CN107516872B - MMC converter valve submodule forward overvoltage protection circuit - Google Patents
MMC converter valve submodule forward overvoltage protection circuit Download PDFInfo
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- CN107516872B CN107516872B CN201610422763.4A CN201610422763A CN107516872B CN 107516872 B CN107516872 B CN 107516872B CN 201610422763 A CN201610422763 A CN 201610422763A CN 107516872 B CN107516872 B CN 107516872B
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- 238000006243 chemical reaction Methods 0.000 claims description 48
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- 230000002093 peripheral effect Effects 0.000 claims description 7
- 230000002159 abnormal effect Effects 0.000 claims description 6
- 230000000630 rising effect Effects 0.000 claims description 5
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/10—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers
- H02H7/12—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers
- H02H7/1213—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers for DC-DC converters
Abstract
The invention provides a forward overvoltage protection circuit for a submodule of an MMC converter valve, which comprises a main function circuit and an auxiliary function circuit; the main function circuit and the auxiliary function circuit are connected in parallel. In the forward overvoltage protection circuit of the submodule of the MMC converter valve, the electronic FOP overvoltage protection circuit of the submodule of the MMC converter valve can accurately, timely and effectively drive the bypass action of the submodule protection device under the condition of overvoltage of a direct current capacitor, so that the submodule is prevented from being damaged due to overvoltage, the FOP overvoltage protection circuit has the advantages of short time delay and small deviation value compared with the conventional BOD hardware overvoltage protection, and more reliable and accurate protection is provided for the safety of the submodule.
Description
Technical Field
The invention relates to a protection circuit, in particular to a forward overvoltage protection circuit for a submodule of an MMC converter valve.
Background
With the development of Modular Multilevel Converter (MMC) technology and engineering practice, when the Converter is over-voltage due to failure, the sub-module unit needs to have an accurate, fast and reliable over-voltage protection circuit, and the bypass unit is driven to successfully bypass and withdraw the sub-module, so as to ensure the safety of the sub-module unit.
At present, the MMC converter valve and the extra-high voltage converter valve hardware overvoltage protection circuit adopt BOD (Break overdiodes) as a main continuous protection action device for implementing overvoltage protection, but because the action voltage value of the BOD device is greatly fluctuated by the temperature influence and the action error value is large, the protection action under the given overvoltage can not be accurately carried out for a long time, the reliable hardware overvoltage protection function is greatly reduced, and the operation risk and the fault rate of a power unit are increased.
However, the forward overvoltage protection circuit fop (forward Over protect) of the electronic sub-module unit is a new circuit that can stably, accurately, timely, and reliably protect the sub-module unit from overvoltage. The protection action voltage deviation value is small, the protection action time delay is short, and the overvoltage of the submodule can be quickly responded.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a forward overvoltage protection circuit for a submodule of an MMC converter valve, which solves the problems of large deviation of an action value and long delay time of the traditional BOD overvoltage protection of the converter valve, so that the overvoltage protection of the submodule can be timely, accurate and efficient.
In order to achieve the purpose of the invention, the invention adopts the following technical scheme:
the invention provides a forward overvoltage protection circuit of a submodule of an MMC converter valve, which comprises a main function circuit and an auxiliary function circuit; the main function circuit and the auxiliary function circuit are connected in parallel.
The auxiliary function circuit comprises a DC-DC power supply conversion unit, an ultra-high precision reference voltage unit and a power supply state feedback unit;
the output end of the DC-DC power supply conversion unit is connected with the input end of the ultra-high precision reference voltage unit and is simultaneously connected with the input end of the power supply state feedback unit.
The DC-DC power supply conversion unit adopts a voltage division mode to obtain energy by the DC support capacitor, provides DC working voltage for the ultrahigh-precision reference voltage unit, and converts high voltage between the ends of the DC support capacitor into power supply voltage VCC；
The ultra-high precision reference voltage unit converts the power supply voltage VCCConversion to a reference voltage VJZAnd applying a reference voltage VJZTo the main function circuit;
the power state feedback unit displays the working state of the DC-DC power conversion unit in a level signal mode, and the power state feedback unit judges the working state of the DC-DC power conversion unit.
The power state feedback unit comprises a comparator U1, a voltage division resistor RF1, a voltage division resistor RF2, a discharge resistor R1, a current limiting resistor R2, a current limiting resistor R3, a filter capacitor CN1 and a voltage stabilizing diode DZ 1;
the cathode of the voltage stabilizing diode DZ1 is connected with the output end of the DC-DC power supply conversion unit, and the anode of the voltage stabilizing diode DZ1 is grounded through a discharge resistor R1;
the current-limiting resistor R2 and the current-limiting resistor R3 are connected in series to form an R2-R3 branch, one end of the R2-R3 branch is connected between the voltage-stabilizing diode DZ1 and the discharge resistor R1, and the other end of the R2-R3 branch is connected with the anode input end of the comparator U1;
one end of the filter capacitor CN1 is connected between the current-limiting resistor R2 and the current-limiting resistor R3, and the other end is grounded;
one end of the divider resistor RF1 is connected with the negative input end of the comparator U1, and the other end is grounded;
one end of the divider resistor RF2 is connected with the negative input end of the comparator U1, and the other end is connected with the output end of the DC-DC power conversion unit.
The main function circuit comprises a voltage acquisition unit, a reference voltage comparison unit, a double-precision monostable multivibrator and a pulse trigger unit.
The voltage acquisition unit comprises a voltage dividing resistor RF3, a voltage dividing resistor RF4, an anti-reverse diode D1, a current limiting resistor R4 and a filter capacitor CN 2;
the voltage dividing resistor RF3 and the voltage dividing resistor RF4 are connected in series and then connected in parallel to two sides of the direct current supporting capacitor, the anode of the anti-reverse diode D1 is connected with the cathode of the direct current supporting capacitor, and the cathode of the anti-reverse diode D1 is connected between the voltage dividing resistor RF3 and the voltage dividing resistor RF 4; one end of the current limiting resistor R4 is connected with the cathode of the anti-reverse diode D1, and the other end of the current limiting resistor R4 is connected with the negative electrode input end of the comparator U2; one end of the filter capacitor CN2 is connected to the negative electrode of the dc support capacitor, and the other end thereof is connected to the negative input terminal of the comparator U2.
The reference voltage comparison unit is used for judging whether the direct current support capacitor is in an overvoltage state or not, and comprises a comparator U2;
the positive pole input end of the comparator U2 is connected with the output end of the ultra-high precision reference voltage unit to obtain a reference voltage VJZThe negative input end of the comparator U2 is connected with the low-voltage end of the voltage acquisition unit, namely, the current-limiting resistor R4, and the comparator U2 is used for comparing the reference voltage VJZAnd comparing the voltage with the voltage at the low-voltage end of the voltage acquisition unit, and inputting the compared result to the double-precision monostable multivibrator.
The double-precision monostable multivibrator comprises a core chip and a peripheral circuit;
the peripheral circuit comprises a discharge capacitor CT1 and a discharge resistor RT 1; one end of the discharge capacitor CT1 is connected with the discharge resistor RT1, and the other end of the discharge capacitor CT1 is connected with the negative electrode of the direct-current support capacitor and is connected with the discharge time parameter capacitor end of the core chip; one end of the discharge resistor RT1 is connected with the discharge capacitor CT1, and the other end of the discharge resistor RT1 is connected with the output end of the DC-DC power supply conversion unit and is connected with the discharge time parameter resistor end of the core chip; the output end/R of the comparator U1 is connected with the reset end of the core chip;
the core chip generates a pulse with a time width of T according to the rising edge/falling edge of the output level inversion of the comparator U2 and the level state of the output end/R of the comparator U1, wherein T is CT1 RT 1.
The pulse trigger unit comprises a PNP Darlington tube, a pull-up resistor R5, a current-limiting resistor R6, a filter resistor RL1, a filter capacitor CL1, an anti-reverse diode D2, an anti-reverse diode D3, a pull-down resistor R7 and a TVS;
the filter resistor RL1 and the filter capacitor CL1 are connected in parallel to form an RL1// CL1 branch, and the pull-down resistor R7, the TVS and the anti-reflection diode D3 are connected in parallel to form an R7// TVS// D3 branch; one end of the RL1// CL1 branch is connected with a collector of a PNP Darlington tube, the other end of the RL1// CL1 branch is connected with an anode of an anti-reflection diode D2, and a cathode of the anti-reflection diode D2 is grounded through an R7// TVS// D3 branch; the emitting electrode of the PNP Darlington tube is directly connected with a power supply voltage VCCThe base electrode of the pull-up resistor R5 is connected with the output end of the double-precision monostable multivibrator through a current-limiting resistor R6, one end of the pull-up resistor R5 is connected with the output end of the double-precision monostable multivibrator, and the other end of the pull-up resistor R5 is connected with a power supply voltage VCCAnd (4) connecting.
The power state feedback unit judges the working state of the DC-DC power conversion unit, and comprises the following steps:
1) when the power supply voltage VCCAbove 8.6V, the Zener diode DZ1 is in breakdown state, and the voltage V of Zener diode DZ1DZ14.3V, 0.5W, and the input voltage at the positive input of the comparator U1 is VCC-VDZ1Due to the supply voltage VCCIs in the range of 10V to 15V, the input voltage of the positive input terminal of the comparator U1 is in the range of 5.7V to 10.7V, and the negative input of the comparator U1Input voltage at input terminal is VCC(RF1/(RF2+ RF1)) ranging from 5V to 7.5V, and since the input voltage at the positive input terminal is greater than the input voltage at the negative input terminal, the output terminal/R of the comparator U1 is at a high level, indicating that the operating state of the DC-DC power conversion unit is normal;
2) when the power supply voltage VCCWhen the voltage is lower than 8.6V, the input voltage of the positive input end and the input voltage of the negative input end of the comparator U1 are both lower than 4.3V, and the power supply voltage VCCThe lower the voltage difference between the input voltage of the positive input terminal and the input voltage of the negative input terminal is, the larger the voltage difference is, and therefore, the output/R of the comparator U1 is at a low level, which indicates that the operating state of the DC-DC power conversion unit is abnormal.
Compared with the closest prior art, the technical scheme provided by the invention has the following beneficial effects:
in the forward overvoltage protection circuit of the submodule of the MMC converter valve, the electronic FOP overvoltage protection circuit of the submodule of the MMC converter valve can accurately, timely and effectively drive the bypass action of the submodule protection device under the condition of overvoltage of a direct current capacitor, so that the submodule is prevented from being damaged due to overvoltage, the FOP overvoltage protection circuit has the advantages of short time delay and small deviation value compared with the conventional BOD hardware overvoltage protection, and more reliable and accurate protection is provided for the safety of the submodule.
Drawings
FIG. 1 is a schematic diagram of an auxiliary function circuit in an embodiment of the present invention;
FIG. 2 is a schematic diagram of a main function circuit in an embodiment of the invention;
fig. 3 is a diagram of a theoretical output waveform in an embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings.
The invention provides a forward overvoltage protection circuit of a submodule of an MMC converter valve, which comprises a main function circuit and an auxiliary function circuit; the main function circuit and the auxiliary function circuit are connected in parallel.
As shown in fig. 1, the auxiliary function circuit includes a DC-DC power conversion unit, an ultra-high precision reference voltage unit, and a power state feedback unit;
the output end of the DC-DC power supply conversion unit is connected with the input end of the ultra-high precision reference voltage unit and is simultaneously connected with the input end of the power supply state feedback unit.
The DC-DC power supply conversion unit adopts a voltage division mode to obtain energy by the DC support capacitor, provides DC working voltage for the ultrahigh-precision reference voltage unit, and converts high voltage between the ends of the DC support capacitor into power supply voltage VCC；
The ultra-high precision reference voltage unit converts the power supply voltage VCCConversion to a reference voltage VJZAnd applying a reference voltage VJZTo the main function circuit;
the power state feedback unit displays the working state of the DC-DC power conversion unit in a level signal mode, and the power state feedback unit judges the working state of the DC-DC power conversion unit.
The power state feedback unit comprises a comparator U1, a voltage division resistor RF1, a voltage division resistor RF2, a discharge resistor R1, a current limiting resistor R2, a current limiting resistor R3, a filter capacitor CN1 and a voltage stabilizing diode DZ 1;
the cathode of the voltage stabilizing diode DZ1 is connected with the output end of the DC-DC power supply conversion unit, and the anode of the voltage stabilizing diode DZ1 is grounded through a discharge resistor R1;
the current-limiting resistor R2 and the current-limiting resistor R3 are connected in series to form an R2-R3 branch, one end of the R2-R3 branch is connected between the voltage-stabilizing diode DZ1 and the discharge resistor R1, and the other end of the R2-R3 branch is connected with the anode input end of the comparator U1;
one end of the filter capacitor CN1 is connected between the current-limiting resistor R2 and the current-limiting resistor R3, and the other end is grounded;
one end of the divider resistor RF1 is connected with the negative input end of the comparator U1, and the other end is grounded;
one end of the divider resistor RF2 is connected with the negative input end of the comparator U1, and the other end is connected with the output end of the DC-DC power conversion unit.
As shown in fig. 2, the main function circuit includes a voltage acquisition unit, a reference voltage comparison unit, a double-precision monostable multivibrator and a pulse trigger unit.
The voltage acquisition unit comprises a voltage dividing resistor RF3, a voltage dividing resistor RF4, an anti-reverse diode D1, a current limiting resistor R4 and a filter capacitor CN 2;
the voltage dividing resistor RF3 and the voltage dividing resistor RF4 are connected in series and then connected in parallel to two sides of the direct current supporting capacitor, the anode of the anti-reverse diode D1 is connected with the cathode of the direct current supporting capacitor, and the cathode of the anti-reverse diode D1 is connected between the voltage dividing resistor RF3 and the voltage dividing resistor RF 4; one end of the current limiting resistor R4 is connected with the cathode of the anti-reverse diode D1, and the other end of the current limiting resistor R4 is connected with the negative electrode input end of the comparator U2; one end of the filter capacitor CN2 is connected to the negative electrode of the dc support capacitor, and the other end thereof is connected to the negative input terminal of the comparator U2.
The reference voltage comparison unit is used for judging whether the direct current support capacitor is in an overvoltage state or not, and comprises a comparator U2;
the positive pole input end of the comparator U2 is connected with the output end of the ultra-high precision reference voltage unit to obtain a reference voltage VJZThe negative input end of the comparator U2 is connected with the low-voltage end of the voltage acquisition unit, namely, the current-limiting resistor R4, and the comparator U2 is used for comparing the reference voltage VJZAnd comparing the voltage with the voltage at the low-voltage end of the voltage acquisition unit, and inputting the compared result to the double-precision monostable multivibrator.
The double-precision monostable multivibrator comprises a core chip and a peripheral circuit;
the peripheral circuit comprises a discharge capacitor CT1 and a discharge resistor RT 1; one end of the discharge capacitor CT1 is connected with the discharge resistor RT1, and the other end of the discharge capacitor CT1 is connected with the negative electrode of the direct-current support capacitor and is connected with the discharge time parameter capacitor end of the core chip; one end of the discharge resistor RT1 is connected with the discharge capacitor CT1, and the other end of the discharge resistor RT1 is connected with the output end of the DC-DC power supply conversion unit and is connected with the discharge time parameter resistor end of the core chip; the output end/R of the comparator U1 is connected with the reset end of the core chip;
the core chip generates a pulse with a time width of T according to the rising edge/falling edge of the output level inversion of the comparator U2 and the level state of the output end/R of the comparator U1, wherein T is CT1 RT 1.
The pulse trigger unit comprises a PNP Darlington tube, a pull-up resistor R5, a current-limiting resistor R6, a filter resistor RL1, a filter capacitor CL1, an anti-reflection diode D2, an anti-reflection diode D3, a pull-down resistor R7 and a TVS (TRANSIENT VOLTAGES UPPRESSOR);
the filter resistor RL1 and the filter capacitor CL1 are connected in parallel to form an RL1// CL1 branch, and the pull-down resistor R7, the TVS and the anti-reflection diode D3 are connected in parallel to form an R7// TVS// D3 branch; one end of the RL1// CL1 branch is connected with a collector of a PNP Darlington tube, the other end of the RL1// CL1 branch is connected with an anode of an anti-reflection diode D2, and a cathode of the anti-reflection diode D2 is grounded through an R7// TVS// D3 branch; the emitting electrode of the PNP Darlington tube is directly connected with a power supply voltage VCCThe base electrode of the pull-up resistor R5 is connected with the output end of the double-precision monostable multivibrator through a current-limiting resistor R6, one end of the pull-up resistor R5 is connected with the output end of the double-precision monostable multivibrator, and the other end of the pull-up resistor R5 is connected with a power supply voltage VCCAnd (4) connecting.
The working principle of the auxiliary function circuit is as follows:
firstly, the DC-DC power supply conversion unit with high isolation performance converts the high voltage of the direct current support capacitor of the submodule into a power supply voltage VCC，VCCThe voltage of the auxiliary function circuit is determined by the selection of the DC-DC power supply conversion unit and the device of the auxiliary function circuitCCThe range of (A) is 10V-15V; second, VCCThe reference voltage V is determined by the conversion of the ultrahigh-precision reference voltage conversion unit and the selection of the overvoltage set value of the submoduleJZThe voltage of the direct current support capacitor is 2.5V, and the voltage is used for comparing and judging the voltage of the direct current support capacitor by the main function circuit to determine whether an overvoltage condition exists or not, and the ultrahigh-precision reference voltage conversion unit has the characteristics of high precision and stable output; the power state feedback unit judges the working state of the DC-DC power conversion unit, and comprises the following steps:
1) when the power supply voltage VCCAbove 8.6V, the Zener diode DZ1 is in breakdown state, and the voltage V of Zener diode DZ1DZ14.3V, 0.5W, and the input voltage at the positive input of the comparator U1 is VCC-VDZ1Due to the supply voltage VCCIs in the range of 10V to 15V, the input voltage at the positive input terminal of the comparator U1 is in the range of 5.7V to 10.7V, and the input voltage at the negative input terminal of the comparator U1 is VCC(RF1/(RF2+ RF1)) ranging from 5V to 7.5V, and since the input voltage at the positive input terminal is greater than the input voltage at the negative input terminal, the output terminal/R of the comparator U1 is at a high level, indicating that the operating state of the DC-DC power conversion unit is normal;
2) when the power supply voltage VCCWhen the voltage is lower than 8.6V, the input voltage of the positive input end and the input voltage of the negative input end of the comparator U1 are both lower than 4.3V, and the power supply voltage VCCThe lower the voltage difference between the input voltage of the positive input terminal and the input voltage of the negative input terminal is, the larger the voltage difference is, and therefore, the output/R of the comparator U1 is at a low level, which indicates that the operating state of the DC-DC power conversion unit is abnormal. The output end/R of the comparator U1 is sent to the main functional circuit, and when the DC-DC power supply conversion unit works normally, the main functional circuit continuously and effectively works; when the DC-DC power conversion unit works abnormally, no matter whether the main functional circuit detects overvoltage, the DC-DC power conversion unit does not start to trigger the overvoltage protection device to act due to the abnormal work of the DC-DC power conversion unit.
The working principle of the main functional circuit is as follows:
the voltage acquisition unit acquires low voltage suitable for secondary equipment from the submodule direct current supporting capacitor with high voltage through a voltage dividing resistor RF3 and a voltage dividing resistor RF4 which are connected in series, and filters and stabilizes the voltage value; the reference voltage comparator then obtains the 2.5V reference voltage VJZCompared with the secondary low voltage obtained by the voltage acquisition unit, when the secondary low voltage obtained by voltage division is less than 2.5V, the comparator U2 outputs high level, and when the secondary low voltage is more than 2.5V, the comparator U2 outputs low level.
When the double-precision monostable multivibrator judges that the level output by the comparator U2 changes (namely, a rising edge and a falling edge) when the output end/R of the comparator U1 is in a high level state, when the level changes from high to low (namely, a falling edge), the voltage of a sub-module capacitor is determined to be in an overvoltage state, the double-precision monostable multivibrator does not output negative pulses, the pulse width is determined by a discharge capacitor CT1 and a discharge resistor RT1, at the moment, the PNP Darlington tube turns on to invert the negative pulses into positive pulses with equal pulse width and the energy is increased, a trigger action pulse of a protection device is output and formed by an anti-reverse diode D2, wherein the anti-reverse diode D2 also has the function of preventing the voltage from reversely entering the Darlington tube, the anti-reverse diode D3 has the function of preventing the G-K trigger pulse from reversely damaging a rear-stage trigger action device, and the TVS is used for clamping the G-K voltage and, the stable voltage selected by the TVS is 18V; when the level is changed from low to high (namely rising edge), the non-output of the double-precision monostable multivibrator is positive pulse, the PNP Darlington tube is in an off state, no pulse is output between G and K, G is pulled down by the pull-down resistor R7, and the voltage difference between G and K is basically zero, so that the direct-current support capacitor of the submodule has no overvoltage.
When the output end/R of the comparator U1 is in a low level state, the double-precision monostable multivibrator indicates that the output of the DC-DC power supply conversion unit is abnormal, and the output of the double-precision monostable multivibrator keeps unchanged no matter whether the submodule has overvoltage or not, and a rear-stage circuit is not driven, so that the protection action of the protection device is prevented from being triggered by mistake when the power-on start or the fault of the DC/DC power supply conversion unit occurs.
The invention adopts a mode of directly taking energy by high voltage, realizes the conversion of high voltage and low voltage, and avoids introducing external control voltage which is easy to be interfered;
according to the invention, a high-precision reference voltage device is adopted to design, so that accurate reference voltage is generated, the judgment value of overvoltage is more accurate, the overlarge deviation of the overvoltage value is avoided, and the operation risk of a submodule is increased;
the invention realizes the self-checking of the working state of the power supply and has the reliability of the protection of the power supply against the abnormal operation;
the invention adopts the electronic integrated rapid overvoltage protection action design, and has the advantages of short overvoltage protection action delay and high action accuracy compared with the BOD single-device hardware;
the width of the trigger pulse of the protection device is determined by the peripheral capacitance-resisting device, and the pulse width can be conveniently and freely adjusted according to the requirement.
The invention can adjust the over-voltage protection value of the FOP according to the adjustment of the resistance value of the divider resistor RF3 or the divider resistor RF 4.
Finally, it should be noted that: the above embodiments are only intended to illustrate the technical solution of the present invention and not to limit the same, and a person of ordinary skill in the art can make modifications or equivalents to the specific embodiments of the present invention with reference to the above embodiments, and such modifications or equivalents without departing from the spirit and scope of the present invention are within the scope of the claims of the present invention as set forth in the claims.
Claims (8)
1. The utility model provides a forward overvoltage protection circuit of MMC converter valve submodule piece which characterized in that: the forward overvoltage protection circuit comprises a main function circuit and an auxiliary function circuit; the main function circuit and the auxiliary function circuit are connected in parallel;
the auxiliary function circuit comprises a DC-DC power supply conversion unit, an ultra-high precision reference voltage unit and a power supply state feedback unit;
the output end of the DC-DC power supply conversion unit is connected with the input end of the ultra-high precision reference voltage unit and is also connected with the input end of the power supply state feedback unit;
the DC-DC power supply conversion unit adopts a voltage division mode to obtain energy by the DC support capacitor, provides DC working voltage for the ultrahigh-precision reference voltage unit, and converts high voltage between the ends of the DC support capacitor into power supply voltage VCC；
The ultra-high precision reference voltage unit converts the power supply voltage VCCConversion to a reference voltage VJZAnd applying a reference voltage VJZTo the main function circuit;
the power state feedback unit displays the working state of the DC-DC power conversion unit in a level signal mode, and the power state feedback unit judges the working state of the DC-DC power conversion unit.
2. The MMC converter valve sub-module forward overvoltage protection circuit of claim 1, wherein: the power state feedback unit comprises a comparator U1, a voltage division resistor RF1, a voltage division resistor RF2, a discharge resistor R1, a current limiting resistor R2, a current limiting resistor R3, a filter capacitor CN1 and a voltage stabilizing diode DZ 1;
the cathode of the voltage stabilizing diode DZ1 is connected with the output end of the DC-DC power supply conversion unit, and the anode of the voltage stabilizing diode DZ1 is grounded through a discharge resistor R1;
the current-limiting resistor R2 and the current-limiting resistor R3 are connected in series to form an R2-R3 branch, one end of the R2-R3 branch is connected between the voltage-stabilizing diode DZ1 and the discharge resistor R1, and the other end of the R2-R3 branch is connected with the anode input end of the comparator U1;
one end of the filter capacitor CN1 is connected between the current-limiting resistor R2 and the current-limiting resistor R3, and the other end is grounded;
one end of the divider resistor RF1 is connected with the negative input end of the comparator U1, and the other end is grounded;
one end of the divider resistor RF2 is connected with the negative input end of the comparator U1, and the other end is connected with the output end of the DC-DC power conversion unit.
3. The MMC converter valve sub-module forward overvoltage protection circuit of claim 2, wherein: the main function circuit comprises a voltage acquisition unit, a reference voltage comparison unit, a double-precision monostable multivibrator and a pulse trigger unit.
4. The MMC converter valve sub-module forward overvoltage protection circuit of claim 3, wherein: the voltage acquisition unit comprises a voltage dividing resistor RF3, a voltage dividing resistor RF4, an anti-reverse diode D1, a current limiting resistor R4 and a filter capacitor CN 2;
the voltage dividing resistor RF3 and the voltage dividing resistor RF4 are connected in series and then connected in parallel to two sides of the direct current supporting capacitor, the anode of the anti-reverse diode D1 is connected with the cathode of the direct current supporting capacitor, and the cathode of the anti-reverse diode D1 is connected between the voltage dividing resistor RF3 and the voltage dividing resistor RF 4; one end of the current limiting resistor R4 is connected with the cathode of the anti-reverse diode D1, and the other end of the current limiting resistor R4 is connected with the negative electrode input end of the comparator U2; one end of the filter capacitor CN2 is connected to the negative electrode of the dc support capacitor, and the other end thereof is connected to the negative input terminal of the comparator U2.
5. The MMC converter valve sub-module forward overvoltage protection circuit of claim 4, wherein: the reference voltage comparison unit is used for judging whether the direct current support capacitor is in an overvoltage state or not, and comprises a comparator U2;
the positive pole input end of the comparator U2 is connected with the output end of the ultra-high precision reference voltage unit to obtain a reference voltage VJZThe negative input end of the comparator U2 is connected with the low-voltage end of the voltage acquisition unit, namely, the current-limiting resistor R4, and the comparator U2 is used for comparing the reference voltage VJZAnd comparing the voltage with the voltage at the low-voltage end of the voltage acquisition unit, and inputting the compared result to the double-precision monostable multivibrator.
6. The MMC converter valve sub-module forward overvoltage protection circuit of claim 5, wherein: the double-precision monostable multivibrator comprises a core chip and a peripheral circuit;
the peripheral circuit comprises a discharge capacitor CT1 and a discharge resistor RT 1; one end of the discharge capacitor CT1 is connected with the discharge resistor RT1, and the other end of the discharge capacitor CT1 is connected with the negative electrode of the direct-current support capacitor and is connected with the discharge time parameter capacitor end of the core chip; one end of the discharge resistor RT1 is connected with the discharge capacitor CT1, and the other end of the discharge resistor RT1 is connected with the output end of the DC-DC power supply conversion unit and is connected with the discharge time parameter resistor end of the core chip; the output end/R of the comparator U1 is connected with the reset end of the core chip;
the core chip generates a pulse with a time width of T according to the rising edge/falling edge of the output level inversion of the comparator U2 and the level state of the output end/R of the comparator U1, wherein T is CT1 RT 1.
7. The MMC converter valve sub-module forward overvoltage protection circuit of claim 3, wherein: the pulse trigger unit comprises a PNP Darlington tube, a pull-up resistor R5, a current-limiting resistor R6, a filter resistor RL1, a filter capacitor CL1, an anti-reverse diode D2, an anti-reverse diode D3, a pull-down resistor R7 and a TVS;
the filter resistor RL1 and the filter capacitor CL1 are connected in parallel to form an RL1// CL1 branch, and the pull-down resistorThe R7, the TVS and the anti-reverse diode D3 are connected in parallel to form a branch R7// TVS// D3; one end of the RL1// CL1 branch is connected with a collector of a PNP Darlington tube, the other end of the RL1// CL1 branch is connected with an anode of an anti-reflection diode D2, and a cathode of the anti-reflection diode D2 is grounded through an R7// TVS// D3 branch; the emitting electrode of the PNP Darlington tube is directly connected with a power supply voltage VCCThe base electrode of the pull-up resistor R5 is connected with the output end of the double-precision monostable multivibrator through a current-limiting resistor R6, one end of the pull-up resistor R5 is connected with the output end of the double-precision monostable multivibrator, and the other end of the pull-up resistor R5 is connected with a power supply voltage VCCAnd (4) connecting.
8. The MMC converter valve sub-module forward overvoltage protection circuit of claim 7, wherein: the power state feedback unit judges the working state of the DC-DC power conversion unit, and comprises the following steps:
1) when the power supply voltage VCCAbove 8.6V, the Zener diode DZ1 is in breakdown state, and the voltage V of Zener diode DZ1DZ14.3V, 0.5W, and the input voltage at the positive input of the comparator U1 is VCC-VDZ1Due to the supply voltage VCCIs in the range of 10V to 15V, the input voltage at the positive input terminal of the comparator U1 is in the range of 5.7V to 10.7V, and the input voltage at the negative input terminal of the comparator U1 is VCC(RF1/(RF2+ RF1)) ranging from 5V to 7.5V, and since the input voltage at the positive input terminal is greater than the input voltage at the negative input terminal, the output terminal/R of the comparator U1 is at a high level, indicating that the operating state of the DC-DC power conversion unit is normal;
2) when the power supply voltage VCCWhen the voltage is lower than 8.6V, the input voltage of the positive input end and the input voltage of the negative input end of the comparator U1 are both lower than 4.3V, and the power supply voltage VCCThe lower the voltage difference between the input voltage of the positive input terminal and the input voltage of the negative input terminal is, the larger the voltage difference is, and therefore, the output/R of the comparator U1 is at a low level, which indicates that the operating state of the DC-DC power conversion unit is abnormal.
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| CN111830313A (en) * | 2020-07-07 | 2020-10-27 | 国网福建省电力有限公司电力科学研究院 | Transient overvoltage broadband monitoring system for modular multilevel converter |
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| CN201222647Y (en) * | 2008-06-27 | 2009-04-15 | 上海亿盟电气自动化技术有限公司 | Switch power source |
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