阅读说明：本技术 一种变频器的缺相保护装置和变频器 (Open-phase protection device of frequency converter and frequency converter ) 是由 张统世 张艳婷 周维邦 张旗旗 谢嵩琳 于 2021-09-14 设计创作，主要内容包括：本发明公开了一种变频器的缺相保护装置和变频器,该装置包括：软启动单元,提供触发信号；触发信号,是用于触发驱动模块的信号；缺相检测单元,检测三相交流电源是否缺相,得到缺相故障输出信号；以及,根据缺相故障输出信号和触发信号,确定驱动模块的驱动信号；三相交流电源,是输入至整流单元的电源；驱动模块,根据驱动信号,控制晶闸管模块的工作。该方案,通过采用硬件电路进行三相电网缺相检测,能够提升检测准确性。(The invention discloses a phase-failure protection device of a frequency converter and the frequency converter, the device comprises: the soft starting unit provides a trigger signal; the trigger signal is a signal for triggering the driving module; the open-phase detection unit is used for detecting whether the three-phase alternating-current power supply is open-phase or not to obtain an open-phase fault output signal; determining a driving signal of the driving module according to the phase-failure fault output signal and the trigger signal; a three-phase AC power supply which is a power supply input to the rectifying unit; and the driving module controls the work of the thyristor module according to the driving signal. This scheme carries out three-phase electric wire netting phase loss detection through adopting hardware circuit, can promote the detection accuracy.)

1. A phase loss protection device of a frequency converter is characterized in that the frequency converter comprises: the soft start circuit comprises a rectifying unit and a soft start unit; the rectifying unit includes: a half-controlled rectifier bridge; the half-controlled rectifier bridge comprises: the driving module comprises a thyristor module and a driving module of the thyristor module; the open-phase protection device of the frequency converter comprises: a phase loss detection unit; wherein the content of the first and second substances,

the soft start unit is configured to provide a trigger signal; the trigger signal is a signal for triggering the driving module;

the open-phase detection unit is configured to detect whether a three-phase alternating-current power supply is open-phase or not to obtain an open-phase fault output signal; determining a driving signal of the driving module according to the open-phase fault output signal and the trigger signal; the three-phase alternating current power supply is a power supply input to the rectifying unit;

the driving module is configured to control the operation of the thyristor module according to the driving signal.

2. The open-phase protection device of a frequency converter according to claim 1, wherein the open-phase detection unit comprises: the system comprises a three-phase electric sampling module, a fault judging module and a comparison output module; wherein the content of the first and second substances,

the open-phase detection unit is used for detecting whether the three-phase alternating-current power supply is open-phase or not to obtain an open-phase fault output signal; and determining a driving signal of the driving module according to the open-phase fault output signal and the trigger signal, including:

the three-phase electric sampling module is configured to detect an isolation voltage of a phase voltage of each phase of the three-phase alternating-current power supply and compare the isolation voltage of the phase voltage of each phase of the three-phase alternating-current 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, and the second comparison result is used as a fault output signal for judging whether the three-phase alternating-current power supply is in a phase failure state;

the comparison output module is configured to perform AND operation on the open-phase fault output signal and the trigger signal to obtain an operation result, and the operation result is used as a driving signal of the driving module.

3. The open-phase protection device of a frequency converter according to claim 2, wherein the three-phase electric sampling module comprises: the device comprises a first pull-up module, a second pull-up module, a first voltage division module, an A-phase electric sampling branch, a B-phase electric sampling branch and a C-phase electric sampling branch; wherein the content of the first and second substances,

the first direct-current power supply is connected to the A-phase electric sampling branch, the B-phase electric sampling branch and the C-phase electric sampling branch respectively after passing through the first pull-up module;

the first direct-current power supply also provides first reference voltages for the A-phase electric sampling branch, the B-phase electric sampling branch and the C-phase electric sampling branch respectively after passing through the first voltage division module;

the second direct-current power supply respectively performs pull-up processing on first comparison results output by the A-phase electric sampling branch, the B-phase electric sampling branch and the C-phase electric sampling branch after passing through the second pull-up module;

the A-phase electric sampling branch, the B-phase electric sampling branch and the C-phase electric sampling branch are connected at the common end.

4. The open-phase protection device of a frequency converter according to claim 3, wherein the A-phase electrical sampling branch, the B-phase electrical sampling branch and the C-phase electrical sampling branch are identical in structure.

5. The open-phase protection device of a frequency converter according to claim 3 or 4, wherein the A-phase electrical sampling branch comprises: the device comprises a first current limiting module, a first rectifying module, a first isolating module and a first comparing module; wherein the content of the first and second substances,

the A-phase alternating current in the three-phase alternating current passes through the first current limiting module, the first rectifying module and the first isolating module and then is output to the non-inverting input end of the first comparing module;

the non-inverting input end of the first comparison module is connected to the first pull-up module; the voltage division point of the first voltage division module is connected to the inverting input end of the first comparison module; the output end of the first comparison module is output to the input end of the fault judgment module;

one end of the first rectifying module is used as a first common end of common ends of the A-phase electric sampling branch, the B-phase electric sampling branch and the C-phase electric sampling branch; a voltage division point of the first voltage division module is used as a second common end of common ends of the A-phase electric sampling branch, the B-phase electric sampling branch and the C-phase electric sampling branch; and the output end of the first comparison module is used as a third common end of common ends of the A-phase electrical sampling branch, the B-phase electrical sampling branch and the C-phase electrical sampling branch, and is also used as the output end of the three-phase electrical sampling module.

6. The open-phase protection device of a frequency converter according to claim 5, wherein the first rectifying module comprises: a first rectifying diode; the first isolation module, comprising: a first optical coupler;

and the anode of the first rectifying diode is connected with the cathode of the diode side in the first optical coupler and is used as the first common end.

7. The open-phase protection device of a frequency converter according to any one of claims 2 to 4, wherein the fault determining module comprises: the device comprises a switching tube module, a comparison module and a charge-discharge module; wherein the content of the first and second substances,

the output end of the three-phase electric sampling module passes through the switch tube module and then is output to the inverted input end of the comparison module and is connected to the charge-discharge module; the non-inverting input end of the comparison module is used as the input end of a second reference voltage; and the output end of the comparison module can output a defect fault output signal indicating whether the three-phase alternating-current power supply is in phase failure.

8. The open-phase protection device of a frequency converter according to claim 7, wherein the switch tube module comprises: a third pull-up module and a triode; the comparison module comprises: the comparator and the second voltage division module; the charge-discharge module comprises: a capacitance module and a resistance module; wherein the content of the first and second substances,

the output end of the three-phase electric sampling module is connected to the base electrode of the triode; the first direct current power supply is connected to the collector electrode of the triode after passing through the third pull-up module; the emitter of the triode is connected to the inverting input end of the comparator and is also connected to the resistor module and the capacitor module which are connected in parallel; and the voltage division point of the second voltage division module is connected to the non-inverting input end of the comparator.

9. The open-phase protection device of a frequency converter according to any one of claims 2 to 4, wherein the comparison output module comprises: the first AND gate module, the second AND gate module and the third AND gate module; wherein the content of the first and second substances,

the first input end of the first AND gate module is connected with the output end of the fault judgment circuit; the second input end of the first AND gate module is connected with the output end of the soft start unit; the output end of the first AND gate module outputs a driving signal for controlling a first thyristor in the thyristor module;

the first input end of the second AND gate module is connected with the output end of the fault judgment circuit; the second input end of the second AND gate module is connected with the output end of the soft start unit; the output end of the second AND gate module outputs a driving signal for controlling a second thyristor in the thyristor module;

the first input end of the third AND gate module is connected with the output end of the fault judgment circuit; the second input end of the third AND gate module is connected with the output end of the soft start unit; and the output end of the third AND gate module outputs a driving signal for controlling a third thyristor in the thyristor module.

10. A frequency converter, comprising: a phase-loss protection arrangement for a frequency converter according to any one of claims 1 to 9.

Technical Field

The invention belongs to the technical field of frequency converters, and particularly relates to a phase-loss protection device of a frequency converter and the frequency converter, in particular to a phase-loss protection device applied to a high-power frequency converter and the frequency converter with the same.

Background

In the high-voltage complex working process of the three-phase power grid, the phase loss of the power grid is easily caused, if the phase loss fault is not detected in time or the time for detection and elimination is long, the reliable operation of the frequency converter can be seriously influenced, and the related power equipment such as a rear-stage rectifier bridge is damaged, so that the economic and property loss is serious. However, in the related schemes, the power grid open-phase fault detection circuit mainly detects the power grid open-phase fault by adopting a software or software and hardware combination mode, and the detection accuracy is poor.

The above is only for the purpose of assisting understanding of the technical aspects of the present invention, and does not represent an admission that the above is prior art.

Disclosure of Invention

The invention aims to provide a phase-lack protection device of a frequency converter and the frequency converter, which are used for solving the problem of poor detection accuracy when software or a software and hardware combined mode is adopted for detecting the phase lack of a three-phase power grid, and achieving the effect of improving the detection accuracy by adopting a hardware circuit for detecting the phase lack of the three-phase power grid.

The invention provides a phase-lack protection device of a frequency converter, wherein the frequency converter comprises: the soft start circuit comprises a rectifying unit and a soft start unit; the rectifying unit includes: a half-controlled rectifier bridge; the half-controlled rectifier bridge comprises: the driving module comprises a thyristor module and a driving module of the thyristor module; the open-phase protection device of the frequency converter comprises: 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 driving module; the open-phase detection unit is configured to detect whether a three-phase alternating-current power supply is open-phase or not to obtain an open-phase fault output signal; determining a driving signal of the driving module according to the open-phase fault output signal and the trigger signal; the three-phase alternating current power supply is a power supply input to the rectifying unit; the driving module is configured to control the operation of the thyristor module according to the driving signal.

In some embodiments, the phase-loss detection unit includes: the system comprises a three-phase electric sampling module, a fault judging module and a comparison output module; the open-phase detection unit detects whether a three-phase alternating-current power supply is open-phase or not to obtain an open-phase fault output signal; and determining a driving signal of the driving module according to the open-phase fault output signal and the trigger signal, including: the three-phase electric sampling module is configured to detect an isolation voltage of a phase voltage of each phase of the three-phase alternating-current power supply and compare the isolation voltage of the phase voltage of each phase of the three-phase alternating-current 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, and the second comparison result is used as a fault output signal for judging whether the three-phase alternating-current power supply is in a phase failure state; the comparison output module is configured to perform AND operation on the open-phase fault output signal and the trigger signal to obtain an operation result, and the operation result is used as a driving signal of the driving module.

In some embodiments, the three-phase electrical sampling module comprises: the device comprises a first pull-up module, a second pull-up module, a first voltage division module, an A-phase electric sampling branch, a B-phase electric sampling branch and a C-phase electric sampling branch; the first direct-current power supply is connected to the A-phase electric sampling branch, the B-phase electric sampling branch and the C-phase electric sampling branch respectively after passing through the first pull-up module; the first direct-current power supply also provides first reference voltages for the A-phase electric sampling branch, the B-phase electric sampling branch and the C-phase electric sampling branch respectively after passing through the first voltage division module; the second direct-current power supply respectively performs pull-up processing on first comparison results output by the A-phase electric sampling branch, the B-phase electric sampling branch and the C-phase electric sampling branch after passing through the second pull-up module; the A-phase electric sampling branch, the B-phase electric sampling branch and the C-phase electric sampling branch are connected at the common end.

In some embodiments, the a-phase, B-phase, and C-phase electrical sampling legs are identical in structure.

In some embodiments, the a-phase electrical sampling branch comprises: the device comprises a first current limiting module, a first rectifying module, a first isolating module and a first comparing module; the A-phase alternating current in the three-phase alternating current passes through the first current limiting module, the first rectifying module and the first isolating module and then is output to the non-inverting input end of the first comparing module; the non-inverting input end of the first comparison module is connected to the first pull-up module; the voltage division point of the first voltage division module is connected to the inverting input end of the first comparison module; the output end of the first comparison module is output to the input end of the fault judgment module; one end of the first rectifying module is used as a first common end of common ends of the A-phase electric sampling branch, the B-phase electric sampling branch and the C-phase electric sampling branch; a voltage division point of the first voltage division module is used as a second common end of common ends of the A-phase electric sampling branch, the B-phase electric sampling branch and the C-phase electric sampling branch; and the output end of the first comparison module is used as a third common end of common ends of the A-phase electrical sampling branch, the B-phase electrical sampling branch and the C-phase electrical sampling branch, and is also used as the output end of the three-phase electrical sampling module.

In some embodiments, the first rectification module comprises: a first rectifying diode; the first isolation module, comprising: a first optical coupler; and the anode of the first rectifying diode is connected with the cathode of the diode side in the first optical coupler and is used as the first common end.

In some embodiments, the failure determination module includes: the device comprises a switching tube module, a comparison module and a charge-discharge module; the output end of the three-phase electric sampling module passes through the switch tube module and then is output to the inverted input end of the comparison module and is connected to the charge-discharge module; the non-inverting input end of the comparison module is used as the input end of a second reference voltage; and the output end of the comparison module can output a defect fault output signal indicating whether the three-phase alternating-current power supply is in phase failure.

In some embodiments, the switch tube module comprises: a third pull-up module and a triode; the comparison module comprises: the comparator and the second voltage division module; the charge-discharge module comprises: a capacitance module and a resistance module; the output end of the three-phase electric sampling module is connected to the base electrode of the triode; the first direct current power supply is connected to the collector electrode of the triode after passing through the third pull-up module; the emitter of the triode is connected to the inverting input end of the comparator and is also connected to the resistor module and the capacitor module which are connected in parallel; and the voltage division point of the second voltage division module is connected to the non-inverting input end of the comparator.

In some embodiments, the comparison output module includes: the first AND gate module, the second AND gate module and the third AND gate module; the first input end of the first AND gate module is connected with the output end of the fault judgment circuit; the second input end of the first AND gate module is connected with the output end of the soft start unit; the output end of the first AND gate module outputs a driving signal for controlling a first thyristor in the thyristor module; the first input end of the second AND gate module is connected with the output end of the fault judgment circuit; the second input end of the second AND gate module is connected with the output end of the soft start unit; the output end of the second AND gate module outputs a driving signal for controlling a second thyristor in the thyristor module; the first input end of the third AND gate module is connected with the output end of the fault judgment circuit; the second input end of the third AND gate module is connected with the output end of the soft start unit; and the output end of the third AND gate module outputs a driving signal for controlling a third thyristor in the thyristor module.

In accordance with the above apparatus, another aspect of the present invention provides a frequency converter, including: the phase-lack protection device of the frequency converter is described above.

Therefore, according to the scheme of the invention, a hardware circuit is formed by adopting the three-phase electric sampling detection circuit, the fault judgment circuit and the comparison output protection circuit, the phase-lack fault detection is carried out when the input three-phase power supply is in phase-lack state, and when the three-phase-lack condition occurs, a phase-lack protection signal is output so as to carry out phase-lack protection on the circuit after the phase-lack fault occurs in the power grid; therefore, the detection accuracy can be improved by adopting the hardware circuit to detect the phase loss of the three-phase power grid.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.

The technical solution of the present invention is further described in detail by the accompanying drawings and embodiments.

Drawings

Fig. 1 is a schematic structural diagram of an embodiment of a phase-loss protection apparatus for a frequency converter according to an embodiment of the present invention;

fig. 2 is a schematic structural diagram of an embodiment of a frequency converter soft start system with a phase-loss protection device according to an embodiment of the present invention;

fig. 3 is a schematic structural diagram of an embodiment of a phase-loss protection system applied to a frequency converter soft start system according to the present invention;

fig. 4 is a schematic workflow diagram of an embodiment of the open-phase protection apparatus according to the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to the specific embodiments of the present invention and the accompanying drawings. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

According to an embodiment of the invention, a phase-loss protection device of a frequency converter is provided. Referring to fig. 1, a schematic diagram of an embodiment of the apparatus of the present invention is shown. The frequency converter comprises: a rectifying unit and a soft start unit. A soft start unit, such as a soft start control system. The rectifying unit includes: and a semi-controlled rectifier bridge. The half controlA rectifier bridge, comprising: thyristor module (e.g. thyristor D)₁Thyristor D₂Thyristor D₃) And a driving module of the thyristor module (i.e., a thyristor driving module). The open-phase protection device of the frequency converter comprises: a phase loss detection unit (e.g., a phase loss detection system).

Wherein the soft start unit is configured to provide a trigger signal. The trigger signal is a signal for triggering the driving module.

And the open-phase detection unit is configured to detect whether the three-phase alternating-current power supply is open-phase or not to obtain an open-phase fault output signal. And determining a driving signal of the driving module according to the phase-lack fault output signal and the trigger signal. The three-phase ac power supply is a power supply input to the rectifying unit.

The driving module is configured to control the operation of the thyristor module according to the driving signal.

The invention provides a low-cost and high-reliability detection device to realize open-phase protection, in particular to an open-phase protection device applied to a high-power frequency converter, which can monitor the open-phase condition of a power grid in real time and carry out open-phase protection on a circuit after the open-phase fault of the power grid occurs.

In some embodiments, the phase-loss detection unit includes: the device comprises a three-phase electric sampling module, a fault judging module and a comparison output module. The three-phase power sampling module is a three-phase power sampling detection circuit, the fault judgment module is a fault judgment circuit, and the comparison output module is a comparison output protection circuit.

The open-phase detection unit detects whether a three-phase alternating-current power supply is open-phase or not to obtain an open-phase fault output signal. And determining a driving signal of the driving module according to the open-phase fault output signal and the trigger signal, including:

the three-phase electric sampling module is configured to detect an isolation voltage of a phase voltage of each phase of the three-phase alternating-current power supply, and compare the isolation voltage of the phase voltage of each phase of the three-phase alternating-current power supply with a first reference voltage to obtain a first comparison result. The isolation voltage of the phase voltage of each alternating current power supply is the voltage output after the optocoupler is switched on and the isolation voltage of the phase voltage of each alternating current power supply is switched on and then is pulled up to 15V.

And the fault judging module is configured to compare the first comparison result with a second reference voltage to obtain a second comparison result, and the second comparison result is used as a fault output signal for judging whether the three-phase alternating-current power supply is in a phase failure state or not.

The comparison output module is configured to perform AND operation on the open-phase fault output signal and the trigger signal to obtain an operation result, and the operation result is used as a driving signal of the driving module.

According to the scheme of the invention, three circuits, namely the three-phase power sampling detection circuit, the fault judgment circuit and the comparison output protection circuit, are adopted to detect and protect the phase-lack fault when the input three-phase power supply is in phase-lack state, and the three-phase power sampling detection circuit is simple in structure and accurate in detection. Under the condition that three-phase electricity is in phase failure, the protection circuit blocks the thyristor driving signal to achieve the phase failure protection effect.

Fig. 2 is a schematic structural diagram of an embodiment of a frequency converter soft start system with a phase-loss protection device according to the present invention. As shown in fig. 2, the frequency converter soft start system with the open-phase protection device includes: the device comprises a rectifying unit, a bus capacitor unit, a phase-lack detection system, a soft start control system and a thyristor drive module. Three-phase alternating current power supply such as 380V AC is output to the bus capacitor unit after passing through the rectifying unit. A rectifying unit comprising: and a semi-controlled rectifier bridge. This half accuse rectifier bridge includes: thyristor D₁Thyristor D₂Thyristor D₃Diode D₄Diode D₅Diode D₆. The thyristor drive module is connected to the thyristor D₁Thyristor D₂Thyristor D₃. A phase loss detection system comprising: the phase loss detection module and the phase loss protection module are connected to the thyristor drive module. A soft start control system comprising: the device comprises a trigger signal generation module, a phase-shifting signal generation module, a synchronous signal generation module and a voltage sampling module. Voltage sampling module capable of samplingAnd the bus voltage of the bus capacitor voltage and the line voltage or the phase voltage of the motor. And the voltage sampling module is respectively output to the trigger signal generation module after passing through the phase shift signal generation module and the synchronous signal generation module. And the trigger signal generation module outputs the trigger signal to the open-phase protection module. A bus capacitor unit comprising: bus capacitor and voltage-sharing resistor.

Referring to the example shown in fig. 2, in the soft start system of the high-power frequency converter, a three-phase half-controlled rectification topology composed of thyristors and diodes is adopted. The soft starting device adopts a hardware control mode, the trigger pulse is generated by a voltage sampling module, a phase-shifting signal generating module, a synchronous signal generating module and a trigger signal generating module, and the width of the trigger pulse is continuously increased when the trigger angle is changed from 180 degrees to 0 degrees, namely, the conduction interval is continuously enlarged, and the bus voltage is continuously increased. When the trigger angle is reduced to 0 degree, the soft start of the frequency converter is completed.

Collecting three-phase input line voltage U_UV、U_VW、U_WUAnd obtaining its inverse value U by means of an operational amplifier_VU、U_WV、U_UW；U_UW、U_VU、U_WVComparing with zero respectively to obtain U, V, W three-phase synchronous signals, wherein the synchronous signals are 180-degree trigger intervals of each phase of thyristor; u shape_UVAnd U_UW、U_VUAnd U_VW、U_WUAnd U_WVTwo pairs of the signals are taken as a group, and the maximum value of each group is taken to respectively generate U, V, W three-phase saddle wave signals; saddle wave and bus sampling voltage U of each phase_DCComparing to generate a phase-shifted signal; the effective interval of the phase-shift signal is increased along with the increase of the bus voltage; the sync signal of each phase is anded with the phase shift signal to generate the trigger signal for that phase. The larger the interval of the trigger signal is, the higher the bus voltage value is reflected; in order to make the thyristor conduct stably, multi-pulse triggering needs to be used when the thyristor is triggered. A NOT gate or an operational amplifier is used for generating a self-oscillation clock, and the clock signal and a trigger signal are used for carrying out AND operation, so that a control signal is generated; in a soft start system, the control signal output by the system can be directThe driving signal is input into the thyristor driving module to generate a driving signal to directly drive the thyristor. However, in the present invention, the control signal output by the system needs to be and-operated with the phase-missing fault signal FO, and if there is no phase-missing fault (i.e. the phase-missing fault signal FO is a high-level signal), the control signal is normally output and input to the thyristor driving module to generate a driving signal to directly drive the thyristor. If a phase-missing fault occurs (i.e. the phase-missing fault signal FO is a low-level signal), the control signal cannot be output, which means that the thyristor driving module cannot generate a driving signal to drive the thyristor.

The three-phase alternating current open-phase detection circuit in the related scheme is realized by outputting an open-phase detection result to a related circuit, such as an MCU/DSP control unit, after alternating current rectification and voltage division are compared with a reference voltage through a comparator, and a software and hardware combination mode, and the detection circuit has the problem of inaccurate detection. In the scheme of the invention, the phase-failure protection device is applied to the phase-failure protection device of the high-power frequency converter, the phase-failure detection and protection are realized by completely adopting a hardware circuit mode, and the circuit is simple and easy to implement. The frequency converter soft start system with the open-phase protection device outputs an open-phase protection signal when the three-phase open-phase condition occurs, blocks the driving signal of the thyristor, ensures that the three thyristors are not conducted, can monitor the open-phase condition of a power grid in real time, and carries out open-phase protection on a circuit after the open-phase fault occurs in the power grid.

In some embodiments, the three-phase electrical sampling module comprises: the device comprises a first pull-up module, a second pull-up module, a first voltage division module, an A-phase electric sampling branch, a B-phase electric sampling branch and a C-phase electric sampling branch. A first pull-up module, such as resistor R4. The first voltage dividing module is a resistor R5 and a resistor R6. A second pull-up module, such as resistor R11.

And a first direct current power supply, such as a +15V power supply, is connected to the a-phase electrical sampling branch, the B-phase electrical sampling branch and the C-phase electrical sampling branch respectively after passing through the first pull-up module.

The first direct current power supply also provides first reference voltage for the A-phase electric sampling branch, the B-phase electric sampling branch and the C-phase electric sampling branch respectively after passing through the first voltage division module.

And a second direct current power supply, such as a +5V power supply, is subjected to pull-up processing on first comparison results output by the A-phase electric sampling branch, the B-phase electric sampling branch and the C-phase electric sampling branch respectively after passing through the second pull-up module.

The A-phase electric sampling branch, the B-phase electric sampling branch and the C-phase electric sampling branch are connected at the common end.

In some embodiments, the a-phase, B-phase, and C-phase electrical sampling legs are identical in structure.

In some embodiments, the a-phase electrical sampling branch comprises: the circuit comprises a first current limiting module, a first rectifying module, a first isolating module and a first comparing module. The circuit comprises a first current limiting module such as a resistor R1, a first rectifying module such as a diode D1, a first isolating module such as an optical coupler OC1 and a first comparing module such as a comparator U1.

The A-phase alternating current in the three-phase alternating current passes through the first current limiting module, the first rectifying module and the first isolating module and then is output to the non-inverting input end of the first comparing module.

And the non-inverting input end 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 terminal of the resistor R5 and the resistor R6, is connected to the inverting input terminal of the first comparing module. And the output end of the first comparison module is output to the input end of the fault judgment module.

One end of the first rectifying module is used as a first common end of common ends of the A-phase electric sampling branch, the B-phase electric sampling branch and the C-phase electric sampling branch. And the voltage division point of the first voltage division module is used as a second common end in common ends of the A-phase electric sampling branch, the B-phase electric sampling branch and the C-phase electric sampling branch. And the output end of the first comparison module is used as a third common end of common ends of the A-phase electrical sampling branch, the B-phase electrical sampling branch and the C-phase electrical sampling branch, and is also used as the output end of the three-phase electrical sampling module.

In some embodiments, the first rectification module comprises: a first rectifying diode, such as diode D1. The first isolation module, comprising: a first optical coupler, such as optical coupler OC 1.

And the anode of the first rectifying diode is connected with the cathode of the diode side in the first optical coupler and is used as the first common end.

Fig. 3 is a schematic structural diagram of an embodiment of a phase-loss protection system applied to a frequency converter soft start system according to the present invention. As shown in fig. 3, the open-phase protection system applied to the frequency converter soft start system is the open-phase detection system shown in fig. 2. In the open-phase detection system, the open-phase detection module includes: the system comprises a three-phase electric sampling detection circuit and a fault judgment circuit. A phase loss protection module comprising: and comparing output protection.

Wherein, three-phase electricity sampling detection circuit includes: the device comprises an A-phase electric sampling detection branch, a B-phase electric sampling detection branch, a C-phase electric sampling detection branch, a resistor R4, a resistor R5, a resistor R6 and a resistor R11. A looks electricity sampling test branch road includes: the circuit comprises a resistor R1, a diode D1, an optical coupler OC1 and a comparator U1. B looks electricity sampling test branch road includes: the circuit comprises a resistor R2, a diode D2, an optical coupler OC2 and a comparator U2. C looks electricity sampling test branch road includes: the circuit comprises a resistor R3, a diode D3, an optical coupler OC3 and a comparator U3.

The A phase of the three-phase alternating current passes through a current limiting resistor R1 and then is connected to the cathode of a diode D1 and also connected to the anode of a light emitting diode in an optical coupler OC 1. The anode of the diode D1 is connected with the cathode of the light emitting diode in the optical coupler OC 1. The anode of the diode D1 is also connected to the anode of the diode D2 and the anode of the diode D3. And a collector at the transistor side in the optical coupler OC1 is connected with a +15V power supply through a resistor R4. The collector electrode on the transistor side in the optical coupler OC1 is also connected with the collector electrode on the transistor side in the optical coupler OC2 and the collector electrode on the transistor side in the optical coupler OC 3. An emitter on the transistor side in the optical coupler OC1, an emitter on the transistor side in the optical coupler OC2 and an emitter on the transistor side in the optical coupler OC3 are grounded. The +15V power supply is grounded through a resistor R5 and a resistor R6, and is connected to an emitter on the transistor side in the optical coupler OC 3. The collector on the transistor side in the optical coupler OC1 is also connected to the non-inverting input terminal of the comparator U1. The collector on the transistor side in the optical coupler OC2 is also connected to the non-inverting input terminal of the comparator U2. The collector on the transistor side in the optical coupler OC3 is also connected to the non-inverting input terminal of the comparator U3. The common terminal of the resistor R5 and the resistor R6 is connected to the inverting input terminal of the comparator U1.

The +5V power supply is connected to the output terminal of the comparator U1, the output terminal of the comparator U2 and the output terminal of the comparator U3 through the resistor R11.

Referring to the example shown in fig. 3, in the open-phase protection device applied to the frequency converter according to the present invention, three-phase power (e.g., a phase a, a phase B, and a phase C) is connected to an anode of a light emitting diode in an optical coupler (e.g., an optical coupler OC1, an optical coupler OC2, and an optical coupler OC3) through a current limiting resistor (e.g., a resistor R1, a resistor R2, and a resistor R3), and cathodes of the light emitting diodes in the three optical couplers are connected.

In some embodiments, the failure determination module includes: the device comprises a switching tube module, a comparison module and a charge-discharge module. The circuit comprises a switching tube module such as a triode Q1, a comparison module such as a comparator U4, a charging and discharging module such as a capacitor C1 and a resistor R8.

The output end of the three-phase electric sampling module passes through the switch tube module, then is output to the inverted input end of the comparison module, and is connected to the charge-discharge module. And the non-inverting input end of the comparison module is used as the input end of the second reference voltage. And the output end of the comparison module can output a defect fault output signal indicating whether the three-phase alternating-current power supply is in phase failure.

In some embodiments, the switch tube module comprises: third pull-up module and transistor the third pull-up module is, for example, a resistor R7 and the transistor is, for example, a transistor Q1. The comparison module comprises: a comparator and a second voltage division module. A comparator such as a comparator U4, and a second voltage dividing module such as a resistor R9 and a resistor R10. The charge-discharge module comprises: a capacitive module and a resistive module. A capacitive module, such as a capacitor C1. A resistance module, such as resistance module R8.

The output end of the three-phase electric sampling module is connected to the base electrode of the triode. And the first direct current power supply is connected to the collector electrode of the triode after passing through the third pull-up module. And the emitter of the triode is connected to the inverting input end of the comparator and is also connected to the resistor module and the capacitor module which are connected in parallel. And the voltage division point of the second voltage division module is connected to the non-inverting input end of the comparator.

Referring to the example shown in fig. 3, the failure determination circuit includes: triode Q1, resistance R7, resistance R8, resistance R9, resistance R10, comparator U4. The output terminal of the comparator U1, the output terminal of the comparator U2, and the output terminal of the comparator U3 are also connected to the gate G of the transistor Q1. The +15V power supply is connected to the collector of the transistor Q1 through a resistor R7. The emitter of the transistor Q1 is grounded through a resistor R8 and a capacitor C1 which are connected in parallel. The +15V power supply is grounded after passing through the resistor R9 and the resistor R10, and the common end of the resistor R9 and the resistor R10 is connected with the non-inverting input end E of the comparator U4. The emitter of the transistor Q1 is also connected to the inverting input F of the comparator U4.

In some embodiments, the comparison output module includes: the first AND gate module, the second AND gate module and the third AND gate module. A first and gate module such as and gate U5, a second and gate module such as and gate U6, and a third and gate module such as and gate U7.

And the first input end of the first AND gate module is connected with the output end of the fault judgment circuit. And the second input end of the first AND gate module is connected with the output end of the soft start unit. And the output end of the first AND gate module outputs a driving signal for controlling a first thyristor in the thyristor module. First thyristors, e.g. thyristor D₁。

And the first input end of the second AND gate module is connected with the output end of the fault judgment circuit. And the second input end of the second AND gate module is connected with the output end of the soft start unit. And the output end of the second AND gate module outputs a driving signal for controlling a second thyristor in the thyristor module. Second thyristors, e.g. thyristor D₂。

And the first input end of the third AND gate module is connected with the output end of the fault judgment circuit. Second of the third AND gate moduleAnd the input end is connected with the output end of the soft start unit. And the output end of the third AND gate module outputs a driving signal for controlling a third thyristor in the thyristor module. Third thyristors, e.g. thyristors D₃。

Referring to the example shown in fig. 3, the comparison output protection circuit includes: and the and gate U5, the and gate U6, and the and gate U7. The output of the comparator U4 is capable of outputting a phase loss fault signal FO to a first input of the and gate U5, a first input of the and gate U6, and a first input of the and gate U7. Trigger signal generating module, output thyristor D₁The trigger signal SCR _ DRV1 is input to a second input end of the AND gate U5, and the output end of the AND gate U5 outputs a thyristor D₁The determination signal SCR _ DRV _ U. Trigger signal generating module, output thyristor D₂The trigger signal SCR _ DRV2 is input to a second input end of the AND gate U6, and the output end of the AND gate U6 outputs a thyristor D₂The determination signal SCR _ DRV _ V. Trigger signal generating module, output thyristor D₃The trigger signal SCR _ DRV3 is input to a second input end of the AND gate U7, and the output end of the AND gate U7 outputs a thyristor D₃The determination signal SCR _ DRV _ W.

Fig. 4 is a schematic workflow diagram of an embodiment of the open-phase protection apparatus according to the present invention. As shown in fig. 4, the working process of the open-phase protection device, i.e. the open-phase detection system, includes:

and step 1, supplying three-phase power.

And 2, judging whether the three-phase power is in phase failure or not, and if so, executing the step 3. Otherwise, step 4 is executed.

And 3, judging whether the online voltage is close to a zero point, and if so, executing the step 5. Otherwise, step 6 is executed.

And 4, conducting the optical coupler with the largest phase voltage in the three-phase power. The gate G of the transistor Q1 is a low level signal, the transistor Q1 is turned off, and the non-inverting input E of the comparator U4 is a low level signal. The phase-lack fault signal FO output by the comparator U4 is a high-level signal, no phase-lack fault exists, and the three-phase driving signal is normally output.

And 5, no optical coupling conduction exists, the grid G point of the triode Q1 is a high-level signal, the triode Q1 is conducted, the capacitor C1 is charged, and the step 7 is executed.

And 6, switching on the optocoupler with the maximum phase voltage, enabling a grid G point of the polar tube Q1 to be a low-level signal, cutting off the triode Q1, discharging the capacitor C1, and executing the step 7.

And 7, the potential of the point F of the inverting input end of the comparator U4 is greater than the potential of the point E of the non-inverting input end of the comparator U4, the phase-missing fault signal FO output by the comparator U4 is a low-level signal, a phase-missing fault occurs, and no three-phase driving signal is output.

Referring to the example shown in fig. 4, the specific working principle of the open-phase protection device proposed by the scheme of the present invention is that when the voltage of the a phase is the maximum, the first optical coupler OC1 is turned on, when the voltage of the B phase is the maximum, the second optical coupler OC2 is turned on, and when the voltage of the C phase is the maximum, the third optical coupler OC3 is turned on, that is, the optical coupler of the phase with the maximum phase voltage is turned on. When the optical coupler is turned on, the output end of the optical coupler is pulled down to the ground, the positive input end (i.e., the non-inverting input end) of the corresponding comparator is a low-level signal, and the negative input end (i.e., the inverting input end) is a voltage signal divided by the +15V power supply through the resistor R5 and the resistor R6, so that the voltage signal is output as a low level through the comparator. The output of each of the three comparator outputs is low, and the gate G of the transistor Q1 is a low signal. Therefore, when the three phases normally work without phase loss, the gate G of the transistor Q1 is a low level signal. When the gate G of the transistor Q1 is a low level signal, the transistor Q1 is turned off, the negative input terminal of the comparator U4 inputs a low level, the positive input terminal of the comparator U4 is a high level signal divided by the resistor R9 and the resistor R10, and the open-phase fault signal FO of the comparator U4 is a high level signal. The open-phase fault signal FO of the comparator U4 and the three-phase thyristor trigger signals SCR _ DRV1, SCR _ DRV2 and SCR _ DRV3 output by the soft start system are subjected to AND operation, and when the open-phase fault signal FO of the comparator U4 is at a high level, the three-phase thyristor drive signal SCR _ DRV _ U, SCR _ DRV _ V, SCR _ DRV _ W is normally output and input into the thyristor drive module to normally drive the thyristor.

When a phase loss occurs in one of the three phases, three optocouplers are all cut off at a position where the line voltage of the two phases is close to zero, then the output ends of the three optocouplers are all pulled up to +15V and input to the positive input end of the corresponding comparator, the negative input end is a voltage signal divided by the resistor R5 and the resistor R6, the output ends of the three optocouplers are all at high level, the grid G point of the triode Q1 is a high-level signal, the triode Q1 is switched on, the +15V power supply charges the capacitor C1 through the resistor R7 and the resistor R8, the appropriate resistor R7, the resistor R8, the resistor R9 and the resistor R10 are subjected to resistance matching to ensure that the capacitor C1 is charged and discharged, the potential of the F point of the inverting input end of the comparator U4 is always greater than the E point of the in-phase input end of the comparator U4, the negative input end of the comparator U4 is a voltage signal at two ends of the capacitor C1, the positive input end is the +15V power supply through the resistor R9, and the negative end of the power supply, When the voltage signal divided by the resistor R10 is turned on in the transistor Q1 and the capacitor C1 is charged, the comparator U4 outputs the phase-loss fault signal FO as a low level. When the two-phase line voltage deviates from the zero point, the phase optical coupler with the largest phase voltage is conducted, so that the output of the corresponding comparator is at a low level, the grid G point of the triode Q1 is a low-level signal, the triode is cut off, at the moment, the resistor R8 is discharged by the capacitor C1, and during the discharging period of the capacitor C1, the potential of the point F at the inverting input end of the comparator U4 is still higher than the point E at the non-inverting input end of the comparator U4, so that the signal of the phase-missing fault output by the comparator U4 is still at a low level. Therefore, in the whole three-phase open-phase process, the signal FO of the open-phase fault output by the comparator U4 is always in low level, the signal FO of the open-phase fault and the thyristor trigger signal SCR _ DRV1 output by the soft start system are subjected to AND operation, when the signal FO of the open-phase fault is in low level, the three-phase thyristor drive signal SCR _ DRV _ U, SCR _ DRV _ V, SCR _ DRV _ W is blocked in low level, the thyristor is not conducted when no drive signal exists, the equipment damage caused by three-phase open-phase is avoided, and the effect of open-phase protection is achieved.

In a related scheme, a power grid open-phase fault detection circuit mainly detects a power grid open-phase fault in a software mode, and the power grid open-phase fault detection circuit has the technical problems that the circuit structure is complex, the power grid change cannot be quickly responded, and the time delay is large. Compared with software mode detection in related schemes, the open-phase protection device applied to the high-power frequency converter provided by the scheme of the invention is composed of pure hardware circuits, so that the circuit structure is simple, the change of a power grid can be responded in time, and the detection timeliness of the open-phase fault of the power grid is improved. The three circuits are adopted to carry out open-phase fault protection when the input three-phase power is open-phase, and the circuit is simple in structure, small in size, safe and capable of saving cost.

Through a large number of tests, the technical scheme of the invention is adopted, a three-phase electric sampling detection circuit, a fault judgment circuit and a comparison output protection circuit are adopted to form a hardware circuit, the open-phase fault detection is carried out when the input three-phase power supply is in an open phase state, and when the three-phase open phase condition occurs, an open-phase protection signal is output to carry out open-phase protection on the circuit after the open-phase fault occurs in the power grid; therefore, the detection accuracy can be improved by adopting the hardware circuit to detect the phase loss of the three-phase power grid.

According to the embodiment of the invention, the frequency converter corresponding to the open-phase protection device of the frequency converter is also provided. The frequency converter may include: the phase-lack protection device of the frequency converter is described above.

Since the processing and functions implemented by the frequency converter of this embodiment substantially correspond to the embodiments, principles, and examples of the foregoing apparatus, reference may be made to the related descriptions in the foregoing embodiments without being detailed in the description of this embodiment.

Through a large number of tests, the technical scheme of the invention is adopted, and the three-phase electric sampling detection circuit, the fault judgment circuit and the comparison output protection circuit are adopted to form a hardware circuit, so that the open-phase fault detection is carried out when the input three-phase power supply is in an open phase state, and when the three-phase open phase condition occurs, the open-phase protection signal is output, so that the open-phase protection is carried out on the circuit after the open-phase fault occurs in the power grid, the change of the power grid can be responded in time, and the detection timeliness of the open-phase fault of the power grid is improved.

In summary, it is readily understood by those skilled in the art that the advantageous modes described above can be freely combined and superimposed without conflict.

The above description is only an example of the present invention, and is not intended to limit the present invention, and it is obvious to those skilled in the art that various modifications and variations can be made in the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the claims of the present invention.