental wave component, the expression is: Carrier harmonics, expressed as: Sideband harmonics, expressed as: m=1,2,…∞; n=1,2,…∞ In the above formula, Q km is the amplitude of the modulated wave, Q kb is the amplitude of the sideband harmonics, Q kc is the amplitude of the carrier harmonic, E is the amplitude of the modulating signal, t is the time, ω m is the angular frequency of the debugging wave, ω c is the angular frequency of the carrier signal, J0 is the 0th order Bessel function; The frequency of the modulation wave ranges from 30Hz to 300Hz; The carrier frequency ranges from 600Hz to 6000Hz.

6. A series resonance test system based on SiC power electronic transformer according to claim 1, characterized in that: The step of the control module (11) performing automatic frequency scanning comprises: Set the sweep voltage amplitude V max ; Using the set V max , initializing the duty cycle of the high-frequency inverter module (14), and adjusting the modulation wave frequency of the output inverter module (17) within a preset frequency range to perform an initial frequency sweep, collecting voltage values ​​through a feedback channel, and recording a plurality of frequency points at which the voltage values ​​are maximum; Between the obtained frequency points, frequency sweep is performed with a smaller step size, voltage values ​​are collected through the feedback channel, and multiple second frequency points with the largest voltage values ​​are recorded; Between the obtained second frequency points, frequency sweep is performed with a minimum step length, voltage values ​​are collected through a feedback channel, and the frequency point with the maximum voltage value is determined as the resonant frequency point; In the above frequency sweep process, when the voltage amplitude exceeds V max When the voltage is lower than V max Then perform frequency sweep to the next frequency point.

7. A series resonance test system based on SiC power electronic transformer according to claim 1, characterized in that: The control module (11) further comprises an automatic pressurization function, and the operation steps of the automatic pressurization function include: Determine the parameters of the pressurization process, including setting the pressurization voltage value and the corresponding pressurization time, and form a pressurization instruction; Using the determined pressurization instruction, pressurization is performed based on the resonant frequency point obtained by automatic frequency sweeping, and the voltage value is monitored in real time through the feedback signal channel; The duty cycle of the high-frequency inverter module (14) is adjusted according to the monitoring result. During this process, when a sudden drop in the voltage value occurs, it is judged as a possible breakdown or resonant circuit detuning, and the control module (11) controls the output inverter module (17) to stop working immediately.

8. A series resonance test system based on SiC power electronic transformer according to claim 1, characterized in that: The voltage divider (3) is a capacitive voltage divider.

9. A series resonance test system based on SiC power electronic transformer according to claim 2, characterized in that: The three-phase rectifier module (13) comprises a plurality of diodes connected to a filter composed of a current limiting inductor and a filter capacitor, wherein the current limiting inductor is used to prevent damage to the diode caused by excessive instantaneous current, and the filter capacitor is used to smooth the DC output; The high-frequency inverter module (14) adopts SiC devices, the inverter frequency is set within a predetermined range, and frequency conversion is performed in the form of PWM. When the load voltage is lower than a preset value, the pulse width of the modulation signal is increased, and when the load voltage value is higher than the preset value, the pulse width of the modulation signal is reduced.

10. A series resonance test system based on SiC power electronic transformer according to claim 2, characterized in that: The high frequency transformer (15) adopts a manganese-zinc ferrite core; The high-frequency rectification module (16) is an H-bridge high-voltage rectifier composed of a plurality of high-voltage silicon stacks, and the output side of the high-frequency rectification module (16) is connected to a filter composed of a current-limiting inductor and a filter capacitor; The output inverter module (17) is an H-bridge inverter composed of a plurality of high-voltage resistant switch devices, each of which is composed of a SiC single-tube MOSFET connected in series.

Images