High-power inverter strong current test protection circuit

Abstract

The application discloses a strong current test protection circuit applied to a high-power converter, wherein the strong current test protection circuit is located between a three-phase alternating current power supply and a device to be tested and comprises an IGBT module, one end of the IGBT module being connected with the three-phase alternating current power supply and the other end of the IGBT module being connected with the device to be tested, the IGBT module being used for controlling on-off of the three-phase alternating current power supply and the device to be tested; a current sensor, the current sensor being connected with each phase of the three-phase alternating current power supply and being used for collecting each phase current of the three-phase alternating current power supply; and a control circuit, one end of the control circuit being connected with the current sensor and the other end of the control circuit being connected with the IGBT module, the control circuit being used for determining a control signal of the IGBT module according to the each phase current of the three-phase alternating current power supply and controlling switching of the IGBT module. The application solves the problem that the rear side of a high-power converter strong current test does not have a protection circuit in the prior art, the device to be tested is prone to failure, and the safety of the device is protected and the test safety is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the air conditioning technical field, and more particularly, to a strong current test protection circuit applied to a high-power converter. BACKGROUND

[0002] At present, in the design and function test process of high-power converters, frequency converters and inverters, a high-power AC / DC adjustable power supply is generally used as a test power supply for strong current test, and the device is provided with current limiting, voltage limiting and other related protections, and the main circuit breaker in the distribution box in front of the adjustable power supply also has overcurrent and short circuit protection functions.

[0003] However, since the power section of the device is generally hundreds of kilowatts, the power capacity of the power supply is also generally hundreds of kilowatts or even megawatts. Even if such a device has overcurrent and overvoltage protection, and the power supply circuit has a circuit breaker to limit the increase of current, when the device has a control, electrical main circuit, switch tube misdirecting and other test equipment out-of-control conditions on the back side, the current can easily increase sharply in a short time, causing the test equipment to be damaged in the time of mechanical action of the circuit breaker in the distribution box, execution of overcurrent protection of the adjustable power supply, and even the circuit breaker may be damaged. The damage of the new device under test due to the lack of timely protection will seriously affect the troubleshooting and development progress of the device.

[0004] At present, there is no effective solution to the problem that the back side of the strong current test of the high-power converter in the related art does not have a protection circuit, which can easily cause the device under test to fail. SUMMARY

[0005] The present application provides a strong current test protection circuit applied to a high-power converter, which at least solves the problem that the back side of the strong current test of the high-power converter in the prior art does not have a protection circuit, which can easily cause the device under test to fail.

[0006] To solve the above technical problems, according to an aspect of an embodiment of the present application, a strong current test protection circuit is provided, which is located between a three-phase AC power supply and a device under test, and includes: an IGBT module, one end of which is connected with the three-phase AC power supply, and the other end of which is connected with the device under test, for controlling the on-off of the three-phase AC power supply and the device under test; a current sensor, connected with each phase of the three-phase AC power supply, for collecting the current of each phase of the three-phase AC power supply; and a control circuit, one end of which is connected with the current sensor, and the other end of which is connected with the IGBT module, for determining the control signal of the IGBT module according to the current of each phase of the three-phase AC power supply, and controlling the switching of the IGBT module.

[0007] Further, the IGBT module comprises: a first IGBT module, a second IGBT module and a third IGBT module, which are connected with A phase, B phase and C phase of the three-phase alternating current power supply respectively; wherein each IGBT module comprises: two IGBT devices connected in parallel at the E terminal; an IGBT drive core, one end of which is connected with the IGBT device, and the other end of which is connected with the control circuit, for controlling the switching of the IGBT device according to the control signal of the IGBT module.

[0008] Further, the control circuit comprises: an operational amplifier module connected with the current sensor, for performing operational amplification on the current of each phase of the three-phase alternating current power supply, and determining the maximum current value of the three-phase alternating current; a comparison module connected with the operational amplifier module, for comparing the maximum current value with the overcurrent protection current value, determining whether the three-phase alternating current is overloaded, and outputting the control signal of the IGBT module according to the comparison result.

[0009] Further, the current sensor comprises: a first current sensor, a second current sensor and a third current sensor, which are connected with A phase, B phase and C phase of the three-phase alternating current power supply respectively; the operational amplifier module comprises: a first operational amplifier module, a second operational amplifier module and a third operational amplifier module, which are connected with the first current sensor, the second current sensor and the third current sensor respectively; wherein each operational amplifier module comprises: a first operational amplifier, a second operational amplifier and a third operational amplifier; the input end of the first operational amplifier is connected with the current sensor, and the output end is connected with the reverse input end of the second operational amplifier and the positive input end of the third operational amplifier respectively.

[0010] Further, the operational amplifier module further comprises: a first diode, one end of which is connected with the output end of the second operational amplifier, and the other end of which is connected with the input end of the comparison module; a second diode, one end of which is connected with the output end of the third operational amplifier, and the other end of which is connected with the input end of the comparison module.

[0011] Further, the comparison module comprises: a comparator, the first input end of which is connected with the output end of each operational amplifier module, and the second input end of which is connected with the output end of the overcurrent protection setting circuit, for outputting the comparison result signal of the maximum current value and the overcurrent protection current value; a logic circuit, one end of which is connected with the output end of the comparator, and the other end of which is connected with the IGBT module, for outputting the control signal of the IGBT module according to the comparison result signal.

[0012] Further, the overcurrent protection setting circuit comprises: a first direct current power supply, an adjustable resistor and a first resistor connected in sequence; wherein the connection point between the adjustable resistor and the first resistor is connected with the second input end of the comparator; the adjustable resistor adjusts the size of the overcurrent protection current value by changing the resistance value.

[0013] Further, the logic circuit comprises: an inverter connected with the output end of the comparator; an AND gate circuit, a first input end of which is connected with the inverter, a second input end of which is connected with the second DC power supply, and an output end of which is connected with the IGBT module, for outputting a low level to control the IGBT module to be opened in the case of overcurrent of the three-phase AC power supply, and outputting a high level to control the IGBT module to be closed in the case of normality of the three-phase AC power supply.

[0014] Further, the logic circuit further comprises: a self-locking circuit comprising a second resistor, a third resistor and a triode, wherein one end of the second resistor is connected with the second DC power supply, the other end is connected with the second input end of the AND gate circuit, the e pole of the triode is connected with the second input end of the AND gate circuit, and the b pole of the triode is connected with the output end of the AND gate circuit through the third resistor.

[0015] Further, the logic circuit further comprises: a self-locking circuit comprising a second resistor, a third resistor and a triode, wherein one end of the second resistor is connected with the second DC power supply, the other end is connected with the second input end of the AND gate circuit, the e pole of the triode is connected with the second input end of the AND gate circuit, and the b pole of the triode is connected with the output end of the AND gate circuit through the third resistor.

[0016] In the application, in order to improve the problem that the back side of the high-power converter strong current test does not have a protection circuit, and the to-be-tested equipment is prone to failure, a high-power converter strong current test protection circuit is provided between the three-phase AC power supply and the to-be-tested equipment, the current sensor is used to collect the current of each phase of the three-phase AC power supply, the control circuit determines the control signal of the IGBT module according to the current of each phase of the three-phase AC power supply, and the switching of the IGBT module is controlled. When the to-be-tested equipment has a sharp increase in current in a short time, the circuit can cut off the power supply main loop in a short time after reaching the protection limit value, so as to protect the equipment safety and improve the test safety. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is an electrical schematic diagram according to the strong current protection scheme in the prior art;

[0018] Figure 2 is an optional electrical schematic diagram of the strong current protection scheme according to the embodiment of the application;

[0019] Figure 3 is an optional circuit diagram of the strong current protection circuit according to the embodiment of the application;

[0020] Figure 4 is an optional circuit diagram of the control circuit according to the embodiment of the application. DETAILED DESCRIPTION

[0021] The exemplary embodiments will be described in detail herein with reference to the attached drawings. The description below refers to the accompanying drawings, which show, by way of example, specific embodiments with which the inventive concept can be practiced. The same numbers in different drawings identify the same or similar elements. These embodiments are described in sufficient detail to enable those skilled in the art to practice the inventive concept. Other embodiments can be utilized and structural, and logical changes can be made without departing from the scope of the present inventive concept. The following detailed description is, therefore, not to be taken in a limiting sense, as the scope of the inventive concept is defined by the appended claims.

[0022] Embodiment 1

[0023] In the conventional application of electrical scheme, as Figure 1 , the three-phase AC power grid is connected to the input side of the three-phase adjustable power supply through the main circuit breaker K, the power supply state of the three-phase adjustable power supply is controlled by the main circuit breaker K, and then the input interface of the high-power device to be tested is connected to the output side of the three-phase adjustable power supply, and various working states of the simulated AC power grid and power supply control are provided by the three-phase adjustable power supply.

[0024] In the design scheme of the present application, the main circuit connection between devices is as Figure 2 , a test protection module is installed between the three-phase adjustable power supply and the device to be tested, the A, B, and C phases of the three-phase input side of the test protection module are connected to the A, B, and C phases of the three-phase adjustable power supply output side, and the A, B, and C of the test protection module output side are connected to the A, B, and C of the input side of the device to be tested.

[0025] In the preferred embodiment 1 of the present application, a strong electric test protection circuit is provided, in particular, Figure 3 An alternative circuit diagram of the protection circuit is shown, as Figure 3 The protection circuit is located between the three-phase AC power supply and the device to be tested, and includes:

[0026] An IGBT module is connected to one end of the three-phase AC power supply and the other end of the device to be tested, for controlling the on-off of the three-phase AC power supply and the device to be tested;

[0027] A current sensor is connected to each phase of the three-phase AC power supply for collecting the current of each phase of the three-phase AC power supply;

[0028] A control circuit is connected to one end of the current sensor and the other end of the IGBT module, for determining the control signal of the IGBT module according to the current of each phase of the three-phase AC power supply, and controlling the switching of the IGBT module.

[0029] In the above embodiment, in order to improve the problem that the rear side of the high-power converter strong current test does not have a protection circuit, which easily causes the fault of the device to be tested, a protection circuit for high-power converter strong current test is provided, which is located between the three-phase alternating current power supply and the device to be tested, the current sensor is used to collect the current of each phase of the three-phase alternating current power supply, the control circuit determines the control signal of the IGBT module according to the current of each phase of the three-phase alternating current power supply, and the switch of the IGBT module is controlled. When the current of the device to be tested increases sharply in a short time, the circuit can cut off the power supply main circuit in a short time after reaching the protection limit value, so as to protect the safety of the device and improve the test safety.

[0030] As shown in Figure 3 , the IGBT module includes: a first IGBT module, a second IGBT module and a third IGBT module, which are connected with the A phase, the B phase and the C phase of the three-phase alternating current power supply respectively; wherein each IGBT module includes: two IGBT devices connected in parallel at the E end; an IGBT drive core, one end of which is connected with the IGBT device, and the other end of which is connected with the control circuit, which is used to control the switch of the IGBT device according to the control signal of the IGBT module.

[0031] In the test protection module, as shown in Figure 3 , it mainly includes a current sensor, a control circuit, an IGBT drive core and an IGBT. The current sensor is installed at the input side of the main circuit of each phase, which is used to detect the size of the current value of each phase. The rear side of the current sensor in the main circuit is provided with two IGBTs for controlling the on-off state of the main circuit. The main circuit of each phase is connected to the output side after passing through the IGBT. The current signal sampling value output by the current sensor is input into the control circuit of the protection circuit, which is converted into the on-off state signal of the IGBT, i.e. the control signal, after being processed by the control circuit, and is output to the IGBT drive core of each phase. The drive core processes and amplifies the on-off state signal of the IGBT, and then controls the on-off state of the IGBT.

[0032] Figure 4 The circuit diagram of the control circuit in the protection circuit is shown in Figure 4 , the control circuit includes: an operational amplifier module connected with the current sensor, which is used to amplify the current of each phase of the three-phase alternating current power supply, and determine the maximum current value of the three-phase alternating current; a comparison module connected with the operational amplifier module, which is used to compare the maximum current value with the overcurrent protection current value, determine whether the three-phase alternating current is overloaded, and output the control signal of the IGBT module according to the comparison result.

[0033] Corresponding to the three-phase alternating current power supply, the current sensor comprises: a first current sensor (current sensor A), a second current sensor (current sensor B) and a third current sensor (current sensor C), which are connected with A phase, B phase and C phase of the three-phase alternating current power supply respectively; the operational amplifier module comprises: a first operational amplifier module, a second operational amplifier module and a third operational amplifier module, which are connected with the first current sensor, the second current sensor and the third current sensor respectively; wherein each operational amplifier module comprises: a first operational amplifier (operational amplifier 1), a second operational amplifier (operational amplifier 2) and a third operational amplifier (operational amplifier 3); the input end of the first operational amplifier is connected with the current sensor, and the output end is connected with the reverse input end of the second operational amplifier and the forward input end of the third operational amplifier respectively.

[0034] The operational amplifier module further comprises: a first diode D1, one end of which is connected with the output end of the second operational amplifier, and the other end is connected with the input end of the comparison module; a second diode D2, one end of which is connected with the output end of the third operational amplifier, and the other end is connected with the input end of the comparison module.

[0035] The comparison module comprises: a comparator, a first input end of which is connected with the output end of each operational amplifier module, and a second input end of which is connected with the output end of the overcurrent protection setting circuit, for outputting a comparison result signal of the maximum current value and the overcurrent protection current value; a logic circuit, one end of which is connected with the output end of the comparator, and the other end of which is connected with the IGBT module, for outputting a control signal of the IGBT module according to the comparison result signal.

[0036] The overcurrent protection setting circuit comprises: a first direct current power supply, an adjustable resistor and a first resistor R7 connected in sequence; wherein the connection point between the adjustable resistor and the first resistor R7 is connected with the second input end of the comparator, for inputting a preset voltage value to the comparator.

[0037] The logic circuit comprises: an inverter, which is connected with the output end of the comparator; an AND gate circuit, a first input end of which is connected with the inverter, a second input end of which is connected with a second direct current power supply, and an output end of which is connected with the IGBT module, for outputting a low level to control the IGBT module to be opened in the case of overcurrent of the three-phase alternating current power supply, and outputting a high level to control the IGBT module to be closed in the case of normal of the three-phase alternating current power supply.

[0038] The logic circuit further comprises: a self-locking circuit comprising a second resistor R11, a third resistor R13 and a triode; wherein one end of the second resistor R11 is connected with the second direct current power supply, the other end is connected with the second input end of the AND gate circuit, the e pole of the triode is connected with the second input end of the AND gate circuit, and the b pole of the triode is connected with the output end of the AND gate circuit through the third resistor R13.

[0039] The protection circuit further comprises a reset circuit comprising a reset switch and a fourth resistor R12; wherein one end of the reset switch is connected to the b electrode of the triode, and the other end is connected to the second DC power supply through the fourth resistor R12.

[0040] The protection circuit of the high-power converter strong current test is connected between a three-phase adjustable power supply for testing and a device to be tested, uses a three-phase alternating current sensor to collect currents of each phase, amplifies the collected current signals, compares the amplified signals with a set voltage through a voltage comparator, and turns off all main circuit IGBT modules and disconnects the device to be tested from the main circuit when the current of any phase exceeds the set value, thereby protecting the device to be tested, the three-phase adjustable power supply, and the researchers.

[0041] As Figure 4 After the current sampling signal of the A-phase current sensor is amplified by the first-stage operational amplifier 1, the signal is input into the second-stage operational amplifier 2 and the operational amplifier 3 for second-stage amplification. After the operational amplifier 2 and the operational amplifier 3, the current sampling signal is rectified into a forward voltage signal, and then flows through the diode D1 and the diode D2. The B-phase and C-phase current sampling circuits in the first-stage amplification circuit and the second-stage amplification circuit are the same as the A-phase. The three-phase current sampling signals are connected in parallel after the diodes, and then input into the voltage comparator for comparison with the set voltage. The overcurrent state signal is output from the comparator, inverted by the inverter NOT gate, input into the AND gate logic circuit, and then output to the IGBT to control the switching state of the IGBT. The specific process is as follows:

[0042] After the three-phase current sampling signals are amplified by the first-stage and second-stage amplification circuits and connected in parallel after the diodes D1 and D2, the signal input into the comparator is the maximum value signal of the three-phase currents, and the voltage signal at the connection point of the resistor RX and the resistor R7 is input into the + input end of the comparator. The overcurrent protection current value can be adjusted by adjusting the variable resistor RX. In the normal non-overcurrent state, the voltage value of the three-phase current sampling signals is less than the set value of RX and R7, the comparator outputs a low level, which is inverted to a high level by the inverter NOT gate, and then the AND gate is self-locked, outputting a high level. The IGBT is turned on by the IBGT drive core, and the main circuit is in a closed state.

[0043] When the short circuit or other problems of the device under test occur at a moment, any one phase current exceeds the set value, the current sampling signal is sent into the comparator in parallel after the first and second amplification, the voltage at the back side of R8 exceeds the set value of RX and R7, the output of the comparator is high level, the low level is obtained after the diode and the inverter, the upper pin of the AND gate is low level, the output of the AND gate is low level, the transistor is opened, the lower pin of the AND gate is pulled to low level by the opened transistor to complete self-locking, the IGBT drive core receives the low level signal, all IGBTs are turned off at a moment, the main circuit is disconnected, the upper pin of the AND gate is restored to high level;

[0044] When the tester performs the loop detection, it is determined that the power can be turned on again, the reset switch K1 is pressed, the transistor control end is pulled up to high level, the transistor is turned off, the lower pin of the AND gate is pulled back to high level by R11, the output end of the AND gate outputs high level, the IGBT drive core receives the high level signal, all IGBTs are turned on, and the main circuit returns to the conduction state.

[0045] The beneficial effects of the scheme include:

[0046] 1. When the device under test has a sharp increase in current in a short time, the circuit can cut off the power supply main circuit in a short time after reaching the protection limit value, and the safety of the device is protected.

[0047] 2. In the design verification stage, the test damage of the device is greatly reduced, and the device under test is quickly cut off after failure, so that the device is not damaged and the test failure reason is easy to find.

[0048] 3. The device under test is quickly cut off from the power supply circuit, the main power device is protected from being damaged, and the maintenance time is reduced.

[0049] 4. In the development and test process of such high-power strong electric equipment, once the main circuit fails, accidents are prone to occur, and even the design of major equipment damage, personnel injury and other situations, the test safety can be greatly improved through the scheme.

[0050] Other embodiments of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. This application is intended to cover any variations, uses or adaptive changes of the application following in general the principles of the application and including such

[0051] It should be understood that the application is not limited to the precise construction which has been described above and which shown in the drawings, and that various modifications and changes can be made by those skilled in the art without departing from the scope of the application. The scope of the application should be limited only by the appended claims.

Claims

1. A strong current test protection circuit, characterized by, Between a three-phase alternating current power supply and a device to be tested, comprising: an IGBT module, one end of which is connected with the three-phase alternating current power supply and the other end of which is connected with the device to be tested, for controlling the on-off of the three-phase alternating current power supply and the device to be tested; a current sensor, connected with each phase of the three-phase alternating current power supply, for collecting the current of each phase of the three-phase alternating current power supply; a control circuit, one end of which is connected with the current sensor and the other end of which is connected with the IGBT module, for determining the control signal of the IGBT module according to the current of each phase of the three-phase alternating current power supply, and controlling the switch of the IGBT module; the IGBT module comprises: a first IGBT module, a second IGBT module and a third IGBT module, which are connected with the A phase, the B phase and the C phase of the three-phase alternating current power supply respectively; wherein each IGBT module comprises: two IGBT devices connected in parallel at the E terminal; an IGBT drive core, one end of which is connected with the IGBT device and the other end of which is connected with the control circuit, for controlling the switch of the IGBT device according to the control signal of the IGBT module; the control circuit comprises: an operational amplifier module, connected with the current sensor, for performing operational amplification on the current of each phase of the three-phase alternating current power supply, and determining the maximum current value of the three-phase alternating current; a comparison module, connected with the operational amplifier module, for comparing the maximum current value with an overcurrent protection current value, determining whether the three-phase alternating current is overloaded, and outputting the control signal of the IGBT module according to the comparison result; the comparison module comprises: a comparator, a first input end of which is connected with the output end of each operational amplifier module and a second input end of which is connected with the output end of an overcurrent protection setting circuit, for outputting the comparison result signal of the maximum current value and the overcurrent protection current value; a logic circuit, one end of which is connected with the output end of the comparator and the other end of which is connected with the IGBT module, for outputting the control signal of the IGBT module according to the comparison result signal; the logic circuit comprises: an inverter, the input end of which is connected with the output end of the comparator; an AND gate circuit, a first input end of which is connected with the output end of the inverter, a second input end of which is connected with a second DC power supply, and an output end of which is connected with the IGBT module, for outputting a low level to control the IGBT module to be disconnected in the case of overcurrent of the three-phase alternating current power supply, and outputting a high level to control the IGBT module to be closed in the case of normality of the three-phase alternating current power supply; a self-locking circuit, comprising a second resistor, a third resistor and a transistor; wherein one end of the second resistor is connected with the second DC power supply and the other end of the second resistor is connected with the second input end of the AND gate circuit, the e terminal of the transistor is connected with the second input end of the AND gate circuit, and the b terminal of the transistor is connected with the output end of the AND gate circuit through the third resistor; a reset circuit, comprising a reset switch and a fourth resistor; wherein one end of the reset switch is connected with the b terminal of the transistor and the other end of the reset switch is connected with the second DC power supply through the fourth resistor.

2. The protection circuit of claim 1, wherein The current sensor comprises a first current sensor, a second current sensor and a third current sensor, which are connected with A phase, B phase and C phase of the three-phase alternating current power supply respectively; The operational amplifier module comprises a first operational amplifier module, a second operational amplifier module and a third operational amplifier module, which are connected with the first current sensor, the second current sensor and the third current sensor respectively; wherein each operational amplifier module comprises: a first operational amplifier, a second operational amplifier and a third operational amplifier; The input end of the first operational amplifier is connected with the current sensor, and the output end is connected with the reverse input end of the second operational amplifier and the forward input end of the third operational amplifier respectively.

3. The protection circuit of claim 2, wherein, The operational amplifier module further comprises: a first diode, one end of which is connected with the output end of the second operational amplifier, and the other end is connected with the input end of the comparison module; a second diode, one end of which is connected with the output end of the third operational amplifier, and the other end is connected with the input end of the comparison module.

4. The protection circuit of claim 1, wherein, The overcurrent protection setting circuit comprises: a first direct current power supply, an adjustable resistor and a first resistor connected in sequence; wherein the connection point between the adjustable resistor and the first resistor is connected with the second input end of the comparator; the adjustable resistor adjusts the size of the overcurrent protection current value by changing the resistance value.

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