A phase loss protection device for an inverter and an inverter

Abstract

The present invention discloses a phase loss protection device and an inverter for an inverter. The device includes: a soft start unit that provides a trigger signal, where the trigger signal is a signal for triggering a drive module; a phase loss detection unit that detects whether a three-phase AC power supply is missing a phase and obtains a phase loss fault output signal; and determines a drive signal for the drive module based on the phase loss fault output signal and the trigger signal; a three-phase AC power supply that is the power supply input to a rectification unit; and a drive module that controls the operation of a thyristor module according to the drive signal. With this solution, by using a hardware circuit to detect a phase loss in a three-phase power grid, the detection accuracy can be improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of frequency converters, and particularly relates to a phase loss protection device and a frequency converter for a frequency converter, and more particularly to a phase loss protection device applied to a high-power frequency converter and a frequency converter having the device. Background Art

[0002] During the high-voltage and complex operation process of a three-phase power grid, it is easy to cause a phase loss in the power grid. If the phase loss fault fails to be detected and found in time or the detection and elimination time is relatively long, it will seriously affect the reliable operation of the frequency converter, damage related power equipment such as the subsequent rectifier bridge, and cause serious economic losses. However, in related solutions, the power grid phase loss fault detection circuit mainly uses software or a combination of software and hardware to detect the power grid phase loss fault, and the detection accuracy is relatively poor.

[0003] The above content is only used to assist in understanding the technical solution of the present invention, and does not represent an admission that the above content is prior art. Summary of the Invention

[0004] The purpose of the present invention is to provide a phase loss protection device and a frequency converter for a frequency converter, so as to solve the problem of relatively poor detection accuracy in detecting the phase loss of a three-phase power grid by using software or a combination of software and hardware, and achieve the effect of improving the detection accuracy by using a hardware circuit to detect the phase loss of a three-phase power grid.

[0005] In a phase loss protection device for a frequency converter provided by the present invention, the frequency converter includes a rectification unit and a soft start unit; the rectification unit includes a semi-controlled rectifier bridge; the semi-controlled rectifier bridge includes a thyristor module and a drive module of the thyristor module; the phase loss protection device for the frequency converter includes a phase loss detection unit; wherein, the soft start unit is configured to provide a trigger signal; the trigger signal is a signal for triggering the drive module; the phase loss detection unit is configured to detect whether a three-phase AC power supply is missing a phase to obtain a phase loss fault output signal; and determine a drive signal of the drive module according to the phase loss fault output signal and the trigger signal; the three-phase AC power supply is a power supply input to the rectification unit; the drive module is configured to control the operation of the thyristor module according to the drive signal.

[0006] In some embodiments, the phase loss detection unit includes: a three-phase power sampling module, a fault judgment module, and a comparison output module; wherein, the phase loss detection unit detects whether there is a phase loss in a three-phase AC power supply to obtain a phase loss fault output signal; and determines a drive signal of the drive module according to the phase loss fault output signal and the trigger signal, including: the three-phase power sampling module is configured to detect an isolation voltage of the phase voltage of each phase of the three-phase AC power supply, and compare the isolation voltage of the phase voltage of each phase of the three-phase AC power supply with a first reference voltage to obtain a first comparison result; the fault judgment module is configured to compare the first comparison result with a second reference voltage to obtain a second comparison result as a defect fault output signal indicating whether there is a phase loss in the three-phase AC power supply; the comparison output module is configured to perform an AND operation on the phase loss fault output signal and the trigger signal to obtain an operation result as the drive signal of the drive module.

[0007] In some embodiments, the three-phase power sampling module includes: a first pull-up module, a second pull-up module, a first voltage dividing module, an A-phase power sampling branch, a B-phase power sampling branch, and a C-phase power sampling branch; wherein, a first DC power supply is respectively connected to the A-phase power sampling branch, the B-phase power sampling branch, and the C-phase power sampling branch after passing through the first pull-up module; the first DC power supply also provides a first reference voltage for the A-phase power sampling branch, the B-phase power sampling branch, and the C-phase power sampling branch respectively after passing through the first voltage dividing module; a second DC power supply performs a pull-up process on the first comparison results output by the A-phase power sampling branch, the B-phase power sampling branch, and the C-phase power sampling branch respectively after passing through the second pull-up module; wherein, the common ends of the A-phase power sampling branch, the B-phase power sampling branch, and the C-phase power sampling branch are connected.

[0008] In some embodiments, the A-phase power sampling branch, the B-phase power sampling branch, and the C-phase power sampling branch have the same structure.

[0009] In some embodiments, the A-phase electrical sampling branch includes: a first current limiting module, a first rectifying module, a first isolation module, and a first comparison module; wherein, the A-phase alternating current in the three-phase alternating current is output to the in-phase input terminal of the first comparison module after passing through the first current limiting module, the first rectifying module, and the first isolation module; the in-phase input terminal of the first comparison module is connected to the first pull-up module; the voltage dividing point of the first voltage dividing module is connected to the anti-phase input terminal of the first comparison module; the output terminal of the first comparison module is output to the input terminal of the fault judgment module; wherein, one end of the first rectifying module serves as the first common terminal among the common terminals of the A-phase electrical sampling branch, the B-phase electrical sampling branch, and the C-phase electrical sampling branch; the voltage dividing point of the first voltage dividing module serves as the second common terminal among the common terminals of the A-phase electrical sampling branch, the B-phase electrical sampling branch, and the C-phase electrical sampling branch; the output terminal of the first comparison module serves as the third common terminal among the common terminals of the A-phase electrical sampling branch, the B-phase electrical sampling branch, and the C-phase electrical sampling branch, and also serves as the output terminal of the three-phase electrical sampling module.

[0010] In some embodiments, the first rectifying module includes: a first rectifying diode; the first isolation module includes: a first optocoupler; the anode of the first rectifying diode is connected to the cathode of the diode side in the first optocoupler and serves as the first common terminal.

[0011] In some embodiments, the fault judgment module includes: a switching tube module, a comparison module, and a charge and discharge module; wherein, the output terminal of the three-phase electrical sampling module is output to the anti-phase input terminal of the comparison module and connected to the charge and discharge module after passing through the switching tube module; the in-phase input terminal of the comparison module serves as the input terminal of the second reference voltage; the output terminal of the comparison module can output a defect fault output signal indicating whether the three-phase AC power supply is missing a phase.

[0012] In some embodiments, the switching tube module includes: a third pull-up module and a triode; the comparison module includes: a comparator and a second voltage dividing module; the charge and discharge module includes: a capacitor module and a resistor module; wherein, the output terminal of the three-phase electrical sampling module is connected to the base of the triode; a first DC power supply is connected to the collector of the triode after passing through the third pull-up module; the emitter of the triode is connected to the anti-phase input terminal of the comparator and also connected to the parallel-connected resistor module and capacitor module; the voltage dividing point of the second voltage dividing module is connected to the in-phase input terminal of the comparator.

[0013] In some embodiments, the comparison output module includes: a first AND gate module, a second AND gate module, and a third AND gate module; wherein, a first input terminal of the first AND gate module is connected to an output terminal of the fault judgment circuit; a second input terminal of the first AND gate module is connected to an output terminal of the soft start unit; an output terminal of the first AND gate module outputs a drive signal for controlling a first thyristor in the thyristor module; a first input terminal of the second AND gate module is connected to the output terminal of the fault judgment circuit; a second input terminal of the second AND gate module is connected to the output terminal of the soft start unit; an output terminal of the second AND gate module outputs a drive signal for controlling a second thyristor in the thyristor module; a first input terminal of the third AND gate module is connected to the output terminal of the fault judgment circuit; a second input terminal of the third AND gate module is connected to the output terminal of the soft start unit; an output terminal of the third AND gate module outputs a drive signal for controlling a third thyristor in the thyristor module.

[0014] Matched with the above device, on the other hand, the present invention provides an inverter, including: the phase loss protection device of the inverter described above.

[0015] Thus, the solution of the present invention forms a hardware circuit by adopting a three-phase power sampling detection circuit, a fault judgment circuit, and a comparison output protection circuit to detect the phase loss fault when the input three-phase power supply is missing a phase. When a three-phase phase loss occurs, a phase loss protection signal is output to protect the circuit after a phase loss fault occurs in the power grid; thereby, by adopting a hardware circuit for three-phase power grid phase loss detection, the detection accuracy can be improved.

[0016] Other features and advantages of the present invention will be described in the following description, and part of them will be obvious from the description, or will be understood by implementing the present invention.

[0017] Next, through the drawings and embodiments, the technical solutions of the present invention will be further described in detail. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 FIG. is a schematic structural diagram of an embodiment of the phase loss protection device of the inverter proposed by the solution of the present invention;

[0019] Figure 2 FIG. is a schematic structural diagram of an embodiment of the soft start system of the inverter with a phase loss protection device proposed by the solution of the present invention;

[0020] Figure 3 FIG. is a schematic structural diagram of an embodiment of the phase loss protection system applied to the soft start system of the inverter proposed by the solution of the present invention;

[0021] Figure 4Schematic diagram of the working process of an embodiment of the phase loss protection device proposed by the solution of the present invention. Detailed implementation manners

[0022] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments of the present invention and the corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0023] According to an embodiment of the present invention, a phase loss protection device for an inverter is provided. Refer to Figure 1 Schematic diagram of the structure of an embodiment of the device of the present invention as shown. The inverter includes a rectification unit and a soft start unit. The soft start unit is, for example, a soft start control system. The rectification unit includes a semi-controlled rectifier bridge. The semi-controlled rectifier bridge includes a thyristor module (such as thyristors D1, D2, D3), and a drive module of the thyristor module (i.e., a thyristor drive module). The phase loss protection device of the inverter includes a phase loss detection unit (such as a phase loss detection system).

[0024] Wherein, the soft start unit is configured to provide a trigger signal. The trigger signal is a signal for triggering the drive module.

[0025] The phase loss detection unit is configured to detect whether the three-phase AC power supply is out of phase, and obtain a phase loss fault output signal. And, based on the phase loss fault output signal and the trigger signal, determine the drive signal of the drive module. The three-phase AC power supply is the power supply input to the rectification unit.

[0026] The drive module is configured to control the operation of the thyristor module according to the drive signal.

[0027] The solution of the present invention provides a low-cost and highly reliable detection device to achieve phase loss protection, specifically a phase loss protection device applied to a high-power inverter, which can monitor the phase loss situation of the power grid in real time and perform phase loss protection on the circuit after a phase loss fault occurs in the power grid.

[0028] In some implementation manners, the phase loss detection unit includes a three-phase power sampling module, a fault judgment module, and a comparison output module. The three-phase power sampling module is, for example, a three-phase power sampling detection circuit, the fault judgment module is, for example, a fault judgment circuit, and the comparison output module is, for example, a comparison output protection circuit.

[0029] Among them, the phase loss detection unit detects whether there is a phase loss in the three-phase AC power supply to obtain a phase loss fault output signal. And, according to the phase loss fault output signal and the trigger signal, the drive signal of the drive module is determined, including:

[0030] The three-phase power sampling module is configured to detect the isolation voltage of the phase voltage of each phase of the three-phase AC power supply, and compare the isolation voltage of the phase voltage of each phase of the three-phase AC power supply with a first reference voltage to obtain a first comparison result. The isolation voltage of the phase voltage of each phase of the three-phase AC power supply is the voltage output after passing through an optocoupler after the optocoupler is turned on, and is pulled up to 15V after being turned on.

[0031] The fault judgment module is configured to compare the first comparison result with a second reference voltage to obtain a second comparison result as the defect fault output signal indicating whether there is a phase loss in the three-phase AC power supply.

[0032] The comparison output module is configured to perform an AND operation on the phase loss fault output signal and the trigger signal to obtain an operation result as the drive signal of the drive module.

[0033] The solution of the present invention uses three circuits, namely a three-phase power sampling detection circuit, a fault judgment circuit, and a comparison output protection circuit, to detect and protect against phase loss faults when the input three-phase power supply is missing a phase. The structure is simple and the detection is accurate. In the case of a three-phase power phase loss, the thyristor drive signal is blocked through the protection circuit to achieve the phase loss protection function.

[0034] Figure 2 It is a schematic structural diagram of an embodiment of a frequency converter soft start system with a phase loss protection device proposed for the solution of the present invention. As Figure 2As shown, the soft start system of the frequency converter with a phase loss protection device includes a rectification unit, a bus capacitor unit, a phase loss detection system, a soft start control system, and a thyristor drive module. A three-phase AC power supply such as 380V AC is output to the bus capacitor unit after passing through the rectification unit. The rectification unit includes a semi-controlled rectifier bridge. The semi-controlled rectifier bridge includes thyristors D1, D2, D3, diodes D4, D5, and D6. The thyristor drive module is connected to thyristors D1, D2, and D3. The phase loss detection system includes a phase loss detection module and a phase loss protection module, and the phase loss detection module and the phase loss protection module are connected to the thyristor drive module. The soft start control system includes a trigger signal generation module, a phase shift signal generation module, a synchronization signal generation module, and a voltage sampling module. The voltage sampling module can sample the bus voltage of the bus capacitor voltage and the line voltage or phase voltage of the motor. The voltage sampling module is output to the trigger signal generation module after passing through the phase shift signal generation module and the synchronization signal generation module respectively. The trigger signal generation module is output to the phase loss protection module. The bus capacitor unit includes a bus capacitor and a voltage equalizing resistor.

[0035] See Figure 2 In the example shown, in the soft start system of a high-power frequency converter, a three-phase semi-controlled rectification topology composed of thyristors and diodes is adopted. In this soft start device, a hardware control method is used. The trigger pulses are generated through a voltage sampling module, a phase shift signal generation module, a synchronization signal generation module, and a trigger signal generation module. When the trigger angle changes from 180° to 0°, the trigger pulse width continuously increases, that is, the conduction interval continuously becomes larger, and the bus voltage continuously rises. When the trigger angle decreases to 0°, the soft start of the frequency converter is completed.

[0036] Collect the three-phase input line voltages U UV 、U VW 、U WU , and obtain their reverse values U VU 、U WV 、U UW ; U UW 、U VU 、U WV are respectively compared with the zero point to obtain the synchronization signals of the three phases of U, V, and W. This synchronization signal is the 180° trigger interval of each phase thyristor; U UV and U UW 、U VU and U VW 、U WU and U WV are taken in pairs, and the maximum value of each pair is taken to generate the saddle wave signals of the three phases of U, V, and W respectively; the saddle wave of each phase and the bus sampling voltage U DCCompare to generate a phase-shifted signal; the effective interval of the phase-shifted signal increases as the bus voltage rises; the synchronization signal of each phase is ANDed with the phase-shifted signal to generate the trigger signal for that phase. The larger the interval of this trigger signal, the higher the value of the bus voltage is reflected; to make the thyristor conduct stably, multi-pulse triggering is required when triggering the thyristor. Use a NOT gate or an operational amplifier to generate a self-excited oscillation clock, and AND this clock signal with the trigger signal to generate a control signal; in the soft start system used, the control signal output by this system can be directly input into the thyristor drive module to generate a drive signal to directly drive the thyristor. However, in the present invention, the control signal output by this system needs to be ANDed with the phase-loss fault signal FO. If there is no phase-loss fault (i.e., the phase-loss fault signal FO is a high-level signal), this control signal is normally output and input into the thyristor drive module to generate a drive signal to directly drive the thyristor. If a phase-loss fault occurs (i.e., the phase-loss fault signal FO is a low-level signal), this control signal cannot be output, which is equivalent to the thyristor drive module being unable to generate a drive signal to drive the thyristor.

[0037] In the three-phase AC phase-loss detection circuit in related solutions, the AC is rectified, divided in voltage, and then compared with a reference voltage through a comparator to output the phase-loss detection result to related circuits, such as for use by an MCU / DSP control unit, and is implemented through a combination of software and hardware. This detection circuit will have the problem of inaccurate detection. In the solution of the present invention, the phase-loss protection device applied to a high-power frequency converter completely uses a hardware circuit method to implement phase-loss detection and protection, and the circuit is simple and easy to implement. For the soft start system of the frequency converter with a phase-loss protection device, when a three-phase phase-loss occurs, a phase-loss protection signal is output to block the drive signal of the thyristor, so that all three thyristors do not conduct, and it can monitor the phase-loss situation of the power grid in real time and perform phase-loss protection on the circuit after a phase-loss fault occurs in the power grid.

[0038] In some embodiments, the three-phase electricity sampling module includes: a first pull-up module, a second pull-up module, a first voltage-dividing module, an A-phase electricity sampling branch, a B-phase electricity sampling branch, and a C-phase electricity sampling branch. The first pull-up module, such as resistor R4. The first voltage-dividing module, such as resistors R5 and R6. The second pull-up module, such as resistor R11.

[0039] Among them, a first DC power supply, such as a +15V power supply, after passing through the first pull-up module, is respectively connected to the A-phase electricity sampling branch, the B-phase electricity sampling branch, and the C-phase electricity sampling branch.

[0040] The first DC power supply also provides a first reference voltage for the A-phase electricity sampling branch, the B-phase electricity sampling branch, and the C-phase electricity sampling branch after passing through the first voltage-dividing module.

[0041] The second DC power supply, such as the +5V power supply, after passing through the second pull-up module, performs pull-up processing on the first comparison results output by the A-phase electrical sampling branch, the B-phase electrical sampling branch, and the C-phase electrical sampling branch respectively.

[0042] Among them, the common ends of the A-phase electrical sampling branch, the B-phase electrical sampling branch, and the C-phase electrical sampling branch are connected.

[0043] In some embodiments, the structures of the A-phase electrical sampling branch, the B-phase electrical sampling branch, and the C-phase electrical sampling branch are the same.

[0044] In some embodiments, the A-phase electrical sampling branch includes: a first current limiting module, a first rectification module, a first isolation module, and a first comparison module. The first current limiting module is, for example, resistor R1, the first rectification module is, for example, diode D1, the first isolation module is, for example, optocoupler OC1, and the first comparison module is, for example, comparator U1.

[0045] Among them, the A-phase alternating current in the three-phase alternating current is output to the non-inverting input terminal of the first comparison module after passing through the first current limiting module, the first rectification module, and the first isolation module.

[0046] The non-inverting input terminal of the first comparison module is connected to the first pull-up module. The voltage dividing point of the first voltage dividing module, such as the common end of resistor R5 and resistor R6, is connected to the inverting input terminal of the first comparison module. The output terminal of the first comparison module is output to the input terminal of the fault judgment module.

[0047] Among them, one end of the first rectification module serves as the first common end among the common ends of the A-phase electrical sampling branch, the B-phase electrical sampling branch, and the C-phase electrical sampling branch. The voltage dividing point of the first voltage dividing module serves as the second common end among the common ends of the A-phase electrical sampling branch, the B-phase electrical sampling branch, and the C-phase electrical sampling branch. The output terminal of the first comparison module serves as the third common end among the common ends of the A-phase electrical sampling branch, the B-phase electrical sampling branch, and the C-phase electrical sampling branch, and also serves as the output terminal of the three-phase electrical sampling module.

[0048] In some embodiments, the first rectification module includes: a first rectification diode, such as diode D1. The first isolation module includes: a first optocoupler, such as optocoupler OC1.

[0049] The anode of the first rectification diode is connected to the cathode of the diode side in the first optocoupler and serves as the first common end.

[0050] Figure 3 It is a schematic structural diagram of an embodiment of a phase loss protection system applied to a soft start system of a frequency converter proposed by the solution of the present invention. AsFigure 3 As shown, a phase loss protection system applied to the soft start system of a frequency converter, that is Figure 2 the phase loss detection system shown. In the phase loss detection system, the phase loss detection module includes: a three-phase power sampling detection circuit and a fault judgment circuit. The phase loss protection module includes: comparison output protection.

[0051] Among them, the three-phase power sampling detection circuit includes: an A-phase power sampling detection branch, a B-phase power sampling detection branch, a C-phase power sampling detection branch, resistor R4, resistor R5, resistor R6, resistor R11. The A-phase power sampling detection branch includes: resistor R1, diode D1, optocoupler OC1, comparator U1. The B-phase power sampling detection branch includes: resistor R2, diode D2, optocoupler OC2, comparator U2. The C-phase power sampling detection branch includes: resistor R3, diode D3, optocoupler OC3, comparator U3.

[0052] For the A-phase of the three-phase alternating current, after passing through the current-limiting resistor R1, it is connected to the cathode of diode D1 and also to the anode of the light-emitting diode in optocoupler OC1. The anode of diode D1 is connected to the cathode of the light-emitting diode in optocoupler OC1. The anode of diode D1 is also connected to the anodes of diode D2 and diode D3. The collector of the transistor side in optocoupler OC1 is connected to the +15V power supply after passing through resistor R4. The collector of the transistor side in optocoupler OC1 is also connected to the collectors of the transistor sides in optocoupler OC2 and optocoupler OC3. The emitters of the transistor sides in optocoupler OC1, optocoupler OC2, and optocoupler OC3 are grounded. The +15V power supply is also grounded after passing through resistor R5 and resistor R6 and is connected to the emitter of the transistor side in optocoupler OC3. The collector of the transistor side in optocoupler OC1 is also connected to the non-inverting input terminal of comparator U1. The collector of the transistor side in optocoupler OC2 is also connected to the non-inverting input terminal of comparator U2. The collector of the transistor side in optocoupler OC3 is also connected to the non-inverting input terminal of comparator U3. The common terminal of resistor R5 and resistor R6 is connected to the inverting input terminal of comparator U1.

[0053] The +5V power supply is respectively connected to the output terminals of comparator U1, comparator U2, and comparator U3 after passing through resistor R11.

[0054] Referring to Figure 3 the example shown, in a phase loss protection device applied to a frequency converter proposed by the solution of the present invention, the three-phase power (such as A-phase, B-phase, C-phase) is connected to the anodes of the light-emitting diodes in the optocouplers (such as optocoupler OC1, optocoupler OC2, and optocoupler OC3) after passing through current-limiting resistors (such as resistor R1, resistor R2, and resistor R3), and the cathodes of the light-emitting diodes in the three optocouplers are connected together.

[0055] In some embodiments, the fault determination module includes a switching transistor module, a comparison module, and a charge and discharge module. The switching transistor module is, for example, transistor Q1, the comparison module is, for example, comparator U4, and the charge and discharge module is, for example, capacitor C1 and resistor R8.

[0056] Among them, the output terminal of the three-phase power sampling module is output to the inverting input terminal of the comparison module and connected to the charge and discharge module after passing through the switching transistor module. The non-inverting input terminal of the comparison module serves as the input terminal of the second reference voltage. The output terminal of the comparison module can output a defect fault output signal indicating whether the three-phase AC power supply is missing a phase.

[0057] In some embodiments, the switching transistor module includes a third pull-up module and a transistor. The third pull-up module is, for example, resistor R7, and the transistor is, for example, transistor Q1. The comparison module includes a comparator and a second voltage dividing module. The comparator is, for example, comparator U4, and the second voltage dividing module is, for example, resistor R9 and resistor R10. The charge and discharge module includes a capacitor module and a resistor module. The capacitor module is, for example, capacitor C1. The resistor module is, for example, resistor module R8.

[0058] Among them, the output terminal of the three-phase power sampling module is connected to the base of the transistor. The first DC power supply is connected to the collector of the transistor after passing through the third pull-up module. The emitter of the transistor is connected to the inverting input terminal of the comparator and also connected to the parallel-connected resistor module and capacitor module. The voltage dividing point of the second voltage dividing module is connected to the non-inverting input terminal of the comparator.

[0059] See Figure 3 In the example shown, the fault determination circuit includes transistor Q1, resistor R7, resistor R8, resistor R9, resistor R10, and comparator U4. The output terminals of comparator U1, comparator U2, and comparator U3 are also connected to the gate G of transistor Q1. The +15V power supply is connected to the collector of transistor Q1 after passing through resistor R7. The emitter of transistor Q1 is grounded after passing through the parallel-connected resistor R8 and capacitor C1. The +15V power supply is grounded after passing through resistor R9 and resistor R10, and the common terminal of resistor R9 and resistor R10 is connected to the non-inverting input terminal E of comparator U4. The emitter of transistor Q1 is also connected to the inverting input terminal F of comparator U4.

[0060] In some embodiments, the comparison output module includes a first AND gate module, a second AND gate module, and a third AND gate module. The first AND gate module is, for example, AND gate U5, the second AND gate module is, for example, AND gate U6, and the third AND gate module is, for example, AND gate U7.

[0061] Among them, the first input terminal of the first AND gate module is connected to the output terminal of the fault judgment circuit. The second input terminal of the first AND gate module is connected to the output terminal of the soft start unit. The output terminal of the first AND gate module outputs a driving signal for controlling the first thyristor in the thyristor module. The first thyristor is, for example, thyristor D1.

[0062] The first input terminal of the second AND gate module is connected to the output terminal of the fault judgment circuit. The second input terminal of the second AND gate module is connected to the output terminal of the soft start unit. The output terminal of the second AND gate module outputs a driving signal for controlling the second thyristor in the thyristor module. The second thyristor is, for example, thyristor D2.

[0063] The first input terminal of the third AND gate module is connected to the output terminal of the fault judgment circuit. The second input terminal of the third AND gate module is connected to the output terminal of the soft start unit. The output terminal of the third AND gate module outputs a driving signal for controlling the third thyristor in the thyristor module. The third thyristor is, for example, thyristor D3.

[0064] See Figure 3 In the example shown, the comparison output protection circuit includes: AND gate U5, AND gate U6, and AND gate U7. The output terminal of comparator U4 can output a phase loss fault signal FO to the first input terminals of AND gate U5, AND gate U6, and AND gate U7. The trigger signal SCR_DRV1 of thyristor D1 output by the trigger signal generation module is input to the second input terminal of AND gate U5, and the output terminal of AND gate U5 outputs a determination signal SCR_DRV_U of thyristor D1. The trigger signal SCR_DRV2 of thyristor D2 output by the trigger signal generation module is input to the second input terminal of AND gate U6, and the output terminal of AND gate U6 outputs a determination signal SCR_DRV_V of thyristor D2. The trigger signal SCR_DRV3 of thyristor D3 output by the trigger signal generation module is input to the second input terminal of AND gate U7, and the output terminal of AND gate U7 outputs a determination signal SCR_DRV_W of thyristor D3.

[0065] Figure 4 It is a schematic diagram of the working process of an embodiment of the phase loss protection device proposed by the solution of the present invention. As Figure 4 shown, the working process of the phase loss protection device, i.e., the phase loss detection system, includes:

[0066] Step 1: Apply three-phase electricity.

[0067] Step 2: Determine whether there is a phase loss in the three-phase electricity. If so, execute Step 3. Otherwise, execute Step 4.

[0068] Step 3: Determine whether the line voltage is close to zero. If so, execute Step 5. Otherwise, execute Step 6.

[0069] Step 4: In three-phase power, the optocoupler with the maximum phase voltage conducts. The gate G point of transistor Q1 is at a low-level signal, transistor Q1 is cut off, and the non-inverting input terminal E point of comparator U4 is at a low-level signal. The phase-loss fault signal FO output by comparator U4 is at a high-level signal, there is no phase-loss fault, and the three-phase drive signals are normally output.

[0070] Step 5: No optocoupler conducts, the gate G point of transistor Q1 is at a high-level signal, transistor Q1 conducts, capacitor C1 charges, and step 7 is executed.

[0071] Step 6: The optocoupler with the maximum phase voltage conducts, the gate G point of transistor Q1 is at a low-level signal, transistor Q1 is cut off, capacitor C1 discharges, and step 7 is executed.

[0072] Step 7: The potential of the inverting input terminal F point of comparator U4 is greater than the potential of the non-inverting input terminal E point of comparator U4, and the phase-loss fault signal FO output by comparator U4 is at a low-level signal, there is a phase-loss fault, and no signal is output for the three-phase drive signals.

[0073] See Figure 4 In the example shown, the specific working principle of the phase-loss protection device proposed by the solution of the present invention is that when the voltage of phase A is the largest, the first optocoupler OC1 conducts, when the voltage of phase B is the largest, the second optocoupler OC2 conducts, and when the voltage of phase C is the largest, the third optocoupler OC3 conducts, that is, the optocoupler of the phase with the largest phase voltage conducts. After the optocoupler conducts, its output terminal is pulled down to the ground, so the positive input terminal (i.e., the non-inverting input terminal) of the corresponding comparator is at a low-level signal, and the negative input terminal (i.e., the inverting input terminal) is the voltage signal after the +15V power supply is divided by resistor R5 and resistor R6. Therefore, the output after passing through the comparator is at a low level. The output lines of the three comparators are ANDed. As long as the output of one comparator is at a low level, the gate G point of transistor Q1 is at a low-level signal. Therefore, when the three phases are working normally without phase loss, the gate G point of transistor Q1 is at a low-level signal. When the gate G point of transistor Q1 is at a low-level signal, transistor Q1 does not conduct, then the negative input terminal of comparator U4 inputs a low level, and the positive input terminal of comparator U4 is the high-level signal after the power supply is divided by resistor R9 and resistor R10. Then the phase-loss fault signal FO of comparator U4 is at a high-level signal. The phase-loss fault signal FO of comparator U4 is ANDed with the three-phase thyristor trigger signals SCR_DRV1, SCR_DRV2, and SCR_DRV3 output by the soft-start system. When the phase-loss fault signal FO of comparator U4 is at a high level, the three-phase thyristor drive signals SCR_DRV_U, SCR_DRV_V, and SCR_DRV_W are normally output and input to the thyristor drive module for normal thyristor drive.

[0074] When a certain phase of the three-phase power supply is lacking, all three optocouplers are cut off at the position where the two-phase line voltage is close to zero. Then, the output terminals of all three optocouplers are pulled up to +15V and input to the positive input terminals of the corresponding comparators. The negative input terminals are the voltage signals obtained by dividing the voltage of +15V through resistors R5 and R6. As a result, the outputs of all three comparators are at high level. Then, the gate G point of the triode Q1 is at high-level signal, and the triode Q1 conducts. The +15V power supply charges the capacitor C1 through resistors R7 and R8. By appropriately matching the resistors R7, R8, R9, and R10, it is ensured that during the charging and discharging of the capacitor C1, the potential at the inverting input terminal F point of the comparator U4 is always greater than the potential at the non-inverting input terminal E point of the comparator U4. The negative input terminal of the comparator U4 inputs the voltage signal across the capacitor C1, and the positive input terminal is the voltage signal obtained by dividing the voltage of the +15V power supply through resistors R9 and R10. Then, during the conduction of the triode Q1 and the charging of the capacitor C1, the comparator U4 outputs a phase-loss fault signal FO at low level. When the two-phase line voltage deviates from zero, the optocoupler corresponding to the phase with the largest phase voltage conducts. Therefore, the output of the corresponding comparator is at low level. The gate G point of the triode Q1 is at low-level signal, and the triode is cut off. At this time, the capacitor C1 discharges through the resistor R8. During the discharging of the capacitor C1, the potential at the inverting input terminal F point of the comparator U4 is still higher than the potential at the non-inverting input terminal E point of the comparator U4. Therefore, at this time, the comparator U4 still outputs the phase-loss fault signal FO at low level. So, during the entire three-phase phase-loss process, the comparator U4 always outputs the phase-loss fault signal FO at low level. The phase-loss fault signal FO and the thyristor trigger signal SCR_DRV1 output by the soft-start system are subjected to an "AND" operation. When the phase-loss fault signal FO is at low level, the three-phase thyristor drive signals SCR_DRV_U, SCR_DRV_V, and SCR_DRV_W are all at low level and are blocked. The thyristors have no drive signals and do not conduct, avoiding equipment damage caused by three-phase phase-loss and achieving the effect of phase-loss protection.

[0075] In the related solutions, for the power grid phase-loss fault detection circuit, the detection of power grid phase-loss faults mainly adopts a software method. Not only is the circuit structure complex, but it also cannot quickly respond to the changes in the power grid, having the technical problem of large delay. Compared with the software method of detection in the related solutions, the phase-loss protection device for high-power inverters proposed in the solution of the present invention is composed of a pure hardware circuit. Not only is the circuit structure simple, but it can also respond to the changes in the power grid in a timely manner, improving the detection efficiency of power grid phase-loss faults. Among them, three circuits are used to perform phase-loss fault protection when the input three-phase power is lacking. The circuit structure is simple and the volume is small, which is both safe and cost-saving.

[0076] Through a large number of experimental verifications, by adopting the technical solution of the present invention, a hardware circuit is formed by using a three-phase power sampling detection circuit, a fault judgment circuit and a comparison output protection circuit to detect the open-phase fault when the input three-phase power supply is open-phased. When a three-phase open-phase situation occurs, an open-phase protection signal is output to perform open-phase protection on the circuit after an open-phase fault occurs in the power grid. Therefore, by using a hardware circuit to detect the open-phase of a three-phase power grid, the detection accuracy can be improved.

[0077] According to an embodiment of the present invention, there is also provided an inverter corresponding to the open-phase protection device of the inverter. The inverter may include: the open-phase protection device of the inverter described above.

[0078] Since the processing and functions implemented by the inverter of this embodiment are basically corresponding to the embodiments, principles and examples of the foregoing device, for the details not described in the description of this embodiment, reference may be made to the relevant descriptions in the foregoing embodiments and will not be elaborated here.

[0079] Through a large number of experimental verifications, by adopting the technical solution of the present invention, a hardware circuit is formed by using a three-phase power sampling detection circuit, a fault judgment circuit and a comparison output protection circuit to detect the open-phase fault when the input three-phase power supply is open-phased. When a three-phase open-phase situation occurs, an open-phase protection signal is output to perform open-phase protection on the circuit after an open-phase fault occurs in the power grid, which can respond to the power grid change in time and improve the detection timeliness of the power grid open-phase fault.

[0080] In summary, it is easy for those skilled in the art to understand that, on the premise of no conflict, the above advantageous ways can be freely combined and superimposed.

[0081] The above are only embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the scope of the claims of the present invention.

Claims

1. A phase loss protection device for an inverter, characterized in that, The frequency converter includes a rectification unit and a soft start unit; the rectification unit includes a semi-controlled rectifier bridge; the semi-controlled rectifier bridge includes a thyristor module and a drive module for the thyristor module; the phase loss protection device of the frequency converter includes a phase loss detection unit; wherein, The soft start unit is configured to provide a trigger signal; the trigger signal is a signal for triggering the drive module. The phase loss detection unit is configured to detect whether the three-phase AC power supply is missing a phase and obtain a phase loss fault output signal; and determine the drive signal of the drive module according to the phase loss fault output signal and the trigger signal; the three-phase AC power supply is the power supply input to the rectification unit. The drive module is configured to control the operation of the thyristor module according to the drive signal. The phase loss detection unit includes a three-phase power sampling module, a fault judgment module, and a comparison output module; wherein, The phase loss detection unit detects whether the three-phase AC power supply is missing a phase and obtains a phase loss fault output signal; and determines the drive signal of the drive module according to the phase loss fault output signal and the trigger signal, including: The three-phase power sampling module is configured to detect the isolation voltage of the phase voltage of each phase of the three-phase AC power supply, and compare the isolation voltage of the phase voltage of each phase of the three-phase AC power supply with a first reference voltage to obtain a first comparison result. The fault judgment module is configured to compare the first comparison result with a second reference voltage to obtain a second comparison result as the defect fault output signal indicating whether the three-phase AC power supply is missing a phase. The comparison output module is configured to perform an AND operation on the phase loss fault output signal and the trigger signal to obtain an operation result as the drive signal of the drive module.

2. The phase loss protection device for an inverter according to claim 1, characterized in that, The three-phase power sampling module includes a first pull-up module, a second pull-up module, a first voltage dividing module, an A-phase power sampling branch, a B-phase power sampling branch, and a C-phase power sampling branch; wherein, A first DC power supply is respectively connected to the A-phase power sampling branch, the B-phase power sampling branch, and the C-phase power sampling branch after passing through the first pull-up module. The first DC power supply also provides a first reference voltage for the A-phase power sampling branch, the B-phase power sampling branch, and the C-phase power sampling branch after passing through the first voltage dividing module. A second DC power supply performs a pull-up process on the first comparison results output by the A-phase power sampling branch, the B-phase power sampling branch, and the C-phase power sampling branch after passing through the second pull-up module. Wherein, the common ends of the A-phase power sampling branch, the B-phase power sampling branch, and the C-phase power sampling branch are connected.

3. The phase loss protection device for an inverter according to claim 2, characterized in that, The A-phase power sampling branch, the B-phase power sampling branch, and the C-phase power sampling branch have the same structure.

4. The phase loss protection device for an inverter according to claim 2 or 3, characterized in that, The A-phase power sampling branch includes a first current limiting module, a first rectification module, a first isolation module, and a first comparison module; wherein, The A-phase alternating current in the three-phase alternating current is output to the in-phase input terminal of the first comparison module after passing through the first current-limiting module, the first rectification module, and the first isolation module; The in-phase input terminal of the first comparison module is connected to the first pull-up module; the voltage-dividing point of the first voltage-dividing module is connected to the anti-phase input terminal of the first comparison module; the output terminal of the first comparison module is output to the input terminal of the fault judgment module; Among them, one end of the first rectification module serves as the first common terminal among the common terminals of the A-phase electrical sampling branch, the B-phase electrical sampling branch, and the C-phase electrical sampling branch; the voltage-dividing point of the first voltage-dividing module serves as the second common terminal among the common terminals of the A-phase electrical sampling branch, the B-phase electrical sampling branch, and the C-phase electrical sampling branch; the output terminal of the first comparison module serves as the third common terminal among the common terminals of the A-phase electrical sampling branch, the B-phase electrical sampling branch, and the C-phase electrical sampling branch, and also serves as the output terminal of the three-phase electrical sampling module.

5. The phase loss protection device for an inverter according to claim 4, characterized in that, The first rectification module includes: a first rectification diode; the first isolation module includes: a first optocoupler; The anode of the first rectification diode is connected to the cathode of the diode side in the first optocoupler and serves as the first common terminal.

6. The phase loss protection device for an inverter according to any one of claims 1 to 3, characterized in that, The fault judgment module includes: a switch tube module, a comparison module, and a charge and discharge module; among them, The output terminal of the three-phase electrical sampling module passes through the switch tube module and is output to the anti-phase input terminal of the comparison module and is connected to the charge and discharge module; the in-phase input terminal of the comparison module serves as the input terminal of the second reference voltage; the output terminal of the comparison module can output a defect fault output signal indicating whether the three-phase AC power supply is missing a phase.

7. The phase loss protection device for an inverter according to claim 6, characterized in that, The switch tube module includes: a third pull-up module and a triode; the comparison module includes: a comparator and a second voltage-dividing module; the charge and discharge module includes: a capacitor module and a resistor module; among them, The output terminal of the three-phase electrical sampling module is connected to the base of the triode; a first DC power supply is connected to the collector of the triode after passing through the third pull-up module; the emitter of the triode is connected to the anti-phase input terminal of the comparator and is also connected to the parallel-connected resistor module and capacitor module; the voltage-dividing point of the second voltage-dividing module is connected to the in-phase input terminal of the comparator.

8. The phase loss protection device for an inverter according to any one of claims 1 to 3, characterized in that, The comparison output module includes: a first AND gate module, a second AND gate module, and a third AND gate module; among them, The first input terminal of the first AND gate module is connected to the output terminal of the fault judgment module; the second input terminal of the first AND gate module is connected to the output terminal of the soft start unit; the output terminal of the first AND gate module outputs a drive signal for controlling the first thyristor in the thyristor module; The first input terminal of the second AND gate module is connected to the output terminal of the fault judgment module; the second input terminal of the second AND gate module is connected to the output terminal of the soft start unit; the output terminal of the second AND gate module outputs a drive signal for controlling the second thyristor in the thyristor module; The first input terminal of the third AND gate module is connected to the output terminal of the fault judgment module; the second input terminal of the third AND gate module is connected to the output terminal of the soft start unit; the output terminal of the third AND gate module outputs a driving signal for controlling the third thyristor in the thyristor module.

9. A frequency converter, characterized in that, Comprising: The phase loss protection device of the frequency converter according to any one of claims 1 to 8.

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