CN113595372A - Protection circuit, application device thereof and circuit protection method - Google Patents

Protection circuit, application device thereof and circuit protection method Download PDF

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Publication number
CN113595372A
CN113595372A CN202110857170.1A CN202110857170A CN113595372A CN 113595372 A CN113595372 A CN 113595372A CN 202110857170 A CN202110857170 A CN 202110857170A CN 113595372 A CN113595372 A CN 113595372A
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Prior art keywords
circuit
voltage
current
protection
preset
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CN202110857170.1A
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Inventor
李必杰
周朋飞
吴风雷
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Sungrow Power Supply Co Ltd
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Sungrow Power Supply Co Ltd
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Priority to CN202110857170.1A priority Critical patent/CN113595372A/en
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/32—Means for protecting converters other than automatic disconnection
    • 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
    • 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
    • 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
    • H02H7/122—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 inverters, i.e. dc/ac converters
    • 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
    • H02H7/125—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 rectifiers
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
    • H02M7/5387—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Inverter Devices (AREA)

Abstract

The invention provides a protection circuit, an application device thereof and a circuit protection method, which are applied to the technical field of power electronics. According to the invention, the circuit to be protected is protected only when the target working voltage is greater than the preset voltage threshold and the target working current is greater than the preset current threshold, so that the protection is more comprehensive, and the reliability of the circuit operation is improved due to the improvement of the accuracy of fault identification.

Description

Protection circuit, application device thereof and circuit protection method
Technical Field
The present invention relates to the field of power electronics technologies, and in particular, to a protection circuit, an application device thereof, and a circuit protection method.
Background
With the development of power electronic technology, power conversion circuits implemented based on controllable power elements such as IGBTs are more and more widely used, such as rectification circuits, inverter circuits, and dc power circuits, and in order to protect the operation safety of the power conversion circuits, corresponding protection circuits are often required to be arranged in the power conversion circuits.
The inventor researches and discovers that in the prior art, the coupling relation between a controllable power element and working voltage and working current in the operation process of the power conversion circuit is mostly not considered for the protection of the power conversion circuit, the mutual influence of the working voltage and the working current is neglected, the fault identification accuracy is not high, the protection effect is good, and the reliability of the circuit operation is influenced.
Disclosure of Invention
The invention provides a protection circuit, an application device thereof and a circuit protection method, which are used for simultaneously comparing the working voltage and the working current of a circuit to be protected and protecting the circuit under the condition that the target working voltage is greater than a preset voltage threshold and the target working current is greater than a preset current threshold, so that the protection is more comprehensive, and the reliability of the operation of the circuit is improved due to the improvement of the accuracy of fault identification.
In order to achieve the purpose, the technical scheme provided by the invention is as follows:
in a first aspect, the present invention provides a protection circuit comprising: a voltage acquisition circuit, a current acquisition circuit and a comparison circuit, wherein,
the voltage acquisition circuit and the current acquisition circuit are respectively connected with a circuit to be protected;
the comparison circuit is respectively connected with the voltage acquisition circuit and the current acquisition circuit;
the voltage acquisition circuit acquires a target working voltage of the circuit to be protected;
the current acquisition circuit acquires a target working current of the circuit to be protected;
and the comparison circuit outputs a protection signal for triggering a preset protection measure under the condition that the target working voltage is greater than a preset voltage threshold and the target working current is greater than a preset current threshold.
Optionally, the comparison circuit sets at least one set of threshold value pairs, and any one set of threshold value pairs includes a preset voltage threshold value and a preset current threshold value;
the comparison circuit outputs the protection signal when the target working voltage is greater than a preset voltage threshold value of a target threshold value pair and the target working current is greater than a preset current threshold value of the target threshold value pair;
wherein the target threshold value pair is any one of the threshold value pairs.
Optionally, the preset voltage threshold of any one of the threshold pairs is determined based on the working current of the circuit to be protected and the bus voltage of the circuit to be protected;
and determining the preset current threshold value of any threshold value pair based on the working current of the circuit to be protected.
Optionally, under the condition that the threshold pairs are arranged from low to high according to the preset voltage threshold, the preset current threshold of each threshold pair is arranged from high to low.
Optionally, the comparison circuit includes at least one comparison sub-circuit;
the input end of each comparison sub-circuit is used as the input end of the comparison circuit;
the output end of each comparison sub-circuit is used as the output end of the comparison circuit;
each of the comparison sub-circuits corresponds to a different threshold value pair.
Optionally, the comparison sub-circuit includes: a current comparison circuit, a voltage comparison circuit, and a signal output circuit, wherein,
the input end of the current comparison circuit is used as the first input end of the comparison sub-circuit;
the input end of the voltage comparison circuit is used as a second input end of the comparison sub-circuit;
the output end of the current comparison circuit is connected with the first input end of the signal output circuit;
the output end of the voltage comparison circuit is connected with the second input end of the signal output circuit;
the current comparison circuit outputs a first driving signal under the condition that the target working current is greater than a corresponding preset current threshold value;
the voltage comparison circuit outputs a second driving signal under the condition that the target working voltage is greater than a corresponding preset voltage threshold;
the signal output circuit outputs the protection signal when receiving the first drive signal and the second drive signal.
Optionally, the current comparison circuit comprises a first operational amplifier, wherein,
a first input end of the first operational amplifier is connected with a first reference voltage, and the first reference voltage is obtained by converting based on a preset current threshold corresponding to the current comparison circuit;
a second input end of the first operational amplifier is used as an input end of the current comparison circuit;
and the output end of the first operational amplifier is used as the output end of the current comparison circuit.
Optionally, the current comparison circuit further comprises a second operational amplifier, wherein,
a second input end of the second operational amplifier is connected to the first reference voltage;
a connection point of a first input end of the second operational amplifier and a second input end of the first operational amplifier is used as an input end of the current comparison circuit;
a connection point of an output end of the first operational amplifier and an output end of the second operational amplifier is used as an output end of the current comparison circuit;
wherein the first input terminal of the second operational amplifier is of the same polarity as the first input terminal of the first operational amplifier.
Optionally, the voltage comparison circuit comprises a third operational amplifier, wherein,
a first input end of the third operational amplifier is connected with a second reference voltage, and the voltage value of the second reference voltage is a preset voltage threshold value corresponding to the voltage comparison circuit;
a second input end of the third operational amplifier is used as an input end of the voltage comparison circuit;
and the output end of the third operational amplifier is used as the output end of the voltage comparison circuit.
Optionally, the signal output circuit comprises an and gate circuit, wherein,
a first input end of the AND gate circuit is used as a first input end of the signal output circuit;
a second input end of the AND gate circuit is used as a second input end of the signal output circuit;
and the output end of the AND gate circuit is used as the output end of the signal output circuit.
Optionally, the signal output circuit further includes: a first pull-up circuit and a second pull-up circuit, wherein,
the first pull-up circuit is connected with a first input end of the signal output circuit;
the second pull-up circuit is connected to a second input terminal of the signal output circuit.
Optionally, the voltage acquisition circuit includes: a voltage acquisition sub-circuit and a first selection circuit, wherein,
the input end of the voltage acquisition sub-circuit is used as the input end of the voltage acquisition circuit;
the output end of the voltage acquisition sub-circuit is connected with the input end of the first selection circuit;
the output end of the first selection circuit is used as the output end of the voltage acquisition circuit;
the voltage acquisition sub-circuit acquires positive half bus voltage and negative half bus voltage of the circuit to be protected;
the first selection circuit outputs a larger bus voltage of the positive half bus voltage and the negative half bus voltage as the target operating voltage.
Optionally, the current collecting circuit includes: a current collection sub-circuit and a second selection circuit, wherein,
the input end of the current acquisition sub-circuit is used as the input end of the current acquisition circuit;
the output end of the current acquisition sub-circuit is connected with the input end of the second selection circuit;
the output end of the second selection circuit is used as the output end of the current acquisition circuit;
the current acquisition sub-circuit acquires a plurality of working currents of the circuit to be protected;
the second selection circuit outputs the largest working current of the working currents as the target working current.
Optionally, the current collecting circuit further includes: a voltage conversion circuit, wherein,
the voltage conversion circuit is connected in series between the current acquisition sub-circuit and the second selection circuit;
the voltage conversion circuit converts the plurality of working currents of the circuit to be protected, which are acquired by the current acquisition sub-circuit, into corresponding sampling voltages respectively;
the second selection circuit is used for outputting the largest sampling voltage in the sampling voltages so as to represent the target working current.
Optionally, the protection circuit provided by any one of the first aspect of the present invention further includes: the protection controller is configured to, among other things,
the protection controller is respectively connected with the output end of the comparison circuit and the circuit to be protected;
and the protection controller receives the protection signal and executes the preset protection measures.
Optionally, the preset protection measure includes at least one of the following measures:
reducing the bus voltage of the circuit to be protected;
reducing the change rate of the working current of the circuit to be protected;
controlling the circuit to be protected to stop operating;
and controlling a controllable switching tube in the circuit to be protected to be in a conducting or switching-off state.
Optionally, the process of reducing, by the protection controller, the change rate of the operating current of the circuit to be protected includes:
and reducing the working current of the circuit to be protected, or reducing the switching-on speed of a controllable switch tube in the circuit to be protected.
In a second aspect, the present invention provides a power converter comprising: the power conversion main circuit, the power conversion controller, and the protection circuit according to any one of the first aspect of the present invention,
the power conversion controller is connected with the power conversion main circuit and controls the working process of the power conversion circuit;
the protection circuit is connected with the power conversion main circuit.
Optionally, the power conversion controller includes a protection controller in the protection circuit.
Optionally, the power conversion main circuit includes an inverter circuit, a rectifier circuit, and a DC/DC circuit.
In a third aspect, the present invention provides a three-level inverter, comprising: a three-level inverter circuit, an inverter controller, and a protection circuit according to any one of the first aspect of the present invention,
the three-level inverter circuit comprises a positive half bus capacitor, a negative half bus capacitor and a three-phase inverter bridge arm, wherein,
the positive half bus capacitor and the negative half bus capacitor are connected in series to form a capacitor series branch;
all the inverter bridge arms are connected in parallel to form bridge arm parallel branches;
the positive end of the capacitor series branch is connected with the positive end of the bridge arm parallel branch, and the negative end of the capacitor series branch is connected with the negative end of the bridge arm parallel branch;
the connection point of the positive half bus capacitor and the negative half bus capacitor is respectively connected with each inverter bridge arm;
the inverter controller is connected with the three-level inverter circuit and controls the working process of the three-level inverter circuit;
and the protection circuit is connected with the three-level inverter circuit.
In a fourth aspect, the present invention provides a circuit protection method, including:
acquiring a target working current and a target working voltage of a circuit to be protected;
and if the target working voltage is greater than a preset voltage threshold value and the target working current is greater than a preset current threshold value, outputting a protection signal for triggering a preset protection measure.
Optionally, at least one set of threshold value pairs is preset, and any one set of threshold value pairs comprises a preset voltage threshold value and a preset current threshold value;
if the target working voltage is greater than a preset voltage threshold and the target working current is greater than a preset current threshold, outputting a protection signal triggering a preset protection measure, including:
if the target working voltage is greater than a preset voltage threshold value of a target threshold value pair, and the target working current is greater than a preset current threshold value of the target threshold value pair, outputting a protection signal for triggering a preset protection measure;
wherein the target threshold value pair is any one of the threshold value pairs.
Optionally, under the condition that the threshold pairs are arranged from low to high according to the preset voltage threshold, the preset current threshold of each threshold pair is arranged from high to low.
Optionally, the process of generating any one of the threshold value pairs includes:
acquiring the working current and half bus voltage of the circuit to be protected;
determining a preset voltage threshold corresponding to the working current according to the working current of the circuit to be protected and the half bus voltage;
determining a preset current threshold corresponding to the working current;
and taking the preset current threshold value and the preset voltage threshold value as a group of threshold value pairs.
Optionally, the determining a preset voltage threshold corresponding to the working current according to the working current of the circuit to be protected and the half-bus voltage includes:
inputting the working current and the half-bus voltage of the circuit to be protected into the following formula to obtain a preset voltage threshold corresponding to the working current:
Figure BDA0003184492500000061
wherein, UZRepresents a preset voltage threshold;
l represents the equivalent inductance of the circuit to be protected;
di represents the variation of the working current of the circuit to be protected;
dt represents the time length of switching the power element in the circuit to be protected from the on state to the off state;
UBUSrepresenting the half-bus voltage of the circuit to be protected.
The protection circuit provided by the invention comprises a voltage acquisition circuit, a current acquisition circuit and a comparison circuit, wherein the voltage acquisition circuit and the current acquisition circuit are respectively connected with a circuit to be protected, the comparison circuit is respectively connected with the voltage acquisition circuit and the current acquisition circuit, the voltage acquisition circuit acquires target working voltage of the circuit to be protected, the current acquisition circuit acquires target working current of the circuit to be protected, and the comparison circuit outputs a protection signal for triggering a preset protection measure under the condition that the target working voltage is greater than a preset voltage threshold and the target working current is greater than a preset current threshold. The protection circuit provided by the invention can simultaneously compare the working voltage and the working current of the circuit to be protected, and protect the circuit to be protected under the condition that the target working voltage is greater than the preset voltage threshold and the target working current is greater than the preset current threshold.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a block diagram of a protection circuit according to an embodiment of the present invention;
fig. 2 is a corresponding relationship between peak voltage and operating current of the power device according to the embodiment of the invention;
fig. 3 is a schematic diagram of a protection range of a protection circuit according to an embodiment of the present invention;
fig. 4 is a block diagram of another protection circuit according to an embodiment of the present invention;
FIG. 5 is a circuit topology diagram of a comparison circuit according to an embodiment of the present invention;
FIG. 6 is a circuit topology diagram of another comparison circuit provided by an embodiment of the present invention;
FIG. 7 is a circuit topology diagram of yet another comparison circuit provided by an embodiment of the present invention;
fig. 8 is a circuit topology diagram of a protection circuit according to an embodiment of the present invention;
fig. 9 is a circuit topology diagram of a three-level inverter circuit of a three-level inverter according to an embodiment of the present invention;
fig. 10 is a flowchart of a circuit protection method according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. 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 application.
Referring to fig. 1, fig. 1 is a block diagram of a protection circuit according to an embodiment of the present invention, where the protection circuit includes: a voltage acquisition circuit 10, a current acquisition circuit 20, and a comparison circuit 30, wherein,
the input end of the voltage acquisition circuit 10 is connected to the circuit to be protected 40 to acquire the target working voltage of the circuit to be protected 40, and correspondingly, the input end of the current acquisition circuit 20 is also connected to the circuit to be protected 40 to acquire the target working current of the circuit to be protected 40. The output end of the voltage acquisition circuit 10 and the output end of the current acquisition circuit 20 are respectively connected with the input end of the comparison circuit 30, and the acquired target working voltage and target working current are transmitted to the comparison circuit 30.
The comparison circuit 30 compares the obtained target working voltage with a preset voltage threshold, compares the obtained target working current with a preset current threshold, and outputs a protection signal for triggering a preset protection measure when the target working voltage is greater than the preset voltage threshold and the target working current is greater than the preset current threshold, so that a device or a controller receiving the protection signal executes the preset protection measure.
In practical application, the circuit to be protected 40 may be a power conversion circuit implemented based on power elements such as IGBTs, such as an inverter circuit, a rectifier circuit, and a DC/DC conversion circuit, and may also be other circuits requiring overvoltage protection and overcurrent protection.
In summary, the protection circuit provided by the invention can simultaneously compare the working voltage and the working current of the circuit to be protected, and protect the circuit to be protected only when the target working voltage is greater than the preset voltage threshold and the target working current is greater than the preset current threshold.
Furthermore, due to the fact that the protection method is achieved based on the hardware circuit, compared with a protection method achieved based on software control in the prior art, the protection method has the advantages that time consumption is short in the whole process from the time of collecting the voltage and the current of a circuit to be protected to the time of outputting a protection signal, execution efficiency is high, and the operation safety of the power conversion circuit is improved.
Based on the protection circuit shown in fig. 1, the inventors further found that, in a power conversion circuit implemented by power elements such as IGBTs, the voltage applied to the IGBT elements is related to not only the bus voltage of the power conversion circuit, but also the operating current of the power conversion circuit, and different operating currents cause the power elements to apply different peak voltages, which are superimposed on the bus of the power conversion circuit, to be the operating voltages applied to the power elements.
Specifically, referring to fig. 2, fig. 2 shows a corresponding relationship between the peak voltage and the operating current of the power element, and it can be seen from fig. 2 that the peak voltage of the power element and the operating current of the power element are positively correlated, and the larger the operating current of the power element is, the larger the corresponding peak voltage is. Specifically, in the quantization relation, the peak voltage can be calculated by the following formula:
Figure BDA0003184492500000081
wherein Δ U represents a peak voltage of the power element;
l represents an equivalent inductance of a circuit to which the power element belongs;
di represents the variation of the working current of the circuit to be protected;
dt represents the duration of the switching of the power element from the on-state to the off-state in the circuit to be protected.
Based on the above formula, it can be seen that, for a certain circuit to be protected, its own equivalent inductance is determined, and under the condition that the on-time of the power element is certain, the peak voltage corresponding to the power element is directly related to the operating current of the power element. It is further conceivable that the magnitude of the spike voltage and thus the operating voltage across the power element can be changed by controlling the on-time of the power element, which is also the basis for implementing the corresponding protection measures described in the following, and will not be described in detail here.
In practical application, the working current of the power element changes within a certain range, different working currents correspond to different peak voltages, and the sum of the peak voltage and the bus voltage is the working voltage of the power element, so that corresponding preset voltage thresholds can be determined according to different working currents of the circuit to be protected and the bus voltage, meanwhile, corresponding preset current thresholds can be determined according to the working current of the circuit to be protected, for example, a certain margin can be added on the basis of the working current, or the working current can be amplified according to a certain proportion, and the obtained result can be used as the preset current threshold. Based on the protection method, multiple groups of working currents and bus voltages are collected according to the actual operation condition of the circuit to be protected, so that corresponding multiple groups of protection thresholds can be obtained, and the circuit to be protected is subjected to a stepped protection mode.
In combination with the above, in the protection circuit provided by the embodiment of the present invention, the comparison circuit sets at least one set of threshold pairs, and any one set of threshold pairs includes a preset voltage threshold and a preset current threshold. And taking any one group of threshold value pairs in each threshold value pair as a target threshold value pair, and outputting the protection signal by the comparison circuit under the condition that the obtained target working voltage is greater than a preset voltage threshold value of the target threshold value pair and the target working current is greater than a preset current threshold value of the target threshold value pair.
As mentioned above, the operating current of the power element is positively correlated with the operating voltage that the power element is subjected to, which means that if the operating current of the power element is small, the voltage threshold can be increased to a certain extent, and conversely, if the operating current of the power element is large, the voltage threshold should be correspondingly reduced in order to avoid overvoltage breakdown of the power element, so that by setting the threshold value pair, on the basis of simultaneously realizing overvoltage protection and overcurrent protection, a stepped protection mode can be formed, and the protection range of the power element can be expanded. Optionally, referring to fig. 3, if the threshold pairs provided by the embodiments of the present invention are arranged from low to high according to the preset voltage threshold, the preset current thresholds of the threshold pairs are arranged from high to low. As can be seen from fig. 3, the present invention can also provide a protection range within a plurality of rectangular frames in the diagram, on the premise of the existing working range of the power element.
Optionally, based on the above, an embodiment of the present invention provides another protection circuit, and on the basis of the embodiment shown in fig. 1, this embodiment provides a specific structure of a comparison circuit in the protection circuit, and referring to fig. 4, in the protection circuit provided in this embodiment, a comparison circuit 30 includes at least one path of comparison sub-circuit (shown as two paths of sub-circuits in fig. 4).
As shown in the figure, the input terminal of each comparison sub-circuit is used as the input terminal of the comparison circuit, and is connected to the output terminals of the voltage acquisition circuit 10 and the current acquisition circuit 20, respectively, to receive the target working voltage fed back by the voltage acquisition circuit and the target working current fed back by the current acquisition circuit. Furthermore, the output end of each comparison sub-circuit is used as the output end of the comparison circuit to output the protection signal.
More importantly, in this embodiment, each comparison sub-circuit is provided with a threshold pair, and the threshold pairs corresponding to the comparison sub-circuits are different from each other. Therefore, with the increase of the number of the comparison sub-circuits, the multi-step protection of the circuit to be protected can be realized.
Furthermore, any one of the comparison sub-circuits specifically comprises a current comparison circuit, a voltage comparison circuit and a signal output circuit, wherein the input end of the current comparison circuit is used as the first input end of the comparison sub-circuit and is connected with the current acquisition circuit; the input end of the voltage comparison circuit is used as the second input end of the comparison sub-circuit and is connected with the voltage acquisition circuit; the output end of the current comparison circuit is connected with the first input end of the signal output circuit, and outputs a first driving signal to the signal output circuit under the condition that the obtained target working current is larger than the corresponding preset current threshold value, and correspondingly, the output end of the voltage comparison circuit is connected with the second input end of the signal output circuit, and outputs a second driving signal to the signal output circuit under the condition that the target working voltage is larger than the corresponding preset voltage threshold value.
The signal output circuit outputs the protection signal when receiving the first drive signal and the second drive signal.
Specifically, referring to fig. 5, the current comparison circuit may be implemented based on the first operational amplifier Q1. It should be noted in advance that, since the operational amplifier can only compare the voltage magnitude, when the function of the current comparison circuit is specifically implemented, the function is implemented based on the voltage comparison function, that is, the target operating current provided by the current collecting circuit should be converted into a corresponding voltage value and then input into the current comparison circuit, and the preset current threshold should also be represented by the corresponding voltage value.
In this embodiment, the negative input terminal of the first operational amplifier Q1 is used as a first input terminal to receive a first reference voltage, which is obtained by converting based on a preset current threshold corresponding to the current comparison circuit, and the positive input terminal of the first operational amplifier Q1 is used as a second input terminal as an input terminal (shown as C in the figure) of the current comparison circuit, and receives a target operating current fed back by the current collection circuit, it is conceivable that the actual voltage fed back by the current collection circuit should be a voltage corresponding to the target operating current, and then the comparison with the first reference voltage is implemented; the output terminal of the first operational amplifier Q1 is used as the output terminal of the current comparison circuit, and outputs the first driving signal when the above condition is satisfied.
In addition, the voltage comparison circuit includes a third operational amplifier Q3, as shown in fig. 5, a negative input terminal of the third operational amplifier Q3 is used as a first input terminal to receive the second reference voltage, a positive input terminal is used as a second input terminal of the third operational amplifier Q3 and is also used as an input terminal (shown as D in the figure) of the voltage comparison circuit, the voltage comparison circuit receives the target operating voltage fed back by the voltage acquisition circuit, and an output terminal of the third operational amplifier Q3 is used as an output terminal of the voltage comparison circuit, and when the aforementioned conditions are satisfied, the second driving signal is output. The voltage value of the second reference voltage is a preset voltage threshold corresponding to the voltage comparison circuit.
The signal output circuit is implemented based on an and circuit, and specifically, a first input terminal (shown as a in the figure) of the and circuit is used as a first input terminal of the signal output circuit and is connected with the current comparison circuit; a second input end (shown as B in the figure) of the AND gate circuit is used as a second input end of the signal output circuit and is connected with the output end of the voltage comparison circuit; the output terminal (shown by Y in the figure) of the and circuit serves as the output terminal of the signal output circuit, and outputs the protection signal. It is conceivable that, in the present embodiment, the protection signal is a high level output from the and circuit.
In the embodiment shown in fig. 5, the current comparison circuit can only compare direct currents in a forward direction, and in practical applications, alternating currents need to be sampled and compared in many application scenarios, and to solve this problem, the present invention further provides a comparison circuit capable of comparing alternating currents on the basis of the embodiment shown in fig. 5.
Specifically, referring to fig. 6, on the basis of the embodiment shown in fig. 5, the current comparison circuit provided in this embodiment further includes a second operational amplifier Q2. The negative input end of the first operational amplifier Q1 is used as the first input end to access the first reference voltage, and correspondingly, the positive input end of the second operational amplifier Q2 is used as the second input end to access the first reference voltage, it is conceivable that the first operational amplifier Q1 and the second operational amplifier Q2 are both used as the first reference voltage, but because the polarities of the specifically accessed input ends of the first operational amplifier Q1 and the second operational amplifier Q2 are opposite, the checking of the working current including the positive direction and the negative direction can be realized, the most typical application scenario is that the circuit to be protected is an inverter circuit, the output current of the inverter circuit is an alternating current including the positive half-cycle current and the negative half-cycle current, and the comparison of the positive half-cycle current and the negative half-cycle current can be realized simultaneously through the current comparison circuit shown in fig. 6.
Further, a connection point between the positive input terminal of the first operational amplifier Q1 and the negative input terminal of the second operational amplifier Q2 serves as an input terminal (shown as C in the figure) of the current comparison circuit, and receives the target working current fed back by the current acquisition circuit; the connection point between the output terminal of the first operational amplifier Q1 and the output terminal of the second operational amplifier Q2 serves as the output terminal of the current comparison circuit, and outputs the first drive signal when the aforementioned conditions are satisfied.
It should be noted that, when comparing the magnitude relationship between the ac current and the preset current threshold, the comparison may be implemented by other circuits, for example, by setting a bias voltage to identify the positive working current and the negative working current, which is also optional, and on the premise of not exceeding the scope of the core idea of the present invention, the comparison also belongs to the protection scope of the present invention.
As can be seen from the circuit topology shown in fig. 6, the current comparison circuit provided in this embodiment can simultaneously implement comparison of positive current and negative current, and can be applied to an ac current calibration scenario. For the specific configurations of the voltage comparison circuit and the signal output circuit in this embodiment, and the connection relationship between the respective constituent circuits, reference may be made to the embodiment shown in fig. 5, and the description thereof will not be repeated.
Optionally, on the basis of the embodiment shown in fig. 6, the signal output circuit may also adopt a structure as shown in fig. 7, and compared with the embodiment shown in fig. 6, the signal output circuit in this embodiment further includes a first pull-up circuit R1 and a second pull-up circuit R2. The first pull-up circuit R1 is connected with the first input end A of the signal output circuit, the second pull-up circuit R2 is connected with the second input end B of the signal output circuit, and meanwhile, the first pull-up circuit R1 and the second pull-up circuit R2 are also connected with the working power supply of the AND circuit at the same time, so that the signal output circuit can receive a controllable driving signal.
It is conceivable that, in the above embodiments, the negative input terminal of the operational amplifier is used as the first input terminal, and the positive input terminal is used as the second input terminal, in practical applications, the positive input terminal may also be selected as the first input terminal, and correspondingly, the negative input terminal is selected as the second input terminal, which are also optional on the premise that the above circuit functions can be implemented, and also belong to the protection scope of the present invention.
Optionally, referring to fig. 8, fig. 8 is a circuit topology diagram of a protection circuit according to an embodiment of the present invention, on the basis of the embodiment shown in fig. 6, this embodiment further provides optional configurations of a current acquisition circuit and a voltage acquisition circuit, and meanwhile, the protection circuit provided in this embodiment further includes a protection controller 50.
Specifically, the voltage acquisition circuit 10 includes a voltage acquisition sub-circuit and a first selection circuit, an input end of the voltage acquisition sub-circuit is used as an input end of the voltage acquisition circuit, and is connected to a circuit to be protected (not shown in fig. 8) to acquire a positive half bus voltage and a negative half bus voltage of the circuit to be protected, an output end of the voltage acquisition sub-circuit is connected to an input end of the first selection circuit, an output end of the first selection circuit is used as an output end of the voltage acquisition circuit, and a larger one of the positive half bus voltage and the negative half bus voltage is output to the comparison circuit 30 at the rear stage as a target working voltage.
The current collection circuit 20 includes: the current acquisition sub-circuit and the second selection circuit. The input end of the current collecting sub-circuit is used as the input end of the current collecting circuit, and is connected to a circuit to be protected (not shown in fig. 8), and collects a plurality of working currents of the circuit to be protected, for example, in the case that the circuit to be protected is an inverter circuit, the current collecting sub-circuit needs to collect three-phase alternating current output by the inverter circuit; the output end of the current collecting sub-circuit is connected with the input end of the second selection circuit, and the maximum working current in the working currents of the circuit to be protected is output to the post-stage comparison circuit 30 as the target working current through the second selection circuit.
Optionally, as described above, in the case of using the current comparison circuit implemented based on the operational amplifier shown in fig. 8, it is difficult to directly compare the magnitude of the current, and a voltage corresponding to the current needs to be converted, therefore, the current collection circuit may further include a voltage conversion circuit, the voltage conversion circuit is connected in series between the current collection sub-circuit and the second selection circuit, the voltage conversion circuit converts the plurality of working currents of the circuit to be protected collected by the current collection sub-circuit into corresponding sampling voltages, respectively, and the second selection circuit is configured to output the largest sampling voltage among the sampling voltages, so as to represent the target working current mentioned in the foregoing description.
The target operating current and the target operating voltage are output to the comparator 30 at the subsequent stage, and the comparison in magnitude is performed as described above, which will not be repeated here.
Further, the output terminal of the comparison circuit 30 is connected to the input terminal of the protection controller 50, meanwhile, the protection controller 50 is further connected to the circuit to be protected, and the protection controller 50 executes a preset protection measure after receiving the protection signal.
Optionally, in combination with an operation process of a circuit to be protected in practical application, especially in a case where the circuit to be protected is a power conversion circuit, the preset protection measure includes at least one of the following measures:
reducing the bus voltage of a circuit to be protected;
reducing the change rate of the working current of the circuit to be protected;
controlling a circuit to be protected to stop;
and controlling a controllable switching tube in the circuit to be protected to be in a conducting or switching-off state.
When the protection controller 50 reduces the change rate of the working current of the circuit to be protected, the working current of the circuit to be protected can be reduced, or the switching speed of a controllable switching tube in the circuit to be protected can be reduced.
Optionally, an embodiment of the present invention further provides a main power conversion circuit, a power conversion controller, and a protection circuit provided in any of the above embodiments, wherein,
the power conversion controller is connected with the power conversion main circuit and controls the working process of the power conversion circuit;
the protection circuit is connected with the power conversion main circuit.
Optionally, the power conversion controller comprises a protection controller in the protection circuit.
Optionally, the power conversion main circuit includes an inverter circuit, a rectifier circuit and a DC/DC circuit.
Optionally, an embodiment of the present invention further provides a three-level inverter, including a three-level inverter circuit, an inverter controller, and the protection circuit provided in any of the above embodiments, wherein,
the inversion controller is connected with the three-level inversion circuit and controls the working process of the three-level inversion circuit;
the protection circuit is connected with the three-level inverter circuit, collects the working current and the working voltage of the three-level inverter circuit and protects the three-level inverter circuit.
Alternatively, referring to fig. 9, fig. 9 is a circuit topology diagram of a three-level inverter circuit provided in an embodiment of the present invention, where the three-level inverter circuit includes a positive half-bus capacitor, a negative half-bus capacitor, and a three-phase inverter bridge arm, where,
the positive half bus capacitor and the negative half bus capacitor are connected in series to form a capacitor series branch;
each inversion bridge arm is connected in parallel to form a bridge arm parallel branch;
the positive end of the capacitor series branch is connected with the positive end of the bridge arm parallel branch, and the negative end of the capacitor series branch is connected with the negative end of the bridge arm parallel branch;
and the connection points of the positive half bus capacitor and the negative half bus capacitor are respectively connected with each inverter bridge arm.
In summary, the protection circuit and the application apparatus of the protection circuit provided in the above embodiments implement protection of a power element in a circuit to be protected based on a hardware circuit, and based on the same protection concept, the protection logic may also be implemented based on software, so as to achieve the same protection effect.
Optionally, referring to fig. 10, fig. 10 is a flowchart of a circuit protection method provided in an embodiment of the present invention, and the circuit protection method provided in the embodiment of the present invention may be applied to an electronic device, where the electronic device may be a controller included in a circuit to be protected itself, or may be independent of another controller other than the circuit to be protected, and of course, in some cases, the method may also be applied to a controller on a network side. The process of the circuit protection method provided by the embodiment includes:
s100, obtaining target working current and target working voltage of a circuit to be protected.
The target working current and the target working voltage of the circuit to be protected are obtained according to different specific circuit structures and application scenarios of the circuit to be protected. Specifically, if the working current of the circuit to be protected is an alternating current, the target working current should be a current with a larger absolute value of the positive current and the negative current, and correspondingly, if the working current is a direct current, the obtained direct current is the target working current. Further, if the bus voltage of the circuit to be protected includes a positive half bus voltage and a negative half bus voltage, the target operating voltage should be the greater of the positive half bus voltage and the negative half bus voltage.
S110, judging whether the target working voltage is larger than a preset voltage threshold and the target working current is larger than a preset current threshold, if so, executing S120.
And if the obtained target working voltage is greater than the preset voltage threshold and the target working current is greater than the preset current threshold, executing S120, and if at least one of the conditions that the obtained target working voltage is less than or equal to the preset voltage threshold or the target working current is less than or equal to the preset current threshold occurs, not executing any operation and not interfering the working process of the circuit to be protected.
Optionally, in the circuit protection method provided in the embodiment of the present invention, at least one set of threshold value pairs is set in advance, where each set of threshold value pair includes a preset voltage threshold value and a preset current threshold value, and in this case, if the target operating voltage is greater than the preset voltage threshold value of the target threshold value pair and the target operating current is greater than the preset current threshold value of the target threshold value pair, S120 may be performed. It should be noted that the target threshold pair mentioned herein is any one of the threshold pairs, that is, S120 may be executed as long as the target operating current and the target operating voltage are respectively greater than the corresponding preset current threshold and preset voltage threshold in the same threshold pair.
Further, as mentioned above, the voltage stress borne by the power element in the circuit to be protected is not only related to the bus voltage of the circuit to be protected, but also related to the working current of the circuit to be protected. Therefore, in the protection method provided by the embodiment of the present invention, under the condition that the threshold pairs are arranged from low to high according to the preset voltage threshold, the preset current thresholds of the threshold pairs are arranged from high to low.
And S120, outputting a protection signal triggering a preset protection measure.
And under the condition that the obtained target working voltage is greater than a preset voltage threshold and the target working current is greater than a preset current threshold, outputting a protection signal triggering a preset protection measure, thereby ensuring the safe operation of the circuit to be protected.
In summary, embodiments of the present invention provide a circuit protection method, which implements protection of a circuit to be protected based on software, and compared with the prior art, the protection circuit that can simultaneously perform overcurrent protection and overvoltage protection on the circuit to be protected is more comprehensive in protection, so as to effectively reduce the frequency of faults of a power conversion circuit and improve the operational reliability of the circuit.
Alternatively, any set of threshold value pairs described above may be determined in the same manner. Specifically, the working current and the half-bus voltage of the circuit to be protected are obtained first, and it is conceivable that the working current and the half-bus voltage of the circuit to be protected are inevitably changed within a certain range in actual work, so that corresponding threshold value pairs can be obtained by selecting different working currents and half-bus voltages, and multiple groups of working currents and half-bus voltages can be obtained, thus multiple groups of threshold value pairs can be obtained. The collection density of the working current and the half-bus voltage should be determined according to specific control requirements, which is not limited in the present invention.
Then, a preset voltage threshold corresponding to the working current is determined according to the working current and the half bus voltage of the circuit to be protected, a preset current threshold corresponding to the working current is determined, and after the corresponding preset current threshold and the corresponding preset voltage threshold are obtained according to the working current and the half bus voltage obtained by one-time collection, the preset current threshold and the preset voltage threshold can be used as a group of threshold value pairs.
The working current and the half-bus voltage of the circuit to be protected can be input into the following formula, and the preset voltage threshold corresponding to the working current is obtained:
Figure BDA0003184492500000161
wherein, UZRepresents a preset voltage threshold;
l represents the equivalent inductance of the circuit to be protected;
d i represents the variation of the working current of the circuit to be protected;
dt represents the time length for switching a power element in a circuit to be protected from an on state to an off state;
UBUSrepresenting the half-bus voltage of the circuit to be protected.
As for the preset current threshold, as mentioned above, a certain margin may be added on the basis of the working current, or the working current may be amplified according to a certain proportion, and the obtained result may be used as the preset current threshold.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. The device disclosed by the embodiment corresponds to the method disclosed by the embodiment, so that the description is simple, and the relevant points can be referred to the method part for description.
Those of skill would further appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both, and that the various illustrative components and steps have been described above generally in terms of their functionality in order to clearly illustrate this interchangeability of hardware and software. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.
The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in Random Access Memory (RAM), memory, Read Only Memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (26)

1. A protection circuit, comprising: a voltage acquisition circuit, a current acquisition circuit and a comparison circuit, wherein,
the voltage acquisition circuit and the current acquisition circuit are respectively connected with a circuit to be protected;
the comparison circuit is respectively connected with the voltage acquisition circuit and the current acquisition circuit;
the voltage acquisition circuit acquires a target working voltage of the circuit to be protected;
the current acquisition circuit acquires a target working current of the circuit to be protected;
and the comparison circuit outputs a protection signal for triggering a preset protection measure under the condition that the target working voltage is greater than a preset voltage threshold and the target working current is greater than a preset current threshold.
2. The protection circuit of claim 1, wherein the comparison circuit sets at least one set of threshold value pairs, and any one set of the threshold value pairs comprises a predetermined voltage threshold value and a predetermined current threshold value;
the comparison circuit outputs the protection signal when the target working voltage is greater than a preset voltage threshold value of a target threshold value pair and the target working current is greater than a preset current threshold value of the target threshold value pair;
wherein the target threshold value pair is any one of the threshold value pairs.
3. The protection circuit according to claim 2, wherein the preset voltage threshold of any one of the threshold pairs is determined based on the operating current of the circuit to be protected and the bus voltage of the circuit to be protected;
and determining the preset current threshold value of any threshold value pair based on the working current of the circuit to be protected.
4. The protection circuit of claim 2, wherein the preset current thresholds of each pair of thresholds are arranged from high to low when the pairs are arranged from low to high according to a preset voltage threshold.
5. The protection circuit of claim 2, wherein the comparison circuit comprises at least one comparison sub-circuit;
the input end of each comparison sub-circuit is used as the input end of the comparison circuit;
the output end of each comparison sub-circuit is used as the output end of the comparison circuit;
each of the comparison sub-circuits corresponds to a different threshold value pair.
6. The protection circuit of claim 5, wherein the comparison sub-circuit comprises: a current comparison circuit, a voltage comparison circuit, and a signal output circuit, wherein,
the input end of the current comparison circuit is used as the first input end of the comparison sub-circuit;
the input end of the voltage comparison circuit is used as a second input end of the comparison sub-circuit;
the output end of the current comparison circuit is connected with the first input end of the signal output circuit;
the output end of the voltage comparison circuit is connected with the second input end of the signal output circuit;
the current comparison circuit outputs a first driving signal under the condition that the target working current is greater than a corresponding preset current threshold value;
the voltage comparison circuit outputs a second driving signal under the condition that the target working voltage is greater than a corresponding preset voltage threshold;
the signal output circuit outputs the protection signal when receiving the first drive signal and the second drive signal.
7. The protection circuit of claim 6, wherein the current comparison circuit comprises a first operational amplifier, wherein,
a first input end of the first operational amplifier is connected with a first reference voltage, and the first reference voltage is obtained by converting based on a preset current threshold corresponding to the current comparison circuit;
a second input end of the first operational amplifier is used as an input end of the current comparison circuit;
and the output end of the first operational amplifier is used as the output end of the current comparison circuit.
8. The protection circuit of claim 7, wherein the current comparison circuit further comprises a second operational amplifier, wherein,
a second input end of the second operational amplifier is connected to the first reference voltage;
a connection point of a first input end of the second operational amplifier and a second input end of the first operational amplifier is used as an input end of the current comparison circuit;
a connection point of an output end of the first operational amplifier and an output end of the second operational amplifier is used as an output end of the current comparison circuit;
wherein the first input terminal of the second operational amplifier is of the same polarity as the first input terminal of the first operational amplifier.
9. The protection circuit of claim 6, wherein the voltage comparison circuit comprises a third operational amplifier, wherein,
a first input end of the third operational amplifier is connected with a second reference voltage, and the voltage value of the second reference voltage is a preset voltage threshold value corresponding to the voltage comparison circuit;
a second input end of the third operational amplifier is used as an input end of the voltage comparison circuit;
and the output end of the third operational amplifier is used as the output end of the voltage comparison circuit.
10. The protection circuit of claim 6, wherein the signal output circuit comprises an AND gate circuit, wherein,
a first input end of the AND gate circuit is used as a first input end of the signal output circuit;
a second input end of the AND gate circuit is used as a second input end of the signal output circuit;
and the output end of the AND gate circuit is used as the output end of the signal output circuit.
11. The protection circuit of claim 10, wherein the signal output circuit further comprises: a first pull-up circuit and a second pull-up circuit, wherein,
the first pull-up circuit is connected with a first input end of the signal output circuit;
the second pull-up circuit is connected to a second input terminal of the signal output circuit.
12. The protection circuit of claim 1, wherein the voltage acquisition circuit comprises: a voltage acquisition sub-circuit and a first selection circuit, wherein,
the input end of the voltage acquisition sub-circuit is used as the input end of the voltage acquisition circuit;
the output end of the voltage acquisition sub-circuit is connected with the input end of the first selection circuit;
the output end of the first selection circuit is used as the output end of the voltage acquisition circuit;
the voltage acquisition sub-circuit acquires positive half bus voltage and negative half bus voltage of the circuit to be protected;
the first selection circuit outputs a larger bus voltage of the positive half bus voltage and the negative half bus voltage as the target operating voltage.
13. The protection circuit of claim 1, wherein the current acquisition circuit comprises: a current collection sub-circuit and a second selection circuit, wherein,
the input end of the current acquisition sub-circuit is used as the input end of the current acquisition circuit;
the output end of the current acquisition sub-circuit is connected with the input end of the second selection circuit;
the output end of the second selection circuit is used as the output end of the current acquisition circuit;
the current acquisition sub-circuit acquires a plurality of working currents of the circuit to be protected;
the second selection circuit outputs the largest working current of the working currents as the target working current.
14. The protection circuit of claim 13, wherein the current acquisition circuit further comprises: a voltage conversion circuit, wherein,
the voltage conversion circuit is connected in series between the current acquisition sub-circuit and the second selection circuit;
the voltage conversion circuit converts the plurality of working currents of the circuit to be protected, which are acquired by the current acquisition sub-circuit, into corresponding sampling voltages respectively;
the second selection circuit is used for outputting the largest sampling voltage in the sampling voltages so as to represent the target working current.
15. The protection circuit according to any one of claims 1 to 14, further comprising: the protection controller is configured to, among other things,
the protection controller is respectively connected with the output end of the comparison circuit and the circuit to be protected;
and the protection controller receives the protection signal and executes the preset protection measures.
16. The protection circuit of claim 15, wherein the predetermined protection measure comprises at least one of:
reducing the bus voltage of the circuit to be protected;
reducing the change rate of the working current of the circuit to be protected;
controlling the circuit to be protected to stop operating;
and controlling a controllable switching tube in the circuit to be protected to be in a conducting or switching-off state.
17. The protection circuit of claim 16, wherein the process of the protection controller reducing the rate of change of the operating current of the circuit to be protected comprises:
and reducing the working current of the circuit to be protected, or reducing the switching-on speed of a controllable switch tube in the circuit to be protected.
18. A power converter, comprising: a power conversion main circuit, a power conversion controller, and a protection circuit according to any one of claims 1 to 17,
the power conversion controller is connected with the power conversion main circuit and controls the working process of the power conversion circuit;
the protection circuit is connected with the power conversion main circuit.
19. The power converter of claim 18, wherein the power conversion controller comprises a protection controller in the protection circuit.
20. The power conversion circuit of claim 18, wherein the power conversion main circuit comprises an inverter circuit, a rectifier circuit and a DC/DC circuit.
21. A three-level inverter, comprising: a three-level inverter circuit, an inverter controller, and the protection circuit of any one of claims 1 to 17,
the three-level inverter circuit comprises a positive half bus capacitor, a negative half bus capacitor and a three-phase inverter bridge arm, wherein,
the positive half bus capacitor and the negative half bus capacitor are connected in series to form a capacitor series branch;
all the inverter bridge arms are connected in parallel to form bridge arm parallel branches;
the positive end of the capacitor series branch is connected with the positive end of the bridge arm parallel branch, and the negative end of the capacitor series branch is connected with the negative end of the bridge arm parallel branch;
the connection point of the positive half bus capacitor and the negative half bus capacitor is respectively connected with each inverter bridge arm;
the inverter controller is connected with the three-level inverter circuit and controls the working process of the three-level inverter circuit;
and the protection circuit is connected with the three-level inverter circuit.
22. A circuit protection method, comprising:
acquiring a target working current and a target working voltage of a circuit to be protected;
and if the target working voltage is greater than a preset voltage threshold value and the target working current is greater than a preset current threshold value, outputting a protection signal for triggering a preset protection measure.
23. The circuit protection method of claim 22, wherein at least one set of threshold value pairs is preset, and any one set of threshold value pairs comprises a preset voltage threshold value and a preset current threshold value;
if the target working voltage is greater than a preset voltage threshold and the target working current is greater than a preset current threshold, outputting a protection signal triggering a preset protection measure, including:
if the target working voltage is greater than a preset voltage threshold value of a target threshold value pair, and the target working current is greater than a preset current threshold value of the target threshold value pair, outputting a protection signal for triggering a preset protection measure;
wherein the target threshold value pair is any one of the threshold value pairs.
24. The circuit protection method of claim 23, wherein the preset current thresholds of each of the threshold pairs are arranged from high to low when the threshold pairs are arranged from low to high according to the preset voltage threshold.
25. The circuit protection method of claim 23, wherein the process of generating any one of the threshold value pairs comprises:
acquiring the working current and half bus voltage of the circuit to be protected;
determining a preset voltage threshold corresponding to the working current according to the working current of the circuit to be protected and the half bus voltage;
determining a preset current threshold corresponding to the working current;
and taking the preset current threshold value and the preset voltage threshold value as a group of threshold value pairs.
26. The circuit protection method according to claim 25, wherein the determining a preset voltage threshold corresponding to the working current according to the working current and the half-bus voltage of the circuit to be protected comprises:
inputting the working current and the half-bus voltage of the circuit to be protected into the following formula to obtain a preset voltage threshold corresponding to the working current:
Figure FDA0003184492490000061
wherein, UZRepresents a preset voltage threshold;
l represents the equivalent inductance of the circuit to be protected;
di represents the variation of the working current of the circuit to be protected;
dt represents the time length of switching the power element in the circuit to be protected from the on state to the off state;
UBUSrepresenting the half-bus voltage of the circuit to be protected.
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CN107147094A (en) * 2017-04-27 2017-09-08 华为技术有限公司 Current-limiting protection circuit and guard method
CN109524941A (en) * 2018-12-29 2019-03-26 北京汇能精电科技股份有限公司 Phase current foldback circuit and photovoltaic controller
CN110416974A (en) * 2019-08-15 2019-11-05 阳光电源股份有限公司 A kind of protective circuit of switch power source, Switching Power Supply and Switching Power Supply guard method

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