CN102739090B - Overcurrent protection device and method for inverter as well as inverter - Google Patents
Overcurrent protection device and method for inverter as well as inverter Download PDFInfo
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- CN102739090B CN102739090B CN201210225326.5A CN201210225326A CN102739090B CN 102739090 B CN102739090 B CN 102739090B CN 201210225326 A CN201210225326 A CN 201210225326A CN 102739090 B CN102739090 B CN 102739090B
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Abstract
The embodiment of the invention provides an overcurrent protection device and method for an inverter as well as the inverter, which relate to the electrical and electronic field. The overcurrent protection device and method as well as the inverter are invented for efficiently improving overcurrent protection for the inverter at lower cost. The inverter comprises a power alternating circuit, a filtering circuit and the overcurrent protection device, and a change on output voltage of the filtering circuit exceeds the change on inductance current of the filtering circuit; and the overcurrent protection device comprises the following of: a voltage sampling unit which is used for sampling output voltage of the filtering circuit; a voltage comparison unit which is used for comparing the sampling output voltage sampled by the voltage sampling unit with preset voltage; and a current-limiting unit which is used for limiting current for the power alternating circuit when output voltage of the filtering circuit is reversed with theoretical output voltage and an absolute value of output voltage of the filtering circuit is larger than that of preset voltage. The overcurrent protection device and method for inverter as well as the inverter can be applied in a contravariant power supply.
Description
Technical field
The present invention relates to electric and electronic technical field, relate in particular to a kind of overcurrent protective device of inverter and method, inverter.
Background technology
Inverter is a kind of device that direct current is converted into alternating current, general using PWM (Pulse Width Modulation, pulse width modulation) being switched on or switched off of principle control semiconductor power switch, and then control being switched on or switched off of output circuit and DC circuit, then make described output circuit after filtering circuit filtering can obtain the alternating current of preset frequency.
Wherein, filter circuit can be made up of filter capacitor and filter inductance conventionally, load, particularly pure capacitive load oppositely fall seriously output voltage in the moment of access inverter circuit, thereby make circuit produce larger surge current, within the short time (as several delicate), inductive current rising hundreds of ampere, therefore causes semiconductor power switch pipe usually because overcurrent damages.
In prior art, can sample to inductive current, compare with corresponding reference current value by sampled value, in the time that inductive current sampled value is greater than reference current value, just closes semiconductor power switch pipe according to certain sequential, thereby avoid semiconductor power switch pipe to be burned because of overcurrent.But, in said process, because current sample and current ratio expend the regular hour compared with action need, cause from inductive current sampled value be greater than reference current value time be carved into and between the moment that power switch pipe successfully closes, have larger time delay, like this, before power switch pipe is closed, actual inductive current will, much larger than reference current value, still may cause the damage of power switch pipe.Therefore, the over-flow protecting effect to inverter in prior art is unsatisfactory, and reliability is not high.
Summary of the invention
The embodiment of the present invention provides a kind of overcurrent protective device of inverter and method, inverter, can realize better the overcurrent protection to inverter, reduces the risk that inverter damages because of overcurrent.
For reaching above-mentioned purpose, on the one hand, the embodiment of the present invention provides a kind of inverter, comprise the power conversion circuit for direct current being converted into alternating current, also comprise filter circuit and overcurrent protective device, described filter circuit is connected with described power conversion circuit, and described overcurrent protective device is connected with described filter circuit with described power conversion circuit respectively; Described filter circuit comprises filter capacitor and filter inductance, and for the alternating current of described power conversion circuit output is carried out to low-pass filtering, the variation of the output voltage of described filter circuit is ahead of the variation of the inductive current of described filter circuit;
Described overcurrent protective device comprises: voltage sample unit, for the output voltage of the described filter circuit of sampling; Voltage comparison unit, for comparing the output voltage of described voltage sample unit sampling with predefined voltage; Current limliting unit, reverse for working as the output voltage of described filter circuit and the theoretical output voltage of described filter circuit, and when the absolute value that described voltage comparison unit is determined the output voltage of described filter circuit is greater than the absolute value of described predefined voltage, described power conversion circuit is carried out to current limliting.
On the other hand, the embodiment of the present invention provides a kind of overcurrent protective device of inverter, comprise: voltage sample unit, for the output voltage of filter circuit of the described inverter of sampling, wherein, described filter circuit comprises filter capacitor and filter inductance, alternating current for the power conversion circuit output to described inverter carries out low-pass filtering, described power conversion circuit is for being converted into alternating current by direct current, and the variation of the output voltage of described filter circuit is ahead of the variation of the inductive current of described filter circuit; Voltage comparison unit, for comparing the output voltage of described voltage sample unit sampling with predefined voltage; Current limliting unit, for when the output voltage of described filter circuit and when the theoretical output voltage of described filter circuit is reverse and the absolute value of the output voltage of described filter circuit is greater than the absolute value of described predefined voltage, described power conversion circuit is carried out to current limliting.
On the other hand, the embodiment of the present invention also provides a kind of over-current protection method of inverter, comprise: the output voltage of the filter circuit of the described inverter of sampling, described filter circuit carries out low-pass filtering for the alternating current of the power conversion circuit output to described inverter, described power conversion circuit is for being converted into alternating current by direct current, and the variation of the output voltage of described filter circuit is ahead of the variation of the inductive current of described filter circuit; The output voltage of the described filter circuit of sampling is compared with predefined voltage; When the output voltage of described filter circuit and when the theoretical output voltage of described filter circuit is reverse and the absolute value of the output voltage of described filter circuit is greater than the absolute value of described predefined voltage, described power conversion circuit is carried out to current limliting.
Adopt after technique scheme; the overcurrent protective device of the inverter that the embodiment of the present invention provides and method, inverter; can the sample output voltage of filter circuit of described inverter; reverse at output voltage and the theoretical output voltage of filter circuit of determining described inverter; and when the absolute value of the output voltage of described filter circuit is greater than the absolute value of predefined voltage, described power conversion circuit is carried out to current limliting.Like this; because the variation of the output voltage of described filter circuit is ahead of the variation of inductive current; that is to say; if the output voltage of described filter circuit experiences larger variation within a period of time; can conclude after during this period of time; inductive current also can experience larger variation, makes its absolute value exceed the absolute value of overcurrent protection reference current.Like this, compare by the sampling of the output voltage to described filter circuit and with predefined voltage, can know in advance whether the absolute value of described inductive current over time can be greater than the absolute value of overcurrent protection reference current, and in advance described power conversion circuit is carried out to current limliting, compensate described power conversion circuit has been carried out in current limliting operation because the current limliting that hardware time delay and software delay cause operates the hysteresis coming into force, thereby be greater than the absolute value of overcurrent protection reference current at the absolute value of inductive current before, current limliting operation to described power conversion circuit comes into force in time, under the condition of not changing circuit element, improve at lower cost the overcurrent protection to inverter, reduce the risk that inverter damages because of overcurrent.
Accompanying drawing explanation
In order to be illustrated more clearly in the embodiment of the present invention or technical scheme of the prior art, to the accompanying drawing of required use in embodiment or description of the Prior Art be briefly described below, apparently, accompanying drawing in the following describes is only some embodiments of the present invention, for those of ordinary skills, do not paying under the prerequisite of creative work, can also obtain according to these accompanying drawings other accompanying drawing.
A kind of structural representation of the inverter that Fig. 1 provides for the embodiment of the present invention;
A kind of fundamental diagram of the overcurrent protection of the inverter that Fig. 2 provides for the embodiment of the present invention;
The another kind of structural representation of the inverter that Fig. 3 provides for the embodiment of the present invention;
Fig. 4 is a kind of local circuit structural representation of the inverter shown in Fig. 1 or Fig. 3;
Fig. 5 is the schematic diagram of output voltage waveforms and the inductive current waveform when with pure capacitive load of the inverter shown in Fig. 4;
A kind of flow chart of the over-current protection method for inverter that Fig. 6 provides for the embodiment of the present invention.
Embodiment
Below in conjunction with the accompanying drawing in the embodiment of the present invention, the technical scheme in the embodiment of the present invention is clearly and completely described, obviously, described embodiment is only the present invention's part embodiment, rather than whole embodiment.Based on the embodiment in the present invention, those of ordinary skills, not making the every other embodiment obtaining under creative work prerequisite, belong to the scope of protection of the invention.
As shown in Figure 1; embodiments of the invention provide a kind of inverter 1; comprise the power conversion circuit 2 for direct current being converted into alternating current; also comprise filter circuit 3 and overcurrent protective device 4; filter circuit 3 is connected with power conversion circuit 2; overcurrent protective device 4 is connected with filter circuit 3 with power conversion circuit 2 respectively, and the output of filter circuit 3 is connected with load 5.
Overcurrent protective device 4 comprises:
Wherein, theoretical output voltage is to be the theoretical value of the output voltage of confirmable filter circuit 3 according to component parameter and input electrical signal in filter circuit 3.In normal operation, the output voltage of filter circuit 3 equals its theoretical output voltage, but in the time that 3 moments of filter circuit are accessed pure capacitive load, and output voltage tends to produce and falls, and does not cause described output voltage output voltage theoretical with it not etc.
Adopt after technique scheme, the inverter 1 that the embodiment of the present invention provides, can the sample output voltage of filter circuit 3 of inverter 1, reverse at the output voltage output voltage theoretical with it of filter circuit 3 of determining inverter 1, and when the absolute value of the output voltage of filter circuit 3 is greater than the absolute value of predefined voltage, power conversion circuit 2 is carried out to current limliting.Like this; because the variation of the output voltage of filter circuit 3 is ahead of the variation of inductive current; that is to say; if the output voltage of filter circuit 3 experiences larger variation within a period of time; can conclude after during this period of time; inductive current also can experience larger variation, makes its absolute value exceed the absolute value of overcurrent protection reference current.
Like this, compare by the sampling of the output voltage to described filter circuit and with predefined voltage, can know in advance whether the absolute value of described inductive current over time can be greater than the absolute value of overcurrent protection reference current, and in advance described power conversion circuit is carried out to current limliting, compensate described power conversion circuit has been carried out in current limliting operation because the current limliting that hardware time delay and software delay cause operates the hysteresis coming into force, thereby be greater than the absolute value of overcurrent protection reference current at the absolute value of inductive current before, current limliting operation to described power conversion circuit comes into force in time, under the condition of not changing circuit element, effectively improve at lower cost the overcurrent protection to inverter, reduce the risk that inverter damages because of overcurrent.
Concrete, voltage sample unit 41 can have for any circuit structure or chip of voltage sample function, voltage comparison unit 42 is connected with voltage sample unit 41, can there is for voltage comparator or other software or the hardware circuit of voltage comparing function, compare with the 0 voltage plus or minus of the direction of determining described output voltage of the output voltage of the filter circuit 3 that can obtain by being sampled in voltage sample unit 41.Current limliting unit 43, can, for having the controller etc. of certain software filtering function and/or logic analysis function, so that the result that voltage comparison unit 42 is exported is carried out interference filtering and logic analysis, thereby carry out current limliting operation to power conversion circuit 2.
It should be noted that, in the present embodiment, in advance power conversion circuit 2 is carried out to current limliting, refer to the output voltage of filter circuit 3 and described theoretical output voltage oppositely and after the absolute value of the output voltage of filter circuit 3 is greater than the absolute value of predefined voltage, before the absolute value of inductive current exceedes the absolute value of overcurrent protection reference current, current limliting unit 43 just starts to carry out software filtering and/or logic analysis, in the time that the current limliting operation to power conversion circuit 2 comes into force, the absolute value of inductive current just equals the absolute value of overcurrent protection reference current like this, thereby in time power conversion circuit 2 is carried out to current limliting operation, effectively improve the over-flow protecting effect of inverter 1.
Although it is pointed out that above-described embodiment only described by the sampling of the output voltage to filter circuit 3 and relatively come power conversion circuit 2 to carry out current limliting operation, the invention is not restricted to this.In other embodiments of the invention, can also, by output voltage being sampled, comparing and the mode of inductive current being sampled, relatively combining, carry out current limliting to power conversion circuit 2.For example; as shown in Figure 2; in one embodiment of the invention; when the output voltage of filter circuit 3 and theoretical output voltage are oppositely and when the absolute value of the output voltage of filter circuit 3 exceedes the absolute value of predefined voltage; or in the time that the absolute value of inductive current exceedes the absolute value of overcurrent protection reference current, the current limliting operation to power conversion circuit 2 is all carried out in current limliting unit 43.Like this; inductive current and output voltage by while detection filter circuit 3 carry out current limliting operation to power conversion circuit 2; even if wherein a kind of detection method breaks down; also can carry out current limliting to power conversion circuit 2 according to another kind of detection method, effectively improve the reliability of the overcurrent protection of inverter 1.
It should be noted that, about the absolute value that whether is greater than predefined electric current according to the absolute value of inductive current, power conversion circuit 2 being carried out to the content of current limliting can be referring to the description of background technology, the not emphasis of the embodiment of the present invention, no matter omit in description therefore later.
Further, as shown in Figure 3, in previous embodiment, the overcurrent protective device 4 of inverter 1 also comprises removes unit 44 and current sample and comparing unit 45.Wherein, current sample and comparing unit 45 can be for the inductive current of filter circuit 3 is sampled, and the absolute value of described inductive current is compared with the absolute value of predefined electric current; Removing unit 44 can be for when power conversion circuit 2 is during by current limliting, if the output voltage of filter circuit 3 and described theoretical output voltage are in the same way, and the comparative result of current sample and comparing unit 45 is the absolute value that the absolute value of the inductive current of filter circuit 3 is less than predefined electric current, remove the current limliting to power conversion circuit 2.Wherein, the absolute value of described predefined electric current can equal the absolute value of described overcurrent protection reference current, also can be less than the absolute value of described overcurrent protection reference current.
Concrete, the diode neutral point clamp type tri-level inversion circuit shown in Fig. 4 is a concrete example of the power conversion circuit 2 shown in Fig. 1 and filter circuit 3.Below in conjunction with Fig. 1 and Fig. 4, specifically to introduce overcurrent protective device 4 are output voltages of how sampling filter circuit 3 and utilize the output voltage sampling to carry out current limliting to power conversion circuit 2.Certainly, in other embodiments of the invention, the concrete structure of power conversion circuit 2 and filter circuit 3 can also be other, and embodiments of the invention are not construed as limiting this.
As shown in Figure 4, power conversion circuit 2 comprises four power switch pipe Q1-Q4, and the grid of inputting Q1-Q4 by pwm control signal carrys out the opening and closing of power ratio control switching tube Q1-Q4, can be so that the output voltage U of power conversion circuit 2
bbe respectively positive direct-current busbar voltage U
inor negative DC bus-bar voltage-U
inor zero potential.Wherein, D1-D4 is the diode colonizing in Q1-Q4, and D5 and D6 are clamping diode, and capacitor C 1, C2 can be by the AC ripple component filtering in the positive and negative DC bus-bar voltage of the direct-flow input end of power conversion circuit 2.Filter circuit 3 comprises filter capacitor 31 and filter inductance 32, wherein, one end of filter inductance 32 is connected with the output of the power switch pipe of power conversion circuit 2, the other end is connected with filter capacitor 31, and filter capacitor 31 one end are connected with filter inductance 32, the other end connect to neutral (N line).And one end being connected with filter inductance 32 of filter capacitor 31 is connected with load 5.In the present embodiment, filter circuit 3 is low-pass filter circuit.
Concrete, power conversion circuit 2 can be converted into alternating current by direct current, can further described alternating current be converted into theoretical output voltage after filtering after the low-pass filtering of circuit 3.Herein, described theoretical output voltage refers to the voltage of the alternating current of filter circuit 3 expection amplitude-frequency characteristic output, that have regulation and phase-frequency characteristic.Optionally, the amplitude-frequency characteristic of this theory output voltage and phase-frequency characteristic can be specified by the instruction being recorded in inverter 1, and can be by the modification realization theory output voltage amplitude-frequency characteristic to instruction and the setting of phase-frequency characteristic.In the present embodiment, can carry out suitable selection according to the parameter of the opening and closing of instruction power ratio control switching tube Q1-Q4 and the filtering device to filter circuit 3, obtain having the theoretical output voltage of regulation amplitude-frequency characteristic and phase-frequency characteristic.Concrete, in the present embodiment, in the positive half period of theoretical output voltage, can control that Q2 opens, Q4 closes, Q1 and Q3 make U according to the complementary conducting of the control of PWM
bfor positive direct-current busbar voltage U
inor zero potential, wherein at the alternating phases of complementary conducting, guarantee that power switch pipe exists dead band, and in the negative half-cycle of alternating current, can control that Q3 opens, Q1 closes, Q4 and Q2, according to the complementary conducting of the control of PWM, make U
bfor negative DC bus-bar voltage-U
inor zero potential.Equally, at the alternating phases of complementary conducting, guarantee that power switch pipe exists dead band.
Generally, the alternating current of filter circuit 3 actual outputs is total identical with theoretical output voltage, but when the load 5 of filter circuit 3 is pure capacitive load, in the time of pure capacitive load access inverter, the output voltage of filter circuit 3 reality falls being subject to load 5 to affect the voltage that generation is larger, now, the output voltage of filter circuit 3 reality produces larger difference with theoretical output voltage, even reverse with theoretical output voltage.
When the output voltage of filter circuit 3 reality and theoretical output voltage are when reverse, the overcurrent protective device 4 of the inverter 1 of the present embodiment, by the voltage at 41 sampling filter electric capacity 31 two ends, voltage sample unit, i.e. sampling and outputting voltage U
c, and pass through voltage comparison unit 42 by the output voltage U of filter circuit 3
ccompare with predefined voltage, judge output voltage U
cdirection, when the output voltage U of filter circuit 3
creverse with theoretical output voltage, and the output voltage U of sampling
cabsolute value while being greater than the absolute value of predefined voltage; the variation that is ahead of the inductive current of filter circuit 3 according to the variation of the output voltage of filter circuit 3 can be informed in after certain hour in advance; the absolute value of the inductive current of filter circuit 3 will be greater than the absolute value of overcurrent protection reference current, thereby in advance power conversion circuit 2 is carried out to current limliting.Make a concrete analysis of as follows.
As shown in Figure 4, the voltage at filter inductance 32 two ends is the output voltage U of power conversion circuit 2
bvoltage U with filter capacitor 31 two ends
cpoor, that is:
U
L＝U
B-U
C (1)
From circuit basic principle, flow through the current i of filter inductance 32
lvoltage U with filter inductance 32 two ends
lthere is integral relation:
i
L＝1/L·∫U
Ldt (2)
(1) substitution (2) is obtained
i
L＝1/L·∫(U
B-U
C)dt (3)
In the present embodiment, U
bcan equal positive direct-current busbar voltage U
inor negative DC bus-bar voltage-U
inor 0.In the transient response of connecting in filter circuit 3 and load 5, load 5 is in parallel with filter capacitor 31, if load 5 is pure capacitive loads, and due to the impact of stray inductance, load capacitance on loaded line, the output voltage U of filter circuit 3
cto there is the process of a vibration, thereby make output voltage U
cproduce larger variation.Especially, when in this voltage oscillation process, when the actual output voltage of filter circuit 3 is reverse with the theoretical output voltage that is converted into of expection, (U
b-U
c) absolute value also can be greater than certain value, according to (3) formula, indicating that, through after a period of time, the absolute value of the output current of filter circuit 3 may be greater than the absolute value of overcurrent protection reference current.For example, in one embodiment of the invention, in the positive half period of theoretical output voltage, U
cshould be for just, and U
bmay be positive direct-current busbar voltage or zero, if now due to the impact of circuit oscillation make the output voltage of filter circuit 3 reality and theoretical output voltage reverse, i.e. U
cfor negative, (U
b-U
c) absolute value also can be greater than certain value, according to (3) formula, integration postpone after, may make inductive current i
lexcessive, thus power switch pipe may be damaged because of overcurrent.That is to say, in the oscillatory process of transient response, when output voltage U c and theoretical output voltage reverse, and output voltage U
cabsolute value while increasing to the absolute value that exceedes predefined voltage, can predict through inductive current i after a period of time
labsolute value will exceed the absolute value of overcurrent protection reference current.Consider from detecting that flowing to coming into force of the metering function to power conversion circuit 2 also needs certain hardware time delay and/or software delay, can carry out current limliting to power conversion circuit 2 in advance.Like this; when voltage comparison unit 42 determines that the output voltage of filter circuit 3 reality and theoretical output voltage are when reverse; if current limliting unit 43 determines that the absolute value of the output voltage of filter circuit 3 reality is greater than predefined magnitude of voltage; power conversion circuit 2 is carried out to current limliting; can make this metering function come into force exceed the absolute value of overcurrent protection reference current at the absolute value of inductive current before, thereby effectively improve the overcurrent protection to inverter 1.
The overcurrent protection of the overcurrent protective device 4 of inverter 1 can illustrate intuitively by one group of current-voltage relation curve.When positive half period that to Figure 5 shows that at the output voltage of filter circuit 3 be theoretical output voltage, pure capacitive load 5 accessed in the blink after filter circuit 3, the voltage in circuit, curent change curve.Wherein, the initial voltage of pure capacitive load 5 is for negative, and in the section time, the theoretical output voltage polarity of filter circuit 3 is contrary therewith.As shown in Figure 5, the voltage U that outputs to filter circuit 3 under PWM controls of the power switch pipe Q1/Q2 that curve (a) is power conversion circuit 2
b, under normal condition, the high level of curve (a) is positive direct-current bus+BUS voltage U
in, low level is 0; Under limited current state, the high level of curve (a) is positive direct-current bus+BUS voltage U
in, low level is according to the sequential difference of the opening and closing of power switch pipe Q1-Q4, can be 0 or negative DC bus-bar voltage-U
in; Curve (b) is the voltage U at filter capacitor 31 two ends in the time phase corresponding with curve (a)
csituation over time; Curve (c) is in the time phase corresponding with curve (a), (b), flows through the current i of filter inductance 32
lsituation over time.Wherein, t
0represent that load 5 accesses the moment of filter circuit 3, t
0～t
3represent that load 5 accesses a current limliting process in the transient process after filter circuit 3, its time can be for example approximately 100 microseconds.
Below in conjunction with Fig. 1, Fig. 4 and Fig. 5, the operation principle of the inverter 1 that the present embodiment is provided is described in detail.It should be noted that, although the present embodiment only the situation take the output voltage of filter circuit 3 as the positive half period of alternating voltage as example describes, the invention is not restricted to this, the situation of the negative half period that output voltage is alternating voltage is similar to its principle.
Concrete, in the time of positive half period that the output voltage of filter circuit 3 is alternating voltage, Q1 is in opening, the output end voltage U of power switch pipe
bequal positive direct-current busbar voltage U
in.When filter circuit 3 is not yet connected with load 5, output voltage U
cfor U
c0, load 5 accesses the t after filter circuit 3
0-t
2in time, because load 5 is pure capacitive loads, and the output voltage U at the polarity of the initial voltage at load 5 two ends and filter capacitor 31 two ends
con the contrary, therefore, the output voltage U of filter capacitor 31
csharply fall.
In this stage, output voltage U
cbe always negative and constantly reducing, due to the output voltage U of power conversion circuit 2 now
bfor just, therefore, (U
b-U
c) for just and be far longer than U
b.From (3) formula, output current i in the case
lmay be excessive, even exceed overcurrent protection reference current.
Due to the output voltage U of filter circuit 3
cwith inductive current i
lthere is as the expressed integral relation of (3) formula inductive current i
lby (U
b-U
c) through integration after a while, inductive current i
lvariation with respect to output voltage U
cvariation there is certain time delay, i.e. output voltage U
cvariation be ahead of output current i
lvariation.Therefore, in the present embodiment, sampling and outputting voltage U
ccan know in advance inductive current i
lvariation tendency, thereby in advance power conversion circuit 2 is carried out to current limliting.For example, as shown in Figure 5, output voltage U
cat t
0moment starts sharply to decline, corresponding, output current i
lat t
2* the moment starts just sharply to rise.Wherein, output voltage U
cwith output current i
lvariation tendency be due to U in (3) formula on the contrary
cdue to front negative sign.If at t
0moment carries out current limliting to power conversion circuit 2, may make metering function at t
2* the moment is to t
3between moment, come into force, effectively avoided the delay of current limliting operation, thereby effectively improved the over-flow protecting effect of inverter 1.
Further, time and the inductive current i of hardware delay and/or software delays in known current limliting operation
lthe condition of overcurrent protection reference current under, can, according to according to (3) formula, calculate described predefined voltage.So that come into force after necessary software delay and/or hardware time delay through metering function, metering function just can be at inductive current i
lwhile exceeding overcurrent reference current, come into force.
Certainly,, in order to make overcurrent protection there is larger surplus, also predefined voltage can be set for and made metering function at output current i
lbefore reaching overcurrent reference current, just come into force, as long as can avoid inductive current i
lgeneration overcurrent, the present invention does not limit this.
For example, in one embodiment of the invention, described predefined voltage is the negative DC bus-bar voltage-U of power conversion circuit 2
in, corresponding to t
2moment starts power conversion circuit 2 to carry out current limliting operation.Current limliting unit 43, specifically for the theoretical output voltage when filter circuit 3 expection output for just, the output voltage U of filter circuit 3 reality
cfor negative, and U
cabsolute value be less than U
intime, power conversion circuit 2 is carried out to current limliting.Be t
2moment starts power conversion circuit 2 to carry out current limliting operation after corresponding hardware delay and software delays, and overcurrent protective device 4 will be at t
2* to t
3between a certain moment, make the metering function of power conversion circuit 2 come into force.
Again for example, in another embodiment of the present invention, described predefined voltage can be also 0 current potential, corresponding to t
1moment starts power conversion circuit 2 to carry out current limliting operation.Current limliting unit 43, specifically for the theoretical output voltage when filter circuit 3 expection output for just, and the output voltage U of filter circuit 3
cwhile being less than 0 current potential, power conversion circuit 2 is carried out to current limliting.At t
1moment starts power conversion circuit 2 to carry out current limliting operation, and, after corresponding hardware delay and software delays, overcurrent protective device 4 will be at t
2* to t
3between a certain moment, make the metering function of power conversion circuit 2 come into force.
No matter at t
1moment is still at t
2moment starts power conversion circuit 2 to carry out current limliting operation, as long as guarantee output current i
lat t
3moment is no more than overcurrent protection reference current I
ref1, the present invention does not limit this.Wherein, as shown in Figure 5, the dotted line of arrow indication has not represented and in advance power conversion circuit 2 has not been carried out, in the situation of current limliting operation, flowing through the current i of inductance L
l.Visible, because the coming into force of current limliting operation to power conversion circuit 2 exists delay, if at t
3moment starts power conversion circuit 2 to carry out current limliting, and this metering function will be at inductive current i
lsubstantially exceed overcurrent protection reference current I
ref1in time, just comes into force, and therefore can not realize in time overcurrent protection.
In another embodiment of the present invention, in conjunction with Fig. 3, Fig. 4 and Fig. 5, the current limliting process of inverter 1 is identical with previous embodiment, repeats no more herein.When power conversion circuit 2 is when by the state of overcurrent protective device 4 current limlitings, if remove unit 44 also for the theoretical output voltage of filter circuit 3 in positive half period, the output voltage U of filter circuit 3
cfor just, and the absolute value that flows through the electric current of filter inductance 32 is less than the absolute value I of predefined electric current
ref2, remove the current limliting to power conversion circuit 2.In the present embodiment, the absolute value I of described predefined electric current
ref2be less than the absolute value I of described overcurrent protection reference current
ref1, to guarantee that removing unit 44 removes after the current limliting of power conversion circuit 2, the absolute value of inductive current is no more than the absolute value of described overcurrent protection reference current.But the absolute value I of predefined electric current in other embodiments of the invention,
ref2also can equal the absolute value I of overcurrent protection reference current
ref1, the embodiment of the present invention is not construed as limiting this.
It should be noted that; the theoretical output voltage of above-described embodiment Main Analysis filter circuit 3 is in positive half period; and when the output voltage of filter circuit 3 reality is negative; the operation principle of the overcurrent protective device 4 of inverter 1; but the invention is not restricted to this; situation for theoretical output voltage in negative half-cycle, the operation principle of inverter 1 and above-described embodiment broadly similar, the situation that the symbol that is the circuit parameters such as electric current, voltage is positive half period with theoretical output voltage is contrary.
For example, in one embodiment of the invention, in the time that filter circuit 3 expects that the theoretical output voltage of output is negative, current limliting unit 43, can be specifically for the output voltage U when filter circuit 3 reality
cfor just and while being greater than described predefined voltage, power conversion circuit 2 is carried out to current limliting.
Optionally, described predefined voltage can be 0 or positive direct-current busbar voltage, can certainly be that the present invention does not limit this according to determined other the magnitude of voltage of concrete circuit parameter.
Further, when the theoretical output voltage of filter circuit 3 expection output is during in negative half-cycle, remove unit 44, can also be used for the output voltage U when filter circuit 3 reality
cwhen negative, if the current i of filter inductance 32
labsolute value be less than predefined electric current absolute value as I
ref2, remove the current limliting to power conversion circuit 2.
Accordingly, the embodiment of the present invention also provides a kind of overcurrent protective device of inverter, the described overcurrent protective device for inverter can be the overcurrent protective device arranging in any inverter of previous embodiment, therefore can whether exceed according to the absolute value of the output voltage of filter circuit equally the absolute value of predefined voltage, be informed in advance the absolute value whether absolute value of described inductive current after certain hour can be greater than overcurrent protection reference current, and determine whether to carry out current limliting to power conversion circuit in advance, thereby its operation of current limliting to power conversion circuit is come into force in time, under the condition of not changing circuit element, effectively improve at lower cost the overcurrent protection to inverter, reduce the risk that inverter damages because of overcurrent.
Accordingly, as shown in Figure 6, the embodiment of the present invention also provides a kind of over-current protection method for inverter, comprising:
S11, the output voltage of the filter circuit of the described inverter of sampling;
Described filter circuit carries out low-pass filtering for the alternating current of the power conversion circuit output to described inverter, wherein, described power conversion circuit is for being converted into alternating current by direct current, described power conversion circuit is for being converted into alternating current by direct current, and the variation of the output voltage of described filter circuit is ahead of the variation of the inductive current of described filter circuit;
S12, compares the output voltage of the described filter circuit of sampling with predefined voltage;
S13, when the output voltage of described filter circuit and when described theoretical output voltage is reverse and the absolute value of the output voltage of described filter circuit is greater than the absolute value of described predefined voltage, carries out current limliting to described power conversion circuit.
Adopt after technique scheme; the over-current protection method of the inverter that the embodiment of the present invention provides; can the sample output voltage of filter circuit of described inverter; reverse at output voltage and the theoretical output voltage of filter circuit of determining described inverter; and when the absolute value of the output voltage of described filter circuit is greater than the absolute value of predefined voltage, described power conversion circuit is carried out to current limliting.Like this; because the variation of the output voltage of described filter circuit is ahead of the variation of inductive current; that is to say; if the output voltage of described filter circuit experiences larger variation within a period of time; can conclude after during this period of time; inductive current also can experience larger variation, makes its absolute value exceed the absolute value of overcurrent protection reference current.
Like this, compare by the sampling of the output voltage to described filter circuit and with predefined voltage, can know in advance whether the absolute value of described inductive current over time can be greater than the absolute value of overcurrent protection reference current, and in advance described power conversion circuit is carried out to current limliting, compensate described power conversion circuit has been carried out in current limliting operation because the current limliting that hardware time delay and software delay cause operates the hysteresis coming into force, thereby be greater than the absolute value of overcurrent protection reference current at the absolute value of inductive current before, current limliting operation to described power conversion circuit comes into force in time, under the condition of not changing circuit element, effectively improve at lower cost the overcurrent protection to inverter, reduce the risk that inverter damages because of overcurrent.
In step S11, the output voltage of the described inverter of sampling can be specially the voltage at the filter capacitor two ends of the filter circuit of the described inverter of sampling.Optionally, in one embodiment of the invention, step S12 specifically can comprise: when described theoretical output voltage is for just, and the output voltage of described filter circuit is when negative, and described power conversion circuit is carried out to current limliting, and wherein said predefined voltage is 0; Or when described theoretical output voltage is for negative, and the output voltage of described filter circuit is timing, and described power conversion circuit is carried out to current limliting, and wherein said predefined voltage is 0.
Optionally, in another embodiment of the present invention, step S12 specifically can comprise: when described theoretical output voltage is for just, described output voltage is negative and is less than while bearing DC bus-bar voltage, described power conversion circuit is carried out to current limliting, and wherein said predefined voltage is negative DC bus-bar voltage; Or when described theoretical output voltage is for negative, described output voltage, for just and while being greater than positive direct-current busbar voltage, carries out current limliting to described power conversion circuit, and wherein said predefined voltage is positive direct-current busbar voltage.
Further, after step S13, described power conversion circuit is carried out to current limliting after, described method also comprises:
When described power conversion circuit is during by current limliting, if the output voltage of described filter circuit and described theoretical output voltage are in the same way, and the absolute value of the inductive current of described filter circuit is less than the absolute value of predefined electric current, remove the current limliting to described power conversion circuit.
One of ordinary skill in the art will appreciate that: all or part of flow process that realizes said method embodiment can complete by the relevant hardware of computer program instructions, aforesaid program can be stored in a computer read/write memory medium, this program, in the time carrying out, is carried out the step that comprises said method embodiment; And aforesaid storage medium comprises: various media that can be program code stored such as ROM, RAM, magnetic disc or CDs.
The above; be only the specific embodiment of the present invention, but protection scope of the present invention is not limited to this, any be familiar with those skilled in the art the present invention disclose technical scope in; can expect easily changing or replacing, within all should being encompassed in protection scope of the present invention.Therefore, protection scope of the present invention should be as the criterion with the protection range of described claim.
Claims (14)
1. an inverter, comprise the power conversion circuit for direct current being converted into alternating current, it is characterized in that, also comprise filter circuit and overcurrent protective device, described filter circuit is connected with described power conversion circuit, and described overcurrent protective device is connected with described filter circuit with described power conversion circuit respectively;
Described filter circuit comprises filter capacitor and filter inductance, and for the alternating current of described power conversion circuit output is carried out to low-pass filtering, the variation of the output voltage of described filter circuit is ahead of the variation of the inductive current of described filter circuit;
Described overcurrent protective device comprises:
Voltage sample unit, for the output voltage of the described filter circuit of sampling;
Voltage comparison unit, for comparing the output voltage of described voltage sample unit sampling with predefined voltage;
Current limliting unit, reverse for working as the output voltage of described filter circuit and the theoretical output voltage of described filter circuit, and when the absolute value that described voltage comparison unit is determined the output voltage of described filter circuit is greater than the absolute value of described predefined voltage, described power conversion circuit is carried out to current limliting; Wherein, described theoretical output voltage is the theoretical value of the output voltage of the described filter circuit determined according to the parameter of filter capacitor and filter inductance in described filter circuit and input electrical signal.
2. inverter according to claim 1, is characterized in that, described predefined voltage is 0; Correspondingly, described current limliting unit, specifically for when described theoretical output voltage is for just, and the output voltage of described filter circuit is when bearing, and described power conversion circuit is carried out to current limliting; Or when described theoretical output voltage is for negative, and the output voltage of described filter circuit is timing, and described power conversion circuit is carried out to current limliting.
3. inverter according to claim 1, is characterized in that,
Described predefined voltage is negative DC bus-bar voltage, and described current limliting unit is specifically for when described theoretical output voltage is for just, and the output voltage of described filter circuit is for negative and be less than while bearing DC bus-bar voltage, and described power conversion circuit is carried out to current limliting;
Or described predefined voltage is positive direct-current busbar voltage, described current limliting unit is specifically for working as described theoretical output voltage for negative, and the output voltage of described filter circuit, for just and while being greater than positive direct-current busbar voltage, carries out current limliting to described power conversion circuit.
4. inverter according to claim 1; it is characterized in that; described overcurrent protective device also comprises releasing unit; for when described power conversion circuit is during by current limliting; if the theoretical output voltage of the output voltage of described filter circuit and described filter circuit in the same way; and when the absolute value of the inductive current of described filter circuit is less than the absolute value of predefined electric current, remove the current limliting to described power conversion circuit.
5. an overcurrent protective device for inverter, is characterized in that, comprising:
Voltage sample unit, for the output voltage of the filter circuit of the inverter of sampling, wherein,
Described filter circuit comprises filter capacitor and filter inductance, alternating current for the power conversion circuit output to described inverter carries out low-pass filtering, described power conversion circuit is for being converted into alternating current by direct current, and the variation of the output voltage of described filter circuit is ahead of the variation of the inductive current of described filter circuit;
Voltage comparison unit, for comparing the output voltage of described voltage sample unit sampling with predefined voltage;
Current limliting unit, reverse for working as the output voltage of described filter circuit and the theoretical output voltage of described filter circuit, and when the absolute value that described voltage comparison unit is determined the output voltage of described filter circuit is greater than the absolute value of described predefined voltage, described power conversion circuit is carried out to current limliting; Wherein, described theoretical output voltage is the theoretical value of the output voltage of the described filter circuit determined according to the parameter of filter capacitor and filter inductance in described filter circuit and input electrical signal.
6. overcurrent protective device according to claim 5, is characterized in that, described voltage comparison unit is 0 for predefined voltage relatively; Described current limliting unit, specifically for when described theoretical output voltage is for just, and the output voltage of described filter circuit is when bearing, and described power conversion circuit is carried out to current limliting; Or when described theoretical output voltage is for negative, and the output voltage of described filter circuit is timing, and described power conversion circuit is carried out to current limliting.
7. overcurrent protective device according to claim 5, is characterized in that,
Described voltage comparison unit is negative DC bus-bar voltage for predefined voltage relatively, described current limliting unit is specifically for when described theoretical output voltage is for just, and the output voltage of described filter circuit is negative and is less than while bearing DC bus-bar voltage, described power conversion circuit is carried out to current limliting;
Or, described voltage comparison unit is positive direct-current busbar voltage for predefined voltage relatively, described current limliting unit is specifically for working as described theoretical output voltage for negative, and the output voltage of described filter circuit, for just and while being greater than positive direct-current busbar voltage, carries out current limliting to described power conversion circuit.
8. overcurrent protective device according to claim 5; it is characterized in that; described overcurrent protective device also comprises releasing unit; for when described power conversion circuit is during by current limliting; if the output voltage of described filter circuit and described theoretical output voltage are in the same way; and when the absolute value of the inductive current of described filter circuit is less than the absolute value of predefined electric current, remove the current limliting to described power conversion circuit.
9. an over-current protection method for inverter, is characterized in that, comprising:
The output voltage of the filter circuit of sampling inverter, described filter circuit carries out low-pass filtering for the alternating current of the power conversion circuit output to described inverter, described power conversion circuit is for being converted into alternating current by direct current, and the variation of the output voltage of described filter circuit is ahead of the variation of the inductive current of described filter circuit;
The output voltage of the described filter circuit of sampling is compared with predefined voltage;
When the output voltage of described filter circuit and when the theoretical output voltage of described filter circuit is reverse and the absolute value of the output voltage of described filter circuit is greater than the absolute value of described predefined voltage, described power conversion circuit is carried out to current limliting; Wherein, described theoretical output voltage is the theoretical value of the output voltage of the described filter circuit determined according to the parameter of filter capacitor and filter inductance in described filter circuit and input electrical signal.
10. method according to claim 9, is characterized in that, the output voltage of the filter circuit of the described inverter of described sampling, specifically comprises: the voltage at the filter capacitor two ends of the filter circuit of the described inverter of sampling.
11. methods according to claim 10, is characterized in that, described predefined voltage is 0;
When the absolute value of the output voltage of the reverse and described filter circuit of the theoretical output voltage of the described output voltage when described filter circuit and described filter circuit is greater than the absolute value of described predefined voltage, described power conversion circuit is carried out to current limliting, specifically comprises:
When described theoretical output voltage is for just, and the output voltage of described filter circuit is when negative, and described power conversion circuit is carried out to current limliting; Or when described theoretical output voltage is for negative, and the output voltage of described filter circuit is timing, and described power conversion circuit is carried out to current limliting.
12. methods according to claim 10, is characterized in that, described predefined voltage is negative DC bus-bar voltage;
When the absolute value of the output voltage of the reverse and described filter circuit of the described output voltage when described filter circuit and described theoretical output voltage is greater than the absolute value of described predefined voltage, described power conversion circuit is carried out to current limliting, specifically comprises:
When described theoretical output voltage is for just, described output voltage, for negative and while being less than negative DC bus-bar voltage, carries out current limliting to described power conversion circuit.
13. methods according to claim 10, is characterized in that, described predefined voltage is positive direct-current busbar voltage;
When the absolute value of the output voltage of the reverse and described filter circuit of the theoretical output voltage of the described output voltage when described filter circuit and described filter circuit is greater than the absolute value of described predefined voltage, described power conversion circuit is carried out to current limliting, specifically comprises:
When described theoretical output voltage is for negative, described output voltage, for just and while being greater than positive direct-current busbar voltage, carries out current limliting to described power conversion circuit.
14. according to the method described in claim 9-13 any one, it is characterized in that, described power conversion circuit is carried out to current limliting after, described method also comprises:
If the output voltage of described filter circuit and described theoretical output voltage are in the same way, and the absolute value of the inductive current of described filter circuit is less than the absolute value of predefined electric current, the current limliting of releasing to described power conversion circuit.
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| CN103078485B (en) * | 2013-01-28 | 2015-08-19 | 华为技术有限公司 | A kind of Inverter Over-current-limiting Methods guard method and device |
| CN103474964B (en) * | 2013-09-17 | 2015-08-26 | 北京科技大学 | A kind of prevent inversion from overturning intelligent overcurrent protective device and control method |
| CN104104062B (en) * | 2014-07-25 | 2018-01-16 | 华为技术有限公司 | The Over Current Protection System and method of inverter circuit |
| CN104767368B (en) * | 2015-03-27 | 2017-06-13 | 深圳市航天新源科技有限公司 | A kind of highly reliable three-level inverter circuit Current limited Control method |
| CN107147094B (en) * | 2017-04-27 | 2021-05-07 | 华为技术有限公司 | Current-limiting protection circuit and protection method |
| CN112670958A (en) * | 2019-10-16 | 2021-04-16 | 株洲中车时代电气股份有限公司 | Overcurrent protection method and device for output current of inverter |
| CN113595372A (en) * | 2021-07-28 | 2021-11-02 | 阳光电源股份有限公司 | Protection circuit, application device thereof and circuit protection method |
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