AC test power supply system

Abstract

The utility model provides an AC test power supply system, and belongs to the field of test power supplies. Comprising an EMC unit, a three-phase PFC unit, three DC / DC isolation units, three inversion units, a second control unit and a second signal acquisition unit. The output end of the EMC unit is connected to the three-phase PFC unit, the output end of the three-phase PFC unit is connected to the three DC / DC isolation units, the output ends of the three DC / DC isolation units are connected to the three inversion units, and output N pins of the three inversion units are connected in parallel; and the second signal acquisition unit is connected with the second control unit and the three inversion units. The utility model has the advantages of comprehensive function, high efficiency, high voltage precision, flexible power expansion and low AC output harmonic content.

Description

Technical Field

[0001] This utility model relates to the field of test power supply technology, specifically to an AC test power supply system. Background Technology

[0002] An AC test power supply is a power supply device used for testing and calibrating electrical equipment. It provides a stable AC power output to supply power to electrical equipment, and can also measure parameters such as current and voltage of the equipment.

[0003] Most common AC test power supply solutions on the market currently use power frequency transformers for isolation, resulting in large size and low efficiency. They employ conventional sampling circuits, which are limited by large resistance temperature drift and low bit depth of the integrated AD converter, making it difficult to improve output voltage accuracy. Furthermore, their use of conventional unipolar or bipolar modulation methods leads to high AC output harmonic content, easily causing malfunctions in user equipment. Therefore, existing AC test power supplies have limited functionality, low output voltage accuracy, inflexible power expansion, and high AC output harmonic content, failing to meet the needs of various application scenarios. Utility Model Content

[0004] The technical problem to be solved by this utility model is how to provide a fully functional AC test power supply system.

[0005] To solve the above-mentioned technical problems, this utility model provides the following technical solution: an AC test power supply system, including an EMC unit, a three-phase PFC unit, a three-channel DC / DC isolation unit, a three-channel inverter unit, a second control unit, and a second signal acquisition unit; the output terminal of the EMC unit is connected to the three-phase PFC unit, the output terminal of the three-phase PFC unit is connected to the three-channel DC / DC isolation unit, the output terminal of the three-channel DC / DC isolation unit is connected to the three-channel inverter unit, and the N-pins of the three-channel inverter unit are connected in parallel; the second signal acquisition unit is connected to the second control unit and the three-channel inverter unit.

[0006] This utility model includes three sets of independent inverter units, so the output voltage and phase of each inverter unit can be set independently, enabling single-phase, three-phase and split-phase output functions. It is comprehensive in function and can meet a wider range of application scenarios.

[0007] Preferably, it includes a second drive unit, and the second control unit is connected to three DC / DC isolation units and three inverter units through the second drive unit.

[0008] In this invention, the PWM drive signal of the second control unit can be converted into a level signal suitable for the switching of silicon carbide MOSFETs after passing through the second drive unit, and then sent to the three DC / DC isolation units and the three inverter units respectively.

[0009] Preferably, it further includes a first control unit, a first drive unit, and a first signal acquisition unit, wherein the first drive unit and the first signal acquisition unit are connected to the first control unit and are connected to the three-phase PFC unit.

[0010] The first signal acquisition unit of this utility model can acquire the three-phase mains input voltage, input current, output bus voltage and MOSFET temperature of the three-phase PFC unit and send them to the first control unit. The first control unit can realize the voltage regulation control of the PFC output bus and the input power factor correction. At the same time, it can realize overvoltage, overcurrent and overtemperature protection functions based on the acquired information. The PWM drive signal of the first control unit can be converted into a level signal suitable for silicon carbide MOSFET switching by the first drive unit and sent to the three-phase PFC unit.

[0011] Preferably, it also includes a third control unit, wherein the first control unit is connected to the second control unit, and the second control unit is also connected to the third control unit.

[0012] In this invention, the first control unit sends the status information of the three-phase PFC unit to the second control unit, and the second control unit can send the status information of the DC / DC isolation unit, the inverter unit, and the three-phase PFC unit to the third control unit.

[0013] Preferably, it also includes a liquid crystal display unit and a user communication unit, both of which are connected to the third control unit.

[0014] This utility model includes an independent user communication unit, which facilitates remote command operation by the user; it also includes an independent LCD display unit, which makes it convenient and quick to display and set status parameters such as current, voltage, power, THD, and working mode, with good operability and a user-friendly human-machine interface.

[0015] Preferably, it further includes an optical fiber communication unit, which is connected to the second control unit.

[0016] This utility model includes an optical fiber communication unit, which enables multiple units to be connected in parallel, improves the reliability of parallel connection, expands and enhances the system power, and allows users to flexibly build AC test power supply systems according to power requirements.

[0017] Preferably, it also includes a high-precision acquisition unit, which is connected to the second control unit and three inverter units.

[0018] Preferably, the circuit of the high-precision acquisition unit includes a first amplifier circuit, a second amplifier circuit, and a conversion circuit connected in sequence, and the input terminal of the first amplifier circuit is connected to the output terminal of one of the three inverter units.

[0019] Preferably, the first amplification circuit includes cryogenic film resistors R1 and R2, and an instrumentation amplifier U1; the second amplification circuit includes a differential signal amplifier U2; and the conversion circuit includes an AD converter U3. Pin 1 of the cryogenic film resistor R1 is connected to the output L pin of one of the three inverter units; the output N pin of this inverter unit is connected to pin 1 of the cryogenic film resistor R2; pin 2 of the cryogenic film resistor R1 is connected to pin 2 of the cryogenic film resistor R2 and grounded; pin 3 of the cryogenic film resistor R1 is connected to the positive input pin of the instrumentation amplifier U1; pin 3 of the cryogenic film resistor R2 is connected to the negative input pin of the instrumentation amplifier U1; the output pin of the instrumentation amplifier U1 is connected to the positive input pin of the differential signal amplifier U2 in the second amplification circuit; the positive output pin of the differential signal amplifier U2 is connected to the positive input terminal of the AD converter U3 in the conversion circuit; and the negative output pin of the differential signal amplifier U2 is connected to the negative input terminal of the AD converter U3.

[0020] The high-precision acquisition unit of this invention uses a low-temperature drift film resistor, an instrumentation amplifier, and an AD converter to acquire the output voltage, enabling accurate acquisition, control, and display of AC output voltage, thereby improving the accuracy of the output voltage.

[0021] Preferably, the circuit of the DC / DC isolation unit includes eight MOSFETs: Q5 to Q12, and a transformer; MOSFETs Q5 and Q6 are connected in series and in parallel with MOSFETs Q7 and Q8 connected in series; MOSFETs Q9 and Q10 are connected in series and in parallel with MOSFETs Q11 and Q12 connected in series; pins 1 and 2 of the transformer are on the same side, and pins 3 and 4 are on the same side; pin 1 of the transformer is connected to the end where MOSFETs Q5 and Q6 are connected; pin 2 of the transformer is connected to the end where MOSFETs Q7 and Q8 are connected; pin 4 of the transformer is connected to the end where MOSFETs Q9 and Q10 are connected; and pin 3 of the transformer is connected to the end where MOSFETs Q11 and Q12 are connected.

[0022] The DC / DC isolation unit circuit of this invention adopts a series resonant DAB topology, which can realize soft switching of MOA transistors, thereby improving efficiency and operating density.

[0023] Compared with existing technologies, the advantages of this utility model are:

[0024] (1) The AC output frequency, phase and voltage of three independent inverter units are controlled by the control unit, which is compatible with single-phase, three-phase and split-phase modes and can meet a wider range of application scenarios. The inverter unit adopts unipolar frequency doubling modulation. With the bridge arm MOS tube operating frequency unchanged, the inverter inductor operating frequency is doubled, the AC output harmonic content is lower, and the user equipment is guaranteed to work normally.

[0025] (2) Using fiber optic communication to achieve parallel connection of multiple machines improves the reliability of parallel connection, realizes the expansion and enhancement of system power, and facilitates users to flexibly build AC test power supply system according to power requirements;

[0026] (3) The DC / DC isolation unit adopts a series resonant DAB topology, which realizes soft switching of MOSFETs and can improve efficiency and power density;

[0027] (4) The high-precision acquisition unit uses a low-temperature drift film resistor, an instrumentation amplifier and a high-precision AD converter to achieve accurate acquisition, control and display of AC output voltage, thereby improving the accuracy of output voltage;

[0028] (5) The three communication-connected control units can send the status information of the three-phase PFC unit, DC / DC isolation unit and inverter unit to the LCD display unit, display the status of each unit and provide fault alarms. The LCD display unit can also receive the user's parameter setting instructions and send them to the three control units to realize the adjustment of AC output frequency, phase and voltage. The human-machine interaction is convenient and fast. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the system composition according to an embodiment of the present utility model;

[0030] Figure 2 This is a first amplifier circuit diagram of the high-precision acquisition unit in this embodiment of the present invention;

[0031] Figure 3 This is a second amplifier circuit diagram of the high-precision acquisition unit in an embodiment of this utility model;

[0032] Figure 4 This is a conversion circuit diagram of the high-precision acquisition unit in this embodiment of the utility model;

[0033] Figure 5 This is a circuit diagram of the three-phase PFC unit in an embodiment of this utility model;

[0034] Figure 6 This is a circuit diagram of the DC / DC isolation unit in an embodiment of this utility model;

[0035] Figure 7 This is a circuit diagram of the inverter unit in an embodiment of this utility model. Detailed Implementation

[0036] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0037] Example

[0038] like Figure 1 As shown, this embodiment provides an AC test power supply system, including an EMC unit, a three-phase PFC unit, a three-channel DC / DC isolation unit, a three-channel inverter unit, three control units, two drive units, two signal acquisition units, a high-precision acquisition unit, a user communication unit, an LCD display unit, and an optical fiber communication unit.

[0039] The output of the EMC unit is connected to the input of the three-phase PFC unit. The output of the three-phase PFC unit is connected to three DC / DC isolation units. The outputs of the three DC / DC isolation units are connected to three inverter units. The first control unit is connected to the first drive unit and the first signal acquisition unit. The first drive unit and the first signal acquisition unit are connected to the three-phase FPC unit. The second control unit is connected to the second drive unit, the second signal acquisition unit, and the high-precision acquisition unit. The second drive unit is connected to the three DC / DC isolation units and the three inverter units. The second signal acquisition unit and the high-precision acquisition unit are connected to the three inverter units. The output N-line of the three inverter units is connected in parallel. The first control unit is connected to the second control unit. The second control unit is also connected to the third control unit. The user communication unit and the LCD display unit are connected to the third control unit. The fiber optic communication unit is connected to the second control unit.

[0040] The first signal acquisition unit acquires the three-phase mains input voltage, input current, output bus voltage, and MOSFET temperature of the three-phase PFC unit and sends them to the first control unit. The first control unit uses a DSP processor to perform voltage regulation control and input power factor correction of the PFC output bus. At the same time, it implements overvoltage, overcurrent, and overtemperature protection functions based on the acquired information. The PWM drive signal of the first control unit is converted into a suitable level signal for the silicon carbide MOSFET by the first drive unit and sent to the three-phase PFC unit.

[0041] The second signal acquisition unit acquires the inverter bus voltage, AC output voltage, inverter inductor current, output load current, and MOSFET temperature, and sends them to the second control unit. The second control unit uses a DSP processor to perform voltage regulation control of the inverter bus voltage, and voltage, frequency, and phase control of the AC output. At the same time, it implements overvoltage, overcurrent, overtemperature, and over / underfrequency protection functions based on the acquired information. The PWM drive signal of the second control unit is converted into a suitable level signal for the silicon carbide MOSFET switch by the second drive unit and sent to the three DC / DC isolation units and the three inverter units respectively.

[0042] The mains power is fed into the EMC unit for filtering. The output of the EMC unit is connected to the three-phase PFC unit for power factor correction and outputs a stable DC voltage. The output of the three-phase PFC unit is connected to three DC / DC isolation units for isolation conversion, providing independent DC bus voltages for the three inverter units. The inverter units modulate the DC bus into three independent AC outputs with adjustable frequency, phase, and voltage.

[0043] When the user selects the single-phase output mode, the output L lines of the three inverter units are connected in parallel externally. The second control unit controls the AC output frequency, phase and voltage of the three inverter units to synchronize, realizing single-phase parallel output. The output frequency and voltage can be set by the user.

[0044] When the user selects the three-phase output mode, the second control unit controls the AC output frequency of the three inverter units to be synchronized, the voltage amplitude is the same, and the phase difference is 120 degrees, so as to realize three-phase output. The output frequency and voltage can be set by the user.

[0045] When the user selects the phase-splitting output mode, the second control unit controls the AC output frequency of the three inverter units to be synchronized and can be set by the user. The voltage and voltage of each inverter are independent of each other, realizing phase-splitting output. The user can set the output phase and voltage of each phase independently.

[0046] The AC test voltage system in this embodiment uses three sets of independent inverter units, which are compatible with single-phase, three-phase and split-phase output modes, and can meet a wider range of application scenarios.

[0047] In this embodiment, the first control unit and the second control unit use RS485 communication, the second control unit and the third control unit use SPI communication, and the third control unit and the liquid crystal display unit use LVDS communication.

[0048] The first control unit sends the status information of the three-phase PFC unit to the second control unit. The second control unit sends the status information of the DC / DC isolation unit, inverter unit, and three-phase PFC unit to the third control unit. The third control unit sends the above status information to the LCD display unit for status display and fault alarm prompts. The LCD display unit also receives the user's parameter setting instructions and sends them to the three control units for execution, realizing the adjustment of AC output frequency, phase, and voltage, making human-machine interaction convenient and fast.

[0049] The third control unit is extended to multiple communication interfaces such as RS232, RS485, CAN, and Ethernet via the user communication unit, which facilitates remote command operation by the user.

[0050] The fiber optic communication unit utilizes commercially available optical transceiver modules to achieve parallel operation of multiple units, offering good anti-interference capabilities and improved parallel reliability. When multiple units operate in parallel, the master unit sends output voltage and current information to each slave unit. The slave units then fine-tune their output voltages based on the master unit's parameters while maintaining phase synchronization, achieving parallel current sharing. The use of the fiber optic communication unit expands and enhances system power, allowing users to flexibly construct AC test power supply systems according to their power requirements.

[0051] Combination Figure 2 , 3 4 and 5 represent the first amplifier circuit, the second amplifier circuit, and the conversion circuit that are sequentially connected in the circuit of the high-precision acquisition unit in this embodiment.

[0052] The input terminal of the first amplifier circuit is connected to the output terminal of one of the three inverter units. In this embodiment, the input terminal of the first amplifier circuit is connected to the output terminal of the first inverter unit. The first amplifier circuit includes low-temperature drift film resistors R1 and R2, resistors R3 and R4, capacitors C1, C2, C3, C4, C6, C7, and C8, and an instrumentation amplifier U1. In this embodiment, U1 is an INA128. Both low-temperature drift film resistors R1 and R2 are composed of two resistors connected in series. Pin 1 of low-temperature drift film resistor R1 is connected to the output L pin of the first inverter unit, and pin 2 is connected to pin 2 of low-temperature drift film resistor R2 and grounded. Pin 1 of low-temperature drift film resistor R2 is connected to the output N pin of the first inverter unit. Pin 3, the junction between the series resistors of low-temperature drift film resistor R1, is connected to one end of resistor R4. The other end of resistor R4 is connected to the positive input pin of instrumentation amplifier U1. Pin 3, the junction between the series resistors of low-temperature drift film resistor R2, is connected to one end of resistor R3. The other end of resistor R3 is connected to the negative input pin of instrumentation amplifier U1. The output pin of instrumentation amplifier U1 is connected to the second amplifier circuit.

[0053] After capacitors C1 and C2 are connected in parallel, one end is connected to the positive power supply pin of instrumentation amplifier U1, and the other end is grounded. The positive power supply pin of instrumentation amplifier U1 is also connected to a +12V power supply. After capacitors C7 and C8 are connected in parallel, one end is connected to the negative power supply pin of instrumentation amplifier U1, and the other end is grounded. The negative power supply pin of instrumentation amplifier U1 is also connected to a -12V power supply. Capacitors C3, C4, and C6 are connected in series. The end of capacitor C3 connected to capacitor C4 is connected to the negative input terminal of instrumentation amplifier U1, and the other end of capacitor C3 is grounded. The end of capacitor C4 connected to capacitor C6 is connected to the positive input terminal of instrumentation amplifier U1, and the other end of capacitor C6 is grounded.

[0054] The second amplification circuit includes a differential signal amplifier U2, resistors R5, R6, R7, R8, R9, R13, and R15, and capacitors C9, C10, and C11. In the first amplification circuit, the output pin of the instrumentation amplifier U1 is connected to one end of resistor R6, and the other end of resistor R6 is connected to one end of resistor R8 and then to the positive input pin of the differential signal amplifier U2. In this embodiment, the differential signal amplifier U2 is an ADA4940. The other end of resistor R8 is connected to the negative output pin of the differential signal amplifier U2. The positive output pin of the differential signal amplifier U2 is connected to one end of resistor R13, and the negative output pin of the differential signal amplifier U2 is connected to one end of resistor R15. The other ends of resistors R13 and R15 are connected to the conversion circuit.

[0055] One end of resistor R5 is connected to the DISABLE pin of differential signal amplifier U2, and the other end is connected to the power supply. One end of resistor R7 is connected to one end of resistor R9 and is connected to the negative input terminal of differential signal amplifier U2. The other end of resistor R9 is connected to the positive output terminal of differential signal amplifier U2, and the other end of resistor R7 is grounded. Capacitors C9 and C11 are connected in series and in parallel with capacitor C10 and then connected to the positive and negative input terminals of AD converter U3. The end of capacitors C9 and C11 connected is grounded. The +VS and -VS pins of differential signal amplifier U2 are connected to the +5V and -5V power supply, respectively.

[0056] The conversion circuit includes an AD converter U3 and resistors R10 to R14. In this embodiment, the AD converter U3 is model AD7175-2. The SDI1 pin of the AD converter U3 is connected to one end of resistor R10, and the other end of resistor R10 is grounded. The SCK1, SDO1, and CNV1 pins of the AD converter U3 are connected to one end of resistors R11, R12, and R13, respectively. The other ends of the three resistors are all connected to a +3.3V power supply. The REF1, VDD1, and VIO1 pins of the AD converter U3 are connected to +5V, +2.5V, and +3.3V power supplies, respectively.

[0057] The AC output voltage is divided by low-temperature drift film resistors R1 and R2 and then connected to instrumentation amplifier U1. After differential amplification by U1, it is connected to single-ended to differential signal amplifier U2. After 1:1 amplification, it is connected to 16-bit high-precision AD converter U3. The AD converter and the second control unit transmit the output voltage data via SPI communication.

[0058] In this embodiment, the high-precision acquisition unit uses a low-temperature drift film resistor, an instrumentation amplifier, and a 16-bit high-precision AD converter to acquire the output voltage. The second control unit uses the output voltage acquired by the high-precision acquisition unit to calibrate the output voltage sampling coefficient of the second signal acquisition unit, thereby realizing accurate acquisition, control, and display of AC output voltage and improving output voltage accuracy.

[0059] like Figure 5 The diagram shows the circuit of the three-phase PFC unit in this embodiment, including three phase bridge arms, a variable capacitor, three capacitors, and three inductors. Each phase bridge arm includes an upper bridge arm and a lower bridge arm, each containing a MOSFET. The variable capacitor is connected in parallel with the three phase bridge arms. One end of each of the three capacitors is connected together, and the other end is connected to the three-phase output of the EMC unit and to pin 1 of each of the three inductors. Pin 2 of each of the three inductors is connected to the three phase bridge arms, with the connection points located between the upper and lower bridge arms of each phase bridge arm. In this embodiment, the three-phase PFC unit uses a two-level SV modulation method, resulting in higher bus utilization.

[0060] like Figure 6 The diagram shown is a circuit diagram of the DC / DC isolation unit in this embodiment, including eight MOSFETs: Q5 to Q12, a transformer, and two capacitors. MOSFETs Q5 and Q6 are connected in series and in parallel with MOSFETs Q7 and Q8 (also connected in series). MOSFETs Q9 and Q10 are connected in series and in parallel with MOSFETs Q11 and Q12 (also connected in series). MOSFETs Q11 and Q12 are also connected in parallel with a capacitor. Pins 1 and 2 of the transformer are on the same side, and pins 3 and 4 are on the same side. Pin 1 of the transformer is connected to the end where MOSFETs Q5 and Q6 are connected, pin 2 is connected to the end where MOSFETs Q7 and Q8 are connected, pin 4 is connected to the end where MOSFETs Q9 and Q10 are connected, and pin 3 is connected to one end of a capacitor. The other end of the capacitor is connected to the end where MOSFETs Q11 and Q12 are connected.

[0061] In this embodiment, the DC / DC isolation unit adopts a series resonant DAB converter, which uses the leakage inductance of the high-frequency transformer and the resonant capacitor for resonance. The MOSFETs located diagonally are turned on and off simultaneously, and the two sets of MOSFETs conduct alternately. The switching frequency is the resonant frequency of the transformer leakage inductance and the resonant capacitor. At this time, the current waveform of the MOSFET is close to sinusoidal, and the drain of the MOSFET achieves zero voltage turn-on and near-zero current turn-off. The MOSFET achieves soft switching, which greatly reduces switching losses and greatly improves efficiency. The secondary MOSFET operates in synchronous rectification mode. Taking advantage of the low on-resistance of the MOSFET, it replaces the body diode for conduction, resulting in a lower on-voltage drop and lower losses.

[0062] like Figure 7 The diagram shown is a circuit diagram of the inverter unit in this embodiment, including four MOSFETs: Q1 to Q4, two inductors: L1 and L2, and one capacitor C0. MOSFETs Q1 and Q2 are connected in series and in parallel with the series-connected MOSFETs Q3 and Q4. One end of inductor L1 is connected to the end where MOSFETs Q1 and Q2 are connected, and the other end of inductor L1 is connected to the output L pin. One end of inductor L2 is connected to the end where MOSFETs Q3 and Q4 are connected, and the other end of inductor L2 is connected to the output N pin. The two ends of capacitor C0 are connected to the output L pin and the output N pin, respectively.

[0063] In this embodiment, the inverter unit adopts unipolar frequency doubling modulation. The principle of unipolar frequency doubling modulation is as follows: During the positive half-cycle of the inverter output voltage Vo, when the triangular carrier voltage Vtri is between the forward and reverse modulation wave voltages Vsin1 and Vsin2, Q2 and Q3 are turned on, Q1 and Q4 are turned off, and the inverter bridge arm is turned on. When the triangular carrier voltage Vtri is higher than the forward modulation wave voltage Vsin1, Q1 and Q3 are turned off, Q2 and Q4 are turned on, and the inverter bridge arm is turned off. When the triangular carrier voltage Vtri is lower than the reverse modulation wave voltage Vsin2, Q1 and Q3 are turned on, Q2 and Q4 are turned off, and the inverter bridge arm is turned off. Within one triangular carrier Vtri cycle, the midpoint of the inverter bridge arm switches twice, realizing frequency doubling modulation.

[0064] During the negative half-cycle of the inverter output voltage Vo, when the triangular carrier voltage Vtri is between the positive and negative modulation wave voltages Vsin1 and Vsin2, Q1 and Q4 are turned on, Q2 and Q3 are turned off, and the inverter bridge arm is turned on. When the triangular carrier voltage Vtri is higher than the modulation wave voltage Vsin2, Q1 and Q3 are turned off, Q2 and Q4 are turned on, and the inverter bridge arm is turned off. When the triangular carrier voltage Vtri is lower than the modulation wave voltage Vsin1, Q1 and Q3 are turned on, Q2 and Q4 are turned off, and the inverter bridge arm is turned off. Within one triangular carrier voltage Vtri cycle, the midpoint of the inverter bridge arm switches twice, achieving frequency doubling modulation.

[0065] This embodiment can double the operating frequency of the inverter inductor while keeping the operating frequency of the bridge arm MOSFET unchanged, resulting in lower harmonic content in the AC output.

[0066] This embodiment includes three independent inverter units, each with independently settable output voltage and phase, enabling single-phase, three-phase, and split-phase output functions to meet a wider range of application scenarios. Fiber optic communication is used to achieve parallel connection of multiple units, improving parallel reliability and expanding and increasing system power, allowing users to flexibly construct AC test power supply systems according to power requirements. The power conversion circuits all use silicon carbide MOSFETs, and the DC / DC isolation unit adopts a series resonant DAB topology, achieving soft switching of the MOSFETs and improving efficiency and power density. The inverter unit uses unipolar frequency doubling modulation, doubling the inverter inductor operating frequency while keeping the bridge arm MOSFET operating frequency unchanged, resulting in lower AC output harmonic content. The high-precision acquisition unit uses low-temperature drift film resistors, instrumentation amplifiers, and a 16-bit high-precision AD converter to achieve accurate acquisition, control, and display of the AC output voltage, improving output voltage accuracy.

[0067] The above-disclosed embodiments are merely preferred embodiments of the present utility model and should not be construed as limiting the scope of protection of the present utility model. Therefore, any equivalent changes made in accordance with the claims of the present utility model shall still fall within the scope of the present utility model.

Claims

1. An AC test power supply system, characterized in that, It includes an EMC unit, a three-phase PFC unit, a three-channel DC / DC isolation unit, a three-channel inverter unit, a second control unit, and a second signal acquisition unit; the output terminal of the EMC unit is connected to the three-phase PFC unit, the output terminal of the three-phase PFC unit is connected to the three DC / DC isolation units, the output terminals of the three DC / DC isolation units are connected to the three inverter units, and the N-pins of the outputs of the three inverter units are connected in parallel. The second signal acquisition unit is connected to the second control unit and three inverter units.

2. The AC test power supply system according to claim 1, characterized in that, It also includes a second drive unit, through which the second control unit is connected to three DC / DC isolation units and three inverter units.

3. The AC test power supply system according to claim 2, characterized in that, It also includes a first control unit, a first drive unit, and a first signal acquisition unit, wherein the first drive unit and the first signal acquisition unit are connected to the first control unit and are connected to the three-phase PFC unit.

4. An AC test power supply system according to claim 3, characterized in that, It also includes a third control unit, which is connected to the first control unit and the second control unit is also connected to the third control unit.

5. An AC test power supply system according to claim 4, characterized in that, It also includes a liquid crystal display unit and a user communication unit, both of which are connected to a third control unit.

6. An AC test power supply system according to claim 1, characterized in that, It also includes an optical fiber communication unit, which is connected to the second control unit.

7. An AC test power supply system according to claim 1, characterized in that, It also includes a high-precision acquisition unit, which is connected to the second control unit and three inverter units.

8. An AC test power supply system according to claim 7, characterized in that, The high-precision acquisition unit includes a first amplifier circuit, a second amplifier circuit, and a conversion circuit connected in sequence. The input terminal of the first amplifier circuit is connected to the output terminal of one of the three inverter units.

9. An AC test power supply system according to claim 8, characterized in that, The first amplification circuit includes cryogenic film resistors R1 and R2, and an instrumentation amplifier U1. The second amplification circuit includes a differential signal amplifier U2, and the conversion circuit includes an AD converter U3. Pin 1 of the cryogenic film resistor R1 is connected to the output L pin of one of the three inverter units. The output N pin of this inverter unit is connected to pin 1 of the cryogenic film resistor R2. Pin 2 of the cryogenic film resistor R1 is connected to pin 2 of the cryogenic film resistor R2 and grounded. Pin 3 of the cryogenic film resistor R1 is connected to the positive input pin of the instrumentation amplifier U1. Pin 3 of the cryogenic film resistor R2 is connected to the negative input pin of the instrumentation amplifier U1. The output pin of the instrumentation amplifier U1 is connected to the positive input pin of the differential signal amplifier U2 in the second amplification circuit. The positive output pin of the differential signal amplifier U2 is connected to the positive input terminal of the AD converter U3 in the conversion circuit, and the negative output pin of the differential signal amplifier U2 is connected to the negative input terminal of the AD converter U3.

10. An AC test power supply system according to claim 1, characterized in that, The circuit of the DC / DC isolation unit includes eight MOSFETs: Q5 to Q12, and a transformer. MOSFETs Q5 and Q6 are connected in series and in parallel with MOSFETs Q7 and Q8 (also connected in series). MOSFETs Q9 and Q10 are connected in series and in parallel with MOSFETs Q11 and Q12 (also connected in series). Pins 1 and 2 of the transformer are on the same side, and pins 3 and 4 are on the same side. Pin 1 of the transformer is connected to the end where MOSFETs Q5 and Q6 are connected. Pin 2 of the transformer is connected to the end where MOSFETs Q7 and Q8 are connected. Pin 4 of the transformer is connected to the end where MOSFETs Q9 and Q10 are connected. Pin 3 of the transformer is connected to the end where MOSFETs Q11 and Q12 are connected.

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